1
|
Kim J, Roh J, Park M, Lee C. Recent Advances and Challenges of Colloidal Quantum Dot Light-Emitting Diodes for Display Applications. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2212220. [PMID: 36853911 DOI: 10.1002/adma.202212220] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 02/21/2023] [Indexed: 06/18/2023]
Abstract
Colloidal quantum dots (QDs) exhibit tremendous potential in display technologies owing to their unique optical properties, such as size-tunable emission wavelength, narrow spectral linewidth, and near-unity photoluminescence quantum yield. Significant efforts in academia and industry have achieved dramatic improvements in the performance of quantum dot light-emitting diodes (QLEDs) over the past decade, primarily owing to the development of high-quality QDs and optimized device architectures. Moreover, sophisticated patterning processes have also been developed for QDs, which is an essential technique for their commercialization. As a result of these achievements, some QD-based display technologies, such as QD enhancement films and QD-organic light-emitting diodes, have been successfully commercialized, confirming the superiority of QDs in display technologies. However, despite these developments, the commercialization of QLEDs is yet to reach a threshold, requiring a leap forward in addressing challenges and related problems. Thus, representative research trends, progress, and challenges of QLEDs in the categories of material synthesis, device engineering, and fabrication method to specify the current status and development direction are reviewed. Furthermore, brief insights into the factors to be considered when conducting research on single-device QLEDs are provided to realize active matrix displays. This review guides the way toward the commercialization of QLEDs.
Collapse
Affiliation(s)
- Jaehoon Kim
- Department of Energy and Mineral Resources Engineering, Dong-A University, Busan, 49315, Republic of Korea
| | - Jeongkyun Roh
- Department of Electrical Engineering, Pusan National University, Busan, 46241, Republic of Korea
| | - Myoungjin Park
- Display Research Center, Samsung Display Co., Yongin-si, Gyeonggi-do, 17113, Republic of Korea
| | - Changhee Lee
- Display Research Center, Samsung Display Co., Yongin-si, Gyeonggi-do, 17113, Republic of Korea
| |
Collapse
|
2
|
Chen Z, Li H, Yuan C, Gao P, Su Q, Chen S. Color Revolution: Prospects and Challenges of Quantum-Dot Light-Emitting Diode Display Technologies. SMALL METHODS 2024; 8:e2300359. [PMID: 37357153 DOI: 10.1002/smtd.202300359] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2023] [Revised: 05/15/2023] [Indexed: 06/27/2023]
Abstract
Light-emitting diodes (LEDs) based on colloidal quantum-dots (QDs) such as CdSe, InP, and ZnSeTe feature a unique advantage of narrow emission linewidth of ≈20 nm, which can produce highly accurate colors, making them a highly promising technology for the realization of displays with Rec. 2020 color gamut. With the rapid development in the past decades, the performances of red and green QLEDs have been remarkably improved, and their efficiency and lifetime can almost meet industrial requirements. However, the industrialization of QLED displays still faces many challenges; for example, (1) the device mechanisms including the charge injection/transport/leakage, exciton quenching, and device degradation are still unclear, which fundamentally limit QLED performance improvement; (2) the blue performances including the efficiency, chromaticity, and stability are relatively low, which are still far from the requirements of practical applications; (3) the color patterning processes including the ink-jet printing, transfer printing, and photolithography are still immature, which restrict the manufacturing of high resolution full-color QLED displays. Here, the recent advancements attempting to address the above challenges of QLED displays are specifically reviewed. After a brief overview of QLED development history, device structure/principle, and performances, the main focus is to investigate the recent discoveries on device mechanisms with an emphasis on device degradation. Then recent progress is introduced in blue QLEDs and color patterning. Finally, the opportunities, challenges, solutions, and future research directions of QLED displays are summarized.
Collapse
Affiliation(s)
- Zinan Chen
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen, 518055, P. R. China
| | - Haotao Li
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen, 518055, P. R. China
| | - Cuixia Yuan
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen, 518055, P. R. China
| | - Peili Gao
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen, 518055, P. R. China
| | - Qiang Su
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen, 518055, P. R. China
| | - Shuming Chen
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen, 518055, P. R. China
| |
Collapse
|
3
|
Azadinia M, Chun P, Lyu Q, Cotella G, Aziz H. Differences in Electron and Hole Injection and Auger Recombination between Red, Green, and Blue CdSe-Based Quantum Dot Light Emitting Devices. ACS NANO 2024; 18:1485-1495. [PMID: 38175971 DOI: 10.1021/acsnano.3c07999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2024]
Abstract
Despite the significant progress that has been made in recent years in improving the performance of quantum dot light-emitting devices (QLEDs), the effect of charge imbalance and excess carriers on excitons in red (R) vs green (G) vs blue (B) QLEDs has not been compared or systematically studied. In this work we study the effect of changing the electron (e)/hole (h) supply ratio in the QDs emissive layer (EML) in CdSe-based R-, G-, and B-QLEDs with inverted structure in order to identify the type of excess carriers and investigate their effect on the electroluminescence performance of QLEDs of each color. Results show that in R-QLEDs, the e/h ratio in the EML is >1, whereas in G- and B-QLEDs, the e/h ratio is <1 with charge balance conditions being significantly worse in the case of B-QLEDs. Transient photoluminescence (PL) and steady state PL measurements show that, compared to electrons, holes lead to a stronger Auger quenching effect. Transient electroluminescence (TrEL) results indicate that Auger quenching leads to a gradual decline in the EL performance of the QLEDs after a few microseconds, with a stronger effect observed for positive charging versus negative charging. The results provide insights into the differences in the efficiency behavior of R-, G-, and B-QLEDs and uncover the role of excess holes and poor charge balance in the lower efficiency and EL stability of B-QLEDs.
Collapse
Affiliation(s)
- Mohsen Azadinia
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| | - Peter Chun
- Ottawa IC Laboratory, Huawei Canada, 19 Allstate Parkway, Markham, Ontario L3R 5B4, Canada
| | - Quan Lyu
- Ipswich Research Centre, Huawei Technologies Research & Development (U.K.) Ltd., Phoenix House (B55), Adastral Park, Ipswich, IP5 3RE, U.K
| | - Giovanni Cotella
- Ipswich Research Centre, Huawei Technologies Research & Development (U.K.) Ltd., Phoenix House (B55), Adastral Park, Ipswich, IP5 3RE, U.K
| | - Hany Aziz
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| |
Collapse
|
4
|
Liu Y, Yan M, Shu J, He H, Wang Z, Qin Z, Wang Y, Zhang Y. Enhanced Performance and High Resistance to Efficiency Degradation of Blue Quantum-Dot Light-Emitting Diodes Using the Lewis Base Blended Hole-Transporting Layers. ACS APPLIED MATERIALS & INTERFACES 2024; 16:1251-1258. [PMID: 38129975 DOI: 10.1021/acsami.3c17141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
The distinctive characteristics of blue quantum dots (QDs) such as their deep valence band and large bandgap give rise to an elevated hole injection barrier between the hole transport layers (HTLs) and the QD active layer. This results in an imbalance of carrier transport and injection across the device, leading to a degrading performance in QD light-emitting diodes (QLEDs). In this paper, high-efficiency and low-efficiency degradation blue CdSe/CdS/ZnS QLEDs were fabricated by using the Lewis base, 1,2-bis(diphenylphosphino)ethane (DPPE), blended with poly(9-vinylcarbazole) (PVK) (DPPE:PVK) as HTLs. The device performance of blue QLEDs can be finely adjusted by manipulating the blending ratio between DPPE and PVK. When 4 wt % DPPE was blended with PVK (4 wt % DPPE:PVK) as the HTL, the device achieved its optimal performance. Compared to the device with neat PVK as the HTL, the turn-on voltage of blue QLEDs with the 4 wt % DPPE:PVK HTL is reduced from 3.21 to 2.9 V. The maximum current efficiency (CE) and external quantum efficiency (EQE) of blue QLEDs increase from 2.92 cd A-1 and 5.89% in neat PVK to 5.75 cd A-1 and 11.75% for the 4 wt % DPPE:PVK HTL. Furthermore, the QLEDs incorporating DPPE:PVK HTLs exhibited exceptional resistance to efficiency degradation (EQE = 8.83%@L = 12,000 cd m-2 for 4 wt % DPPE:PVK as the HTL and EQE = 2.80%@L = 12,000 cd m-2 for neat PVK as the HTL). A more in-depth analysis reveals that enhanced device performance results from the chelating and bridging effect of the bidentate ligand Lewis base DPPE. These effects strengthen the binding of free metal ions in the blue QDs, reduce the charge barriers, enhance the contact between the HTLs and the QD active layer, and ultimately improve hole injection.
Collapse
Affiliation(s)
- Yuyu Liu
- School of Semiconductor Science and Technology, South China Normal University, Guangzhou 510631, P. R. China
| | - Minming Yan
- School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, P. R. China
| | - Jia Shu
- School of Semiconductor Science and Technology, South China Normal University, Guangzhou 510631, P. R. China
| | - Hongwei He
- School of Semiconductor Science and Technology, South China Normal University, Guangzhou 510631, P. R. China
| | - Zi Wang
- School of Semiconductor Science and Technology, South China Normal University, Guangzhou 510631, P. R. China
| | - Ziyu Qin
- School of Semiconductor Science and Technology, South China Normal University, Guangzhou 510631, P. R. China
| | - Yunwei Wang
- School of Semiconductor Science and Technology, South China Normal University, Guangzhou 510631, P. R. China
| | - Yong Zhang
- School of Semiconductor Science and Technology, South China Normal University, Guangzhou 510631, P. R. China
- Guangdong Engineering Technology Research Center of Low Carbon and Advanced Energy Materials, Guangzhou 510631, P. R. China
| |
Collapse
|
5
|
Zhao F, Duan HW, Li SN, Pan JL, Shen WS, Li SM, Zhang Q, Wang YK, Liao LS. Iodotrimethylsilane as a Reactive Ligand for Surface Etching and Passivation of Perovskite Nanocrystals toward Efficient Pure-red to Deep-red LEDs. Angew Chem Int Ed Engl 2023; 62:e202311089. [PMID: 37770413 DOI: 10.1002/anie.202311089] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 09/27/2023] [Accepted: 09/28/2023] [Indexed: 09/30/2023]
Abstract
Resurfacing perovskite nanocrystals (NCs) with tight-binding and conductive ligands to resolve the dynamic ligands-surface interaction is the fundamental issue for their applications in perovskite light-emitting diodes (PeLEDs). Although various types of surface ligands have been proposed, these ligands either exhibit weak Lewis acid/base interactions or need high polar solvents for dissolution and passivation, resulting in a compromise in the efficiency and stability of PeLEDs. Herein, we report a chemically reactive agent (Iodotrimethylsilane, TMIS) to address the trade-off among conductivity, solubility and passivation using all-inorganic CsPbI3 NCs. The liquid TMIS ensures good solubility in non-polar solvents and reacts with oleate ligands and produces in situ HI for surface etching and passivation, enabling strong-binding ligands on the NCs surface. We report, as a result, red PeLEDs with an external quantum efficiency (EQE) of ≈23 %, which is 11.2-fold higher than the control, and is among the highest CsPbI3 PeLEDs. We further demonstrate the universality of this ligand strategy in the pure bromide system (CsPbBr3 ), and report EQE of ≈20 % at 640, 652, and 664 nm. This represents the first demonstration of a chemically reactive ligand strategy that applies to different systems and works effectively in red PeLEDs spanning emission from pure-red to deep-red.
Collapse
Affiliation(s)
- Feng Zhao
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, 215123, Suzhou, China
| | - Hong-Wei Duan
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, 215123, Suzhou, China
| | - Sheng-Nan Li
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, 215123, Suzhou, China
| | - Jia-Lin Pan
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, 215123, Suzhou, China
| | - Wan-Shan Shen
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, 215123, Suzhou, China
| | - Sheng-Ming Li
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, 215123, Suzhou, China
| | - Qiao Zhang
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, 215123, Suzhou, China
| | - Ya-Kun Wang
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, 215123, Suzhou, China
| | - Liang-Sheng Liao
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, 215123, Suzhou, China
- Macao Institute of Materials Science and Engineering, Macau University of Science and Technology, Taipa, 999078, Macau SAR, China
| |
Collapse
|
6
|
Samaeifar F, Azadinia M, Aziz H. Lifetime enhancement in QDLEDs via an electron-blocking hole transport layer. Sci Rep 2023; 13:18698. [PMID: 37907631 PMCID: PMC10618160 DOI: 10.1038/s41598-023-45907-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Accepted: 10/25/2023] [Indexed: 11/02/2023] Open
Abstract
This study investigates the impact of an engineered hole transport layer (HTL) on the stability of electroluminescent quantum dot light-emitting devices (QDLEDs). The 9-Phenyl-3,6-bis(9-phenyl-9Hcarbazol-3-yl)-9H-carbazole (Tris-PCz) HTL, which possesses a shallower lowest unoccupied molecular orbital (LUMO) energy level compared to the widely used 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP) HTL, is employed to confine electron overflow toward the HTL. Utilizing the Tris-PCz HTL results in a 20× improvement in the electroluminescence half-life (LT50) of QDLEDs compared with conventional QDLEDs using the CBP HTL. Electric and optoelectronic analyses reveal that the migration of excess electrons toward the HTL is impeded by the up-shifted LUMO level of Tris-PCz, contributing to prolonged operational device stability. Furthermore, the augmented electric field at the QD/Tris-PCz interface, due to accumulated electrons, expedites hole injection rates, leading to better charge injection balance and the confinement of the exciton recombination zone within the QD and thus the device stability enhancement. This study highlights the significant influence of the HTL on QDLED stability and represents one of the longest LT50 for a QDLED based on the conventional core/shell QD structure.
Collapse
Affiliation(s)
- Fatemeh Samaeifar
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1, Canada.
| | - Mohsen Azadinia
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1, Canada
| | - Hany Aziz
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1, Canada
| |
Collapse
|
7
|
Chen J, Ghorbani A, Chung DS, Azadinia M, Davidson-Hall T, Chun P, Lyu Q, Cotella G, Song D, Xu Z, Aziz H. Influence of Encapsulation on the Efficiency and Positive Aging Behavior in Blue Quantum Dot Light-Emitting Devices. ACS APPLIED MATERIALS & INTERFACES 2023. [PMID: 37421356 DOI: 10.1021/acsami.3c05272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/10/2023]
Abstract
Encapsulating blue quantum dot light-emitting devices (QLEDs) using an ultraviolet curable resin is known to lead to a significant increase in their efficiency. Some of this efficiency increase occurs immediately, whereas some of it proceeds over a period of time, typically over several tens of hours following the encapsulation, a behavior commonly referred to as positive aging. The root causes of this positive aging, especially in blue QLEDs, remain not well understood. Here, it is revealed that contrary to the expectation, the significant improvement in device efficiency during positive aging arises primarily from an improvement in electron injection across the QD/ZnMgO interface and not due to the inhibition of interface exciton quenching as is widely believed. The underlying changes are investigated by XPS measurements. Results show that the enhancement in device performance arises primarily from the reduction in O-related defects in both the QDs and ZnMgO at the QD/ZnMgO interface. After 51.5 h, the blue QLEDs reach the optimal performance, exhibiting an EQEmax of 12.58%, which is more than sevenfold higher than that in the control device without encapsulation. This work provides design principles for realizing high efficiency in blue QLEDs with oxide electron-transporting layers (ETLs) and provides a new understanding of the mechanisms underlying positive aging in these devices and thus offers a new starting point for both fundamental investigations and practical applications.
Collapse
Affiliation(s)
- Junfei Chen
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
- Key Laboratory of Luminescence and Optical Information, Beijing Jiaotong University, Ministry of Education, Beijing 100044, China
- Institute of Optoelectronics Technology, Beijing Jiaotong University, Beijing 100044, China
| | - Atefeh Ghorbani
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| | - Dong Seob Chung
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| | - Mohsen Azadinia
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| | - Tyler Davidson-Hall
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| | - Peter Chun
- Ottawa IC Laboratory, Huawei Canada, 19 Allstate Parkway, Markham, Ontario L3R 5B4, Canada
| | - Quan Lyu
- Ipswich Research Centre, Huawei Technologies Research & Development (UK) Ltd., Phoenix House, (B55), Adastral Park, Ipswich IP5 3RE, U.K
| | - Giovanni Cotella
- Ipswich Research Centre, Huawei Technologies Research & Development (UK) Ltd., Phoenix House, (B55), Adastral Park, Ipswich IP5 3RE, U.K
| | - Dandan Song
- Key Laboratory of Luminescence and Optical Information, Beijing Jiaotong University, Ministry of Education, Beijing 100044, China
- Institute of Optoelectronics Technology, Beijing Jiaotong University, Beijing 100044, China
| | - Zheng Xu
- Key Laboratory of Luminescence and Optical Information, Beijing Jiaotong University, Ministry of Education, Beijing 100044, China
- Institute of Optoelectronics Technology, Beijing Jiaotong University, Beijing 100044, China
| | - Hany Aziz
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| |
Collapse
|
8
|
Cai F, Tu Y, Tian D, Fang Y, Hou B, Ishaq M, Jiang X, Li M, Wang S, Du Z. Defect passivation and electron band energy regulation of a ZnO electron transport layer through synergetic bifunctional surface engineering for efficient quantum dot light-emitting diodes. NANOSCALE 2023. [PMID: 37314171 DOI: 10.1039/d3nr01194a] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Zinc oxide nanoparticles (ZnO NPs) have been actively pursued as the most effective electron transport layer for quantum-dot light-emitting diodes (QLEDs) in light of their unique optical and electronic properties and low-temperature processing. However, the high electron mobility and smooth energy level alignment at QDs/ZnO/cathode interfaces cause electron over-injection, which aggravates non-radiative Auger recombination. Meanwhile, the abundant defects hydroxyl group (-OH) and oxygen vacancies (OV) in ZnO NPs act as trap states inducing exciton quenching, which synergistically reduces the effective radiation recombination for degrading the device performance. Here, we develop a bifunctional surface engineering strategy to synthesize ZnO NPs with low defect density and high environmental stability by using ethylenediaminetetraacetic acid dipotassium salt (EDTAK) as an additive. The additive effectively passivates surface defects in ZnO NPs and induces chemical doping simultaneously. Bifunctional engineering alleviates electron excess injection by elevating the conduction band level of ZnO to promote charge balance. As a result, state-of-the-art blue QLEDs with an EQE of 16.31% and a T50@100 cd m-2 of 1685 h are achieved, providing a novel and effective strategy to fabricate blue QLEDs with high efficiency and a long operating lifetime.
Collapse
Affiliation(s)
- Fensha Cai
- Key Lab for Special Functional Materials of Ministry of Education, National & Local Joint Engineering Research Center for High-efficiency Display and Lighting Technology, School of Materials Science and Engineering, and Collaborative Innovation Center of Nano Functional Materials and Applications, Henan University, Kaifeng 475004, China.
| | - Yufei Tu
- School of Electronics Information and, Intelligent Manufacturing, Sias University, Xinzheng, China
| | - Dadi Tian
- Key Lab for Special Functional Materials of Ministry of Education, National & Local Joint Engineering Research Center for High-efficiency Display and Lighting Technology, School of Materials Science and Engineering, and Collaborative Innovation Center of Nano Functional Materials and Applications, Henan University, Kaifeng 475004, China.
| | - Yan Fang
- Key Lab for Special Functional Materials of Ministry of Education, National & Local Joint Engineering Research Center for High-efficiency Display and Lighting Technology, School of Materials Science and Engineering, and Collaborative Innovation Center of Nano Functional Materials and Applications, Henan University, Kaifeng 475004, China.
| | - Bo Hou
- School of Physics and Astronomy, Cardiff University, Cardiff, Wales, CF24 3AA, UK
| | - Muhammad Ishaq
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Xiaohong Jiang
- Key Lab for Special Functional Materials of Ministry of Education, National & Local Joint Engineering Research Center for High-efficiency Display and Lighting Technology, School of Materials Science and Engineering, and Collaborative Innovation Center of Nano Functional Materials and Applications, Henan University, Kaifeng 475004, China.
| | - Meng Li
- Key Lab for Special Functional Materials of Ministry of Education, National & Local Joint Engineering Research Center for High-efficiency Display and Lighting Technology, School of Materials Science and Engineering, and Collaborative Innovation Center of Nano Functional Materials and Applications, Henan University, Kaifeng 475004, China.
| | - Shujie Wang
- Key Lab for Special Functional Materials of Ministry of Education, National & Local Joint Engineering Research Center for High-efficiency Display and Lighting Technology, School of Materials Science and Engineering, and Collaborative Innovation Center of Nano Functional Materials and Applications, Henan University, Kaifeng 475004, China.
| | - Zuliang Du
- Key Lab for Special Functional Materials of Ministry of Education, National & Local Joint Engineering Research Center for High-efficiency Display and Lighting Technology, School of Materials Science and Engineering, and Collaborative Innovation Center of Nano Functional Materials and Applications, Henan University, Kaifeng 475004, China.
| |
Collapse
|
9
|
Yu R, Yin F, Pu C, Zhou D, Ji W. On the electroluminescence overshoot of quantum-dot light-emitting diodes. OPTICS LETTERS 2023; 48:3059-3062. [PMID: 37262280 DOI: 10.1364/ol.492710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 05/15/2023] [Indexed: 06/03/2023]
Abstract
The charge-carrier dynamics is a fundamental question in quantum-dot light-emitting diodes (QLEDs), determining the electroluminescence (EL) properties of the devices. By means of a hole-confined QLED design, the distribution and storage/residing of the charge carriers in the devices are deciphered by the transient electroluminescence (TrEL) spectroscopic technology. It is demonstrated that the holes stored in the quantum dots (QDs) are responsible for the EL overshoot during the rising edge of the TrEL response. Moreover, the earlier electroluminescence turn-on behavior is observed due to the holes residing in the hole-confined structure. The hole storage effect should be attributed to the ultralow hole mobility of QD films and large barrier for hole escape from the cores of the QDs. Our findings provide a deep understanding of the charge transport and storage at the most critical interface between QDs and hole-transport layer, where the excitons are formed.
Collapse
|
10
|
Chen D, Ma L, Chen Y, Zhou X, Xing S, Deng Y, Hao Y, Pu C, Kong X, Jin Y. Electrochemically Stable Ligands of ZnO Electron-Transporting Layers for Quantum-Dot Light-Emitting Diodes. NANO LETTERS 2023; 23:1061-1067. [PMID: 36662173 DOI: 10.1021/acs.nanolett.2c04670] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Thin films of ZnO nanocrystals are actively pursued as electron-transporting layers (ETLs) in quantum-dot light-emitting diodes (QLEDs). However, the developments of ZnO-based ETLs are highly engineering oriented and the design of ZnO-based ETLs remains empirical. Here, we identified a previously overlooked efficiency-loss channel associated with the ZnO-based ETLs: i.e., interfacial exciton quenching induced by surface-bound ethanol. Accordingly, we developed a general surface-treatment procedure to replace the redox-active surface-bound ethanol with electrochemically inert alkali carboxylates. Characterization results show that the surface treatment procedure does not change other key properties of the ETLs, such as the conductance and work function. Our single-variable experimental design unambiguously demonstrates that improving the electrochemical stabilities of the ZnO ETLs leads to QLEDs with a higher efficiency and longer operational lifetime. Our work provides a crucial guideline to design ZnO-based ETLs for optoelectronic devices.
Collapse
Affiliation(s)
- Desui Chen
- Zhejiang Key Laboratory for Excited-State Materials, State Key Laboratory of Silicon Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, People's Republic of China
| | - Luying Ma
- Zhejiang Key Laboratory for Excited-State Materials, State Key Laboratory of Silicon Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, People's Republic of China
| | - Yunhua Chen
- Zhejiang Key Laboratory for Excited-State Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, People's Republic of China
| | - Xiaoqi Zhou
- Zhejiang Key Laboratory for Excited-State Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, People's Republic of China
| | - Shiyu Xing
- Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Hangzhou 310027, People's Republic of China
| | - Yunzhou Deng
- Zhejiang Key Laboratory for Excited-State Materials, State Key Laboratory of Silicon Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, People's Republic of China
| | - Yanlei Hao
- Zhejiang Key Laboratory for Excited-State Materials, State Key Laboratory of Silicon Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, People's Republic of China
| | - Chaodan Pu
- School of Physical Science and Technology, Shanghai Tech University, Shanghai 201210, People's Republic of China
| | - Xueqian Kong
- Zhejiang Key Laboratory for Excited-State Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, People's Republic of China
| | - Yizheng Jin
- Zhejiang Key Laboratory for Excited-State Materials, State Key Laboratory of Silicon Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, People's Republic of China
| |
Collapse
|
11
|
Luo X, Zhou X, Wei S. Ionic liquid-assisted green solution approach for high-performance full-color emission quantum dot films of Ag-doped ZnxCd1-xS. INORG CHEM COMMUN 2023. [DOI: 10.1016/j.inoche.2023.110421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
|
12
|
Hu Y, Cao S, Qiu P, Yu M, Wei H. All-Inorganic Perovskite Quantum Dot-Based Blue Light-Emitting Diodes: Recent Advances and Strategies. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:4372. [PMID: 36558224 PMCID: PMC9781770 DOI: 10.3390/nano12244372] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 12/02/2022] [Accepted: 12/06/2022] [Indexed: 06/17/2023]
Abstract
Light-emitting diodes (LEDs) based on all-inorganic lead halide perovskite quantum dots (PQDs) have undergone rapid development especially in the past five years, and external quantum efficiencies (EQEs) of the corresponding green- and red-emitting devices have exceeded 23%. However, the blue-emitting devices are facing greater challenges than their counterparts, and their poor luminous efficiency has hindered the display application of PQD-based LEDs (PeQLEDs). This review focuses on the key challenges of blue-emitting PeQLEDs including low EQEs, short operating lifetime, and spectral instability, and discusses the essential mechanism by referring to the latest research. We then systematically summarize the development of preparation methods of blue emission PQDs, as well as the current strategies on alleviating the poor device performance involved in composition engineering, ligand engineering, surface/interface engineering, and device structural engineering. Ultimately, suggestions and outlooks are proposed around the major challenges and future research direction of blue PeQLEDs.
Collapse
Affiliation(s)
- Yuyu Hu
- Beijing Advanced Innovation Center for Materials Genome Engineering, Beijing Key Laboratory for Magneto–Photoelectrical Composite and Interface Science, School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China
| | - Shijie Cao
- Beijing Advanced Innovation Center for Materials Genome Engineering, Beijing Key Laboratory for Magneto–Photoelectrical Composite and Interface Science, School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China
| | - Peng Qiu
- Beijing Advanced Innovation Center for Materials Genome Engineering, Beijing Key Laboratory for Magneto–Photoelectrical Composite and Interface Science, School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China
| | - Meina Yu
- Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, China
| | - Huiyun Wei
- Beijing Advanced Innovation Center for Materials Genome Engineering, Beijing Key Laboratory for Magneto–Photoelectrical Composite and Interface Science, School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China
- Engineering Research Center of Clinical Functional Materials and Diagnosis & Treatment Devices of Zhejiang Province, Wenzhou Institute, Wenzhou Institute of Biomaterials & Engineering, University of Chinese Academy of Sciences, Wenzhou 325027, China
| |
Collapse
|
13
|
Wang LX, Tang CG, Tan ZS, Phua HY, Chen J, Lei W, Png RQ, Chua LL, Ho PKH. Double-type-I charge-injection heterostructure for quantum-dot light-emitting diodes. MATERIALS HORIZONS 2022; 9:2147-2159. [PMID: 35616351 DOI: 10.1039/d1mh00859e] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Enforcing balanced electron-hole injection into the emitter layer of quantum-dot light-emitting diodes (QLEDs) remains key to maximizing the quantum efficiency over a wide current density range. This was previously thought not possible for quantum dot (QD) emitters because of their very deep energy bands. Here, we show using Mesolight® blue-emitting CdZnSeS/ZnS QDs as a model that its valence levels are in fact considerably shallower than the corresponding band maximum of the bulk semiconductor, which makes the ideal double-type-I injection/confinement heterostructure accessible using a variety of polymer organic semiconductors as transport and injection layers. We demonstrate flat external quantum efficiency characteristics that indicate near perfect recombination within the QD layer over several decades of current density from the onset of device turn-on of about 10 μA cm-2, for both normal and inverted QLED architectures. We also demonstrate that these organic semiconductors do not chemically degrade the QDs, unlike the usual ZnMgO nanoparticles. However, these more efficient injection heterostructures expose a new vulnerability of the QDs to in device electrochemical degradation. The work here opens a clear path towards next-generation ultra-high-performance, all-solution-processed QLEDs.
Collapse
Affiliation(s)
- Li-Xi Wang
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550, Singapore.
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing, People's Republic of China
| | - Cindy G Tang
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550, Singapore.
| | - Zhao-Siu Tan
- Department of Chemistry, National University of Singapore, Lower Kent Ridge Road, S117552, Singapore.
| | - Hao-Yu Phua
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550, Singapore.
| | - Jing Chen
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing, People's Republic of China
| | - Wei Lei
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing, People's Republic of China
| | - Rui-Qi Png
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550, Singapore.
| | - Lay-Lay Chua
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550, Singapore.
- Department of Chemistry, National University of Singapore, Lower Kent Ridge Road, S117552, Singapore.
| | - Peter K H Ho
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550, Singapore.
| |
Collapse
|
14
|
Fang Y, Bai P, Li J, Xiao B, Wang Y, Wang Y. Highly Efficient Red Quantum Dot Light-Emitting Diodes by Balancing Charge Injection and Transport. ACS APPLIED MATERIALS & INTERFACES 2022; 14:21263-21269. [PMID: 35486114 DOI: 10.1021/acsami.2c04369] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Quantum dot light-emitting diodes (QLEDs) have promising commercial value and application prospects in the fields of displays and lighting. However, a charge-transfer imbalance always exists in the devices. In this work, the high-efficiency red QLEDs were obtained via employing the mixtures of poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(4,4'-(N-(4-butylphenyl) (TFB) and 4,4'-bis(carbazole-9-yl)-1,1'-biphenyl (CBP) as hole-transport layers (HTLs) by solution processing. The optimized mixing concentration of CBP is 20 wt %. The corresponding red QLED exhibited a maximum luminance of 963 433 cd m-2, a maximum current efficiency of 38.7 cd A-1, an external quantum efficiency of 30.0%, a central wavelength of 628 nm with a narrow full width at half-maximum (fwhm) of 24 nm, and a 5-fold T50 lifetime enhancement at an extremely high luminance of 200 000 cd m-2. The characteristics of carrier-only devices with QD emissive layers (QD EMLs) and impedance characteristics of QLEDs demonstrate that these advances are chiefly ascribed to the more balanced charge transport and efficient hole-electron recombination in EML. We anticipate that our results could offer a low-cost and simple solution-processed method for preparing high-performance QLEDs.
Collapse
Affiliation(s)
- Yunfeng Fang
- School of Materials Science and Engineering, Changchun University of Science and Technology, Changchun 130022, People's Republic of China
| | - Penglong Bai
- School of Materials Science and Engineering, Changchun University of Science and Technology, Changchun 130022, People's Republic of China
| | - Jiayi Li
- School of Materials Science and Engineering, Changchun University of Science and Technology, Changchun 130022, People's Republic of China
| | - Binbin Xiao
- School of Materials Science and Engineering, Changchun University of Science and Technology, Changchun 130022, People's Republic of China
| | - Yiqing Wang
- School of Materials Science and Engineering, Changchun University of Science and Technology, Changchun 130022, People's Republic of China
| | - Yanping Wang
- School of Materials Science and Engineering, Changchun University of Science and Technology, Changchun 130022, People's Republic of China
| |
Collapse
|
15
|
Wang R, Wang T, Kang Z, Zhang H, Yu R, Ji W. Efficient flexible quantum-dot light-emitting diodes with unipolar charge injection. OPTICS EXPRESS 2022; 30:15747-15756. [PMID: 35473288 DOI: 10.1364/oe.456449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Accepted: 04/11/2022] [Indexed: 06/14/2023]
Abstract
The exfoliation between the electrode film and the adjacent functional layer is still a big challenge for the flexible light emitting diodes, especially for the devices dependent on the direct charge injection from the electrodes. To address this issue, we design a flexible quantum-dot light-emitting diodes (QLEDs) with a charge-generation layer (CGL) on the bottom electrode as the electron supplier. The CGL consisting of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/ZnO can provide sufficient electron injection into the QDs, enabling a balanced charge injection. As a result, the CGL-based QLED exhibits a peak external quantum efficiency 18.6%, over 25% enhancement in comparison with the device with ZnO as the electron transport layer. Moreover, the residual electrons in the ZnO can be pulled back to the PEDOT:PSS/ZnO interface by the storage holes in the CGL, which are released and accelerates the electron injection during the next driving voltage pulse, hence improving the electroluminescence response speed of the QLEDs.
Collapse
|
16
|
Kim SK, Lee SH, Yoon SY, Jo DY, Kim HM, Kim Y, Park SM, Kim YH, Yang H. Localized surface plasmon-enhanced blue electroluminescent device based on ZnSeTe quantum dots and AuAg nanoparticles. Inorg Chem Front 2022. [DOI: 10.1039/d2qi00448h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Localized surface plasmon resonance-enhanced Cd-free blue electroluminescent devices integrated with ZnSeTe quantum dots and AuAg alloy nanoparticles were demonstrated.
Collapse
Affiliation(s)
- Sun-Kyo Kim
- Department of Materials Science and Engineering, Hongik University, Seoul 04066, Korea
| | - Sun-Hyoung Lee
- Department of Materials Science and Engineering, Hongik University, Seoul 04066, Korea
| | - Suk-Young Yoon
- Department of Materials Science and Engineering, Hongik University, Seoul 04066, Korea
| | - Dae-Yeon Jo
- Department of Materials Science and Engineering, Hongik University, Seoul 04066, Korea
| | - Hyun-Min Kim
- Department of Materials Science and Engineering, Hongik University, Seoul 04066, Korea
| | - Yuri Kim
- Department of Materials Science and Engineering, Hongik University, Seoul 04066, Korea
| | - Seong Min Park
- Department of Materials Science and Engineering, Hongik University, Seoul 04066, Korea
| | - Yang-Hee Kim
- Department of Materials Science and Engineering, Hongik University, Seoul 04066, Korea
| | - Heesun Yang
- Department of Materials Science and Engineering, Hongik University, Seoul 04066, Korea
| |
Collapse
|
17
|
Wu Q, Gong X, Zhao D, Zhao YB, Cao F, Wang H, Wang S, Zhang J, Quintero-Bermudez R, Sargent EH, Yang X. Efficient Tandem Quantum-Dot LEDs Enabled by An Inorganic Semiconductor-Metal-Dielectric Interconnecting Layer Stack. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2108150. [PMID: 34761462 DOI: 10.1002/adma.202108150] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Indexed: 06/13/2023]
Abstract
Light-emitting diodes (LEDs) in a tandem configuration offer a strategy to realize high-performance, multicolor devices. Until now, though, the efficiency of tandem colloidal quantum dot LEDs (QLEDs) has been limited due to unpassivated interfaces and solvent damage originating from the materials processing requirements of interconnecting layers (ICLs). Here an ICL is reported consisting of a semiconductor-metal-dielectric stack that provides facile fabrication, materials stability, and good optoelectronic coupling. It is investigated experimentally how the ICL enables charge balance, suppresses current leakage, and prevents solvent damage to the underlying layers. As a result record efficiencies are reported for double-junction tandem QLEDs, whose emission wavelengths cover from blue to red light; i.e., external quantum efficiencies (EQEs) of 40% (average 37+/-2%) for red, 49% (average 45+/-2%) for yellow, 50% (average 46+/-2%) for green, and 24% (average 21+/-2%) for blue are achieved.
Collapse
Affiliation(s)
- Qianqian Wu
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, 149 Yanchang Road, Shanghai, 200072, China
| | - Xiwen Gong
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, Ontario, M5S 1A4, Canada
| | - Dewei Zhao
- Institute of Solar Energy Materials and Devices, College of Materials Science and Engineering, Sichuan University, No. 24 South Section 1, Yihuan Road, Chengdu, 610065, China
| | - Yong-Biao Zhao
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, Ontario, M5S 1A4, Canada
| | - Fan Cao
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, 149 Yanchang Road, Shanghai, 200072, China
| | - Haoran Wang
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, 149 Yanchang Road, Shanghai, 200072, China
| | - Sheng Wang
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, 149 Yanchang Road, Shanghai, 200072, China
| | - Jianhua Zhang
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, 149 Yanchang Road, Shanghai, 200072, China
| | - Rafael Quintero-Bermudez
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, Ontario, M5S 1A4, Canada
| | - Edward H Sargent
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, Ontario, M5S 1A4, Canada
| | - Xuyong Yang
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, 149 Yanchang Road, Shanghai, 200072, China
| |
Collapse
|
18
|
Dong JY, Ng KW, Song YM, Li JL, Kong YC, Wang MW, Xu JC, Li L, Chen S, Tang ZK, Wang SP. Observation and Suppression of Stacking Interface States in Sandwich-Structured Quantum Dot Light-Emitting Diodes. ACS APPLIED MATERIALS & INTERFACES 2021; 13:56630-56637. [PMID: 34794311 DOI: 10.1021/acsami.1c13052] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Interfacial quality of functional layers plays an important role in the carrier transport of sandwich-structured devices. Although the suppression of interface states is crucial to the overall device performance, our understanding on their formation and annihilation mechanism via direct characterization is still quite limited. Here, we present a thorough study on the interface states present in the electron transport layer (ETL) of blue quantum dot (QD) light-emitting diodes (QLEDs). A ZnO/ZnMgO bilayer ETL is adopted to enhance the electron injection into blue QDs. By probing the ETL band structure with photoelectron spectroscopy, we discover that substantial band bending exists at the ZnO/ZnMgO interface, elucidating the presence of a high density of interface states which hinder electron transport. By inserting a ZnO@ZMO interlayer composed of mixed ZnO and ZnMgO nanoparticles, the band bending and thus the interface states are observed to reduce significantly. We attribute this to the hybrid surface properties of ZnO@ZMO, which can annihilate the surface states of both the ZnO and ZnMgO layers. The introduction of a bridging layer has led to ∼40% enhancement in the power efficiency of blue QLEDs and noticeable performance boosts in green and red QLEDs. The findings here demonstrate a direct observation of interface states via detailed band structure studies and outline a potential pathway for eliminating these states for better performances in sandwich-structured devices.
Collapse
Affiliation(s)
- Jia-Yi Dong
- Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao, SAR 999078, China
| | - Kar Wei Ng
- Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao, SAR 999078, China
| | - Yin-Man Song
- Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao, SAR 999078, China
| | - Jie-Lei Li
- Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao, SAR 999078, China
| | - You-Chao Kong
- Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao, SAR 999078, China
| | - Meng-Wei Wang
- Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao, SAR 999078, China
| | - Jin-Cheng Xu
- Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao, SAR 999078, China
| | - Lin Li
- Key Laboratory for Photonic and Electronic Bandgap Materials, Ministry of Education, School of Physics & Electron Engineering, Harbin Normal University, Harbin 150025, China
| | - Shi Chen
- Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao, SAR 999078, China
| | - Zi-Kang Tang
- Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao, SAR 999078, China
| | - Shuang-Peng Wang
- Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao, SAR 999078, China
| |
Collapse
|
19
|
Liu RJ, Dong JY, Wang MW, Yuan QL, Ji WY, Xu JC, Liu WW, Su SC, Ng KW, Tang ZK, Wang SP. Efficiency Improvement of Quantum Dot Light-Emitting Diodes via Thermal Damage Suppression with HATCN. ACS APPLIED MATERIALS & INTERFACES 2021; 13:49058-49065. [PMID: 34633792 DOI: 10.1021/acsami.1c16034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
With many advantages including superior color saturation and efficiency, quantum dot light-emitting diodes (QLEDs) are considered a promising candidate for the next-generation displays. Emission uniformity over the entire device area is a critical factor to the overall performance and reliability of QLEDs. In this work, we performed a thorough study on the origin of dark spots commonly observed in operating QLEDs and developed a strategy to eliminate these defects. Using advanced cross section fabrication and imaging techniques, we discovered the occurrence of voids in the organic hole transport layer and directly correlated them to the observed emission nonuniformity. Further investigations revealed that these voids are thermal damages induced during the subsequent thermal deposition of other functional layers and can act as leakage paths in the device. By inserting a thermo-tolerant 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HATCN) interlayer with an optimized thickness, the thermally induced dark spots can be completely suppressed, leading to a current efficiency increase by 18%. We further demonstrated that such a thermal passivation strategy can work universally for various types of organic layers with low thermal stability. Our findings here provide important guidance in enhancing the performances and reliability of QLEDs and also other sandwich-structured devices via the passivation of heat-sensitive layers.
Collapse
Affiliation(s)
- Ren-Jun Liu
- Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, Macao SAR 999078, China
| | - Jia-Yi Dong
- Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, Macao SAR 999078, China
| | - Meng-Wei Wang
- Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, Macao SAR 999078, China
| | - Qi-Lin Yuan
- Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, Macao SAR 999078, China
- Key Lab of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, 2699 Qianjin Street, Changchun 130012, China
| | - Wen-Yu Ji
- Key Lab of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, 2699 Qianjin Street, Changchun 130012, China
| | - Jin-Cheng Xu
- Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, Macao SAR 999078, China
| | - Wei-Wei Liu
- Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, Macao SAR 999078, China
- Department of Physics and Electronic Engineering, Yancheng Teachers University, Yancheng 224002, China
| | - Shi-Chen Su
- Institute of Semiconductor Science and Technology, South China Normal University, Guangzhou 510631, China
- SCNU Qingyuan Institute of Science and Technology Innovation Co., Ltd., Qingyuan 511517, China
| | - Kar-Wei Ng
- Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, Macao SAR 999078, China
| | - Zi-Kang Tang
- Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, Macao SAR 999078, China
| | - Shuang-Peng Wang
- Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, Macao SAR 999078, China
| |
Collapse
|
20
|
Chung DS, Davidson-Hall T, Yu H, Samaeifar F, Chun P, Lyu Q, Cotella G, Aziz H. Significant enhancement in quantum-dot light emitting device stability via a ZnO:polyethylenimine mixture in the electron transport layer. NANOSCALE ADVANCES 2021; 3:5900-5907. [PMID: 36132666 PMCID: PMC9419077 DOI: 10.1039/d1na00561h] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 08/17/2021] [Indexed: 05/22/2023]
Abstract
The effect of adding polyethylenimine (PEI) into the ZnO electron transport layer (ETL) of inverted quantum dot (QD) light emitting devices (QDLEDs) to form a blended ZnO:PEI ETL instead of using it in a separate layer in a bilayer ZnO/PEI ETL is investigated. Results show that while both ZnO/PEI bilayer ETL and ZnO:PEI blended ETL can improve device efficiency by more than 50% compared to QDLEDs with only ZnO, the ZnO:PEI ETL significantly improves device stability, leading to more than 10 times longer device lifetime. Investigations using devices with marking luminescent layers, electron-only devices and delayed electroluminescence measurements show that the ZnO:PEI ETL leads to a deeper penetration of electrons into the hole transport layer (HTL) of the QDLEDs. The results suggest that the stability enhancement may be due to a consequent reduction in hole accumulation at the QD/HTL interface. The findings show that ZnO:PEI ETLs can be used for enhancing both the efficiency and stability of QDLEDs. They also provide new insights into the importance of managing charge distribution in the charge transport layers for realizing high stability QDLEDs and new approaches to achieve that.
Collapse
Affiliation(s)
- Dong Seob Chung
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo 200 University Avenue West Waterloo Ontario N2L 3G1 Canada
| | - Tyler Davidson-Hall
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo 200 University Avenue West Waterloo Ontario N2L 3G1 Canada
| | - Hyeonghwa Yu
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo 200 University Avenue West Waterloo Ontario N2L 3G1 Canada
| | - Fatemeh Samaeifar
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo 200 University Avenue West Waterloo Ontario N2L 3G1 Canada
| | - Peter Chun
- Ottawa IC Laboratory, Huawei Canada 19 Allstate Parkway Markham ON L3R 5B4 Canada
| | - Quan Lyu
- Ipswich Research Centre, Huawei Technologies Research & Development (UK) Ltd. Phoenix House (B55), Adastral Park Ipswich IP5 3RE UK
| | - Giovanni Cotella
- Ipswich Research Centre, Huawei Technologies Research & Development (UK) Ltd. Phoenix House (B55), Adastral Park Ipswich IP5 3RE UK
| | - Hany Aziz
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo 200 University Avenue West Waterloo Ontario N2L 3G1 Canada
| |
Collapse
|
21
|
Wang T, Chen Z, Zhang H, Ji W. Color-Tunable Alternating-Current Quantum Dot Light-Emitting Devices. ACS APPLIED MATERIALS & INTERFACES 2021; 13:45815-45821. [PMID: 34519471 DOI: 10.1021/acsami.1c11529] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
To date, it remains a central challenge to achieve electroluminescence in both positive and negative half cycles of alternating-current (AC) voltage for a light-emitting device. Herein, we successfully demonstrated a novel structure to construct a real AC quantum dot light-emitting device (QLED) with two charge generation layers (CGLs) consisting of the poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/ZnO nanoparticle bilayer structure. Besides the conventional driving way with power input from a pair of opposite electrodes, this AC QLED can also work in the manner of in-planar-electrode driving mode, achieving simultaneous electroluminescence of each pixel. By employing a bilayer emissive layer composed of red and green quantum dots, the emission color of the AC QLED can be tuned by both the polarity and amplitude of the driving voltage. Leveraging the excellent electron injection and negligible voltage consumption from the CGLs, this QLED can be turned on at a record low voltage of 5.6 V. We believe that this AC QLED can provide a platform for the realization of simple and smart plug-and-play QLED-based display and lighting systems.
Collapse
Affiliation(s)
- Ting Wang
- Key Lab of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun 130012, China
| | - Zhijie Chen
- Key Lab of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun 130012, China
| | - Huimin Zhang
- Key Lab of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun 130012, China
| | - Wenyu Ji
- Key Lab of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun 130012, China
| |
Collapse
|
22
|
Zvaigzne M, Alexandrov A, Tkach A, Lypenko D, Nabiev I, Samokhvalov P. Optimizing the PMMA Electron-Blocking Layer of Quantum Dot Light-Emitting Diodes. NANOMATERIALS (BASEL, SWITZERLAND) 2021; 11:2014. [PMID: 34443846 PMCID: PMC8401809 DOI: 10.3390/nano11082014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 08/03/2021] [Accepted: 08/04/2021] [Indexed: 02/04/2023]
Abstract
Quantum dots (QDs) are promising candidates for producing bright, color-pure, cost-efficient, and long-lasting QD-based light-emitting diodes (QDLEDs). However, one of the significant problems in achieving high efficiency of QDLEDs is the imbalance between the rates of charge-carrier injection into the emissive QD layer and their transport through the device components. Here we investigated the effect of the parameters of the deposition of a poly (methyl methacrylate) (PMMA) electron-blocking layer (EBL), such as PMMA solution concentration, on the characteristics of EBL-enhanced QDLEDs. A series of devices was fabricated with the PMMA layer formed from acetone solutions with concentrations ranging from 0.05 to 1.2 mg/mL. The addition of the PMMA layer allowed for an increase of the maximum luminance of QDLED by a factor of four compared to the control device without EBL, that is, to 18,671 cd/m2, with the current efficiency increased by an order of magnitude and the turn-on voltage decreased by ~1 V. At the same time, we have demonstrated that each particular QDLED characteristic has a maximum at a specific PMMA layer thickness; therefore, variation of the EBL deposition conditions could serve as an additional parameter space when other QDLED optimization approaches are being developed or implied in future solid-state lighting and display devices.
Collapse
Affiliation(s)
- Mariya Zvaigzne
- Laboratory of Nano-Bioengineering, Institute of Engineering Physics for Biomedicine, National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 31 Kashirskoe Highway, 115409 Moscow, Russia; (A.T.); (I.N.)
| | - Alexei Alexandrov
- Laboratory of Electronic and Photonic Processes in Polymeric Nanomaterials, A.N. Frumkin Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences, 31, bld.4, Leninsky Prospect, 119071 Moscow, Russia; (A.A.); (D.L.)
| | - Anastasia Tkach
- Laboratory of Nano-Bioengineering, Institute of Engineering Physics for Biomedicine, National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 31 Kashirskoe Highway, 115409 Moscow, Russia; (A.T.); (I.N.)
| | - Dmitriy Lypenko
- Laboratory of Electronic and Photonic Processes in Polymeric Nanomaterials, A.N. Frumkin Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences, 31, bld.4, Leninsky Prospect, 119071 Moscow, Russia; (A.A.); (D.L.)
| | - Igor Nabiev
- Laboratory of Nano-Bioengineering, Institute of Engineering Physics for Biomedicine, National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 31 Kashirskoe Highway, 115409 Moscow, Russia; (A.T.); (I.N.)
- Laboratory of Immunopathology, I.M. Sechenov First Moscow State Medical University, 8-2 Trubetskaya Str., 119991 Moscow, Russia
- Laboratoire de Recherche en Nanosciences, Université de Reims Champagne-Ardenne, 51 rue Cognacq Jay, 51100 Reims, France
| | - Pavel Samokhvalov
- Laboratory of Nano-Bioengineering, Institute of Engineering Physics for Biomedicine, National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 31 Kashirskoe Highway, 115409 Moscow, Russia; (A.T.); (I.N.)
| |
Collapse
|
23
|
Chen WS, Yang SH, Tseng WC, Chen WWS, Lu YC. Utilization of Nanoporous Nickel Oxide as the Hole Injection Layer for Quantum Dot Light-Emitting Diodes. ACS OMEGA 2021; 6:13447-13455. [PMID: 34056492 PMCID: PMC8158834 DOI: 10.1021/acsomega.1c01618] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 04/29/2021] [Indexed: 06/10/2023]
Abstract
Nickel oxide (NiOx) has been extensively investigated as the hole injection layer (HIL) for many optoelectronic devices because of its excellent hole mobility, high environmental stability, and low-cost fabrication. In this research, a NiOx thin film and nanoporous layers (NPLs) have been utilized as the HIL for the fabrication of quantum dot light-emitting diodes (QLEDs). The obtained NiOx NPLs have spongelike nanostructures that possess a larger surface area to enhance carrier injection and to lower the turn-on voltage as compared with the NiOx thin film. The energy levels of NiOx were slightly downshifted by incorporating the nanoporous structure. The amount of Ni2O3 species is higher than that of NiO in the NiOx NPL, confirming its good hole transport ability. The best QLED was achieved with a 30 nm thick NiOx NPL, exhibiting a maximum brightness of 68 646 cd m-2, a current efficiency of 7.60 cd A-1, and a low turn-on voltage of 3.4 V. More balanced carrier transport from the NiOx NPL and ZnO NPs/polyethylenimine ethoxylated (PEIE) is responsible for the improved device performance.
Collapse
Affiliation(s)
- Wei-Sheng Chen
- Institute
of Lighting and Energy Photonics, College of Photonics, National Chiao Tung University, No. 301, Gaofa 3rd Road, Guiren District, Tainan 71150, Taiwan, ROC
| | - Sheng-Hsiung Yang
- Institute
of Lighting and Energy Photonics, College of Photonics, National Chiao Tung University, No. 301, Gaofa 3rd Road, Guiren District, Tainan 71150, Taiwan, ROC
| | - Wei-Cheng Tseng
- Opulence
Optronics Co., Ltd., 3F, No. 1, Zhanye 1st Road, East District, Hsinchu 30091, Taiwan, ROC
| | - Wilson Wei-Sheng Chen
- Opulence
Optronics Co., Ltd., 3F, No. 1, Zhanye 1st Road, East District, Hsinchu 30091, Taiwan, ROC
| | - Yuan-Chang Lu
- Opulence
Optronics Co., Ltd., 3F, No. 1, Zhanye 1st Road, East District, Hsinchu 30091, Taiwan, ROC
| |
Collapse
|
24
|
Wu Q, Cao F, Wang H, Kou J, Zhang Z, Yang X. Promoted Hole Transport Capability by Improving Lateral Current Spreading for High-Efficiency Quantum Dot Light-Emitting Diodes. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2020; 7:2001760. [PMID: 33304749 PMCID: PMC7709982 DOI: 10.1002/advs.202001760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 08/28/2020] [Indexed: 06/12/2023]
Abstract
Carrier imbalance resulting from stronger electron injection from ZnO into quantum-dot (QD) emissive layer than hole injection is one critical issue that constrains the performance of QDs-based light-emitting diodes (QLEDs). This study reports highly efficient inverted QLEDs enabled by periodic insertion of MoO3 into (4,4'-bis(N-carbazolyl)-1,1'-biphenyl) (CBP) hole transport layer (HTL). The periodic ultrathin MoO3/CBP-stacked HTL results in improved lateral current spreading for the QLEDs, which significantly relieves the crowding of holes and thus enhances hole transport capability across the CBP in QLEDs. Comprehensive analysis on the photoelectric properties of devices shows that the optimal thickness for MoO3 interlayer inserted in CBP is only ≈1 nm. The resulting devices with periodic two insertion layers of MoO3 into CBP exhibit better performance compared with the CBP-only ones, such that the peak current efficiency is 88.7 cd A-1 corresponding to the external quantum efficiency of 20.6%. Furthermore, the resulting QLEDs show an operational lifetime almost 2.5 times longer compared to CBP-only devices.
Collapse
Affiliation(s)
- Qianqian Wu
- Key Laboratory of Advanced Display and System Applications of Ministry of EducationShanghai University149 Yanchang RoadShanghai200072China
| | - Fan Cao
- Key Laboratory of Advanced Display and System Applications of Ministry of EducationShanghai University149 Yanchang RoadShanghai200072China
| | - Haoran Wang
- Key Laboratory of Advanced Display and System Applications of Ministry of EducationShanghai University149 Yanchang RoadShanghai200072China
| | - Jianquan Kou
- State Key Laboratory of Reliability and Intelligence of Electrical EquipmentHebei University of Technology5340 Xiping Road, Beichen DistrictTianjin300401China
| | - Zi‐Hui Zhang
- State Key Laboratory of Reliability and Intelligence of Electrical EquipmentHebei University of Technology5340 Xiping Road, Beichen DistrictTianjin300401China
| | - Xuyong Yang
- Key Laboratory of Advanced Display and System Applications of Ministry of EducationShanghai University149 Yanchang RoadShanghai200072China
| |
Collapse
|
25
|
Cho H, Park S, Shin H, Kim M, Jang H, Park J, Yang JH, Han CW, Baek JH, Jung YS, Jeon DY. Highly Efficient Deep Blue Cd-Free Quantum Dot Light-Emitting Diodes by a p-Type Doped Emissive Layer. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2020; 16:e2002109. [PMID: 32930494 DOI: 10.1002/smll.202002109] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 07/13/2020] [Indexed: 06/11/2023]
Abstract
Environmentally friendly ZnSe/ZnS core/shell quantum dots (QDs) as an alternative blue emission material to Cd-based QDs have shown great potential for use in next-generation displays. However, it remains still challenging to realize a high-efficiency quantum dot light-emitting diode (QLED) based on ZnSe/ZnS QDs due to their insufficient electrical characteristics, such as excessively high electron mobility (compared to the hole mobility) and the deep-lying valence band. In this work, the effects of QDs doped with hole transport materials (hybrid QDs) on the electrical characteristics of a QLED are investigated. These hybrid QDs show a p-type doping effect, which leads to a change in the density of the carriers. Specifically, the hybrid QDs can balance electrons and holes by suppressing the overflow of electrons and improving injection of holes, respectively. These electrical characteristics help to improve device performance. In detail, an external quantum efficiency (EQE) of 6.88% is achieved with the hybrid QDs. This is increased by 180% compared to a device with pure ZnSe/ZnS QDs (EQE of 2.46%). This record is the highest among deep-blue Cd-free QLED devices. These findings provide the importance of p-type doping effect in QD layers and guidance for the study of the electrical properties of QDs.
Collapse
Affiliation(s)
- Hyunjin Cho
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Sunjoong Park
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Hongjoo Shin
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Moohyun Kim
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Hanhwi Jang
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Jaehyun Park
- LG Display R&D Center, LG Sciencepark, 30, Magokjungang 10-ro, Gangseo-gu, Seoul, 07796, Republic of Korea
| | - Joong Hwan Yang
- LG Display R&D Center, LG Sciencepark, 30, Magokjungang 10-ro, Gangseo-gu, Seoul, 07796, Republic of Korea
| | - Chang Wook Han
- LG Display R&D Center, LG Sciencepark, 30, Magokjungang 10-ro, Gangseo-gu, Seoul, 07796, Republic of Korea
| | - Ji Ho Baek
- LG Display R&D Center, LG Sciencepark, 30, Magokjungang 10-ro, Gangseo-gu, Seoul, 07796, Republic of Korea
| | - Yeon Sik Jung
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Duk Young Jeon
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| |
Collapse
|
26
|
Lee K, Yun J, Lee S, Song J, Kim Y, Kwak J, Kim GT. Understanding of the aging pattern in quantum dot light-emitting diodes using low-frequency noise. NANOSCALE 2020; 12:15888-15895. [PMID: 32697229 DOI: 10.1039/d0nr01885f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The negative and positive aging effects of quantum dot (QD) light-emitting diodes (QLEDs) have received considerable attention in recent years and various analysis methods have been discussed. Here, we introduce a new approach to understand the aging effect of QLEDs, which is to diagnose the behavior of carriers and traps at interfaces between each layer of the QLEDs and inside the layers themselves. In particular, low-frequency noise (LFN) measurement and the analysis of current in the QLEDs were introduced to investigate the trapping/de-trapping behaviors of carriers in the defect states in the devices. A flicker noise was observed before the carriers are injected into the QD emitting layer, while the exciton generation-recombination (G-R) noise and shot noise were observed when the electrons were injected. A correlated noise, which is the correlated model of the trapping/de-trapping of the carriers near and/or inside the QDs and the exciton recombination, was also observed above the turn-on voltage. In addition, when the devices were aged with a constant current source, rapid increases in the luminance and external quantum efficiency (EQE) were observed for up to 50 h. After 100 h of the current aging, however, the devices were negatively aged with the reduced EQE. The LFN analysis results imply that the aging phenomena mainly depend on the trapping/de-trapping of carriers. In addition to the LFN analysis, we also investigated the current density-voltage-luminance and capacitance-voltage characteristics of the devices to clarify the aging behaviors in QLEDs.
Collapse
Affiliation(s)
- Kookjin Lee
- School of Electrical Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea
| | | | | | | | | | | | | |
Collapse
|
27
|
Xu Q, Li X, Lin Q, Shen H, Wang H, Du Z. Improved Efficiency of All-Inorganic Quantum-Dot Light-Emitting Diodes via Interface Engineering. Front Chem 2020; 8:265. [PMID: 32391315 PMCID: PMC7191064 DOI: 10.3389/fchem.2020.00265] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Accepted: 03/18/2020] [Indexed: 11/13/2022] Open
Abstract
As the charge transport layer of quantum dot (QD) light-emitting diodes (QLEDs), metal oxides are expected to be more stable compared with organic materials. However, the efficiency of metal oxide-based all-inorganic QLEDs is still far behind that of organic–inorganic hybrid ones. The main reason is the strong interaction between metal oxide and QDs leading to the emission quenching of QDs. Here, we demonstrated nickel oxide (NiOx)-based all-inorganic QLEDs with a maximum current efficiency of 20.4 cd A−1 and external quantum efficiency (EQE) of 5.5%, which is among the most efficient all-inorganic QLEDs. The high efficiency is mainly attributed to the aluminum oxide (Al2O3) deposited at the NiOx/QDs interface to suppress the strong quenching effect of NiOx on the QD emission, together with the molybdenum oxide (MoOx) that reduced the leakage current and facilitated hole injection, more than 300% enhancement was achieved compared with the pristine NiOx-based QLEDs. Our study confirmed the effect of decorating the NiOx/QDs interface on the performance enhancement of the all-inorganic QLEDs.
Collapse
Affiliation(s)
- Qiulei Xu
- Key Lab for Special Functional Materials, Ministry of Education, National and Local Joint Engineering Research Center for High-Efficiency Display and Lighting Technology, Collaborative Innovation Center of Nano Functional Materials and Applications, School of Materials Science and Engineering, Henan University, Kaifeng, China
| | - Xinyu Li
- Key Lab for Special Functional Materials, Ministry of Education, National and Local Joint Engineering Research Center for High-Efficiency Display and Lighting Technology, Collaborative Innovation Center of Nano Functional Materials and Applications, School of Materials Science and Engineering, Henan University, Kaifeng, China
| | - Qingli Lin
- Key Lab for Special Functional Materials, Ministry of Education, National and Local Joint Engineering Research Center for High-Efficiency Display and Lighting Technology, Collaborative Innovation Center of Nano Functional Materials and Applications, School of Materials Science and Engineering, Henan University, Kaifeng, China
| | - Huaibin Shen
- Key Lab for Special Functional Materials, Ministry of Education, National and Local Joint Engineering Research Center for High-Efficiency Display and Lighting Technology, Collaborative Innovation Center of Nano Functional Materials and Applications, School of Materials Science and Engineering, Henan University, Kaifeng, China
| | - Hongzhe Wang
- Key Lab for Special Functional Materials, Ministry of Education, National and Local Joint Engineering Research Center for High-Efficiency Display and Lighting Technology, Collaborative Innovation Center of Nano Functional Materials and Applications, School of Materials Science and Engineering, Henan University, Kaifeng, China
| | - Zuliang Du
- Key Lab for Special Functional Materials, Ministry of Education, National and Local Joint Engineering Research Center for High-Efficiency Display and Lighting Technology, Collaborative Innovation Center of Nano Functional Materials and Applications, School of Materials Science and Engineering, Henan University, Kaifeng, China
| |
Collapse
|
28
|
Alexandrov A, Zvaigzne M, Lypenko D, Nabiev I, Samokhvalov P. Al-, Ga-, Mg-, or Li-doped zinc oxide nanoparticles as electron transport layers for quantum dot light-emitting diodes. Sci Rep 2020; 10:7496. [PMID: 32366882 PMCID: PMC7198560 DOI: 10.1038/s41598-020-64263-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Accepted: 04/14/2020] [Indexed: 11/09/2022] Open
Abstract
Colloidal quantum dots and other semiconductor nanocrystals are essential components of next-generation lighting and display devices. Due to their easily tunable and narrow emission band and near-unity fluorescence quantum yield, they allow cost-efficient fabrication of bright, pure-color and wide-gamut light emitting diodes (LEDs) and displays. A critical improvement in the quantum dot LED (QLED) technology was achieved when zinc oxide nanoparticles (NPs) were first introduced as an electron transport layer (ETL) material, which tremendously enhanced the device brightness and current efficiency due to the high mobility of electrons in ZnO and favorable alignment of its energy bands. During the next decade, the strategy of ZnO NP doping allowed the fabrication of QLEDs with a brightness of about 200 000 cd/m2 and current efficiency over 60 cd/A. On the other hand, the known ZnO doping approaches rely on a very fine tuning of the energy levels of the ZnO NP conduction band minimum; hence, selection of the appropriate dopant that would ensure the best device characteristics is often ambiguous. Here we address this problem via detailed comparison of QLEDs whose ETLs are formed by a set of ZnO NPs doped with Al, Ga, Mg, or Li. Although magnesium-doped ZnO NPs are the most common ETL material used in recently designed QLEDs, our experiments have shown that their aluminum-doped counterparts ensure better device performance in terms of brightness, current efficiency and turn-on voltage. These findings allow us to suggest ZnO NPs doped with Al as the best ETL material to be used in future QLEDs.
Collapse
Affiliation(s)
- Alexei Alexandrov
- Laboratory of Nano-Bioengineering, National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 115409, Moscow, Russian Federation
- Laboratory of Electronic and Photonic Processes in Polymeric Nanostructural Materials, A.N. Frumkin Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences, 119071, Moscow, Russian Federation
| | - Mariya Zvaigzne
- Laboratory of Nano-Bioengineering, National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 115409, Moscow, Russian Federation
| | - Dmitri Lypenko
- Laboratory of Nano-Bioengineering, National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 115409, Moscow, Russian Federation
- Laboratory of Electronic and Photonic Processes in Polymeric Nanostructural Materials, A.N. Frumkin Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences, 119071, Moscow, Russian Federation
| | - Igor Nabiev
- Laboratory of Nano-Bioengineering, National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 115409, Moscow, Russian Federation.
- Laboratoire de Recherche en Nanosciences, LRN-EA4682, Université de Reims Champagne-Ardenne, 51100, Reims, France.
- I.M. Sechenov First Moscow State Medical University, 119991, Moscow, Russian Federation.
| | - Pavel Samokhvalov
- Laboratory of Nano-Bioengineering, National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 115409, Moscow, Russian Federation.
| |
Collapse
|
29
|
Davidson-Hall T, Aziz H. Significant Enhancement in Quantum Dot Light-Emitting Device Stability via a Cascading Hole Transport Layer. ACS APPLIED MATERIALS & INTERFACES 2020; 12:16782-16791. [PMID: 32181638 DOI: 10.1021/acsami.9b23567] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
This work investigates the effect of the hole transport layer (HTL) on the stability of electroluminescent quantum dot light-emitting devices (QDLEDs). The electroluminescence half-life (LT50) of QDLEDs can be improved by 25× through the utilization of a cascading HTL (CHTL) structure with consecutive steps in the highest occupied molecular orbital energy level. Using this approach, a LT50 of 864,000 h (for an initial luminance of 100 cd m-2) is obtained for red QDLEDs using a conventional core/shell QD emitter. The CHTL primarily improves QDLED stability by shifting excessive hole accumulation away from the QD/HTL interface and toward the interlayer HTL/HTL interfaces. The wider electron-hole recombination zone in the CHTL for electrons that have leaked from the QD layer results in less HTL degradation at the QD/HTL interface. This work highlights the significant influence of the HTL on QDLED stability and represents the longest LT50 for a QDLED based on the conventional core/shell QD structure.
Collapse
Affiliation(s)
- Tyler Davidson-Hall
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| | - Hany Aziz
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| |
Collapse
|
30
|
Rhee S, Chang JH, Hahm D, Kim K, Jeong BG, Lee HJ, Lim J, Char K, Lee C, Bae WK. "Positive Incentive" Approach To Enhance the Operational Stability of Quantum Dot-Based Light-Emitting Diodes. ACS APPLIED MATERIALS & INTERFACES 2019; 11:40252-40259. [PMID: 31590488 DOI: 10.1021/acsami.9b13217] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Balanced charge injection promises high efficiency of quantum dot-based light-emitting diodes (QD-LEDs). The most widely used approach to realize charge injection balance impedes the injection rate of the dominant charge carrier with energetic barriers. However, these approaches often accompany unwanted outcomes (e.g., the increase in operation voltage) that sacrifice the operational stability of devices. Herein, a "positive incentive" approach is proposed to enhance the efficiency and the operational stability of QD-LEDs. Specifically, the supply of hole, an inferior carrier than its counterpart, is facilitated by adopting a thin fullerene (C60) interlayer at the interface between the hole injection layer (MoOX) and hole transport layer (4,4'-bis(9-carbazolyl)-1,1'-biphenyl). The C60 interlayer boosts the hole current by eliminating the universal energy barrier, lowers the operation voltage of QD-LEDs, and enhances the charge balance in the QD emissive layer within the working device. Consequently, QD-LEDs benefitting from the adoption of the C60 interlayer exhibit significantly enhanced device efficiency and operation stability. Grounded on the quantitative assessment of the charge injection imbalance within the QD emissive layer, the impact of electrical parameters of QD-LEDs on their optoelectronic performance and operational stability is also discussed.
Collapse
Affiliation(s)
| | | | | | | | - Byeong Guk Jeong
- SKKU Advanced Institute of Nanotechnology , Sungkyunkwan University , Suwon 16419 , Korea
| | | | - Jaehoon Lim
- Department of Chemical Engineering , Ajou University , Suwon 16499 , Korea
| | | | | | - Wan Ki Bae
- SKKU Advanced Institute of Nanotechnology , Sungkyunkwan University , Suwon 16419 , Korea
| |
Collapse
|
31
|
Lee CY, Naik Mude N, Lampande R, Eun KJ, Yeom JE, Choi HS, Sohn SH, Yoo JM, Kwon JH. Efficient Cadmium-Free Inverted Red Quantum Dot Light-Emitting Diodes. ACS APPLIED MATERIALS & INTERFACES 2019; 11:36917-36924. [PMID: 31529962 DOI: 10.1021/acsami.9b12514] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Here, we report an efficient inverted red indium phosphide (InP) comprising QD (InP/ZnSe/ZnS, core/shell structure) light-emitting diode (QLED) by modulating an interfacial contact between the electron transport layer and emissive InP-QDs and applying self-aging approach. The red InP-QLED with optimized interfacial contact exhibits a significant improvement in maximum external quantum efficiency and current efficiency from 4.42 to 10.2% and 4.70 to 10.8 cd/A, respectively, after 69 days of self-aging, which is an almost 2.3-fold improvement compared to the fresh device. The analysis indicates the consecutive reduction in electron injection and accumulation in the emissive QD due to changes in the conduction band minimum of ZnMgO (0.1 eV after 10 days of storage) through a downward vacuum-level shift according to the aging times. During the device aging periods, the oxygen vacancy of ZnMgO reduces, which leads to lower the conductivity of ZnMgO. As a result, charge balance of the device is improved with the suppression of exciton quenching at the interface of ZnMgO and InP-QD.
Collapse
Affiliation(s)
- Chae Young Lee
- Department of Information Display , Kyung Hee University , 26, Kyungheedae-ro , Dongdaemoon-gu, Seoul 02447 , Republic of Korea
| | - Nagarjuna Naik Mude
- Department of Information Display , Kyung Hee University , 26, Kyungheedae-ro , Dongdaemoon-gu, Seoul 02447 , Republic of Korea
| | - Raju Lampande
- Department of Information Display , Kyung Hee University , 26, Kyungheedae-ro , Dongdaemoon-gu, Seoul 02447 , Republic of Korea
| | - Kwan Ju Eun
- Department of Information Display , Kyung Hee University , 26, Kyungheedae-ro , Dongdaemoon-gu, Seoul 02447 , Republic of Korea
| | - Ji Eun Yeom
- Department of Information Display , Kyung Hee University , 26, Kyungheedae-ro , Dongdaemoon-gu, Seoul 02447 , Republic of Korea
| | - Hyung Sik Choi
- Research and Development Team, Visual Display , Samsung Electronics Co., Ltd , 129, Samsung-ro , Yeongtong-gu, Suwon 16677 , Republic of Korea
| | - Sang Hyun Sohn
- Research and Development Team, Visual Display , Samsung Electronics Co., Ltd , 129, Samsung-ro , Yeongtong-gu, Suwon 16677 , Republic of Korea
| | - Jun Mo Yoo
- Research and Development Team, Visual Display , Samsung Electronics Co., Ltd , 129, Samsung-ro , Yeongtong-gu, Suwon 16677 , Republic of Korea
| | - Jang Hyuk Kwon
- Department of Information Display , Kyung Hee University , 26, Kyungheedae-ro , Dongdaemoon-gu, Seoul 02447 , Republic of Korea
| |
Collapse
|
32
|
Moon H, Lee C, Lee W, Kim J, Chae H. Stability of Quantum Dots, Quantum Dot Films, and Quantum Dot Light-Emitting Diodes for Display Applications. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1804294. [PMID: 30650209 DOI: 10.1002/adma.201804294] [Citation(s) in RCA: 171] [Impact Index Per Article: 34.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 10/10/2018] [Indexed: 05/06/2023]
Abstract
Quantum dots (QDs) are being highlighted in display applications for their excellent optical properties, including tunable bandgaps, narrow emission bandwidth, and high efficiency. However, issues with their stability must be overcome to achieve the next level of development. QDs are utilized in display applications for their photoluminescence (PL) and electroluminescence. The PL characteristics of QDs are applied to display or lighting applications in the form of color-conversion QD films, and the electroluminescence of QDs is utilized in quantum dot light-emitting diodes (QLEDs). Studies on the stability of QDs and QD devices in display applications are reviewed herein. QDs can be degraded by oxygen, water, thermal heating, and UV exposure. Various approaches have been developed to protect QDs from degradation by controlling the composition of their shells and ligands. Phosphorescent QDs have been protected by bulky ligands, physical incorporation in polymer matrices, and covalent bonding with polymer matrices. The stability of electroluminescent QLEDs can be enhanced by using inorganic charge transport layers and by improving charge balance. As understanding of the degradation mechanisms of QDs increases and more stable QDs and display devices are developed, QDs are expected to play critical roles in advanced display applications.
Collapse
Affiliation(s)
- Hyungsuk Moon
- School of Chemical Engineering, Sungkyunkwan University (SKKU), Seoburo 2066, Jangan-gu, Suwon, Gyeonggi-do, 16419, Republic of Korea
| | - Changmin Lee
- School of Chemical Engineering, Sungkyunkwan University (SKKU), Seoburo 2066, Jangan-gu, Suwon, Gyeonggi-do, 16419, Republic of Korea
| | - Woosuk Lee
- School of Chemical Engineering, Sungkyunkwan University (SKKU), Seoburo 2066, Jangan-gu, Suwon, Gyeonggi-do, 16419, Republic of Korea
| | - Jungwoo Kim
- School of Chemical Engineering, Sungkyunkwan University (SKKU), Seoburo 2066, Jangan-gu, Suwon, Gyeonggi-do, 16419, Republic of Korea
| | - Heeyeop Chae
- School of Chemical Engineering, Sungkyunkwan University (SKKU), Seoburo 2066, Jangan-gu, Suwon, Gyeonggi-do, 16419, Republic of Korea
- SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University (SKKU), Seoburo 2066, Jangan-gu, Suwon, Gyeonggi-do, 16419, Republic of Korea
| |
Collapse
|
33
|
Davidson-Hall T, Aziz H. The role of excitons within the hole transporting layer in quantum dot light emitting device degradation. NANOSCALE 2019; 11:8310-8318. [PMID: 30982837 DOI: 10.1039/c8nr09560d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
This work investigates the root causes of the limited stability of electroluminescent quantum dot light-emitting devices (QDLEDs). Studies using electrical measurements, continuous UV irradiation, and both steady-state and transient photoluminescence (PL) spectroscopy reveal that exciton-induced degradation of the hole transporting material (HTM) in QDLEDs plays a role in limiting their electroluminescence (EL) stability. The results indicate that there is a correlation between device EL stability and the susceptibility of the HTM to exciton-induced degradation. The presence of quenchers in the HTM layer can lead to a decrease in the luminescence quantum yield of QDs, suggesting that energy transfer between the QD and HTM films may play a role in this behavior. The results uncover a new degradation mechanism where excitons within the HTM limit the EL stability of QDLEDs.
Collapse
Affiliation(s)
- Tyler Davidson-Hall
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada.
| | | |
Collapse
|
34
|
Sun Y, Jiang Y, Sun XW, Zhang S, Chen S. Beyond OLED: Efficient Quantum Dot Light-Emitting Diodes for Display and Lighting Application. CHEM REC 2019; 19:1729-1752. [PMID: 30698895 DOI: 10.1002/tcr.201800191] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Indexed: 01/25/2023]
Abstract
The unique features of solution-processed quantum dots (QDs) including emission tunability in the visible range, high-quality saturated color and outstanding intrinsic stability in environment are highly desired in various application fields. Especially, for the preparation of wide color gamut displays, QDs with high photoluminescence quantum yield are deemed as the optimal fluorescent emitter that has been utilized in the backlight for liquid crystal display. Nevertheless, the commercialization of electrically driven self-emissive quantum dot light-emitting diode (QLED) display is the ultimate target due to its merits of high contrast, slim configuration and compatibility with flexible substrate. Through the great efforts devoted to material engineering and device configuration, astonishing progresses have been made in device performance, giving the QLED technology a great chance to compete with other counterparts for next-generation displays. In this review, we retrospect the development roadmap of QLED technology and introduce the essential principles in the QLED devices. Moreover, we discuss the key factors that affect the QLED efficiency and lifetime. Finally, the advances in device architectures and pixel patterning are also summarized.
Collapse
Affiliation(s)
- Yizhe Sun
- Institute of Microelectronics, Peking University, Beijing, P. R. China, 100871.,Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen, P. R. China, 518055
| | - Yibin Jiang
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen, P. R. China, 518055.,State Key Lab on Advanced Displays and Optoelectronics, The Hong Kong University of Science and Technology Clear Water Bay, Kowloon, Hong Kong
| | - Xiao Wei Sun
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen, P. R. China, 518055
| | - Shengdong Zhang
- Institute of Microelectronics, Peking University, Beijing, P. R. China, 100871
| | - Shuming Chen
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen, P. R. China, 518055
| |
Collapse
|
35
|
Jin H, Moon H, Lee W, Hwangbo H, Yong SH, Chung HK, Chae H. Charge balance control of quantum dot light emitting diodes with atomic layer deposited aluminum oxide interlayers. RSC Adv 2019; 9:11634-11640. [PMID: 35517031 PMCID: PMC9063432 DOI: 10.1039/c9ra00145j] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 04/03/2019] [Indexed: 12/01/2022] Open
Abstract
We developed a 1.0 nm thick aluminum oxide (Al2O3) interlayer as an electron blocking layer to reduce leakage current and suppress exciton quenching induced by charge imbalance in inverted quantum dot light emitting diodes (QLEDs). The Al2O3 interlayer was deposited by an atomic layer deposition (ALD) process that allows precise thickness control. The Al2O3 interlayer lowers the mobility of electrons and reduces Auger recombination which causes the degradation of device performance. A maximum current efficiency of 51.2 cd A−1 and an external quantum efficiency (EQE) of 12.2% were achieved in the inverted QLEDs with the Al2O3 interlayer. The Al2O3 interlayer increased device efficiency by 1.1 times, increased device lifetime by 6 times, and contributed to reducing efficiency roll-off from 38.6% to 19.6% at a current density up to 150 mA cm−2. The improvement of device performance by the Al2O3 interlayer is attributed to the reduction of electron injection and exciton quenching induced by zinc oxide (ZnO) nanoparticles (NPs). This work demonstrates that the Al2O3 interlayer is a promising solution for charge control in QLEDs and that the ALD process is a reliable approach for atomic scale thickness control for QLEDs. We developed a 1.0 nm thick aluminum oxide (Al2O3) interlayer as an electron blocking layer to reduce leakage current and suppress exciton quenching induced by charge imbalance in inverted quantum dot light emitting diodes (QLEDs).![]()
Collapse
Affiliation(s)
- Hoseok Jin
- School of Chemical Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| | - Hyungseok Moon
- School of Chemical Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| | - Woosuk Lee
- School of Chemical Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| | - Hyeok Hwangbo
- School of Chemical Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| | - Sang Heon Yong
- School of Chemical Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
| | - Ho Kyoon Chung
- SKKU Advanced Institute of Nanotechnology
- Sungkyunkwan University
- Suwon
- Republic of Korea
| | - Heeyeop Chae
- School of Chemical Engineering
- Sungkyunkwan University
- Suwon
- Republic of Korea
- SKKU Advanced Institute of Nanotechnology
| |
Collapse
|
36
|
Tu Y, Wang S, Zhang Y, Chen L, Fang Y, Du Z. Balanced carrier injection of quantum dots light-emitting diodes: the case of interface barrier of bilayer ZnO electron transport layer. NANOTECHNOLOGY 2018; 29:485203. [PMID: 30207296 DOI: 10.1088/1361-6528/aae0b8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Unbalanced carrier injection is one of the most important reasons for the efficiency roll-off in quantum dot light-emitting diodes. Reducing the electron injection can effectively balance the carrier transport and improve the optoelectronic performance of the device. In this work, a bilayer ZnO electron transport layer was fabricated by twice spin-coating and annealing methods. More than 60% of electrons are effectively blocked by the ZnO interface barrier compared with the standard device, resulting in increasing the maximum luminance of the device from 25 390 to 48 220 cd m-2 and the current efficiency from 1.5 to 3.2 cd A-1.
Collapse
Affiliation(s)
- Yufei Tu
- Key Laboratory for Special Functional Materials of Ministry of Education, National & Local Joint Engineering Research Center for High-efficiency Display and Lighting Technology, School of Materials Science and Engineering, and Collaborative Innovation Center of Nano Functional Materials and Applications, Henan University, Kaifeng 475004, People's Republic of China
| | | | | | | | | | | |
Collapse
|
37
|
Su Q, Sun Y, Zhang H, Chen S. Origin of Positive Aging in Quantum-Dot Light-Emitting Diodes. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2018; 5:1800549. [PMID: 30356978 PMCID: PMC6193172 DOI: 10.1002/advs.201800549] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 05/12/2018] [Indexed: 05/15/2023]
Abstract
The phenomenon of positive aging, i.e., efficiency increased with time, is observed in quantum-dot light-emitting diodes (QLEDs). For example, the external quantum efficiency (EQE) of blue QLEDs is significantly improved from 4.93% to 12.97% after storage for 8 d. The origin of such positive aging is thoroughly investigated. The finding indicates that the interfacial reaction between Al cathode and ZnMgO electron transport layer accounts for such improvement. During shelf-aging, the Al slowly reacts with the oxygen from ZnMgO, and consequently, leads to the formation of AlO x and the production of oxygen vacancies in ZnMgO. The AlO x interlayer reduces the electron injection barrier while the oxygen vacancies increase the conductivity of ZnMgO and, as a result, the electron injection is effectively enhanced. Moreover, the AlO x can effectively suppress the quenching of excitons by metal electrode. Due to the enhancement of electron injection and suppression of exciton quenching, the aged blue, green, and red QLEDs exhibit a 2.6-, 1.3-, and 1.25-fold efficiency improvement, respectively. The studies disclose the origin of positive aging and provide a new insight into the exciton quenching mechanisms, which would be useful for further constructing efficient QLED devices.
Collapse
Affiliation(s)
- Qiang Su
- Department of Electrical and Electronic EngineeringSouthern University of Science and TechnologyShenzhen518055P. R. China
| | - Yizhe Sun
- Department of Electrical and Electronic EngineeringSouthern University of Science and TechnologyShenzhen518055P. R. China
| | - Heng Zhang
- Department of Electrical and Electronic EngineeringSouthern University of Science and TechnologyShenzhen518055P. R. China
| | - Shuming Chen
- Department of Electrical and Electronic EngineeringSouthern University of Science and TechnologyShenzhen518055P. R. China
| |
Collapse
|
38
|
Zhang Z, Ye Y, Pu C, Deng Y, Dai X, Chen X, Chen D, Zheng X, Gao Y, Fang W, Peng X, Jin Y. High-Performance, Solution-Processed, and Insulating-Layer-Free Light-Emitting Diodes Based on Colloidal Quantum Dots. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1801387. [PMID: 29808563 DOI: 10.1002/adma.201801387] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 04/08/2018] [Indexed: 05/12/2023]
Abstract
Quantum-dot light-emitting diodes (QLEDs) may combine superior properties of colloidal quantum dots (QDs) and advantages of solution-based fabrication techniques to realize high-performance, large-area, and low-cost electroluminescence devices. In the state-of-the-art red QLED, an ultrathin insulating layer inserted between the QD layer and the oxide electron-transporting layer (ETL) is crucial for both optimizing charge balance and preserving the QDs' emissive properties. However, this key insulating layer demands very accurate and precise control over thicknesses at sub-10 nm level, causing substantial difficulties for industrial production. Here, it is reported that interfacial exciton quenching and charge balance can be independently controlled and optimized, leading to devices with efficiency and lifetime comparable to those of state-of-the-art devices. Suppressing exciton quenching at the ETL-QD interface, which is identified as being obligatory for high-performance devices, is achieved by adopting Zn0.9 Mg0.1 O nanocrystals, instead of ZnO nanocrystals, as ETLs. Optimizing charge balance is readily addressed by other device engineering approaches, such as controlling the oxide ETL/cathode interface and adjusting the thickness of the oxide ETL. These findings are extended to fabrication of high-efficiency green QLEDs without ultrathin insulating layers. The work may rationalize the design and fabrication of high-performance QLEDs without ultrathin insulating layers, representing a step forward to large-scale production and commercialization.
Collapse
Affiliation(s)
- Zhenxing Zhang
- Centre for Chemistry of High-Performance & Novel Materials, State Key Laboratory of Silicon Materials, Department of Chemistry, Zhejiang University, Hangzhou, 310027, China
| | - Yuxun Ye
- State Key Laboratory of Silicon Materials, Centre for Chemistry of High-Performance & Novel Materials, School of Materials Science and Engineering, Hangzhou, 310027, China
| | - Chaodan Pu
- Centre for Chemistry of High-Performance & Novel Materials, Department of Chemistry, Hangzhou, 310027, China
| | - Yunzhou Deng
- Centre for Chemistry of High-Performance & Novel Materials, State Key Laboratory of Silicon Materials, Department of Chemistry, Zhejiang University, Hangzhou, 310027, China
| | - Xingliang Dai
- State Key Laboratory of Silicon Materials, Centre for Chemistry of High-Performance & Novel Materials, School of Materials Science and Engineering, Hangzhou, 310027, China
| | - Xiaopeng Chen
- Najing Technology Corporation LTD., Hangzhou, 310052, China
| | - Dong Chen
- Centre for Chemistry of High-Performance & Novel Materials, State Key Laboratory of Silicon Materials, Department of Chemistry, Zhejiang University, Hangzhou, 310027, China
| | - Xuerong Zheng
- Centre for Chemistry of High-Performance & Novel Materials, State Key Laboratory of Silicon Materials, Department of Chemistry, Zhejiang University, Hangzhou, 310027, China
| | - Yuan Gao
- Najing Technology Corporation LTD., Hangzhou, 310052, China
| | - Wei Fang
- Center for Chemistry of High-Performance & Novel Materials, State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Xiaogang Peng
- Centre for Chemistry of High-Performance & Novel Materials, Department of Chemistry, Hangzhou, 310027, China
- Najing Technology Corporation LTD., Hangzhou, 310052, China
| | - Yizheng Jin
- Centre for Chemistry of High-Performance & Novel Materials, State Key Laboratory of Silicon Materials, Department of Chemistry, Zhejiang University, Hangzhou, 310027, China
| |
Collapse
|
39
|
Zhang M, Hu B, Meng L, Bian R, Wang S, Wang Y, Liu H, Jiang L. Ultrasmooth Quantum Dot Micropatterns by a Facile Controllable Liquid-Transfer Approach: Low-Cost Fabrication of High-Performance QLED. J Am Chem Soc 2018; 140:8690-8695. [DOI: 10.1021/jacs.8b02948] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Min Zhang
- Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry, Beihang University, Beijing 100191, P. R. China
- Key Lab for Special Functional Materials of Ministry of Education, Collaborative Innovation Center of Nano Functional Materials and Applications, Henan University, Kaifeng 475000, P. R. China
| | - Binbin Hu
- Key Lab for Special Functional Materials of Ministry of Education, Collaborative Innovation Center of Nano Functional Materials and Applications, Henan University, Kaifeng 475000, P. R. China
| | - Lili Meng
- Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry, Beihang University, Beijing 100191, P. R. China
| | - Ruixin Bian
- Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry, Beihang University, Beijing 100191, P. R. China
| | - Siyuan Wang
- Suzhou Xingshuo
Nanotech Company, Limited (Mesolight), Suzhou 215123, P. R. China
| | - Yunjun Wang
- Suzhou Xingshuo
Nanotech Company, Limited (Mesolight), Suzhou 215123, P. R. China
| | - Huan Liu
- Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry, Beihang University, Beijing 100191, P. R. China
| | - Lei Jiang
- Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry, Beihang University, Beijing 100191, P. R. China
| |
Collapse
|
40
|
Sun Y, Wang W, Zhang H, Su Q, Wei J, Liu P, Chen S, Zhang S. High-Performance Quantum Dot Light-Emitting Diodes Based on Al-Doped ZnO Nanoparticles Electron Transport Layer. ACS APPLIED MATERIALS & INTERFACES 2018; 10:18902-18909. [PMID: 29745643 DOI: 10.1021/acsami.8b04754] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
ZnO nanoparticles (NPs) are widely used as the electron transport layer (ETL) in quantum dot light-emitting diodes (QLEDs) owing to their suitable electrical properties. However, because of the well-aligned conduction band levels, electrons in QDs can be spontaneously transferred to adjacent ZnO NPs, leading to severe exciton dissociation, which reduces the proportion of radiative recombination and deteriorates the device efficiency. In this work, Al-doped ZnO NPs are thoroughly investigated as a replacement of ZnO for QLEDs. The energy band structures of Al-doped ZnO are modified by adjusting the concentration of Al dopants. With the increasing Al content, the work function and the conduction band edge of ZnO are gradually raised, and thus the charge transfer at the interface of QDs/ETL is effectively suppressed. Consequently, the green QLEDs with 10% Al-doped ZnO NPs exhibit maximum current efficiency and external quantum efficiency of 59.7 cd/A and 14.1%, which are about 1.8-fold higher than 33.3 cd/A and 7.9% of the devices with undoped ZnO NPs. Our work suggests that Al-doped ZnO NPs can serve as a good electron transport/injection material in QLEDs and other optoelectronic devices.
Collapse
Affiliation(s)
- Yizhe Sun
- Institute of Microelectronics, Peking University , Beijing 100871 , P. R. China
- Department of Electrical and Electronic Engineering , Southern University of Science and Technology , Shenzhen 518055 , P. R. China
| | - Weigao Wang
- Department of Electrical and Electronic Engineering , Southern University of Science and Technology , Shenzhen 518055 , P. R. China
| | - Heng Zhang
- Department of Electrical and Electronic Engineering , Southern University of Science and Technology , Shenzhen 518055 , P. R. China
| | - Qiang Su
- Department of Electrical and Electronic Engineering , Southern University of Science and Technology , Shenzhen 518055 , P. R. China
| | - Jiangliu Wei
- Guangdong Poly Optoelectronics Co., Ltd. , Jiangmen 529040 , P. R. China
| | - Pai Liu
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices , South China University of Technology , Guangzhou 510640 , P. R. China
- Guangdong Poly Optoelectronics Co., Ltd. , Jiangmen 529040 , P. R. China
| | - Shuming Chen
- Department of Electrical and Electronic Engineering , Southern University of Science and Technology , Shenzhen 518055 , P. R. China
| | - Shengdong Zhang
- Institute of Microelectronics, Peking University , Beijing 100871 , P. R. China
| |
Collapse
|
41
|
Fu Y, Jiang W, Kim D, Lee W, Chae H. Highly Efficient and Fully Solution-Processed Inverted Light-Emitting Diodes with Charge Control Interlayers. ACS APPLIED MATERIALS & INTERFACES 2018; 10:17295-17300. [PMID: 29738225 DOI: 10.1021/acsami.8b05092] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In this work, we developed a charge control sandwich structure around QD layers for the inverted QLEDs, the performance of which is shown to exceed that of the conventional QLEDs in terms of the external quantum efficiency (EQE) and the current efficiency (CE). The QD light-emitting layer (EML) is sandwiched with two ultrathin interfacial layers: one is a poly(9-vinlycarbazole) (PVK) layer to prevent excess electrons, and the other is a polyethylenimine ethoxylated (PEIE) layer to reduce the hole injection barrier. The sandwich structure resolves the imbalance between injected holes and electrons and brings the level of balanced charge carriers to a maximum. We demonstrated the highly improved performance of 89.8 cd/A of current efficiency, 22.4% of external quantum efficiency, and 72 814 cd m-2 of maximum brightness with the solution-processed inverted QLED. This sandwich structure (PVK/QD/PEIE), as a framework, can be applied to various QLED devices for enhancing performance.
Collapse
Affiliation(s)
- Yan Fu
- College of Materials Science and Engineering , Jilin Institute of Chemical Technology , Jilin 132022 , P. R. China
| | | | | | | | | |
Collapse
|
42
|
Wang T, Zhu B, Wang S, Yuan Q, Zhang H, Kang Z, Wang R, Zhang H, Ji W. Influence of Shell Thickness on the Performance of NiO-Based All-Inorganic Quantum Dot Light-Emitting Diodes. ACS APPLIED MATERIALS & INTERFACES 2018; 10:14894-14900. [PMID: 29637767 DOI: 10.1021/acsami.8b01814] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The effect of shell thickness on the performance of all-inorganic quantum dot light-emitting diodes (QLEDs) is explored by employing a series of green quantum dots (QDs) (Zn xCd1- xSe/ZnS core/shell QDs with different ZnS shell thicknesses) as the emitters. ZnO nanoparticles and sol-gel NiO are employed as the electron and hole transport materials, respectively. Time-resolved and steady-state photoluminescence results indicate that positive charging processes might occur for the QDs deposited on NiO, which results in emission quenching of QDs and poor device performance. The thick shell outside the core in QDs not only largely suppresses the QD emission quenching but also effectively preserves the excitons in QDs from dissociation of electron-hole pairs when they are subjected to an electric field. The peak efficiency of 4.2 cd/A and maximum luminance of 4205 cd/m2 are achieved for the device based on QDs with the thickest shells (∼4.2 nm). We anticipate that these results will spur progress toward the design and realization of efficient all-inorganic QLEDs as a platform for the QD-based full-colored displays.
Collapse
Affiliation(s)
- Ting Wang
- Key Lab of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics , Jilin University , 2699 Qianjin Street , Changchun 130012 , China
| | - Bingyan Zhu
- Key Lab of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics , Jilin University , 2699 Qianjin Street , Changchun 130012 , China
| | - Shuangpeng Wang
- Institute of Applied Physics and Materials Engineering , University of Macau , Avenida da Universidade , Taipa 999078 , Macau SAR , China
| | - Qilin Yuan
- Key Lab of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics , Jilin University , 2699 Qianjin Street , Changchun 130012 , China
| | - Han Zhang
- Key Lab of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics , Jilin University , 2699 Qianjin Street , Changchun 130012 , China
| | - Zhihui Kang
- Key Lab of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics , Jilin University , 2699 Qianjin Street , Changchun 130012 , China
| | - Rong Wang
- Key Lab of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics , Jilin University , 2699 Qianjin Street , Changchun 130012 , China
| | - Hanzhuang Zhang
- Key Lab of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics , Jilin University , 2699 Qianjin Street , Changchun 130012 , China
| | - Wenyu Ji
- Key Lab of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics , Jilin University , 2699 Qianjin Street , Changchun 130012 , China
| |
Collapse
|
43
|
Davidson-Hall T, Aziz H. The role of polyethylenimine in enhancing the efficiency of quantum dot light-emitting devices. NANOSCALE 2018; 10:2623-2631. [PMID: 29354848 DOI: 10.1039/c7nr07683e] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Although the use of polyethylenimine (PEI) in quantum dot light-emitting devices (QDLEDs) has recently been found to improve efficiency, the mechanism behind this increase has been disputed in the literature. In this work, we conduct investigations to elucidate the role of PEI in enhancing QDLED efficiency. Spectroscopic studies of devices with a phosphorescent marking layer reveal that the PEI layer increases, rather than decreases, the generation of excitons within the hole transporting layer indicative of increased electron injection. Delayed electroluminescence measurements corroborate these findings as devices with a PEI interlayer exhibit a greater concentration of excess mobile and trapped electrons. We attribute the improvement in efficiency despite the ensuing increased charge imbalance within the devices to the passivation of exciton quenching at the ZnO/QD interface. The increase in efficiency predominantly occurs over low driving currents which is particularly attractive for the brightness targets of display applications. Furthermore, despite the increased charge imbalance, the PEI passivation layer appears to have little effect on QDLED stability. This shows that excess electrons and Auger quenching by unneutralized electrons are not detrimental to QDLED stability.
Collapse
Affiliation(s)
- Tyler Davidson-Hall
- Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada.
| | | |
Collapse
|
44
|
Sun Y, Jiang Y, Peng H, Wei J, Zhang S, Chen S. Efficient quantum dot light-emitting diodes with a Zn 0.85Mg 0.15O interfacial modification layer. NANOSCALE 2017; 9:8962-8969. [PMID: 28548170 DOI: 10.1039/c7nr02099f] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Efficient inverted quantum-dot (QD) light-emitting diodes (LEDs) are demonstrated by using 15% Mg doped ZnO (Zn0.85Mg0.15O) as an interfacial modification layer. By doping Mg into ZnO, the conduction band level, the density of oxygen vacancies and the conductivity of the ZnO can be tuned. To suppress excess electron injection, a 13 nm Zn0.85Mg0.15O interlayer with a relatively higher conduction band edge and lower conductivity is inserted between the ZnO electron transport layer and QD light-emitting layer, which improves the balance of charge injection and blocks the non-radiative pathway. Moreover, according to the electrical and optical studies of devices and materials, quenching sites at the ZnO surface are effectively reduced by Mg-doping. Therefore exciton quenching induced by ZnO nanoparticles is largely suppressed by capping ZnO with Zn0.85Mg0.15O. Consequently, the red QLEDs with a Zn0.85Mg0.15O interfacial modification layer exhibit superior performance with a maximum current efficiency of 18.69 cd A-1 and a peak external quantum efficiency of 13.57%, which are about 1.72- and 1.74-fold higher than 10.88 cd A-1 and 7.81% of the devices without Zn0.85Mg0.15O. Similar improvements are also achieved in green QLEDs. Our results indicate that Zn0.85Mg0.15O can serve as an effective interfacial modification layer for suppressing exciton quenching and improving the charge balance of the devices.
Collapse
Affiliation(s)
- Yizhe Sun
- Institute of Microelectronics, Peking University, Beijing, 100871, P. R. China.
| | | | | | | | | | | |
Collapse
|
45
|
Ding K, Chen H, Fan L, Wang B, Huang Z, Zhuang S, Hu B, Wang L. Polyethylenimine Insulativity-Dominant Charge-Injection Balance for Highly Efficient Inverted Quantum Dot Light-Emitting Diodes. ACS APPLIED MATERIALS & INTERFACES 2017; 9:20231-20238. [PMID: 28524654 DOI: 10.1021/acsami.7b04662] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Quantum dot (QD) light-emitting diodes (QLEDs) with an inverted architecture suffer from charge-injection imbalance and severe QD charging, which degrade device performance. Blocking excess electron injection into QDs is crucial for efficient inverted QLEDs. It is observed that polyethylenimine (PEI) has two opposite effects on electron injection: one is blocking electron injection by its intrinsic insulativity and the other one is promoting electron injection by reducing the work function of ZnO/PEI. In this work, the insulating nature of PEI has been dominantly utilized to reduce electron injection and the charge-injection balance is realized when PEI becomes thicker and blocks more excess electrons. Furthermore, PEI contributes to QD charging suppression and results in a smoother surface morphology than that of ZnO nanoparticles, which is beneficial for leakage current reduction and QD deposition. As a result, the optimized QLED with 15 nm PEI shows a 2.5 times improved efficiency compared to that of the QLED without PEI. Also, the QLED possesses the maximum external quantum efficiency and current efficiency of 16.5% and 18.8 cd/A, respectively, accompanied with a low efficiency roll-off of 15% at 1000 cd/m2, which is comparable to that of the reported inverted red QLED with the highest efficiency.
Collapse
Affiliation(s)
- Ke Ding
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology , Wuhan 430074, China
| | - Hongting Chen
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology , Wuhan 430074, China
| | - Lianwei Fan
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology , Wuhan 430074, China
| | - Bo Wang
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology , Wuhan 430074, China
| | - Zhi Huang
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology , Wuhan 430074, China
| | - Shaoqing Zhuang
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology , Wuhan 430074, China
| | - Bin Hu
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology , Wuhan 430074, China
| | - Lei Wang
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology , Wuhan 430074, China
| |
Collapse
|
46
|
Wang L, Lv Y, Lin J, Fan Y, Zhao J, Wang Y, Liu X. High-efficiency inverted quantum dot light-emitting diodes with enhanced hole injection. NANOSCALE 2017; 9:6748-6754. [PMID: 28485442 DOI: 10.1039/c7nr01414g] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Hybrid MoO3/HAT-CN is employed as a hole injection layer (HIL) in green inverted colloidal quantum dot light-emitting devices (QLEDs). The hybrid HILs can be easily prepared and have been found to effectively improve the electroluminescent properties. The best performance device had an HIL of 1.5 nm-thick MoO3/2.5 nm-thick HAT-CN and showed a turn-on voltage of 1.9 V, a maximum current efficiency (CEmax) of 41.3 cd A-1, and maximum external quantum efficiency of 9.72%. Compared to the corresponding devices with the single MoO3 or HAT-CN interlayer, the CEmax of the hole-only devices was improved by 1.6 or 1.5 times, respectively. The measured electrical performance shows that hole-only devices with hybrid HILs have a smaller leakage current density at low driving voltage and much enhanced hole injection current than the devices with single interlayers. It indicates that much improved electroluminescent efficiency in green inverted QLEDs with hybrid MoO3/HAT-CN orginates from the significant enhancement of hole injection efficiency and suppression of space charge accumulation in the quantum dot-emitting region due to the improved balance of the charge carriers. The hybrid HILs can be extended to other color inverted QLEDs, which are favorable to achieve bright, highly efficient, and color saturation devices for display applications.
Collapse
Affiliation(s)
- Lishuang Wang
- State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China.
| | | | | | | | | | | | | |
Collapse
|
47
|
Dai X, Deng Y, Peng X, Jin Y. Quantum-Dot Light-Emitting Diodes for Large-Area Displays: Towards the Dawn of Commercialization. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1607022. [PMID: 28256780 DOI: 10.1002/adma.201607022] [Citation(s) in RCA: 256] [Impact Index Per Article: 36.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Revised: 02/02/2017] [Indexed: 05/21/2023]
Abstract
Quantum dots are a unique class of emitters with size-tunable emission wavelengths, saturated emission colors, near-unity luminance efficiency, inherent photo- and thermal- stability and excellent solution processability. Quantum dots have been used as down-converters for back-lighting in liquid-crystal displays to improve color gamut, leading to the booming of quantum-dot televisions in consumer market. In the past few years, efficiency and lifetime of electroluminescence devices based on quantum dots achieved tremendous progress. These encouraging facts foreshadow the commercialization of quantum-dot light-emitting diodes (QLEDs), which promises an unprecedented generation of cost-effective, large-area, energy-saving, wide-color-gamut, ultra-thin and flexible displays. Here we provide a Progress Report, covering interdisciplinary aspects including material chemistry of quantum dots and charge-transporting layers, optimization and mechanism studies of prototype devices and processing techniques to produce large-area and high-resolution red-green-blue pixel arrays. We also identify a few key challenges facing the development of active-matrix QLED displays.
Collapse
Affiliation(s)
- Xingliang Dai
- Center for Chemistry of High-Performance & Novel Materials, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, People's Republic of China
| | - Yunzhou Deng
- Center for Chemistry of High-Performance & Novel Materials, State Key Laboratory of Silicon Materials, Department of Chemistry, Zhejiang University, Hangzhou, 310027, People's Republic of China
| | - Xiaogang Peng
- Center for Chemistry of High-Performance & Novel Materials, Department of Chemistry, Zhejiang University, Hangzhou, 310027, People's Republic of China
| | - Yizheng Jin
- Center for Chemistry of High-Performance & Novel Materials, State Key Laboratory of Silicon Materials, Department of Chemistry, Zhejiang University, Hangzhou, 310027, People's Republic of China
| |
Collapse
|
48
|
Liang X, Bai S, Wang X, Dai X, Gao F, Sun B, Ning Z, Ye Z, Jin Y. Colloidal metal oxide nanocrystals as charge transporting layers for solution-processed light-emitting diodes and solar cells. Chem Soc Rev 2017; 46:1730-1759. [DOI: 10.1039/c6cs00122j] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
This review bridges the chemistry of colloidal oxide nanocrystals and their application as charge transporting interlayers in solution-processed optoelectronics.
Collapse
Affiliation(s)
- Xiaoyong Liang
- State Key Laboratory of Silicon Materials
- School of Materials Science and Engineering
- Zhejiang University
- Hangzhou 310027
- People's Republic of China
| | - Sai Bai
- Department of Physics
- Chemistry and Biology (IFM)
- Linköping University
- SE-581 83 Linköping
- Sweden
| | - Xin Wang
- State Key Laboratory of Silicon Materials
- School of Materials Science and Engineering
- Zhejiang University
- Hangzhou 310027
- People's Republic of China
| | - Xingliang Dai
- State Key Laboratory of Silicon Materials
- School of Materials Science and Engineering
- Zhejiang University
- Hangzhou 310027
- People's Republic of China
| | - Feng Gao
- Department of Physics
- Chemistry and Biology (IFM)
- Linköping University
- SE-581 83 Linköping
- Sweden
| | - Baoquan Sun
- Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices
- Institute of Functional Nano & Soft Materials (FUNSOM)
- Soochow University
- Suzhou 215123
- People's Republic of China
| | | | - Zhizhen Ye
- State Key Laboratory of Silicon Materials
- School of Materials Science and Engineering
- Zhejiang University
- Hangzhou 310027
- People's Republic of China
| | - Yizheng Jin
- Center for Chemistry of High-Performance & Novel Materials
- State Key Laboratory of Silicon Materials
- Department of Chemistry
- Zhejiang University
- Hangzhou 310027
| |
Collapse
|