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Zhang T, Wang L, Jiang R, Wu Z, Han Y, Xu B, Jin X, Li Q, Bai J. Well-type thick-shell quantum dots combined with double hole transport layers device structure assisted realization of high-performance quantum dot light-emitting diodes. OPTICS EXPRESS 2024; 32:20618-20628. [PMID: 38859439 DOI: 10.1364/oe.523932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Accepted: 05/12/2024] [Indexed: 06/12/2024]
Abstract
Quantum dot (QD) light-emitting diodes (QLEDs) are promising for next-generation lighting and displays. Considering the optimization design of both the QD and device structure is expected to improve the QLED's performance significantly but has rarely been reported. Here, we use the thick-shell QDs combined with a dual-hole transport layer device structure to construct a high-efficiency QLED. The optimized thick-shell QDs with CdS/CdSe/CdS/ZnS seed/spherical quantum well/shell/shell geometry exhibit a high photoluminescence quantum yield of 96% at a shell thickness of 5.9 nm. The intermediate emissive CdSe layer with coherent strain ensures defect-free growth of the thick CdS and ZnS outer shells. Based on the orthogonal solvents assisted Poly-TPD&PVK dual-hole transport layer device architecture, the champion QLED achieved a maximum external quantum efficiency of 22.5% and a maximum luminance of 259955 cd m-2, which are 1.6 and 3.7 times that of thin-shell QDs based devices with single hole transport layer, respectively. Our study provides a feasible idea for further improving the performance of QLED devices.
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Ma S, Cao F, Jia G, Wu Q, Wang S, Yang X. Blue ZnSeTe quantum dot light-emitting diodes with low efficiency roll-off enabled by an in situ hybridization of ZnMgO nanoparticles and amino alcohol molecules. NANOSCALE 2024; 16:10441-10447. [PMID: 38742531 DOI: 10.1039/d4nr01515k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
ZnSeTe quantum dots (QDs) have been employed as promising emitters for blue QD-based light-emitting diodes (QLEDs) due to their unique optoelectronic properties and environmental friendliness. However, such QLEDs usually suffer from serious efficiency roll-off primarily stemming from exciton loss at the interface of the QD layer and the ZnMgO (ZMO) electron transport layer (ETL), which remarkably hinders their application in flat-panel displays. Herein, we propose an in situ hybridization strategy that involves the pre-introduction of amino alcohols into the reaction solution. This strategy effectively suppresses the nucleophilic condensation process by facilitating the coordination of ammonium and hydroxyl groups with metal cations (M2+, i.e. Zn2+ and Mg2+). It slows down the growth rate of ZMO nanoparticles (NPs) while simultaneously facilitating M-O coordination, resulting in the synthesis of small-sized and low-defect ZMO NPs. Notably, this in situ hybridization approach not only alleviates emission quenching at the QDs/ETL interface but also elevates the energy level of the ETL for enhancing carrier injection. We further investigated the impact of amino alcohols with varying carbon-chain lengths on the performance of ZMO NPs and the corresponding LED devices. The optimal blue ZnSeTe QLED demonstrates an impressive EQE of 8.6% with only an ∼11% drop when the current density is increased to 200 mA cm-2, and the device operating lifetime extends to over 1300 h. Conversely, the device utilizing traditionally post-treated ZMO NPs as the ETL exhibits 45% efficiency roll-off and device lifetime of merely 190 h.
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Affiliation(s)
- Shaolin Ma
- Shanghai University Microelectronic R&D Center, Shanghai University, Shanghai 201900, P. R. China
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, Shanghai 200072, P. R. China.
| | - Fan Cao
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, Shanghai 200072, P. R. China.
| | - Guohua Jia
- School of Molecular and Life Sciences, Curtin University, Bentley, WA 6102, Australia
| | - Qianqian Wu
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, Shanghai 200072, P. R. China.
| | - Sheng Wang
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, Shanghai 200072, P. R. China.
| | - Xuyong Yang
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, Shanghai 200072, P. R. China.
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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.
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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
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Hou S, Gao X, Lv X, Zhao Y, Yin X, Liu Y, Fang J, Yu X, Ma X, Ma T, Su D. Decade Milestone Advancement of Defect-Engineered g-C 3N 4 for Solar Catalytic Applications. NANO-MICRO LETTERS 2024; 16:70. [PMID: 38175329 PMCID: PMC10766942 DOI: 10.1007/s40820-023-01297-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Accepted: 11/17/2023] [Indexed: 01/05/2024]
Abstract
Over the past decade, graphitic carbon nitride (g-C3N4) has emerged as a universal photocatalyst toward various sustainable carbo-neutral technologies. Despite solar applications discrepancy, g-C3N4 is still confronted with a general fatal issue of insufficient supply of thermodynamically active photocarriers due to its inferior solar harvesting ability and sluggish charge transfer dynamics. Fortunately, this could be significantly alleviated by the "all-in-one" defect engineering strategy, which enables a simultaneous amelioration of both textural uniqueness and intrinsic electronic band structures. To this end, we have summarized an unprecedently comprehensive discussion on defect controls including the vacancy/non-metallic dopant creation with optimized electronic band structure and electronic density, metallic doping with ultra-active coordinated environment (M-Nx, M-C2N2, M-O bonding), functional group grafting with optimized band structure, and promoted crystallinity with extended conjugation π system with weakened interlayered van der Waals interaction. Among them, the defect states induced by various defect types such as N vacancy, P/S/halogen dopants, and cyano group in boosting solar harvesting and accelerating photocarrier transfer have also been emphasized. More importantly, the shallow defect traps identified by femtosecond transient absorption spectra (fs-TAS) have also been highlighted. It is believed that this review would pave the way for future readers with a unique insight into a more precise defective g-C3N4 "customization", motivating more profound thinking and flourishing research outputs on g-C3N4-based photocatalysis.
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Affiliation(s)
- Shaoqi Hou
- School of Mathematical and Physical Sciences, Faculty of Science, University of Technology Sydney (UTS), Sydney, NSW, 2007, Australia
| | - Xiaochun Gao
- Laboratory of Plasma and Energy Conversion, School of Physics and Optoelectronic Engineering, Ludong University, 186 Middle Hongqi Road, Yantai, 264025, People's Republic of China.
| | - Xingyue Lv
- Laboratory of Plasma and Energy Conversion, School of Physics and Optoelectronic Engineering, Ludong University, 186 Middle Hongqi Road, Yantai, 264025, People's Republic of China
| | - Yilin Zhao
- Laboratory of Plasma and Energy Conversion, School of Physics and Optoelectronic Engineering, Ludong University, 186 Middle Hongqi Road, Yantai, 264025, People's Republic of China
| | - Xitao Yin
- Laboratory of Plasma and Energy Conversion, School of Physics and Optoelectronic Engineering, Ludong University, 186 Middle Hongqi Road, Yantai, 264025, People's Republic of China
| | - Ying Liu
- Laboratory of Plasma and Energy Conversion, School of Physics and Optoelectronic Engineering, Ludong University, 186 Middle Hongqi Road, Yantai, 264025, People's Republic of China
| | - Juan Fang
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, 100083, People's Republic of China
| | - Xingxing Yu
- Department of Chemistry, The University of Tokyo, 7-3-1 Hogo, Bunkyo, Tokyo, Japan
| | - Xiaoguang Ma
- Laboratory of Plasma and Energy Conversion, School of Physics and Optoelectronic Engineering, Ludong University, 186 Middle Hongqi Road, Yantai, 264025, People's Republic of China.
| | - Tianyi Ma
- School of Science, STEM College, RMIT University, Melbourne, VIC, 3000, Australia.
| | - Dawei Su
- School of Mathematical and Physical Sciences, Faculty of Science, University of Technology Sydney (UTS), Sydney, NSW, 2007, Australia.
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Ghorbani A, Chen J, Chun P, Lyu Q, Cotella G, Aziz H. Changes in Hole and Electron Injection under Electrical Stress and the Rapid Electroluminescence Loss in Blue Quantum-Dot Light-Emitting Devices. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2304580. [PMID: 37653596 DOI: 10.1002/smll.202304580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 08/17/2023] [Indexed: 09/02/2023]
Abstract
Blue quantum dot light-emitting devices (QLEDs) suffer from fast electroluminescence (EL) loss when under electrical bias. Here, it is identified that the fast EL loss in blue QLEDs is not due to a deterioration in the photoluminescence quantum yield of the quantum dots (QDs), contrary to what is commonly believed, but rather arises primarily from changes in charge injection overtime under the bias that leads to a deterioration in charge balance. Measurements on hole-only and electron-only devices show that hole injection into blue QDs increases over time whereas electron injection decreases. Results also show that the changes are associated with changes in hole and electron trap densities. The results are further verified using QLEDs with blue and red QDs combinations, capacitance versus voltage, and versus time characteristics of the blue QLEDs. The changes in charge injection are also observed to be partially reversible, and therefore using pulsed current instead of constant current bias for driving the blue QLEDs leads to an almost 2.5× longer lifetime at the same initial luminance. This work systematically investigates the origin of blue QLEDs EL loss and provides insights for designing improved blue QDs paving the way for QLEDs technology commercialization.
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Affiliation(s)
- 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
| | - 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
- Institute of Optoelectronics Technology, Beijing Jiaotong University, Beijing, 100044, China
| | - 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, 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
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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.
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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
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Kim Y, Park H, Yoon J, Yoon H, Jeong S, Kim D, Hong Y. Monomer-mixed hole transport layers for improving hole injection of quantum dot light-emitting diodes. OPTICS EXPRESS 2023; 31:20730-20739. [PMID: 37381189 DOI: 10.1364/oe.493134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Accepted: 05/19/2023] [Indexed: 06/30/2023]
Abstract
Quantum-dot light-emitting diodes (QLEDs) are promising components for next-generation displays and related applications. However, their performance is critically limited by inherent hole-injection barrier caused by deep highest-occupied molecular orbital levels of quantum dots. Herein, we present an effective method for enhancing the performance of QLEDs by incorporating a monomer (TCTA or mCP) into hole-transport layers (HTL). The impact of different monomer concentrations on the characteristics of QLEDs were investigated. The results indicate that sufficient monomer concentrations improve the current efficiency and power efficiency. The increased hole current using monomer-mixed HTL suggests that our method holds considerable potential for high-performance QLEDs.
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Azadinia M, Davidson-Hall T, Chung DS, Ghorbani A, Samaeifar F, Chen J, Chun P, Lyu Q, Cotella G, Aziz H. Inverted Solution-Processed Quantum Dot Light-Emitting Devices with Wide Band Gap Quantum Dot Interlayers. ACS APPLIED MATERIALS & INTERFACES 2023; 15:23631-23641. [PMID: 37141421 DOI: 10.1021/acsami.3c02356] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Despite its benefits for facilitating device fabrication, utilization of a polymeric hole transport layer (HTL) in inverted quantum dots (QDs) light-emitting devices (IQLEDs) often leads to poor device performance. In this work, we find that the poor performance arises primarily from electron leakage, inefficient charge injection, and significant exciton quenching at the HTL interface in the inverted architecture and not due to solvent damage effects as is widely believed. We also find that using a layer of wider band gap QDs as an interlayer (IL) in between the HTL and the main QDs' emission material layer (EML) can facilitate hole injection, suppress electron leakage, and reduce exciton quenching, effectively mitigating the poor interface effects and resulting in high electroluminescence performance. Using an IL in IQLEDs with a solution-processed poly(9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine) (TFB), HTL improves the efficiency by 2.85× (from 3 to 8.56%) and prolongs the lifetime by 9.4× (from 1266 to 11,950 h at 100 cd/m2), which, to the best of our knowledge, is the longest lifetime for an R-IQLED with a solution-coated HTL. Measurements on single-carrier devices reveal that while electron injection becomes easier as the band gap of the QDs decreases, hole injection surprisingly becomes more difficult, indicating that EMLs of QLEDs are more electron-rich in the case of red devices and more hole-rich in the case of blue devices. Ultraviolet photoelectron spectroscopy measurements verify that blue QDs have a shallower valence band energy than their red counterparts, corroborating these conclusions. The findings in this work, therefore, provide not only a simple approach for achieving high performance in IQLEDs with solution-coated HTLs but also novel insights into charge injection and its dependence on QDs' band gap as well as into different HTL interface properties of the inverted versus upright architecture.
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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
| | - 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
| | - 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
| | - 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
| | - 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
| | - 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
| | - Peter Chun
- Ottawa IC Laboratory, Huawei Canada, 19 Allstate Parkway, Markham, Ontario L3R 5B4, Canada
| | - Quan Lyu
- Cambridge Research Centre, Huawei Technologies Research & Development (UK) Ltd., Cambridge CB4 0FY, U.K
| | - Giovanni Cotella
- Ipswich Research Centre, Huawei Technologies Research & Development (UK) 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
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