1
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Diesing S, Zhang L, Zysman-Colman E, Samuel IDW. A figure of merit for efficiency roll-off in TADF-based organic LEDs. Nature 2024; 627:747-753. [PMID: 38538942 PMCID: PMC10972759 DOI: 10.1038/s41586-024-07149-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 02/01/2024] [Indexed: 04/01/2024]
Abstract
Organic light-emitting diodes (OLEDs) are a revolutionary light-emitting display technology that has been successfully commercialized in mobile phones and televisions1,2. The injected charges form both singlet and triplet excitons, and for high efficiency it is important to enable triplets as well as singlets to emit light. At present, materials that harvest triplets by thermally activated delayed fluorescence (TADF) are a very active field of research as an alternative to phosphorescent emitters that usually use heavy metal atoms3,4. Although excellent progress has been made, in most TADF OLEDs there is a severe decrease of efficiency as the drive current is increased, known as efficiency roll-off. So far, much of the literature suggests that efficiency roll-off should be reduced by minimizing the energy difference between singlet and triplet excited states (ΔEST) to maximize the rate of conversion of triplets to singlets by means of reverse intersystem crossing (kRISC)5-20. We analyse the efficiency roll-off in a wide range of TADF OLEDs and find that neither of these parameters fully accounts for the reported efficiency roll-off. By considering the dynamic equilibrium between singlets and triplets in TADF materials, we propose a figure of merit for materials design to reduce efficiency roll-off and discuss its correlation with reported data of TADF OLEDs. Our new figure of merit will guide the design and development of TADF materials that can reduce efficiency roll-off. It will help improve the efficiency of TADF OLEDs at realistic display operating conditions and expand the use of TADF materials to applications that require high brightness, such as lighting, augmented reality and lasing.
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Affiliation(s)
- S Diesing
- Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, UK
- Organic Semiconductor Centre, EaStCHEM, School of Chemistry, St Andrews, UK
| | - L Zhang
- Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, UK
- Organic Semiconductor Centre, EaStCHEM, School of Chemistry, St Andrews, UK
| | - E Zysman-Colman
- Organic Semiconductor Centre, EaStCHEM, School of Chemistry, St Andrews, UK.
| | - I D W Samuel
- Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, UK.
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2
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Jia X, Soprani L, Londi G, Hosseini SM, Talnack F, Mannsfeld S, Shoaee S, Neher D, Reineke S, Muccioli L, D'Avino G, Vandewal K, Beljonne D, Spoltore D. Molecularly induced order promotes charge separation through delocalized charge-transfer states at donor-acceptor heterojunctions. MATERIALS HORIZONS 2024; 11:173-183. [PMID: 37915305 DOI: 10.1039/d3mh00526g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2023]
Abstract
The energetic landscape at the interface between electron donating and accepting molecular materials favors efficient conversion of intermolecular charge-transfer (CT) states into free charge carriers (FCC) in high-performance organic solar cells. Here, we elucidate how interfacial energetics, charge generation and radiative recombination are affected by molecular arrangement. We experimentally determine the CT dissociation properties of a series of model, small molecule donor-acceptor blends, where the used acceptors (B2PYMPM, B3PYMPM and B4PYMPM) differ only in the nitrogen position of their lateral pyridine rings. We find that the formation of an ordered, face-on molecular packing in B4PYMPM is beneficial to efficient, field-independent charge separation, leading to fill factors above 70% in photovoltaic devices. This is rationalized by a comprehensive computational protocol showing that, compared to the more amorphous and isotropically oriented B2PYMPM, the higher structural order of B4PYMPM molecules leads to more delocalized CT states. Furthermore, we find no correlation between the quantum efficiency of FCC radiative recombination and the bound or unbound nature of the CT states. This work highlights the importance of structural ordering at donor-acceptor interfaces for efficient FCC generation and shows that less bound CT states do not preclude efficient radiative recombination.
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Affiliation(s)
- Xiangkun Jia
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, 01187 Dresden, Germany
| | - Lorenzo Soprani
- Department of Industrial Chemistry "Toso Montanari", University of Bologna, 40136 Bologna, Italy
| | - Giacomo Londi
- Laboratory for Chemistry of Novel Materials, University of Mons, B-7000 Mons, Belgium.
| | - Seyed Mehrdad Hosseini
- Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
| | - Felix Talnack
- Center for Advancing Electronics Dresden (cfaed) and Faculty of Electrical and Computer Engineering, Technische Universität Dresden, 01062 Dresden, Germany
| | - Stefan Mannsfeld
- Center for Advancing Electronics Dresden (cfaed) and Faculty of Electrical and Computer Engineering, Technische Universität Dresden, 01062 Dresden, Germany
| | - Safa Shoaee
- Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
| | - Dieter Neher
- Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
| | - Sebastian Reineke
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, 01187 Dresden, Germany
| | - Luca Muccioli
- Department of Industrial Chemistry "Toso Montanari", University of Bologna, 40136 Bologna, Italy
| | - Gabriele D'Avino
- Grenoble Alpes University, CNRS, Grenoble INP, Institut Néel, 25 rue des Martyrs, 38042 Grenoble, France
| | - Koen Vandewal
- Institute for Materials Research (IMO-IMOMEC), Hasselt University, Wetenschapspark 1, 3590 Diepenbeek, Belgium.
| | - David Beljonne
- Laboratory for Chemistry of Novel Materials, University of Mons, B-7000 Mons, Belgium.
| | - Donato Spoltore
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, 01187 Dresden, Germany
- Institute for Materials Research (IMO-IMOMEC), Hasselt University, Wetenschapspark 1, 3590 Diepenbeek, Belgium.
- Department of Mathematical, Physical and Computer Sciences, University of Parma, V.le delle Scienze 7/A, 43124 Parma, Italy.
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3
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Giebink NC, Forrest SR. Thermodynamic Limit for Excitonic Light-Emitting Diodes. PHYSICAL REVIEW LETTERS 2023; 130:267002. [PMID: 37450827 DOI: 10.1103/physrevlett.130.267002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Revised: 02/28/2023] [Accepted: 06/07/2023] [Indexed: 07/18/2023]
Abstract
We derive the thermodynamic limit for organic light-emitting diodes (OLEDs), and show that strong exciton binding in these devices requires a higher voltage to achieve the same luminance as a comparable inorganic LED. The OLED overpotential, which does not reduce the power conversion efficiency, is minimized by having a small exciton binding energy, a long exciton lifetime, and a large Langevin coefficient for electron-hole recombination. Based on these results, it seems likely that the best phosphorescent and thermally activated delayed fluorescence OLEDs reported to date approach their thermodynamic limit. The framework developed here is broadly applicable to other excitonic materials, and should therefore help guide the development of low voltage LEDs for display and solid-state lighting applications.
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Affiliation(s)
- Noel C Giebink
- Department of Electrical Engineering and Computer Science, and Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
- Department of Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Stephen R Forrest
- Department of Electrical Engineering and Computer Science, and Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
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4
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Cao HT, Hou PF, Yu WJ, Gao Y, Li B, Feng QY, Zhang H, Wang SS, Su ZM, Xie LH. Enhanced Efficiency of Exciplex Emission from a 9-Phenylfluorene Derivative. ACS APPLIED MATERIALS & INTERFACES 2023; 15:7236-7246. [PMID: 36700822 DOI: 10.1021/acsami.2c22266] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The exciplex-thermally activated delayed fluorescence (exciplex-TADF) system is an excellent candidate for the fabrication of high-efficiency organic light-emitting diodes (OLEDs) because of its more easily achieved small singlet-triplet energy splitting (ΔEST) and doping control. However, exciplex-TADF is still faced with the problems of low external quantum efficiency (ηext) and unclear effect of structure modification in electron acceptors. Herein, we provide a steric hindrance increase strategy to obtain high-efficiency exciplex emissions. Through introducing a 9-phenylfluorene group into N-ethylcarbazole of the dicyano-substituted 9-phenylfluorene, an electron acceptor material with increased steric hindrance is obtained, which helps the exciplex harvest a larger driving force and higher emission efficiencies. Encouragingly, the obtained OLED displays a maximum ηext of 25.8%, which is one of the best efficiency values among reported exciplex-OLEDs, simultaneously possessing excellent current efficiency of 83.6 cd A-1 and power efficiency of 93.7 lm W-1. It is expected that this work will offer a new avenue for designing electron acceptors for highly efficient exciplex emissions.
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Affiliation(s)
- Hong-Tao Cao
- Center for Molecular Systems and Organic Devices (CMSOD), State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing 210023, P.R. China
| | - Peng-Fei Hou
- Center for Molecular Systems and Organic Devices (CMSOD), State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing 210023, P.R. China
| | - Wen-Jing Yu
- Center for Molecular Systems and Organic Devices (CMSOD), State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing 210023, P.R. China
| | - Ying Gao
- Institute of Biomass Functional Materials Interdisciplinary Studies, Jilin Engineering Normal University, 3050 Kaixuan Road, Changchun 130052, P.R. China
| | - Bo Li
- Center for Molecular Systems and Organic Devices (CMSOD), State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing 210023, P.R. China
| | - Quan-You Feng
- Center for Molecular Systems and Organic Devices (CMSOD), State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing 210023, P.R. China
| | - He Zhang
- Center for Molecular Systems and Organic Devices (CMSOD), State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing 210023, P.R. China
| | - Sha-Sha Wang
- Center for Molecular Systems and Organic Devices (CMSOD), State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing 210023, P.R. China
| | - Zhong-Min Su
- College of Chemistry, Northeast Normal University, 5268 Renmin Street, Changchun 130024, P.R. China
| | - Ling-Hai Xie
- Center for Molecular Systems and Organic Devices (CMSOD), State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing 210023, P.R. China
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5
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Cao H, Hou P, Cao Q, Li Y, Wang S, Xie L. Exciplex Emission and Property Investigation Based on Cyano-substituted 9-Phenylfluorene Derivative. ACTA CHIMICA SINICA 2022. [DOI: 10.6023/a22070335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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6
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Wang X, Li Y, Wu Y, Qin K, Xu D, Wang D, Ma H, Ning S, Wu Z. A 2-phenylfuro[2,3- b]quinoxaline-triphenylamine-based emitter: photophysical properties and application in TADF-sensitized fluorescence OLEDs. NEW J CHEM 2022. [DOI: 10.1039/d2nj03508a] [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
We have demonstrated that the T1-state energy of a fluorescence dopant (FD) is close to that of the thermally activated delayed fluorescence (TADF)-type exciplex co-host, and the energy loss caused by the T1 states of the FD could be suppressed in TADF-sensitized fluorescence (TSF) OLEDs.
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Affiliation(s)
- XinYe Wang
- School of Chemistry, Xi’an JiaoTong University, Xi’an 710049, P. R. China
| | - YiXiang Li
- School of Chemistry, Xi’an JiaoTong University, Xi’an 710049, P. R. China
| | - Yuan Wu
- School of Electronic Information and Artificial Intelligence, Shaanxi University of Science and Technology Xi’an, Shaanxi, 710021, P. R. China
| | - Ke Qin
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Nanjing Tech University, Nanjing 211816, P. R. China
| | - DeFei Xu
- School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049, P. R. China
| | - DongDong Wang
- School of Chemistry, Xi’an JiaoTong University, Xi’an 710049, P. R. China
| | - HuiLi Ma
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Nanjing Tech University, Nanjing 211816, P. R. China
| | - ShuYa Ning
- School of Electronic Information and Artificial Intelligence, Shaanxi University of Science and Technology Xi’an, Shaanxi, 710021, P. R. China
| | - ZhaoXin Wu
- Key Laboratory for Physical Electronics and Devices of the Ministry of Education & Shaanxi Key Lab of Information Photonic Technique, School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049, P. R. China
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7
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Song Y, Tian M, Yu R, He L. Through-Space Charge-Transfer Emitters Developed by Fixing the Acceptor for High-Efficiency Thermally Activated Delayed Fluorescence. ACS APPLIED MATERIALS & INTERFACES 2021; 13:60269-60278. [PMID: 34881866 DOI: 10.1021/acsami.1c17707] [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
Through-space charge-transfer (TSCT) emitters have been extensively explored for thermally activated delayed fluorescence (TADF), but arranging various donors and acceptors into rigid cofacial conformations for various efficient TSCT TADF emitters has remained challenging. Here, we report a "fixing acceptor" design to reach various efficient TSCT TADF emitters. By chemically fixing the acceptor (benzophenone) with a rigid spiro-structure and cofacially aligning various donors with the fixed acceptor, a series of efficient TSCT TADF emitters have been developed. Single-crystal structures and theoretical calculations have verified closely packed cofacial donor/acceptor conformations and favorable TSCT in the emitters. In doped films, the emitters afford sky blue to yellow TADF emission, with high photoluminescence efficiencies up to 0.92 and reverse intersystem crossing rates up to 1.0 × 106 s-1. Organic light-emitting diodes using the emitters afford sky blue to yellow electroluminescence with high external quantum efficiencies up to 20.9%. The work opens a new avenue toward a wide variety of efficient TSCT TADF emitters.
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Affiliation(s)
- Yongjun Song
- Key Laboratory of Pesticide and Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, College of Chemistry, Central China Normal University, Wuhan 430079, People's Republic of China
| | - Mingxing Tian
- Key Laboratory of Pesticide and Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, College of Chemistry, Central China Normal University, Wuhan 430079, People's Republic of China
| | - Renyou Yu
- Key Laboratory of Pesticide and Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, College of Chemistry, Central China Normal University, Wuhan 430079, People's Republic of China
| | - Lei He
- Key Laboratory of Pesticide and Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, College of Chemistry, Central China Normal University, Wuhan 430079, People's Republic of China
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8
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Wang J, Liang B, Wei J, Li Z, Xu Y, Yang T, Li C, Wang Y. Highly Efficient Electrofluorescence Material Based on Pure Organic Phosphor Sensitization**. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202104755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Jiaxuan Wang
- State Key Laboratory of Supramolecular Structure and Materials College of Chemistry Jilin University Changchun 130012 P. R. China
| | - Baoyan Liang
- Jihua Laboratory 28 Huandao South Road Foshan 528200 Guangdong Province P. R. China
| | - Jinbei Wei
- State Key Laboratory of Supramolecular Structure and Materials College of Chemistry Jilin University Changchun 130012 P. R. China
| | - Zhiqiang Li
- Jihua Laboratory 28 Huandao South Road Foshan 528200 Guangdong Province P. R. China
| | - Yincai Xu
- State Key Laboratory of Supramolecular Structure and Materials College of Chemistry Jilin University Changchun 130012 P. R. China
| | - Tong Yang
- State Key Laboratory of Supramolecular Structure and Materials College of Chemistry Jilin University Changchun 130012 P. R. China
| | - Chenglong Li
- State Key Laboratory of Supramolecular Structure and Materials College of Chemistry Jilin University Changchun 130012 P. R. China
| | - Yue Wang
- State Key Laboratory of Supramolecular Structure and Materials College of Chemistry Jilin University Changchun 130012 P. R. China
- Jihua Laboratory 28 Huandao South Road Foshan 528200 Guangdong Province P. R. China
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9
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Wang J, Liang B, Wei J, Li Z, Xu Y, Yang T, Li C, Wang Y. Highly Efficient Electrofluorescence Material Based on Pure Organic Phosphor Sensitization*. Angew Chem Int Ed Engl 2021; 60:15335-15339. [PMID: 33904242 DOI: 10.1002/anie.202104755] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Indexed: 11/07/2022]
Abstract
Pure organic room-temperature phosphorescence (RTP) materials are considered as potential candidates for replacing precious metal complexes to fabricate highly efficient organic light-emitting devices (OLEDs). However, applications of the reported RTP materials in OLEDs are seriously impeded by their low photoluminescence quantum yields (PLQYs) in a thin film state. To overcome these obstacles, we established a new strategy to construct highly efficient OLEDs based on a pure organic RTP material sensitized fluorescence emitter by selecting benzimidazole-triazine molecules (PIM-TRZ), 2,6-di(phenothiazinyl)naphthalene (β-DPTZN), and 5,6,11,12-tetraphenylnaphthacene (rubrene) as host, phosphor sensitizer, and fluorescent emitter, respectively. The perfect combination of host, phosphorescent sensitizer, and fluorescent emitter in the emitting layer ensure the outstanding performance of the devices with an external quantum efficiency (EQE) of 15.7 %.
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Affiliation(s)
- Jiaxuan Wang
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Baoyan Liang
- Jihua Laboratory, 28 Huandao South Road, Foshan, 528200, Guangdong Province, P. R. China
| | - Jinbei Wei
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Zhiqiang Li
- Jihua Laboratory, 28 Huandao South Road, Foshan, 528200, Guangdong Province, P. R. China
| | - Yincai Xu
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Tong Yang
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Chenglong Li
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Yue Wang
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, P. R. China.,Jihua Laboratory, 28 Huandao South Road, Foshan, 528200, Guangdong Province, P. R. China
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10
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He L, Bai R, Yu R, Meng X, Tian M, Wang X. Donor/Acceptor Pairs Created by Electrostatic Interaction: Design, Synthesis, and Investigation on the Exciplex Formed Within the Pair. Angew Chem Int Ed Engl 2021; 60:6013-6020. [PMID: 33331060 DOI: 10.1002/anie.202013332] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 12/11/2020] [Indexed: 12/23/2022]
Abstract
Exciplexes formed between donors and acceptors have been widely explored but isolating them from each other and tuning the interaction between the donor and acceptor have remained challenges. Here, we report donor/acceptor (D/A) pairs created by electrostatic interaction between a carbazole-based anionic donor and a 1,3,5-triazine-based cationic acceptor and the exciplex formed within the pair. In a diluted film, the D/A pair affords an isolated exciplex which shows thermally activated delayed fluorescence (TADF). By changing the anchoring position of the imidazolium cation in the cationic acceptor, interactions between the donor and acceptor can be changed. Compared to the conventional exciplex formed in a neat film, the isolated exciplex exhibits a substantially higher luminescence efficiency. The D/A pairs show intriguing mechanochromic luminescence and mechanical grinding-induced/reinforced TADF in the solid state and promising performances as emitters in organic light-emitting diodes.
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Affiliation(s)
- Lei He
- Key Laboratory of Pesticide and Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, College of Chemistry, Central China Normal University, Wuhan, 430079, P. R. China
| | - Rubing Bai
- Key Laboratory of Pesticide and Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, College of Chemistry, Central China Normal University, Wuhan, 430079, P. R. China
| | - Renyou Yu
- Key Laboratory of Pesticide and Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, College of Chemistry, Central China Normal University, Wuhan, 430079, P. R. China
| | - Xianwen Meng
- Key Laboratory of Pesticide and Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, College of Chemistry, Central China Normal University, Wuhan, 430079, P. R. China
| | - Mingxing Tian
- Key Laboratory of Pesticide and Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, College of Chemistry, Central China Normal University, Wuhan, 430079, P. R. China
| | - Xiaoxiang Wang
- Key Laboratory of Pesticide and Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, College of Chemistry, Central China Normal University, Wuhan, 430079, P. R. China
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11
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Zhang M, Zheng CJ, Lin H, Tao SL. Thermally activated delayed fluorescence exciplex emitters for high-performance organic light-emitting diodes. MATERIALS HORIZONS 2021; 8:401-425. [PMID: 34821262 DOI: 10.1039/d0mh01245a] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Owing to their natural thermally activated delayed fluorescence (TADF) characteristics, the development of exciplex emitters for organic light-emitting diodes (OLEDs) has witnessed booming progress in recent years. Formed between electron-donating and electron-accepting molecules, exciplexes with intermolecular charge transfer processes have unique advantages compared with unimolecular TADF materials, offering a new way to develop high-performance TADF emitters. In this review, a comprehensive overview of TADF exciplex emitters is presented with a focus on the relationship between the constituents of exciplexes and their electroluminescence performance. We summarize and discuss the latest and most significant developments of TADF exciplex emitters. Notably, the design principles of efficient TADF exciplex emitters are systematically categorized into three systems within this review. These progressive achievements of TADF exciplex emitters point out future challenges to trigger more research endeavors in this growing field.
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Affiliation(s)
- Ming Zhang
- School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China (UESTC), Chengdu, 610054, P. R. China.
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12
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He L, Bai R, Yu R, Meng X, Tian M, Wang X. Donor/Acceptor Pairs Created by Electrostatic Interaction: Design, Synthesis, and Investigation on the Exciplex Formed Within the Pair. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202013332] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Lei He
- Key Laboratory of Pesticide and Chemical Biology of Ministry of Education Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis College of Chemistry Central China Normal University Wuhan 430079 P. R. China
| | - Rubing Bai
- Key Laboratory of Pesticide and Chemical Biology of Ministry of Education Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis College of Chemistry Central China Normal University Wuhan 430079 P. R. China
| | - Renyou Yu
- Key Laboratory of Pesticide and Chemical Biology of Ministry of Education Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis College of Chemistry Central China Normal University Wuhan 430079 P. R. China
| | - Xianwen Meng
- Key Laboratory of Pesticide and Chemical Biology of Ministry of Education Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis College of Chemistry Central China Normal University Wuhan 430079 P. R. China
| | - Mingxing Tian
- Key Laboratory of Pesticide and Chemical Biology of Ministry of Education Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis College of Chemistry Central China Normal University Wuhan 430079 P. R. China
| | - Xiaoxiang Wang
- Key Laboratory of Pesticide and Chemical Biology of Ministry of Education Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis College of Chemistry Central China Normal University Wuhan 430079 P. R. China
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13
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Liang B, Yu Z, Zhuang X, Wang J, Wei J, Ye K, Zhang Z, Liu Y, Wang Y. Achieving High-Performance Pure-Red Electrophosphorescent Iridium(III) Complexes Based on Optimizing Ancillary Ligands. Chemistry 2020; 26:4410-4418. [PMID: 32017269 DOI: 10.1002/chem.201905690] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 02/02/2020] [Indexed: 11/07/2022]
Abstract
Two new iridium(III) complexes were synthesized by introducing two trifluoromethyl groups into an ancillary ligand to develop pure-red emitters for organic light-emitting diodes (OLEDs). The electron-donating ability of the ancillary ligands is suppressed, owing to the electron-withdrawing nature of trifluoromethyl groups, which can reduce the HOMO energy levels compared with those of compounds without trifluoromethyl groups. However, the introduction of trifluoromethyl groups into the ancillary ligand has little impact on the LUMO energy levels. Therefore, a well-tuned, pure-red, excited-state energy was achieved by regulating the relative energy level between the HOMO and LUMO. OLEDs with these complexes as emitters showed high external quantum efficiencies (EQEs) of 26 % and realized high EQEs of about 25 % and fairly low driving voltages of 3.3-3.6 V for practical luminance of 1000 cd m-2 , as well as excellent Commission Internationale de L'Eclairage (CIE) coordinates of (0.66, 0.33) and (0.67, 0.33); thus, this demonstrates the successful molecular design strategy by modifying the electron-donating ability of ancillary ligand.
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Affiliation(s)
- Baoyan Liang
- State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun, 130012, P.R. China
| | - Zhanshuang Yu
- State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun, 130012, P.R. China
| | - Xuming Zhuang
- State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun, 130012, P.R. China
| | - Jiaxuan Wang
- State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun, 130012, P.R. China
| | - Jinbei Wei
- State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun, 130012, P.R. China
| | - Kaiqi Ye
- State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun, 130012, P.R. China
| | - Zuolun Zhang
- State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun, 130012, P.R. China
| | - Yu Liu
- State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun, 130012, P.R. China
| | - Yue Wang
- State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun, 130012, P.R. China
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Wang M, Huang YH, Lin KS, Yeh TH, Duan J, Ko TY, Liu SW, Wong KT, Hu B. Revealing the Cooperative Relationship between Spin, Energy, and Polarization Parameters toward Developing High-Efficiency Exciplex Light-Emitting Diodes. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1904114. [PMID: 31566271 DOI: 10.1002/adma.201904114] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 09/06/2019] [Indexed: 06/10/2023]
Abstract
Experimental studies to reveal the cooperative relationship between spin, energy, and polarization through intermolecular charge-transfer dipoles to harvest nonradiative triplets into radiative singlets in exciplex light-emitting diodes are reported. Magneto-photoluminescence studies reveal that the triplet-to-singlet conversion in exciplexes involves an artificially generated spin-orbital coupling (SOC). The photoinduced electron parametric resonance measurements indicate that the intermolecular charge-transfer occurs with forming electric dipoles (D+• →A-• ), providing the ionic polarization to generate SOC in exciplexes. By having different singlet-triplet energy differences (ΔEST ) in 9,9'-diphenyl-9H,9'H-3,3'-bicarbazole (BCzPh):3',3'″,3'″″-(1,3,5-triazine-2,4,6-triyl)tris(([1,1'-biphenyl]-3-carbonitrile)) (CN-T2T) (ΔEST = 30 meV) and BCzPh:bis-4,6-(3,5-di-3-pyridylphenyl)-2-methyl-pyrimidine (B3PYMPM) (ΔEST = 130 meV) exciplexes, the SOC generated by the intermolecular charge-transfer states shows large and small values (reflected by different internal magnetic parameters: 274 vs 17 mT) with high and low external quantum efficiency maximum, EQEmax (21.05% vs 4.89%), respectively. To further explore the cooperative relationship of spin, energy, and polarization parameters, different photoluminescence wavelengths are selected to concurrently change SOC, ΔEST , and polarization while monitoring delayed fluorescence. When the electron clouds become more deformed at a longer emitting wavelength due to reduced dipole (D+• →A-• ) size, enhanced SOC, increased orbital polarization, and decreased ΔEST can simultaneously occur to cooperatively operate the triplet-to-singlet conversion.
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Affiliation(s)
- Miaosheng Wang
- Joint Institute for Advanced Materials, Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN, 37996, USA
| | - Yi-Hsuan Huang
- Department of Chemistry, National Taiwan University, and Institute of Atomic and Molecular Science, Academia Sinica, Taipei, 10617, Taiwan
| | - Kai-Siang Lin
- Department of Electronic Engineering, Ming Chi University of Technology, New Taipei City, 24301, Taiwan
- Organic Electronics Research Center, Ming Chi University of Technology, New Taipei City, 24301, Taiwan
| | - Tzu-Hung Yeh
- Organic Electronics Research Center, Ming Chi University of Technology, New Taipei City, 24301, Taiwan
| | - Jiashun Duan
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, China
| | - Tzu-Yu Ko
- Department of Chemistry, National Taiwan University, and Institute of Atomic and Molecular Science, Academia Sinica, Taipei, 10617, Taiwan
| | - Shun-Wei Liu
- Department of Electronic Engineering, Ming Chi University of Technology, New Taipei City, 24301, Taiwan
- Organic Electronics Research Center, Ming Chi University of Technology, New Taipei City, 24301, Taiwan
| | - Ken-Tsung Wong
- Department of Chemistry, National Taiwan University, and Institute of Atomic and Molecular Science, Academia Sinica, Taipei, 10617, Taiwan
| | - Bin Hu
- Joint Institute for Advanced Materials, Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN, 37996, USA
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Wang J, Liang J, Xu Y, Liang B, Wei J, Li C, Mu X, Ye K, Wang Y. Purely Organic Phosphorescence Emitter-Based Efficient Electroluminescence Devices. J Phys Chem Lett 2019; 10:5983-5988. [PMID: 31537062 DOI: 10.1021/acs.jpclett.9b02513] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
A pure organic molecule 2,6-di(phenothiazinyl)naphthalene (DPTZN) with room-temperature phosphorescence (RTP) features was developed. Remarkably, a triazine-benzimidazole-based molecule TRZ-BIM can significantly improve the RTP efficiency of DPTZN in DPTZN:TRZ-BIM blend films. The photoluminescence quantum yield (PLQY) of 10 wt % DPTZN:TRZ-BIM blend film is 38%. The RTP property of DPTZN:TRZ-BIM blend films was characterized by steady, time-resolved, and temperature-dependent emission spectra. An organic light-emitting diode (OLED) with 10 wt % DPTZN:TRZ-BIM blend film as the emitting layer showed a high maximum external quantum efficiency of 11.5%, current efficiency of 33.8 cd A-1, and power efficiency of 32.6 lm W-1. Herein, we have developed an efficient approach to achieve precious-metal-free organic films that can be employed to fabricate high-performance phosphorescence OLEDs.
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Affiliation(s)
- Jiaxuan Wang
- State Key Laboratory of Supramolecular Structure and Materials , Jilin University , Changchun 130012 , P.R. China
| | - Jixiong Liang
- State Key Laboratory of Supramolecular Structure and Materials , Jilin University , Changchun 130012 , P.R. China
| | - Yincai Xu
- State Key Laboratory of Supramolecular Structure and Materials , Jilin University , Changchun 130012 , P.R. China
| | - Baoyan Liang
- State Key Laboratory of Supramolecular Structure and Materials , Jilin University , Changchun 130012 , P.R. China
| | - Jinbei Wei
- State Key Laboratory of Supramolecular Structure and Materials , Jilin University , Changchun 130012 , P.R. China
| | - Chenglong Li
- State Key Laboratory of Supramolecular Structure and Materials , Jilin University , Changchun 130012 , P.R. China
| | - Xiaoyue Mu
- State Key Laboratory of Supramolecular Structure and Materials , Jilin University , Changchun 130012 , P.R. China
| | - Kaiqi Ye
- State Key Laboratory of Supramolecular Structure and Materials , Jilin University , Changchun 130012 , P.R. China
| | - Yue Wang
- State Key Laboratory of Supramolecular Structure and Materials , Jilin University , Changchun 130012 , P.R. China
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