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Goto D, Mori H. Avoiding Photocyclized Degradation of Electrochromic Materials Based on Quantum Chemical Molecular Design. J Phys Chem Lett 2024; 15:8205-8210. [PMID: 39102584 DOI: 10.1021/acs.jpclett.4c01783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/07/2024]
Abstract
Suppressing the photodegradation of organic electronic materials is crucial for their device applications. This study proposes a method to mitigate the photodegradation. With focus on the molecular design of triphenylamine derivatives commonly used in organic electronics, it was demonstrated that spin distributions of the derivatives would be a good quantum descriptor for predicting the photocyclization resistance to not give carbazole derivatives.
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Affiliation(s)
- Daisuke Goto
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, Tokyo 112-8551, Japan
- Advanced Technology Research and Development Division, Ricoh Company, Limited, Ebina, Kanagawa 243-0460, Japan
| | - Hirotoshi Mori
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, Tokyo 112-8551, Japan
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Yumoto S, Katsumata J, Osawa F, Wada Y, Suzuki K, Kaji H, Marumoto K. Operando ESR observation in thermally activated delayed fluorescent organic light-emitting diodes. Sci Rep 2023; 13:11109. [PMID: 37429886 DOI: 10.1038/s41598-023-38063-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Accepted: 07/02/2023] [Indexed: 07/12/2023] Open
Abstract
Organic light-emitting diodes (OLEDs) using thermally activated delayed fluorescence (TADF) materials have advantages over OLEDs using conventional fluorescent materials or high-cost phosphorescent materials, including higher efficiency and lower cost. To attain further high device performance, clarifying internal charge states in OLEDs at a microscopic viewpoint is crucial; however, only a few such studies have been performed. Here, we report a microscopic investigation into internal charge states in OLEDs with a TADF material by electron spin resonance (ESR) at a molecular level. We observed operando ESR signals of the OLEDs and identified their origins due to a hole-transport material PEDOT:PSS, gap states at an electron-injection layer, and a host material CBP in the light-emitting layer by performing density functional theory calculation and studying thin films used in the OLEDs. The ESR intensity varied with increasing applied bias before and after the light emission. We find leakage electrons in the OLED at a molecular level, which is suppressed by a further electron-blocking layer MoO3 between the PEDOT:PSS and light-emitting layer, resulting in the enhancement of luminance with a low-voltage drive. Such microscopic information and applying our method to other OLEDs will further improve the OLED performance from the microscopic viewpoint.
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Affiliation(s)
- Shintaro Yumoto
- Department of Materials Science, Institute of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8573, Japan
| | - Junya Katsumata
- Department of Materials Science, Institute of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8573, Japan
| | - Fumiya Osawa
- Department of Materials Science, Institute of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8573, Japan
| | - Yoshimasa Wada
- Institute for Chemical Research, Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Katsuaki Suzuki
- Institute for Chemical Research, Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Hironori Kaji
- Institute for Chemical Research, Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Kazuhiro Marumoto
- Department of Materials Science, Institute of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8573, Japan.
- Tsukuba Research Center for Energy Materials Science (TREMS), University of Tsukuba, Ibaraki, 305-8571, Japan.
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Wu Y, Zhu Y, Zhang Z, Zhao C, He J, Yan C, Meng H. Narrowband Deep-Blue Multi-Resonance Induced Thermally Activated Delayed Fluorescence: Insights from the Theoretical Molecular Design. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27020348. [PMID: 35056667 PMCID: PMC8780697 DOI: 10.3390/molecules27020348] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 01/02/2022] [Accepted: 01/06/2022] [Indexed: 11/16/2022]
Abstract
Multi-resonance thermal activated delayed fluorescence (MR-TADF) has been promising with large oscillator strength and narrow full width at half maxima of luminescence, overcoming the compromise of emission intensity and energy criteria of traditional charge transfer TADF frameworks. However, there are still limited theoretical investigations on the excitation mechanism and systematic molecular manipulation of MR-TADF structures. We systematically study the highly localized excitation (LE) characteristics based on typical blue boron-nitrogen (BN) MR-TADF emitters and prove the potential triangular core with theoretical approaches. A design strategy by extending the planar π-conjugate core structure is proposed to enhance the multiple resonance effects. Moreover, several substituted groups are introduced to the designed core, achieving color-tunable functions with relatively small energy split and strong oscillator strength simultaneously. This work provides a theoretical direction for molecular design strategy and a series of potential candidates for highly efficient BN MR-TADF emitters.
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Affiliation(s)
- Yuting Wu
- School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China; (Y.W.); (Y.Z.); (Z.Z.); (C.Z.); (J.H.); (C.Y.)
| | - Yanan Zhu
- School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China; (Y.W.); (Y.Z.); (Z.Z.); (C.Z.); (J.H.); (C.Y.)
| | - Zewei Zhang
- School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China; (Y.W.); (Y.Z.); (Z.Z.); (C.Z.); (J.H.); (C.Y.)
| | - Chongguang Zhao
- School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China; (Y.W.); (Y.Z.); (Z.Z.); (C.Z.); (J.H.); (C.Y.)
- State High-Tech Industrial Innovation Center, Shenzhen 518057, China
| | - Junpeng He
- School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China; (Y.W.); (Y.Z.); (Z.Z.); (C.Z.); (J.H.); (C.Y.)
| | - Chaoyi Yan
- School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China; (Y.W.); (Y.Z.); (Z.Z.); (C.Z.); (J.H.); (C.Y.)
| | - Hong Meng
- School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China; (Y.W.); (Y.Z.); (Z.Z.); (C.Z.); (J.H.); (C.Y.)
- Correspondence:
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