Enhanced Operational Durability of Thermally Activated Delayed Fluorescence-Based Organic Light-Emitting Diodes with a Triazine Electron Transporter |
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Authors: | Kenta Yamaguchi Dr Toshinori Matsushima Dr Atula S D Sandanayaka Yoko Homma Naoki Uchida Prof Chihaya Adachi |
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Institution: | 1. Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka, 819-0395 Japan
Japan Science and Technology Agency (JST), ERATO, Adachi Molecular Exciton Engineering Project, Kyushu University, 744 Motooka, Nishi, Fukuoka, 819-0395 Japan;2. Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka, 819-0395 Japan;3. Tokyo Research Center, Organic Materials Research Laboratory, Tosoh Corporation, 2743-1, Hayakawa, Ayase, Kanagawa, 252-1123 Japan |
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Abstract: | In organic light-emitting diodes (OLEDs) based on materials that show thermally activated delayed fluorescence (TADF), the internal quantum efficiency of 100 % can be obtained without using phosphorescence-based organometallics that contain rare metals. Therefore, with TADF-based emitters, it is possible to fabricate high-performing OLEDs at a lower cost. However, compared with fluorescence- and phosphorescence-based OLEDs, an understanding of degradation mechanisms in TADF-based OLEDs is still insufficient for future commercialization. In particular, it is widely recognized that the development of electron transport materials is crucial for improving OLED characteristics, especially driving voltages and operational durability. In this study, it was demonstrated that the operational durability of TADF-based OLEDs was greatly improved by introducing a triazine-based material of 2,4,6-tris(1,1′-biphenyl-4-yl)-1,3,5]triazine (pT2T) as a hole-blocking layer (HBL) compared with a conventional HBL material of 2,4,6-tris(biphenyl-3-yl)-1,3,5]triazine (T2T). Several experiments were carried out to make the reasons of the improved durability clearer, and attributed the improved durability to the shift of a carrier recombination zone from the emitting layer/HBL interface and the suppressed formation of excited-state quenchers in the pT2T HBL, because of the higher electron mobility of pT2T and the better stability of its radical anion state. |
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Keywords: | degradation mechanism electron transporters operational durability organic light-emitting diodes triazine |
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