High-efficiency phosphorescent organic light-emitting devices with low efficiency roll-off using a thermally activated delayed fluorescence material as host |
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| Affiliation: | 1. State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054, PR China;2. School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou, PR China;1. School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054, PR China;2. Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou, Jiangsu 215123, PR China;1. Department of Green Energy & Semiconductor Engineering, Hoseo University, Asan, Republic of Korea;2. Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4L7, Canada;1. Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, PR China;2. Shaanxi Institute of Flexible Electronics (SIFE), Northwestern Polytechnical University (NPU), 127 West Youyi Road, Xi''an 710072, PR China;1. Department of Applied Chemistry, 744 Motooka, Nishi, Fukuoka 819-0395, Japan;2. Center for Organic Photonics and Electronics Research, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan;3. Institute of Applied Research, Vilnius University, Saul?tekio 9-III, LT-10222 Vilnius, Lithuania;4. Japan Science and Technology Agency (JST), ERATO, Adachi Molecular Exciton Engineering Project, 744 Motooka, Nishi, Fukuoka 819-0395, Japan;5. International Institute for Carbon Neutral Energy Research, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan |
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| Abstract: | Phosphorescent organic light-emitting devices (PHOLEDs) with high efficiency and low efficiency roll-off were fabricated. The emissive layer was composed of a thermally activated delayed fluorescence (TADF) material 4,5-bis(carbazol-9-yl)-1,2-dicyanobenzene (2CzPN) as host and an orange iridium complex bis(4-tert-butyl-2-phenylbenzothiozolato-N,C2′)iridium(III)(acetylacetonate) (tbt)2Ir(acac)] as dopant. At a low dopant concentration of 1 wt%, a PHOLED without light extraction optimization achieved a maximum power efficiency of 42.1 lm/W, a luminance efficiency of 77.9 cd/A and an external quantum efficiency (EQE) of 26.8%, respectively. Meanwhile, the EQE maintained 26.6% at 1000 cd/m2 and 25.8% at 5000 cd/m2, respectively. Moreover, a critical current density of 300 mA/cm2 was realized, indicating significantly improved efficiency roll-off. The efficient utilization of triplet excitons on 2CzPN for phosphorescence via reverse inter-system crossing of 2CzPN followed by F?rster resonance energy transfer from 2CzPN to (tbt)2Ir(acac) is responsible for the superior performance. |
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| Keywords: | Organic light-emitting device Thermally activated delayed fluorescence host Orange phosphor Low efficiency roll-off |
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