系统间交叉
电致发光
激发态
有机发光二极管
单重态
材料科学
量子产额
光致发光
量子效率
光电子学
物理
荧光
原子物理学
光学
纳米技术
图层(电子)
作者
Donghai Zhang,Shanshan Jiang,Xiaodong Tao,Fulin Lin,Lingyi Meng,Xulin Chen,Can‐Zhong Lu
出处
期刊:Research
[AAAS00]
日期:2023-01-01
卷期号:6
被引量:3
标识
DOI:10.34133/research.0155
摘要
Thermally activated delayed fluorescence (TADF) materials with both high photoluminescence quantum yield (PLQY) and fast reverse intersystem crossing (RISC) are strongly desired to realize efficient and stable organic light-emitting diodes (OLEDs). Control of excited-state dynamics via molecular design plays a central role in optimizing the PLQY and RISC rate of TADF materials but remains challenging. Here, 3 TADF emitters possessing similar molecular structures, similar high PLQYs (89.5% to 96.3%), and approximate energy levels of the lowest excited singlet states (S 1 ), but significantly different spin-flipping RISC rates (0.03 × 10 6 s −1 vs. 2.26 × 10 6 s −1 ) and exciton lifetime (297.1 to 332.8 μs vs. 6.0 μs) were systematically synthesized to deeply investigate the feasibility of spin-flip between charge-transfer excited states ( 3 CT– 1 CT) transition. Experimental and theoretical studies reveal that the small singlet–triplet energy gap together with low RISC reorganization energy between the 3 CT and 1 CT states could provide an efficient RISC through fast spin-flip 3 CT– 1 CT transition, without the participation of an intermediate locally excited state, which has previously been recognized as being necessary for realizing fast RISC. Finally, the OLED based on the champion TADF emitter achieves a maximum external quantum efficiency of 27.1%, a tiny efficiency roll-off of 4.1% at 1,000 cd/m 2 , and a high luminance of 28,150 cd/m 2 , which are markedly superior to those of the OLEDs employing the other 2 TADF emitters.
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