Organic Electronics ( IF 2.7 ) Pub Date : 2021-01-30 , DOI: 10.1016/j.orgel.2021.106076
Zhuobin Li , JunshengYu , Xiaoqing Liao , Lu Li
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Improvement of the utilization of triplet excitons for thermally activated delayed fluorescence (TADF) emitter-based white organic light emitting devices (WOLEDs) is a key scientific challenge. In this study, a new strategy with stepped reverse intersystem crossing (RISC) channels induced by new ternary exciplex was proposed to enhance up-conversion of non-radiative triplet excitons. A flexible TADF WOLED with external quantum efficiency (EQE) of 22.7% and a power efficiency of 62.5 lmW−1 was demonstrated. At 1000 cdm−2, the EQE still remained at 21.4%, showing low efficiency roll-off of 5.7%. It is attributed to the reduced non-radiative triplet excitons stack, which suppressed the triplet–triplet quenching. Moreover, the new ternary exciplex-based WOLED system mCP: DMAC-DPS:PO-T2T:4CZPNPh exhibited rate constant of RISC process of 2.5 × 106 s−1, and about 2 times photoluminescence quantum yield over binary exciplex. The high efficiency effectively demonstrated that the proposed multiple triplet excitons capture process is an effective strategy to improve the utilization of triplet excitons. Moreover, the novel strategy can be a promising approach for the further development of WOLED.
中文翻译:
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通过三元激基复合物的阶梯状反向系统间交叉通道,具有超过22%EQE的柔性全荧光白有机发光器件
对于基于热活化延迟荧光(TADF)发射体的白色有机发光器件(WOLED),提高三重态激子的利用率是一项关键的科学挑战。在这项研究中,提出了一种由新的三元激基复合物诱导的带有逐步反向系统间交叉(RISC)通道的新策略,以增强非辐射三重态激子的上转换。展示了一种柔性TADF WOLED,其外部量子效率(EQE)为22.7%,功率效率为62.5 lmW -1。在1000 cdm -2时,EQE仍保持在21.4%,显示低效率下降了5.7%。这归因于非辐射三重态激子堆叠的减少,抑制了三重态-三重态猝灭。此外,基于三元激基复合物的新型WOLED系统mCP:DMAC-DPS:PO-T2T:4CZPNPh的RISC过程的速率常数为2.5×10 6 s -1,是二元激基复合物的2倍。高效有效地证明了所提出的多重三重态激子捕获过程是提高三重态激子利用率的有效策略。此外,新颖的策略可能是WOLED进一步发展的有前途的方法。