摘要
目前,商用的深蓝有机发光二极管(OLED)使用的三重态-三重态融合(TTF)型发光材料只能捕获50%的三重态(T_(1))激子,导致其器件效率较低.基于窄带蓝色发射体的热激活延迟荧光(TADF)和超荧光策略可以实现接近100%的激子利用率,然而,在发射层(EML)中停留的高能量T_(1)激子通常会导致不可避免的分子降解,从而限制了器件的使用寿命.为了解决这一问题,本文研究了一种TTF-杂化局域-电荷转移态(HLCT)一体化分子,旨在通过多个激子回收通道降低EML内T_(1)激子的密度,从而提高高效深蓝OLED的稳定性.通过TTF过程回收T_(1)激子,通过HLCT过程利用高能三重态(Tn)激子,可以提高EML中三重态激子的利用率.此外,低浓度掺杂的TTF-HLCT分子在TADF体系中可以减轻T_(1)激子猝灭造成的效率损失.最后,实现了外量子效率(EQE)为25.9%、CIE为(0.131,0.050)、蓝光指数(CE由CIEy校准)为312 cd A^(−1) CIE_(y)^(−1)的顶发射OLED,并且其寿命T90@1000 cd m^(−2)从0.5小时延长到6.1小时.本工作揭示了低浓度TTF-HLCT分子掺杂的潜力,作为一种可行的解决方案,可以最大限度地减少效率猝灭,并解决蓝光OLED的稳定性问题.
Currently,commercial deep blue organic lightemitting diodes(OLEDs)using triplet-triplet fusion(TTF)type emitting materials can only capture 50%of triplet(T_(1))excitons,resulting in poor device efficiency.The utilization of nearly 100%excitons can be achieved by thermally activated delayed fluorescence(TADF)and hyperfluorescence strategy with narrowband blue emitters.However,the presence of high-energy T_(1) excitons in the emitting layer(EML)typically results in inevitable molecule degradation,thereby limiting the device’s lifetime.To address this issue,a TTF-hybridized local and charge transfer(HLCT)combinational molecule is investigated in this work,aiming to enhance the stability of highly efficient deep blue OLED by reducing the density of T_(1) excitons within EML through multiple exciton recycling channels.The utilization ratio of triplet excitons in EML can be enhanced by recycling T_(1) excitons through the TTF process and high energy triplet(Tn)excitons through the HLCT process.Moreover,the low doping concentration of the TTFHLCT molecule in the TADF system can mitigate the efficiency loss caused by the quenching of T_(1) excitons.Finally,a top-emitting OLED with an external quantum efficiency of 25.9%,Commission Internationale de l´Eclairage(CIE)of(0.131,0.050),and blue index of 312 cd A^(−1) CIE_(y)^(−1) are realized.Besides,the lifetime T90@1000 cd m^(−2)has been extended from 0.5 to 6.1 h.This work suggests the potential of the low doping concentration of a TTF-HLCT combinational molecule as a viable solution to address the stability issues encountered in deep blue OLEDs.
作者
唐振宇
龚乐帆
郭浩清
杨爽
罗骏
唐荣
肖静
张震
曲波
陈志坚
肖立新
Zhenyu Tang;Lefan Gong;Haoqing Guo;Shuang Yang;Jun Luo;Rong Tang;Jing Xiao;Zhen Zhang;Bo Qu;Zhijian Chen;Lixin Xiao(State Key Laboratory of Artificial Microstructure and Mesoscopic Physics,School of Physics,Peking University,Beijing 100871,China;College of Physics and Electronic Engineering,Taishan University,Taian 271000,China;Key Laboratory of Advanced Display and System Applications,Ministry of Education,Shanghai University,Shanghai 200072,China)
基金
supported by the National Key Research and Development Program of China(2022YFE0109000)
the National Natural Science Foundation of China(62374112)
the Natural Science Foundation of Shandong Province(ZR2002MF271).
