Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, China.
Center for Flexible Electronics Technology, Tsinghua University, Beijing, 100084, P. R. China.
Adv Mater. 2018 Feb;30(6). doi: 10.1002/adma.201705250. Epub 2017 Dec 27.
Organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence-sensitized fluorescence (TSF) offer the possibility of attaining an ultimate high efficiency with low roll-off utilizing noble-metal free, easy-to-synthesize, pure organic fluorescent emitters. However, the performances of TSF-OLEDs are still unsatisfactory. Here, TSF-OLEDs with breakthrough efficiencies even at high brightnesses by suppressing the competitive deactivation processes, including direct charge recombination on conventional fluorescent dopants (CFDs) and Dexter energy transfer from the host to the CFDs, are demonstrated. On the one hand, electronically inert terminal-substituents are introduced to protect the electronically active core of the CFDs; on the other hand, delicate device structures are designed to provide multiple energy-funneling paths. As a result, unprecedentedly high maximum external quantum efficiency/power efficiency of 24%/71.4 lm W in a green TSF-OLED are demonstrated, which remain at 22.6%/52.3 lm W even at a high luminance of 5000 cd m . The work unlocks the potential of TSF-OLEDs, paving the way toward practical applications.
基于热激活延迟荧光敏化荧光（TSF）的有机发光二极管（OLED）利用无贵金属、易于合成的纯有机荧光发射器，有可能实现高效率和低滚降。然而，TSF-OLED 的性能仍不尽如人意。在这里，通过抑制竞争失活过程，包括传统荧光掺杂剂（CFD）上的直接电荷复合和主体到 CFD 的德克斯特能量转移，展示了即使在高亮度下也具有突破性效率的 TSF-OLED。一方面，引入电子惰性末端取代基来保护 CFD 的电子活性核心；另一方面，设计了精细的器件结构以提供多条能量传递路径。结果，在绿色 TSF-OLED 中实现了前所未有的高最大外量子效率/功率效率 24%/71.4 lm W，即使在 5000 cd m 的高亮度下仍保持 22.6%/52.3 lm W。这项工作释放了 TSF-OLED 的潜力，为实际应用铺平了道路。
