Highly efficient blue thermally activated delayed fluorescence with ortho-donor appended cyclic boryl acceptor

Abstract

Thermally activated delayed fluorescence (TADF) has recently shown great promise in the field of organic light-emitting diodes (OLEDs). TADF-OLEDs can achieve nearly 100% internal quantum efficiency through the upconversion of triplet excitons to singlet excitons via reverse intersystem crossing (RISC) process. Until now, various kinds of TADF emitters have been reported. In particular, those with boron acceptor moieties are getting more and more attractive because they can show very high TADF properties. Boron acceptors such as triarylborons possess strong electron-accepting properties and thus can form donor–acceptor (DA) emitters exhibiting a high degree of TADF when combined with a suitable donor. In this study, we have synthesized a new boron emitter (DPACoBA) based on ortho-donor appended cyclic boryl acceptor. This novel compound shows very high photoluminescence quantum yield (PLQY) both in solution and in films. OLED devices based on these boron emitters are shown to produce pure blue emission with high external quantum efficiency over 25%. We believe this approach is likely to make a significant contribution to the realization of efficient blue TADF-OLEDs.