High Efficiency and Stable Organic Light-Emitting Diodes Based on Thermally Activated Delayed Fluorescence Emitter**Supported by the National Natural Science Foundation of China under Grant Nos 61420106002, 51373189, 61178061, and 61227008, the Hundred Talents Program of the Chinese Academy of Sciences, the National Basic Research Program of China under Grant No 2014CB932600, and the Start-Up Fund of the Technical Institute of

Abstract

High efficiency, stable organic light-emitting diodes (OLEDs) based on 2-pheyl-4′-carbazole-9-H-Thioxanthen-9-one-10,10-dioxide (TXO-PhCz) with different doping concentration are constructed. The stability of the encapsulated devices are investigated in detail. The devices with the 10 wt% doped TXO-PhCz emitter layer (EML) show the best performance with a current efficiency of 52.1 cd/A, a power efficiency of 32.7 lm/W, and an external quantum efficiency (EQE) of 17.7%. The devices based on the 10 wt%-doped TXO-PhCz EML show the best operational stability with a half-life time (LT50) of 80 h, which is 8 h longer than that of the reference devices based on fac-tris(2-phenylpyridinato)iridium(III) (Ir(ppy)3). These indicate excellent stability of TXO-PhCz for redox and oxidation processes under electrical excitation and TXO-PhCz can be potentially used as the emitters for OLEDs with high efficiency and excellent stability. The high-performance device based on TXO-PhCz with high stability can be further improved by the optimization of the encapsulation technology and the development of a new host for TXO-PhCz.