Coumarin-Based Thermally Activated Delayed Fluorescence Emitters with High External Quantum Efficiency and Low Efficiency Roll-off in the Devices

• DOI: 10.1021/acsami.6b15816
• Publication Date: 2017-02-21T15:48:44Z
• Authors: Jia-Xiong Chen; Wei Liu; Cai-Jun Zheng; Kai Wang; Ke Liang; Yi-Zhong Shi; Xue-Mei Ou; Xiao-Hong Zhang
• Keywords: Quantum Efficiency

Thermally activated delayed fluorescence (TADF) emitters have attracted much interest for their great applications in organic light-emitting diodes (OLEDs), but the TADF OLEDs are limited by large efficiency roll-offs. In this study, we report two coumarin-based emitters, 3-methyl-6-(10H-phenoxazin-10-yl)-1H-isochromen-1-one (PHzMCO) and 9-(10H-phenoxazin-10-yl)-6H-benzo[c]chromen-6-one (PHzBCO), with relatively high photoluminescence quantum yields (PLQYs) extremely small singlet-triplet splittings. using these compounds as respectively demonstrate external efficiencies of 17.8% PHzMCO 19.6% PHzBCO, which highest among reported coumarin-derivative-based OLEDs. More importantly, devices based on PHzBCO remained 10.3% 12.9% at 10000 cd m-2, respectively, showing low roll-offs brightness. These results reveal that PLQYs can effectively reduce roll-off devices.