High-performance red and white organic light-emitting diodes based on a novel red thermally activated delayed fluorescence emitter in an exciplex matrix

Abstract

Blue and green organic emitters based on thermally activated delayed fluorescence (TADF) mechanism have made great progress in organic light-emitting diode (OLED) applications, whereas red and white OLEDs with this kind of emitters are lagging behind. In this text, we develop high-performance red and white OLEDs by doping a novel red TADF emitter 10,10'-(11,12-diphenyldibenzo[a,c]phenazine-3,6-diyl)bis(10H-phenoxazine) (DBBPZ-DPXZ) into a blue emissive exciplex matrix. The highly rigid components and twisted donor-acceptor (D-A) structure of DBBPZ-DPXZ can suppress non-radiation decays and guarantee a small ΔEST, which results in effective exciton utilization. Meanwhile, the exciplex matrix can also provide additional reverse intersystem crossing (RISC) channel and enhance the utilization of triplet excitons. And thus, with doping 6 wt% DBBPZ-DPXZ into the exciplex host, red OLED with an electroluminescence peak at 628 nm and a high EQE of 20.8% is achieved. Moreover, by dropping doping concentration of DBBPZ-DPXZ into 0.2 wt%, a white OLED with Commission Internationale de l'Eclairage of (0.40, 0.38) at the luminance of 1000 cd m−2 and EQE of 20.7% is realized.