Red thermally activated delayed fluorescence materials for high-performance organic light-emitting diode

Abstract

Developing red thermally activated delayed fluorescence (TADF) materials is challenging but crucial for realizing full-color displays and solid-state lighting systems. In this work, we propose a novel design strategy that connects two emitting units to a phenyl ring to create efficient red luminescent materials. Two D-A-π-A-D type TADF molecules with mild-twist structures, m-DTPAQCN and p-DTPAQCN, were designed and synthesized. These molecules incorporate an electron-withdrawing acceptor of quinoxaline-6,7-dicarbonitrile group and an electron-donating donor of triphenylamine group. Both m-DTPAQCN and p-DTPAQCN exhibit red emissions in toluene solutions at 607 nm and 614 nm, respectively, and in doped films at 618 nm and 627 nm. The doped films, prepared with varying doping concentrations, demonstrate excellent photoluminescence quantum yields (PLQYs) ranging from 60.10 % to 84.70 %. The corresponding organic light-emitting diodes (OLEDs) employing m-DTPAQCN and p-DTPAQCN as emitters present efficient red electroluminescence with a maximum external quantum efficiency of 17.37 % and 20.05 %, respectively. This work provides a new and effective strategy for designing efficient red TADF molecules, offering significant potential for application in OLEDs.