Isomer engineering for red thermally activated delayed fluorescence molecules: Luminescence mechanism study and rational molecular design

Abstract

Developing efficient red TADF molecules remains a great challenge and it is extremely urgent to reveal the luminescence mechanisms through theoretical perspectives. Herein, the photophysical properties of two pairs of red TADF isomers in toluene and solid phase have been theoretically studied. Results indicate that, compared with trans-isomers, cis-isomers possess smaller energy gaps which bring fast RISC processes. While for molecules in solid phase, decreased energy gaps and increased spin orbit coupling constants are determined, all these factors contribute to the remarkable RISC processes. Furthermore, previous experimental measurements are reasonably explained and three new red TADF molecules are theoretically proposed.