A Simple Approach to Solution‐Processible Small‐Molecule Multi‐Resonance TADF Emitters for High‐Performance Narrowband OLEDs

Abstract

Most multi-resonance (MR) induced thermally activated delayed fluorescence (TADF) emitters generally exhibit strong aggregation and relatively worse solubility due to their rigid and planar molecule structures, which is highly undesirable for solution-processible devices. Herein, a simple but feasible approach for solution-processible small-molecule MR-TADF emitters is developed by incorporating two MR-TADF units onto carbazole bridge bearing long alkyl chains. The obtained emitters demonstrate supreme film-forming capability and narrowband emissions with full-width at half-maximums (FWHMs) of 22 nm. The resulting solution-processed narrowband electroluminescent devices achieve maximum external quantum efficiency of 27.1 %, which represents the highest efficiency among the solution-processed OLEDs based on MR-TADF emitters. This simple approach reveals great potential of developing solution-processible emitters for rigid and planar molecular structures.