Regioisomeric Engineering to Optimize the Characteristics of TADF Emitters for High‐Performance Solution Processable Organic Light Emitting Diodes

Abstract Nimble utilization of the regioisomerism concept plays an important role in organic optoelectronic field to exploit high‐performance materials in a concise way. However, the relationship between the binding mode and molecular property is still short of explicit understanding and it impedes the creation of desirable materials efficiently. Herein, we report three regioisomeric emitters with obvious thermally activated delayed fluorescence (TADF) and aggregation‐induced emission characteristics when multiple flexible dendrons are bonded to the different substituted position of carbazole groups (C2/C3/C4) through ether bond. Bonding positions are closely correlated with molecular electrostatic potential, emissive wavelength, reverse intersystem crossing process, and exciton utilization efficiency. Fully solution processable organic light emitting diodes manifest the otherness of these isomers in device performance, and highlight the significant status of these regioisomers not only acting as non‐doped emitter but also functioning as TADF sensitizer in a multi‐resonance system, which show a maximum external quantum efficiency of 20.8% and a narrow full width at half maximum of 29 nm.