Regioisomer Effect of Pyrene on Multi‐Resonance Emitters and Their Application for Hyperfluorescence Organic Light‐Emitting Diodes

Abstract Multiple‐resonance (MR) type emitters have overcome several issues in organic light‐emitting diodes (OLEDs) because of their narrowband emission and high electroluminescence quantum yield efficiency. Also, this kind of emitters has been widely used as hyperfluorescence (HF)‐OLEDs thanks to their advantageous properties. However, there has been a significant challenge for HF‐OLEDs based on MR emitters, which is impacted by the nature of the long‐lived triplet excitons of MR emitters, as there is a trade‐off between narrowband emission and short exciton lifetime. Herein, the low‐possessed triplet energy level of pyrene is introduced to an MR core unit to achieve stable HF‐OLEDs with the development of three isomers to investigate the regioisomer effect of pyrenes. The improved device lifetimes are successfully achieved, and the reasons for the differences in excimer formation and stability between those three isomers are studied.