Room temperature phosphorescence from a benzothiophene-based N–B–N multi-resonance core

Abstract

We report a design strategy that enables room temperature phosphorescence from an N–B–N type heterocycle, reminiscent of a multi-resonance thermally activated delayed fluorescence (MR-TADF) compound, by disturbing the alternating frontier molecular orbital distribution pattern through five-membered ring fusion with the boron atom. The 2 wt% doped film in mCP host showed a long phosphorescence lifetime of 51.5 ms at 571 nm at room temperature, with an afterglow visible for up to 1 s.