Multi-resonance thermally activated delayed fluorescence emitters based on BNCz framework

Abstract

Multi-resonance thermally activated delayed fluorescence (MR-TADF) materials, distinguished by their narrow emission bands and 100% exciton utilization efficiency, represent ideal candidates for high-definition organic light-emitting diode (OLED) displays. In recent years, a variety of MR-TADF emitters based on boron and nitrogen atoms have been developed, exhibiting high external quantum efficiencies and exceptionally narrow electroluminescence spectra. Among these, BNCz stands out due to its straightforward synthesis and excellent structural modifiability. Extensive research on BNCz-based structural modifications primarily focuses on functional substitutions at the para and meta positions relative to the boron atom. Specific strategies include introducing acceptor or donor groups to enhance intersystem crossing or achieve color tuning, modulating steric hindrance to mitigate aggregation-caused quenching, and incorporating chiral groups to induce circularly polarized emission. This review categorizes these substituents based on their structural characteristics and systematically discusses their impacts on the photophysical properties of the BNCz core and the overall performance of OLED devices, thereby providing critical insights for the design and future application of OLED materials.