Complementary Multi‐Resonance Thermally Activated Delayed Fluorescence Design for Blue OLEDs Beyond the Concentration Limit

Advances in boron-based organic compounds exhibiting multi-resonance (MR)-type thermally activated delayed fluorescence (TADF) have been primarily driven by their potential as narrowband blue emitters for wide-gamut display applications. Nevertheless, the intrinsically planar architecture of MR-type TADF molecules often leads to pronounced concentration quenching at elevated doping levels, posing a significant impediment to realizing highly efficient organic light-emitting diodes (OLEDs). Notably, the exciton quenching effect observed here fundamentally follows the same energy transfer mechanism that underlies exciton migration. Based on this insight, we developed a system comprising two MR-TADF molecules with analogous electronic structures that enable mutual exciton energy transfer. The resultant complementary MR-TADF emitter system exhibits substantially improved resistance to concentration quenching relative to single MR-TADF emitters, effectively suppressing efficiency drop and conferring enhanced control over exciton density. We envisage that this strategy represents a pivotal step toward overcoming the longstanding challenge of concentration quenching in MR-TADF materials, thereby enabling the development of high-performance deep-blue OLEDs.