Through-space charge transfer enables efficient carbonyl/amine multi-resonance emitters for organic light-emitting...

Owing to their narrow-band emission and high color purity, multiple-resonance thermally activated delayed fluorescence (MR-TADF) emitters have emerged as promising contenders for ultra-high-definition organic light-emitting diodes (OLEDs). However, carbonyl/amine MR-TADF systems are still plagued by sluggish reverse intersystem crossing (RISC) and severe aggregation-caused quenching (ACQ), limiting device efficiency and concentration tolerance. Herein, we propose a through-space charge-transfer (TSCT) strategy by integrating a spirolocked carbazole donor with a carbonyl/amine MR acceptor skeleton. The resulting emitter, tCON-SCFMe, exhibits controllable TSCT characteristics enabled by intramolecular π-stacking interactions, which effectively promote exciton upconversion while maintaining a small emission redshift and narrowband emission. Meanwhile, the sterically congested structure suppresses intermolecular quenching and enhances anti-aggregation capability. Consequently, the optimized OLED achieves greenish-blue emission at 488 nm with a maximum external quantum efficiency (EQE_max) of 20.2%. Notably, the OLED retains a high EQE of 14.6% at a doping concentration of 20 wt%, demonstrating excellent concentration tolerance. This study provides a robust molecular design for simultaneously regulating exciton dynamics and aggregation behavior in carbonyl/amine MR-TADF emitters for efficient narrowband OLEDs.