Efficient selenium-integrated TADF OLEDs with reduced roll-off

Organic light emitters based on multiresonance-induced thermally activated delayed fluorescent materials have great potential for realizing efficient, narrowband organic light-emitting diodes (OLEDs). However, at high brightness operation, efficiency roll-off attributed to the slow reverse intersystem crossing (RISC) process hinders use of in practical applications. Here we report a heavy-atom incorporating emitter, BNSeSe, which is selenium-integrated boron–nitrogen skeleton and exhibits 100% photoluminescence quantum yield RISC rate (kRISC) 2.0 × 106 s−1. The corresponding green OLEDs exhibit excellent external efficiencies up 36.8% ultra-low character brightnesses (with very small values 2.8% 14.9% 1,000 cd m−2 10,000 m−2, respectively). Furthermore, outstanding capability harvest triplet excitons also enables BNSeSe be superior sensitizer hyperfluorescence OLED, shows state-of-the-art performance with 40.5%, power beyond 200 lm W−1, luminance close 20,0000 m−2. Green offer operational reduced roll-off.