Effect of reverse intersystem crossing rate to suppress efficiency roll-off in organic light-emitting diodes with thermally activated delayed fluorescence emitters

â¿¢EL efficiency roll-off in OLEDs based on TADF emitters was investigated.â¿¢Rate constants of intramolecular exciton relaxation processes were investigated.â¿¢EL roll-off was dramatically suppressed with an emitter showing faster RISC.â¿¢Initial EL decreasing caused by strong STA occurred when RISC was lower.â¿¢Faster RISC reduced triplet exciton density and suppressed STA and TTA.