Accelerating reverse intersystem crossing by bridging two multiresonant thermally activated delayed fluorescence emitters with [2.2]paracyclophane

The development of circularly polarized multi-resonant thermally activated delayed fluorescence (CP-MR-TADF) materials with fast reverse intersystem crossing (RISC) process remains a challenge. Herein, we introduce high-lying excited states to assist the RISC process. Through arranging two known MR-TADF emitters tCzBN and DiKTa at the pseudo-ortho position of a chiral skeleton paracyclophane (PCP), the excited states density was increased. The proof-of-concept emitter po-PCP-tCzBN-DiKTa shows nearly 3 times higher kRISC (5.31×104 s-1) than PCP-tCzBN (1.73×104 s-1) without compromising color purity and exhibiting circularly polarized luminescence (CPL) with |gPL| values at the 10-4 level. The solution processed organic light-emitting diodes (SP-OLEDs) with po-PCP-tCzBN-DiKTa shows high maximum external quantum efficiency (EQEmax) reaches 23% with a moderate efficiency roll-off showing EQE of 18% and 9% at 100 cd/m2 and 1000 cd/m2.