Accelerating reverse intersystem crossing (RISC) without sacrificing fast radiative decay is effective in suppressing efficiency roll‐off (eRO) in thermally activated delayed fluorescence (TADF)‐based organic light‐emitting diodes. We here report a TADF emitter, CC‐TXO‐I, combining a bicarbazole donor (CC) and a sulfur‐containing acceptor (TXO). The CC is used to accelerate radiative decay via moderate donor‐acceptor torsion angle, and the TXO is expected to provide fast RISC by the heavy atom effect. We realized very large rate constants of RISC (k
RISCs) of ~107 s−1. Both k
RISCs and rate constants of radiative decay of CC‐TXO‐I increased with increasing doping concentration, attributing improved eRO.
A new red-emitting CPL/TADF derivative is reported. A monomeric form is compared to its chiral dimeric counterpart to unravel the impact of dimerization on TADF properties. Circularly polarized fluorescence and phosphorescence are also investigated.
Accelerating reverse intersystem crossing (RISC) without sacrificing fast radiative decay would be effective in suppressing efficiency roll‐off (eRO) in thermally activated delayed fluorescence (TADF)‐based organic light‐emitting diodes. We here report a TADF emitter, CC‐TXO‐I, combining a bicarbazole donor (CC) and a sulfur‐containing acceptor (TXO). The CC is used to accelerate radiative decay via moderate donor‐acceptor torsion angle, and the TXO is expected to provide fast RISC by the heavy atom effect of sulfur. We successfully realized very large rate constants for RISC (kRISC) of ~107 s−1, and eROs were improved by increasing both kRISC and rate constants of radiative decays.
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