Dual-channel charge transfer-based thermally activated delayed fluorescence emitter facilitating efficient and low roll-off non-doped devices.

Through-bond charge transfer (TBCT) and through-space charge transfer (TSCT) are simultaneously demonstrated in SFO-SPAC-based TADF emitters, leading to high EQEs of 23.5% and 22.3% in evaporation- and solution-processed non-doped OLEDs along with low efficiency roll-off. [Display omitted] • TBCT and TSCT channels are simultaneously realized in TADF emitters. • Spiral donor–acceptor framework of SFO-SPAC shows nearly 100% PLQY in neat films. • The evaporated non-doped OLEDs achieve an EQE of 23.5% with low roll-off. • The solution-processed non-doped TADF OLEDs achieve an EQE of 22.3%. The development of thermally activated delayed fluorescence (TADF) emitters with fast reverse intersystem crossing rate (RISC) remains huge challenge. In this work, donor–acceptor-type TADF material SFO-SPAC is designed and synthesized, which contains methyl and F-atom shells along with dual-spiral segments. The SFO-SPAC emitter features through-bond and through-space charge transfer due to the distorted donor–acceptor structures and the induced effects of F-atoms. The neat film of SFO-SPAC exhibits a photoluminescence quantum yield of 96%, a fast RISC rate of 1.04 × 106 s−1, and a fast radiative decay rate of 1.90 × 107 s−1. Consequently, the evaporation-processed non-doped green organic light emitting diode (OLED) achieves a maximum external quantum efficiency (EQE) of 23.5% and low efficiency roll-off with an EQE of 20.1% at 5000 cd m−2. In addition, the solution-processed non-doped device shows high EQE up to 22.3%. [ABSTRACT FROM AUTHOR]