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

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%.