A spin-flip from a triplet to a singlet excited state, that is, reverse intersystem crossing (RISC), is an attractive route for improving light emission in organic light-emitting diodes, as shown by devices using thermally activated delayed fluorescence (TADF). However, device stability and efficiency roll-off remain challenging issues that originate from a slow RISC rate (k_RISC). Here, we report a TADF molecule with multiple donor units that form charge-resonance-type hybrid triplet states leading to a small singlet–triplet energy splitting, large spin–orbit couplings, and a dense manifold of triplet states energetically close to the singlets. The k_RISC in our TADF molecule is as fast as 1.5 × 10⁷ s⁻¹, a value some two orders of magnitude higher than typical TADF emitters. Organic light-emitting diodes based on this molecule exhibit good stability (estimated T₉₀ about 600 h for 1,000 cd m⁻²), high maximum external quantum efficiency (>29.3%) and low efficiency roll-off (<2.3% at 1,000 cd m⁻²).

从三重态激发到单重态激发的自旋翻转，即反向系统间交叉（RISC），是改善有机发光二极管发光的诱人途径，如使用热激活延迟荧光（TADF）的设备所示。但是，由于RISC速率慢（k _RISC），器件的稳定性和效率下降仍然是具有挑战性的问题。在这里，我们报告了一个具有多个供体单元的TADF分子，这些供体单元形成了电荷共振型杂化三重态，导致了一个单重态-三重态能量分裂，大的自旋-轨道耦合以及一个紧密靠近三重态的密集的三重态。TADF分子中的k _RISC高达1.5×10 ⁷  s ^-1，该值比典型的TADF发射器高两个数量级。基于该分子的有机发光二极管表现出良好的稳定性（对于1,000 cd m ^-2，估计T ₉₀约为600 h ），最大外部量子效率高（> 29.3％）和低效率滚降（在1,000 cd时<2.3％） m ^-2）。