Thermally activated delayed fluorescence (TADF) sensitized fluorescent organic light-emitting diodes (TSF-OLEDs) have shown great potential for the realization of high efficiency with low efficiency roll-off and good color purity. However, the superior examples of TSF-OLEDs are still limited up to now. Herein, a trade-off strategy is presented for designing efficient TADF materials and achieving high-performance TSF-OLEDs via the construction of a new type of triazolotriazine (TAZTRZ) acceptor. The enhanced electron-withdrawing ability of TAZTRZ acceptor, fused by triazine (TRZ) and triazole (TAZ) together, enables TADF luminogens with small singlet-triplet energy gap (ΔE_ST) values. Meanwhile, the increased planarity from the TRZ-phenyl linkage (6:6 system) to the TAZ-phenyl linkage (5:6 system) can compensate the decrease of oscillator strength (f) while lowing ΔE_ST, thus achieving a trade-off between small ΔE_ST and high f. As a result, the related TSF-OLED achieved an extremely low turn-on voltage of 2.1 V, an outstanding maximum external quantum efficiency (EQE_max) of 23.7% with small efficiency roll-off (EQE₁₀₀₀ of 23.2%; EQE₅₀₀₀ of 20.6%) and an impressively high maximum power efficiency of 82.1 lm W^-1, which represents the state-of-the-art performance for yellow TSF-OLEDs.

热激活延迟荧光 (TADF) 敏化荧光有机发光二极管 (TSF-OLED) 显示出实现高效率、低效率滚降和良好色纯度的巨大潜力。然而，迄今为止，TSF-OLED 的优秀示例仍然有限。在此，提出了一种权衡策略，用于设计高效的 TADF 材料并通过构建新型三唑并三嗪 (TAZTRZ) 受体实现高性能 TSF-OLED。TAZTRZ 受体增强的吸电子能力，由三嗪 (TRZ) 和三唑 (TAZ) 融合在一起，使 TADF 发光体具有小的单重态-三重态能隙 (Δ E _ST) 值。同时，从 TRZ-苯基连接（6:6 系统）到 TAZ-苯基连接（5:6 系统）的平面度增加可以补偿振荡器强度 ( f ) 的降低，同时降低 Δ E _ST，从而实现权衡在小 Δ E _ST和高f之间关闭。因此，相关的 TSF-OLED 实现了 2.1 V 的极低开启电压，出色的 23.7% 的最大外部量子效率 (EQE _max ) 和小的效率滚降（EQE ₁₀₀₀为 23.2%；EQE ₅₀₀₀为20.6%) 和令人印象深刻的 82.1 lm W ^-1的最大功率效率，代表了黄色 TSF-OLED 的最先进性能。