摘要：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 rolloff and good color purity. However, the superior examples of TSF-OLEDs are still limited up to ***, a trade-off strategy is presented for designing efficient TADF materials and achieving highperformance 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(EQEmax) 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.