Thermally activated delayed fluorescence (TADF) emitters have received much attention for the fabrication of white organic light-emitting diodes (WOLEDs); however, challenges remain owing to severe efficiency roll-off, poor color stability, and high cost. In this contribution, solution-processed hybrid WOLEDs were obtained by employing a blue TADF dendrimer, bis{4-[3,6-bis(3,6-di-tert-butylcarbazol-N-yl)carbazol-N-yl]phenyl}sulfone (BPS), combined with an orange iridium complex, bis(2-phenylbenzothiazolato)(acetylacetonate)iridium(III), Ir(bt)2 (acac), as a co-dopant. The devices achieved a maximum external quantum efficiency of 6.59 % and a maximum current efficiency of 17.34 cd A-1 . The results suggest that the TADF dendrimer serving as an assistant dopant were helpful in reducing the triplet populations by up-converting the triplet excitons to the singlet state and immediately transferring the singlet excitons to Ir(bt)2 (acac) (bt=2-phenylbenzothiazolato, acac=acetylacetonato) by virtue of the long-range Förster resonance energy transfer, thus significantly decreasing the triplet-triplet annihilation (TTA). Moreover, the emitters can act as shallow trapping centers to decrease charge and exciton aggregation. The resulting OLEDs exhibit stable electroluminescent spectra and low efficiency roll-off at relatively high current density. The CIE coordinates Δ(x, y) vary only (0.02, 0.02) in the luminance range of 100 to 10 000 cd m-2 .

中文翻译：

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基于蓝色热激活延迟荧光树枝状聚合物的溶液处理的暖白色有机发光二极管。

热激活延迟荧光（TADF）发射器在白色有机发光二极管（WOLED）的制造中受到了广泛的关注。然而，由于严重的效率下降，差的颜色稳定性和高成本，仍然存在挑战。在此贡献中，通过使用蓝色TADF树状大分子双{4- [3,6-双（3,6-二叔丁基咔唑-N-基）咔唑-N-基]苯基获得溶液处理的混合WOLED。 }砜（BPS）与橙色铱配合物双（2-苯基苯并噻唑并）（乙酰丙酮）铱（III），Ir（bt）2（acac）混合使用。该器件的最大外部量子效率为6.59％，最大电流效率为17.34 cd A-1。结果表明，TADF树枝状大分子作为辅助掺杂剂有助于将三重态激子上转换为单重态，并立即将单重态激子转移到Ir（bt）2（acac）（bt = 2-苯并噻唑并（acac =乙酰丙酮），通过长距离Förster共振能量转移，从而显着降低了三重态-三重态an灭（TTA）。此外，发射极可以充当浅陷阱，以减少电荷和激子聚集。所得的OLED在相对较高的电流密度下表现出稳定的电致发光光谱和低效率的滚降。CIE坐标Δ（x，y）在100至10000cd m-2的亮度范围内仅变化（0.02，0.02）。