A novel donor (D)–spiro-acceptor (A) emitter, namely 10-phenyl-10H-spiro[acridine-9,9′-fluorene]-2′,4′,7′-tricarbonitrile (SAF-3CN), was synthesized for high efficiency, yellowish green third-generation thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs). The CN-modulation of the fluorene was adopted for the modification of the singlet state with minor modifications of the triplet state. Compared to the reference material 10-phenyl-10H-spiro[acridine-9,9′-fluorene]-2′,7′-dicarbonitrile (ACRFLCN), the electron-withdrawing –CN substituent on the C4 site of the fluorene results in a sufficiently small singlet–triplet energy gap (ΔE_ST) and obvious TADF characteristics of SAF-3CN in the doped films. Encouragingly, the device performance achieves an external quantum efficiency (EQE) of 19.4% and small roll-off, which is better than that of ACRFLCN and closer to the best performance in this system.

中文翻译：

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受体调节可改善螺旋型热活化延迟荧光发射体

一种新型的供体（D）-螺受体（A）发射体，即10-苯基-10 H-螺[[啶-9,9'-芴] -2'，4'，7'-三碳腈（SAF-3CN）合成了高效率的黄绿色第三代热激活延迟荧光（TADF）有机发光二极管（OLED）。芴的CN-调节被用于单重态的修饰而对三重态的修饰很小。与参考材料10-苯基-10 H-螺[[啶-9,9'-芴] -2'，7'-二腈（ACRFLCN）相比，芴的C4位上的吸电子-CN取代基在足够小的单重态-三重态能隙（ΔE _ST）和掺杂薄膜中SAF- 3CN的明显TADF特性。令人鼓舞的是，该器件的性能可实现19.4％的外部量子效率（EQE）和小滚降，这比ACRFLCN更好，并且接近该系统的最佳性能。