Molecules capable of thermally activated delayed fluorescence (TADF) are promising as emitters in organic light-emitting devices. Processes leading to and competing with TADF in 4,5-di(9H-carbazol-9-yl)-phthalonitrile are analyzed in detail. It is demonstrated that the key features of an efficient TADF emitter include the presence of two triplet states of different natures with potential energy surfaces crossing between the T₁ and S₁ minima and a noticeable dependence of the S₁ → S₀ oscillator strength on molecular deformations from low-frequency antisymmetric vibrational modes. These conclusions can be useful in the targeted design of efficient TADF emitters.

中文翻译：

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深入进行4,5-二（9H-咔唑-9-基）-邻苯二甲腈热活化延迟荧光的从头算研究。

能够热活化延迟荧光（TADF）的分子有望在有机发光器件中用作发射体。详细分析了在4,5-二（9 H-咔唑-9-基）-苯二甲腈中与TADF竞争的过程。结果表明，高效TADF发射器的关键特征包括存在两个不同性质的三重态，势能面在T ₁和S ₁极小值之间交叉，并且S ₁ →S ₀振荡强度对分子的显着依赖性低频反对称振动模式引起的形变。这些结论对于高效TADF发射器的目标设计很有用。