Employing dual-emission thermally activated delayed fluorescence (TADF) molecules to fabricate single emitters in highly efficient white organic light-emitting diodes (WOLEDs) is still a challenge. In this work, a systematic study on the luminescence mechanism of three TADF molecules with blue–orange dual emission is performed. It is found that the quasi-axial (ax) conformer is responsible for blue normal fluorescence (NF), while the quasi-equatorial (eq) conformer is responsible for orange TADF. In addition, the upconversion for the TADF molecules happens from the first triplet state (T₁) and the second triplet state (T₂) to the first singlet state (S₁) in the quasi-equatorial conformers. In addition, the transition from T₁ to S₁ and T₂ to S₁ also happens in the process of conformation transformation. Besides, our study also indicates that the donor with an asymmetric bond length in the six-membered ring could favor the generation of dual conformations and dual emission. Some molecules with PTZ or PXZ as donors are predicted as potential emitters with white light emission. Our research would favor the design of TADF emitters with dual emission in WOLEDs.

中文翻译：

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白色有机发光二极管中热激活延迟荧光发射体的理论研究：发射机理和分子设计。

在高效的白色有机发光二极管（WOLED）中，采用双发射热激活延迟荧光（TADF）分子制造单个发射器仍然是一个挑战。在这项工作中，对蓝橙色双发射的三个TADF分子的发光机理进行了系统的研究。发现准轴（ax）构象负责蓝色正常荧光（NF），而准赤道（eq）构负责橙色TADF。另外，TADF分子的上转换在准赤道构象异构体中从第一三重态（T ₁）和第二三重态（T ₂）发生到第一单重态（S ₁）。此外，从T ₁到S的过渡₁和T ₂至S ₁也在构象转换过程中发生。此外，我们的研究还表明，在六元环上具有不对称键长的供体可能有利于双构象和双发射的产生。某些以PTZ或PXZ为供体的分子被预测为具有白光发射的潜在发射体。我们的研究将支持WOLED中具有双发射的TADF发射器的设计。