Thermally activated delayed fluorescence (TADF) emitters, which convert nonemissive triplets into emissive singlets, have garnered tremendous impetus as next-generation organic electroluminescent materials. Employing donor–acceptor (D–A) designs to produce intramolecular charge transfer (ICT) states is considered an attractive strategy to effectively reduce the singlet–triplet (ΔE_ST) gap, thereby enhancing reverse intersystem crossing (rISC) in TADF emitters. Herein, we report two ICT chromophores (BP-1TPA and BP-2TPA) utilizing a rational design strategy based on a twisted biphthalimide acceptor core integrated with varying triphenylamine donors. We accomplish efficient TADF emission with a high photoluminescence quantum yield (PLQY) of ∼80% at ambient conditions from poly(methyl methacrylate)-doped films of these chromophores. Twisting the acceptor core ensures the separation of natural transition orbitals, leading to small ΔE_ST and generates an intermediate triplet excited state to facilitate rISC. The present study, therefore, sheds light on how delayed fluorescence can be realized from a simple twisted phthalimide core by rational molecular engineering and enables new insights toward exploring the aromatic imide class of molecules as potential organic light-emitting materials.

中文翻译：

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双邻苯二甲酰亚胺基发色团的扭转可实现热激活延迟荧光

热激活延迟荧光（TADF）发射器可将非发射三重态转化为发射单重态，作为下一代有机电致发光材料获得了巨大的推动力。采用供体-受体（D-A）设计来产生分子内电荷转移（ICT）态被认为是一种有吸引力的策略，可以有效减少单线态-三线态（Δ E _ST）间隙，从而增强TADF发射器中的反向系间窜越（rISC）。在此，我们报告了两种ICT发色团（BP-1TPA和BP-2TPA），利用基于与不同三苯胺供体集成的扭曲联邻苯二甲酰亚胺受体核心的合理设计策略。我们利用这些发色团的聚（甲基丙烯酸甲酯）掺杂薄膜，在环境条件下实现了高效的 TADF 发射，光致发光量子产率（PLQY）约为 80%。扭曲受体核可确保自然过渡轨道的分离，从而导致较小的 Δ E _ST并产生中间三重激发态以促进 rISC。因此，本研究揭示了如何通过合理的分子工程从简单的扭曲邻苯二甲酰亚胺核实现延迟荧光，并为探索芳香酰亚胺类分子作为潜在的有机发光材料提供了新的见解。