A new class of donor–bridge–acceptor (D−π–A) π-conjugated light-emitting molecules comprising carbazole as donor and maleimide (Cbz-MI, Cbz-MI(d)), phthalimide (Cbz-Pth) as acceptor units with phenyl ring as spacer have been synthesized in good yields. These compounds exhibit high quantum yield with three distinct emission colors yellowish-green (Cbz-MI), bright yellow Cbz-MI(d), and sky blue (Cbz-Pth) in the solid state. Single-crystal X-ray and quantum chemical calculations reveals that twisting of the phenyl rings with high torsional angle on maleimide and phthalimide units reduce the effective inter-chromophore electronic coupling, furnish dramatic changes in their photophysical properties in solution and solid states. Intriguingly, Cbz-MI(d) and Cbz-Pth exhibits a unique aggregation-induced blue-shifted emission (AIBSE) due to restricted intramolecular rotation (RIR) process, while Cbz-MI shows red-shifted emission in the solid state. The solvatochromic study reveal that combined RIR and excited state migration augment AIE (aggregation-induced emission) properties. The electrochemical properties reveal that Cbz-MI exhibits high oxidation propensity while Cbz-Pth shows low reduction values. Subsequently, organic light-emitting diodes (OLEDs) were fabricated with a simple three-layer device containing Cbz-Pth and Cbz-MI(d) as emitting layers. Cbz-MI(d) exhibits high performance yellow OLED with an external quantum efficiency exceeding ∼4.1% and a brightness exceeding ∼73915 cd/m², which is among the best performance reported for bright yellow fluorescence organic light-emitting diodes.

中文翻译：

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聚集诱导发射可实现高效的蓝色和黄色有机发光二极管

一类新型的供体-桥-受体（D-π-A）π共轭发光分子，包括咔唑作为供体和马来酰亚胺（Cbz-MI，Cbz-MI（d）），邻苯二甲酰亚胺（Cbz-Pth）以苯环为间隔基的高产率单元已经合成。这些化合物具有高的量子产率，具有三种不同的发射颜色：黄绿色（Cbz-MI），亮黄色Cbz-MI（d）和天蓝色（Cbz-Pth）处于固态。单晶X射线和量子化学计算表明，在马来酰亚胺和邻苯二甲酰亚胺单元上具有高扭转角的苯环扭曲会降低有效的生色团电子耦合，从而在溶液和固态下提供其光物理性质的巨大变化。有趣的是，由于分子内旋转（RIR）受到限制，Cbz-MI（d）和Cbz-Pth表现出独特的聚集诱导蓝移发射（AIBSE），而Cbz-MI在固态下显示红移发射。溶剂变色研究表明，RIR和激发态迁移相结合可增强AIE（聚集诱导的发射）特性。电化学性能表明Cbz-MI表现出高氧化倾向，而Cbz-Pth表现出低还原值。随后，用包含Cbz-Pth和Cbz-MI（d）作为发光层的简单三层器件制造有机发光二极管（OLED）。Cbz-MI（d）表现出高性能的黄色OLED，其外部量子效率超过〜4.1％，亮度超过〜73915 cd / m ²，是亮黄色荧光有机发光二极管的最佳性能之一。