Herein, we have synthesized 4,5-diphenyl-1H-imidazole and 2-(1H-indol-3-yl)acetonitrile based donor–π–acceptor fluorophores and studied their optical, thermal, electroluminescence properties. Both the fluorophores exhibit high fluorescence quantum yield (Φ_f = <0.6) and good thermal stability (T_d10 = <300 °C), and could be excellent candidates for OLED applications. Moreover, the ground and excited state properties of the compounds were analysed in various solvents with different polarities. The geometric and electronic structures of the fluorophores in the ground and excited states have been studied using density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. The absorption of BIPIAN and BITIAN in various solvents corresponds to S₀ → S₁ transitions and the most intense bands with respect to the higher oscillator strengths are mainly contributed by HOMO → LUMO transition. Significantly, the vacuum deposited non-doped OLED device was fabricated using BITIAN as an emitter, and the device shows electroluminescence (EL) at 564 nm, maximum current efficiency (CE) 0.687 cd A⁻¹ and a maximum external quantum efficiency (EQE) of 0.24%.

中文翻译：

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可调谐 2-(1H-indol-3-yl) 乙腈基荧光团对光学、热和电致发光特性的影响†

在此，我们合成了 4,5-二苯基-1 H-咪唑和 2-(1 H-吲哚-3-基)乙腈基供体-π-受体荧光团，并研究了它们的光学、热学和电致发光性质。两种荧光团都表现出高荧光量子产率 ( Φ _f = <0.6) 和良好的热稳定性 ( T _d10= <30​​0 °C)，并且可能是 OLED 应用的优秀候选者。此外，在不同极性的各种溶剂中分析了化合物的基态和激发态性质。使用密度泛函理论 (DFT) 和时间相关密度泛函理论 (TDDFT) 方法研究了基态和激发态荧光团的几何和电子结构。BIPIAN和BITIAN在各种溶剂中的吸收对应于S ₀ → S ₁关于较高振荡器强度的跃迁和最强烈的带主要是由 HOMO → LUMO 跃迁贡献的。值得注意的是，真空沉积非掺杂OLED器件是使用BITIAN作为发射器制造的，该器件在564 nm处显示出电致发光（EL）、最大电流效率（CE）0.687 cd A ^-1和最大外量子效率（EQE） 0.24%。