基于蒽醌的红色延迟荧光材料的设计合成及光电性质
Design, Synthesis and Optoelectronic Properties of Red Delayed Fluorescence Materials Based on Anthraquinone
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摘要: 由于受到能隙定律的严重约束, 激发态的有机红光材料的非辐射衰减较大, 从而导致其荧光量子产率普遍较低。该文利用电子给/受体(donor-acceptor, D-A)之间不同的连接方式, 在有无苯环作为 π 桥的情况下合成了 AQ-2DPAC 和 AQ-2PDPAC 两种红光蒽醌材料。并系统地研究了上述两种材料的电子结构、热性能、光物理性能和电致发光性能, 以评估苯环作为 π 桥对材料发光性能的影响。两种蒽醌材料采取高度扭曲构造, 均具有优良的聚集诱导发光和延迟荧光特性。该研究表明, 就两种电荷转移发光材料而言, 苯环作为 π 桥的引入使 D-A 得到了更有效的分离, 并减小了最低单重态和三重态激发态之间的能级差, 提高了辐射复合速率, 从而提高荧光量子产率。因此, 荧光量子产率从 D-A 型分子 AQ-2DPAC 的 19% 显著提升至 D-π-A 型分子 AQ-2PDPAC 的 52%。采用 AQ-2PDPAC 发光材料的有机发光二极管器件性能更为优异, 最大外量子效率为 13.7%, 最大亮度为 12 260 cd·m-2。Abstract: Organic red luminogens are seriously bound by that of the energy gap law, giving rise to severe nonradiative decay of excited state and consequently low photoluminescence quantum yield (ΦPL). Herein, two red anthraquinone-based luminogens, AQ-2DPAC and AQ-2PDPAC, are synthesized by using different linking modes between the electron donor and the electron acceptor (D-A) with or without the phenyl ring as π-bridge. Their electronic structures, thermal properties, photophysical properties, and electroluminescent properties are investigated systematically to assess the impact of the phenyl bridge on their photoluminescence properties. Both highly twisted luminogens exhibit obvious aggregation-induced emission and delayed fluorescence features, and the elongation of D-A separation distance via the introduction of phenyl bridge can simultaneously decrease singlet-triplet energy splitting, enhance fluorescence decay rate and consequently increase ΦPL. Therefore, the ΦPL of D-π-A-type AQ-2PDPAC (52%) is much larger than that of D-A-type AQ-2DPAC (19%). The organic light-emitting diode employing AQ-2PDPAC as emitter realizes a high maximum external quantum efficiency of 13.7%, and a maxima luminance of 12 260 cd·m-2.