近红外有机发光材料及其器件（NIR-OLEDs）在信息安全显示、光纤通讯、生物成像等领域应用前景广阔。然而受限于能隙规则，随着波长红移，有机分子激发态的非辐射跃迁速率呈指数上升，导致有机材料在NIR区普遍存在发光效率低的难题。同时，基于传统荧光材料的电致发光器件受限于自旋统计规则，通常只能利用25%的单线态激子，从而导致器件外量子效率（EQE）更低。如何理性设计高效有机NIR发光材料？是否有可能突破能隙规则的限制实现高效的纯有机NIR-OLEDs？是当前有机发光领域极具挑战性的难题。本文设计合成了三种基于苊并吡嗪受体和三苯胺给体的纯有机小分子发光材料，其在固态下可以形成分子间电荷转移聚集体，深入研究其单分子结构、聚集体结构与材料光电性能之间关系，发现分子间电荷转移聚集体在实现高效近红外发光材料和器件方面具有独特优势。主要成果如下：1. 设计合成了两种基于苊并吡嗪衍生物受体的纯有机小分子发光材料，在薄膜中能形成分子间电荷转移聚集体，在近红外I区实现了高效发光，并诱导出热活化延迟荧光（TADF）性质。以其制备的OLED器件，发光峰值为 682 nm、788 nm、804 nm时，最大外量子效率分别为 21.65%、2.42%、1.41%，是目前报道的TADF-OLEDs在相同波段下的最高值。2. 设计合成了基于苊并四氮杂萘衍生物受体的近红外材料，在薄膜中能形成分子间电荷转移聚集体。以其制备的OLED器件，发光峰值位于1010 nm，是目前报道的首个在近红外II区发光的TADF-OLED。3. 通过实验和理论计算证明了固态下分子间电荷转移聚集体的存在，发现了 分子间电荷转移聚集体的形成可实现显著的光谱红移、诱导并增强 TADF 性质、抑制非辐射跃迁，是实现高效近红外有机发光的新策略。
Near-infrared pure organic emitting materials and their organic light-emitting diodes (NIR-OLEDs) have great potentials in the applications of information security display, optical communications, bio-imaging, etc. However, due to the energy-gap law, the bathochromic shift of the wavelength will induce exponential growth of the non-radiative decay rate, leading to a low emitting efficiency of the pure organic emitting materials. Meanwhile, OLEDs based on conventional materials are limited by the spin statics, in which only the 25% singlet excitons can be used, leading to a low external quantum efficiency (EQE). How to rationally design the high-efficiency pure organic NIR emitting materials? Is it possible to develop high-efficient NIR-OLEDs by breaking the spin statics? These are very challenging problems in the development of pure organic emitting materials.In this work, three pure organic emitting materials based on the acenaphtho[1,2-b]pyrazine-8,9-dicarbonitrile acceptor and triphenylamine donor were designed and synthesized. In solid states, these molecules can form intermolecular charge transfer aggregates. The molecular structure, packing modes in single crystals and their characteristics were compared to study their relationships. Moreover, these materials were finally used in OLEDs. The main contents are as follows: 1. Based on the acenaphtho[1,2-b]pyrazine-8,9-dicarbonitrile acceptor, two novel pure organic emitting materials were designed and synthesized. With the formation of intermolecular charge transfer aggregates in films, highly-efficient NIR I emission were achieved and the thermally activated delayed fluorescence (TADF) were informed. Based on these dyes, the emission peak wavelength of the OLEDs are 682 nm、788 nm、804 nm, and the maxmum EQEs are 21.65%、2.42%、1.41%, respectively, which are highest EQEs among the TADF-OLEDs with similar electroluminescent wavelength. 2. Based on the acenaphtho[1,2-b]pyrazino[2,3-e]pyrazine-9,10-dicarbonitrile acceptor, a novel pure organic emitting materials were designed and synthesized. With the formation of intermolecular charge transfer aggregates in films, the emission peak wavelength of the OLED is 1010 nm, which is the first TADF-OLED in NIR II.3. The formation of intermolecular charge transfer aggregates in solid states was proved with experiments and theoretical calculations. The formation of intermolecular charge transfer aggregates can achieve significant red-shifted wavelength, inform and enhance the TADF characters from non-TADF molecule, as well as reduce the non-radiative decay, which demonstrate a new design strategy to achieve high-efficient NIR emission.
