高性能深红与近红外有机固体发光材料：分子和超分子结构的优化与发光波长和效率的调控

Organic light emitting devices (OLEDs) based on noble metal-free thermally activated delayed fluorescence (TADF) are raising increasing interest for their potential to achieve 100% internal quantum efficiency of electroluminescence. For deep red (DR) and near-infrared (NIR) TADF emitters, their exited state energies are quite low and therefore, the emission molecule vibrations, surrounding vibrations, self-absorption, dipole-dipole coupling and so on induced non-radiative channels are very abundant suggesting that achieving highly efficient DR and NIR emission is very hard. The development of high performance DR and NIR organic solids based on molecular structure design is not an efficient approach. We propose to realize highly efficient long wavelength emissions (650-750 nm) by collaboratively optimizing the molecular and supramolecular structures. The TADF organic molecules, which display emission maxima from 580 to 600 nm at monodisperse molecule state, will be designed and synthesized. The supramolecular aggregation induced red-shift of emission maximum is employed to prompt and enhance DR and NIR luminescence. The aggregation induced quenching will be eliminated or depressed by regulating the intermolecular interactions and supramolecualr structures. These DR and NIR emission materials will be used to fabricate high performance organic electroluminescence devices.

由于热活化延迟荧光有机材料的电致发光内量子效率可以达到100%，因此有关研究引起人们广泛关注。深红和近红外热活化延迟荧光有机分子的激发态能量很低，发光分子自身振动、所处环境振动、自吸收、偶极-偶极相互作用等导致的非辐射跃迁途径十分丰富，因此高效率发光很难实现。原理上讲，单纯依赖分子结构设计和优化很难获得高效率的深红和近红外热活化延迟荧光有机固体材料。本项目拟采取分子和超分子结构协同优化的方法，使有机固体材料长波长（650-750 nm）发射和高效率同时实现。拟设计合成分子单分散状态下发光峰位处于橙红光区（580-600 nm）的高效率热活化延迟荧光有机化合物，利用分子聚集形成的超分子结构引起的发射红移实现深红和近红外光发射。同时，通过优化分子间相互作用和超分子结构消除或降低荧光猝灭、实现固体状态下的高发光效率。利用获得的发光材料制备高效率深红和近红外电致发光器件。

深红光和近红外光有机发光材料吸引了很多研究者的关注，其主要原因在于这些材料在生物荧光成像、光通讯、信息安全及有机电致发光等技术领域有潜在应用价值。然而，受到基本能隙理论的限制，设计合成高效率深红光和近红外光有机电致发光材料遇到很大的挑战。我们的研究结果证明，单纯依赖分子结构设计和优化很难获得高效率深红和近红外热活化延迟荧光有机固体材料。本项目提出了分子和超分子结构协同优化的材料设计策略，基于该策略可以使有机固体材料长波长发射（650-750 nm）和高效率同时实现。该项目设计合成出分子处于单分散状态下发光峰位在橙红光区（550-600 nm）的高效率热活化延迟荧光有机化合物，并利用分子聚集形成的超分子结构引起的发射红移获得深红和近红外光发射。通过优化分子间相互作用和分子堆积结构有效降低了荧光猝灭、实现固体状态下的高发光效率。已经利用获得的发光材料制备出了高效率深红和近红外电致发光器件。