基于氮杂环的新型三维共轭小分子受体材料的分子构筑及其光伏性能研究

Recently, although organic solar cells have made breakthroughs in device performance due to the development of non-fullerene acceptors, they still face many problems that need to be solved, such as the charge mobility based on current A-D-A linear acceptors are relatively low which makes the performance of the device is sensitive to the thickness of the active layer, and the energy loss is relatively large, which makes the device performance difficult to further improve. Therefore, it is particularly urgent to develop high-performance novel acceptors. This project proposes the construction of a novel three-dimensional conjugated small molecule acceptors with nitrogen heterocycles for organic solar cells. The unique advantages of the novel acceptors are: nitrogen heterocycles can enhance the electron delocalization of the aromatic nucleus, decrease recombination energy, and can reduce energy loss; In addition, the three-dimensional structure allows the molecule to have three strong electron-withdrawing end groups, which can promote charge separation and transportation, while increasing the absorption coefficient; Besides, the three-dimensional structure of the acceptor can increase the charge transport channels, prevent excessive aggregation of molecules, and easily form an ideal active layer morphology with the donor materials; Moreover, three-dimensional conjugated molecules are beneficial for research and reveal the regulation mechanism of molecular chemical structure and spatial stereology on photovoltaic performance. In-depth study of the effects of molecular structure on energy levels, absorption, energy loss, microphase structure and device performance, and to develop high-performance new acceptor materials with high mobility and low energy loss.

尽管有机太阳能电池因非富勒烯受体的开发使其器件性能在近几年得到突破性进展，但仍面临诸多亟需解决的难题，如目前基于A-D-A类线型受体的电荷迁移率还相对较低导致器件性能对活性层厚度敏感、能量损失相对较大导致器件性能较难进一步提升等，因此发展高效新型受体显得尤为迫切。本项目提出构筑新型含氮杂环的三维共轭小分子受体用于有机太阳能电池。新型受体的独特优势是：氮杂环能增强芳核的电子离域作用、降低重组能，减小能量损失；此外，三维结构使分子具有三个强吸电子末端基，能促进电荷分离与传输，同时提高吸收系数；三维结构的受体还具有各向同性的载流子高效传输性能、且能防止分子过度聚集，易与给体形成理想的活性层形貌；另外，三维共轭分子有利于研究和揭示分子化学结构和空间立构对光伏性能的调控机制。深入研究分子结构对能级、吸收、能量损失、微相结构及器件性能的影响，从而发展同时具备高迁移率和低能量损失的高性能新型受体材料。

本项目针对目前线型受体的电荷迁移率还相对较低导致器件性能对活性层厚度敏感、能量损失相对较大导致器件性能较难进一步提升等科学问题，提出构筑一类新型含氮杂环的三维共轭小分子受体用于有机太阳能电池。本项目构筑了一系列含氮杂环的三维共轭稠环小分子材料，研究发现，这类分子由于其自身结构特点，分子不易聚集，结晶性弱等特点使其适合Y系列受体的器件加工，具有三维共轭骨架材料的引入可以分散Y系列受体的聚集，优化活性层形貌，同时减小能量损失，提高器件效率和稳定性；设计合成了含氮杂环的A-D-A’-D-A和A-D-A型非富勒烯受体，并结合烷基侧链、二维氟化以及末端工程进行协同优化，实现合成步骤简单，改善分子组装性能和光电性能；结合三元策略、添加剂策略以及准平面异质结器件结构进一步优化活性层形貌和降低能量损失，从而实现有机太阳能电池器件性能和稳定性大幅提高。该项目的研究成果为将来有机太阳能电池的商业化发展提供了丰富的材料和理论指导。相关研究成果在Nat. Commun., Adv. Mater., Energy Environ. Sci., Adv. Energy Mater., Adv. Funt. Mater., ACS Nano, Sci. China Chem., Chem. Eng. J., Chem. Mater., J. Energy Chem., Chin. Chem. Lett.等国际权威期刊上相继发表论文23篇，其中影响因子大于10的论文13篇，入选ESI高被引论文3篇，申请发明专利5项，其中授权1项。研究工作被Chem. Rev., Chem. Soc. Rev., Nat. Commun., J. Am. Chem. Soc., Angew. Chem. Int. Ed., Adv. Mater.等国际顶级期刊引用和详细点评。