联受体型聚合物受体材料在小分子给体/聚合物受体型太阳能电池中的应用

Notable breakthrough on power conversion efficiency of polymer solar cell based on fused-ring acceptors has been achieved in the past few years, mainly due to the synergy between donor and acceptor in energy level, light absorbance, mobility as well as compatibility. Contrary to expectation, development of the small-molecule donor/polymer acceptor organic solar cell is still in slow pace because of the lack of high performance polymer acceptors and the unsatisfactory morphology of the donor/acceptor blends. Given that, this project will focus on developing new polymeric acceptor materials and novel methods for precisely controlling the microphase structure, which includes: (1) By introducing the linked-acceptors to the D-A copolymers and adjusting chemical structure, energy level and intermolecular interactions, we expect to obtain new polymer acceptor that has narrow band gap, broadened absorption spectrum and relatively high electron mobility. (2) Appropriate small-molecule donor will be carefully selected to build the donor/acceptor system with the new polymer acceptor, and the phase compatibility and the packing orientations of molecules in the blends will be actively optimized subsequently. (3) By constructing organic solar cells with novel polymer acceptors, the project seeks a breakthrough on power conversion efficiency.

近年来，基于稠环小分子受体的聚合物太阳能电池的光电转化效率已取得重大突破，这主要得益于给/受体在能级、光谱、迁移率和相容性等方面发挥出了良好的协同效应。但同为小分子、聚合物组合的小分子给体/聚合物受体型太阳能电池的发展却受到了聚合物受体材料种类匮乏、性能偏低以及给/受共混体系微相形貌不理想等因素的严重限制。本项目将主要聚焦于这一体系中新材料的开发和微相结构的调控等关键问题，拟开展如下工作：（1）在D-A共聚结构的基础上引入联受体单元，通过对共聚物结构、能级和分子间作用力的调节来获得具有窄带隙、宽吸收、高电子迁移率特性的新型聚合物受体材料；（2）选择与之匹配的小分子给体，结合共混相形貌调控，改善给/受体之间的相容性，优化二者在共混相中的分子排列取向；（3）构建新型小分子给体/聚合物受体太阳能电池体系，实现光电转化效率更高层次的突破。

本项目在实施过程中开发出了多种有机光伏材料，包括联受体共聚型聚合物给体材料、小分子给体材料和小分子电极修饰层材料等。基于这些材料，我们分别在半透明有机太阳能电池、全小分子有机太阳能电池以及高效非富勒烯型聚合物太阳能电池领域取得了一定的进展和突破。具体说来，我们利用本项目提出的联受体共聚型聚合物材料的设计策略研发出了一种适用于半透明有机太阳能电池的窄带隙聚合物给体材料。基于这一材料，我们实现了半透明有机太阳能电池11%的光电转化效率和35%的平均可见光透过率的突破；我们开发出了一种能够在三元富勒烯体系全小分子电池和三元非富勒烯体系全小分子电池中都能发挥电荷传输作用的客体小分子给体材料，通过引入这一材料有效地提升了全小分子有机太阳能电池的光电转化效率；此外，我们还开发出了一种简单易制备的小分子电极修饰材料，基于这一材料，我们大幅提升了非富勒烯型聚合物太阳能电池的光电转化效率，并获得了18.4%的效率突破。总之，这些成果的取得在一定程度上有助于推动未来有机太阳能电池商业化应用的进程。