利用对称性破缺策略构筑高效共轭聚合物捕光材料及其光伏性能研究

Organic solar cells have attracted great attentions due to the particular features of light weight, flexibility, semi-transparency, enhanced low-light performance and the capability to be fabricated into large-area devices via solution processing. How to improve photovoltaic performance is critical to realize the commercialization. In our previous work, “symmetry-breaking strategy” based on BDT unit was proposed and employed to construct highly efficient light-harvesting materials with the combination of advantages of both 1D and 2D conjugated polymers. It is worth pointing out that the new strategy can efficiently enhance the open circuit voltage and short-circuit current density simultaneously, which is rare in the previous reports to our knowledge. Therefore, in this project, we will further develop and perfect the above molecular design strategy, and construct a series of highly efficient conjugated polymers through changing the 1D side chains, or tuning the pi electron density and conjugated length of 2D aromatic groups，or applying the strategy to other building blocks. Then, we will investigate systematically the influence of the above aspects in the absorption spectra, energy level, molecular aggregation of these new polymers, explore the relationship between the structures and the properties, and the internal mechanism. Furthermore, the efficiencies and stabilities of the photovoltaic devices based on the new polymers will be improved by device engineering. Through implementing this project, a series of innovative achievements will be obtained in the cutting-edge research field of organic solar cells.

有机太阳能电池由于具有质轻、柔性以及可通过卷对卷大面积制备等优点而备受关注。而如何发展新型分子构建策略提高电池效率是实现产业化的关键问题。在前期工作中，我们初步发展了一种基于苯并二噻吩（BDT）单元侧链的对称性破缺的设计策略，能有效地结合一维和二维同类型共轭聚合物的优点，提高了材料的光伏性能，尤其是器件的开路电压和短路电流密度能同时得到提升，这在以往报道是不多见的。在本项目中，我们拟进一步发展和完善对称性破缺策略：通过或改变一维侧链，或调控二维芳香基团的π电子密度或共轭长度，或应用于其他构筑单元，从而开发一系列高效捕光聚合物材料，深入研究其分子结构-凝聚态-器件性能之间的规律，探索内在机理，力图获得新的科学发现。更进一步，结合器件工程，采取多种手段进行优化，深挖其在光电转换领域中的潜力，通过本项目的实施，力争在有机太阳能电池这个前沿领域中获得重要创新成果。

有机太阳能电池由于具有质轻、柔性以及可通过溶液法大面积制备等优点而备受关注。发展新型分子设计策略构建用于捕光并产生光电转换的给体材料，以期进一步提高效率，是实现产业化的关键所在。项目负责人提出“对称性破缺分子设计策略”，在本项目的资助下，利用该策略构建了不对称的共轭聚合物结构单元，增大了材料从基态到激发态的偶极矩，降低了激子复合几率，增强了分子间相互作用，获得了高性能的有机太阳能电池器件，最高效率远超项目任务书设定的13%，达到了17%。实验结果验证了“对称性破缺”的设计思路是切实可行的，即不对称策略能同时提高材料的短路电流密度、开路电压和填充因子，从而获得高效的电池器件，这不仅为高性能光伏聚合物的构建提供了一种具有较好普适性的新策略，也为未来的共轭聚合物分子设计开启了新视野，可以应用于不同的领域。在4年资助期内，项目负责人以创新分子设计为主线，在共轭聚合物光伏材料领域开展了一系列工作，获得了一些有特色的原创发现。这一系列创新研究成果以通讯作者发表在主流学术期刊Advanced Materials (2篇)，Advanced Energy Materials (2篇)，Advanced Functional Materials (3篇)，Nano Energy，Advanced Science，Journal of Materials Chemistry A，Chemistry of Materials，Macromolecules等SCI收录论文41篇，这些原创性和特色性成果受到了国际同行的广泛关注和多次引用。我们圆满完成了项目任务书的各项指标。