聚合物太阳能电池内电荷分离机制的新挑战及机理研究

Based on the broad prospects of polymer solar cells in energy utilization and the newest problems about the understanding on the charge separation mechanism in experiments, this project will highlight the challenges to the traditional exciton theory resulting from charge transfer state formation and ultrafast charge separation phenomenon, and carry out a systematic research to the key physical processes through establishing physical models. Specific contents are: Research on the charge separation mechanism dominated by cold charge transfer state, including the charge separation induced by the interfacial molecular orientation distribution, configuration, and other micro-morphology, and induced by the interfacial distribution forms of temperature field; Research on the charge separation mechanism dominated by thermal charge transfer state, including the role of its excess energy in the charge separation, the regulation of the ultrafast internal conversion relaxation on charge separation dynamics under different interface micro-morphology and temperature conditions; Mechanism research on the experimentally observed ultrafast charge separation phenomenon, including the currently known delocalized mechanism of excited states, and our proposed ultrafast charge separation mechanism induced by the interface micro-morphology and local electric field. These works of this project will be closely combined with the latest experimental progress. We believe that the research will help to find a new theoretical breakthrough for the device physics research of polymer solar cells, and further improve their photovoltaic performance.

基于聚合物太阳能电池在能源利用中的广阔前景及实验中对其电荷分离机制认识的最新问题，本项目将突出电荷转移态产生和超快电荷分离现象对传统激子理论的挑战，建立物理模型对其中关键的物理过程展开机理性研究。具体内容为：冷电荷转移态主导的电荷分离机制研究，包括由界面分子取向分布、弯曲堆叠等微观形貌诱导的电荷分离和界面附近温度场分布形式诱导的电荷分离；热电荷转移态主导的电荷分离机制研究，包括其剩余能对电荷分离的作用机理和其超快内转换对电荷分离效率的调控；超快电荷分离实验现象的机理研究，包括目前已认同的激发态离域性机制和本项目提出的界面分子微观形貌及局域电场的诱导机制。这些工作将与最新的实验进展密切结合，相信能为聚合物太阳能电池器件物理的研究及其光伏性能的进一步提升找到新的理论突破口。

聚合物太阳能电池由于柔性、重量轻、半透明及成膜技术简单，在能源利用中已展现出广阔前景，并成为多学科领域研究的热点。本项目对聚合物太阳能电池电荷分离机制认识的新问题和新现象展开基础性理论研究，研究手段主要为物理模型结合非绝热的量子动力学方法。研究内容和创新点包括：（1）通过引入聚合物光伏体系内禀存在的不同无序效应，澄清了它们对激发态性质、受激吸收及内转换弛豫动力学的影响，解释了实验中相关体系的电荷分离现象；（2）首次提出了聚合物光伏体系内禀存在的非均匀场（非均匀电场和非均匀分子排列构型场）诱导的激子超快输运，为解释超快电荷分离和光伏体系优化设计提供了新的方向；（3）首次提出了聚合物光伏体系D/A界面非均匀场驱动的“冷”CT(电荷转移)态电荷分离机制，并解释了实验中观察到的CT态沿D/A界面的输运现象；（4）针对聚合物光伏体系D/A界面亚带隙吸收和“冷”CT态再吸收对电荷分离的贡献，研究了界面结构和光激发条件等因素对它们的影响，阐明了调控界面亚带隙吸收和“冷”CT态再吸收的有效途径；（5）研究了聚合物光伏体系D/A界面结构和受体分子聚集对电荷及能量转移的影响，为认识和调控器件电荷及能量转移的协同效应提供了明确的理论指导；（6）结合本项目的研究成果，发表“有机太阳能电池的能量损耗：机制、策略和展望”综述文章，提出了该领域亟需解决的基础性物理问题。