三元共混聚合物光伏体系的界面电荷产生及复合动力学研究

One of the latest developments in the polymer photovoltaics that allowed optimization of their performance is related to the use of ternary blend structure. Although tedious adjustment of the third component provides the ternary blend improvement, the mechanism behind it is still not clear. In this project, we will focus on the charge photogeneration and recombination processes at the interface of ternary blend photovoltaics, aiming at understanding the photoelectrical mechanism of the tailored optimization of the ternary device performance by studying the correlation between the third component content and photoelectric conversion dynamics. For that, we will study the correlations among the contents of third component, charge transfer state and device performance by applying a combination of steady state spectroscopy, various microscopy methods and device characterization; we will study effect of third component content and device working conditions on charge photogeneration and recombination dynamics at the interface of ternary blend photovoltaics, by applying time resolved spectroscopy; Based on the above steady-state and time-resolved results, the mechanism behand the adjustment of device output performance via the content of the third component is clarified. This study can reveal the intrinsic correlation between the output performance of ternary blend photovoltaic devices and photoelectric conversion dynamics, and provide some new ideas and theoretical basis for designing materials and optimizing the output performances of ternary blend photovoltaics.

三元共混结构是优化聚合物光伏性能的重要方式，是聚合物光伏领域的最新发展方向之一。尽管三元共混结构中的第三组分可显著影响器件的宏观输出性能，但其影响机制尚不明确。本项目以PTB7-Th:m-ITIC:PC71BM三元共混光伏体系为研究对象，以界面电荷产生及复合为切入点，通过研究第三组分含量与光电转换动力学间的关系，阐明影响三元共混聚合物光伏器件输出性能的光电转换机制。为此，本项目将综合运用稳态光谱、结构表征以及性能测试手段，研究器件输出性能、第三组分含量与界面电荷转移态的关联；通过时间分辨光谱技术，研究第三组分含量及器件工作条件对三元共混光伏体系界面电荷产生及复合动力学过程的影响；结合上述稳态和时间分辨的研究结果，阐明第三组分含量调控器件输出性能的影响机制。通过上述研究，揭示三元共混光伏器件输出性能与光电转换动力学的内在关系，为该类聚合物光伏的材料设计和器件性能优化提供理论依据和新思路。

探明三元聚合物光伏器件的光电转换动力学机理可为高效有机光伏器件设计提供新思路。本项目以PTB7-Th:m-ITIC:PC71BM、PM6:IT-4F:ITIC等三元共混光伏体系为研究对象，以从纯膜到共混膜、从二元共混到三元共混、从活性层到器件的研究思路，开展了三元聚合物光伏体系光电转换动力学机制的研究工作。课题研究所取得的重要结果包括：（1）探究了典型三元聚合物光伏体系各组分在纯膜状态下的激发态特性，揭示了聚合小分子受体薄膜中激发光子能量和激发光通量依赖的激发态弛豫路径;（2）探明了三元体系各界面电荷转移和能量转移的竞争机制，构建了通过稳态光谱定量分析界面电荷转移和能量转移占比的新方法，在非富勒烯界面模型体系中观察到了与给/受体界面能级差密切相关的电荷转移、能量转移以及电荷复合过程;（3）在活性层和器件实际工作层面，阐明了PTB7-Th:m-ITIC:PC71BM等三元光伏体系第三组分含量、器件输出性能以及界面电荷产生和复合间的内在关系。研究结果可为多元聚合物光伏的材料设计和器件性能优化提供理论依据和新思路。迄今，在ACS Appl. Mater. Interfaces、J. Phys. Chem. Lett.、J. Mater. Chem. C、J. Phys. Chem. C等期刊发表SCI论文16篇。