优化活性层薄膜的形貌是提高有机小分子太阳能电池性能的关键。本项目选择最具代表性的两类高效率的液晶给体小分子，即结构单元为BDT和DTS的小分子，将P3HT和P3BT及其纳米线引入小分子异质结体系中，作为模板，诱导给体小分子结晶，改善成膜性，并提供三维网络通道，提高垂直基底方向上的载流子传输。进一步在成膜过程中施加磁场作用，诱导给体小分子的取向，提高其结晶质量。通过同步辐射等先进表征技术，研究共轭聚合物及其纳米线存在下薄膜的微观形貌，包括给体小分子的结晶结构、结晶尺寸、PCBM聚集体的尺寸与分布、相尺度与纯度等，理解共轭聚合物及其纳米线调控小分子本体异质结形貌的机理。研究磁场强度、方向与作用时间对薄膜形貌，尤其是给体小分子取向与相纯度的影响，理解磁场调控给体小分子结晶以及小分子本体异质结形貌的机理。建立活性层薄膜的微观形貌与载流子迁移率和器件光伏性能之间的关联，制备高效太阳能电池。

It is the key to improve the photovoltaic properties of solar cells based on small molecules by optimizing the morphology of the active layer. The project will choose the two characteristic donor molecules showing of liquid crystalline properties and high power conversion efficiency (PCE) value, and the molecules contain the core of BDT and DTS units. The P3HT and P3BT as well as their nanowires will be incorporated into the small molecule heterojunction systems, serving as the template to induce the crystallization of donor molecules, improving the ability to form membranes. The nanowires will provide the three dimensional network pathways, facilitating the transporting of charge carriers vertical to the substrate. The magnetic field will be further applied during the film formation process, inducing the orientation of donor molecules and improving the quality of crystals. Based on the synchrotron radiation and other advanced characterization techniques, the morphology of the membranes in the presence of conjugated polymers and their nanowires will be deeply investigated in the nanometer scale, including the crystalline structure of donor molecules, crystal diameters, size and distribution of PCBM aggregates, domain size and purity, etc. The mechanism of morphology evolution of the small molecule bulk heterojunction optimized by conjugated polymers and their nanowires will be understood. The effect of the strength, direction and time of the magnetic field on the morphology change will be investigated, especially for the orientation of donor molecules and domain purity, in order to understand the mechanism of crystallization of donor molecules and morphology evolution of small molecule bulk heterojunction. The relationship between morphology of the active layer, charge transporting properties and photovoltaic properties of the devices will be analyzed, in order to fabricate the solar cells showing of high PCE values.