全聚合物体系分子链缠结行为与薄膜共混相结构调控

The morphology of active layer in organic solar cells is closely related with the device photophysical process. With the construction of three-phase morphological model in fullerene-containing blend systems, the positive influence of mixed phase on the excitons dissociation process has been confirmed, which provides a new guidance to control the microstructure of active layer and optimize the device performance. However, compared to fullerene-containing blend systems, the important mixed phase in all-polymer blend films is difficult in characterization due to their similar material properties; the complicated molecular chain entanglement behaviors make the content of mixed phase difficult to tune, which inhibits the further improvement of device performance. This proposal intends to carefully characterize the mixed phase in all-polymer blend films with Resonant Soft X-ray Scattering (RSoXS), adjust polymer chain entangled behaviors in the solution state and film drying process by synergetic control of the thermodynamic and kinetic process parameters, which aims to optimize the film content of mixed phase, and then construct the relationship between mixed phase and excitons dissociation/charge carriers transport process. This study paves a pathway to better understand the effect of detailed film structure on device physical process, and provides a new method to further improve the device performance by morphological optimization for all-polymer solar cells.

有机太阳能电池的活性层形貌与器件的光物理过程密切相关。随着富勒烯体系三相形貌模型的建立，共混相区对激子分离过程的积极作用得到确立，为活性层微观形貌调控和器件性能优化提供了新的切入点。然而，与富勒烯共混体系相比，全聚合物薄膜的给受体性质较为接近，导致共混相结构更加难于表征；聚合物分子之间复杂的链缠结状态使得薄膜的共混相含量难于调控，严重限制此类体系器件性能的进一步提升。本项目针对以上问题，提出采用共振软X射线等手段对全聚合物薄膜的共混相结构进行精确表征，通过协同调节热力学和动力学等加工参数，改善溶液中不同分子链缠结形态的含量以及成膜阶段的分子链缠结/解缠结动态过程，对全聚合物薄膜的共混相含量进行优化，并建立激子分离及载流子传输过程与共混相的内在关联。本项目的研究为深入理解活性层的精细结构与器件物理过程提供依据，并对通过改善活性层形貌进一步提高全聚合物体系器件性能提供了新思路。

有机太阳能电池的活性层形貌与器件性能密切相关。构筑有利于电荷分离和传输的相分离形貌、掌握形貌的精确表征方法与演化机理、建立形貌与器件物理过程的关联对提升有机太阳能电池的性能意义重大。然而，目前对于高效有机太阳能电池体系的形貌调控规律还未完全掌握，特别是对于具有多尺度相分离结构的共混体系而言，很难实现复杂形貌的精确表征，严重阻碍了器件性能的进一步提升。针对以上问题，本项目（1）通过调节组分相互作用、溶剂体系选择以及顺序刮涂手段实现了共混体系热力学状态和成膜动力学过程的改善，进而优化薄膜共混相、结晶性、相区尺寸等形貌参数；（2）利用多种测试手段对薄膜形貌进行了精确表征，揭示了活性层薄膜多级相分离形貌演化的内在机理；（3）通过建立薄膜形貌参数与激子分离、电荷复合、载流子迁移等物理过程的关系，实现了有机太阳能电池器件性能的提升，成功的将多个体系的性能提升20%以上。在项目的资助下，本项目研究人员在Advanced Materials, Advanced Energy Materials, ACS Energy Letters等杂志发表研究论文16篇，参加国内外会议4次，合作培养硕士研究生3人。本项目的研究成果对于揭示活性层形貌与器件性能之间的内在关联具有重要意义，对基于溶液法加工的有机太阳能电池器件性能的提升具有指导作用，并为此类电池的商业化应用奠定基础。