染料敏化太阳能电池单离子全固态聚合物电解质的设计及机理研究

The conductivity of electrolyte, the diffusion coefficient of redox couple and the wetting and pore filling of porous TiO2 film are key factors in determining the conversion efficiency of all-solid-state dye-sensitized solar cells. In this program, the mono-ion transport all-solid-state polymer electrolyte is prepared by using in situ polymerization of alkyl-bis(imidazole)s with alkyl-bis(iodine)s, and employed to fabricate all-solid-state dye-sensitized solar cells. The mono-ion transport feature is favorable to increase the diffusion rate of redox couple in all-solid-state electrolyte. The polyiodides chains for Grotthuss bond exchange and 3D channel for ionic diffusion can form simultaneously in the as-prepared electrolyte by adjusting the component of the electrolyte, and then the conductivity of the electrolyte could be increased greatly. The wetting and pores filling of the TiO2 film by the all-solid-state electrolyte could be greatly improved by using in situ solidification of electrolyte and regulating the thickness and pore structure of TiO2 film. The conductivity mechanism of mono-ion all-solid-state polymer electrolyte is studied. The dependence of the physical and chemical properties of electrolyte on the electrolyte components and the influence of the electrolyte components on the photovoltaic performance of as-prepared cell are discussed. The mechanism and kinetics of the charge transfer at the interface of electrolyte and electrode are analyzed. The results obtained in this program may also provide a theoretical basis for further improving the photovoltaic performance of all-solid-state dye-sensitized solar cells.

提高全固态电解质的电导率和氧化还原对的传输速率、改善全固态电解质在二氧化钛多孔膜的渗透和界面接触是提高全固态染料敏化太阳能电池效率的关键。本项目设计烷基二咪唑与二碘代烷在二氧化钛多孔膜进行原位聚合制备新型单离子全固态聚合物电解质，并同时组装全固态染料敏化太阳能电池。电解质的单离子传导特性可有效提高氧化还原对的传输速率。通过调控电解质组成和各组份的结构，在电解质中同时形成快速进行Grotthuss键交换反应的多碘离子链和离子快速扩散的3D通道，从而大大提高全固态电解质的电导率。电解质的原位固化结合二氧化钛多孔膜厚度和微结构的调控可大大改善全固态电解质在二氧化钛多孔膜的渗透和界面接触。研究单离子全固态聚合物电解质的电导机制，研究电解质的组成、结构对其物理化学性能及所组装电池光电性能的影响，研究单离子全固态电解质/电极界面的电荷迁移机理和动力学过程，为进一步提高全固态电池的光电性能提供理论依据。

全固态电解质易于密封、稳定性好，因此全固态染料敏化太阳能电池受到广泛关注。但是全固态电解质的粘度大，因而电导率低，而且对光阳极TiO2多孔膜的浸润渗透性差。因此，全固态染料敏化太阳能电池的光电转换效率还偏低。提高全固态电解质的电导率、改善全固态电解质对光阳极TiO2多孔膜的浸润渗透和界面接触是提高全固态染料敏化太阳能电池的关键。本课题通过烷基二咪唑与二碘代烷间的原位聚合反应制备了新型单离子聚合物电解质，并同时组装了全固态染料敏化太阳能电池。通过热重分析、SEM、电化学阻抗谱等对所制备的单离子聚合物固态电解质进行了分析。通过光电流-电压曲线、暗电流测量、SEM、电化学阻抗谱等对所组装的全固态染料敏化太阳能电池的光电性能和电池内各界面的电荷转移进行了研究。原位固化使全固态电解质在TiO2多孔膜内具有较好的浸润渗透和界面接触，从而减少了界面的电子复合。通过调控单离子聚合物的结构和电解质的组成，聚合物主链上的咪唑环形成π-π堆积结构，从而在不加碘的情况下，在电解质内形成能够以Grotthuss键交换机理导电的多碘离子链，使所制备的单离子聚合物全固态电解质的电导率达到1.26 mS/cm。100mW/cm2光照下，单离子聚合物固态电解质组装的染料敏化太阳能电池的光电转换效率达到6.55%。当在电解质中加入碘，虽然电解质的电导率有所上升，但由于电解质/光阳极界面的电子复合增强，使所组装的全固态染料敏化太阳能电池的光电效率降低。另外，以CoS和含氮碳材料代替Pt制备了低价、高催化活性的对电极，所组装的染料敏化太阳能电池的光电性能与传统Pt对电极电池相当。