Polymer electrolytes and adapted mesoporous TiO2 for Solid State Dye Sensitized Solar

Dye-sensitized solar cells (DSSC) have attracted a great attention due to their low production cost and high photo-conversion efficiencies since a new type of dye-sensitized solar cell has been reported by Grätzel [1,2]. The electrolytes are one of the key components and their properties have much effect on the conversion efficiencies. An electrolyte containing a suitable redox couple plays a very important role in determining the photovoltaic characteristics and durability of DSSC. Although there is the inherent drawback of the cell due to the volatility and possible leakage problem of liquid electrolytes during the long-term out-door operation. Numerous efforts have been made to overcome this problem by replacing the liquid electrolytes with solid or quasi-solid state electrolytes composed of various polymers [3] and room temperature ionic liquids [4]. In this work, we report a new quasi-solid state polymer electrolyte based on polysiloxane consisting of imidazolium exhibiting higher ionic conductivity, good chemical, thermal and electrochemical stabilities. Three types of polymer electrolytes based on polysiloxane grafted with different ratio of imidazolium moieties and ionic liquids have been synthesized and characterized. Increasing the proportion of imidazolium moieties in polysiloxane increased the conductivity and viscosity of the polymer electrolyte respectively. The thermal stability of the polymer electrolytes is determined by thermogravimetric analysis. The porosity of the TiO2 photoanode plays a crucial role due to the requirement of excellent pore filling by the solid state electrolyte to ensure optimal interface. Therefore, TiO2 thin films with regular and large pores, designed for optimal electrolyte impregnation will be prepared using templating-assisted dip-coating methods. The objective of the present work is to develop in parallel the best formulation of polymer-based electrolyte and a highly porous TiO2 photo anode. The performances of those combined components will be evaluated in assembled DSSC, with commercial dyes and transparent conductive glasses.
[1] M. Grätzel, Journal of Photochemistry and Photobiology C 4, 2003, 145.
[2] A. Hagfeldt, M. Grätzel, Accounts of Chemical Research 33, 2000, 269.
[3] J. Wu, Z. Lan, J. Lin, M. Huang, S. Hao, T. Sato, S. Yin, Advanced Materials 19, 2007, 4006.
[4] M.C. Kroon, W. Buijs, C.J. Peters, G.J. Witkamp, Green Chemistry 8, 2006, 241.