In situ formation of continuous charge transfer pathways for highly efficient, solvent-free, polymer electrolyte-based dye-sensitized solar cells

For the fabrication of highly efficient all-solid-state dye-sensitized solar cells, a full coverage of electrolyte on dye/TiO₂ surface and a continuous electrolyte route from dye/TiO₂ surface to counter electrode are the most important issues, which depend heavily on the infiltration and precipitation behavior of solid electrolyte into porous photoanode. In this paper, an important experimental strategy, fast evaporation of the solvent at 80 °C under a low pressure, was explored for the first time to create in situ continuous charge transfer pathways after the infiltration of polymer electrolyte solution into a dual-porous TiO₂ film created by vacuum cold spraying. It was found that with the novel strategy very good electrolyte coverage could be realized on the dye/TiO₂ surface, and continuous electrolyte fibers could be developed in the sub-micro-pores of the dual-porous TiO₂ film, which could serve as a highway for fast electron transport between counter electrode and photoanode. As a result, a very high photo-to-electric energy conversion efficiency was demonstrated by the solvent-free polymer electrolyte solar cell.