Quasi-solid dye sensitized solar cells solidified with chemically cross-linked gelators: Control of TiO2/gel electrolytes and counter Pt/gel electrolytes interfaces

Dye sensitised solar cells (DSSCs) were solidified with chemically cross-linked gelators without losing the performance of DSSCs before gelation. The electrolytes contain ionic liquids (1-methyl-3-propylimidazolium iodide) solidified with polyvinylpyridine and 1,2,4,5-tetra(bromomethyl)benzene. The solidification was carried out by baking the cells after the gel electrolyte precursors were injected in the cells. This brought about sufficient physical contacts between gel electrolytes and TiO2 nano-crystals in nano-porous TiO2 electrolytes. Small amount of water was added in order to decrease initial viscosities for ionic liquid type gel precursors, which makes it possible for the gel precursors to impregnate into nano-pores in TiO2 layers. The addition of water also has an advantage for decreasing charge transfer resistances between electrolytes and counter Pt. It was found that short circuit current (Jsc) and open crcuit voltage (Voc) increased much, when TiO2 layers with N3 dye were dipped in dilute carboxylic acid solutions and dried. Decreases in resistant of TiO2 layers were observed after the carboxylic acid treatments were carried out. This method is useful for increase in performance DSSC containing ionic liquid type electrolytes.