In Situ Gelation of Electrolytes for Highly Efficient Gel-State Dye-Sensitized Solar Cells By using poly(acrylonitrile-co-vinyl acetate) as a gelator in an acetonitrile-based liquid electrolyte, an in situ gelation of the liquid electrolyte can be performed inside the mesoporous matrix of TiO(2) films. By introduction of TiO(2) nanoparticles as fillers of the gel-electrolyte, the energy conversion efficiency of a gel-state dye-sensitized solar cell can achieve a value higher than that of a liquid-state cell.