Solid type dye-sensitized solar cell using polysaccharide containing redox electrolyte solution

The liquid of a dye-sensitized solar cell composed of a nanoporous titanium dioxide (TiO2) film and a bipyridine–Ru complex dye (N3 dye) was solidified by utilizing a tight and elastic solid polysaccharide (κ-carrageenan or agarose) containing excess liquid. The solid type cell exhibited similar characteristics and light-to-electricity conversion efficiency as a conventional liquid type cell. The electric resistance of the solid containing the solution of redox electrolytes (I−/I3−) was of the same order of magnitude as a liquid, and the charge transfer resistance on the electrode surface was even smaller for the solid than for the liquid. The increase of the polysaccharide solid hardness did not greatly affect the conversion efficiency. On exchanging the water of the polysaccharide solid with an organic medium solution containing redox electrolytes, the soaking time (from 1 to 3 h) and the repeated change to a fresh solution did not greatly affect the performance of the solid type cell. For both the solid and liquid type cells the thinner electrolyte layer gave a higher conversion efficiency. The investigation of both the solid and liquid type cells by alternating current impedance spectroscopy showed almost similar behavior in every step of the charge transfer event.