Structural control of porous nano-space in dye-sensitized TiO2 solar cells

Nanostructural effects in ruthenium dye-sensitized TiO2 solar cells were investigated by using all anatase TiO2 nanocrystallites as an electron transport layer, and by solidifying the organic liquid redox couple, I- /I-3(-), as a hole transport layer. All anatase TiO2 nanocrystallites (HyCOM-TiO2) were prepared by the method of direct hydrolysis of titanium alkoxide under quasi-supercritical conditions. The optically transparency of HyCOM-TiO2 films (16 mu m thickness) was found to be superior to those of P25-TiO2 films (11 mu m thickness), The modules using HyCOM-TiO2 films gave relatively efficient photo-energy conversion when compared with those of P25-TiO2 films. The unique characteristics of the films were attributed to the high crystallinity, the mono-dispersed nano-scale size, and the crystalline necking in the films. Solidification of liquid redox electrolytes was successfully achieved by using amino acid derivatives as low molecular weight gelators. The gelators caused smooth gelation of the liquid electrolytes in the porous nano-space of the modules without losing the redox hole transport activity of the redox electrolytes. Such homogeneous,gelation should contribute to the construction of quasi-solid-state dye-sensitized solar cells with respectable efficiency and stability.