PHOTOVOLTAIC PERFORMANCE OF INJECTION SOLAR-CELLS AND OTHER APPLICATIONS OF NANOCRYSTALLINE OXIDE LAYERS

The direct conversion of sunlight to electricity via photoelectrochemi cal solar cells is an attractive option that has been pursued for near ly two decades in several laboratories. In this paper, we review the p rinciples and performance features of very efficient solar cells that are being developed in our laboratories. These are based on the concep t of dye-sensitization of wide bandgap semiconductors used in the form of mesoporous nanocrystalline membrane-type films. The key feature is charge injection from the excited state of an anchored dye to the con duction band of an oxide semiconductor such as TiO2. In the use of the semiconductor in the form of high surface area, highly porous film of fers several unique advantages: monomeric distribution of a large quan tity of the dye in a compact (few micron thick) him, efficient charge collection and drastic inhibition of charge recombination ('capture of charge carriers by oxidized dye'). Near quantitative efficiency for c harge collection for monochromatic light excitation gives rise to sunl ight conversion efficiency in the range of 8-10% This has led to fruit ful collaboration with several industrial partners. Possible applicati ons and commercialization of these solar cells and also other practica l applications of nanosized films are briefly outlined.