Dye-Sensitized Solar Cells Based on Nanostructured Semiconductor Oxide Ceramics with Ultra-Thin Barrier Layers

Abstract

Nanostructured high band-gap oxide semiconductor ceramics are extensively investigated to understand their unique properties and applications in dye-sensitized solar cells, sensors, supercapacitors and other electronic and electrochemical devices. The unusual properties of these materials originate from large surface-area to bulk-volume ratio, quantum size effects and formation of space charge layers of dimensions comparable to the crystallite size in depletion of carriers. A prototype device demonstrating the unique properties of nanostructured semiconductor ceramics is the dye-sensitized solar cell. The original version of this device is based on TiO2 and other familiar stable oxides SnO2 and ZnO yield lower efficiencies owing to faster recombination. SnO2 admits faster electron transport because of the lower effective electron mass, but the same property enhances recombination. Ultra-thin barrier layers insulating stannates coated over the SnO2 crystallites by glazing with alkaline earth chlorides increases the efficiency from ∼1 to 6.6%.