That is the question. All of the materials are expensive themselves (gallium, indium) or expensive to process ( silicon) - which means these cells will never sc

That is the question. All of the materials are expensive themselves (gallium, indium) or expensive to process ( silicon) - which means these cells will never scale and replace oil. Which is why dye-sensitized solar cells are such a promising alternative, despite their lower single module efficiencies of ~15% (20-30% for the expensive semiconductors discussed in OP). http://en.wikipedia.org/wiki/Dye-sensitized_solar_cell http://en.wikipedia.org/wiki/Dye-sensitized_solar_cell