Energy and time-efficient synthesis of oxide semiconductors for solar photovoltaic and photocatalytic applications

Abstract

Oxide semiconductors are eminently attractive candidates as the active material in solar photovoltaic or photocatalysis systems both from inherent cost and photochemical stability considerations. The prototype oxide is TiO2; however, it has too large an energy band gap, Eg (3.0-3.2 eV) for efficiently harnessing solar energy. Two key considerations in terms of process economics are (a) the abundance of the component elements in the material and their environmental compatibility and (b) the energy payback time associated with the semiconductor material itself and the solar cell. That is, the shorter the payback time, the better is the overall process economics. Thus lowering the energy requirements for the semiconductor synthesis step becomes a critical factor in the overall process economics. Combustion synthesis and electrosynthesis are two process candidates for semiconductor preparation that meet the criteria for energy and time efficiency. This paper describes recent examples of the use of these methods in our laboratories for the energy- and time-efficient synthesis of inorganic oxide semiconductors.