Non-vacuum methods for formation of Cu(In, Ga)(Se, S)₂ thin film photovoltaic absorbers

Polycrystalline thin films of copper indium diselenide and its alloys with gallium and sulphur (CIGS) have proven to be suitable for use as absorbers in high-efficiency solar cells. Record efficiency devices of 20% power conversion efficiency have been produced by co-evaporation of the elements under high vacuum. However, non-vacuum methods for absorber deposition promise significantly lower capital expenditure and reduced materials costs, and have been used to produce devices with efficiencies of up to 14%. Such efficiencies are already high enough for commercial up-scaling to be considered and several companies are now trying to develop products based on non-vacuum deposited CIGS absorbers. This article will review the wide range of non-vacuum techniques that have been used to deposit CIGS thin films, highlighting the state of the art and efforts towards commercialization. Copyright © 2009 John Wiley & Sons, Ltd.