Band-gap engineering in CuIn(Se,S)2 absorbers for solar cells

Thin films based on CuInSe2 have become very successful as absorber layers for solar cells. It is only in the recent past that gallium (Ga) and sulfur (S) were incorporated into CuInSe2 in order to increase the energy band gap of the film to an optimum value with the ultimate aim of producing more efficient devices. This paper focuses on the incorporation of S into partly selenized CuInSe2 films in order to produce CuIn(Se,S)2 films with varying S/Se+S ratios, resulting in different band-gap energies. This was achieved by varying the conditions when selenizing Cu/In alloys in H2Se/Ar, and then exposing these various partly selenized films to H2S/Ar under identical conditions.