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

Thin films based on CuInSe 2 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 CuInSe 2 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 CuInSe 2 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 H 2Se/Ar, and then exposing these various partly selenized films to H 2S/Ar under identical conditions.