Tuning the band gap of Cu(In,Ga)Se2 thin films by simultaneous selenization/sulfurization

The simultaneous selenization/sulfurization is investigated to fabricate Cu(In, Ga)(Se,S)2 thin films in the H2S/H2Se/N2 hybrid gas, and the optical band gap of Cu(In, Ga)(Se,S)2 thin film is adjusted from 1.05 eV to 1.22 eV by varying the concentration ratio of H2S/H2Se. It is found that more S incorporates into the CIGSeS phase when the H2S concentration is increased, which widens the band gap of CIGSeS alloy. Furthermore, the through-film element profile of the CIGSeS films with different reaction time reveals that CIGSeS film is Ga-poor and S-poor during the initial reaction, and Ga and S are redistributed during the subsequent reaction with a joint of H2S and H2Se.