Effects of Cu/In ratio of electrodeposited precursor on post-sulfurization process in fabricating quaternary CuIn(S,Se)2 thin films

This paper reports the analysis of S diffusion into electrodeposited CuInSe2 (CISe) precursors during post-sulfurization treatment at 500 °C in an Ar/H2S ambient. The characterizations of the sulfurized films by X-ray diffraction, grazing-incidence X-ray diffraction, Auger electron spectroscopy and micro-Raman spectroscopy allow the observation of the strong dependence of S incorporation into these films on the Cu/In ratio of the precursor. AES profiles reveal higher S content along the depth of Cu-rich film than Cu-poor film after sulfurization. Raman Scattering shows that copper sulfoselenides Cu–(Se,S) are only detected in Cu-rich samples. The re-crystallization of films during sulfurization was analyzed and it is presumed that quasi-liquid Cu–Se phases, which are related to Cu/In ratio of precursor, promote continuous incorporation of S into these films.