Effects of Cu2S sintering aid on the formation of CuInS2 coatings from single crystal Cu2In2O5 nanoparticles

This article reports the sulfurization of single crystalline Cu2In2O5 nanoparticles (NPs) for the formation of CuInS2 (CIS) coatings. Cu2In2O5 NPs were synthesized using a chemical route. Thus formed NPs were applied to Mo-coated glass substrate by a doctor-blading technique. After the doctor-blading, coatings were sulfurized under 500 torr of H2S at various temperatures. Selected doctor-bladed samples were heat treated at 430 °C in air for 30 min for the removal of carbon residual prior to the sulfurization. During the sulfurization, Cu2S (melting point 435 °C) was used as the sintering aid. The weight ratio of Cu2S to Cu2In2O5 was varied. The effect of Cu2S on the CIS crystalline structure was explored using Raman analysis. It was found that Cu2S not only improves the sintering but also promotes the formation of desired CIS-chalcopyrite structure and reduces the impurity phase in the resulting CIS coatings.