Fabrication of CuInS2 thin film by electrodeposition of Cu–In alloy

• CuInS1.5 thin film is fabricated by co-deposition of Cu–In alloy and sulfurization.
• Triethanolamine is adopted as complexing agent to suppress the reduction of Cu2+.
• C and O impurities are incorporated into the obtained CuInS1.5 thin films.
• Cu2In alloy layer is formed at electrodeposition potential of −1000 mV.
• The conversion efficiency can be improved further by depositing PbS particles.

CuInS2 thin films of chalcopyrite structure were fabricated on indium tin oxide substrates by electrochemical co-deposition of copper–indium alloy layers at 1 atm, followed by sulphurization. Co-deposition potential was determined according to voltammetric study. The effect of deposition potential, concentration of complexing agent, and heat treatment temperature on the morphology and crystal structure of the obtained thin films was examined. Then the influence of heat treatment on the optical and photoelectrochemical performance of CuInS2 thin films was studied. In the electrodeposition solution containing 5 mM CuCl2, 5 mM InCl3 and 0.2 M triethanolamine at pH of 4.0, Cu2In alloy layers were observed at the deposition potential of −1000 mV (vs. saturated calomel electrode). After sulfurization, chalcopyrite CuInS1.5 thin films with the impurity elements of C and O were obtained. Those thin films exhibited p-type semiconductor behavior with the bandgap of about 1.5 eV. The conversion efficiency can be improved further by depositing PbS particles on the thin films.