Study of the stoichiometric ratio of one-step electrodeposited CuInSe ₂films on ITO/soda-lime glass

Copper indium diselenide (CuInSe₂) thin films were grown on indium-tin oxide (ITO)/soda-lime glass using a one-step cathodic electrodeposition process at potentials lower than -0.6 V vs SCE, and in the presence of a large excess of In³⁺. The source solution contained CuCl₂, InCl₃, and H₂SeO₃ complexed by citric acid. The concentration of InCl₃ in the electrochemical bath affected the structure, composition, stoichiometric ratio, and morphological properties of electrodeposited films. CuInSe₂ films with a chalcopyrite structure and quite good stoichiometry were directly electrodeposited from a solution of 20 mM InCl₃, 5 mM CuCl ₂, and 8 mM H₂SeO₃. Annealing of these CuInSe₂ films in the temperature range from 300°C to 500°C improves their crystallinity and increases their grain size. Good chalcopyrite CuInSe₂ films with a (112) preferential orientation suitable for the production of efficient solar cells are obtained after annealing at 500°C. The formation mechanism of the ternary CuInSe₂ compound during the electrodeposition process was discussed.