Study of composition reproducibility of electrochemically co-deposited CuInSe2 films onto ITO

CuInSe2 thin films were electrodeposited onto ITO substrates from aqueous solution containing 4.5 mM CuSO4, 10 mM In2(SO4)3 and 10 mM SeO2 isopotentionally and by two-step deposition technique — changing the deposition potential during the deposition process step-wise: from lower to higher and vice versa in the potential range of − 0.6 to − 1.0 V (vs. Ag/AgCl). Solution pH was varied from 1.3 to 1.9 at temperatures 293 and 313 K to clarify the region for co-deposition of In-rich CuInSe2 films on ITO with high composition reproducibility. Morphology and composition of CuInSe2 layers depended not only on deposition temperature and potential, but also on the direction of potential change in the case of two-step process. The potential change from lower negative values to higher ones resulted in layers with low adhesivity. Alternatively, from higher potential to lower potential, the homogeneous, well-structured, adhesive and smooth layers were deposited. Modifying deposition periods in a two-step process, the chemical composition of films can be tailored. At pH < 1.9 reproducibility of the film's composition was low. ITO electrodes were found not to be stable at pH < 1.9.