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

CuInSe 2 thin films were electrodeposited onto ITO substrates from aqueous solution containing 4.5 mM CuSO 4 , 10 mM In 2 (SO 4 ) 3 and 10 mM SeO 2 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 CuInSe 2 films on ITO with high composition reproducibility. Morphology and composition of CuInSe 2 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.