EFFECT OF pH ON THE ELECTRODEPOSITION OF Cu(In, Al)Se2 FROM AQUEOUS SOLUTION IN PRESENCE OF CITRIC ACID AS COMPLEXING AGENT

Abstract

Effect of pH on the one-step electrodeposition of Cu ( In , Al ) Se 2 chalcopyrite layer in the presence of citric acid has been investigated by applying different electrochemical and characterization techniques. It has been observed that at pH of 1.5, nanocrystalline phase of chalcopyrite and small amount of binary phase of Cu 2 Se with overall composition of Cu 0.91 In 0.32 Al 0.39 Se 2 have been deposited. On the other hand, at pH of 4, the film composition changed to Cu 1.9 In 0.05 Al 0.21 Se 2 and an additional binary phase of copper selenide ( CuSe ) has also been formed. Morphological investigation illustrated that smooth and compact layer with fine spherical particles having the size of ~20 nm has been obtained at pH of 1.5 whereas mixture of planar and spherical particles with size of 450–550 nm have been formed at pH of 4. In alkaline environment (pH~9), the deposition current has been noticeably decreased and no deposition occurred due to the formation of a stable complex of citric acid with metal ions. The mechanism of citric acid interaction with metal ions at different pH has also been studied by cyclic voltammetry measurement.