ELECTRODEPOSITION OF COPPER-INDIUM ALLOY UNDER DIFFUSION-LIMITING CURRENT CONTROL

The aim of this work was to study a method of electrodeposition of sto ichiometric copper-indium alloy to be used as a precursor for obtainin g CuInSe2 by selenization. This compound represents one of the most pr omising materials in terms of low cost and high efficiency for the rea lization of large-area thin film solar cells for terrestrial applicati ons. However, to avoid the growth of secondary phases such as CuSe and In2Se3, the stoichiometry and morphology of the alloy have to be care fully controlled. We investigated the relationship between the ratio o f Cu2+ to In3+ in the solution and the metal ratio in the deposited fi lm. In order to avoid the use of complexing agents we chose to control the stoichiometry of the copper-indium alloys, electrodepositing them under diffusion-limiting current. Since the diffusion currents are, a s a first approximation, proportional to the concentrations, there is a simple relationship between the individual diffusion currents of the ions and the stoichiometry of the deposited alloy. Thus we can change the Cu-In content in the deposited film by controlling the ratio betw een the ions in the deposition bath.