Microstructure evolution of CuInSe2 thin films prepared by single-bath electrodeposition

The composition and the microstructure evolutions of CuInSe₂ thin films under single-bath electrodeposition processes were investigated. It was found that the film composition was mainly determined by the Se⁴⁺]/Cu²⁺] ratios in solution, but the film microstructure is strongly dependent on the initial concentrations of Se⁴⁺, Cu²⁺, and In³⁺ precursors. Higher initial concentrations of Cu²⁺ and In³⁺ in solution are beneficial for the fabrication of compact CuInSe₂ thin films with highly crystallized and large grain sized chalcopyrite phase. The microstructure evolution suggests that prior adsorption and reduction of Cu²⁺ ions and the formation of Cu₂Se compound on the substrate can promote the nucleation, growth, and coarsening of CuInSe₂ crystal to form a high quality thin film during the electrodeposition processes.