Electrochemical Synthesis of CuIn ( Se , S ) 2 Layer for Thin-Film Solar Cell with a Superstrate Configuration

Abstract

Copper indium diselenide thin films were grown on a fluorine-doped tin oxide (FTO) glass substrate covered with a thin layer of cadmium sulfide (CdS) by an electrodeposition method. The annealing of the films in a sulfur atmosphere resulted in a partial replacement of selenium with sulfur to form solid solutions. Structural characterizations of the annealed samples by using X-ray diffraction, energy-diffused X-ray analysis, and UV/visible/near-infrared absorption spectra revealed that the sulfur contents and the photoabsorption onsets strongly depended on the annealing temperature. The performance of superstrate-type solar cells was highest when the layer was annealed at in a sulfur atmosphere. A capacitance–voltage analysis of the junctions showed that the hole density in was increased by annealing at a high temperature, contributing to the improvement in the photocurrent. However, annealing at a high temperature led to the interdiffusion of CdS into the layer, resulting in the lowering of the solar cell performance. As a result of the trade-off between these factors, annealing at gave the best result for films made by the electrodeposition method.