Formation of p-type CuInS2 absorber layers via sulfurization of co-electrodeposited Cu–In precursors

Abstract

The electrodeposition of Cu–In alloy precursors with suitable stoichiometry and consisting mainly of intermetallic compounds, followed by sulfurization, is a promising method to form good quality CuInS₂ thin films. In this work, Cu–In precursors forming intermetallic compounds were electrodeposited from an acidic solution on Mo substrates at 50 °C and sulfurized to form p-type CuInS₂ absorber layers. We studied the crystal structure and compositional characteristics of films before and after sulfurization. Intermetallic compounds, namely Cu₁₁In₉ and Cu₉In₄, have been observed for precursor films suitable to form CuInS₂, and p-type CuInS₂ phase with small amounts of CuS was formed, showing the chalcopyrite and CuAu-type ordered phases for Cu/In ratios between 1.09–1.34. The carrier density was increased with increasing Cu/In ratio, but the photoelectrochemical response of the films was not directly related to this ratio. Film morphology has a critical influence on the photocurrent response. The highest photoelectrochemical current was achieved from compact and smooth precursors that were electrodeposited at −1.3 V while the lowest value was obtained with a rough dendritic precursor that was electrodeposited at −1.6 V.