Sulfurization in Gas Mixture of H2S and O2 for Growth of CuInS2 Thin Films

Abstract
We propose a new sulfurization process for the preparation of homogeneous CuInS2 films. The process was carried out in a gas mixture of H2S and O2 with varying O2/H2S ratios, using an InS/Cu/Na2O2/In stacked layer as the precursor. In this method, the decomposition of H2S is induced at low temperatures by O2 incorporation, thereby promoting the sulfurization of the precursor. Consequently, the serious problem of In metal segregation, which deteriorates the uniformity of CuInS2 films, is prevented. This method has realized the highest efficiency of Cu-poor CuInS2-based solar cells known to date.