Improved Cu2ZnSnS4 Solar Cell Performance by Multimetallic Stacked Nanolayers

Abstract

This study utilized a postdeposition sulfurization method to produce thin films of the Cu₂SnSnS₄ (CZTS) absorber layer. Initially, metal precursors were deposited onto a tin oxide-coated substrate through thermal evaporation. Subsequently, sulfurization occurred in a mixed environment of sulfur vapor and argon gas. The sulfurization temperature was set at 500°C for a duration of 30 min. During the sulfurization process, the facile evaporation of tin compounds could lead to a deviation in the atomic ratio within the absorber layer and potentially result in the attachment of secondary phases to the surface of the absorber layer. Therefore, this study employed a multilayered metal precursor structure (with a constant total thickness for each metal and nonmetal sulfides as precursors) for sulfurization. This method effectively suppressed the formation of secondary phases, including ZnS within the absorber layer and SnS₂ on the surface. From the quantification results, the ratio of ZnS to CZTS signal intensity decreased from 0.52 to 0, while the ratio of SnS₂ to CZTS signal intensity dropped from 1.2 to 0. Additionally, the efficiency increased to 2.79%. In summary, this research introduced a novel preparation method to enhance the quality of CZTS films. The modification to a multilayered metal precursor structure reduced the evaporation of tin compounds, consequently minimizing the generation of secondary phases.