A study of kesterite Cu2ZnSn(Se,S)4 formation from sputtered Cu–Zn–Sn metal precursors by rapid thermal processing sulfo-selenization of the metal thin films

Cu–Zn–Sn intermetallic thin films were sputtered on Mo-coated soda-lime glass substrates from elemental targets. Samples representing a wide range of compositions around the 2:1:1 kesterite ratio of the Cu–Zn–Sn material system have been investigated. Crystalline phase content and chemical composition of the metal precursors were characterized by X-ray phase analysis and X-ray fluorescence. The metal precursor films were then processed into metal chalcogenides by rapid thermal processing in sulfur ambient with a maximum process temperature around 500 °C. Thin films were investigated by X-ray powder diffraction, X-ray fluorescence and Raman spectroscopy to identify their phase contents as a function of precursor composition and initial intermetallic crystalline phase content. Compositional regions of kesterite crystallization as well as remaining secondary chalcogenide phases were identified. Consequences of the obtained results for the thin film crystallization of Kesterite absorbers for solar cell fabrication by rapid thermal processing of metallic precursors will be discussed.

► The kesterite films were prepared by sulfo-selenization of intermetallic films.
► Intermetallic film compositions were adjusted having a broad compositional range.
► A precursor compositional deviation leads to resolvable phases.
► Kesterite forms from Cu2 − x(S,Se), Zn(S,Se) and Sn(S,Se)2.
► Kesterite Cu2ZnSn(S,Se)4 formation is proposed.