Synthesis and characterization of Cu2FeSnS4 thin films prepared by electrochemical deposition

Quaternary compound Cu2FeSnS4 (CFTS) thin films, a potential absorber layer candidate in thin film solar cells, were successfully synthesized for the first time by electrochemical deposition method with a post-sulfurization treatment at 500 °C and 550 °C. The samples were analyzed by X-ray diffraction (XRD), Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible-near-infrared spectrophotometer (UV-vis-NIR spectrophotometer). XRD data and Raman spectra revealed that the CFTS thin films possess a stannite structure and the crystallinity of the samples was improved with the increasing sulfurization temperature. X-ray photoemission spectroscopy analysis of the four constituent elements indicated Cu(I), Fe(II), Sn(IV) and sulfide ions. The direct band gap values of samples with post-sulfurization treatment at 500 °C and 550 °C were evaluated to be 1.35 eV and 1.40 eV by UV-vis-NIR absorption spectra respectively, which show that CFTS is promising for photovoltaic applications.