Optical and structural properties of CZTS thin films produced by electrodeposition

Abstract

Copper-zinc-tin sulfide (Cu2ZnSnS4 or CZTS), a quaternary compound, behaves as an intrinsic p-type semiconductor, making it an attractive, cost-effective and environmentally-friendly alternative as an absorber layer in photovoltaic cells. In this study, we deposited CZTS onto ITO conductive glass substrates using a single-step co-electrodeposition technique known as Cu-Zn-Sn-S (Co-Ed). The deposition process occurred at room temperature in an aqueous citrate electrolyte bath containing copper (II), zinc (II), tin (II), and sulfur. The deposition process was assisted by cyclic voltammetry to study the influence of cycle numbers, in particular 5, 10 and 15, on the structural and optical characteristics of sulfidation-free films. Scans were carried out at a rate of 20 mV/s in the potential range from −1.6 to 0 eV. CZTS thin films were characterized using X-ray diffraction (XRD) and UV–visible spectroscopy (UV–vis). The XRD results indicate the formation of CZTS kesterite, as evidenced by characteristic peaks. Likewise, optical analysis reveals an optical gap energy closely aligned with the optimum gap for the CZTS absorber layer (1.5 eV), making it suitable for photovoltaic applications.