Towards phase pure Kesterite Cu2ZnSnS4 thin films via Cu-Zn-Sn electrodeposition under a variable applied potential

This work reports on the synthesis of pure Kesterite Cu₂ZnSnS₄ films by sulfurization of electrodeposited Cu-Zn-Sn precursor by means of a variable applied potential. Our study highlights the effect of using a variable potential during the film preparation on the properties of CZTS deposited films. The phase purity and crystal quality of CZTS films were investigated using XRD and Raman analyses. All films show distinct diffraction peaks of the pure phase of CZTS with Kesterite structure. As a signature of highly pure crystalline films of CZTS Kesterite phase, Raman spectroscopy technique shows the principal CZTS Raman characteristic peaks with a strong intensity at 337.9 cm⁻¹ of A-symmetry vibrational mode of sulfur atom in the CZTS Kesterite structure. Moreover, the chemical composition of the CZTS films could be controlled by changing the deposition process. The cyclic and the reverse sweep voltammetry approaches can be used to obtain the CZTS films with the suitable composition ratios. The deposited films exhibit a suitable photovoltaic bandgap semiconductor in the range of 1.52–1.57 eV. The relaxation process in deposited samples has been investigated using the electrical impedance spectroscopy analysis.