Fabrication of 3.01% power conversion efficient high-quality CZTS thin film solar cells by a green and simple sol-gel technique

Fine quality Cu₂ZnSnS₄ (CZTS) thin films were prepared by a non-toxic, simple and economical sol-gel and spin-coating technique. The CZTS thin films were prepared on Molybdenum coated soda lime glass substrates. The films were annealed at three different temperatures viz. 525, 550 and 575 °C under H₂S gas atmosphere to study the effect of annealing temperature on the morphological, structural, chemical, compositional, optical and photovoltaic properties of the CZTS thin films. The X-ray diffraction and Raman spectroscopy investigations on the CZTS thin films showed formation of the pure kesterite structure. The X-ray fluorescence studies demonstrated that all the CZTS thin films were nearly stoichiometric having Zn rich composition. All the annealed films were further subjected to fabrication of solar cells as an SLG/Mo/CZTS/CdS/i-ZnO/AZO/Al grid. The best solar cell showed a short-circuit current density of 14.57 mA/cm², open-circuit voltage of 513 mV, fill factor of 40% and power conversion efficiency of 3.01% under air mass 1.5 (100 mW/cm²) illumination.