Fabrication of high-quality kesterite Cu2ZnSnS4 thin films deposited by an optimized sol–gel sulphurization technique for solar cells

Kesterite Cu₂ZnSnS₄ (CZTS) thin films were prepared by spin-coating deposition of sol–gel precursor followed by optimized sulphurization via custom-made home-built sulphurization setup. The effects of sulphurization on the structural, morphological, optical and electrical properties of CZTS thin films were investigated. X-ray diffraction and Raman spectroscopy studies revealed that the sulphurized CZTS thin films have a polycrystalline nature with a kesterite phase and the crystallite size of sulphurized CZTS thin film is higher as compare to as-synthesized CZTS thin films. The direct optical bandgap of sulphurized CZTS thin film is found to be 1.5 eV. Hall measurement indicates that the sulphurized CZTS thin films have p-type conductivity with charge carrier concentration of 9.47 × 10¹⁹ cm⁻³. Finally, a thin film solar cell was fabricated with the configuration—SLG/FTO/CdS/CZTS/Al. A photoelectric conversion efficiency of 1.5% was achieved with an open-circuit voltage of 0.32 V and a short-circuit current density of 11.9 mA cm⁻². These findings clearly show that quality of CZTS samples and photovoltaic performance could be effectively improved by an optimized sol–gel sulphurization process.