Fabrication of high-quality kesterite Cu_2ZnSnS_4 thin films deposited by an optimized sol-gel sulphurization technique for solar cells

摘要

Kesterite Cu_2ZnSnS_4 (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 × 10~(19) 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.