Low cost and non-toxic preparation of Cu2ZnSnS4 absorber material for thin film photovoltaics and studies its structural and thermal properties

Unlike Si Thin film solar cells have appealed scientific community due to direct band gap properties requiring less quantity of material. In thin film solar cells, CdTe and CIGS are prominent candidates with PCE 17% and 20%, respectively. Large scale production from CdTe and CIGS is limited due to unavailability of the elements (In, Te) and environmental concerns with toxic Cd. Cu₂ZnSnS₄ (CZTS) has emerged as a potential candidate in thin film photovoltaic due to its non-toxicity, low cost and economic availability of precursors. CZTS is a semiconductor with a direct bandgap of 1.5 eV and an absorption coefficient of 10⁴ cm-1. Conventional synthesis techniques are either energy intensive or use toxic chemicals. In this work, Cu₂ZnSnS₄ was successfully prepared by wet chemistry route using a non-toxic solvent. CZTS precursor solution was prepared in a mixture of water and ethanol using metal chlorides and Thiourea as source of sulfur. XRD analysis revealed that binary and ternary sulfide phases formed at 250 °C. However, by increasing temperature up to 300 °C, pure CZTS compound is formed with a change in lattice parameters. SEM studies of surface morphology and particle size analyses were carried out. Furthermore, thermal behavior of the as-fabricated powders is depicted using the thermogravimetric analysis. Spin coating technique was successfully applied for thin film formation on a soda lime glass substrate.