Characterization of Cu2znsns4 (Czts) Thin Films Deposited by Potentiostatic Czt Elemental Deposition Followed by Chemical Bath in Sodium Sulphide Solution

Abstract

Copper indium gallium selenide (CIGS) is currently one of the most efficient thin film solar technologies. However, the scarcity and toxicity of its primary constituents (that is indium/gallium) present a challenge for future large scale production and sustainability. Replacement of indium and gallium by earth abundant and nontoxic zinc and tin to form Cu2ZnSnS4 (CZTS) presents a viable alternative. In this work, CZTS thin films deposited by low cost electrodeposition coupled with chemical bath techniques at room temperature and then annealed under sulphur rich atmosphere were investigated. Redox potentials were investigated using a standard electrochemical cell with three electrodes: RE-Ag|AgCl (saturated KCl), CE-Pt wire and WE- TCO coated glass was used. The reduction potential of Cu2+, Zn2+ and Sn4+ ions verses Ag/AgCl were, -0.47 V, -0.62 V and 0.63 V, respectively, verses Ag/AgCl. CZTS thin film quality determination was carried out using Raman spectroscopy which confirmed formation of quality CZTS film. Electrical characterization was carried out using four point probe instrument and the resistivity was in the order of ~10-4 Ω-cm. The optical characterization was done using UV-VIS-NIR spectrophotometer. The band gaps of the annealed CZTS film ranged from 1.45 eV to 1.94 eV with absorption coefficient of order ~104 cm-1 in the visible and near infrared range of the solar spectrum. Key words: Cu2ZnSnS4, stoichiometric, electrodeposition, chemical bath, reductionpotential