Effect of initial bath condition and post-annealing on co-electrodeposition of Cu2ZnSnS4

Polycrystalline Cu2ZnSnS4 thin films were electrodeposited on Mo and F:SnO2/Glass substrates at room temperature by single step method from an aqueous solution containing tri-sodium citrate and tartaric acid as complexing and pH controlling agents, respectively. The thermostatic bath deposition was carried out at room temperature (25 °C) with lower and higher initial concentrations of Cu, Zn, Sn and S- precursors in order to investigate the effect of stoichiometric deviations on their phase compositions and optoelectronic properties. As-prepared samples were photoactive as revealed by photo electrochemical (PEC) measurement, however, it showed the films were mixture of p- and n-type semiconducting phases. The post-annealing treatment was carried out in the temperature range 400-600 °C in an Ar-atmosphere to improve the CZTS phase composition and crystallinity of the film. The kesterite Cu2ZnSnS4 phase with preferred orientation along the (112) crystal direction grew to greater extent upon Ar-annealing at 500 °C associated with an improvement in the optical band gap. The PEC cells made from the annealed film showed an enhanced photocurrent response with p-type conductivity.