Effect of copper concentration and spray rate on the properties Cu2ZnSnS4 thin films deposited using spray pyrolysis

• We have prepared CZTS thin films using chemical spray pyrolysis and studied the effect of copper concentration and spray rate on the structural and opto-electronic properties.
• Optimum copper concentration for getting stoichiometric CZTS film with suitable band gap for photovoltaic applications could be found out.
• Band gap engineering of sprayed CZTS films could be achieved through variation in spray rate.

Polycrystalline Cu2ZnSnS4 (CZTS) thin films were prepared using chemical spray pyrolysis. We examined the influence of concentration of copper in spray solution and spray rate on the properties of the films. Choice of copper concentration in the precursor solution was found to have a pivotal role in adjusting composition, band gap and resistivity of sprayed CZTS thin films. Nearly stoichiometric CZTS thin films with desirable band gap were obtained by using copper concentration of 0.015 M. Spray rate also has crucial role in adjusting properties like band gap of the films. Higher spray rates resulted in rougher films with secondary phases of copper sulfide. Secondary phases were also observed at low spray rate of 2 ml/min. Good films without any secondary phases and having band gap of 1.5 eV were obtained at the spray rate of 6 ml/min.