Microstructural and optical characterization of CZTS thin films deposited in one step by spray pyrolysis

This work describes a route to grow single phase Cu₂ZnSnS₄ (CZTS) thin films in one step process using spray pyrolysis technique, followed by annealing at 773K in nitrogen-atmosphere. The precursor solution was prepared dissolving metallic salts and thiourea in dimethyl sulfoxide (DMSO). The effect of film thickness and annealing temperature on the phases formed in the CZTS films, as well as its optical and structural properties have been studied through transmittance, Urbach energy (Eu), X-ray diffraction (XRD) and Raman spectroscopy measurements. Raman scattering analysis allowed identifying symmetric vibrational modes associated to different phases. It was found that single phase CZTS films with tetragonal structure are formed when thin films of thickness greater than or equal to 1 μm are subjected to annealing at 773K during 30 min, in a chamber maintained at nitrogen partial pressure of 20 mBar. This type of CZTS films have low Urbach energy, indicating that are characterized by a low density of structural defects.