Cu2ZnSnS4 films grown in one-step process by spray pyrolysis with improved properties

This work reports results of a study carried out to improve the optical, electrical and microstructural properties of Cu2ZnSnS4 (CZTS) films grown by spray pyrolysis in a one-step process using a precursor solution prepared dissolving thiourea and salts of Cu, Sn and Zn in a solvent constituted by a mixture of dimethyl sulfoxide (DMSO) and acetone. The improvement of the properties of the CZTS films was achieved through a parameters study performed by using an experimental design 23 face centered central composite design (FCCCD). The study revealed that substrate temperature (Ts), carrier gas pressure (Pg), spray pulse time (tsp) as well as their interaction are the parameters that most critically affect the above mentioned properties. Special emphasis was done on studying the influence of these parameters on the micro structural properties of the CZTS films using the XRD peak broadening method and Williamson-Hall equations, assuming the models UDM (uniform deformation model), USDM (uniform stress deformation model) and UDEDM (uniform deformation energy density model). Further, information regarding the influence of preparation conditions on the formation of structural defects was achieved through Urbach energy measurements.