Effect of substrate temperature on physical properties of Cu2FeSnS4 thin films for photocatalysis applications

Quaternary chalcogenide Cu2FeSnS4 (CFTS) thin layers have been grown by spray pyrolysis technique on glass substrates using different substrate temperatures (T-s = 160, 200, 240 and 280 degrees C). Physical properties of CFTS thin films were investigated by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), spectrophotometer and Hall Effect. All results suggest that CFTS thin film synthesized at T-s = 240 degrees C has the best physical properties. XRD indicates an enhancement of crystalline quality of stannite CFTS elaborated at T-s = 240 degrees C with a maximum grain size about 45 nm and Raman spectroscopy confirms the purity phase of optimum sample. At T-s = 240 degrees C, atomic ratios of Cu/Fe/Sn/S were close to the theoretical ratios 2/1/1/4 and SEM images illustrates that the surface of the film is covered from a large number of micro-aggregates with spherical form. It is found that energy band gap and absorption coefficient values were about 1.46 eV and 9.8 10(4) cm(-1) respectively at T-s = 240 degrees C. Hall Effect measurements revealed that electrical resistivity of optimum sample decreased to 0.18 Omega cm. Thus, all experimental results demonstrate that CFTS thin film grown at T-s = 240 degrees C can be considered as a promising absorber material in solar cell devices. A higher photodegradation rate of MB was about 81% under sun light for 4 h which indicates that optimum CFTS thin film grown at T-s = 240 degrees C would be a cheaper alternative catalyst to replace TiO2 in photocatalysis applications.