Effect of sprayed volume on physical properties of Cu2FeSnS4 thin films and an efficient p-type Cu2FeSnS4/n-type F-doped SnO2 heterojunction

Abstract Quaternary chalcogenide Cu2FeSnS4 (CFTS) thin layers were successfully synthesized by a spray pyrolysis technique and deposited on glass substrates for different sprayed volumes (Vs = 300, 600, 900, and 1200 ml). Energy-dispersive X-ray (EDX) spectroscopy, scanning electron microscopy, X-ray diffraction (XRD), Raman spectroscopy, spectrophotometry, and Hall effect measurements were used to investigate, respectively, the chemical composition and the morphological, structural, optical, and electrical properties of CFTS thin films. XRD analysis and Raman spectroscopy revealed that the optimum growth of CFTS thin film occurred for Vs = 900 ml owing to the pure phase, good crystallinity, and maximum crystallite size estimated to be 62 nm. EDX analysis for Vs = 900 ml showed that the Cu/Fe/Sn/S stoichiometric ratio is close to the theoretical value of 2:1:1:4. The band gap and the electrical resistivity of the optimum film are 1.48 eV and 0.11 Ω cm, respectively. These experimental results allow us to consider CFTS thin film prepared with Vs = 900 ml as a promising absorber layer for solar cell applications. Furthermore, the optimum CFTS thin film exhibits good photocatalytic activity toward the degradation of methylene blue under sunlight irradiation. Moreover, a new heterojunction composed of CFTS and F-doped SnO2 was synthesized and studied. The photodegradation rate of methylene blue was 88%, which makes this heterojunction a promising alternative for removal of organic pollutants in wastewater treatment by photocatalysis.