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Attaining the optimal composition of Cu2ZnSnS4 (CZTS) thin film is a pre-requisite for photovoltaic application. Herein, the near-optimal composition of spray pyrolyzed CZTS thin film has been obtained by varying copper and thiourea molar concentrations in the precursor solution. Different characterization techniques such as x-ray diffraction (XRD), UV–vis spectroscopy, Scanning electron microscopy (SEM) and Energy-dispersive x-ray spectroscopy (EDS) have been employed to determine the changes in absorber layer properties. The CZTS thin films synthesized using Cu-0.016 M exhibits higher crystallinity with the direct band gap of 1.52 eV. Apart from that, the reduction of copper molar concentration in precursor solution minimizes the segregation of surface secondary phase. The variation of thiourea molar concentration facilities the growth of CZTS and reduces the formation of secondary phases. Besides that, the optical studies revealed that the increment in thiourea molar concentration leads to a broadening of band gap from 1.52 eV to 1.61 eV. The CZTS thin films synthesized using copper and thiourea molar concentrations of 0.016 M and 0.12 M showed appropriate absorber layer properties with near-optimal Cu-poor and Zn-rich ratio i.e., Cu/(Zn+Sn) = 0.81 and Zn/Sn = 1.26.

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The cubic-tin sulfide (SnS) compound material is optimal for the absorber layer in photovoltaic technology. In this study, the role of annealing temperature on the physical properties of cubic-SnS thin film has been determined. The spray pyrolyzed SnS thin films were post-annealed, using the chemical vapor deposition system, at the temperature range between 350 and 500 °C The annealed films have been analyzed using a comprehensive range of characterization techniques i.e., X-ray diffraction (XRD), Raman spectroscopy, UV–Vis spectroscopy, Photoluminescence spectroscopy (PL), Field-emission scanning electron microscopy (FESEM), Energy dispersive spectroscopy (EDS) and Hall measurements. The XRD results discovered the phase deterioration of cubic-SnS at higher annealing temperatures i.e., > 350 °C. Further, the Raman analysis confirmed the cubic-SnS phase deterioration, along with the formation of SnS2 and Sn2S3 secondary phases, at higher annealing temperatures. Besides that, a band gap in the range of 1.63–1.68 eV has been obtained for the SnS thin films. The films exhibit the near-band edge emission peak in the PL spectra. Moreover, the SEM micrographs show the needle-shaped grains, and their size and distribution were increased with respect to the enhancement in annealing temperature. A considerable amount of sulfur inclusion was observed in EDS analysis and the films annealed at 450° exhibit the near stoichiometric composition ratio of Sn/S = 1.01. The hall measurement studies showed resistivity, carrier concentration, and mobility of 29.4–376.5 Ω cm, 4.2 × 1014–3.0 × 1016 cm−3 and 13.1–66.1 cm2/Vs, respectively.

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