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The growth of Cu2ZnSnS4 thin films was optimized via sulfurization free chemical spray pyrolysis technique. The sulfate based precursors were used to prepare the CZTS films with varying sulfur contents ranging from 0.08 to 0.12 M to maintain the stoichiometric and avoid sulfurization or H2S gas. The formation of secondary phases on the CZTS films was minimized by controlling the sulfur concentrations with the 2- methoxyethanol solvent. The CZTS kesterite structure with preferential orientation along (112) plane was confirmed by X-Ray diffraction at the sulfur content of 0.12 M. From the Raman analysis, we observed that the addition of the higher sulfur concentration to the precursor solution resulted in a pure phase CZTS peak at 336 cm−1 and reduces the secondary phase segregation. Scanning electron microscopy confirms that higher sulfur concentrations facilitate the growth of CZTS films with larger grain size and achieved Cu-poor and Zn-rich compositions for 0.12 M sulfur concentration from energy dispersive spectra. The UV analysis revealed the maximum absorption peak in the visible region with increasing sulfur concentration and the measurement of the Hall effect affirmed p-type conductivity with carrier concentrations ranging from 1014 to 1016 cm−3 as sulfur concentration increased. The charge transport property of the deposited films was characterized by electrochemical impedance spectroscopy where higher sulfur concentrations resulted in lower internal charge transfer resistance, which is the ideal absorber layer in thin film photovoltaic cells. [ABSTRACT FROM AUTHOR]

Cost effective photovoltaic Cu2ZnSnS4 (CZTS) nanomaterials with kesterite crystal phase were synthesized using a facile solvothermal method. Here ethylene glycol was the solvent and Polyvinylpyrrolidone (PVP) used as capping agent. The obtained CZTS nanoparticles were characterized by means of suitable analytical techniques such as X-ray powder diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Raman Spectroscopy, Ultraviolet- Visible (UV-Vis) Spectrometer and Photoluminescence (PL) respectively. The XRD results showed that the obtained sample presented as kesterite crystallinity with (112), (200), (220) and (312) planes of the CZTS nanoparticles and the average crystallite size was about 5.7 nm. The morphological investigation results given by the FESEM revealed that the average particle size of the sample was around 129 to160 nm. In addition, the optical observation suggested by both the absorption of UV-Vis and emission spectra of PL showed that the CZTS nanoparticles produced by this solvothermal method has the direct band gap energy within the range of 1.49 to 1.53 eV, which is near the optimal value and it is a dynamic absorber material for the efficient photovoltaic application. [ABSTRACT FROM AUTHOR]