In this paper we have presented an in-depth study of effect of metallic precursor stacking order on the growth of the Cu 2 ZnSnS 4 (CZTS) thin films. The CZTS films were prepared by employing a two-step process comprising of sequential sputtering of the metal precursors followed by sulfurization. An optimized stacking sequence as well as growth mechanism for obtaining the single phase CZTS has been proposed based on the results of XRD, Raman, XPS, UV-Vis and electrical studies. A combination of Raman analysis and XPS has been carried out to confirm the CZTS phase formation and to detect any minor phases, if present. The occurrence of Raman modes at around 286 and 336 cm-1 for the Zn/Cu/Sn/Cu stack sulfurized at 500 o C indicated the existence of prominent Kesterite CZTS phase. The perfect homogeneous mixing of sequential precursors together with the elemental sulfur was observed in the case of sulfurized stack order of Zn/Cu/Sn/Cu, and which yielded single phase CZTS films, which and further confirmed by high resolution core level XPS measurements. Stack dependent micro structural features and elemental analysis were also carried out using FESEM attached to EDS. The p-type charge carriers as detected using hot-probe measurement technique and the band-gap energy of ~1.52 eV as estimated from the absorbance spectrum, suggested that the Zn/Cu/Sn/Cu stack order is most appropriate for realizing single phase CZTS growth using two step method.

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In this paper, we employed a simple and cost-effective thioglycolic acid (TGA) free hydrothermal method, based on thiourea hydrolysis of stannous chloride dihydrate [SnCl2.2H2O] at 160[Formula: see text]C–190[Formula: see text]C for 6[Formula: see text]h, for the synthesis of SnS nanoparticles. The effect of hydrothermal autoclave reaction temperature on various properties of SnS nanoparticles have been examined at length using X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy attached with EDAX (FE-SEM), transmission electron microscopy (TEM) and ultraviolet-visible (UV-Vis) spectroscopy. The results suggest that the crystallization of orthorhombic SnS nanoparticles, with size varying from 3[Formula: see text]nm to 5[Formula: see text]nm, formed at R[Formula: see text]C. Further, the formation of SnS phase was confirmed by an IR Sn-S characteristic bands around 2350[Formula: see text]cm[Formula: see text], 1041[Formula: see text]cm[Formula: see text] and 570[Formula: see text]cm[Formula: see text], and four distinguished Raman peaks at 95[Formula: see text]cm[Formula: see text], 160[Formula: see text]cm[Formula: see text], 189[Formula: see text]cm[Formula: see text] and 220[Formula: see text]cm[Formula: see text]. The mechanism for the formation of SnS nanoparticles have been proposed and discussed. The SnS nanoparticles have exhibited reaction temperature dependent morphological features like nanoflowers, nanoflakes, spherical nanoparticles and nanogranules. The absorbance studies indicated both strong direct and weak indirect allowed transitions for SnS nanoparticles and the associated band gaps were found to be 1.5[Formula: see text]eV and 1.19[Formula: see text]eV, respectively. The dual band gap combination of SnS would favor strong direct absorption of carriers and improved minority carrier life time due to indirect nature, which means the grown particles are suitable for ideal absorber material for solar cell applications.

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