Hydrothermally synthesized nanocrystalline photoactive SnS2 thin films: effect of surface directing agents

Abstract

In the present work, we have synthesized tin disulphide (SnS₂) thin films via a facile, low cost, single-step hydrothermal route using various surface directing agents. The SnS₂ thin films were characterized for their optical, structural and morphological properties. The optical study illustrated a direct allowed type of optical transition with a bandgap in the range of 1.78 to 2.03 eV. Morphological study demonstrated the formation of hierarchical nutshell surface morphologies, when using different surfactants, having higher surface-to-volume ratios for better light absorption. The structural study revealed that nanocrystalline SnS₂ thin films were formed with a pure hexagonal crystal structure with crystallite size ranging between 12.24 and 19.79 nm. Compositional analysis confirmed the formation of pure and stoichiometric SnS₂ thin films. Finally, we carefully analyzed the photoresponse properties of the as synthesized and surfactant-assisted SnS₂ thin films with the help of a standard two-electrode system on an electrochemical workstation where SnS₂ thin films acted as the working electrode and graphite acted as the counter electrode. Photocurrent (J_sc) was enhanced with the use of the surface directing agents from 0.24 to 0.96 mA cm² allied with a photovoltage (V_oc) from 416 to 610.2 mV. The highest photoelectric conversion efficiency was obtained for the Triton X-100 assisted SnS₂ photoanode and it was 0.83%. EIS performance of SnS₂ thin films synthesized with surfactants demonstrated reduced charge transfer resistance (R_ct), which supports the PEC (photoelectrochemical) performance.