Optical and photoelectric properties of nanostructured SnS films obtained by spraying ink using a nanoparticle suspension

Abstract In this work, SnS films were prepared using spraying ink with a nanoparticle suspension. The average size of the synthesized nanoparticles was (18–20) nm. The structural, optical and photoelectric properties of SnS films were investigated using different characterization techniques. XRD and EDX results show that the investigated films exhibited an orthorhombic SnS phase with a composition close to the stoichiometry (C S /C Sn = 0.99) and low level of microdeformation ( ε = 1.8 × 10 −3 ). In addition, the hexagonal SnS 2 and tetragonal SnO 2 phases were also observed. The presence of SnS and SnS 2 phases is confirmed by Raman characteristics. The band gap of the SnS, SnS 2 , and SnO 2 phases was determined using the novel ACFD method based on the analysis of the spectra of the first derivative of the absorption coefficient, which directly determines the energy of both band-to-band optical transitions and transitions involving defect’s levels. These results correlate very well with data obtained using photoconductivity spectra. The nature of the electronic optical transitions as well as the type and energy position of various defect levels were established. It was shown that the energy of direct and indirect band-to-band optical transitions of SnS compound correspond to 1.72 eV and 1.16 eV, respectively. At the same time, the band gap of SnS 2 phase equal to 2.05 eV. The ionization energy of the acceptor (233 meV) and donor (100 meV) levels that determine the p- and n-type conductivity of SnS and SnS 2 compounds, respectively were defined. Due to its properties, SnS films may be suitable for the development of novel effective solar cells with SnS absorber layers.