Suited growth parameters inducing type of conductivity conversions on chemical spray pyrolysis synthesized SnS thin films

Tin monosulfide (SnS) is a promising Cd-free candidate as absorber layer in Thin Film Solar Cell technology. In this work SnS thin films were synthesized by chemical spray pyrolysis (CSP) technique using a 0.2 M equimolar precursor solution of tin chloride and thiourea at substrate temperatures of 350, 370 and 390 °C and pressure for 0.5 and 1.0 kgf/cm2. Characterization of synthesized films was performed by X-ray diffraction, Raman spectroscopy, scanning electron and atomic force microscopy, transmission, reflection and absorption measurements, and electric characterization techniques. Films show an orthorhombic phase, p-type conductivity, a direct optical energy band gap of 1.3-1.7 eV and a high absorption coefficient (≥104/cm). In this work, we have found that the in-situ variation of the carrier gas pressure induced n-type electrical conductivity on SnS films, which will allow an in-situ serial fabrication of the SnS homojunction without the need of additional doping materials.