SnS films for photovoltaic applications: Physical investigations on sprayed SnxSy films

Thin films of tin sulphide (SnxSy) have been deposited on antimony-doped tin oxide-coated glass substrates using spray pyrolysis. The depositions were made using 0.1 M equimolar solutions of tin chloride and thiourea at different substrate temperatures varied in the range 100-450 °C. The physical properties of the films were studied using EDAX, XRD, SEM, AFM, van der Pauw method and spectrophotometry. The obtained results were discussed in the view of testing the suitability of SnS films as an absorber for the fabrication of photovoltaic devices. The films formed for temperatures of 300-375 °C were nearly stoichiometric (Sn/S=1.03), single phase (SnS) and showed a strong (1 1 1) preferred orientation with an average grain size of 0.37 μm. These single-phase films exhibited p-type conductivity with an average electrical resistivity of 30 Ω cm and a net carrier concentration of 2×1015 cm−3. These layers had a direct energy band gap of ∼1.32 eV with an absorption coefficient of ∼105 cm−2 above the fundamental absorption edge. The films deposited at temperatures <300 °C and >375 °C deviated from stoichiometry and additional phases were found to be present.