Comprehensive optical studies on SnS layers synthesized by chemical bath deposition

• SnS absorber layers were grown by chemical bath deposition.
• The growth mechanism for the formation of SnS layer was analyzed.
• Band gap of the SnS layers was determined from the differential reflectance.
• Strength of inter-band optical transitions was measured.
• Resistivity, mobility and density of SnS layers were estimated using optical data.

A simple non-vacuum and cost effective wet chemical technique, chemical bath deposition was used to prepare tin sulphide (SnS) layers on glass substrates. The layers were formed by varying bath temperature in the range, 40–80 °C, keeping other deposition parameters as constant. An exhaustive investigation on their optical properties with bath temperature was made using the transmittance and reflectance measurements. The absorption coefficient was evaluated from the optical transmittance data utilizing Lambert’s principle and is >104 cm−1 for all the as-prepared layers. The energy band gap of the layers was determined from the differential reflectance spectra that varied from 1.41 eV to 1.30 eV. Consequently, refractive index and extinction coefficient were obtained from Pankov relations and dispersion constants were calculated using Wemple–Didomenico method. In addition, other optical parameters such as the optical conductivity, dielectric constants, dissipation factor, high frequency dielectric constant and relaxation time were also calculated. Finally electrical parameters such as resistivity, carrier mobility and carrier density of as-prepared layers were estimated using optical data. A detailed analysis of the dependence of all above mentioned parameters on bath temperature is reported and discussed for a clean understanding of electronic characteristics of SnS layers.