Original research articleAnnealing effect on structural and optical constants of SnS thin films for solar cells application

In this paper thin films of tin sulfide (SnS) were prepared by thermal evaporation method at room temperature on glass substrate and then annealed at different temperature with the aim of optimizing the structural and optical properties of the material for use in photovoltaic solar cell device. The structure and optical properties of SnS film has been studied in different range of annealing temperature from 100 °C to 400 °C with steps of 100 °C for 1 h. The films were analyzed by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX), scanning electron microscope (SEM) and optical absorption spectroscopy. X-ray diffraction studies shows that the structural properties of SnS film has been improved with increasing annealing temperature such that the film exhibits better crystallinity and the grain size has been increased, while film of lower annealing temperature exhibits poor crystalline with amorphous nature. The optical properties of the deposited films have been investigated by using UV-vis spectroscopy in the wavelength range of 300-800 nm. The optical constants such as the refractive index (n), extinction coefficient (k) and optical band gap have been calculated in different annealing temperature. The energy band gap in the range 1.60 eV-2.06 eV has been obtained for a film as-deposited which increases clearly with increasing annealing temperature. The refractive index and extinction coefficient both decrease notably with increasing annealing temperature. The obtained results were discussed can be improved to make suitability of SnS film as an absorber for the fabrication of low-cost and commercially viable solar cells.