Growth of SnS thin films by co-evaporation and sulfurization for use as absorber layers in solar cells

Tin sulfide thin films were grown by co-evaporation on soda-lime glass substrates. The synthesis was performed at different substrate temperatures between 200 °C and 400 °C at a growth rate of 6 Å/s, while adjusting the deposition time in order to obtain film thicknesses above 1500 nm. After evaporation, the samples were heated at 400 °C and 500 °C in sulfur atmosphere during 1 h. The evolution of the morphological, structural, optical and electrical properties has been analyzed as a function of the substrate temperature and the subsequent annealing. In the as-grown samples obtained at low temperatures, Sn tetragonal phase has been observed by XRD. By increasing the temperature up to 350 °C, the SnS phase started to form, the formation being completed at 400 °C. After sulfur annealing at 400 °C, all the samples evolved toward the SnS phase with band gap energy value around 1.22 eV. Otherwise, after annealing at 500 °C, it evolved towards SnS2 in the samples prepared at substrate temperatures above 300 °C.