Morphologies, optical and electrical characterization of aluminum tin sulfide thin film.

Tin (??) sulfide (SnS) has caught many researcher’s attentions as alternative material for solar cell absorber layer due to its abundance in nature, high absorption coefficient (a >104 cm-1) and ideal energy bandgap (in the range of 1.3 – 1.5 eV) that make SnS a suitable candidate for solar cell absorber layer. Aluminum doped SnS (Al:SnS) thin films were deposited onto glass substrates using thermal evaporator machine and annealed at 200oC for 2 hours under vacuum environment. The effects of doping at different weight percentages and annealing processes were investigated thoroughly using X-Ray diffraction (XRD) unit, scanning electron microscope (SEM), atomic force microscope (AFM) and ultra-violet visible (UV-Vis) spectrophotometer. From the XRD pattern, it was confirmed that Al:SnS thin films were successfully deposited using thermal evaporation technique. All the thin film samples were polycrystalline SnS oriented along the (111) direction with orthorhombic structure. XRD results also showed that doping and annealing processes increased the crystallite size of the thin film samples. Based on the SEM and AFM data, uniform thin film surfaces were obtained from samples that underwent the annealing process. UV-Vis spectral analysis indicated that the energy bandgaps for all samples were in the range of 1.32 to 1.49 eV, which were suitable for solar cell applications. From the four point probe measurement, it was found that SnS samples with lower resistivity were achieved when the samples were doped with aluminum. As conclusion, doping percentage and annealing process play vital role in producing high quality and suitable Al:SnS thin films for solar cell absorber layer