Effects of Ge- and Sb-doping and annealing on the tunable bandgaps of SnS films

• Ge- and Sb-doped SnS films were fabricated via spin-coating.
• The solubilities of Ge and Sb in SnS are about 6 and 5 at.%, respectively.
• The bandgaps of SnS films can be tuned by Ge and Sb doping respectively.
• Annealing above 300 °C reduces the bandgaps of Ge- and Sb-doped SnS films.

SnS, Ge- and Sb-doped SnS films with single orthorhombic SnS phase were fabricated via solvothermal routes and subsequent spin-coating, respectively. The substitution solubilities of Ge and Sb in SnS are about 6 and 5 at.%, respectively. The bandgaps of Ge- and Sb-doped SnS films can be tuned in the ranges of 1.25–1.35 and 1.30–1.39 eV, respectively. The possible mechanisms for the tunable bandgaps of Ge- and Sb-doped SnS films are discussed. For the Ge- and Sb-doped SnS films subjected to annealing at 200–350 °C in N2, the bandgaps of 200 °C-annealed films remain unchanged, while those of 300 °C- and 350 °C-annealed films decrease with the annealing temperature because of the evaporation of Ge and Sb respectively.