Structural and optical properties of Fe-doped SnS2 nanoflakes prepared by molten salt solid state reaction

Tin (IV) disulfides (SnS2) doped with Fe ions are prepared through the molten salt solid state reaction at 280 °C and the effect of the Fe-doping on their structural and optical properties is reported. They were found to be nanocrystalline hexagonal structure with nanoflakes morphology with an average size 30 nm. The analysis of the optical data showed that all the samples are indirect semiconductors. Two absorption bands are observed in their optical diffuse reflectance spectra which indicate setting of two photons absorption processes due to formation of Fe intermediate band. The band gaps EgHInd and EgLInd that correspond to the two photons absorptions are found to vary from 1.49 to 1.09 eV and 0.76 to 0.93 eV, respectively. The most significant findings is that the sum of EgHInd and EgLInd has values between 2.25 and 2.02 eV which reproduces or slightly enhances the band gap value of the parent SnS2 (2.01 eV). This finding is directly related with the perseveration of the output voltage (Vo) which is a major condition required for realization of intermediate band solar cells with high solar conversion efficiency.