Exploring the optoelectronic properties of SnSe: a new insight

Tin selenide has established its sound presence among 2D materials. A recent trend in the thermoelectric application study of this material has led to ignoring its optoelectronic potential. Here, we are unraveling its optoelectronics (viz., photodetector and solar cell) potential. Oxidation of the chalcogenides seems to be a boon for tin selenide for its optoelectronic properties. Tin selenide annealed at 300 °C in the open air for different times (0.5, 1, and 1.5 h) shows three consecutive layers (viz. SnSe, SnSe2, and SnO2). After the open-air annealing of SnSe, an enhanced photo-response in the broad spectrum is observed. A spectral response in the broad range of 250-1250 nm is observed compared to unannealed SnSe. Annealing time can tune the response in the required region, such as the ultraviolet and near-infrared regions. A maximum of 0.125 mA W−1 responsivity in the ultraviolet region (355 nm) for 1.5 h annealed and ∼0.117 mA W−1 for 0.5 h annealed in the near-infrared region has been observed. The layers formed are naturally in the form of basic solar cell structures. Experimentally the solar cell efficiency obtained after annealing indicates a new area of exploration for SnSe. A solar cell simulation study (by the simulation program SCAPS-1D) showed that efficiency is very sensitive to the electron affinity of the SnSe2 layer and could reach up to 20.28% under some defined conditions. This fabrication technique for the solar cell can substitute a clean room facility for the fabrication. The open-air annealing led to a better device in terms of responsivity, stability against environmental conditions, and natural formation of the solar cell. Also, this is the first ever reported device that can be uniquely formed just by open-air annealing. Optimizations in the parameters may open a new door in the fabrication technology of solar cells.