Ultra-broadband detection by photovoltaic and thermoelectric coupling based on large-scale single-crystalline SnSe thin film

Recently, the layered tin selenide (SnSe) has attracted intense attention from the researchers due to its distinguished thermoelectric properties, thus giving this compound quite a promising potential application for photothermoelectric detectors. However, the low-cost epitaxial growth method toward a millimeter scale single phase SnSe thin film is still rarely reported, thus limiting its fabrications in arraying photoelectric sensors. Here, we synthesized a large-scale SnSe thin film on the SrTiO₃ substrate by using the crack of PbS thin film-assisted nucleation in the chemical vapor deposition, achieving a homogeneous single-crystal SnSe thin film with a centimeter scale, as revealed by the x-ray diffraction and scanning electron microscope measurement. In addition, a two-terminal device is fabricated to study the photoelectric properties of this film. Surprisingly, this SnSe detector shows a synergetic photovoltaic and thermoelectric effect, achieving an ultrabroad band detection ranging from visible (405 nm) to mid-infrared (10.0  $μm$⁠) at room temperature. Significantly, this detector also shows an impressive performance with an optimized response time of 2.81 ms (at 4.0  $μm$⁠), a responsivity of 290.9  $V W−1$ (at 4.0  $μm$⁠), and a detectivity of $5.5×108$ Jones (at 4.0  $μm$⁠). The above results addressed the bottleneck in SnSe film synthesis, and accelerated its applications in future high-performance photoelectronic devices.