Polarity Flipping in SnSe Empowering Wavelength Selective Self-Powered Broadband Photodetection

The demand for high-performance self-powered photodetectors with broadband wavelength selectivity has intensified due to their applications in various fields such as imaging, sensing, communication, and environmental monitoring. Among emerging materials, tin selenide (SnSe) has garnered significant attention for its promising optoelectronic properties. In this study, we have investigated the phenomenon of polarity flipping in sputtering-grown pure SnSe film and its impact on broadband wavelength selective photodetection. The designed metal semiconductor metal device with an active area of 9 μm2 exhibits a maximum responsivity of 10.82 mAW–1, a high external quantum efficiency of 378.76%, and the lowest noise equivalent power of 5.3 × 10–13 WHz–1/2 for 1064 nm light illumination of optical power 16.2 nW in self-bias mode. The proposed pure SnSe-based device exhibits wavelength-dependent polarity switching in self-bias mode for the spectral range UV–NIR, enabling the device to function in bidirectional mode. The polarity flipping response in the photodetector makes it possible to differentiate between different photons, such as ultraviolet/visible and near-infrared. This capability can improve the accuracy and efficiency of environmental monitoring systems, enabling better detection and analysis of various environmental factors, such as light pollution, radiation levels, and atmospheric composition. We elucidated the possible phenomenon underlying polarity flipping through a comprehensive characterization of the material's structural, optical, and electrical properties. Our findings reveal that the controlled phase during sputter deposition can significantly alter the crystalline structure, resulting in tunable optical properties and enhanced photoresponse across a broad wavelength range. Additionally, the polarity flipping phenomenon enables the photodetector to exhibit unprecedented broadband wavelength selectivity, thus opening avenues for developing advanced optoelectronic devices. This research advances our fundamental understanding of phase-controlled SnSe thin film and paves the way for designing and fabricating highly efficient self-powered photodetectors with tailored spectral response characteristics.