InSe Nanosheet/Ultrathin Si Heterojunction for Filterless, Self-Powered Ultraviolet Photodetection

Owing to the wavelength-dependent coefficient, ultrathin Si demonstrates potential for filterless ultraviolet (UV) photodetection. However, the UV photodetection performance deteriorates significantly by severe surface recombination arising from the high defect density. In this work, we report on the fabrication of an InSe nanosheet/ultrathin Si heterojunction. The established built-in electric field at the interface facilitates the efficient separation of photocarriers and leads to an improved carrier collection efficiency. The heterojunction functions well as a self-powered and filterless UV photodetector, achieving a peak responsivity (R) of 0.25 A W^-1, an external quantum efficiency (EQE) as high as 85.6%, and a fast response speed (150/195 μs for rise/fall times, respectively) under 365 nm illumination. The device also shows great potential for anti-interference UV communication applications. This work offers a promising strategy for portable UV optical communication systems.