PdSe₂/NbSe₂ Heterojunction Photodetector with Broadband Detection and Polarization Sensitivity

Polarized photodetectors based on anisotropic two-dimensional (2D) materials display great potential applications in communications and optoelectronics. However, the existence of high dark current, low anisotropic ratio, and response speed limits their development. In this paper, a broadband polarization angle-dependent photodetector based on the PdSe₂/NbSe₂ van der Waals (vdW) heterojunction has been constructed. Characterization results show that the PdSe₂/NbSe₂ heterojunction photodetector can suppress the dark current effectively (NbSe₂ ∼4 orders of magnitude and PdSe₂ ∼1 order of magnitude compared with individual material). Meanwhile, the device exhibits a broadband detection capability ranging from 405 to 980 nm. The device shows a superior responsivity of 27 mA/W, a considerable detectivity of 9.8 × 10⁷ Jones, a large external quantum efficiency of 528%, and an ultrafast rise/decay time of 1.6/1.9 μs at 1 V bias under 638 nm laser wavelength. The photodetector also achieves a high polarization-sensitive anisotropic ratio of ∼2.62 under 638 nm laser irradiation. In addition, the heterojunction device shows outstanding polarization imaging capabilities, which can be used as the image sensor. This work proposed a PdSe₂/NbSe₂ vdW heterojunction device with low dark current, broadband polarized detection, and polarized visual imaging, which will promote the development and practicality of polarization-sensitive photodetectors.