Self-Powered Broadband UV-NIR Polarization-Sensitive Photodetector Based on Unipolar van der Waals Heterostructure

van der Waals heterostructures (vdWH) composed of two-dimensional (2D) materials have demonstrated significant potential in new-generation multifunctional photodetectors. Herein, we demonstrate a self-powered broadband polarization-sensitive photodetector with high efficiency and ultrafast response speed based on 2D MoS₂/Ta₂NiSe₅ vdWH, which is due to the unilateral depletion region formed at the n-n junction. Under 638 nm laser illumination, the as-fabricated 2D MoS₂/Ta₂NiSe₅ vdWH photodetector exhibits remarkable photoresponse, including high responsivity (R) of 1382 A/W, large specific detectivity (D*) of 6.59 × 10¹³ cm Hz^1/2 W^-1, and impressive external quantum efficiency (EQE) of 2.7 × 10⁵ %, together with ultrafast response time of ∼3 μs. Additionally, the device shows prominent photovoltaic effects with a short-circuit current of 27.4 nA, an open-circuit voltage of 0.28 V, and a maximum output electrical power (P_el) of 1.85 nW, respectively, as well as remarkable self-powered photodetection performance. Interestingly, the device showcases a broadband photoresponse ranging from UV-NIR both under biased and unbiased conditions. Notably, the device also exhibits a robust polarization ratio (PR) of up to 2.89. This study highlights the potential applications of self-powered, broadband, and polarization-sensitive photodetectors based on unipolar vdWH.