High-Performance Ta₂NiSe₅-Based Broadband Photodetectors toward Self-Powered and Polarization-Sensitive Detection

Two-dimensional (2D) Ta₂NiSe₅ is a good broadband optoelectronic material because of its narrow bandgap, high carrier mobility, and excellent stability. Although Ta₂NiSe₅ and Ta₂NiSe₅-based heterostructures exhibit high-performance broadband detection under bias, the study on the polarization-sensitive ability of the Ta₂NiSe₅-based bilayer heterojunction under near-infrared (NIR) illumination in self-powered mode has rarely been explored. Considering the importance of self-powered photodetectors, here, we investigate the self-powered photoresponse of Ta₂NiSe₅-based heterostructures first, by using Ta₂NiSe₅/MoS₂, Ta₂NiSe₅/MoSe₂, and Ta₂NiSe₅/MoSSe as examples. It is found that the heterostructure Ta₂NiSe₅/MoSSe shows superior ability for self-powered broadband polarization-sensitive detection. Its photoresponse can range from the ultraviolet to near-infrared region, and the responsivity and specific detectivity can approach 238 mA/W and 2.73 × 10¹² Jones, respectively. Both rectification and on/off ratios arrive at ∼10⁵, and the dark current in the heterostructure is as low as 10^-14 A. These good performances originate from the strong built-in electric field in the heterostructure and lower contact resistance between the heterostructure and electrode. Then, we also explore the polarization detection of the device, and it shows significant polarization sensitivity of 2.3 under 750 nm illumination, based on the strong in-plane anisotropy of Ta₂NiSe₅. Our work paves the way to fabricate self-powered and polarization-sensitive photodetectors with high performance.