High-Gain MoS₂/Ta₂NiSe₅ Heterojunction Photodetectors with Charge Transfer and Suppressing Dark Current

Emerging two-dimensional narrow band gap materials with tunable band gaps and unique electrical and optical properties have shown tremendous potential in broadband photodetection. Nevertheless, large dark currents severely hinder the performance of photodetectors. Here, a MoS₂/Ta₂NiSe₅ van der Waals heterostructure device was successfully fabricated with a high rectification ratio of ∼10⁴ and an ultralow reverse bias current of the pA level. Excitingly, the charge transfer and the generation of the built-in electric field of heterostructures have been proved by theory and experiment, which effectively suppress dark currents. The dark current of the heterostructure reduces by nearly 10⁴ compared with the pure Ta₂NiSe₅ photodetector at V_ds = 1 V. The MoS₂/Ta₂NiSe₅ device exhibits excellent photoelectric performance with the maximum responsivity of 515.6 A W^-1 and 0.7 A W^-1 at the wavelengths of 532 and 1064 nm under forward bias, respectively. In addition, the specific detectivity is up to 3.1 × 10¹³ Jones (532 nm) and 2.4 × 10⁹ Jones (1064 nm). Significantly, the device presents an ultra-high gain of 6 × 10⁷ and an exceptional external quantum efficiency of 1.2 × 10⁵% under 532 nm laser irradiation. The results reveal that the MoS₂/Ta₂NiSe₅ heterostructure provides an essential platform for the development and application of high-performance broadband optoelectronic devices.