Multi-Mechanism Driven Ta<sub>2</sub>NiSe<sub>5</sub>–Graphene Heterojunction for Ultrabroadband Detection from\nVisible to Terahertz Spectrum

Ultrabroadband\nphotodetectors are essential for applications such\nas biomedical imaging, environmental assessment, optical data transmission,\ngas detection, and security monitoring. However, traditional semiconductor\ndetectors are typically limited to detection within a single spectral\nrange, and achieving ultrabroadband detection often requires integrating\nmultiple detectors. This is particularly challenging in the terahertz\nrange, where detection is constrained by high dark currents and the\nneed for cryogenic cooling. As a result, expanding the detection range\nhas become a critical focus in optoelectronic development. In this\nstudy, we successfully demonstrated ultrabroadband detection from\nthe visible to terahertz spectrum at room temperature using a heterojunction\nformed by Ta<sub>2</sub>NiSe<sub>5</sub> and graphene, driven by multiple\nphysical mechanisms. The detector leverages the combined effects of\nphotoexcited electron–hole pairs and the photothermal response\ntriggered by the asymmetry of the heterojunction, achieving responsivities\nof 4.8 mA/W at 638 nm, 3.8 mA/W at 1550 nm, 42.9 mA/W at 0.12 THz,\nand 14.6 mA/W at 0.3 THz. Additionally, the device achieves NEP values\nas low as 7 pW/Hz<sup>1/2</sup> at 0.12 THz and 23 pW/Hz<sup>1/2</sup> at 0.3 THz, with a response time of 7.4 μs at 0.12 THz. Our\nfindings demonstrate a novel approach to ultrabroadband detection,\nachieving high sensitivity and fast response by leveraging multiple\nphysical mechanisms. This work opens new avenues for the future development\nof optoelectronic detection technologies.