Metal-Semiconductor Phase Transition in Multilayer VSe2 for Broadband Photodetector with High Sensitivity

2D 1T-VSe₂ is a charge-density wave (CDW) system that also exhibits room-temperature ferromagnetism, making it promising for photodetecting devices. However, the sensitivity of 1T-VSe₂ photodetectors is limited by the high dark current due to its metallic feature of T-phase VSe₂. So far, photodetectors based on semiconducting 2H-phase VSe₂ have ever been reported. In this work, the metal-semiconductor phase transition (1T to 2H) in multilayer VSe₂ by thermal annealing process, and the fabrication of 2H-VSe₂ broadband photodetectors with high sensitivity is reported. The 2H-VSe₂ photodetectors exhibit low dark current and a broad spectral range of 405–1550 nm. The responsivity (R) and detectivity (D*) can reach up to 75.26 A W⁻¹ and 1.45 × 10¹⁰ Jones at V_sd of 1 V, outperforming photodetectors based on 1T-VSe₂ and other 2D materials for the 1550 nm optical communication band. This work showcases a facile method for obtaining the metal-semiconductor phase transition of VSe₂ and demonstrates the potential of 2H-VSe₂ for high-performance near-infrared photodetectors.