VSe2 Nanosheets for Broadband Photodetection from Visible to Terahertz

Broadband photodetection has been a hot topic since the development of application requirements for communication, imaging, spectroscopy, and sensing. However, state-of-the-art photodetectors face issues of a narrow response spectrum, low sensitivity, a slow response speed, and complex fabrication processes. Here, VSe2 nanosheets are utilized to fabricate an antenna-assisted ultrabroadband photodetector from the visible to terahertz (THz) region with a fast response driven by the multimechanism synergy. In the visible–infrared region, the photoresponse is caused by photoexcited electron–hole pairs and photothermal effect with an external bias voltage. The responsivities are 1.57 A W–1 at 635 nm, 0.63 A W–1 at 808 nm, 0.34 A W–1 at 980 nm, and 1.18 A W–1 at 1550 nm. In the THz region, nonequilibrium carriers are caused by the injection of electrons from the metal electrodes, and the responsivities are 1.25 × 104 A W–1 at 0.027 THz and 1.3 × 103 A W–1 at 0.256 THz. Meanwhile, a fast response (∼3 μs) and a rather low noise equivalent power (∼2.0 × 10–14 W Hz–1/2) are achieved. The ambient stability of our VSe2 broadband photodetector is proven by air exposure at a timescale of 1 month. Therefore, high-resolution THz imaging is conducted based on the excellent performance of the device. Our study demonstrates the promising prospects of VSe2 nanosheets in optoelectrical applications and provides an approach for high-performance ultrabroadband photodetection.