Polarization-Sensitive, Self-Powered, and Broadband Semimetal MoTe 2 /MoS 2 van der Waals Heterojunction for Photodetection and Imaging.

The emerging type II Weyl semimetal 1T' MoTe 2 as a promising material in polarization-sensitive photodetectors has aroused much attention due to its narrow bandgap and intrinsic in-plane anisotropic crystal structure. However, the semimetal properties lead to a large dark current and a low response. Herein, we demonstrate for the first time an all-2D semimetal MoTe 2 /MoS 2 van der Waals (vdWs) heterojunction to improve the performance of the photodetectors and realize polarization-sensitive, self-powered, and broadband photodetection and imaging. Owing to the built-in electric field of the heterojunction, the device achieves a self-powered photoresponse ranging from 520 to 1550 nm. Under 915 nm light illumination, the device demonstrates outstanding performance, including a high responsivity of 79 mA/W, a specific detectivity of 1.2 × 10 10 Jones, a fast rise/decay time of 180/202 μs, and a high on/off ratio of 1.3 × 10. 3 Wavelength-dependent photocurrent anisotropic ratio is revealed to vary from 1.10 at 638 nm to 2.24 at 1550 nm. Furthermore, we demonstrate the polarization imaging capabilities of the device in scattering surroundings, and the DoLP and AoLP images achieve 78% and 112% contrast enhancement, respectively, compared to the S 0 . This work opens up new avenues to develop anisotropic semimetals heterojunction photodetectors for high-performance polarization-sensitive photodetection and next-generation polarized imaging.