CuI/ReS₂ van der Waals Heterojunction for Self-Powered Broadband and Polarization-Sensitive Photodetection

Polarization-sensitive photodetectors that simultaneously deliver self-powered operation, broadband response, and high polarization selectivity remain challenging due to intrinsic trade-offs between carrier separation efficiency and anisotropic photoresponse in low-symmetry materials. Here, we report a CuI/ReS₂ van der Waals heterojunction photodetector that addresses these challenges through a synergistic approach based on interface-engineered built-in electric fields coupled with intrinsic in-plane anisotropy. The heterojunction enables efficient photocarrier separation, while the dark current is effectively suppressed, resulting in stable self-powered operation. Under 365 nm illumination at zero bias voltage, the photodetector exhibits an open-circuit voltage of -175 mV, a short-circuit current of 25 pA, and a responsivity of 8.02 mA/W. At a bias voltage of 1 V, the photodetector demonstrates broadband photodetection from 365 to 810 nm, with a peak responsivity of 590.59 mA/W, a detectivity of 6.18 × 10¹⁰ Jones, an on/off current ratio of 10³, and rapid rise and decay times of 7.93 and 8.73 ms. Moreover, the CuI/ReS₂ photodetector exhibits polarization sensitivity, achieving a polarization ratio of 2.84 at 660 nm. We demonstrate polarization-encoded imaging, highlighting the capability of the device for real-time optical information processing. This work demonstrates a feasible strategy for integrating self-powered operation, broadband detection, and polarization sensitivity, offering a promising platform for compact intelligent optoelectronic systems.