Air-Stable GaSe/ReS₂ Heterojunctions for Self-Powered Polarization-Sensitive Photodetectors

The problem of energy shortage and environmental pollution is becoming remarkably important and has attracted much attention. Driven by this situation, self-powered devices are highly desirable in all areas. Herein, a broadband photoresponse, self-powered, polarization-sensitive photodetector based on stacked two-dimensional type-II GaSe/ReS2 heterostructures is demonstrated. Because of the formation of the type-II band alignment, GaSe/ReS2 heterostructures display a self-powered photoresponse with an Ion/Ioff ratio of about 8.3 × 102 and exhibit a high responsivity of 54 mA/W under illumination with 532 nm laser light. A maximum photoresponsivity of 170 mA/W and an external quantum efficiency of 10% can be achieved by illumination with a 340 nm laser. Additionally, benefiting from the highly in-plane anisotropic atomic arrangements of ReS2, the photodetector shows a polarization-sensitive photocurrent. The dichroic ratio and polarization sensitivity are determined to be 1.73 and 3.03, respectively, and the highest photoresponsivity of the photodetector can reach up to 94 mA/W when the direction of the incident polarized laser is parallel to the b-axis of ReS2. Importantly, the self-passivating behavior of GaSe can maintain the performance of the heterojunction for 1 week. The present findings open new opportunities for developing air-stable, high-performance van der Waals heterostructure photodetectors.