Unipolar barriers in near-broken-gap heterostructures for high-performance self-powered photodetectors

The two-dimensional heterostructure is a promising research direction in photodetection. However, developing a good photodetector with high responsivity and fast speed is still challenging. Herein, we fabricate a high-performance self-powered broadband (355–1064 nm) photodetector based on a near-broken-gap GeSe/SnS2/InSe heterostructure, where SnS2 is used as a potential hole barrier layer. The device shows an ultrahigh open-circuit voltage (VOC) of 0.57 V, a high power-dependent responsivity of 1.87 A W−1 at 355 nm, and a fast response time of 8 μs in the self-powered mode. Based on the near-broken band alignment, the InSe layer with high electron mobility can efficiently collect the photogenerated electrons from the GeSe layer to improve conversion efficiency. Furthermore, the unipolar hole barrier at the interface can inhibit the Langevin recombination resulting in VOC enhancement. Notably, the anisotropy ratio of photocurrent in our device is also enhanced to ∼3.5, which is higher than GeSe photodetectors and other anisotropic devices counterparts. This work provides an opportunity for the realization of the high-sensitivity polarization-sensitive broadband photodetector.