Self-Powered Photodetector with High Efficiency and Polarization Sensitivity Enabled by WSe 2 /Ta 2 NiSe 5 /WSe 2 van der Waals Dual Heterojunction.

Self-powered photodetectors have triggered widespread attention because of the requirement of Internet of Things (IoT) application and low power consumption. However, it is challenging to simultaneously implement miniaturization, high quantum efficiency, and multifunctionalization. Here, we report a high-efficiency and polarization-sensitive photodetector enabled by two-dimensional (2D) WSe 2 /Ta 2 NiSe 5 /WSe 2 van der Waals (vdW) dual heterojunctions (DHJ) along with a sandwich-like electrode pair. On account of enhanced light collection efficiency and two opposite built-in electric fields at the hetero-interfaces, the DHJ device achieves not only a broadband spectral response of 400-1550 nm but outstanding performance under 635 nm light illumination including an ultrahigh external quantum efficiency (EQE) of 85.5%, a pronounced power conversion efficiency (PCE) of 1.9%, and a fast response speed of 420/640 μs, which is much better than that of the WSe 2 /Ta 2 NiSe 5 single heterojunction (SHJ). Significantly, based on the strong in-plane anisotropy of 2D Ta 2 NiSe 5 nanosheets, the DHJ device shows competitive polarization sensitivities of 13.9 and 14.8 under 635 and 808 nm light, respectively. Furthermore, an excellent self-powered visible imaging capability based on the DHJ device is demonstrated. These results pave a promising platform for realizing self-powered photodetectors with high performance and multifunctionality.