Self-Powered\nPhotodetector with High Efficiency and\nPolarization Sensitivity Enabled by WSe₂/Ta₂NiSe₅/WSe₂ van der Waals Dual Heterojunction

Abstract

Self-powered\nphotodetectors have triggered widespread attention\nbecause of the requirement of Internet of Things (IoT) application\nand low power consumption. However, it is challenging to simultaneously\nimplement miniaturization, high quantum efficiency, and multifunctionalization.\nHere, we report a high-efficiency and polarization-sensitive photodetector\nenabled by two-dimensional (2D) WSe₂/Ta₂NiSe₅/WSe₂ van der Waals (vdW) dual heterojunctions\n(DHJ) along with a sandwich-like electrode pair. On account of enhanced\nlight collection efficiency and two opposite built-in electric fields\nat the hetero-interfaces, the DHJ device achieves not only a broadband\nspectral response of 400–1550 nm but outstanding performance\nunder 635 nm light illumination including an ultrahigh external quantum\nefficiency (EQE) of 85.5%, a pronounced power conversion efficiency\n(PCE) of 1.9%, and a fast response speed of 420/640 μs, which\nis much better than that of the WSe₂/Ta₂NiSe₅ single heterojunction (SHJ). Significantly, based on the\nstrong in-plane anisotropy of 2D Ta₂NiSe₅ nanosheets,\nthe DHJ device shows competitive polarization sensitivities of 13.9\nand 14.8 under 635 and 808 nm light, respectively. Furthermore, an\nexcellent self-powered visible imaging capability based on the DHJ\ndevice is demonstrated. These results pave a promising platform for\nrealizing self-powered photodetectors with high performance and multifunctionality.