Self-Powered Photodetector with High Efficiency and Polarization Sensitivity Enabled by WSe₂/Ta₂NiSe₅/WSe₂ van der Waals Dual Heterojunction

Self-poweredphotodetectors have triggered widespread attentionbecause of the requirement of Internet of Things (IoT) applicationand low power consumption. However, it is challenging to simultaneouslyimplement miniaturization, high quantum efficiency, and multifunctionalization.Here, we report a high-efficiency and polarization-sensitive photodetectorenabled by two-dimensional (2D) WSe2/Ta2NiSe5/WSe2 van der Waals (vdW) dual heterojunctions(DHJ) along with a sandwich-like electrode pair. On account of enhancedlight collection efficiency and two opposite built-in electric fieldsat the hetero-interfaces, the DHJ device achieves not only a broadbandspectral response of 400-1550 nm but outstanding performanceunder 635 nm light illumination including an ultrahigh external quantumefficiency (EQE) of 85.5%, a pronounced power conversion efficiency(PCE) of 1.9%, and a fast response speed of 420/640 mu s, whichis much better than that of the WSe2/Ta2NiSe5 single heterojunction (SHJ). Significantly, based on thestrong in-plane anisotropy of 2D Ta2NiSe5 nanosheets,the DHJ device shows competitive polarization sensitivities of 13.9and 14.8 under 635 and 808 nm light, respectively. Furthermore, anexcellent self-powered visible imaging capability based on the DHJdevice is demonstrated. These results pave a promising platform forrealizing self-powered photodetectors with high performance and multifunctionality.