Photothermoelectric effect driven self-powered broadband photodetection in 1T′-MoTe2 with asymmetric electrodes†

Photothermoelectric (PTE) detection provides a versatile platform for uncooled ultra-broadband photosensing applications. The responsivity and speed of PTE-based photodetectors can be significantly enhanced by introducing two-dimensional (2D) topological Weyl semimetals owing to their unique tilting Weyl cones, high carrier mobilities, and hot-carrier-assisted transport. However, the requirement of localized illumination and complex device fabrication processes still hinder their broader application. Here, a high-performance 1T′-MoTe₂ PTE-based detector with asymmetric electrodes is constructed by employing ultra-high vacuum stencil lithography. The asymmetry is achieved by leveraging differential doping efficiencies at the metal contacts, breaking the mirror symmetry of the Seebeck coefficient profile across the channel. This architecture enables the generation of a self-powered photocurrent even under global illumination conditions. The detector shows a broadband response from 350 to 1200 nm, achieving a responsivity of 8.22 mA W⁻¹ and a detectivity of 7.11 × 10⁹ Jones. Furthermore, it demonstrates fast response dynamics with a rising time of 15.4 μs and a decay time of 8.4 μs. Our proposed strategy opens up the application of 2D Weyl semimetals in PTE-based photodetectors with the advantage of self-powering, broadband, and fast response.