Self-Powered Broadband Photodetectors Based on Large-Scale Continuous Films of Weyl Semimetal WTe₂

WTe₂, as a member of Weyl semimetals, is a promising candidate for next-generation optoelectronic devices with the advantages of high response speed, broadband photoresponse, and low power consumption due to its unique band structure with conduction and valence bands touching at the Weyl nodes. Here, we report on the synthesis of large-scale continuous WTe₂ films and their application in self-powered broadband photodetectors (PDs). The films were synthesized on SiO₂/Si substrate using a modified chemical vapor deposition method with predeposited precursor particles. The pure 1T′ phase and the structural uniformity of the thin film were confirmed by Raman spectroscopy and energy-dispersive X-ray spectroscopy. PDs with asymmetric metal electrodes of Pd-WTe₂-Ag structure were designed and fabricated using shadow-mask-assisted ultra-high vacuum deposition method. By measuring the self-powered photocurrent under the illumination of Xe lamp, it is revealed that the device is sensitive to a wide range (λ = 320-1200 nm) of light spectra while maintaining the on/off ratio (∼10²), responsiveness (0.85 mA/W), and specific detectivity (1.23 × 10⁸ Jones). The response time reaches hundreds of milliseconds in different spectral bands. These results provide insights into future application of 1T′-WTe₂ in advanced optoelectronic devices like self-powered broadband PDs.