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Ultrabroadband, Fast, and Flexible Photodetector Based on HfTe5 Crystal

Ultrabroad spectrum detection has a wide range of photonic and optoelectronic applications, such as spectroscopy, optical communication, imaging, and sensing. 3D topological insulator candidates are promising materials for fast high‐performance photodetectors owing to their linear dispersion band structure and high carrier mobility. In this study, an ultrabroadband photothermoelectric (PTE) self‐powered detector based on the topological insulator candidate HfTe5 is reported for the first time. The photosensitive properties are characterized in an ultrabroadband range from the ultraviolet (375 nm) to terahertz (118.8 µm) wavelengths, and the responsivities at all examined wavelengths are found to be greater than 1 V W−1 at room temperature. Owing to the Dirac band dispersion of HfTe5, the response time (τ) of the proposed detector is as short as ≈1 ms, which is 1–3 orders of magnitude faster than that of recently reported PTE detectors based on millimeter‐scale graphene, 3D graphene, EuBiSe3 single crystal, and SrTiO3 crystal. Furthermore, the sensitivity of the HfTe5 detector to the light intensity and direction of linearly‐polarized light is demonstrated. Thus, the proposed device demonstrates outstanding flexibility, air stability, and long‐term photostability as well, displaying high potential for practical applications in wearable optoelectronics.