Effective Self‐Powered Semimetal TaTe₂ Photodetector with the Thermal Localization Photothermoelectric Effect from Ultraviolet to Mid‐Infrared Range

Ultra‐broadband photodetectors based on semimetal crystals have recently become popular because of their gapless band structures. In particular, semimetal crystals have large carrier mobility or high Seebeck coefficient; this almost eliminates the possibility of using semimetal crystals as photodetectors. In addition, a larger temperature gradient can cause photocurrent generation based on the photothermoelectric effect. Surprisingly, the TaTe 2 crystal has a huge absorption coefficient (≈10 4 cm −1 ), a minimal specific heat (≈0.172 J g −1 K −1 ), and a low thermal conductivity (0.3 W m −1 K −1 ), which is beneficial for generating a high photothermal conversion efficiency of 30.2%, despite its small Seebeck coefficient, and achieving a large temperature gradient occurs for the heat generated by external illumination. Herein, the possibility of photoresponse based on the TaTe 2 detector is explored, which has a low carrier mobility (≈10 cm 2 V −1 s −1 ) and a small Seebeck coefficient (≈7.1 µV K −1 ). The self‐powered TaTe 2 photodetector can also provide a competitive photoresponse range from 355 to 2715 nm and exhibit a maximum responsivity of 1.1 mA W −1 with a detectivity of 4.7 × 10 8 Jones at 455 nm. This study provides a new design scheme and operating mechanism for semimetal photodetectors and enriches semimetal crystal photodetectors.