Flexible Broadband Photothermoelectric Detector for Self‐Powered Gas Monitoring

Abstract The self‐powered and ultra‐broadband photodetectors based on the photothermoelectric (PTE) effect hold significant promise for diverse applications, including night vision, environmental monitoring, and gas sensing. However, existing PTE materials, primarily based on 2D or bulk materials, face limitations in flexible applications and large‐area array integration. Here, it is demonstrated that a flexible PTE photodetector constructed from a large‐area bismuth telluride (Bi 2 Te 3 ) film, coupled with an asymmetric electrode structure. The temperature gradient generated by the asymmetric electrode configuration induces carrier diffusion, resulting in the generation of photovoltage via the PTE effect, even under global illumination. The device exhibits broadband photoresponse across the spectral range from 0.405 to 10.37 µm at room temperature, achieving a detectivity of 1.39 × 10 8 Jones at 10.37 µm. Furthermore, the photodetector is integrated into a gas‐sensing system, achieving a limit of detection (LOD) of ≈100 ppm for CO 2 in its self‐powered mode without external circuits. This work paves the way for the development of flexible, CMOS‐compatible, and cost‐effective optical gas sensors with integrated multifunctionality.