Photon-Phonon-Electron Synergy Enables Efficient Photothermoelectric Conversion for Intelligent Fire Warning.

Photothermoelectric (PTE) detectors offer broad-spectrum response and high sensitivity, but their performance and applications are fundamentally limited by the difficulty of simultaneously controlling photon absorption, phonon propagation, and charge-carrier dynamics. Here, we report silver selenide/silver secondary phases (Ag2Se/Ag-SPs) nanocomposite films comprising vertically aligned Ag-SPs within a (00l)-oriented Ag2Se matrix, fabricated via oriented growth and confined phase separation. This customized architecture suppresses lattice thermal transport through interfacial phonon scattering and regulates carrier transport via shallow-barrier Ag/Ag2Se interfaces, collectively optimizing the thermo-electric conversion process. Moreover, plasmonic waveguiding within Ag-SPs domains improves broadband light absorption, thereby promoting photothermal heat generation, enabling a high PTE responsivity of 126 V W-1 at 1550 nm. When integrated with machine-learning-based transient signal classification, this detector achieves 100% sensitivity in flame recognition, allowing sub-second differentiation of combustion events from innocuous thermal sources. This photon-phonon-electron synergistic enhancement mechanism establishes a scalable paradigm for efficient PTE conversion, offering transformative potential for intelligent fire-warning systems.