ABSTRACT Simultaneously achieving high photothermal and thermoelectric conversion efficiencies in flexible thin films remains challenging, limiting the performance of ultra‐broadband photothermoelectric (PTE) detectors. This study introduces a two‐step approach involving silver pre‐deposition and vapor‐phase selenization, based on a solid‐vapor diffusion mechanism, to fabricate a flexible carbon nanotube (CNT) film modified with Ag 2 Se nanoparticles (CNT@Ag 2 Se), synergistically enhancing its light absorption and thermoelectric properties. By optimizing the selenization time, the carrier transport behavior was effectively modulated, yielding a maximum power factor of 84.35 µW·m −1 ·K −2 at room‐temperature after 20 min of treatment. The incorporation of Ag 2 Se nanoparticles also significantly improved light absorption and photothermal conversion, enabling broad‐spectrum absorption across 200–2500 nm with a 47% enhancement in photothermal performance. As a result, the CNT@Ag 2 Se film exhibited a doubled voltage output compared to pristine CNT films, along with ultra‐broadband detection capability. Laser position‐dependent measurements and synchronized infrared thermal imaging confirm that the photovoltage originates from a light‐induced temperature gradient driving directional carrier diffusion, illustrating a photothermal‐thermoelectric coupling mechanism. Systematic characterization and simulation further reveal the underlying mechanisms for the performance improvement. Furthermore, the film demonstrates excellent flexibility, retaining a stable output under multiple bending cycles and demonstrating outstanding non‐contact sensing capabilities.
Yang et al. (2026) studied this question.