Ag₂Se-Modified Carbon Nanotube Film with Efficient Photothermoelectric Conversion for Flexible Non-Contact Detectors

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 Ag₂Se nanoparticles (CNT@Ag₂Se), 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 Ag₂Se 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@Ag₂Se 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.