Wavy-Structured Carbon Nanotube Photo-Thermoelectric Device for Self-Powered Sensing and Energy Harvesting.

Abstract

Fabrication of flexible photothermoelectric (PTE) devices represents a promising approach for harvesting solar and low-grade thermal energy. However, most PTE devices focus on enhancing temperature gradients (Δ<i>T</i>) through rigid three-dimensional structures, lacking flexibility, all-weather power generation capabilities, and being unable to achieve synchronized changes in photothermal and structural properties. Here, this paper designs a flexible PTE device with a wave-like structure, integrating thermo-actuation technology with a radiative cooling strategy, and achieving a photothermal device featuring reversible structural deformation, stable temperature gradients, and all-weather power generation. The photothermal response is achieved by forming a highly integrated p-n junction array through spaced printing of surface-functionalized single-walled carbon nanotubes (SWCNTs) on a polyimide (PI) film. Simultaneously, the mismatched thermal expansion coefficients between Al₂O₃@PDMS and PI enable reversible thermally driven deformation of the PTE. The resulting wave-like structure enhances the temperature gradient between the hot and cold sides, boosting photothermal conversion efficiency. The presence of Al₂O₃ nanoparticles confers radiative cooling properties, reflecting solar radiation and increasing the effective heat dissipation area to maintain a stable temperature gradient under illumination. This structural design enables the PTE device to achieve a Δ<i>T</i> of 20 K under 100 mW cm^-2 solar irradiation, overcoming the limitations of conventional photothermal devices, and it allows for nighttime energy harvesting, enabling round-the-clock power generation. This strategy offers a design approach for thermal management and the efficient conversion of light and heat energy.