Enhanced Thermoelectric Efficiency in Highly Flexible PVDF–Te Composite Films: Role of Nanoparticle Morphology

The advancement of flexible composite polymers has revolutionized the field of thermoelectric (TE) energy harvesting at room temperature. Human body heat, as a sustainable energy source, can be efficiently converted to usable electrical energy through flexible thermoelectric devices. In this regard, achieving a high Seebeck coefficient is crucial to enhancing device performance. In this study, we present a highly flexible composite film composed of poly(vinylidene fluoride) (PVDF) and tellurium (Te) nanoparticles processed in a 1:1 ratio via a simple solution-casting method. The morphology (nanorods vs nanoellipsoids) and the distribution of Te nanoparticles within the PVDF matrix play a critical role in determining the thermoelectric properties of the composite films. In particular, at 300 K, the Seebeck coefficient increased from 360 μV/K for the PVDF–Te nanorods film to 460 μV/K for the PVDF–Te nanoellipsoids film. The composite film incorporating Te nanoellipsoids demonstrated a 2.6-fold increase in the room temperature power factor compared to the film with Te nanorods, underscoring the significant impact of the nanoparticle morphology on the thermoelectric performance. Furthermore, a thermoelectric strip cut from the PVDF–Te nanoellipsoid composite film successfully generated an output voltage of 107 mV from the heat of the human body, with a temperature difference of 7 K between the body and the ambient environment. The prototype also exhibited exceptional flexibility and twistability, making it highly suitable for applications in microelectronics, wearable bioelectronics, and smart textiles. This is the first reported study of body-heat harvesting using PVDF–Te nanoellipsoid thermoelectric films, highlighting the crucial role of inorganic nanoparticle morphology in enhancing the thermoelectric performance of wearable energy-harvesting devices.