Polycrystalline bismuth nanowire networks for flexible longitudinal and transverse thermoelectrics

This paper reports on the preparation and the characterization of structural, electrical and thermoelectric properties of nanocomposite films formed from three-dimensional networks of polycrystalline bismuth (Bi) nanowires (NWs). The samples were fabricated by electrodeposition within polycarbonate (PC) templates with crossed cylindrical nanopores, yielding self-supported networks of Bi crossed nanowires (CNWs) with mean diameter values ranging from 23 nm to 230 nm. Temperature changes in electrical resistance and thermopower were studied by considering electric and thermal currents flowing in the plane of the films. While the values of the Seebeck coefficient are close to those of polycrystalline Bi for diameters greater than 100 nm, a progressive decrease in thermopower appears at smaller diameters, due to an increasing contribution of surface charge carriers as the diameter decreases. Transverse thermoelectricity based on the Nernst effect was also demonstrated on a network of Bi CNWs 230 nm in diameter. Such hierarchical architectures based on Bi CNWs are extremely robust, offering a reliable solution for the next generation of flexible thermoelectric devices.

Automated summary

This paper presents the preparation and characterization of nanocomposite films made from three-dimensional networks of polycrystalline bismuth nanowires. The films were fabricated using electrodeposition within polycarbonate templates, resulting in self-supported networks of crossed nanowires with varying diameter values. The temperature-dependent electrical resistance and thermopower were studied, revealing a decrease in thermopower at smaller diameters due to the contribution of surface charge carriers. Transverse thermoelectricity based on the Nernst effect was also demonstrated on a network with a diameter of 230 nm. These hierarchical architectures offer a reliable solution for flexible thermoelectric devices.