Tunable Thermoelectric Performance of Thin-Film Multilayered PEDOT:PSS for Flexible Devices

Power supply is a main challenge for wearable electronics and thermoelectric generators (TEGs), which directly convert a temperature difference into electrical power, are a promising solution. Owing to their great mechanical flexibility, material abundance, printability, and low toxicity, TEGs based on organic materials (OTE) show greater potential than their inorganic counterpart to power wearable devices. Among the OTE materials, PEDOT:PSS exhibits one of the best thermoelectric performance. The performance of thermoelectric materials/devices is usually evaluated by the power factor, which is the product of electrical conductivity to the square of the Seebeck coefficient. Many strategies – such as using secondary dopants, post-treatments, and morphological alignment – have been reported to boost the power factor of PEDOT:PSS via increasing the electrical conductivity. However, thus far, the only method to increase the Seebeck coefficient of PEDOT:PSS is de-doping it by the addition of reductive agents. However, de-doping strongly harms the electrical conductivity, which limits the strategies for TEGs design. Herein, we demonstrate a new structure-based approach to improve the Seebeck coefficient of PEDOT:PSS without strongly degrading its electrical conductivity. Inspired by the energy filtering effect used in inorganic TEs, our approach consists of the fabrication of a thin-film multilayer stack that promotes the interfacial scattering of the low-energy carriers detrimental to the Seebeck effect. Optical spectroscopy and X-ray scattering techniques will be used to study the oxidation level and morphology of the produced stack, shedding light on the structure-performance relationship in the material and paving the way to the optimization of the thermoelectric performance. To demonstrate the suitability of our approach for wearable devices, a flexible version of the multilayered material will be produced.