Effects of interfacial area and energetic barrier on thermoelectric performance of PEDOT:PSS-MXene composite films

Thermoelectric (TE) devices based on conducting polymers have significant potential for low-temperature energy harvesting. To enhance the TE performance, the incorporation of low-dimensional inorganic fillers into the polymer matrix has been considered as a promising strategy by exploiting the energy filtering effect. Since the energy filtering effect is strongly influenced by the carrier scattering at the interface between polymer and inorganic fillers, the TE properties are likely to be affected by the interfacial properties of two constituents. In this study, we investigated the TE performance in the composite films of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and two-dimensional Ti3C2 MXene, in order to reveal the effects of the interfacial area and the energetic barrier on the TE performance by controlling the MXene sizes and the oxidation level of PEDOT:PSS. We found that the composite film with smaller MXene exhibits a higher power factor (PF) than that with larger MXene, originating from the increased interfacial area which facilitates the energy filtering effect. We also showed that an optimal energy barrier (0.14 eV) between PEDOT:PSS and MXene can accelerate the energy filtering effect, which allows to maximize the PF of the composite films up to 69.4 mu W m(-1) K-2. We believe that our study not only contributes to the development of the composite-based TE devices utilizing the energy filtering effect, but also helps to understand the charge transport in polymer-inorganic composites.