Morphology–Function Relationship of Thermoelectric Nanocomposite Films from PEDOT:PSS with Silicon Nanoparticles

Abstract

The relation of the thermoelectric figure of merit and the nanocomposite morphology is studied for thermoelectric thin films consisting of poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) with different amounts of silicon nanoparticles (Si‐NPs). An increase in the figure of merit of up to 150% is found for an Si‐NP concentration of 0.5 wt% as compared to pristine PEDOT:PSS films. The improvement originates from a disruption in the molecular ordering and therefore reduced electrical conductivity, which leads to an increased Seebeck coefficient, while also reducing thermal conductivity for higher concentrations through phonon scattering. The thermal conductivity is measured with steady‐state IR thermography on free‐standing PEDOT:PSS/Si‐NP composite films, enabling a full determination of the figure of merit. The morphology is investigated with grazing incidence resonant tender X‐ray scattering (GIR‐TeXS) around the sulfur K‐absorption edge. Without need for extrinsic labeling, GIR‐TeXS measurements have varying scattering contrast conditions for the components of the ternary system. By comparing the scattered intensities at different photon energies with the corresponding scattering contrast, the Si‐NPs are found to be preferentially dispersed in the large and medium‐sized PEDOT‐rich domains. The changes in size for the PEDOT‐rich domains as function of Si‐NP concentration cause improvement of the thermoelectric properties of the films.

Effects of additives and post‐treatment on the thermoelectric performance of vapor‐phase polymerized PEDOT films

“…This estimate is relatively reasonable, On the one hand, this work of material and the polymerization method are in good accordance with literature, and the thermal conductivity is not dependent on the oxidation state . On the other hand, the thermal conductivity of CPs is difficult to measure accurately, and the values are often only estimated in the literature . Therefore, using the optimum measured PF and the above κ // values, a maximum of ZT = 0.036 at 295 K was obtained.…”

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