Thermoelectric Enhancement in PEDOT:PSS Inks Driven by PSS Molecular Weight Tailoring

The growing demand for electricity aggravates global warming and reinforces the need for affordable and sustainable energy sources. Thermoelectric generators, which convert waste heat into electricity, have attracted increasing attention as sustainable energy technologies. Conductive polymers such as poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) are promising candidates due to their low cost, flexibility, and low toxicity. In this study, we investigate the influence of the molecular weight (Mw) of poly(4-styrene sulfonic acid) (PSS) on the thermoelectric properties of PEDOT:PSS inks. The Seebeck coefficient (S) and electrical conductivity (σ) were evaluated to determine the power factor (PF = S 2 · σ). Increasing the Mw of PSS promotes the formation of larger interconnected PEDOT-rich domains, enhancing charge transport and improving the thermoelectric performance. The ink synthesized with higher molecular weight PSS (157 kDa) exhibited the best performance, reaching a power factor of (1.3 ± 0.1) μW/(K 2 ·m), approximately 30 times higher than that of the ink with lower Mw PSS (23 kDa).