<p>In this study, we investigated the effect of ethylene glycol (EG) as a high-boiling-point solvent and sodium dodecyl sulfate (SDS) as a surfactant on the thermoelectric performance of free-standing poly(3,4-ethylendioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films. Samples were prepared by varying the concentrations of EG and SDS, and their electrical conductivity, σ; Seebeck coefficient, S; power factor, PF; and figure of merit, ZT; were analyzed in detail. Among all formulations, the sample with both SDS and EG exhibited the best thermoelectric properties with a conductivity of 658 S/cm, Seebeck coefficient of 21.4&#xa0;μV/K, and PF of 29.0&#xa0;μW/mK², along with a significantly improved ZT value of 0.056 and stretchability over 39%. Structural characterizations using XRD revealed enhanced crystallinity and reduced FWHM for the SDS + EG sample, confirming improved molecular ordering. XPS analysis showed a lower PSS:PEDOT ratio compared to pristine films, indicating partial removal or rearrangement of excess PSS chains. Furthermore, SEM results also supported smoother, more uniform morphology in SDS/EG films, which matches well with the XRD and XPS trends. Film made with only EG showed noticeable improvement compared to the pristine sample, achieving a conductivity of 785 S/cm and PF of 22.9&#xa0;μW/mK². While only EG improved conductivity, overall performance remained lower than that of the SDS/EG-treated film, indicating that structural modification was limited. Combined SDS and EG treatment promoted better ordering and connectivity, resulting in good ZT. This work provides an optimized, practical, and scalable approach for tuning the microstructure and thermoelectric behavior of PEDOT: PSS-based films, offering great potential for wearable and low-power electronics.</p>