Multifaceted Tuning of PEDOT:PSS with Electron-Withdrawing Effect for Superior Thermoelectric Performance

Flexible organic thermoelectric materials hold promise for wearable electronics and low-grade waste heat recovery, yet their performance is limited by the trade-off between electrical conductivity and the Seebeck coefficient. Here, we report a molecular-level strategy to enhance PEDOT:PSS films via electron-withdrawing substituents in benzoic acid. Fluoro (-F) and cyano (-CN) groups synergistically tune chain conformation, molecular ordering, and carrier-state distribution. Furthermore, the cyano and fluoro groups introduce energy barriers that selectively filter low-energy carriers, thereby reducing bipolaron content and boosting the Seebeck coefficient, while facilitating PSS removal and improving electrical conductivity. The optimized DMSO:2-fluoro-5-cyanobenzoic acid (DMSO:2F5CBA) treated film exhibits a conductivity of >1200 S cm-1, a Seebeck coefficient of 43.8 μV K-1, and a power factor of 188.89 μW m-1 K-2. Spectroscopic and morphological analyses confirm effective modulation of carrier states, chain ordering, and phase separation. This work demonstrates a multifaceted approach where energy filtering and structural optimization synergistically enhance thermoelectric performance, providing a promising route toward high-performance flexible organic thermoelectrics.