Low-Energy Nitrogen Ion Implantation Tunes the Thermoelectric Performance of PEDOT:PSS

The inherent trade-off between electrical conductivity and Seebeck coefficient limits the thermoelectric performance of PEDOT:PSS, and conventional chemical post-treatments introduce residues and process complexity. Here, we employed a physical ion implantation strategy that induces chemical doping in PEDOT:PSS thin films and systematically investigated the effects of implantation energy and dose on their structural and thermoelectric properties. Incident ions triggered chain scission and reconstruction via cascade collisions, forming C–N/C═N covalent bonds that achieved effective doping without introducing external dopant residues. Implantation energy governed the damage and repair pathways within the conjugated network by modulating the collision regime and penetration depth, while implantation dose drove a three-stage evolution of nitrogen chemical states, from C═N doping through oxidized nitrogen intermediates to nitrogen-incorporated carbonized networks, which orchestrated the carrier transport transition from purification-enhanced conduction through localization breakdown to percolation recovery. Under optimal conditions (30 keV, 1 × 1015 cm–2), the electrical conductivity reached 741 S cm–1, seebeck coefficient was 16.0 μV K–1, and the power factor reached 19.2 μW m–1 K–2, which is 6.6 times that of the pristine sample. This work demonstrates that ion implantation effectively achieves a synergistic enhancement of electrical conductivity and Seebeck coefficient at the optimal condition, offering a practical, residue-free route to high-performance organic thermoelectric for industrial deployment.