Dicationic Ion-Pair Doping Enables Stable and High-Performing Conducting Polymers for Organic Thermoelectrics

Molecular doping is a key strategy for tuning the thermoelectric (TE) properties of conjugated polymers. Yet achieving both high TE performance and long-term stability remains challenging, as counterions redistribute and microstructures reorganize under thermal and ambient exposure. Here we investigate TAB-2TFSI (TAB²⁺·2TFSI^-), a dicationic ion-pair dopant that couples a strong oxidizing TAB motif with two weakly coordinating TFSI^- counterions. Using poly(3-hexylthiophene-2,5-diyl) (P3HT) as a model polymer, we benchmark TAB-2TFSI against state-of-the-art p-doping systems and find that it delivers the highest average electrical conductivity of 290 ± 30 S cm^{- 1} and power factor of 40 ± 6 µW m^{- 1} K^{- 2}, placing P3HT among the top high-performing isotropic doped polymer thermoelectrics ever reported. Temperature-dependent transport analysis, together with GIWAXS and AFM-IR mapping of TFSI-associated vibrational signatures, indicates morphology-induced improved transport connectivity and a more homogeneous ionic landscape than for other dopants. Consistently, TAB-2TFSI exhibits the highest stability under inert aging and accelerated thermal/oxidative stress among all the doping systems tested, evidenced by minimal spectral and structural evolution over time and the most stable TE performance. Finally, we demonstrate the wide applicability of TAB-2TFSI as a dopant across multiple popular conjugated polymers, highlighting its material-agnostic potential to boost simultaneously doping efficiency and stability.