High‐Performance and Ecofriendly Organic Thermoelectrics Enabled by N‐Type Polythiophene Derivatives with Doping‐Induced Molecular Order

Abstract The ability of n‐type polymer thermoelectric materials to tolerate high doping loading limits further development of n‐type polymer conductivity. Herein, two alcohol‐soluble n‐type polythiophene derivatives that are n‐PT3 and n‐PT4 are reported. Due to the ability of two polymers to tolerate doping loading more significantly than 100 mol%, both achieve electrical conductivity >100 S cm −1 . Moreover, the conductivity of both polythiophenes remains almost constant at high doping concentrations with excellent doping tunability, which may be related to their ability to overcome charging‐induced backbone torsion and morphology change caused by saturated doping. The characterizations reveal that n‐PT4 has a high doping level and carrier concentration (>3.10 × 10 20 cm −3 ), and the carrier concentration continues to increase as the doping concentration increases. In addition, doping leads to improved crystal structure of n‐PT4, and the crystallinity does not decrease significantly with increasing doping concentration; even the carrier mobility increases with it. The synergistic effect of these two leads to both n‐PT3 and n‐PT4 achieving a breakthrough of 100 in conductivity and power factor. The DMlmC‐doped n‐PT4 achieves a power factor of over 150 µW m −1 K −2 . These values are among the highest for n‐type organic thermoelectric materials.