Ultrahigh Thermoelectric Properties of PEDOT:PSS Films by Dedoping and π‐π Overlapping With 4‐(1,3‐dimethyl‐2,3‐dihydro‐1H‐benzoimidazol‐2‐yl)phenyl)Dimethylamine (N‐DMBI)

Abstract Thermoelectric (TE) materials have garnered considerable attention because they can be used to directly convert heat into electricity. Although organic TE materials have advantages of no or low toxicity, low cost, high mechanical flexibility, and solution processability, their TE properties, particularly the Seebeck coefficient, are saliently inferior to the inorganic counterparts. Here, the significant enhancement is reported in the Seebeck coefficient, and thus the overall TE properties of poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) films through a treatment with 4‐(1,3‐dimethyl‐2,3‐dihydro‐1H‐benzoimidazol‐2‐yl)phenyl)dimethylamine (N‐DMBI), which is a popular organic donor. The PEDOT:PSS films treated sequentially with H 2 SO 4 , NaOH, dimethyl sulfoxide (DMSO), and 4‐(1,3‐dimethyl‐2,3‐dihydro‐1H‐benzoimidazol‐2‐yl)phenyl)dimethylamine (N‐DMBI) can exhibit a high Seebeck coefficient of 64.1 µV K −1 and electrical conductivity of 1864 S cm −1 , and the corresponding power factor is 765.1 µW m −1 K −2 , the highest for solid polymer films. N‐DMBI can partially dedope PEDOT:PSS. In addition, it can have π–π overlapping with the conjugated PEDOT chains, which induces the splitting of the lower polaron level, thereby lifting the Fermi level and enhancing the Seebeck coefficient of PEDOT:PSS.