Organic superbase-induced polaron modulation enables high thermoelectric performance in solid PEDOT:PSS films

Organic thermoelectric (TE) materials are attractive for sustainable energy harvesting owing to their mechanical flexibility, low cost, and intrinsically low thermal conductivity. Among them, PEDOT:PSS is one of the most promising candidates. However, its relatively low Seebeck coefficient limits further improvement in TE performance. Here, we demonstrate that treatment with the organic superbase 1-tert-butyl-2,2,4,4,4-pentakis(dimethylamino)-2λ⁵,4λ⁵-catenadi(phosphazene) (P2-t-Bu) of PEDOT:PSS films can enhance the Seebeck coefficient and preserve high electrical conductivity. A PEDOT:PSS film sequentially treated with H₂SO₄ and P2-t-Bu can exhibit a Seebeck coefficient of 81.7 µV K^-1, an electrical conductivity of 1265.3 S cm^-1, and a low thermal conductivity of 0.42 W m^-1 K^-1, yielding a power factor of 845.3 µW m^-1 K^-2 and a high room-temperature ZT value of 0.60 for solid organic thermoelectric materials. Spectroscopic and electronic structure analyses reveal that the exceptional TE performance originates from synergistic dedoping and lower-polaron-level splitting induced by the coupling between the polarons of PEDOT and the lone electron pairs of P2-t-Bu. This work establishes organic superbase engineering as an effective strategy for high-performance organic thermoelectrics.