Great Enhancement in the Seebeck Coefficient of PEDOT:PSS by Polaron Level Splitting via π–π Overlapping with Nonpolar Small Aromatic Molecules

Abstract

Organic thermoelectric (TE) materials are regarded as the next‐generation TE materials because of their merits including low cost, high mechanical flexibility, and low intrinsic thermal conductivity. However, their Seebeck coefficient is usually quite low. Herein, a new strategy is demonstrated to greatly enhance the Seebeck coefficient of poly(3,4‐ethylenedioxy‐thiophene):poly(styrenesulfonate) (PEDOT:PSS), which is the most popular TE polymer, through polaron level splitting via π–π overlapping with nonpolar small aromatic molecules including anthracene, naphthalene, and pyrene. Although these aromatic molecules are neither oxidizing nor reducing agent, they can greatly enhance the Seebeck coefficient of PEDOT:PSS films pre‐treated with dimethyl sulfoxide, acid, or acid then base, while they do not lower the electrical conductivity too much. Through such a treatment with anthracene, the Seebeck coefficient can be up to 45.5 µV K−1, and the ZT value can be up to 0.27. The enhancement is ascribed to the splitting of the lower polaron energy level of PEDOT, which is induced by the π–π overlapping between the aromatic compounds and conjugated PEDOT. This can shift up the Fermi level, thereby enhancing the Seebeck coefficient.

Lightweight, elastic and conductive pure PEDOT:PSS foam for dual-mode sensing

“…2b and S6,† the characteristic peaks in the XPS spectrum of PEDOT:PSS foam between 170–166 eV are related to the S atoms in PSS, while the two characteristic peaks at 162–166 eV are related to the S atoms in PEDOT. 23 The intensity ratio of the characteristic peaks of PSS and PEDOT in SBLPP foam is 1.39, much lower than those of BLPP foam (2.15) and the original PEDOT:PSS aqueous solution (2.9), indicating that PSS is removed during the hydrothermal self-assembly process, facilitating the crosslinking of the enriched PEDOT region. 24 The Raman spectrum (Fig.…”