Structural modulation induced by cobalt‐based ionic liquids for enhanced thermoelectric transport in PEDOT:PSS

Abstract

Poly(3,4ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS) has been intensively studied for its thermoelectric applications. Structural modulation to improve crystalline ordering, chain conformation and film morphology is a promising way to decouple the trade‐off between conductivity and Seebeck coefficient and thus improve the thermoelectric power factor. Post treatment with ionic liquid ([CoCl2 ⋅ 6H2O]:[ChCl]) bearing cobalt‐containing anions resulted in a remarkable enhancement of the power factor to 76.8 μW m−1 K−2. This IL combines the influence of a high‐boiling polar organic solvent and diffusing ions. A high σ mainly resulted from the efficient removal of PSS chains, ordering of the structure and delocalization of bipoloran‐dominant transport after conformational change. The increase in S was not due to dedoping of PEDOT chains, but rather the sharp feature of the density of states at the Fermi level induced by ion‐exchange with unconventional anions.

Effects of cation size on thermoelectricity of PEDOT:PSS/ionic liquid hybrid films for wearable thermoelectric generator application

“…40 Later Kee et al reported that ionic liquids consisting of EMIM DCA or EMIM DCl can manipulate the doping level and nanostructure of PEDOT:PSS through ion exchange, which leads to a remarkable increase in the conductivity and Seebeck coefficient (up to 538 S cm À1 and 35 mV K À1 , respectively). 41 Similar contributions have been realized for PEDOT:PSS lms constructed by ionic liquid coatings based on BMIM or EMIM cations with various anions; [42][43][44][45][46][47][48][49][50][51][52][53] and their thermoelectric performances are summarized in Table S1. † The addition of or treatment with these ionic liquids in previous studies indicates the direction for manipulating the thermoelectric performance.…”