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Correlation of Thermoelectric Performance, Domain Morphology and Doping Level in PEDOT:PSS Thin Films Post‐Treated with Ionic Liquids
Author(s) -
Oechsle Anna Lena,
Heger Julian E.,
Li Nian,
Yin Shanshan,
Bernstorff Sigrid,
MüllerBuschbaum Peter
Publication year - 2021
Publication title -
macromolecular rapid communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 154
eISSN - 1521-3927
pISSN - 1022-1336
DOI - 10.1002/marc.202100397
Subject(s) - pedot:pss , materials science , thermoelectric effect , seebeck coefficient , dicyanamide , ionic liquid , thin film , polystyrene sulfonate , doping , conductive polymer , grazing incidence small angle scattering , chemical engineering , nanotechnology , scattering , optoelectronics , composite material , polymer , organic chemistry , small angle neutron scattering , thermal conductivity , optics , layer (electronics) , chemistry , neutron scattering , engineering , thermodynamics , catalysis , physics
Ionic liquid (IL) post‐treatment of poly(3,4‐ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) thin films with ethyl‐3‐methylimidazolium dicyanamide (EMIM DCA), allyl‐3‐methylimidazolium dicyanamide (AMIM DCA), and 1‐ethyl‐3‐methylimidazolium tetracyanoborate (EMIM TCB) is compared. Doping level modifications of PEDOT are characterized using UV–Vis spectroscopy and directly correlate with the observed Seebeck coefficient enhancement. With conductive atomic force microscopy (c‐AFM) the authors investigate changes in the topographic‐current features of the PEDOT:PSS thin film surface due to IL treatment. Grazing incidence small‐angle X‐ray scattering (GISAXS) demonstrates the morphological rearrangement towards an optimized PEDOT domain distribution upon IL post‐treatment, directly facilitating the interconductivity and causing an increased film conductivity. Based on these improvements in Seebeck coefficient and conductivity, the power factor is increased up to 236 µW m −1 K − 2 . Subsequently, a model is developed indicating that ILs, which contain small, sterically unhindered ions with a strong localized charge, appear beneficial to boost the thermoelectric performance of post‐treated PEDOT:PSS films.