Poly(3,4-ethylenedioxythiophene)
(PEDOT) is certainly the most
known and most used conductive polymer because it is commercially
available and shows great potential for organic electronic, photovoltaic,
and thermoelectric applications. Studies dedicated to PEDOT films
have led to high conductivity enhancements. However, an exhaustive
understanding of the mechanisms governing such enhancement is still
lacking, hindered by the semicrystalline nature of the material itself.
In this article, we report the development of highly conductive PEDOT
films by controlling the crystallization of the PEDOT chains and by
a subsequent dopant engineering approach using iron(III) trifluoromethanesulfonate
as oxidant, N-methyl pyrrolidone as polymerization
rate controller and sulfuric acid as dopant. XRD, HRTEM, Synchrotron
GIWAXS analyses and conductivity measurements down to 3 K allowed
us to unravel the organization, doping, and transport mechanism of
these highly conductive PEDOT materials. N-methyl
pyrrolidone promotes bigger crystallites and structure enhancement
during polymerization, whereas sulfuric acid treatment allows the
replacement of triflate anions by hydrogenosulfate and increases the
charge carrier concentration. We finally propose a charge transport
model that fully corroborates our experimental observations. These
polymers exhibit conductivities up to 5400 S cm–1 and thus show great promise for room temperature thermoelectric
applications or ITO alternative for transparent electrodes.
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