PEDOT Nanocrystal in HighlyConductive PEDOT:PSS PolymerFilms.

The nanometer-size crystallization of poly(3,4-ethylenedioxythiophene)(PEDOT) inside the hydrophobic core region of PEDOT:PSS (PSS: poly(4-styrenesulfonate))in a solid film is found by small and wide-angle X-ray scatteringsusing a synchrotron radiation source. The clarified PEDOT:PSS structureindicates that a nanocrystal of PEDOT surrounded by PSS is grown inthe solid film from randomly oriented PEDOT in a micelle dispersedin water during the course of film fabrication. The addition of ethyleneglycol (EG) to the PEDOT:PSS water dispersion and post-treatment ofthe pristine film with EG both provide similar improvements in PEDOTcrystallinity. The crystallite size of PEDOT increases up to a comparablesize (∼4.8 nm) to the hydrophobic PEDOT core region of themicelle. The electrical conductivity of the solid film is concurrentlyenhanced by 2 orders of magnitude with the growing nanocrystal ofPEDOT. These findings clearly demonstrate the importance of the singlecrystalline PEDOT assisted by EG to obtain high electrical conductivityof the PEDOT:PSS solid film. [ABSTRACT FROM AUTHOR]