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Effect of Additives on the Surface Morphology, Energetics, and Contact Resistance of PEDOT:PSS.

Authors :
Chen AX
Esparza GL
Simon I
Dunfield SP
Qie Y
Bunch JA
Blau R
Lim A
Zhang H
Brew SE
O'Neill FM
Fenning DP
Lipomi DJ
Source :
ACS applied materials & interfaces [ACS Appl Mater Interfaces] 2023 Aug 09; Vol. 15 (31), pp. 38143-38153. Date of Electronic Publication: 2023 Jul 27.
Publication Year :
2023

Abstract

For a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) film employed in a device stack, charge must pass through both the bulk of the film and interfaces between adjacent layers. Thus, charge transport is governed by both bulk and contact resistances. However, for ultrathin films (e.g., flexible devices, thin-film transistors, printed electronics, solar cells), interfacial properties can dominate over the bulk properties, making contact resistance a significant determinant of device performance. For most device applications, the bulk conductivity of PEDOT:PSS is typically improved by blending additives into the solid film. Doping PEDOT:PSS with secondary dopants (e.g., polar small molecules), in particular, increases the bulk conductivity by inducing a more favorable solid morphology. However, the effects of these morphological changes on the contact resistance (which play a bigger role at smaller length scales) are relatively unstudied. In this work, we use transfer length method (TLM) measurements to decouple the bulk resistance from the contact resistance of PEDOT:PSS films incorporating several common additives. These additives include secondary dopants, a silane crosslinker (typically used to stabilize the PEDOT:PSS film), and multi-walled carbon nanotubes (conductive fillers). Using conductive atomic force microscopy, Kelvin probe force microscopy, Raman spectroscopy, and photoelectron spectroscopy, we connect changes in the contact resistance to changes in the surface morphology and energetics as governed by the blended additives. We find that the contact resistance at the PEDOT:PSS/silver interface can be reduced by (1) increasing the ratio of PEDOT to PSS chains, (2) decreasing the work function, (3) decreasing the benzoid-to-quinoid ratio at the surface of the solid film, (4) increasing the film uniformity and contact area, and (5) increasing the phase-segregated morphology of the solid film.

Details

Language :
English
ISSN :
1944-8252
Volume :
15
Issue :
31
Database :
MEDLINE
Journal :
ACS applied materials & interfaces
Publication Type :
Academic Journal
Accession number :
37499172
Full Text :
https://doi.org/10.1021/acsami.3c08341