TY - JOUR
T1 - Quantitative Composition and Mesoscale Ion Distribution in p-Type Organic Mixed Ionic-Electronic Conductors
AU - Wu, Ruiheng
AU - Paulsen, Bryan D.
AU - Ma, Qing
AU - McCulloch, Iain
AU - Rivnay, Jonathan
N1 - Funding Information:
R.W., B.P., and J.R. gratefully acknowledge support from the National Science Foundation grant no. NSF DMR-1751308. The synchrotron XRF work was performed at the 5-BM-D beamline of the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT), located at Sector 5 of the Advanced Photon Source (APS). DND-CAT is supported by Northwestern University, The Dow Chemical Company, and DuPont de Nemours, Inc. GISAXS measurements were performed at beamline 8-ID-E of the APS. The APS is a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract no. DE-AC02-06CH11357. This research used the resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract no. DE-AC02-06CH11357. This work utilized the Keck-II facility of Northwestern University’s NUANCE Center, supported by the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205), the Materials Research Science and Engineering Center (NSF DMR-1720139), the State of Illinois, and Northwestern University. Additionally, the Keck-II facility is partially supported by the International Institute for Nanotechnology (IIN), the Keck Foundation, and the State of Illinois through the IIN. This work also utilized the IMSERC facility at Northwestern University. IMSERC is funded by NSF CHE-9871268 (1998) and Northwestern University. Special thanks to Maximilian Moser for providing the materials essential to the characterization of this study.
Publisher Copyright:
© 2023 American Chemical Society.
PY - 2023/6/28
Y1 - 2023/6/28
N2 - Understanding the ionic composition and distribution in organic mixed ionic-electronic conductors (OMIECs) is crucial for understanding their structure-property relationships. Despite this, direct measurements of OMIEC ionic composition and distribution are not common. In this work, we investigated the ionic composition and mesoscopic structure of three typical p-type OMIEC materials: an ethylene glycol-treated crosslinked OMIEC with a large excess fixed anionic charge (EG/GOPS-PEDOT:PSS), an acid-treated OMIEC with a tunable fixed anionic charge (crys-PEDOT:PSS), and a single-component OMIEC without any fixed anionic charge (pg2T-TT). A combination of X-ray fluorescence (XRF) and X-ray photoelectron spectroscopies, gravimetry, coulometry, and grazing incidence small-angle X-ray scattering (GISAXS) techniques was employed to characterize these OMIECs following electrolyte exposure and electrochemical cycling. In particular, XRF provided quantitative ion-to-monomer compositions for these OMIECs from passive ion uptake following aqueous electrolyte exposure and potential-driven ion uptake/expulsion following electrochemical doping and dedoping. Single-ion (cation) transport in EG/GOPS-PEDOT:PSS due to Donnan exclusion was directly confirmed, while significant fixed anion concentrations in crys-PEDOT:PSS doping and dedoping were shown to occur through mixed anion and cation transport. Controlling the fixed anionic (PSS-) charge density in crys-PEDOT:PSS mapped the strength of Donnan exclusion in OMIEC systems following a Donnan-Gibbs model. Anion transport dominated pg2T-TT doping and dedoping, but a surprising degree of anionic charge trapping (∼1020 cm-3) was observed. GISAXS revealed minimal ion segregation both between PEDOT- and PSS-rich domains in EG/GOPS-PEDOT:PSS and between amorphous and semicrystalline domains in pg2T-TT but showed significant ion segregation in crys-PEDOT:PSS at length scales of tens of nm, ascribed to inter-nanofibril void space. These results bring new clarity to the ionic composition and distribution of OMIECs which are crucial for accurately connecting the structure and properties of these materials.
AB - Understanding the ionic composition and distribution in organic mixed ionic-electronic conductors (OMIECs) is crucial for understanding their structure-property relationships. Despite this, direct measurements of OMIEC ionic composition and distribution are not common. In this work, we investigated the ionic composition and mesoscopic structure of three typical p-type OMIEC materials: an ethylene glycol-treated crosslinked OMIEC with a large excess fixed anionic charge (EG/GOPS-PEDOT:PSS), an acid-treated OMIEC with a tunable fixed anionic charge (crys-PEDOT:PSS), and a single-component OMIEC without any fixed anionic charge (pg2T-TT). A combination of X-ray fluorescence (XRF) and X-ray photoelectron spectroscopies, gravimetry, coulometry, and grazing incidence small-angle X-ray scattering (GISAXS) techniques was employed to characterize these OMIECs following electrolyte exposure and electrochemical cycling. In particular, XRF provided quantitative ion-to-monomer compositions for these OMIECs from passive ion uptake following aqueous electrolyte exposure and potential-driven ion uptake/expulsion following electrochemical doping and dedoping. Single-ion (cation) transport in EG/GOPS-PEDOT:PSS due to Donnan exclusion was directly confirmed, while significant fixed anion concentrations in crys-PEDOT:PSS doping and dedoping were shown to occur through mixed anion and cation transport. Controlling the fixed anionic (PSS-) charge density in crys-PEDOT:PSS mapped the strength of Donnan exclusion in OMIEC systems following a Donnan-Gibbs model. Anion transport dominated pg2T-TT doping and dedoping, but a surprising degree of anionic charge trapping (∼1020 cm-3) was observed. GISAXS revealed minimal ion segregation both between PEDOT- and PSS-rich domains in EG/GOPS-PEDOT:PSS and between amorphous and semicrystalline domains in pg2T-TT but showed significant ion segregation in crys-PEDOT:PSS at length scales of tens of nm, ascribed to inter-nanofibril void space. These results bring new clarity to the ionic composition and distribution of OMIECs which are crucial for accurately connecting the structure and properties of these materials.
KW - Donnan−Gibbs model
KW - X-ray fluorescence
KW - ion composition
KW - organic mixed ionic-electronic conductors
UR - http://www.scopus.com/inward/record.url?scp=85164211728&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85164211728&partnerID=8YFLogxK
U2 - 10.1021/acsami.3c04449
DO - 10.1021/acsami.3c04449
M3 - Article
C2 - 37326843
AN - SCOPUS:85164211728
SN - 1944-8244
VL - 15
SP - 30553
EP - 30566
JO - ACS Applied Materials and Interfaces
JF - ACS Applied Materials and Interfaces
IS - 25
ER -