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Title: Tunable Dopants with Intrinsic Counterion Separation Reveal the Effects of Electron Affinity on Dopant Intercalation and Free Carrier Production in Sequentially Doped Conjugated Polymer Films

Journal Article · · Advanced Functional Materials

Carrier mobility in doped conjugated polymers is limited by Coulomb interactions with dopant counterions. This complicates studying the effect of the dopant’s oxidation potential on carrier generation because different dopants have different Coulomb interactions with polarons on the polymer backbone. In this work, dodecaborane (DDB)-based dopants are used, which electrostatically shield counterions from carriers and have tunable redox potentials at constant size and shape. DDB dopants produce mobile carriers due to spatial separation of the counterion, and those with greater energetic offsets produce more carriers. Neutron reflectometry indicates that dopant infiltration into conjugated polymer films is redox-potential-driven. Remarkably, X-ray scattering shows that despite their large 2-nm size, DDBs intercalate into the crystalline polymer lamellae like small molecules, indicating that this is the preferred location for dopants of any size. These findings elucidate why doping conjugated polymers usually produces integer, rather than partial charge transfer: dopant counterions effectively intercalate into the lamellae, far from the polarons on the polymer backbone. Finally, it is shown that the IR spectrum provides a simple way to determine polaron mobility. Overall, higher oxidation potentials lead to higher doping efficiencies, with values reaching 100% for driving forces sufficient to dope poorly crystalline regions of the film.

Research Organization:
Brookhaven National Laboratory (BNL), Upton, NY (United States); Energy Frontier Research Centers (EFRC) (United States). Center for Synthetic Control Across Length-scales for Advancing Rechargeables (SCALAR); SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division; USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities Division
Grant/Contract Number:
SC0012704; CHE-1608957; CBET-1510353; SC0019381; AC02-76SF00515; AC05-00OR22725
OSTI ID:
1633030
Alternate ID(s):
OSTI ID: 1630673; OSTI ID: 1785170
Report Number(s):
BNL-216013-2020-JAAM
Journal Information:
Advanced Functional Materials, Vol. 30, Issue 28; ISSN 1616-301X
Publisher:
WileyCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 60 works
Citation information provided by
Web of Science

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