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dc.contributor.author
Shi, Xingyuan
dc.contributor.author
Nádaždy, Vojtech
dc.contributor.author
Perevedentsev, Aleksandr
dc.contributor.author
Frost, Jarvist M.
dc.contributor.author
Wang, Xuhua
dc.contributor.author
von Hauff, Elizabeth
dc.contributor.author
MacKenzie, Roderick C.I.
dc.contributor.author
Nelson, Jenny
dc.date.accessioned
2019-06-12T10:30:15Z
dc.date.available
2019-06-11T02:15:34Z
dc.date.available
2019-06-12T10:30:15Z
dc.date.issued
2019
dc.identifier.issn
2160-3308
dc.identifier.other
10.1103/PhysRevX.9.021038
en_US
dc.identifier.uri
http://hdl.handle.net/20.500.11850/346535
dc.identifier.doi
10.3929/ethz-b-000346535
dc.description.abstract
Charge transport in π-conjugated polymers is characterized by a strong degree of disorder in both the energy of conjugated segments and the electronic coupling between adjacent sites. This disorder arises from variations in the structure and conformation of molecular units, as well as the weak intermolecular binding interactions. Although disorder in molecular conformation can be expected to influence the density of states (DOS) distribution—and hence, optoelectronic properties of the material—until now, there has been no direct study of the relationship between a distinct conformational defect and the charge transport properties of a conjugated polymer. Here, we investigate the impact of introducing an extended, planarized chain geometry, known as the “β-phase,” on hole transport through otherwise amorphous films of poly(9,9-dioctylfluorene) (PFO). We show that while β-phase introduces a striking drop of about a hundredfold in time-of-flight (TOF) hole mobility (μh) at room temperature, it reduces the steady-state μh measured from hole-only devices by a factor of less than about 5. In order to reconcile these observations, we combine high-dynamic-range TOF photocurrent spectroscopy and energy-resolved electrochemical impedance spectroscopy to extract the hole DOS of the conjugated polymer. Both methods show that the effect of the β-phase content is to introduce a sharp sub-bandgap feature into the DOS of glassy PFO lying about 0.3 eV above the highest occupied molecular orbital. The observed energy of the conformational trap is consistent with electronic structure calculations using a tight-binding approach. Using the obtained DOS with a drift-diffusion model capable of resolving charge carriers in both time and energy, we show how the seemingly contradictory transport phenomena obtained via the time-resolved, frequency-resolved, and steady-state methods are reconciled. The results highlight the significance of energetic redistribution of charge carriers in affecting transport behavior. This work demonstrates how charge-carrier mobility in organic semiconductors can be controlled via molecular conformation, and it resolves a long-standing debate over how different (equilibrium versus nonequilibrium) transport techniques reveal electronic properties of disordered solids in a unified manner.
en_US
dc.format
application/pdf
en_US
dc.language.iso
en
en_US
dc.publisher
American Institute of Physics
en_US
dc.rights.uri
http://creativecommons.org/licenses/by/4.0/
dc.title
Relating Chain Conformation to the Density of States and Charge Transport in Conjugated Polymers: The Role of the β-phase in Poly(9,9-dioctylfluorene)
en_US
dc.type
Journal Article
dc.rights.license
Creative Commons Attribution 4.0 International
dc.date.published
2019-05-24
ethz.journal.title
Physical Review X
ethz.journal.volume
9
en_US
ethz.journal.issue
2
en_US
ethz.journal.abbreviated
Phys. rev., X
ethz.pages.start
021038
en_US
ethz.size
30 p.
en_US
ethz.version.deposit
publishedVersion
en_US
ethz.identifier.wos
ethz.identifier.scopus
ethz.publication.place
Woodbury, NY
en_US
ethz.publication.status
published
en_US
ethz.date.deposited
2019-06-11T02:15:38Z
ethz.source
WOS
ethz.eth
yes
en_US
ethz.availability
Open access
en_US
ethz.rosetta.installDate
2019-06-12T10:30:26Z
ethz.rosetta.lastUpdated
2020-02-15T19:32:18Z
ethz.rosetta.versionExported
true
ethz.COinS
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