title: Optical Dedoping Mechanism for P3HT:F4TCNQ Mixtures.
abstract: Doping-induced solubility control (DISC) is a recently introduced photolithographic technique for semiconducting polymers, which utilizes reversible changes in polymer solubility upon doping to allow the polymer to function as its own photoresist. Central to this process is a wavelength sensitive optical dedoping reaction, which is poorly understood but generates subdiffraction-limited topographic features and provides optical control of the polymer doping level. Here, we examine the mechanism of optical dedoping in the semiconducting polymer poly-3-hexylthiophene (P3HT) doped by 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), via a combination of ultrafast and steady-state spectroscopy, ab initio calculations, and multidimensional NMR. A simple photoinduced back electron transfer mechanism from reduced F4TCNQ to oxidized P3HT does not explain the observed photophysics. Instead, photoexcited F4TCNQ* reacts with THF solvent molecules to form a neutral, nondoping, and highly soluble F4TCNQ-THF complex. Hence, ionized F4TCNQ is removed from the P3HT indirectly by depletion of the neutral F4TCNQ. Because the reaction involves only the dopant and similar photoreactivity would expected for most other dopant molecules, we expect optical DISC patterning should be generalizable to a wide range of polymer:dopant systems.
authors.affiliation: Department of Chemistry, University of California, Davis , 1 Shields Avenue, Davis, California 95616, United States.
authors.forename: Jack
authors.initials: J
authors.lastname: Fuzell
authors.affiliation: Department of Materials Science, University of California, Davis , 1 Shields Avenue, Davis, California 95616, United States.
authors.forename: Ian E
authors.initials: IE
authors.lastname: Jacobs
authors.affiliation: Department of Chemistry, School of Physical Sciences, The University of Adelaide , Adelaide, South Australia 5005, Australia.
authors.forename: Sophia
authors.initials: S
authors.lastname: Ackling
authors.affiliation: Department of Chemical Engineering, University of California, Davis , 1 Shields Avenue, Davis, California 95616, United States.
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Harrelson
authors.affiliation: Department of Chemistry, School of Physical Sciences, The University of Adelaide , Adelaide, South Australia 5005, Australia.
authors.forename: David M
authors.initials: DM
authors.lastname: Huang
authors.affiliation: Department of Chemistry, University of California, Davis , 1 Shields Avenue, Davis, California 95616, United States.
authors.forename: Delmar
authors.initials: D
authors.lastname: Larsen
authors.affiliation: Department of Chemistry, University of California, Davis , 1 Shields Avenue, Davis, California 95616, United States.|Department of Chemical Engineering, University of California, Davis , 1 Shields Avenue, Davis, California 95616, United States.
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Moulé