title: Molecular packing of high-mobility diketo pyrrolo-pyrrole polymer semiconductors with branched alkyl side chains.
abstract: We describe a series of highly soluble diketo pyrrolo-pyrrole (DPP)-bithiophene copolymers exhibiting field effect hole mobilities up to 0.74 cm(2) V(-1) s(-1), with a common synthetic motif of bulky 2-octyldodecyl side groups on the conjugated backbone. Spectroscopy, diffraction, and microscopy measurements reveal a transition in molecular packing behavior from a preferentially edge-on orientation of the conjugated plane to a preferentially face-on orientation as the attachment density of the side chains increases. Thermal annealing generally reduces both the face-on population and the misoriented edge-on domains. The highest hole mobilities of this series were obtained from edge-on molecular packing and in-plane liquid-crystalline texture, but films with a bimodal orientation distribution and no discernible in-plane texture exhibited surprisingly comparable mobilities. The high hole mobility may therefore arise from the molecular packing feature common to the entire polymer series: backbones that are strictly oriented parallel to the substrate plane and coplanar with other backbones in the same layer.
authors.affiliation: Polymers Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States.
authors.forename: Xinran
authors.initials: X
authors.lastname: Zhang
authors.forename: Lee J
authors.initials: LJ
authors.lastname: Richter
authors.forename: Dean M
authors.initials: DM
authors.lastname: DeLongchamp
authors.forename: R Joseph
authors.initials: RJ
authors.lastname: Kline
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Hammond
authors.forename: Iain
authors.initials: I
authors.lastname: McCulloch
authors.forename: Martin
authors.initials: M
authors.lastname: Heeney
authors.forename: Raja S
authors.initials: RS
authors.lastname: Ashraf
authors.forename: Jeremy N
authors.initials: JN
authors.lastname: Smith
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Anthopoulos
authors.forename: Bob
authors.initials: B
authors.lastname: Schroeder
authors.forename: Yves H
authors.initials: YH
authors.lastname: Geerts
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Fischer
authors.forename: Michael F
authors.initials: MF
authors.lastname: Toney
mesh_terms: D015394:Molecular Structure; D010316:Particle Size; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry*; D012666:Semiconductors; D013237:Stereoisomerism; D013499:Surface Properties; D013876:Thiophenes / Q000737:chemistry
chemical_list: D011108:Polymers; D011758:Pyrroles; D013876:Thiophenes