title: Correlating structure with fluorescence emission in phase-separated conjugated-polymer blends.
abstract: Blends of conjugated polymers are frequently used as the active semiconducting layer in light-emitting diodes and photovoltaic devices. Here we report the use of scanning near-field optical microscopy, scanning force microscopy and nuclear-reaction analysis to study the structure of a thin film of a phase-separated blend of two conjugated polymers prepared by spin-casting. We show that in addition to the well-known micrometre-scale phase-separated morphology of the blend, one of the polymers preferentially wets the surface and forms a 10-nm-thick, partially crystallized wetting layer. Using near-field microscopy we identify unexpected changes in the fluorescence emission from the blend that occurs in a 300-nm-wide band located at the interface between the different phase-separated domains. Our measurements provide an insight into the complex structure of phase-separated conjugated-polymer thin films. Characterizing and controlling the properties of the interfaces in such films will be critical in the further development of efficient optoelectronic devices.
authors.affiliation: Department of Physics and Astronomy, The University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, UK.
authors.forename: John
authors.initials: J
authors.lastname: Chappell
authors.forename: David G
authors.initials: DG
authors.lastname: Lidzey
authors.forename: Paul C
authors.initials: PC
authors.lastname: Jukes
authors.forename: Anthony M
authors.initials: AM
authors.lastname: Higgins
authors.forename: Richard L
authors.initials: RL
authors.lastname: Thompson
authors.forename: Stephen
authors.initials: S
authors.lastname: O'Connor
authors.forename: Ilaria
authors.initials: I
authors.lastname: Grizzi
authors.forename: Robert
authors.initials: R
authors.lastname: Fletcher
authors.forename: Jim
authors.initials: J
authors.lastname: O'Brien
authors.forename: Mark
authors.initials: M
authors.lastname: Geoghegan
authors.forename: Richard A L
authors.initials: RA
authors.lastname: Jones
mesh_terms: D003460:Crystallization / Q000379:methods*; D003461:Crystallography / Q000379:methods*; D004563:Electrochemistry / Q000295:instrumentation / Q000379:methods; D005449:Fluorenes / Q000737:chemistry*; D005453:Fluorescence; D036103:Nanotechnology / Q000295:instrumentation / Q000379:methods*; D010777:Photochemistry / Q000295:instrumentation / Q000379:methods; D011108:Polymers / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013223:Statistics as Topic; D013329:Structure-Activity Relationship; D013499:Surface Properties; D013830:Thiadiazoles / Q000737:chemistry*
chemical_list: D005449:Fluorenes; D011108:Polymers; D013830:Thiadiazoles; C015700:benzo-1,2,3-thiadiazole