title: Aggregation in a high-mobility n-type low-bandgap copolymer with implications on semicrystalline morphology.
abstract: We explore the photophysics of P(NDI2OD-T2), a high-mobility and air-stable n-type donor/acceptor polymer. Detailed steady-state UV-vis and photoluminescence (PL) measurements on solutions of P(NDI2OD-T2) reveal distinct signatures of aggregation. By performing quantum chemical calculations, we can assign these spectral features to unaggregated and stacked polymer chains. NMR measurements independently confirm the aggregation phenomena of P(NDI2OD-T2) in solution. The detailed analysis of the optical spectra shows that aggregation is a two-step process with different types of aggregates, which we confirm by time-dependent PL measurements. Analytical ultracentrifugation measurements suggest that aggregation takes place within the single polymer chain upon coiling. By transferring these results to thin P(NDI2OD-T2) films, we can conclude that film formation is mainly governed by the chain collapse, leading in general to a high aggregate content of ~45%. This process also inhibits the formation of amorphous and disordered P(NDI2OD-T2) films.
authors.affiliation: Institute of Physics and Astronomy, University of Potsdam, D-14476 Potsdam, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Steyrleuthner
authors.forename: Marcel
authors.initials: M
authors.lastname: Schubert
authors.forename: Ian
authors.initials: I
authors.lastname: Howard
authors.forename: Bastian
authors.initials: B
authors.lastname: Klaumünzer
authors.forename: Kristian
authors.initials: K
authors.lastname: Schilling
authors.forename: Zhihua
authors.initials: Z
authors.lastname: Chen
authors.forename: Peter
authors.initials: P
authors.lastname: Saalfrank
authors.forename: Frédéric
authors.initials: F
authors.lastname: Laquai
authors.forename: Antonio
authors.initials: A
authors.lastname: Facchetti
authors.forename: Dieter
authors.initials: D
authors.lastname: Neher