title: Exciton quenching close to polymer-vacuum interface of spin-coated films of poly(p-phenylenevinylene) derivative.
abstract: Polymer-fullerene bilayer heterostructures are suited to study excitonic processes in conjugated polymers. Excitons are efficiently quenched at the polymer-fullerene interface, whereas the polymer-vacuum interface is often considered as an exciton-reflecting interface. Here, we report about efficient exciton quenching close to the polymer-vacuum interface of spin-coated MDMO-PPV (poly[2-methoxy-5-(2'-ethyl-hexyloxy)-p-phenylenevinylene]) films. The quenching efficiency is estimated to be as high as that of the polymer-fullerene interface. This efficient quenching is consistent with enhanced intermolecular interactions close to the polymer-vacuum interface due to the formation of a "skin layer" during the spin-coating procedure. In the skin layer, the polymer density is higher; that is, the intermolecular distances are shorter than in the rest of the film. The effect of exciton quenching at the polymer-vacuum interface should be taken into account when the thickness of the polymer film is on the order of the exciton diffusion length; in particular, in the determination of the exciton diffusion length.
authors.affiliation: Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands. O.Mikhnenko@rug.nl
authors.forename: Oleksandr V
authors.initials: OV
authors.lastname: Mikhnenko
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Cordella
authors.forename: Alexander B
authors.initials: AB
authors.lastname: Sieval
authors.forename: Jan C
authors.initials: JC
authors.lastname: Hummelen
authors.forename: Paul W M
authors.initials: PW
authors.lastname: Blom
authors.forename: Maria Antonietta
authors.initials: MA
authors.lastname: Loi