title: High-Resolution Kelvin Probe Force Microscopy Imaging of Interface Dipoles and Photogenerated Charges in Organic Donor-Acceptor Photovoltaic Blends.
abstract: We present noncontact atomic force microscopy and Kelvin probe force microscopy studies of nanophase segregated photovoltaic blends based on an oligothiophene-fluorenone oligomer and [6,6]-phenyl C70 butyric acid methyl ester. We carried out a complete analysis of the influence of the tip-surface interaction regime on the topographic, in-dark contact potential and surface photovoltage contrasts. It is demonstrated that an optimal lateral resolution is achieved for all channels below the onset of a contrast in the damping images. With the support of electrostatic simulations, it is shown that in-dark contact potential difference contrasts above subsurface acceptor clusters are consistent with an uneven distribution of permanent charges at the donor-acceptor interfaces. A remarkable dependence of the surface photovoltage magnitude with respect to the tip-surface distance is evidenced and attributed to a local enhancement of the electromagnetic field at the tip apex.
authors.forename: Franz
authors.initials: F
authors.lastname: Fuchs
authors.forename: Florent
authors.initials: F
authors.lastname: Caffy
authors.forename: Renaud
authors.initials: R
authors.lastname: Demadrille
authors.affiliation: Institut d'Electronique, Microélectronique et Nanotechnologie (IEMN), CNRS UMR 8520, CS 60069, Avenue Poincaré, 59652 Villeneuve d'Ascq, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Mélin
authors.forename: Benjamin
authors.initials: B
authors.lastname: Grévin
keywords: KPFM; NC-AFM; donor−acceptor interfaces; organic photovoltaics; surface photovoltage