Dresden 2003 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
CPP: Chemische Physik und Polymerphysik
CPP 20: POSTER A
CPP 20.52: Poster
Montag, 24. März 2003, 19:00–21:00, ZEU/250
Anisotropy of charge carrier generation in polyfluorene — •Achmad Zen1, D. Neher1, C. Bauer2, U. Asawapirom3, U. Scherf3, R. Hagen4, S. Kostromine4, and R.F. Mahrt5 — 1Universität Potsdam, Experimentalphysik, Am Neuen Palais 10, Potsdam — 2Universität Marburg, Institut für Physik, Renthof 5, Marburg — 3Bergische Universität Wuppertal, Makromolekulare Chemie, Gaußstr. 20, Wuppertal — 4Bayer AG, Leverkusen — 5IBM Research, Saeumerstr. 4, Rueschlikon
Sandwich devices consisting of 50 nm aligned polyfluorene as active layer were constructed on top of 15 nm photo-oriented photoaddressable polymers. In order to investigate the origin of the charge generation processes, characterisation using illumination from both electrodes were performed. Upon illumination through the ITO electrode, the diodes exhibit a pronounced dependence of the photocurrent on the polarization of the incident light, yielding a polarization sensitivity of more than a factor of 10 at the onset of the absorption. However, the spectra could not be explained with the commonly used Ghosh-model. In fact, the spectra for illumination through ITO are largely governed by the refractive index dispersion. Combined with the analysis of spectra measured through the Al top electrode, the following two conclusions could be drawn. First, there is a non-active zone of ca. 15 nm extending from the Al cathode into the polyfluorene layer. Second, the photogeneration efficiency for light polarized perpendicular to the chains is ca. two times larger than for light polarized parallel to the alignment direction.
[1] A. Zen et al., Apl. Phys. Lett. 80 (2002) 4699