Regensburg 2016 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 30: Poster: Organic Electronics and Photovoltaics

CPP 30.4: Poster

Dienstag, 8. März 2016, 18:15–21:00, Poster B2

Manipulation and controlling the strength of the interfacial polarisation in OLED devices by doping — •Lars Jäger, Tobias D. Schmidt, and Wolfgang Brütting — Institute of Physics, University of Augsburg, 86135 Augsburg, Germany

Most of the used electron transporting materials in organic light emitting diodes are known to be polar. This property modifies the internal electric field distribution of the device and therefore enables an earlier flat band condition for the hole transporting side, leading to improved charge injection. Recently the interfacial polarisation has been investigated with regard to different materials and degradation effects, however, so far the influence of doping has never been looked at. Here we focus on the behavior in the case of doping of the polar electron transporting layer tris-(8-hydroxyquinolate) aluminum (Alq₃) with the hole transporting material 4,4’-bis[N-(1-naphthyl)-N-phenylamino]-biphenyl (NPB). By evaluating impedance spectroscopy data we can show that the limiting parameter is not the effective Alq₃ thickness. In fact the built up of the polarisation reaches a maximum for a 50% blend. Taking the permanent dipole moments of the molecules into account, an increasing contribution was found for a decreasing Alq₃ amount in the blend. This fact can be explained by a sterically mechanism in addition to the minimization of the dipole-dipole interaction.