Dresden 2009 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 40: POSTERS Electronic and Optical Properties
CPP 40.18: Poster
Donnerstag, 26. März 2009, 17:00–19:30, P3
A model for triplet exciton diffusion in poly(para-phenylene) derivatives — •Anna Köhler1, Sebastian Hoffman1, Lekshmi Sudha Devi1, Michael Forster2, Jan-Moritz Koenen2, and Ullrich Scherf2 — 1Department of Physics, University of Bayreuth, 95440 Bayreuth, Germany — 2Department of Chemistry, Bergische Universität Wuppertal, Wuppertal, Germany
Efficient triplet exciton emission has allowed improved operation of organic light-emitting diodes (LEDs). To enhance the device performance, it is necessary to understand what governs the motion of triplet excitons through the organic semiconductor. We have recently shown that, for an organometallic polymer with low energetic disorder, triplet diffusion can be described in the framework of the Holstein small polaron model.(1,2) It predicts a tunnelling process at low temperatures followed by a thermally activated hopping process above a transition temperature. Using phosphorescence measurements, we have here investigated the dynamics of triplet diffusion in the polyfluorene PF2/6 and the ladder-type poly(para-phenylene) MeLPPP. We find this model is suited to describe the dynamics of triplet diffusion in these organic polymers and oligomers. The dominant parameter that controls the triplet transfer rate is the relative size of polaronic effects to energetic disorder. Experimentally, we show that the triplet diffusion rate increases with decreasing geometric relaxation energy and disorder.
(1) L. Sudha Devi et al, PRB 78, 45210, 2008. (2) I. I. Fishchuk et al, PRB78, 45211 2008.