Dresden 2017 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 59: Focus: Static and Dynamic Disorder Phenomena on the Transport in Organic Semiconductors II
CPP 59.3: Vortrag
Donnerstag, 23. März 2017, 16:00–16:15, ZEU 222
Theory of Thermalization and Recombination in Organic Disordered Semiconductors — •Andreas Hofacker1, Dieter Neher2, Koen Vandewal1, and Karl Leo1 — 1Dresden Integrated Center for Applied Physics and Photonic Materials, Dresden University of Technology, D-01069 Dresden — 2Institute of Physics and Astronomy, University of Potsdam, D-14469 Potsdam
Charge carrier recombination in organic disordered semiconductors is strongly influenced by thermalization of charge carriers in the density of states (DOS). Measurements of recombination dynamics, conducted under transient or steady-state conditions, can easily be misinterpreted when a detailed understanding of the interplay of thermalization and recombination is missing. To enable adequate measurement analysis, we solve the multiple-trapping problem for recombining charge carriers and analyze it in the transient and steady excitation paradigm for different DOS distributions.
We show that recombination rates measured after pulsed excitation are inherently time-dependent, since recombination gradually slows down as carriers relax in the DOS. When measuring the recombination order after pulsed excitation, this leads to an apparent high-order recombination at short times. As times goes on, the recombination order approaches an asymptotic value. For the Gaussian and the exponential DOS distributions, this asymptotic value equals the recombination order of the equilibrated system under steady excitation. For a more general DOS distribution, the recombination order can also depend on the carrier density, under both transient and steady-state conditions.