Dispersive and steady-state recombination in organic disordered semiconductors

Andreas Hofacker and Dieter Neher
Phys. Rev. B 96, 245204 – Published 27 December 2017

Abstract

Charge carrier recombination in organic disordered semiconductors is strongly influenced by the 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. We conclude that transient experiments can provide rich information about recombination in and out of equilibrium and the underlying DOS occupation provided that consistent modeling of the system is performed.

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  • Received 25 October 2017
  • Revised 27 November 2017

DOI:https://doi.org/10.1103/PhysRevB.96.245204

©2017 American Physical Society

Physics Subject Headings (PhySH)

Statistical Physics & ThermodynamicsCondensed Matter, Materials & Applied Physics

Authors & Affiliations

Andreas Hofacker1,* and Dieter Neher2,†

  • 1Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, 01187 Dresden, Germany
  • 2Department of Physics and Astronomy, Universität Potsdam, 14476 Potsdam, Germany

  • *andreas.hofacker@tu-dresden.de
  • neher@uni-potsdam.de

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Issue

Vol. 96, Iss. 24 — 15 December 2017

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