Charge carrier concentration dependence of encounter-limited bimolecular recombination in phase-separated organic semiconductor blends

Michael C. Heiber, Thuc-Quyen Nguyen, and Carsten Deibel
Phys. Rev. B 93, 205204 – Published 23 May 2016
PDFHTMLExport Citation

Abstract

Understanding how the complex intermolecular configurations and nanostructure present in organic semiconductor donor-acceptor blends impacts charge carrier motion, interactions, and recombination behavior is a critical fundamental issue with a particularly major impact on organic photovoltaic applications. In this study, kinetic Monte Carlo (KMC) simulations are used to numerically quantify the complex bimolecular charge carrier recombination behavior in idealized phase-separated blends. Recent KMC simulations have identified how the encounter-limited bimolecular recombination rate in these blends deviates from the often used Langevin model and have been used to construct the new power mean mobility model. Here, we make a challenging but crucial expansion to this work by determining the charge carrier concentration dependence of the encounter-limited bimolecular recombination coefficient. In doing so, we find that an accurate treatment of the long-range electrostatic interactions between charge carriers is critical, and we further argue that many previous KMC simulation studies have used a Coulomb cutoff radius that is too small, which causes a significant overestimation of the recombination rate. To shed more light on this issue, we determine the minimum cutoff radius required to reach an accuracy of less than ±10% as a function of the domain size and the charge carrier concentration and then use this knowledge to accurately quantify the charge carrier concentration dependence of the recombination rate. Using these rigorous methods, we finally show that the parameters of the power mean mobility model are determined by a newly identified dimensionless ratio of the domain size to the average charge carrier separation distance.

  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Received 10 March 2016
  • Revised 8 May 2016

DOI:https://doi.org/10.1103/PhysRevB.93.205204

©2016 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Michael C. Heiber1,2,*, Thuc-Quyen Nguyen2,3, and Carsten Deibel1,†

  • 1Institut für Physik, Technische Universität Chemnitz, 09126 Chemnitz, Germany
  • 2Center for Polymers and Organic Solids, University of California, Santa Barbara, California 93106, USA
  • 3Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, USA

  • *heiber@mailaps.org
  • deibel@physik.tu-chemnitz.de

Article Text (Subscription Required)

Click to Expand

Supplemental Material (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand
Issue

Vol. 93, Iss. 20 — 15 May 2016

Reuse & Permissions
Access Options
CHORUS

Article Available via CHORUS

Download Accepted Manuscript
Author publication services for translation and copyediting assistance advertisement

Authorization Required


×
×

Images

×

Sign up to receive regular email alerts from Physical Review B

Log In

Cancel
×

Search


Article Lookup

Paste a citation or DOI

Enter a citation
×