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An ab-initio framework for phonon-mediated exciton diffusion in crystals

ORAL

Abstract

The dynamics of excitons in complex materials upon photoexcitation are important for energy applications, e.g., light-emitting diodes and photovoltaics. As a specific example, in organic photovoltaics, strongly-bound photo-excited excitons must diffuse to donor-acceptor interfaces where charge separation may occur before the rest of the energy conversion process can proceed. Describing phonon-mediated exciton transport in these materials is complicated by the fact that exciton bandwidth and exciton-phonon coupling strengths are similar in magnitude. In turn it is unclear a priori whether exciton diffusion is best described by phonon-limited Boltzmann-like or thermally activated hopping-like theories. In this talk, using density functional perturbation theory and the ab initio Bethe-Salpeter equation approach, we describe a self-contained framework for computing exciton diffusion coefficients in both the band-like and hopping regimes. Our reciprocal-space based, linear response method explicitly takes into account the entire crystalline environment and can seamlessly be applied to study both spin-singlet and -triplet excitations. We apply our method to a select set of acene crystals shedding additional light on microscopic origins of exciton diffusion in these classic materials. 

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Presenters

  • Jonah B Haber

    University of California, Berkeley, University of California, Berkeley; Lawrence Berkeley National Laboratory, Department of Physics, University of California, Berkeley, Department of Physics, University of California, Berkeley, CA 94720; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.

Authors

  • Jonah B Haber

    University of California, Berkeley, University of California, Berkeley; Lawrence Berkeley National Laboratory, Department of Physics, University of California, Berkeley, Department of Physics, University of California, Berkeley, CA 94720; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.

  • Felipe H da Jornada

    Stanford Univ, Stanford University

  • Sivan Refaely-Abramson

    Weizmann Institute of Science

  • Diana Y Qiu

    Yale University

  • Gabriel Antonius

    Université du Québec à Trois-Rivières (UQTR), Université du Québec à Trois-Rivières, Université du Québec à Trois-Rivières, Trois-Rivières, Qc, Canada

  • Steven G Louie

    University of California at Berkeley, and Lawrence Berkeley National Laboratory, Physics Department, UC Berkeley and Lawrence Berkeley National Lab, University of California Berkeley, University of California, Berkeley, University of California at Berkeley; Lawrence Berkeley National Laboratory, University of California at Berkeley and Lawrence Berkeley National Laboratory, UC berkeley, University of California at Berkeley and Lawrence Berkeley National Lab, UC Berkeley & Lawrence Berkeley National Laboratory

  • Jeffrey B Neaton

    Lawrence Berkeley National Laboratory, University of California, Berkeley; Lawrence Berkeley National Laboratory; Kavli Energy NanoSciences Institute at Berkeley, Department of Physics, University of California, Berkeley; Materials Sciences Division, Lawrence Berkeley National Laboratory; Kavli Energy NanoScience Institute at Berkeley, Department of Physics, University of California, Berkeley, CA 94720; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720; Kavli Energy Nano