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. 

*This work is supported by the Department of Energy; computational resources provided by NERSC.

–

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