Session Q49: Focus Session: Organic Electronics and Photonics - Photophysics and Excited State Dynamics

11:15 AM–2:15 PM, Wednesday, February 29, 2012
Room: 162A

Sponsoring Units: DMP DPOLY
Chair: Russell Holmes, University of Minnesota

Abstract ID: BAPS.2012.MAR.Q49.12

Abstract: Q49.00012 : Exciton self-trapping and Stark effect in the optical response of pentacene crystals from first principles

1:27 PM–1:39 PM

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Authors:

  David A. Strubbe
    (Department of Physics, University of California, Berkeley; Materials Sciences Division, Lawrence Berkeley National Laboratory)

  Sahar Sharifzadeh
    (Molecular Foundry, LBNL)

  Jeffrey B. Neaton
    (Molecular Foundry, LBNL)

  Steven G. Louie
    (Physics Dept., UC Berkeley; MSD and MF, LBNL)

Pentacene is a prototypical organic semiconductor with optoelectronic and photovoltaic applications. It is known that the lowest-energy singlet excitation has a Stokes shift between absorption and emission of about 0.14 eV, but the deformation associated with this self-trapped exciton remains unknown. We begin with a calculation of the optical properties via the first-principles GW/Bethe-Salpeter (BSE) theory [ML Tiago, JE Northrup, and SG Louie, Phys. Rev. B 67, 115212 (2003); S Sharifzadeh, A Biller, L Kronik, and JB Neaton, arXiv:1110.4928 (2011)]. We then study the self-trapping phenomenon via our reformulation of the Bethe-Salpeter excited-state forces approximation of Ismail-Beigi and Louie [Phys. Rev. Lett. 90, 076401 (2003)], which can describe the structural relaxation after optical excitation. Whether excitons in pentacene have charge-transfer character has been controversial in electro-absorption experiments. We use the same BSE analytic derivatives approach to calculate the changes in excitation energies due to an applied electric field to understand this experimental controversy.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2012.MAR.Q49.12