Understanding the Role of Orientational Heterogeneity on Photophysical Properties of Organic Polycrystalline Films

ORAL

Abstract

Organic semiconductors are a highly tunable class of optically active materials that are promising as next-generation photovoltaics. Utilizing these materials for efficient solar energy conversion relies on an understanding of the connection between their excited-state electronic structure and their solid-state morphology. While many organic materials have varying degrees of disorder, crystalline films with long-range order provide an opportunity to understand many fundamental physical properties relevant to solar energy conversion. Here, we use a combined theoretical and experimental approach to investigate the nature of low-energy excitons and their dynamics within 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-Pen) polycrystalline films. First-principles many-body perturbation theory and optical absorption spectroscopy on ordered domains reveal multiple low-energy absorption peaks that are composed of delocalized excitonic states. Further, we examine the nature of excitons in grains of different relative orientations and at grain boundaries, and discuss implications for their dynamics as measured by spatially-resolved transient absorption spectroscopy. This work was supported by DOE; computational resources provided by NERSC.

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Authors

  • Sahar Sharifzadeh

    Lawrence Berkeley National Laboratory, Molecular Foundry, LBNL, Molecular Foundry, Lawrence Berkeley National Laboratory, Molecular Foundry at LBNL, Lawrence Berkeley Natl Lab

  • Cathy Wong

    Dept. Chemistry, UC Berkeley

  • Hao Wu

    Dept. Chemistry, UC Berkeley

  • Naomi Ginsberg

    Dept. Chemistry, UC Berkeley, Univ of California - Berkeley

  • Leeor Kronik

    Department of Materials and Interfaces, Weizmann Institute of Science, Weizmann Institute of Science, Israel, Dept. Materials and Interfaces, Weizmann Institute, Weizmann Institute of Science, Department of Materials and Interfaces, Weizmann Institute of Science, Rehovoth 76100, Israel, Dept. of Materials and Interfaces, Weizmann Institute of Science, Rehovot 7610001, Department of Materials and Interfaces, Weizmann Institute of Science, Israel

  • Jeffery B. Neaton

    Department of Physics, UC-Berkeley; Molecular Foundry, LBNL, Molecular Foundry, LBNL, Department of Physics, UC Berkeley, Molecular Foundry, LBNL and Dept. Physics, UC Berkeley, Molecular Foundry, Lawrence Berkeley National Laboratory and Department of Physics, University of California, Berkeley, UC Berkeley, Dept of Physics; Materials Science Division, LBNL, Molecular Foundry, Lawrence Berkeley National Laboratory; Department of Physics, UC-Berkeley, The Molecular Foundry, LBNL; Dept. of Physics, University of California, Berkeley, Lawrence Berkeley National Laboratory, UC Berkeley Department of Physics, Lawrence Berkeley Natl Lab and Department of Physics, UC-Berkeley, Physics Department, UC Berkeley; Molecular Foundry, Lawrence Berkeley National Lab