Physics / Fizik

Permanent URI for this collectionhttps://hdl.handle.net/11147/6

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Access type: Open accessAuthor: search.filters.author.Song, Ziyi

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  • Article
    Citation - WoS: 2
    Citation - Scopus: 2
    Highly Mobile Excitons in Single Crystal Methylammonium Lead Tribromide Perovskite Microribbons
    (American Chemical Society, 2022) McClintock, Luke; Song, Ziyi; Travaglini, H. Clark; Senger, Ramazan Tuğrul; Chandrasekaran, Vigneshwaran; Htoon, Han; Yarotski, Dmitry; Yu, Dong
    Excitons are often given negative connotation in solar energy harvesting in part due to their presumed short diffusion lengths. We investigate exciton transport in single-crystal methylammonium lead tribromide (MAPbBr3) microribbons via spectrally, spatially, and temporally resolved photocurrent and photoluminescence measurements. Distinct peaks in the photocurrent spectra unambiguously confirm exciton formation and allow for accurate extraction of the low temperature exciton binding energy (39 meV). Photocurrent decays within a few μm at room temperature, while a gate-tunable long-range photocurrent component appears at lower temperatures (about 100 μm below 140 K). Carrier lifetimes of 1.2 μs or shorter exclude the possibility of the long decay length arising from slow trapped-carrier hopping. Free carrier diffusion is also an unlikely source of the highly nonlocal photocurrent, due to their small fraction at low temperatures. We attribute the long-distance transport to high-mobility excitons, which may open up new opportunities for novel exciton-based photovoltaic applications.
  • Article
    Citation - WoS: 2
    Citation - Scopus: 3
    Transport Modeling of Locally Photogenerated Excitons in Halide Perovskites
    (American Chemical Society, 2021) Tang, Kuen Wai; Li, Senlei; Weeden, Spencer; Song, Ziyi; McClintock, Luke; Xiao, Rui; Senger, Ramazan Tuğrul
    Excitons have fundamental impacts on optoelectronic properties of semiconductors. Halide perovskites, with long carrier lifetimes and ionic crystal structures, may support highly mobile excitons because the dipolar nature of excitons suppresses phonon scattering. Inspired by recent experimental progress, we perform device modeling to rigorously analyze exciton formation and transport in methylammonium lead triiodide under local photoexcitation by using a finite element method. Mobile excitons, coexisting with free carriers, can dominate photocurrent generation at low temperatures. The simulation results are in excellent agreement with the experimentally observed strong temperature and gate dependence of carrier diffusion. This work signifies that efficient exciton transport can substantially influence charge transport in the family of perovskite materials.