Giant Bandgap Renormalization and Exciton-Phonon Scattering in Perovskite Nanocrystals

Rinku Saran, Amelie Heuer-Jungemann, Antonios G. Kanaras, Richard J. Curry

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    Abstract

    Understanding the interactions between photoexcited charge carriers (electrons and holes) with lattice vibrations (phonons) in quantum confined semiconductor nanocrystals (NCs) is of fundamental interest and a prerequisite for their use in fabricating high-performance optoelectronic devices. Such interactions have a significant impact on their optoelectronic properties including their charge carrier mobility and photoluminescence. Here, we investigate these interactions in cesium lead halide (CsPbX3, where X is Cl, Br or I) NC perovskites. We show that a wide broadening of the excitonic linewidth in these NCs arises from strong exciton-phonon coupling, which is substantially dominated by longitudinal optical phonons via the Fröhlich interaction. Unlike the behavior of conventional semiconductors these NCs display a general red-shift of their emission energy peak with reducing temperature. Interestingly, the CsPbCl3 NCs also display an initial blue-shift and undergo at structural phase transition at ~175 K to 200 K. The anomalous red-shift observed is modeled and analyzed using a Bose-Einstein two-oscillator model to interpret the interaction of excitons with acoustic and optical phonons which induce a renormalization of the bandgap. The net renormalization due to zero point motion (T= 0 K) was found to be ~41.6 meV and ~94.9 meV for CsPbBr3 and CsPbI3 NCs respectively.
    Original languageEnglish
    Article numberadom.201700231R1
    JournalAdvanced Optical Materials
    Volume5
    Issue number17
    Early online date26 Jun 2017
    DOIs
    Publication statusPublished - 2017

    Keywords

    • exciton-phonon interactions
    • bandgap renormalization
    • perovskites
    • nanocrystals
    • cesium lead halides

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