Coulomb Screening and Coherent Phonon in Methylammonium Lead Iodide Perovskites

He Wang, Leonas Valkunas, Thu Cao, Luisa Whittaker-Brooks, Graham R. Fleming

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


Methylammonium lead iodide (CH3NH3PbI3) hybrid perovskite in the tetragonal and orthorhombic phases have different exciton binding energies and demonstrate different excitation kinetics. Here, we explore the role that crystal structure plays in the kinetics via fluence dependent transient absorption spectroscopy. We observe stronger saturation of the free carrier concentration under high pump energy density in the orthorhombic phase relative to the tetragonal phase. We attribute this phenomenon to small dielectric constant, large exciton binding energy, and weak Coulomb screening, which results in difficult exciton dissociation under high light intensity in the orthorhombic phase. At higher excitation intensities, we observe a coherent phonon with an oscillation frequency of 23.4 cm-1 at 77 K, whose amplitude tracks the increase of the first-order lifetime.

Original languageEnglish (US)
Pages (from-to)3284-3289
Number of pages6
JournalJournal of Physical Chemistry Letters
Issue number16
StatePublished - Aug 18 2016
Externally publishedYes

ASJC Scopus subject areas

  • Materials Science(all)
  • Physical and Theoretical Chemistry


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