title: Coulomb Screening and Coherent Phonon in Methylammonium Lead Iodide Perovskites.
abstract: 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.
authors.affiliation: Department of Chemistry, University of California , Berkeley, California 94720, United States.|Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.|Kavli Energy NanoSciences Institute at the UC California, Berkeley, and the Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: He
authors.initials: H
authors.lastname: Wang
authors.affiliation: Theoretical Physics Department, Vilnius University , Vilnius 10222, Lithuania.|Molecular Compound Physics Department, Center for Physical Sciences and Technology , Vilnius 10222, Lithuania.
authors.forename: Leonas
authors.initials: L
authors.lastname: Valkunas
authors.affiliation: Department of Chemistry, University of California , Berkeley, California 94720, United States.|Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.|Kavli Energy NanoSciences Institute at the UC California, Berkeley, and the Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Thu
authors.initials: T
authors.lastname: Cao
authors.affiliation: Department of Chemistry, University of Utah , Salt Lake City, Utah 84112, United States.
authors.forename: Luisa
authors.initials: L
authors.lastname: Whittaker-Brooks
authors.affiliation: Department of Chemistry, University of California , Berkeley, California 94720, United States.|Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.|Kavli Energy NanoSciences Institute at the UC California, Berkeley, and the Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Graham R
authors.initials: GR
authors.lastname: Fleming