Article

Coulomb Screening and Coherent Phonon in Methylammonium Lead Iodide Perovskites

He WangDepartment of Chemistry, University of California, Berkeley, California 94720, United StatesLeonas ValkūnasMolecular Compound Physics Department, Center for Physical Sciences and Technology, Vilnius 10222, LithuaniaThu CaoDepartment of Chemistry, University of California, Berkeley, California 94720, United StatesLuisa Whittaker‐BrooksDepartment of Chemistry, University of Utah, Salt Lake City, Utah 84112, United StatesGraham R. FlemingDepartment of Chemistry, University of California, Berkeley, California 94720, United States

2016en

ABI

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.

Identifiers

DOI: 10.1021/acs.jpclett.6b01425

Citations and references

Cited by 20 references

Metrics — AkademScholar