title: Hot-carrier cooling and photoinduced refractive index changes in organic-inorganic lead halide perovskites.
abstract: Metal-halide perovskites are at the frontier of optoelectronic research due to solution processability and excellent semiconductor properties. Here we use transient absorption spectroscopy to study hot-carrier distributions in CH3NH3PbI3 and quantify key semiconductor parameters. Above bandgap, non-resonant excitation creates quasi-thermalized carrier distributions within 100 fs. During carrier cooling, a sub-bandgap transient absorption signal arises at ∼ 1.6 eV, which is explained by the interplay of bandgap renormalization and hot-carrier distributions. At higher excitation densities, a 'phonon bottleneck' substantially slows carrier cooling. This effect indicates a low contribution from inelastic carrier-impurity or phonon-impurity scattering in these polycrystalline materials, which supports high charge-carrier mobilities. Photoinduced reflectivity changes distort the shape of transient absorption spectra and must be included to extract physical constants. Using a simple band-filling model that accounts for these changes, we determine a small effective mass of mr=0.14 mo, which agrees with band structure calculations and high photovoltaic performance.
authors.affiliation: Cavendish Laboratory, Department of Physics, JJ Thomson Avenue, Cambridge, CB3 0HE, United Kingdom.
authors.forename: Michael B
authors.initials: MB
authors.lastname: Price
authors.affiliation: The MacDiarmid Institute for Advanced Materials and Nanotechnology, and School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6140, New Zealand.
authors.forename: Justinas
authors.initials: J
authors.lastname: Butkus
authors.affiliation: Cavendish Laboratory, Department of Physics, JJ Thomson Avenue, Cambridge, CB3 0HE, United Kingdom.
authors.forename: Tom C
authors.initials: TC
authors.lastname: Jellicoe
authors.affiliation: Cavendish Laboratory, Department of Physics, JJ Thomson Avenue, Cambridge, CB3 0HE, United Kingdom.
authors.forename: Aditya
authors.initials: A
authors.lastname: Sadhanala
authors.affiliation: The MacDiarmid Institute for Advanced Materials and Nanotechnology, and School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6140, New Zealand.
authors.forename: Anouk
authors.initials: A
authors.lastname: Briane
authors.affiliation: The MacDiarmid Institute for Advanced Materials and Nanotechnology, and School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6140, New Zealand.
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Halpert
authors.affiliation: Cavendish Laboratory, Department of Physics, JJ Thomson Avenue, Cambridge, CB3 0HE, United Kingdom.
authors.forename: Katharina
authors.initials: K
authors.lastname: Broch
authors.affiliation: The MacDiarmid Institute for Advanced Materials and Nanotechnology, and School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6140, New Zealand.
authors.forename: Justin M
authors.initials: JM
authors.lastname: Hodgkiss
authors.affiliation: Cavendish Laboratory, Department of Physics, JJ Thomson Avenue, Cambridge, CB3 0HE, United Kingdom.
authors.forename: Richard H
authors.initials: RH
authors.lastname: Friend
authors.affiliation: Cavendish Laboratory, Department of Physics, JJ Thomson Avenue, Cambridge, CB3 0HE, United Kingdom.
authors.forename: Felix
authors.initials: F
authors.lastname: Deschler