title: Photo-induced halide redistribution in organic-inorganic perovskite films.
abstract: Organic-inorganic perovskites such as CH3NH3PbI3 are promising materials for a variety of optoelectronic applications, with certified power conversion efficiencies in solar cells already exceeding 21%. Nevertheless, state-of-the-art films still contain performance-limiting non-radiative recombination sites and exhibit a range of complex dynamic phenomena under illumination that remain poorly understood. Here we use a unique combination of confocal photoluminescence (PL) microscopy and chemical imaging to correlate the local changes in photophysics with composition in CH3NH3PbI3 films under illumination. We demonstrate that the photo-induced 'brightening' of the perovskite PL can be attributed to an order-of-magnitude reduction in trap state density. By imaging the same regions with time-of-flight secondary-ion-mass spectrometry, we correlate this photobrightening with a net migration of iodine. Our work provides visual evidence for photo-induced halide migration in triiodide perovskites and reveals the complex interplay between charge carrier populations, electronic traps and mobile halides that collectively impact optoelectronic performance.
authors.affiliation: Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, USA.
authors.forename: Dane W
authors.initials: DW
authors.lastname: deQuilettes
authors.affiliation: Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK.|Mathematical Institute, OCCAM, Woodstock Road, University of Oxford, Oxford OX2 6GG, UK.
authors.forename: Victor M
authors.initials: VM
authors.lastname: Burlakov
authors.affiliation: Department of Bioengineering, University of Washington, Box 351653, Seattle, Washington 98195-1653, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Graham
authors.affiliation: Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
authors.forename: Tomas
authors.initials: T
authors.lastname: Leijtens
authors.affiliation: Research Laboratory of Electronics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Osherov
authors.affiliation: Research Laboratory of Electronics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Bulović
authors.affiliation: Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
authors.forename: Henry J
authors.initials: HJ
authors.lastname: Snaith
authors.affiliation: Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, USA.
authors.forename: David S
authors.initials: DS
authors.lastname: Ginger
authors.affiliation: Research Laboratory of Electronics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.|Cavendish Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE, UK.
authors.forename: Samuel D
authors.initials: SD
authors.lastname: Stranks
mesh_terms: D017610:Calcium Compounds / Q000737:chemistry / Q000528:radiation effects*; D007454:Iodides / Q000737:chemistry / Q000528:radiation effects*; D007455:Iodine / Q000737:chemistry / Q000528:radiation effects; D007854:Lead / Q000737:chemistry / Q000528:radiation effects; D008027:Light; D008163:Luminescent Measurements / Q000379:methods; D008744:Methylamines / Q000737:chemistry / Q000528:radiation effects; D018613:Microscopy, Confocal / Q000379:methods; D010087:Oxides / Q000737:chemistry / Q000528:radiation effects*; D018629:Spectrometry, Mass, Secondary Ion / Q000379:methods; D014025:Titanium / Q000737:chemistry / Q000528:radiation effects*
chemical_list: D017610:Calcium Compounds; D007454:Iodides; D008744:Methylamines; D010087:Oxides; C059910:perovskite; D007854:Lead; D007455:Iodine; C027451:methylamine; D014025:Titanium