title: Effect of Structural Phase Transition on Charge-Carrier Lifetimes and Defects in CH3NH3SnI3 Perovskite.
abstract: Methylammonium tin triiodide (MASnI3) has been successfully employed in lead-free perovskite solar cells, but overall power-conversion efficiencies are still significantly lower than for lead-based perovskites. Here we present photoluminescence (PL) spectra and time-resolved PL from 8 to 295 K and find a marked improvement in carrier lifetime and a substantial reduction in PL line width below ∼110 K, indicating that the cause of the hindered performance is activated at the orthorhombic to tetragonal phase transition. Our measurements therefore suggest that targeted structural change may be capable of tailoring the relative energy level alignment of defects (e.g., tin vacancies) to reduce the background dopant density and improve charge extraction. In addition, we observe for the first time an above-gap emission feature that may arise from higher-lying interband transitions, raising the prospect of excess energy harvesting.
authors.affiliation: Department of Physics, University of Oxford, Clarendon Laboratory , Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Elizabeth S
authors.initials: ES
authors.lastname: Parrott
authors.affiliation: Department of Physics, University of Oxford, Clarendon Laboratory , Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Milot
authors.affiliation: Department of Physics, University of Oxford, Clarendon Laboratory , Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Thomas
authors.initials: T
authors.lastname: Stergiopoulos
authors.affiliation: Department of Physics, University of Oxford, Clarendon Laboratory , Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Henry J
authors.initials: HJ
authors.lastname: Snaith
authors.affiliation: Department of Physics, University of Oxford, Clarendon Laboratory , Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Michael B
authors.initials: MB
authors.lastname: Johnston
authors.affiliation: Department of Physics, University of Oxford, Clarendon Laboratory , Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Herz