title: Localized holes and delocalized electrons in photoexcited inorganic perovskites: Watching each atomic actor by picosecond X-ray absorption spectroscopy.
abstract: We report on an element-selective study of the fate of charge carriers in photoexcited inorganic CsPbBr3and CsPb(ClBr)3perovskite nanocrystals in toluene solutions using time-resolved X-ray absorption spectroscopy with 80 ps time resolution. Probing the Br K-edge, the Pb L3-edge, and the Cs L2-edge, we find that holes in the valence band are localized at Br atoms, forming small polarons, while electrons appear as delocalized in the conduction band. No signature of either electronic or structural changes is observed at the Cs L2-edge. The results at the Br and Pb edges suggest the existence of a weakly localized exciton, while the absence of signatures at the Cs edge indicates that the Cs+cation plays no role in the charge transport, at least beyond 80 ps. This first, time-resolved element-specific study of perovskites helps understand the rather modest charge carrier mobilities in these materials.
authors.affiliation: Laboratoire de Spectroscopie Ultrarapide, ISIC-FSB and Lausanne Centre for Ultrafast Science (LACUS), Ecole Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
authors.forename: Fabio G
authors.initials: FG
authors.lastname: Santomauro
authors.affiliation: Laboratoire de Spectroscopie Ultrarapide, ISIC-FSB and Lausanne Centre for Ultrafast Science (LACUS), Ecole Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
authors.forename: Jakob
authors.initials: J
authors.lastname: Grilj
authors.affiliation: Laboratoire de Spectroscopie Ultrarapide, ISIC-FSB and Lausanne Centre for Ultrafast Science (LACUS), Ecole Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
authors.forename: Lars
authors.initials: L
authors.lastname: Mewes
authors.forename: Georgian
authors.initials: G
authors.lastname: Nedelcu
authors.forename: Sergii
authors.initials: S
authors.lastname: Yakunin
authors.affiliation: Laboratoire de Spectroscopie Ultrarapide, ISIC-FSB and Lausanne Centre for Ultrafast Science (LACUS), Ecole Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Rossi
authors.affiliation: Laboratoire de Spectroscopie Ultrarapide, ISIC-FSB and Lausanne Centre for Ultrafast Science (LACUS), Ecole Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
authors.forename: Gloria
authors.initials: G
authors.lastname: Capano
authors.affiliation: Laboratoire de Spectroscopie Ultrarapide, ISIC-FSB and Lausanne Centre for Ultrafast Science (LACUS), Ecole Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
authors.forename: André
authors.initials: A
authors.lastname: Al Haddad
authors.affiliation: Laboratoire de Spectroscopie Ultrarapide, ISIC-FSB and Lausanne Centre for Ultrafast Science (LACUS), Ecole Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
authors.forename: James
authors.initials: J
authors.lastname: Budarz
authors.affiliation: Laboratoire de Spectroscopie Ultrarapide, ISIC-FSB and Lausanne Centre for Ultrafast Science (LACUS), Ecole Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
authors.forename: Dominik
authors.initials: D
authors.lastname: Kinschel
authors.affiliation: Paul Scherrer Institut , CH-5232 Villigen, Switzerland.
authors.forename: Dario S
authors.initials: DS
authors.lastname: Ferreira
authors.affiliation: Laboratoire de Spectroscopie Ultrarapide, ISIC-FSB and Lausanne Centre for Ultrafast Science (LACUS), Ecole Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Rossi
authors.affiliation: Laboratoire de Spectroscopie Ultrarapide, ISIC-FSB and Lausanne Centre for Ultrafast Science (LACUS), Ecole Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
authors.forename: Mario
authors.initials: M
authors.lastname: Gutierrez Tovar
authors.affiliation: Paul Scherrer Institut , CH-5232 Villigen, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Grolimund
authors.affiliation: Paul Scherrer Institut , CH-5232 Villigen, Switzerland.
authors.forename: Valerie
authors.initials: V
authors.lastname: Samson
authors.affiliation: Paul Scherrer Institut , CH-5232 Villigen, Switzerland.
authors.forename: Maarten
authors.initials: M
authors.lastname: Nachtegaal
authors.affiliation: Paul Scherrer Institut , CH-5232 Villigen, Switzerland.
authors.forename: Grigory
authors.initials: G
authors.lastname: Smolentsev
authors.forename: Maksym V
authors.initials: MV
authors.lastname: Kovalenko
authors.affiliation: Laboratoire de Spectroscopie Ultrarapide, ISIC-FSB and Lausanne Centre for Ultrafast Science (LACUS), Ecole Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
authors.forename: Majed
authors.initials: M
authors.lastname: Chergui