title: Real-Space Imaging of the Atomic Structure of Organic-Inorganic Perovskite.
abstract: Organic-inorganic perovskite is a promising class of materials for photovoltaic applications and light emitting diodes. However, so far commercialization is still impeded by several drawbacks. Atomic-scale effects have been suggested to be possible causes, but an unequivocal experimental view at the atomic level is missing. Here, we present a low-temperature scanning tunneling microscopy study of single crystal methylammonium lead bromide CH3NH3PbBr3. Topographic images of the in situ cleaved perovskite surface reveal the real-space atomic structure. Compared to the bulk we observe modified arrangements of atoms and molecules on the surface. With the support of density functional theory we explain these by surface reconstruction and a substantial interplay of the orientation of the polar organic cations (CH3NH3)(+) with the position of the hosting anions. This leads to structurally and electronically distinct domains with ferroelectric and antiferroelectric character. We further demonstrate local probing of defects, which may also impact device performance.
authors.affiliation: Energy Materials and Surface Sciences Unit (EMSS), Okinawa Institute of Science and Technology Graduate University (OIST) , 1919-1 Tancha, Onna-son, Okinawa 904-0495, Japan.
authors.forename: Robin
authors.initials: R
authors.lastname: Ohmann
authors.affiliation: Energy Materials and Surface Sciences Unit (EMSS), Okinawa Institute of Science and Technology Graduate University (OIST) , 1919-1 Tancha, Onna-son, Okinawa 904-0495, Japan.
authors.forename: Luis K
authors.initials: LK
authors.lastname: Ono
authors.affiliation: School of Chemical Engineering and Department of Energy Science, Sungkyunkwan University (SKKU) , Suwon 440-746, Korea.
authors.forename: Hui-Seon
authors.initials: HS
authors.lastname: Kim
authors.affiliation: Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University , Suzhou 215123, P. R. China.
authors.forename: Haiping
authors.initials: H
authors.lastname: Lin
authors.affiliation: Energy Materials and Surface Sciences Unit (EMSS), Okinawa Institute of Science and Technology Graduate University (OIST) , 1919-1 Tancha, Onna-son, Okinawa 904-0495, Japan.
authors.forename: Michael V
authors.initials: MV
authors.lastname: Lee
authors.affiliation: Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University , Suzhou 215123, P. R. China.
authors.forename: Youyong
authors.initials: Y
authors.lastname: Li
authors.affiliation: School of Chemical Engineering and Department of Energy Science, Sungkyunkwan University (SKKU) , Suwon 440-746, Korea.
authors.forename: Nam-Gyu
authors.initials: NG
authors.lastname: Park
authors.affiliation: Energy Materials and Surface Sciences Unit (EMSS), Okinawa Institute of Science and Technology Graduate University (OIST) , 1919-1 Tancha, Onna-son, Okinawa 904-0495, Japan.
authors.forename: Yabing
authors.initials: Y
authors.lastname: Qi