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Reentrant Structural and Optical Properties and Large Positive Thermal Expansion in Perovskite Formamidinium Lead Iodide
Author(s) -
Fabini Douglas H.,
Stoumpos Constantinos C.,
Laurita Geneva,
Kaltzoglou Andreas,
Kontos Athanassios G.,
Falaras Polycarpos,
Kanatzidis Mercouri G.,
Seshadri Ram
Publication year - 2016
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201609538
Subject(s) - formamidinium , perovskite (structure) , tetragonal crystal system , crystallography , iodide , thermal expansion , photoluminescence , phase transition , phase (matter) , negative thermal expansion , synchrotron , materials science , chemistry , condensed matter physics , crystal structure , optics , inorganic chemistry , organic chemistry , physics , composite material , optoelectronics
The structure of the hybrid perovskite HC(NH 2 ) 2 PbI 3 (formamidinium lead iodide) reflects competing interactions associated with molecular motion, hydrogen bonding tendencies, thermally activated soft octahedral rotations, and the propensity for the Pb 2+ lone pair to express its stereochemistry. High‐resolution synchrotron X‐ray powder diffraction reveals a continuous transition from the cubic α‐phase (Pm 3 ‾ m, #221) to a tetragonal β‐phase (P4/mbm, #127) at around 285 K, followed by a first‐order transition to a tetragonal γ‐phase (retaining P4/mbm, #127) at 140 K. An unusual reentrant pseudosymmetry in the β‐to‐γ phase transition is seen that is also reflected in the photoluminescence. Around room temperature, the coefficient of volumetric thermal expansion is among the largest for any extended crystalline solid.