Reentrant Structural and Optical Properties and Large Positive Thermal Expansion in Perovskite Formamidinium Lead Iodide

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• 作者：Douglas H. Fabini ; Dr. Constantinos C. Stoumpos ; Dr. Geneva Laurita ; Dr. Andreas Kaltzoglou ; Dr. Athanassios G. Kontos ; Dr. Polycarpos Falaras ; Prof. Dr. Mercouri G. Kanatzidis and Prof. Dr. Ram Seshadri
• 刊名：Angewandte Chemie International Edition
• 出版年：2016
• 出版时间：December 5, 2016
• 年：2016
• 卷：55
• 期：49
• 页码：15392-15396
• 全文大小：1106K
• ISSN：1521-3773

文摘

The structure of the hybrid perovskite HC(NH₂)₂PbI₃ (formamidinium lead iodide) reflects competing interactions associated with molecular motion, hydrogen bonding tendencies, thermally activated soft octahedral rotations, and the propensity for the Pb²⁺ lone pair to express its stereochemistry. High-resolution synchrotron X-ray powder diffraction reveals a continuous transition from the cubic α-phase (Pmh-equation-construct">h-equation-image">hml="true" class="math-equation-mathml" style="display:none">h xmlns:mml="http://www.w3.org/1998/Math/MathML">http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML" accent="true">3‾h> 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.