Room-temperature dynamic correlation between methylammonium molecules in lead-iodine based perovskites: An ab initio molecular dynamics perspective

The high efficiency of lead organo-metal-halide perovskite solar cells has raised many questions about the role of the methylammonium (MA) molecules in the Pb-I framework. Experiments indicate that the MA molecules are able to “freely” spin around at room temperature even though they carry an intrin...

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Bibliographic Details
Published in:Physical review. B 2016-12, Vol.94 (21), Article 214114
Main Authors: Lahnsteiner, Jonathan, Kresse, Georg, Kumar, Abhinav, Sarma, D. D., Franchini, Cesare, Bokdam, Menno
Format: Article
Language:English
Subjects:
Antiferroelectricity
Cages
Correlation analysis
Dipole moments
Iodine
Lead
Molecular dynamics
Perovskites
Photovoltaic cells
Room temperature
Solar cells
Temperature
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Summary:The high efficiency of lead organo-metal-halide perovskite solar cells has raised many questions about the role of the methylammonium (MA) molecules in the Pb-I framework. Experiments indicate that the MA molecules are able to “freely” spin around at room temperature even though they carry an intrinsic dipole moment. We have performed large supercell (2592 atoms) finite-temperature ab initio molecular dynamics calculations to study the correlation between the molecules in the framework. An underlying long-range antiferroelectric ordering of the molecular dipoles is observed. The dynamical correlation between neighboring molecules shows a maximum around room temperature in the mid-temperature phase. In this phase, the rotations are slow enough to (partially) couple to neighbors via the Pb-I cage. This results in a collective motion of neighboring molecules in which the cage acts as the mediator. At lower and higher temperatures, the motions are less correlated.
ISSN:2469-9950
2469-9969
DOI:10.1103/PhysRevB.94.214114