Cooperative Nature of Ferroelectricity in Two-Dimensional Hybrid Organic-Inorganic Perovskites.
basic_science · Level V
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- Record sourced from PubMed, PMID 33754732.
- Also identified by DOI 10.1021/acs.nanolett.1c00395.
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Abstract
Two-dimensional (2D) ferroelectric (FE) hybrid organic-inorganic perovskites (HOIPs) are promising for potential applications as miniaturized flexible ferroelectric/piezoelectric devices. Recently, several 2D HOIPs [e.g., Ruddlensden-Popper type HOIP BA<sub>2</sub>PbCl<sub>4</sub> (BA = C<sub>6</sub>H<sub>5</sub>CH<sub>2</sub>NH<sub>3</sub><sup>+</sup>)] were reported to possess room-temperature ferroelectricity. However, the underlying microscopic mechanisms for ferroelectricity in 2D HOIPs remain elusive. Here, by performing first-principles calculations and symmetry mode analysis, we demonstrate that there exists a cooperative coupling between A-site organic molecules and B-site inorganic Pb<sup>2+</sup> ions that is essential to the ferroelectricity in 2D BA<sub>2</sub>PbCl<sub>4</sub>. The nonpolar ground state of the closely related compounds BA<sub>2</sub>PbBr<sub>4</sub> and BA<sub>2</sub>PbI<sub>4</sub> can also be explained in terms of the weakened cooperative coupling. We further predict that 2D BA<sub>2</sub>PbF<sub>4</sub> displays in-plane ferroelectricity with a higher Curie temperature and larger electric polarization. Our work not only reveals the unusual FE mechanism in 2D HOIPs but also provides a solid theoretical basis for the rational design of 2D multifunctional materials.