Exploring the cation dynamics in lead-bromide hybrid perovskites

Carlo Motta, Fadwa El-Mellouhi, Stefano Sanvito

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

Density functional theory including a many-body treatment of dispersive forces is used to describe the interplay between structure and electronic properties of two prototypical Br-based hybrid perovskites, namely, CH3NH3PbBr3 and HC(NH2)2PbBr3. We find that, like for some of their iodine-based counterparts, the molecules' orientation plays a crucial role in determining the shape of both the conduction and valence bands around the band edges. This is mostly evident in the case of CH3NH3PbBr3, which is a direct band-gap semiconductor when the CH3NH3 group is oriented along the (111) direction but turns indirect when the orientation is (100). We have constructed a simple dipole model, with parameters all evaluated from ab initio calculations, to describe the molecules' depolarization dynamics. We find that, once the molecules are initially orientated along a given high-symmetry direction, their room-temperature depolarization depends on the specific material investigated. In particular we find that the ratio between the polarization decay constant of CH3NH3PbBr3 and that of HC(NH2)2PbBr3 is about 2 at room temperature. With these results at hand we suggest a simple luminescence decay experiment to prove our findings and establish a correlation between optical activity and the molecules' dynamics in these materials.

Original languageEnglish
Article number235412
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume93
Issue number23
DOIs
Publication statusPublished - 8 Jun 2016

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perovskites
Cations
bromides
Lead
Positive ions
cations
Molecules
Depolarization
depolarization
molecules
Optical correlation
optical activity
decay
room temperature
Valence bands
Conduction bands
Iodine
Electronic properties
iodine
Density functional theory

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

Exploring the cation dynamics in lead-bromide hybrid perovskites. / Motta, Carlo; El-Mellouhi, Fadwa; Sanvito, Stefano.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 93, No. 23, 235412, 08.06.2016.

Research output: Contribution to journalArticle

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