Size-Dependent Lattice Structure and Confinement Properties in CsPbI3 Perovskite Nanocrystals: Negative Surface Energy for Stabilization

Qian Zhao, Abhijit Hazarika, Laura T. Schelhas, Jun Liu, E. Ashley Gaulding, Guoran Li, Minghui Zhang, Michael F. Toney, Peter C. Sercel, Joseph M. Luther

Research output: Contribution to journalArticlepeer-review

205 Scopus Citations

Abstract

CsPbI3 nanocrystals with narrow size distributions were prepared to study the size-dependent properties. The nanocrystals adopt the perovskite (over the nonperovskite orthorhombic) structure with improved stability over thin-film materials. Among the perovskite phases (cubic α, tetragonal β, and orthorhombic γ), the samples are characterized by the γphase, rather than α, but may have a size-dependent average tilting between adjacent octahedra. Size-dependent lattice constants systematically vary 3% across the size range, with unit cell volume increasing linearly with the inverse of size to 2.1% for the smallest size. We estimate the surface energy to be from -3.0 to -5.1 eV nm-2 for ligated CsPbI3 nanocrystals. Moreover, the size-dependent bandgap is best described using a nonparabolic intermediate confinement model. We experimentally determine the bulk bandgap, effective mass, and exciton binding energy, concluding with variations from the bulk α-phase values. This provides a robust route to understanding γ-phase properties of CsPbI3.

Original languageAmerican English
Pages (from-to)238-247
Number of pages10
JournalACS Energy Letters
Volume5
Issue number1
DOIs
StatePublished - 2020

Bibliographical note

Publisher Copyright:
© 2019 American Chemical Society.

NREL Publication Number

  • NREL/JA-5900-74571

Keywords

  • nanocrystals
  • perovskites
  • thin film materials

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