FAxCs1-xPbI3 Nanocrystals: Tuning Crystal Symmetry by A-Site Cation Composition

Julian A. Vigil, Abhijit Hazarika, Joseph M. Luther, Michael F. Toney

Research output: Contribution to journalArticlepeer-review

34 Scopus Citations


Nanoscale semiconductors show remarkably tunable properties. For metal halide perovskite (MHP) nanocrystals (NCs), surface energy and lattice strain stabilize desirable MHP compositions and crystallographic phases that are unstable in the bulk. We report an X-ray scattering study of the average room-temperature crystal structure of ∼15 nm FAxCs1-xPbI3 (FA = formamidinium) NCs. All compositions crystallize in the perovskite structure; however, the average structure lowers in symmetry from the α (cubic) to β (tetragonal) to γ(orthorhombic) perovskite phases with decreasing x (Cs addition). The corresponding α-to β- A nd β-to γ-phase transitions occur between x = 0.75-0.5 and x = 0.25-0.1, respectively. Structural refinements also indicate large octahedral tilt angles (10-30°) in the β- A nd γ-phases and an increase in (pseudo)cubic unit cell volume upon FA addition. This work establishes the composition-structure relationship for FAxCs1-xPbI3 NCs and demonstrates the ability to target average crystal symmetry with facile synthetic control.

Original languageAmerican English
Pages (from-to)2475-2482
Number of pages8
JournalACS Energy Letters
Issue number8
StatePublished - 14 Aug 2020

Bibliographical note

Publisher Copyright:
© 2020 American Chemical Society.

NREL Publication Number

  • NREL/JA-5900-76552


  • composition-structure relations
  • halide perovskites
  • nanocrystals
  • quantum dots
  • x-ray diffraction


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