Compositional Heterogeneity in CsyFA1-yPb(BrxI1-x)3 Perovskite Films and its Impact on Phase Behavior

Julien Barrier, Rachel Beal, Aryeh Gold-Parker, Julian Vigil, Eli Wolf, Louis Waquier, Nicholas Weadock, Zihan Zhang, Laura Schelhas, Ana Nogueira, Michael McGehee, Michael Toney

Research output: Contribution to journalArticlepeer-review

21 Scopus Citations

Abstract

Hybrid organic inorganic lead halide perovskite semiconductors of the form CsyFA1-yPb(BrxI1-x)3 are promising candidate materials for high-efficiency photovoltaics. Notably, cation and anion substitution can be used to tune the band gaps to optimize performance and improve stability. However, multi-component materials can be prone to compositional and structural inhomogeneity and the extent, length scale and impact of this heterogeneity on lead halide perovskite properties are not well understood. Here we use synchrotron X-ray diffraction to probe the evolution of crystal structure across the tetragonal-to-cubic phase transition for a series of CsyFA1-yPb(BrxI1-x)3 thin films with x = 0.05 to 0.3 and y = 0.17 to 0.40. We find that the transition occurs across a broad temperature range of approximately 40 degrees C, much larger than for pure compounds such as MAPbI3 and MAPbBr3. We hypothesize that this smearing of the phase transition is due to compositional inhomogeneities that give rise to a distribution of local transition temperatures and we estimate the composition varies by about 10% to 15% with likely greater heterogeneity for the halide anion than the cation. This approach of mapping the transition is a simple and effective method of assessing heterogeneity, enabling evaluation of its impact.
Original languageAmerican English
Pages (from-to)6394-6405
Number of pages12
JournalEnergy and Environmental Science
Volume14
Issue number12
DOIs
StatePublished - 2021

NREL Publication Number

  • NREL/JA-5900-81868

Keywords

  • crystal structure
  • energy gap
  • lead compounds
  • organic-inorganic materials
  • perovskite
  • x-ray diffraction

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