Structural Characterization and Room Temperature Low-Frequency Raman Scattering from MAPbI3 Halide Perovskite Films Rigidized by Cesium Incorporation

Vinayaka H. Damle, Laxman Gouda, Shay Tirosh, Yaakov R. Tischler

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

The structural instability of organometal halide perovskites (OHP) is one of the major issues concerning commercialization of perovskite solar cells. Probing this intrinsic instability is one of the major milestones and challenging tasks toward enhancing the lifespan of the material. Here we have incorporated Cs ions into methylammonium lead iodide (MAPbI3) films and studied the thin film structural and optical properties. Incorporation of Cs into MAPbI3 leads to formation of both α-CsPbI3 and ∂-CsPbI3 phases, black and yellow, respectively, as indicated by the evolution of the optical band edge and X-ray diffraction (XRD) spectrum. At a concentration of 20% Cs ions, we observe the existence of a stable α-CsPbI3 phase. Incorporating 59% or more Cs ions yields the yellow phase of CsPbI3, due to alloying of Cs with the MAPbI3 matrix. The structural transformations observed in absorption spectra and XRD are confirmed by low-frequency Raman spectroscopy. The thermally induced structural fluctuations in pure MAPbI3 films are damped upon Cs incorporation, thus bringing long-range stabilized order to the perovskite structure and enabling for the first time observation of low-frequency Raman scattering at room temperature for OHPs. In addition to this, Cs incorporation rigidizes the perovskite film and sharpens all low-frequency vibrational peaks. This rigidizing effect can explain the importance of incorporating and alloying heavy elements into OHPs to bring both chemical stability and photostability.

Original languageEnglish
Pages (from-to)6707-6713
Number of pages7
JournalACS Applied Energy Materials
Volume1
Issue number12
DOIs
StatePublished - 24 Dec 2018

Bibliographical note

Publisher Copyright:
© 2018 American Chemical Society.

Keywords

  • cesium incorporation
  • hybrid perovskite
  • low frequency Raman
  • perovskite stability
  • phonon damping

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