Room Temperature Phase Transition in Methylammonium Lead Iodide Perovskite Thin Films Induced by Hydrohalic Acid Additives

Chan Myae Myae Soe, Constantinos C. Stoumpos, Boris Harutyunyan, Eric F. Manley, Lin X. Chen, Michael J. Bedzyk, Tobin J Marks, Mercouri G Kanatzidis

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

Although reactive additives have been employed in perovskite solar cells to enhance film morphology and significantly increase device performance, little is known about the effect of these additives on perovskite structural and optical properties. Here we report a systematic study of how the properties of methylammonium lead iodide perovskite (CH3NH3PbI3) are influenced by hydrohalic acid additives (HX; X=I, Br, Cl) in the precursor solution. Detailed structural and optical spectroscopic analysis reveals that all three acids affect the optical properties and alter the unit cell lattice parameters. Depending on the identity and concentration of HX, optical bandgaps widen or compress: addition of HBr yields a wider bandgap, whereas HI compresses the gap at high concentrations; HCl, on the other hand, has no significant effect on the bandgap. These changes can be understood by correlating them with the types of defects present in polycrystalline perovskite thin films in combination with the structural strain induced in very small crystallites. The presence of extra halides from HX in the precursor solution enables filling of the lattice vacancies in the perovskite, thereby altering metal–halogen–metal bond connectivity and consequently cell volumes and optical bandgaps. Remarkably, a room temperature tetragonal→cubic phase transition is observed for CH3NH3PbI3 films treated with high HX concentrations. Further insights into this anomalous phase transformation are obtained from in situ variable-temperature X-ray diffraction in the 25–55 °C (298–328 K) range, revealing a monotonic fall in transition temperature with increasing precursor solution HX concentration.

Original languageEnglish
Pages (from-to)2656-2665
Number of pages10
JournalChemSusChem
Volume9
Issue number18
DOIs
Publication statusPublished - Sep 22 2016

Fingerprint

perovskite
iodide
Iodides
phase transition
Perovskite
Lead
Phase transitions
Thin films
Acids
acid
Optical band gaps
Energy gap
Optical properties
optical property
temperature
Temperature
Spectroscopic analysis
Crystallites
Crystal lattices
halide

Keywords

  • additives
  • perovskite
  • phase transition
  • thin films
  • x-ray diffraction

ASJC Scopus subject areas

  • Environmental Chemistry
  • Chemical Engineering(all)
  • Materials Science(all)
  • Energy(all)

Cite this

Room Temperature Phase Transition in Methylammonium Lead Iodide Perovskite Thin Films Induced by Hydrohalic Acid Additives. / Soe, Chan Myae Myae; Stoumpos, Constantinos C.; Harutyunyan, Boris; Manley, Eric F.; Chen, Lin X.; Bedzyk, Michael J.; Marks, Tobin J; Kanatzidis, Mercouri G.

In: ChemSusChem, Vol. 9, No. 18, 22.09.2016, p. 2656-2665.

Research output: Contribution to journalArticle

Soe, Chan Myae Myae ; Stoumpos, Constantinos C. ; Harutyunyan, Boris ; Manley, Eric F. ; Chen, Lin X. ; Bedzyk, Michael J. ; Marks, Tobin J ; Kanatzidis, Mercouri G. / Room Temperature Phase Transition in Methylammonium Lead Iodide Perovskite Thin Films Induced by Hydrohalic Acid Additives. In: ChemSusChem. 2016 ; Vol. 9, No. 18. pp. 2656-2665.
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