Temperature-Dependent Evolution of Raman Spectra of Methylammonium Lead Halide Perovskites, CH₃NH₃PbX₃ (X = I, Br)

• Published in: Molecules (Basel, Switzerland) Vol. 24; no. 3; p. 626
• Main Authors: Nakada, Kousuke, Matsumoto, Yuki, Shimoi, Yukihiro, Yamada, Koji, Furukawa, Yukio
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 11-02-2019; MDPI
• Subjects: Ammonia; bandwidth; Cages; Energy conversion efficiency; Glass substrates; Hydrogen bonds; Lead compounds; Metal halides; methylammonium lead halide perovskites; motional narrowing; organic/inorganic hybrid perovskites; Perovskites; phase transition; Phase transitions; Raman spectra; Raman spectroscopy; Solar cells; Solar power; Spectrum analysis; Temperature; Temperature dependence; Vibration; Vibrations; motional narrowing; methylammonium lead halide perovskites; organic/inorganic hybrid perovskites; phase transition; Raman spectroscopy; bandwidth
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules24030626

We present a Raman study on the phase transitions of organic/inorganic hybrid perovskite materials, CH₃NH₃PbX₃ (X = I, Br), which are used as solar cells with high power conversion efficiency. The temperature dependence of the Raman bands of CH₃NH₃PbX₃ (X = I, Br) was measured in the temperature ranges of 290 to 100 K for CH₃NH₃PbBr₃ and 340 to 110 K for CH₃NH₃PbI₃. Broad ν₁ bands at ~326 cm
for MAPbBr₃ and at ~240 cm
for MAPbI₃ were assigned to the MA⁻PbX₃ cage vibrations. These bands exhibited anomalous temperature dependence, which was attributable to motional narrowing originating from fast changes between the orientational states of CH₃NH₃⁺ in the cage. Phase transitions were characterized by changes in the bandwidths and peak positions of the MA⁻cage vibration and some bands associated with the NH₃⁺ group.