The Effect of Cesium Incorporation on the Vibrational and Elastic Properties of Methylammonium Lead Chloride Perovskite Single Crystals.

Hybrid organic-inorganic lead halide perovskites (LHPs) have emerged as a highly significant class of materials due to their tunable and adaptable properties, which make them suitable for a wide range of applications. One of the strategies for tuning and optimizing LHP-based devices is the substitution of cations and/or anions in LHPs. The impact of Cs substitution at the A site on the structural, vibrational, and elastic properties of MACsPbCl-mixed single crystals was investigated using X-ray diffraction (XRD) and Raman and Brillouin light scattering techniques.

Influence of Halides on Elastic and Vibrational Properties of Mixed-Halide Perovskite Systems Studied by Brillouin and Raman Scattering.

The relationship between halogen content and the elastic/vibrational properties of MAPbBrCl mixed crystals ( = 1.5, 2, 2.5, and 3) with MA = CHNH has been studied using Brillouin and Raman spectroscopy at room temperature.

Structural Phase Transitions and Thermal Degradation Process of MAPbCl Single Crystals Studied by Raman and Brillouin Scattering.

Raman spectroscopy was applied to MAPbCl single crystals in a wide frequency range from 10 to 3500 cm over a broad temperature range from -196 °C to 200 °C including both two structural phase transitions and a thermal degradation range. Low-frequency lattice modes of MAPbCl were revealed for the first time, which showed discontinuous anomalies along with the change in the number of Raman modes at the transition points of -114 °C and -110 °C. Several Raman modes related to the C-N stretching and MA rocking modes in addition to the lattice modes displayed temperature dependences similar to those of MAPbBr in both Raman shifts and half widths, indicating that the MA cation arrangement and H-halide bond interactions behave similarly in both systems during the phase transition.

Acoustic Anomalies and the Critical Slowing-Down Behavior of MAPbCl Single Crystals Studied by Brillouin Light Scattering.

Inelastic light scattering spectra of organic-inorganic halide perovskite MAPbCl single crystals were investigated by using Brillouin spectroscopy. Sound velocities and acoustic absorption coefficients of longitudinal and transverse acoustic modes propagating along the cubic [100] direction were determined in a wide temperature range. The sound velocities exhibited softening upon cooling in the cubic phase, which was accompanied by the increasing acoustic damping.