Static and Dynamic Disorder in Formamidinium Lead Bromide Single Crystals

We show that formamidinium-based crystals are distinct from methyl ammonium-based halide perovskite crystals because their inorganic sublattice exhibits intrinsic local static disorder that coexists with a well-defined average crystal structure. Our study combines terahertz-range Raman scattering with single-crystal X-ray diffraction and first-principles calculations to probe the evolution of inorganic sublattice dynamics with temperature in the range of 10-300 K. The temperature evolution of the Raman spectra shows that low-temperature, local static disorder strongly affects the crystal structural dynamics and phase transitions at higher temperatures.

Automated summary

We demonstrate that formamidinium-based crystals differ from methyl ammonium-based halide perovskite crystals due to the presence of intrinsic local static disorder in their inorganic sublattice, despite having a well-defined average crystal structure. Our study combines terahertz-range Raman scattering, single-crystal X-ray diffraction, and first-principles calculations to investigate the temperature-dependent dynamics of the inorganic sublattice in the range of 10-300 K. The temperature evolution of the Raman spectra reveals that low-temperature, local static disorder significantly influences the crystal structural dynamics and phase transitions at higher temperatures.