Electrical, thermal and elastic properties of methylammonium lead bromide single crystal

We report temperature-dependent dielectric permittivity, thermal conductivity and mechanical resonances of as-grown hybrid perovskite single crystal CH3NH3PbBr3. Structural phase transitions are analysed using new experimental techniques, where thermal conductivity by steady-state process and elastic modulai by ultra-resonance spectroscopy is carried out through [100] and [110] directions, respectively. Performing thermal conductivity measurement on small-sized samples usually pose a significant challenge due to its dimensional limit. Following the steady-state technique, we measured the thermal conductivity of around 1 W m−1 K−1 in the temperature range 100–300 K on 2 × 2 mm2 size crystal. This is found to be comparable with I+3 anion-based hybrid perovskites as reported by Pisoni et al 2014 J. Phys. Chem. Lett. 5 2488. Room temperature electrical resistivity and dielectric permittivity of order 109 and 102, respectively, shows sharp transitions while approaching 150 K, which strongly supports first-order structural transition. Thermally activated resistivity behaviour above 280 K follows 1/T dependence, yielding activation energy of 0.2 eV. Softening of elastic moduli on approaching the phase transition is analysed from resonant ultrasound spectroscopy measurement. Square of the resonance frequency is found to diverge below 236 K, which inhibits any further experimental determination of elastic moduli at low temperature.