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We present an experimental investigation of methylammonium lead tribromide single crystals in the orthorhombic, tetragonal, and cubic phases based on inelastic and deep inelastic neutron scattering experiments. We show how the average hydrogen nuclear kinetic energy, mainly affected by zero-point vibrational energies, shows differences larger compared to the changes simply related to temperature effects when moving from one phase to another. In particular, the Gaussian contribution to the average nuclear kinetic energy is larger in the tetragonal phase compared to the cubic and orthorhombic ones. Moreover, we find that the vibrational densities of states of MAPbBr3 single crystals in the orthorhombic phase are compatible with previously reported results on powder samples, and that the only vibrational modes that show slightly different frequencies compared to MAPbI3 are those in the energy range between 100 and 300 cm−1, related to librational/rotational modes. As these shifts are of about 10 cm−1 and do not affect any higher-energy vibrational mode, we conclude that the zero-point energies and average nuclear kinetic energies in the two-hybrid organic/inorganic perovskites are expected to be approximately the same within a harmonic framework. [ABSTRACT FROM AUTHOR]

Recent studies of lead halide perovskites demonstrate outstanding optoelectronic properties for thin-film semiconductor device application. Perovskite photovoltaic and light-emitting diodes are on the way to the mass production and spread in commercial semiconductor devices. The lab-to-fab transition of perovskite devices requires adaptation of perovskite deposition methods to industrial semiconductor fabrication standards. In this work, we demonstrated the formation of highly luminescence perovskite films by single-source chemical vapor deposition (ssCVD). Several stoichiometry compositions were prepared from inorganic precursors of CsBr and PbBr2 by dry mechanochemical synthesis with following evaporation. The combination of mechanochemical synthesis and ssCVD is an attractive approach due to the ability to scale up to industrial level and the precise control over the evaporation rate with a single source. Among all compositions CsBr:PbBr2, we show that CsPb2Br5 maintains phase composition and photoluminescent properties for powder and film. This work provides a comparative study of evaporated film properties (PL, XRD, TEM) and modeling calculations of interphase optical transitions. [ABSTRACT FROM AUTHOR]