Elucidating the atomistic origin of anharmonicity in tetragonal CH3NH3PbI3 with Raman scattering

Peculiar anharmonicity of Ruddlesden Popper metal halides: temperature-dependent phonon dephasing

“…The distinction of metal-halide perovskites from classical semiconductors lies, however, in the softness of the lattice and rather large anharmonicity induced by substantially high multiphonon scattering probabilities. 1,13 In addition, the non-polar dynamic fluctuations from the independent motion of the organic cation 2,14 lead to a rapid escalation of the complexity of the microscopic picture of the carrier-lattice dynamics, where the polaronic nature of the material is described as an interplay Electron-phonon interactions govern several key characteristics of semiconductors, including the transport parameters, recombination rates and quantum dynamics. It is common to formulate such interactions under the harmonic approximation, especially in crystalline semiconductors, where the lattice displacement is considered to be negligible in the presence of the carrier.…”

Metal cation s lone-pairs increase octahedral tilting instabilities in halide perovskites

“…[3][4][5][6][7] From a fundamental standpoint, the fascinating optoelectronic properties of HPs are closely related to their highly anharmonic thermal motions that lead to local, polar fluctuations and thus, localization of charge carriers. [8][9][10][11]75 The perovskite crystal (with stoichiometry AMX 3 ) consists of a three-dimensional network of corner-sharing MX 6 octahedra, with A-site cations occupying the cuboctahedral voids. The high connectivity allows for various lower-symmetry phases, characterized by tilting of the octahedra, making HPs capable of accommodating a wide range of compositions.…”

“…[21][22][23][24][25][26][27][28][29][30][31] The tilting can also be dynamic, resulting in structural fluctuations. 8,9,14,[32][33][34][35][36] When t is too low, the corner-sharing octahedra prefer to rearrange into edge-sharing or face-sharing octahedra, 37 taking the system away from the perovskite structure. In addition to t, the octahedral factor m = r M /r X is another important geometric factor.…”

Electronic structure of Li+@C60 adsorbed on methyl-ammonium lead iodide perovskite CH3NH3PbI3 surfaces

“…In addition, the lattice dynamics play an important role in determining the structural and electronic properties of these halide perovskites, [54][55][56] and the tetragonal structure of MAPbI 3 perovskite at room temperature is strongly anharmonic. 57 After gaining an understanding on the correlation between the stability and the vdW interactions at interface, we now investigate the atomic charge distribution at the interface between the MAPbI 3 perovskite and Li + @C 60 (or Li@ C 60 ). We perform an atomic charge analysis using the geometrical optimized structure of the MAPbI 3 /Li + @C 60 (and MAPbI 3 /Li@ C 60 ) system.…”