6:00 PM - 6:15 PM
[14p-B12-18] Control of thermal transport properties in organic-inorganic hybrid structures
Keywords:thermal properties, phonon transport, organic-inorganic hybrid structures
Organic-inorganic hybrid structures have recently attracted attention for possible thermoelectric applications. In such structures, embedded molecules provide selective and various degrees of freedom for thermal properties, which enables us to deal with thermal related issues of devices for their use. Here, we focus on hybrid organic−inorganic halides of the formula ABX3 (A = organic molecular cation; B = Ge, Sn, Pb; X = halide), particularly CH3NH3PbI3 (hereafter MAPI). Recent research showed that the thermal conductivity of MAPI is suppressed quite efficiently even below room temperature, but the specific mechanism remains unclear.
In this research, we investigate the thermal properties of MAPI and elucidate the suppression mechanism, which promises to bring guidelines for the design of hybrid thermoelectric materials. For the precise analysis, we developed the empirical potential for MAPI by fitting to the force trajectory of the ab-initio molecular dynamics calculations. In this procedure, typical interatomic potential functions are adopted and expanded to higher order to reproduce the anharmonic potential surface of MAPI.
With the developed potential, we evaluated the thermal conductivity by the nonequilibrium molecular dynamics method. Results were compared with model systems that include different embedded cations, showing that the rotational motions of embedded molecules notably suppress the thermal conductivity of MAPI. We also checked their vibrational density of states with different temperatures and defined the energy range where phonons are coupled via anharmonicity. Finally we performed phonon dispersion analysis and concluded the suppression mechanism; namely, the rotations are coupled with the translations of cations, via which phonons are coupled and scatter each other.
In this research, we investigate the thermal properties of MAPI and elucidate the suppression mechanism, which promises to bring guidelines for the design of hybrid thermoelectric materials. For the precise analysis, we developed the empirical potential for MAPI by fitting to the force trajectory of the ab-initio molecular dynamics calculations. In this procedure, typical interatomic potential functions are adopted and expanded to higher order to reproduce the anharmonic potential surface of MAPI.
With the developed potential, we evaluated the thermal conductivity by the nonequilibrium molecular dynamics method. Results were compared with model systems that include different embedded cations, showing that the rotational motions of embedded molecules notably suppress the thermal conductivity of MAPI. We also checked their vibrational density of states with different temperatures and defined the energy range where phonons are coupled via anharmonicity. Finally we performed phonon dispersion analysis and concluded the suppression mechanism; namely, the rotations are coupled with the translations of cations, via which phonons are coupled and scatter each other.