Impeding phonon transport through superlattices of organic-inorganic halide perovskites

Abstract

Superlattice structures present a strategy to impede lattice thermal transport through organic-inorganic halide perovskites and improve their potential for thermoelectric applications. We investigate the phonon characteristics of such novel configurations and compare against predictions of the simple perovskite lattices using first principle calculations. Our results show the existence of structural instabilities due to distortions in the octahedral cage surrounding the methylammonium ion. In the superlattices, a strong phonon incoherence reduces the group velocities while interfacial resistance enhances scattering and limits the phonons impeding heat conduction. Although heat transfer is anisotropic in these perovskites, the interfaces in the superlattice obstruct phonon transport along all directions.