The effective regulation of nanotwinning on the multichannel thermal transport in hybrid organic–inorganic halide perovskite

Perovskite shows promising perspective in photoelectric and thermoelectric applications due to its mediate bandgap and low TC stemming from its intrinsic structure, i.e., organic-inorganic framework. While nanostructuring can reduce the thermal conductivity (TC) significantly which is important for the improvement of the corresponding thermoelectric performance, it is detrimental to the electrical and mechanical properties of materials, e.g., conductivity and strength. Nanotwinning has been proved to be an effective strategy to decouple the electrical and thermal properties, and improve the mechanical properties, and therefore it is one of the best candidates for the design of highly efficient thermoelectrics. Moreover, the introduction of nanotwinning can break the host structure of perovskite and regulate the proportions of liquid-convectional and solid-vibrational heat transport in some degree. Therefore, nanotwinning can be seen as an important method to face the challenge in the applications of perovskite in the field of thermoelectric conversion efficiency and thermal stability. Here, the multichannel heat transport in single-crystalline and twinned hybrid organic–inorganic halide perovskite is quantitatively characterized and compared by performing molecular dynamics simulations. Our results demonstrate that the solid-vibrational heat transport plays a dominant role in the whole thermal transport process even under high temperature, however, the contribution of convective term which is usually ignored in the previous studies also reaches to 20–30% of that of solid virial term. Furthermore, we notice that the convectional TC shows an unconventional temperature-independent trend and the cross term expresses a surprising negative TC. As for the twinned perovskite, it is surprising to find that the position of twin boundary plays an important role in controlling TC, i.e., the TC shows a first downward and then upward trend when the twin boundary is located at I atoms (I-model), while decreases when the center of twin is at Pb atoms (Pb-model). Moreover, the completely opposite trends of the TC-contributed ratios between convective and virial term have been found in the I- and Pb-model, respectively. Further, we also notice the TC contributed by fluid convective term is enhanced comparing with single-crystalline case and the cross term shows a much more significant negative TC, which results in the unexpected phenomenon that the total TC is even lower than that contributed by virial term. Our investigations provide a fundament understanding of the thermal transport properties of perovskite and propose the key mechanisms to guide the thermal management.