Ultralow thermal conductivity in all-inorganic halide perovskites

Abstract

<p id="d4162273e348">Discovery of materials with low thermal conductivity in simple, fully dense, and single-crystalline solids has proven extremely challenging. This paper reports the discovery of ultralow thermal conductivity (∼0.4 W⋅m ⁻¹⋅K ⁻¹) in single-crystalline, all-inorganic halide perovskite nanowires, which is comparable to their amorphous limit value. We attribute ultralow thermal conductivity to a cluster rattling mechanism, based on strong phonon–phonon scattering via the coexistence of collective motions involving various atom groups. These results call attention to the vital thermal transport processes and thermal management strategies for applications with all-inorganic halide perovskites. Further, CsSnI ₃ shows a rare combination of ultralow thermal conductivity and high electrical conductivity, so it can be a promising material for unique applications as an electrically conductive thermal insulator. </p><p class="first" id="d4162273e360">Controlling the flow of thermal energy is crucial to numerous applications ranging from microelectronic devices to energy storage and energy conversion devices. Here, we report ultralow lattice thermal conductivities of solution-synthesized, single-crystalline all-inorganic halide perovskite nanowires composed of CsPbI ₃ (0.45 ± 0.05 W·m ⁻¹·K ⁻¹), CsPbBr ₃ (0.42 ± 0.04 W·m ⁻¹·K ⁻¹), and CsSnI ₃ (0.38 ± 0.04 W·m ⁻¹·K ⁻¹). We attribute this ultralow thermal conductivity to the cluster rattling mechanism, wherein strong optical–acoustic phonon scatterings are driven by a mixture of 0D/1D/2D collective motions. Remarkably, CsSnI ₃ possesses a rare combination of ultralow thermal conductivity, high electrical conductivity (282 S·cm ⁻¹), and high hole mobility (394 cm ²·V ⁻¹·s ⁻¹). The unique thermal transport properties in all-inorganic halide perovskites hold promise for diverse applications such as phononic and thermoelectric devices. Furthermore, the insights obtained from this work suggest an opportunity to discover low thermal conductivity materials among unexplored inorganic crystals beyond caged and layered structures. </p>