Weak Host Interactions Induced Thermal Transport Properties of Metal Halide Perovskites Deviating from the Rattling...

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid-State Chemistry

Background:

• Low-frequency phonon branches in metal halide perovskites typically harden with increasing cation mass.
• This leads to anomalous thermal transport, with the underlying physical mechanism remaining unclear.
• The conventional rattling model fails to explain observed phenomena in A2SnI6 perovskites.

Purpose of the Study:

• To theoretically investigate the thermal transport properties of A2SnI6 perovskites (A = K, Rb, Cs).
• To elucidate the physical mechanism behind the anomalous thermal transport in these materials.
• To develop a new model that accurately describes perovskite thermal transport.

Main Methods:

• Theoretical comparison of thermal transport properties in A2SnI6 perovskites.
• Analysis of phonon branch behavior and cation-anion interactions.
• Development and application of a novel spring model.

Main Results:

• The low-frequency phonon branch in A2SnI6 perovskites is insensitive to cation mass.
• Phonon behavior is strongly correlated with A+ cation and I- anion interactions within octahedral structures.
• The rattling model's failure is attributed to weak interactions between octahedral structures.

Conclusions:

• A new spring model successfully explains the thermal transport behavior in A2SnI6 perovskites.
• This work provides new insights into the thermal transport mechanisms of metal halide perovskites.
• Findings guide the design of materials with extremely low thermal conductivity.