Lead-free halide perovskites provide a promising solution for efficient thermoelectric materials due to their ultralow lattice thermal conductivity(κ_(L)).However,disadvantages such as the electrically resistive natu...Lead-free halide perovskites provide a promising solution for efficient thermoelectric materials due to their ultralow lattice thermal conductivity(κ_(L)).However,disadvantages such as the electrically resistive nature strongly affect their power factor.In this work,we introduced the Te-based halide perovskites thermoelectric material Cs_(2)TeI_(6),which is already known as a promising candidate for photovoltaic applications due to its moderate band gap.Our findings reveal that Cs_(2)TeI_(6)has an exceptionally ultralow κ_(L)at room temperature,reaching as low as 0.17 W·m^(-1)·K^(-1).We found that the four-phonon scattering processes play a dominant role in suppressing the thermal transport,leading to an approximate 50% reduction in its particle-like thermal conductivity κ_(p) at 300 K.The ultralow κ_(L)can be mainly attributed to the strong discrepancy in bonding strength,which induces large anharmonicity.The flat and dense phonon dispersions result in a strong phonon scattering rate,making it easy to generate wavelike phonon tunneling.After accounting for the wavelike thermal conductivity κ_(c),a nonstandard T^(-0.30)temperature dependence was observed.Benefiting from the ultralow κ_(L),n-type Cs_(2)TeI_(6)is predicted to achieve an extraordinary ZT of 2.26 at 700 K.This work highlights a pathway for searching high-performance and low-cost thermoelectrics based on lead-free halide perovskites.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12204482 and U2330104)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(Grant No.2020L0537)+2 种基金the Natural Science Foundation of Shanxi Province(Grant No.202403021221164)Higher Education Teaching Reform and Innovation Project of Shanxi Province(Grant No.J20220480)Graduate Curriculum Ideological and Political Education Project of Shanxi Normal University(Grant No.010520233013)。
文摘Lead-free halide perovskites provide a promising solution for efficient thermoelectric materials due to their ultralow lattice thermal conductivity(κ_(L)).However,disadvantages such as the electrically resistive nature strongly affect their power factor.In this work,we introduced the Te-based halide perovskites thermoelectric material Cs_(2)TeI_(6),which is already known as a promising candidate for photovoltaic applications due to its moderate band gap.Our findings reveal that Cs_(2)TeI_(6)has an exceptionally ultralow κ_(L)at room temperature,reaching as low as 0.17 W·m^(-1)·K^(-1).We found that the four-phonon scattering processes play a dominant role in suppressing the thermal transport,leading to an approximate 50% reduction in its particle-like thermal conductivity κ_(p) at 300 K.The ultralow κ_(L)can be mainly attributed to the strong discrepancy in bonding strength,which induces large anharmonicity.The flat and dense phonon dispersions result in a strong phonon scattering rate,making it easy to generate wavelike phonon tunneling.After accounting for the wavelike thermal conductivity κ_(c),a nonstandard T^(-0.30)temperature dependence was observed.Benefiting from the ultralow κ_(L),n-type Cs_(2)TeI_(6)is predicted to achieve an extraordinary ZT of 2.26 at 700 K.This work highlights a pathway for searching high-performance and low-cost thermoelectrics based on lead-free halide perovskites.
