Exploration of metastable phases holds profound implications for functional materials.Herein,we engineer the metastable phase to enhance the thermo-electric performance of germanium selenide(GeSe)through tailoring the...Exploration of metastable phases holds profound implications for functional materials.Herein,we engineer the metastable phase to enhance the thermo-electric performance of germanium selenide(GeSe)through tailoring the chemical bonding mechanism.Initially,AgInTe2 alloying fosters a transition from stable orthorhombic to metastable rhombohedral phase in GeSe by substantially promoting p-state electron bonding to form metavalent bonding(MVB).Besides,extra Pb is employed to prevent a transition into a stable hexagonal phase at elevated temperatures by moderately enhancing the degree of MVB.The stabilization of the metastable rhombohedral phase generates an optimized bandgap,sharpened valence band edge,and stimulative band convergence compared to stable phases.This leads to decent carrier concentra-tion,improved carrier mobility,and enhanced density-of-state effective mass,culminating in a superior power factor.Moreover,lattice thermal conductivity is suppressed by pronounced lattice anharmonicity,low sound velocity,and strong phonon scattering induced by multiple defects.Consequently,a maximum zT of 1.0 at 773 K is achieved in(Ge_(0.98)Pb_(0.02)Se)_(0.875)(AgInTe_(2))_(0.125),resulting in a maximum energy conversion efficiency of 4.90%under the temperature difference of 500 K.This work underscores the significance of regulating MVB to stabilize metastable phases in chalcogenides.展开更多
基金National Key R&D Program of China,Grant/Award Number:2021YFB1507403National Natural Science Foundation of China,Grant/Award Number:52071218+1 种基金China Postdoctoral Science Foundation,Grant/Award Number:2022M722170Shenzhen University 2035 Program for Excellent Research,Grant/Award Number:00000218。
文摘Exploration of metastable phases holds profound implications for functional materials.Herein,we engineer the metastable phase to enhance the thermo-electric performance of germanium selenide(GeSe)through tailoring the chemical bonding mechanism.Initially,AgInTe2 alloying fosters a transition from stable orthorhombic to metastable rhombohedral phase in GeSe by substantially promoting p-state electron bonding to form metavalent bonding(MVB).Besides,extra Pb is employed to prevent a transition into a stable hexagonal phase at elevated temperatures by moderately enhancing the degree of MVB.The stabilization of the metastable rhombohedral phase generates an optimized bandgap,sharpened valence band edge,and stimulative band convergence compared to stable phases.This leads to decent carrier concentra-tion,improved carrier mobility,and enhanced density-of-state effective mass,culminating in a superior power factor.Moreover,lattice thermal conductivity is suppressed by pronounced lattice anharmonicity,low sound velocity,and strong phonon scattering induced by multiple defects.Consequently,a maximum zT of 1.0 at 773 K is achieved in(Ge_(0.98)Pb_(0.02)Se)_(0.875)(AgInTe_(2))_(0.125),resulting in a maximum energy conversion efficiency of 4.90%under the temperature difference of 500 K.This work underscores the significance of regulating MVB to stabilize metastable phases in chalcogenides.
