Electron delocalization enhances the thermoelectric performance of misfit layer compound (Sn1-xBixS)1.2(TiS2)2 |
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Affiliation: | 1.Key Laboratory of Radiation Physics and Technology, Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064, China;2.Institute of New Energy and Low-Carbon Technology, Sichuan University, Chengdu 610065, China |
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Abstract: | The misfit layer compound (SnS)1.2(TiS2)2 is a promising low-cost thermoelectric material because of its low thermal conductivity derived from the superlattice-like structure. However, the strong covalent bonds within each constituent layer highly localize the electrons thereby it is highly challenging to optimize the power factor by doping or alloying. Here, we show that Bi doping at the Sn site markedly breaks the covalent bonds networks and highly delocalizes the electrons. This results in a high charge carrier concentration and enhanced power factor throughout the whole temperature range. It is highly remarkable that Bi doping also significantly reduces the thermal conductivity by suppressing the heat conduction carried by phonons, indicating that it independently modulates phonon and charge transport properties. These effects collectively give rise to a maximum ZT of 0.3 at 720 K. In addition, we apply the single Kane band model and the Debye-Callaway model to clarify the electron and phonon transport mechanisms in the misfit layer compound (SnS)1.2(TiS2)2. |
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Keywords: | misfit layer sulfide electron delocalization carrier mobility chemical bond |
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