• Enhancement of thermoelectric performance of $n$-type AgBi$_{1+x}$Se$_2$ via improvement of the carrier mobility by modulation doping

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    • Keywords


      Thermoelectrics; modulation doping; mobility; power factor; thermal conductivity.

    • Abstract


      High charge carrier mobility with low lattice thermal conductivity is one of the key factors for the design of a good thermoelectric material. Recent studies show that $n$-type Te-free AgBiSe$_2$ is promising compound for thermoelectricenergy conversion due to intrinsically low lattice thermal conductivity. However, low charge carrier mobility in AgBiSe$_2$ is the constraint for enhancement of its power factor. In the present study, we use a chemical modification way to realizemodulation doping in AgBiSe$_2$. The addition of 2–6 mol% excess Bi in AgBiSe$_2$ results in the formation of Bi-rich modulation-doped microstructures of topological semimetal, Bi$_4$Se$_3$ in AgBiSe$_2$ matrix. We show that due to facile carrier transport via semi-metallic Bi4Se$_3$ microstructure results in overall improvement of carrier mobility without compromising Seebeck coefficient in AgBiSe$_2$ system, which in turn results in a remarkable improvement in the power factor ($\sigma S^2$) value. A highest $\sigma S^2$ value of $\sim$6.35 $\mu$W cm$^ {-1}$ K$^{-2}$ at 800 K has been achieved in AgBiSe$_2$-3% Bi excess sample, which is higher than previously reported metal ion and halogen-doped AgBiSe$_2$.

    • Author Affiliations



      1. New Chemistry Unit, School of Advanced Materials and International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064, India
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