Manipulating conduction band degeneracy of $AgBiSe_2$-$CuBiSe_2$ Solid Solutions for Developing High Performance Green Thermoelectric Material

Abstract

Recently, thermoelectric (TE) energy conversion has attracted numerous attentions as a renewable energy source due to their ability to convert heat into useful electricity. However, a number of high-performance TE materials are based on tellurium (Te), which is one of the most scarce element in the earth’s crust. Therefore, it is imperative to replace conventional metal tellurides into other environmentally friendly materials for a wider market growth of TE materials. Therefore, one of the selenium-based compounds, silver bismuth diselenide ($AgBiSe_2$) has been considered an alternative to metal telluride-based TE materials due to its intrinsically low thermal conductivity. However, its low electrical conductivity results in poor TE efficiency and prohibits its wider application. In this work, we report an increased density-of-states effective mass while maintaining a band effective mass by alloying $CuBiSe_2$ into $AgBiSe_2$ system and increasing a valley degeneracy of conduction bands. Therefore, significant increase of the Seebeck coefficient while preserving high electron mobility resulted in 2-fold increase of the power factor and zT than that of the pristine $AgBiSe_2$ at 773 K.