Manipulation of phase structure and Se vacancy to enhance the average thermoelectric performance of AgBiSe2

The high-temperature cubic phase of AgBiSe2 has been revealed to enable promising thermoelectric performance because of the high symmetry. In this work, it is shown that the cubic phase could be stabilized at room temperature by alloying SnSe. Although the effective mass increased, the decreased carrier concentration and mobility as well as the aggravated bipolar effect deteriorated the thermoelectric properties of the pure cubic phase. In contrast, the room-temperature rhombohedral AgBiSe2 obtained a peak zT value of similar to 0.66 at 723 K, which is attributed to the decreased thermal conductivity and increased power factor. Furthermore, reducing Se content not only increased the carrier concentration, but also increased the mobility due to the reduced energy barrier, and hence substantially improved the power factor over the whole temperature range. As a result, the peak zT and average zT were further enhanced in Ag0.94Bi0.94Sn0.06Se1.92. This work provides a novel strategy to optimize the thermoelectric performance of AgBiSe2 material.

Automated summary

The high-temperature cubic phase of AgBiSe2 has shown promising thermoelectric performance. This study reveals that alloying SnSe can stabilize the cubic phase at room temperature. However, the pure cubic phase suffers from decreased carrier concentration, mobility, and aggravated bipolar effect, leading to deteriorated thermoelectric properties. In contrast, the room-temperature rhombohedral AgBiSe2 exhibits improved thermoelectric properties due to decreased thermal conductivity and increased power factor. Reducing Se content further enhances the power factor in Ag0.94Bi0.94Sn0.06Se1.92. This work provides a novel strategy for optimizing thermoelectric performance of AgBiSe2 material.