Pressure-induced insulator-to-metal transitions for enhancing thermoelectric power factor in bismuth telluride-based alloys.

First-principles calculations revealing insulator-to-metal transitions in Bi2Te3 and Bi2Te2Se, at 9 GPa and 12.5 GPa, respectively, match with prior experiments. Our electronic band structure calculations and accompanying Boltzmann transport calculations of thermoelectric properties for Bi2-xSbxTe2-ySey alloys explain and predict large power factor changes induced by pressure. Complex band degeneracy changes preceding insulator-to-metal transitions significantly alter the density of states near the Fermi level, and foster the disentangling of the unfavorable coupling between Seebeck coefficient and electrical conductivity. Our findings on pressure-induced changes in thermoelectric power factor provide insights for designing V2VI3-based high-performance thermoelectric materials through strategies such as alloying, high-pressure processing, and strain engineering.