Multifold enhancements in thermoelectric power factor in isovalent sulfur doped bismuth antimony telluride films

Abstract

We report a two- to four-fold higher thermoelectric power factor α2σ in sputter-deposited Bi0.5Sb1.5Te3 films exposed to 250 to 2800 ppm near surface sulfur doping by keV ion implantation. This remarkable behavior is underpinned by simultaneous increases in electrical conductivity σ of up to 70%, and Seebeck coefficient α up to 55% attributable to isovalent-dopant-induced changes in defect chemistry and band structure. The σ increase correlates with increased sulfur-induced electron density which overpowers implantation-induced decreases in charge carrier mobility. Our results indicate that incorporating controlled amount of isovalent impurities into pnictogen chalcogenides can be attractive for enhancing their thermoelectric properties for applications.