Abstract
High thermoelectric performance is generally achieved in solid-solution alloyed or heavily doped semiconductors. The consequent atomic disorder has a trade-off in the thermoelectric figure of merit, zT: lattice thermal conductivity decreases with increasing disorder, but charge carrier mobility also reduces simultaneously. Herein, we demonstrate a strategy to optimize disorder rooted in the thermodynamic phase diagram and achieve a maximum zT = 2.3 in Ag vacant Ag1−xSbTe2. The formation of AgSbTe2 in the Ag2Te–Sb2Te3 pseudo-binary phase-space causes the precipitation of Ag2Te impurities due to thermodynamic instabilities. We show that Ag vacancies partially remove the disorder from the cation sub-lattice along with the suppression of the secondary Ag2Te impurities. Consequently, the electrical conductivity and power factor increase, while the concomitant formation of nanoscale superstructures (2–6 nm) due to local cation ordering reduces the lattice thermal conductivity. We obtained a high output power density of ∼268 mW cm−2 for ΔT = 325 K in a double-leg thermoelectric device. Our demonstration provides a pathway to optimize intrinsic atomic disorder using vacancy formation and optimize thermoelectric performance.
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