Synergetic enhancement of thermoelectric performance in a Bi_0.5Sb_1.5Te₃/SrTiO₃heterostructure

Thermoelectric devices enable a direct conversion between thermal energy and electrical energy. The maximum output power of thermoelectric devices is determined by, whereSis the Seebeck coefficient, ΔTis the temperature difference andR_intis the internal resistance, respectively. To achieve a high output power, a large Seebeck coefficient and a small internal resistance are required. However, the intrinsic tradeoff between the Seebeck coefficient and the electrical conductivity restrains the further improvement in single thermoelectric materials. Herein, we break this restriction by utilizing the synergetic effect in a Bi_0.5Sb_1.5Te₃/SrTiO₃heterostructure, where the reduced SrTiO₃substrate and the Bi_0.5Sb_1.5Te₃overlayer contribute to a large Seebeck coefficient and a small internal resistance, respectively. As a result, the output power of the Bi_0.5Sb_1.5Te₃/SrTiO_3−xheterostructure can reach up to 722 nW (ΔT= 60 K), which is approximately a 44 and 11 times enhancement compared with the individual Bi_0.5Sb_1.5Te₃thin film and SrTiO₃substrate, respectively. Our studies will not only provide a general guidance to design novel thermoelectric heterostructures with enhanced performance, but also help understand the modulation doping and energy filtering effects at the atomic level.