Development of the high performance thermoelectric unicouple based on Bi₂Te₃ compounds

Bismuth telluride-based compounds are the most common thermoelectric (TE) materials for power generating systems, which can operate in the temperature range of 300–600 K. One of the main disadvantages of Bi₂Te₃-based TE modules is the low energy conversion efficiency (3–6%). For this reason, we offer a unique thermoelectric power generation unicouple based on the developed n-type Bi₂Te_2.7Se_0.3 and cut perpendicularly to the main crystallographic axis p-type Bi_0.5Sb_1.5Te₃ thermoelectric materials. The application of the optimized chemical compositions in combination with Spark Plasma Sintering (SPS) technique provided the high average thermoelectric figure of merit of up to 0.97 and 0.72 for n-Bi₂Te_2.7Se_0.3 and p_ꓕ-Bi_0.5Sb_1.5Te₃, respectively. A three-dimensional finite-element simulation was employed to account for the different transport properties of the n- and p-type materials. As a result of the optimized design, the outstanding energy conversion efficiency η_max ∼8% was experimentally measured for the thermoelectric unicouple device at the relatively small temperature gradient of 250 K (T_c = 350 K). The output unicouple parameters were recorded using the developed herein high-precision original setup. Furthermore, a power generation TE unicouple with an electric power of 0.04 W at the 0.5 V was designed and fabricated offering significant industrial potential.