Optimizing the output performance and parasitic depletion of Bi2Te3-based thermoelectric generators by using a high-density approach

Abstract

Bi₂Te₃-based materials can be assembled into promising thermoelectric generators (TEGs) used for room temperature applications, yet their regulation for a wide range of applications, like the Internet of Things (IoTs), is limited by the small open circuit voltage, poor output power and large energy loss resulting from parasitic depletion to some extent. In this work, we have fabricated high-density thermoelectric generators (HD-TEGs) to compensate for these shortages, and the boosted voltage could reduce the energy loss simultaneously. To integrate HD-TEGs, the fabrication processes manipulate electrode deposition and reflow soldering techniques of delivering micro- and bulk-TEGs. Subsequently, a normalized power density of ∼13.7 μW cm⁻² K⁻², along with an open circuit voltage of ∼1.9 V, calculated contact depletion of ∼36% and experimental circuit depletion of ∼5% at ΔT of 13 K, has been achieved in a HD-TEG with 338 thermocouples (Tcs). Upon increasing ΔT to 73 K, the open circuit voltage and maximum output power are ∼10.1 V and 843.2 mW, which exceed those of the 50-Tcs TEG with packing fraction (f) of 5% and 34%, as well as the 200-Tcs TEG (f = 20%). These conversion properties are even much better than those of most commercial TEGs. Further, the finite-element simulation data indicate that output power and open circuit voltage could be further optimized to ∼68.5 mW (25.4 μW cm⁻² K⁻²) and ∼2.9 V at ΔT of 13 K, by further increasing the density of thermoelectric elements and reducing contact loss. Moreover, our study elucidates that fabricating TEGs by using a high-density approach, i.e., optimizing packing fraction by increasing the quantity of thermocouples, could be an effective avenue for achieving high output performance with superior critical voltage and small energy loss.