Realizing high energy conversion efficiency in a novel segmented-Mg${}_3$(Sb, Bi)${}_2$/cubic-GeTe thermoelectric module for power generation

The performance of thermoelectric materials has been improved considerably in recent decades, making the concept of generating energy from waste heat via solid-state thermoelectric devices more realistic. The construction of multi-stage modular structures based on complex parameter optimization to maximize the efficiency of each material over its optimal operating temperature range has become an effective strategy for improving device performance. Here, multi-segmented n-type Mg${}_3$(Sb, Bi)${}_2$ with low-contact-resistance buffer layers is first fabricated, and phase-transition-suppressed cubic p-type GeTe with enhanced thermoelectric performance is subsequently designed to match the segmented n-type legs. A 3D finite-element analysis model is then used to optimize the module size, providing higher energy conversion efficiency with an optimal average figure of merit over the entire operating temperature range. As a result, the prepared segmented-Mg${}_3$(Sb, Bi)${}_2$/cubic-GeTe module exhibits a high conversion efficiency of (12.8 ± 0.8)% at a hot-side temperature of 773 K with a temperature difference of ≈480 K, which is also comparable to that of previously reported thermoelectric modules. This study increases the number of matching combinations among n-/p-type thermoelectric materials and further broadens the potential candidate material library for segmented thermoelectric devices. (© 2022 Wiley‐VCH GmbH)