Designing good compatibility factor in segmented Bi_0.5Sb_1.5Te₃ – GeTe thermoelectrics for high power conversion efficiency

Over the past decade, thermoelectrics have progressed in leaps and bounds led by advancements in their physical understanding and design. Figure of merit zT exceeding 2 have been consistently reported, especially in GeTe, one of the best medium-temperature thermoelectrics. However, its power conversion efficiency is limited due to its low performance at room temperature. In this work, we report the design and exploration of segmented thermoelectric legs by pairing GeTe with the best room temperature thermoelectric Bi_0.5Sb_1.5Te₃ to achieve extremely high power conversion efficiency of 13.6% between 280 K and 773 K. The high efficiency is achieved by looking beyond simply combining high zT regions to encompass the thermoelectric compatibility factors between dissimilar materials. Our work opens up an avenue for materials design beyond maximizing zT to achieve technologically significant energy harvesting performance in thermoelectrics.