Advancements in Ge-based thermoelectric materials for efficient waste heat energy conversion: a comprehensive review

Abstract

Thermoelectric materials hold significant promise for converting waste heat energy into electrical energy. The performance of these materials and devices is assessed using a quantitative measure known as the figure of merit, which relies on the Seebeck coefficient, thermal conductivity, and electrical conductivity of the material. Extensive efforts have been devoted to enhancing the efficiency of thermoelectric materials and devices through various techniques such as doping, nanostructuring, electron energy filtering, and band engineering. This paper presents a comprehensive review encompassing various thermoelectric materials, including organic, inorganic, intermetallic, complex cell structures, hybrid, and notably Germanium-based materials. Ge, due to its easy availability, low cost, high Seebeck coefficient, and high thermal stability, emerges as a suitable candidate for thermoelectric energy generation. Among the Ge-based materials studied, (Sb2Te3)0.5(Ge0.91Pb0.09Te)17.5 gave the highest figure of merit, with values of approximately 2.4 at 773 K. These findings underscore the significant potential of GeTe alloy in thermoelectric energy harvesting. This review provides an overview of the latest developments in thermoelectric materials, focusing on different strategies to enhance thermoelectric performance. Additionally, the suitability of various Ge-based thermoelectric materials for energy harvesting applications is extensively discussed in this review.