A review of low-, medium-, and high-temperature thermoelectric materials for thermoelectric generators.

Thermoelectric generators convert heat directly into electricity and require different material and engineering strategies across operating temperatures. This review organizes thermoelectric materials and representative generators into low-, medium-, and high-temperature regimes and evaluates their performance using material-, device-, module-, and system-level evidence. Low-temperature systems are dominated by limited temperature differences, heat-source coupling, contact resistance, and mechanical compliance. Medium-temperature technologies depend on high average zT, p-n compatibility, diffusion barriers, and segmented architectures. High-temperature systems increasingly require oxidation resistance, suppression of elemental volatilization, stable low-resistance interfaces, thermomechanical compatibility, reliable joining and packaging, and scalable manufacturing. Half-Heusler alloys, skutterudites, SiGe, Cu2X compounds, Zintl-related materials, and thermoelectric oxides are compared in this framework. Progress toward practical deployment will depend on translating material performance into durable modules validated under realistic thermal, mechanical, and environmental conditions.