Recent Advances in Chalcogenides for Mid-Temperature Thermoelectric Materials

Amidst escalating concerns over energy sustainability and environmental degradation, thermoelectric (TE) technologies have garnered renewed attention, particularly within the mid-temperature regime (400–800 K), which is relevant to industrial waste heat recovery. This review presents a focused and critical assessment of recent advancements in chalcogenide-based thermoelectric materials, diverging from broader surveys by emphasising compositional innovations, strategic doping methodologies, and synthesis-driven performance enhancements. Through comparative analysis of technically advanced systems, we delineate the structural, morphological, and transport property evolutions that underpin improved thermoelectric efficiency. Special attention is given to the mechanistic roles of defect engineering, carrier concentration modulation, and nanostructuring in optimising the dimensionless figure of merit (ZT). Furthermore, we articulate key design principles that differentiate emerging chalcogenides from conventional TE materials, offering insights into their scalability and integration potential. The review concludes by outlining prospective research trajectories aimed at accelerating the development of high-efficiency, environmentally benign thermoelectric devices, thereby positioning chalcogenide systems as pivotal contributors to next-generation sustainable energy solutions.