Thermoelectric Generator: Materials and Applications in Wearable Health Monitoring Sensors and Internet of Things Devices

Wearable sensors and biomedical devices have attracted a great deal of attention among users. Despite technological advancements in this field, a mixture of both progress and setbacks has been witnessed. The limited battery life of these devices for long-term operation remains a major challenge. In this context, thermoelectric generators have emerged as potential candidates for harvesting energy from temperature gradients to power wearable sensors and devices. This review focuses on the working mechanism of a thermoelectric generator, as well as the current progress of a variety of promising and widely used inorganic and organic thermoelectric materials. Encouragingly, the highest ZT values of 2.27, 2.5, 2.8, 2.3, and 1.85 are obtained for bismuth telluride, lead telluride, tin selenide, copper selenide, and magnesium antimonide, respectively, at various temperature ranges. Meanwhile, organic materials such as poly (3,4-ethylenedioxythiophene) polystyrene sulfonate, polyaniline composite, and graphdiyne showed the highest ZT values of 0.75, 0.74, and 4.8, respectively, at near-room temperature. Furthermore, numerous novel thermoelectric generator-powered wearable health monitoring sensors and Internet of Things devices are also presented. Finally, the current challenges and perspectives on the future development of thermoelectric generator, in particular for efficient materials and self-powered devices, are also discussed.