Review of Micro Thermoelectric Generator

Used for thermal energy harvesting, thermoelectric generator (TEG) can convert heat into electricity directly. Structurally, the main part of TEG is the thermopile, which consists of thermocouples connected in series electrically and in parallel thermally. Benefiting from massive progress achieved in a microelectromechanical systems technology, micro TEG (μ-TEG) with advantages of small volume and high output voltage has obtained attention in recent 20 years. The review gives a comprehensive survey of the development and current status of μ-TEG. First, the principle of operation is introduced and some key parameters used for characterizing the performance of μ-TEG are highlighted. Next, μ-TEGs are classified from the perspectives of structure, material, and fabrication technology. Then, almost all the relevant works are summarized for the convenience of comparison and reference. Summarized information includes the structure, material property, fabrication technology, output performance, and so on. This will provide readers with an overall evaluation of different studies and guide them in choosing the suitable μ-TEGs for their applications. In addition, the existing and potential applications of μ-TEG are shown, especially the applications in the Internet of things. Finally, we summarize the challenges encountered in improving the output power of μ-TEG and predicted that more researchers would focus their efforts on the flexible structure μ-TEG, and combination of μ-TEG and other energy harvestings. With the emergence of more low-power devices and the gradual improvement of ZT value of the thermoelectric material, μ-TEG is promising for applications in various fields.