Thermoelectric generators (TEGs) are a form of energy harvester and eco-friendly power generation system that directly transform thermal energy into electrical energy. The thermoelectric (TE) method of energy harvesting takes advantage of the Seebeck effect, which offers a simple solution for fulfilling the power-supply demand in almost every electronics system. A high-temperature condition is commonly essential in the working mechanism of the TE device, which unfortunately limits the potential implementation of the device. This paper presents an in-depth analysis of TEGs at low operating temperature. The review starts with an extensive description of their fundamental working principles, structure, physical properties, and the figure of merit (ZT). An overview of the associated key challenges in optimising ZT value according to the physical properties is discussed, including the state of the art of the advanced approaches in ZT optimisation. Finally, this manuscript summarises the research status of Bi2Te3-based semiconductors and other compound materials as potential materials for TE generators working at low operating temperatures. The improved TE materials suggest that TE power-generation technology is essential for sustainable power generation at near-room temperature to satisfy the requirement for reliable energy supplies in low-power electrical/electronics systems.
Keywords: energy harvester; low operating temperatures; thermoelectric generator; thermoelectric material.