The growing demand for energy and the increased emphasis on clean energy solutions have driven significant research into energy-harvesting technologies like thermoelectric generators (TEGs). TEGs are especially well-suited for waste heat recovery from electronic devices, building systems, and industrial operations because they transform temperature differences into electrical energy. They offer a sustainable solution for eliminating reliance and improving energy efficiency on traditional power sources. Current and recent advances in materials, devices, and applications in thermoelectric technology, for overall critical awareness of current developments in these areas. Key materials explored include bismuth telluride, skutterudites, and recent nanostructured composites—their thermoelectric performances and optimization techniques are surveyed. Improvement of figure of merit (ZT) to larger extent and raising the bar of ZT through new material designs as well as novel synthesis schemes constitutes a prime focus towards attaining optimum performance and efficacy. TEGs in electronic devices have been shown to have enormous potential in power generation for sensors, portable electronics, and wearables by capturing waste heat. The applications underscore their ability to be integrated into the fast-growing ecosystem of low-power electronic systems. Beyond device applications, TEGs are utilized in heating, ventilation and air conditioned (HVAC) systems, industrial machinery, and solar-thermal energy systems for the recovery of waste heat, again underlining their versatility. This study also synthesizes the latest developments in integrating thermoelectric technology into electronic materials and devices, addressing the demand for more sustainable and energy-efficient systems. By capturing and converting waste heat into usable electricity, TEGs contribute significantly to reducing energy consumption and advancing clean energy initiatives. It is anticipated that the use of TEGs will significantly accelerate the transition to energy sustainability, especially when it comes to electronics and other vital applications.