This review explores the transformative role of nanotechnology as the fundamental driver of the global transition toward sustainable energy. By leveraging the high surface-area-to-volume ratio and unique quantum properties of nanomaterials, researchers are overcoming the physical limitations of traditional green technologies. The paper examines three critical pillars: the use of nano-interfacial engineering to resolve the stability and degradation issues in high-efficiency Perovskite solar cells; the implementation of silicon nanowires and carbon nanotube (CNT) networks to mitigate the mechanical expansion and pulverization of high-capacity battery anodes; and the shift toward “Green Synthesis” (phytosynthesis and microbial synthesis) to ensure non-toxic, sustainable manufacturing.