Nanostructured materials, especially metal oxides and rare earths, have received great interest owing to their capability to increase photovoltaic performance. With their favorable electrical, optical, and chemical properties, the metal oxide nanoparticles (MONPs) have high light absorption capability, enhanced surface area, as well as better charge transport—making them specifically suitable for solar energy applications. Also, rare earth elements with their quantum effects, high surface activity, and stable electronic structures have shown potential in solar cell technology. In this chapter, recent advancements in the production and uses of rare earth elements and metal oxide nanostructures are examined, especially as they relate to solar energy harvesting. It emphasizes how such materials will lead to higher solar cell efficiency with increased light trapping, reduced loss of energy, and increased photon-to-electron conversion. The role of rare earth elements in future solar technologies, including perovskite and dye-sensitized solar cells, is also discussed. Based on the continuing research into synthesis routes, structural manipulation, and photovoltaic performance, the nanomaterials are likely to propel the manufacture of cost-effective and efficient solar technologies. In photovoltaic applications, novel metal oxide combinations with equal molar ratios are used with increase in solar efficiency because of their excellent electrical, physical, and chemical qualities and high light absorption capacity. Similarly nowadays rare earth elements are also examined to create nanomaterials for a range of uses with the same qualities of metal oxides. Rare earth elements were used to synthesis of nanomaterials with various applications particularly in solar cell applications. In this book chapter, the usage of metal oxides compounds and rare earth elements for the synthesis of nanoparticles are discussed especially in solar cell application.