This chapter explores the innovative use of waste-derived carbon nanomaterialsNanomaterials in solar cellsSolar cells, addressing both environmental and energyEnergy challenges. It discusses the potential of these materials to improve solar cell efficiency and reduce costs while utilizing waste sources like biomassBiomass, plastics, and industrial by-products. The synthesis methods for these nanomaterialsNanomaterials, including pyrolysis and hydrothermalHydrothermal carbonizationCarbonization, are examined. The chapter details how waste-derived carbon nanomaterials can enhance various solar cell components, such as electron and hole transport layers, in perovskite, organic, and dye-sensitized cells. Specific examples are presented, like grapheneGraphene quantum dotsGraphene quantum dots from coal and carbon nanotubes from plastic waste, along with their performance improvements. The chapter also addresses challenges in using these materials, including purity and scalability issues. Environmental and economic impacts are evaluated, highlighting the potential for waste reduction and creating a circular economy in the solar energy sector. Future trends, such as integration with quantum dots and applications in flexible solar cellsSolar cells, are explored. The chapter concludes by emphasizing the transformative potential of waste-derived carbon nanomaterialsNanomaterials in advancing sustainable solar technology, calling for continued research and development in this promising field.