As the global energy consumption escalates at an alarming rate, the development of clean and renewable energy conversion technologies has become more critical. Solar energy is considered the ideal alternative, since it is the most readily available and richest renewable source of energy. Over the past few years, graphene, a two-dimensional (2D) single atomic carbon sheet, has greatly contributed to many advances in solar energy conversion. However, the use of pure graphene alone is limited to the type of functions it can provide, not to mention the challenges that come with its processability. Therefore, the functionalization of graphene is essential for the development of solar specialized graphene-based materials. This is achieved by typically integrating graphene into a photoactive material (e.g., semiconductors, organics, and metals) or, less commonly, by the self-functionalization of graphene to render it photoactive. Overall, this chapter describes the versatility of functionalization to fabricate sophisticated graphene materials for solar energy conversion in three application categories – photovoltaic, photochemical, and photoelectrochemical.