The contribution of solar photovoltaics in electricity generation in 2020 reached up to 830,741 GWh and with concentrators 13,113 GWh. In 2022, solar photovoltaics captured nearly 60% (298.21 billion US$) share of global renewable energy investments. In India, nearly 2 Lakhs population have employment in the solar photovoltaic industry directly or indirectly. These reference data are enough to understand the importance of solar voltaic technology in modern-day life. In this chapter, we have outlined the history and development of solar cells with special attention to silicon heterojunction solar cells. We have mentioned the rise and some latest applications of graphene in silicon and other types of heterojunction solar cells. The electronic structure of pristine graphene severely restricts some of its electronic applications. Graphene Quantum Dots are fragmented nanostructures of graphene known for their excellent photoluminescent properties. The main objective of this chapter is to shed light on the synthesis techniques, properties, and applications of Graphene Quantum Dots in heterojunction solar cells.