The authors demonstrate single-layer graphene/n-Si Schottky junction solar cells that achieve a power conversion efficiency (PCE) of 8.6% under AM1.5 illumination. This performance, achieved by doping the graphene with bis(trifluoromethanesulfonyl)amide (TFSA), exceeds the native device efficiency by a factor of 4.5 and the best previously reported PCE in similar devices by a factor of nearly 6. The enhancement is attributed to the doping-induced shift in the graphene chemical potential, which increases the carrier density and reduces the cell series resistance, as well as the increase in the built-in potential, which increases the open-circuit voltage. These improvements are confirmed through current-voltage, capacitance-voltage, and external quantum efficiency measurements. The environmental stability of the TFSA-doped graphene/n-Si solar cells is also noted due to the hydrophobic nature of TFSA. The study highlights the advantages of graphene-based solar cells over indium tin oxide (ITO) Si junctions, including tunable work function, inexpensive and convenient electrode formation, superior electrical and optical performance, and the potential for application on other semiconductors.The authors demonstrate single-layer graphene/n-Si Schottky junction solar cells that achieve a power conversion efficiency (PCE) of 8.6% under AM1.5 illumination. This performance, achieved by doping the graphene with bis(trifluoromethanesulfonyl)amide (TFSA), exceeds the native device efficiency by a factor of 4.5 and the best previously reported PCE in similar devices by a factor of nearly 6. The enhancement is attributed to the doping-induced shift in the graphene chemical potential, which increases the carrier density and reduces the cell series resistance, as well as the increase in the built-in potential, which increases the open-circuit voltage. These improvements are confirmed through current-voltage, capacitance-voltage, and external quantum efficiency measurements. The environmental stability of the TFSA-doped graphene/n-Si solar cells is also noted due to the hydrophobic nature of TFSA. The study highlights the advantages of graphene-based solar cells over indium tin oxide (ITO) Si junctions, including tunable work function, inexpensive and convenient electrode formation, superior electrical and optical performance, and the potential for application on other semiconductors.