3D potassium-ion preintercalated graphene (KIPIG), which was recently invented via the reaction of potassium and CO, shows unique properties including large accessible surface area and excellent electrical conductivity for electrodes. Herein, it was revealed that the perovskite solar cells (PSC) and dye-sensitized solar cells (DSSC) with KIPIG electrode exhibited high power conversion efficiencies of 7.81% and 9.12%, respectively. This work not only proves that 3D KIPIG is an efficient electrode material, but also provides a strategy to reduce the fabrication cost of solar cells.