In this article, a combination of spherical and oval NiO nanoparticles were synthesized through the co-precipitation method and incorporated into a MAPbI₃-based perovskite layer ( MAPbI₃:NiO) to enhance hole extraction in carbon-based perovskite solar cells (CPSCs). Field-emission scanning electron microscopy (FESEM) images of the MAPbI₃ and MAPbI₃: NiO NPs composite layers confirmed the formation of needle-like grains. The incorporation of NiO NPs in the perovskite layer enhanced both the crystallinity and the grain size of the film. Moreover, the NiO composited films showed maximum absorbance in the visible region and significantly quenched emission peak in the photoluminescence (PL) emission spectrum. Because of the materials’ outstanding characteristics, the NiO composite perovskite device achieved power conversion efficiency (PCE) of 9.75%. In addition, the effect of adding a spacer layer in the same device architecture was also studied. The results showed an enhancement of the open-circuit voltage (V_oc) from 862 mV to 988 mV, making the device a champion with PCE of ~11%.