Lead-based Perovskite materials and solar cells attracted attention in the last decade, however, lead toxicity hinders the way to commercialization; therefore, partial or total replacement of lead by environmentally friendly materials is suggested. In this work, wxAMPS software is employed to study the electrical parameters of MAPbI3, MAPbZnI3, and MAPbCoI3 as active layers. The thickness of the different active layers is optimized from 200 nm – 800 nm for the best electrical performance. For MAPbI3, the best photoconversion efficiency (PCE) of 24.54% is achieved at 550 nm thickness, while for MAPbZnI3 23.96% PCE is obtained at 500 nm. MAPbCoI3 achieves the highest PCE of 24.97% at 700 nm. With increasing the active layer thickness, PCE and short-circuit current increase; however, at the same time the fill factor and open-circuit voltage decrease. The quantum efficiency (QE) is simulated at different thicknesses for the three active layers. QE of the cells with different active layers increases with the thickness. The QE in the wavelengths range from 600-800 nm increases from 71% at 200 nm to more than 88% at thicknesses 550, 500, and 700 nm for MAPbI3, MAPbZnI3, and MAPbCoI3, respectively. The PCE is not only affected by the active layer thickness, but also by its defect density. The optimum defect density for the best PCE is obtained at 1x1014 cm-3. This simulation study confirms that MAPbZnI3, and MAPbCoI3, are promising new materials for high-efficiency perovskite solar cells.