As poor stability is the primary constraint for the commercialization of perovskite solar cells, improving stability has been the primary focus of recent research works regarding solar cells that make use of perovskite materials. Different metal oxide transport layers are being used with the aim of fabricating stable perovskite solar cells. A stable and efficient solar cell with both metal oxide transport layers (ZnO and NiOX) and a perovskite (methyl ammonium lead iodide) absorber layer is simulated in this work, and a comparison of performance parameters is made with other transport layers from the literature. The issue of optimization regarding the thickness of the absorber layer and the doping concentration in the absorber and transport layers has been addressed, and the effect of defect concentration at the interface has been investigated. Optimum performance is achieved with an absorber layer of thickness 800 nm. Linear grading is also introduced in the absorber layer by varying the concentration of different halides, which increases the efficiency by approximately 8% owing to the increase in the short circuit current density.