Graphene, largely known because of its dynamic properties such as enhanced carrier mobility, has emerged as an important photovoltaic material for increased photo-energy conversion. The efficiency of a perovskite photovoltaic cell can be improved by replacing the “hole transport layer” (HTL) with a layer of graphene. This study demonstrates how growing graphene using the PECVD technique affects the device efficiency. An ITO/PCBM/CsPbI3/graphene model is simulated using the software SCAPS-1D, where CsPbI3 is used as absorber, PCBM as the ETL, and graphene as the HTL. A numerical relation between solar cell efficiency and the plasma parameters is established and the numerically calculated efficiency is compared with that of the simulated model. It is also found that, upon introducing an increment in electron density of graphene sheet, the efficiency of device reduces due to an inverse relation with the Debye length, while an increase in the electron temperature increases the devices efficiency, thereby showing that altering the different plasma parameters at an optimum thickness of the absorber layer and HTL, the device efficiency can be raised, which would better its performance and real-world applications.