Mathematical modelling can offer the physical intuitions about the charge transport process inside a solar cells and provide the various elements affecting their performance. In the present paper, (CH3NH3Pb(I1-xBrx)3 based various perovskite solar cells have been mathematically simulated deploying SCAPS simulator. Various Hole Transport layers (HTLs) based on thickness, total defect density and donor density of mixed halide perovskite have been compared using Cd1-xZnxS as an Electron Transport Layer (ETL). Amongst the proffered HTLs, P3HT [Poly(3-hexylthiophene)] executed better and exhibited the PCE of 28.28%. During the simulation, mixed halide perovskite layer with thickness of 700 nm has been found suitable for the effective solar cell design. These mathematically simulated outcomes indicate the optimum efficiency of the solar cell that may further be prompted to design the extremely high efficient solar cells.