An efficacious Intermediate Layer (IML) is important for multi junction solar Photo Voltaic Cell (PVC) owing to its good electrical conductivity and optical transparency. In this research work, the use of Graphene as an IML with varied thickness on InGaP/GaAs/InGaAs multi-junction solar PVCs is investigated using virtual fabrication TCAD tool SILVACO-Atlas. The detail absorption rate from wavelength 300 nm (ultraviolet)-2500 nm (middle infra-red region) is determined and the effected modelling stages are recounted. The results after simulation are further confirmed with experimental data to prove accuracy of the research work proposed. The performance parameters with = 33.4 mA/cm², = 1.27 V, fill factor (FF) = 99.5% and conversion efficiency of 30.91% (1 sun) are obtained under AM1.5G illumination.