In the present work, different hybrid perovskites were synthesized by gradual concentration variation of larger cation of phenylammoniumiodide (PAI) and methylammoniumiodide (MAI) in PbI2 solution with the aim of improving the stability of MAPbI(3) film and photovoltaic efficiency. To understand the properties of perovskite like structural, optical, thermal, morphological and chemical state, extensive characterizations such as XRD, UV visible spectroscopy, FE-SEM, SEM, EDX and XPS were performed. The role of PAI was investigated further with the use of DFT studies. The DFT results confirmed that the PAI was passivated on the surface of MAPbI3 with most stable arrangement. The stable arrangement revealed the formation of pi-pi interactions within the phenyl rings, which shielded the MAI crystals and thereby resulted in enhanced stability of the perovskites. Highly protected perovskite consequently yielded high- performance solar cell device with enhanced stability under 60% humidity, high temperature exposure and longer time stability even when directly exposed to normal room temperature. The new investigation of capping techniques with the use of bigger organic molecules, high performance solar cell with low device costs could emerge. This could lead to unprecedented rapid progress on power conversion efficiency (PCE). Thus, more stable organic-inorganic hybrid perovskites could be developed for future applications.