Heterojunction solar cells are a notable improvement in solar cell technology, distinguished by the interface created by two distinct semiconductor materials. However, high manufacturing costs and complexity in the production process have limited the use of traditional HJTs. Given the current trend in solar cells toward using thinner absorber layers, it is evident that 2D materials with atomically thin structures and high flexibility are the most suitable options for integrating with next-gen solar cell technology. Phosphorene, a recently emerged 2D material that has exceptional carrier mobility (approximate to 4000 cm(2) V-1 s(-1)), tunable bandgap (approximate to 0.3 to 2 eV) and better mechanical flexibility has gained immense attention in various fields. On the other hand, MoS2 a member of transition metal dichalcogenides possess tunable bandgap (approximate to 1.2-2 eV), high carrier mobility (approximate to 200 cm(2 )V(-1) s(-1)) and huge surface area making them highly suitable for a wide variety of applications. In this work, SCAPS-1D simulation using 2D/2D material heterojunction solar cell is carried out for ITO/phosphorene/MoS2/Al device. The simulation focused on modifying bandgap and defect density (N-t) of 2D semiconductors. Furthermore, impact of input light intensity on device performance are studied.