The paper deals with the conception and feasibility of the device structure based on the optimized PIN-(In, Ga)N homojunction solar cells. A new and efficient model combining the most realistic ones considering the impacts of band gap narrowing, collection efficiency, Shockley-Read-Hall recombination, and interface polarization is proposed to examine the solar cells' performance numerically. The functioning processes of n-In_0.42Ga_0.58N/i-(In, Ga)N/p-In_0.42Ga_0.58N solar cells at room temperature were investigated by calculating their characteristics for the AM1.5D, AM1.5G, and AM0 American Society for Testing and Materials experimental data. Our results show that the indium content, thickness, and defect density of the intrinsic layer strongly influence the characteristics of the InGaN solar cells. As the In-mole fraction increases, V_oc, FF and efficiency diminish to reach an independent regime for high In-content. A higher-quality 2μm−In_0.43Ga_0.57N for 10¹⁴cm⁻³ defect concentration can exhibit as high an efficiency as ≅11.3%, dropping to ≅4.12% for 10¹⁶cm⁻³ one.