The III-nitride material system offers substantial potential to develop high-efficiency solar cells. Currently InGaN based solar cells have been demonstrated on sapphire substrate. This substrate expense adds up significantly to the cost of solar cells realization and further issues like sapphire substrate removal are of concern. Alternatively, InGaN epitaxial layers have been successfully grown on silicon substrate. An InGaN based quantum well solar cell structure is grown simultaneously by MOCVD on both GaN/sapphire and GaN/silicon substrates. The fabricated solar cells have comparable photo-response. The Voc of InGaN solar cell on sapphire is higher while the FF of InGaN solar cell on silicon is higher.