In this study nanodisks made from aluminum are incorporated in a back-reflector scheme in order to enhance the maximum achievable current in one-micron thick crystalline silicon solar cells. We perform three-dimensional numerical investigations of the backward scattering properties of aluminum nanodisks located at the back side, and optimize them for enhancing the absorption in the silicon layer. We also compare our results with previously optimized silver nanodisks and show that Al nanodisks are nearly as efficient as Ag counterpart. We show that if the absorption in the metallic back reflector (flat metal layer) can be avoided; this results in a further enhancement in absorption in the ultra-thin silicon layer. The proposed configuration results in a broadband (500nm to 1200nm) enhancement of absorption (∼ 58 %) for ultra-thin solar cells and has a great potential in thin film photovoltaic.