In an effort to reduce the radiation degradation of triple junction solar cells, imbedded photon management is investigated as a means for reducing the middle subcell thickness while maintaining output. The (In)GaAs subcells of the conventional lattice-matched InGaP/(In)GaAs/Ge triple-junction solar cells with back-side light reflecting structures were simulated. Subcells with two-dimensional dielectric moth-eye reflection grating show promising results: more than 70% of incident in-band light is reflected into the non-zero diffraction orders which allows the thickness of the subcell to be decreased from 3.5 to 1.25 mu m. This reduction of the subcell thickness substantially enhances the radiation hardness of the multi-junction solar cell.