Towards high-efficiency ultra-thin solar cells with nanopatterned metallic front contact

We propose a novel design using multi-resonant absorption to achieve efficient light-trapping in ultra-thin (< 100 nm) solar cells. It is based on a patterned metallic layer which i) strongly confines light in an ultra-thin and flat absorber layer and ii) plays the role of a front contact combining high optical transparency and good electrical conductivity. This versatile approach is applied to different solar cells materials (a-Si:H, GaAs) and geometries of the patterned film (1D or 2D). We demonstrate a theoretical conversion efficiency over 20 % using a 2D silver nanogrid to enhance absorption in a 25 nm-thick GaAs absorber layer. First demonstrators were fabricated and optically characterized. This work should pave the way towards high-efficiency ultra-thin solar cells.