Light trapping enhancement in thin film solar cells by breaking symmetry in nanostructures

We experimentally demonstrate highly efficient light-trapping structures that is achieved by breaking the symmetry in inverted nanopyramids on c-Si. The fabrication of these structures is cost-effective and scalable. Our optical measurement for the structures on 10-μm-thick c-Si cells shows the Shockley-Queisser efficiency of 27.9%. We further fabricate plasmonic metal structures on the symmetry-breaking inverted nanopyramids. When a light-absorbing polymer layer is deposited on top of the plasmonic structures, we observe that the plasmonic light trapping exceeds the Lambertian limit. The remarkable light trapping increases the short circuit current by 2.5 times. We expect the symmetry-breaking structures to be broadly applicable to thin-film solar cells.