Enhanced efficiency of light-trapping nanoantenna arrays for thin-film solar cells.

We suggest a new type of efficient light-trapping structures for thin-film solar cells based on arrays of planar nanoantennas operating far from their plasmon resonances. The operation principle of our structures relies on the excitation of collective modes of the nanoantenna arrays whose electric field is localized between the adjacent metal elements. We calculate a substantial enhancement of the short-circuit photocurrent for photovoltaic layers as thin as 100-150 nm. We compare our light-trapping structures with conventional anti-reflecting coatings and demonstrate that our design approach is more efficient. We show that it may provide a general background for different types of broadband light-trapping structures compatible with large-area fabrication technologies for thin-film solar cells.