Enhanced light trapping with optical nanoantennas for thin-film solar cells

We propose a new type of efficient light-trapping structures for thin-film solar cells based on arrays of planar nanoantennas whose operational band doesn't match with plasmonic resonances. The operation of our light-harvesting structures is based on the excitation of collective modes of the nanoantenna arrays whose electric field is localized between the adjacent metal elements. We demonstrate theoretically a substantial enhancement of the short-circuit photocurrent for the cases when the photovoltaic layer is as thin as 100-150 nm. We compare our novel light-trapping structures with conventional anti-reflecting coatings. Our approach provides a general background for a design of different types of efficient broadband light-trapping structures for thin-film solar cells technologically compatible with large-area fabrication techniques.