Non-plasmonic light trapping for thin film solar cells

We propose the enhancement of the photovoltaic absorption in thin-film solar cells using densely-packed arrays (not obviously regular) of non-absorbing submicron or micron-sized non-plasmonic spheres located on top of the cell. The spheres can decrease reflection forming an effective blooming layer but simultaneously they can suppress the transmission through the photovoltaic layer transforming the incident radiation into a set of collimated beams. The focusing of the light inside the photovoltaic layer allows enhanced useful absorption in it leading to the increment of the photovoltaic current. Every sphere focuses the incident wave separately - this mechanism does not require collective effects or resonances and is therefore takes place in a wide spectral range. Since the fabrication of such the coating is easy, our light-trapping structure may be cheaper than previously known light-trapping ones and perhaps even than flat anti-reflecting coatings.