Configuration optimization of a nanosphere array on top of a thin film solar cell

Resonant dielectric structures placed on top of a solar cell can enhance light absorption and therefore increase its efficiency. Freely propagating sunlight diffractively couples into the resonant modes of a low loss sphere array. We numerically demonstrate this enhancement using 3D full field finite difference time domain simulations. The coupled energy is then transferred into the active layer underneath and significantly contributes to increase the calculated photocurrent of the solar cell. On a typical thin film amorphous silicon solar cell, a parametric analysis is done. For a hexagonally close packed sphere configuration, we vary the size of the spheres as well as the type of material used. Finally, we study a configuration where high index spheres are embedded in a lower index polymer. This last configuration has the advantage that it can easily be integrated upon solar cell fabrication.