Thin film silicon solar cell design based on photonic crystal and diffractive grating structures

In this paper we present novel light trapping designs applied to stand alone and multiple junction thin film silicon solar cells. The new designs incorporate one dimensional photonic crystals as band pass filters that reflect short light wavelengths (400 - 1100 nm) and transmit longer wavelengths(1100 -1800 nm) at the interface between two adjacent cells. In addition, nano structured diffractive gratings that cut into the photonic crystal layers are incorporated to redirect incoming waves and hence increase the optical path length of light within the solar cells. Two designs based on the nano structured gratings that have been realized using the scattering matrix and particle swarm optimization methods are presented. We also show preliminary fabrication results of the proposed light trapping grating structures.