Light trapping by direction-dependent light transmission in front-surface photonic nanostructures

Front-surface photonic nanostructures contribute both reduced reflection loss and light trapping to increase optical absorption in solar cells. We investigated the effect of sub-wavelength photonic nanostructures on light trapping in thin-film crystalline silicon solar cells. We clarified that, even though the angle distribution of scattered light is small compared with that in the case of Lambertian scattering, light trapping enhances with increasing depth of the surface photonic nanostructure, which originates from the direction-dependent light transmission in the surface photonic nanostructure. Our findings indicate that this direction-dependent light transmission contributes to the advanced photon management in thin-film solar cells.