Directional selectivity and light-trapping in solar cells

The Yablonovitch limit for light trapping in solar cells with Lambertian surfaces can be increased using angle selective absorbers thereby exploiting the limited incidence angle of solar radiation. We simulate the efficiency gain or loss caused by an angular and energy selective filter on top of the absorber, compared to a Lambertian and a flat absorber. Additionally, we introduce two possible implementations of such a filter, a Rugate stack and inverted opal layers.