Super-Lambertian photocurrent-generation in solar cells with periodically textured interfaces

We studied solar cells with periodic interface texture. For periods of 550 and 833 nm, we found that the measured photocurrent increases under oblique incidence and assumes a maximum between 20 and 30°. For the geometries used in our experiments, the initial increase occurred for conditions close to those of photonic band gaps. In addition to a forbidden band of energies where waveguide modes cannot propagate, we found that the coupling to the high-energy branches was suppressed under conditions of high symmetry such as sinusoidal interface geometry and perpendicular incidence.