Abstract
In order to increase the optical path length in thin Si solar cells for the efficiency enhancement, we examined a method to use scatterers of air spheres on the 10 nm scale. The air spheres were randomly embedded on the backside of solar cell to cause the Rayleigh scattering. The incident solar light propagates in the lateral direction after the scattering, increasing the optical path length much longer than the cell thickness. According to the simulations, the light was found to be sufficiently absorbed due to the scattering even for the wavelength over 1100 nm, which is difficult to be absorbed in ordinary thin Si cells. In experiments, air holes in a porous Si layer were examined as the scattering sources, showing the behavior similar to the simulation result. These results suggest that the backside scatterers are useful for the efficiency enhancement in thin Si cells.