Light trapping in thin-film silicon solar cells by nano-textured interfaces

In superstrate thin-film solar cells light scattering is introduced by the surface texture of the transparent conductive front contact. However, a prerequisite to discuss light trapping in thin-film solar cells is a deeper understanding of the scattering behavior of such randomly textured substrates. The haze, which is widely used to characterize the scattering properties of randomly textured substrates, is an inadequate criterion to correlate the optical quality of the substrate and the measured short circuit current of solar cells. It will be shown that the wavelength dependence of the haze can be used to classify different kind of substrates. Furthermore, the angular resolved scattering properties are analyzed by means of ray tracing based simulation approach. The gained results reveal new aspects for the assessment of light trapping in thin-film silicon solar cells.