23rd International Conference on Amorphous and Nanocrystalline Semiconductors (ICANS 23)

In thin-film solar cells based on a-Si:H and µc-Si:H, textured surfaces are used to increase the absorption of light, in particular for larger wavelengths where the intrinsic absorption is very low. In the article by Bittkau and Beckers on pp. 661–666, the light scattering at textured a-Si:H/µc-Si:H tandem solar cells is studied in the optical near-field both experimentally by means of near-field scanning optical microscopy (NSOM) and theoretically by rigorous solution of Maxwell's equations. It is shown that the improvement of light absorption due to the texture is borne by the scattering into evanescent light modes. The intensity of these light modes decreases exponentially with the distance from the surface, and they are therefore only accessible in the optical near-field. Methods are shown to extract the evanescent part of light from the spatial distribution of the total light intensity, both theoretically and experimentally. With this technique, maps of local light trapping efficiencies are generated. These maps show correlation to topographic information. The understanding of such correlations is essential for the further improvement of light trapping.