Impact of Front Side Pyramid Size on the Light Trapping Performance of Wafer Based Silicon Solar Cells and Modules

Smaller pyramid sizes for Silicon solar cell front side textures attract more and more interest. At the same time a very good optical performance of the front side texture is crucial to achieve high PV module efficiencies. In this paper an optical study of the impact of periodically arranged front side pyramids on the useful absorption in a Silicon solar cell is presented. Also a way to account for random pyramids is described. Results for solar cells facing semi-infinite EVA/glass are compared to the modeling results of a full solar module stack with the help of the OPTOS formalism. We found that the impact of different pyramids differs depending on the quality of the planar rear side reflector. It is shown that the impact of the module case is crucial and that it has to be accounted for when predicting the optimal pyramid sizes that are relevant for cell and module manufacturers. We also demonstrate that the use of simple parameters such as a single pass light path enhancement factor for the structured surface can lead to wrong conclusions, and a full modeling is required to predict the real module performance. The results indicate that the overall optical performance of a solar module does almost not vary for pyramid sizes above 600 nm.