Nano-textured superstrates for thin film silicon solar cells: Status and industrial challenges

Thin film tandem solar cells based on amorphous and microcrystalline silicon (MicromorphTM in superstrate configuration) benefit from strongly light-scattering nano-textured substrates. A development methodology for the evaluation of the performance of the Micromorph test cells deposited on such substrates with very different surface shapes is presented and illustrated. It is shown that growth related defects and non-conformal coverage of the silicon layers restrict the choice of surface shapes for this photovoltaic application. General guidelines are given in this study for the preferred selection of the surface geometry for MicromorphTM test cells. The results indicate that the application of advanced surface shapes for higher conversion efficiencies requires improved silicon deposition process compared to current industrial state-of-the-art.