15% efficient large area screen printed string ribbon solar cells

Large area solar cells have been processed at the University of Konstanz using a standard industrial type SiN fire-through process on Evergreen Solar´s String Ribbon multicrystalline silicon material. After optimisation of the screen printing step and emitter sheet resistivity, efficiencies of 15% have been reached on 8×10 cm² cells almost independent of material bulk resistivity, which was varied between 1-5 Ωcm. These are the highest large area efficiencies reached on this very promising and cost-effective material using an industrial type process. Cell parameters exhibit a high homogeneity, demonstrating the excellent post-processing material quality. Further improvements within the solar cell process are still possible and could lead to improved results in the near future.