Large Area Screen Printed N-Type MC-SI Solar cells With B-Emitter: Efficiencies Close to 15% and Innovative Module Interconnection

In this paper we present n-type Si solar cells on large area mc-Si wafers with a boron diffused emitter at the front side. The focus of our studies is mainly related to the front surface of the solar cell. We have optimised BBr₃-diffusion and in-situ oxidation with respect to the homogeneity of the sheet resistance and substrate degradation. After diffusion even a slight improvement of the minority charge carrier lifetime was measured, which can be related to B-gettering. The emitter is contacted by AgAl-paste and passivated by thermal SiO₂. The development and optimisation of all processes led to solar cells with efficiencies of 14.7% on mc-Si and 17.1% on Cz-Si substrates. In addition to this we present an innovative interconnection of modules using our developed cell (patent pending). We show an alternate serial interconnection of p- and n-type solar cells resulting in easier module processing