Process and Design Freedom Enabled by Back-Contact Solar Cells Minimizing the Inactive Module Area

We present three process and design novelties that enable higher module efficiencies by decreasing solar modules inactive area: i) a gapless stringing procedure ii) a gapless string layup iii) a cross connection behind the active cell matrix All above mentioned innovations are applied for stringed back contact solar cells called Zebra cells which are in house developed all screen-printed IBC solar cells. Yet they are relevant for most wire interconnected BC type cells. The main improvement is an increased module efficiency achieved by reduction of inactive module area. Another advantage of the gapless stringing approach is the uniform aesthetic module appearance relevant to BIPV applications without the necessity to mask interconnection ribbons, especially in the case of applying a black background and/or colored module glass. To show the validity of our approach we have assembled several mini-modules and a full-size module demonstrator in different configurations applying the above-mentioned novelties. A simple geometric calculation shows the potential of inactive area reduction and also factors in shading of cells due to overlaps that are necessary for the practical realization of the gapless approach.