New technologies for back contact module assembly

Back contact cells not only require adapted technologies for module assembly, but they offer cost saving potentials on module level. Cell interconnection and layup are mostly affected. We looked at approaches that use materials already proven in PV industry. For edge back contact cells, mechanical stress relief in cell spacing may be achieved by a segmented bow design. Finite Element Analysis has been used to assess mechanical stress. For distributed back contacts, tapered interconnector designs with constant current density can make more efficient use of copper material compared to standard ribbons. With stress relief junctions, the thermo-mechanical stress between adjacent joints can be controlled and bi-metallic deformation effects after soldering are avoided. In terms of cell layup, we developed a technology that requires only one cell handling step. After the cell is placed on the encapsulant/glass stack, it is fixed by vacuum and can be further processed and laminated. Several implementations have been tested on small modules up to 24 cells.