Improving solar cell performance by full aluminum back surface field

Conventional method in building the back side of solar cell is: print dry back contact silver busbar then print dry aluminum to cover the rest of the back surface. Full aluminum back surface field (BSF) is always desired to improve cell performance. Print, dry aluminum to cover the entire back surface then print, dry silver back contact on top of dried aluminum or print, dry and fire aluminum then print dry and fire silver busbars are not feasible. Print, dry silver back contact on dried aluminum then co-fire causes peeling of both silver film and aluminum base support underneath. From this observation, a new peeling material is developed to co-fire with dried aluminum. The new method allows formation of full back surface field, selective peeling of excess aluminum above the BSF and then application of the silver back contact in the peeled area. By this novel concept and design, cell performance improved due to higher Voc and maintains its reliability due to good adhesion and solderability of low temperature firing back contact silver busbars.