Co-diffused back-contact back-junction silicon solar cells

Aiming for industrial solar cell fabrication the ratio of costs to watt peak has to be lowered [1]. This can be achieved by either decreasing the overall solar cell manufacturing costs including material, process and module assembly or increasing solar cell efficiency [2]. One very promising approach for decreasing optical losses on the front side of the cell and thus increasing the solar cell efficiency is to contact solar cells only on the back side. Back-contact back-junction (BC-BJ) solar cells already showed efficiencies over 24% [3]. Since the assembly of this type of solar cell is combined with a high process effort and hence high production costs, simplifications of the process sequences are needed. This can be achieved e.g. by avoiding several cost-intensive high temperature steps by implementing a co-diffusion process. Further the avoidance of the so called gap region - region between the highly doped areas on the cell rear side - would lead to a reduction of process steps.