US Patent 7468485 Back side contact solar cell with doped polysilicon regions

In one embodiment, a back side contact solar cell includes a tunnel oxide layer formed on a back side of a substrate. A polysilicon layer is formed on the tunnel oxide layer, and dopant sources are formed on the polysilicon layer. Dopants from the dopant sources are diffused into the polysilicon layer to form p-type and n-type regions therein. The p-type and n-type regions form p-n junctions that, among other advantages, allow for relatively high conversion efficiency.