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.