Aluminum alloy back p–n junction dendritic web silicon solar cell

A new silicon solar cell structure is presented in which the p–n junction is formed by alloying aluminum with n-type silicon, and where this p–n junction is located at the back (unilluminated) side of the cell. With a phosphorus front diffusion, the resultant n+np+ structure has been implemented using dendritic web silicon substrates which are 100 μm thick and doped with antimony to 20 Ω cm. Such a structure eliminates shunting of the p–n junction, provides an effective front surface field, enables a high minority carrier lifetime in the base, and is immune to light-induced degradation. Using only production-worthy, high-throughput processes, aluminum alloy back junction dendritic web cells have been fabricated with efficiencies up to 14.2% and with corresponding minority carrier (hole) lifetime in the base of 115 μs.