Ion implanted passivated contacts for interdigitated back contacted solar cells

We describe work towards an interdigitated back contacted (IBC) solar cell utilizing ion implanted, passivated contacts. Formation of electron and hole passivated contacts to n-type CZ wafers using tunneling SiO₂ and ion implanted amorphous silicon (a-Si) are described. P and B were ion implanted into intrinsic amorphous Si films at several doses and energies. A series of post-implant anneals showed that the passivation quality improved with increasing annealing temperatures up to 900 °C. The recombination parameter, J_o, as measured by a Sinton lifetime tester, was J_o ~ 14 fA/cm² for Si:P, and J_o ~ 56 fA/cm² for Si:B contacts. The contact resistivity for the passivated contacts, as measured by TLM patterns, was 14 milliohm-cm² for the n-type contact and 0.6 milliohm-cm² for the p-type contact. These J_o and p_contact values are encouraging for forming IBC cells using ion implantation to spatially define dopants.