Low temperature Si/SiOx/pc-Si passivated contacts to n-type Si solar cells

We describe the design, fabrication, and results of low-recombination, passivated contacts to n-type silicon utilizing thin SiO_x, and plasma enhanced chemical vapor deposited doped polycrystalline-silicon (pc-Si) layers. A low-temperature silicon dioxide layer is grown on both surfaces of an n-type CZ wafer to a thickness of <;20 Å. Next, a thin layer of P-doped plasma enhanced chemical vapor deposited amorphous silicon (n/a-Si:H) is deposited on top of the SiO_x. The layers are annealed to crystallize the a-Si:H and diffuse H to the Si/SiO_x interface, after which a metal contacting layer is deposited over the conducting pc-Si layer. The contacts are characterized by measuring the recombination current parameter of the full-area contact (J_o,contact) to quantify the passivation quality, and the specific contact resistivity (ρ_contact). The Si/SiO_x/pc-Si contact has an excellent J_o,contact = 30 fA/cm² and a good ρ_contact = 29.5 mOhm-cm². Separate processing conditions lowered J_o,contact to 12 fA/cm². However, the final metallization can substantially degrade this contact and has to be carefully engineered. This contact could be easily incorporated into modern, high-efficiency solar cell designs, benefiting performance and yet simplifying processing by lowering the temperature and growth on only one side of the wafer.