Low Cost Fabrication of Back Contact Crystalline-Silicon Heterojunction Solar Cells with n-a-Si Layers Partially Converted from p-a-Si by Phosphine (PH3) Plasma Ion-Implantation

A novel low cost method for fabricating interdigitated back contact crystalline silicon (c-Si) heterojunction (IBC-SHJ) solar cells is proposed. In the method, selected patterned areas of p-a-Si layer are converted to n-a-Si by phosphine (PH
₃
) plasma ion-implantation in order to form interdigitated n- and p-type a-Si regions for back contact electrodes. It is found that p-a-Si can be converted to n-a-Si while the passivation quality is kept sufficiently high. Since H atoms implanted together with P atoms in plasma ion-implantation play a role for eliminating defects created by implantation, the carrier lifetimes degraded after implantation can be restored by the annealing at temperatures just over 200 °C, although the effect of such low temperature annealing cannot be expected in the conventional ion-implantation with mass-separator. The annealing after plasma ion implantation is one of the keys to obtain high performance solar cells. The various annealing procedures are studied. Finally, it is confirmed that SHJ solar cells can be fabricated and operated by using the PH
₃
plasma ion implantation to show the feasibility of low cost fabrication of IBC-SHJ solar cells.