Building blocks for back-junction back-contacted cells and modules with ion-implanted poly-Si junctions

We propose a process for a back-junction back-contacted solar cell (including module interconnection) combining a high efficiency potential and a lean process flow. This structure offers potential for (i) a high J_sc - no optical shading losses due to the absence of front-side metallization and minimized absorption losses at the cell front-side, (ii) a high V_oc - excellent passivation including “passivated contacts” based on poly-Si/c-Si junctions, and (iii) a high FF - large area contacts with low contact resistance and the absence of busbar losses due to a two-layer metallization. A lean process flow becomes feasible by utilizing two enabling technologies - in situ patterned ion implantation and module interconnection by laser welding (AMELI). We present experimental results for the main building blocks: (1) Patterned ion implantation yields an excellent recombination behavior homogeneously on 6", (2) Ion-implanted poly-Si / c-Si junctions enabling V_oc values up to 742 mV and J_0e values down to 1.3fA/cm², (3) Al₂O₃ front-side passivation enabling Jsc values up to 41.8 mA/cm² and IQE values > 1 for λ <; 350 nm, and (4) busbarless, silver-free AMELI two-layer interconnection. As an intermediate step, we fabricated ion-implanted BJBC cells with conventional junctions and metallization with efficiencies up to 22.1% on 6".