Understanding the Origin of Recombination Losses After Co-Plating of Bifacial Solar Cells: In-Depth Microstructure Study

Large area co‐plated bifacial n‐PERT cells with polysilicon passivating contacts on both sides

“…This can cause significant parasitic absorption in the cells. Furthermore, as mentioned above, the activation step before plating etches (consumes) some of the Si, but the etch rate of p‐doped Si is much lower than n‐doped Si 24 . Therefore, there is room to decrease the thickness of the front poly‐Si.…”

“…It is noted that the polysilicon thickness listed here is estimated from the etch rate of poly‐Si, measured on test wafers (by cross‐section SEM images) after etching in TMAH for varying times. Loss in poly‐Si thickness due to laser ablation 10 and due to plating activation 24 was not measured. Compared with the inkjet‐patterned cells, the cells with the laser oxidation route show >1% absolute higher FF, even though a lower thermal budget (same as previous batches of cells) was used.…”

“…Since the front side laser ablation needs to be aligned to the patterned polysilicon underneath, various poly‐Si widths were tested to successfully align the laser ablation step for both inkjet and laser oxidation patterning routes. Finally, an immersion plating process of Ni/Ag stack 23,24 was applied (Figure 2K) to obtain the finished solar cell. It is noted that the following steps of the previously reported sequence have been applied for the plating process in this work: (1) HF dip to remove oxide from the surface of poly‐Si after laser ablation; (2) surface activation by bath immersion, which etches part of the poly‐Si layer and applies a thin layer of Ni for further plating; (3) electroless plating of Ni by immersion; and (4) Ag for improving line conductivity and as a capping layer by immersion plating.…”

“…This simultaneous Ni/Ag co‐plating process on n & p‐type doped Si is suitable for the metallization of bifacial cells prior to multiwire module integration. Recently, a detailed investigation of this contactless plating process (when applied to n‐PERT solar cells) and its challenges has been published 24 . In the present work, we target the application of this co‐plating process on both n + and p + polysilicon contacts.…”

“…Recently, a detailed investigation of this contactless plating process (when applied to n-PERT solar cells) and its challenges has been published. 24 In the present work, we target the application of this coplating process on both n + and p + polysilicon contacts. We intend to show the viability of bifacial n-PERT cells with a potential efficiency above 24% using two-side passivating contacts with Ni/Ag plating as a metallization scheme on both sides.…”