Self-aligned laser opening and stencil metallization for silver-free contacts in silicon solar cells

Overreliance on silver in solar cell manufacturing places an immense challenge on sustainability. Terawatt-scale solar energy generation is required within the next few decades, and current attempts to replace silver screen printing are inferior compared to conventional techniques. This work reports on a novel metallization methodology using a UV picosecond laser to ablate textured surface dielectric layers in a pattern defined by an in situ stencil shadow mask. Since the stencil mask does not need to be removed, a metal contact can be directly deposited employing printing or vapor deposition in one integrated process. Here, we demonstrate 26 μm wide metal fingers via thermally evaporated aluminum directly deposited onto laser-patterned point contacts of 16.9 × 19.1 μm2 size. Optical and electron microscopy analysis shows that the UV picosecond laser ablation damage is limited, and sufficient alignment is achieved. A line resistivity of 15.74 ± 2.35 Ω/cm and a contact resistivity of <10 mΩ·cm2 show the current-carrying capabilities of the contacts. Complete solar cell devices were produced using our new stencil self-aligned contacts, and electrical measurements show a pseudo-efficiency of 18.8%. This novel approach could potentially lead to a replacement of non-sustainable silver as front and back contacts for bifacial solar cells.