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The potential of in situ phosphorus (P)-doped polycrystalline silicon (poly-Si) films by low pressure chemical vapor deposition (LPCVD) was studied for the realization of poly-Si/SiO x passivating contacts. In situ doping of poly-Si, as an alternative to ex situ methods, could enable simpler fabrication of industrial solar cells featuring these passivating contacts. With this approach, recombination current densities down to 1.7 fA/cm2 and 3.5 fA/cm2 were achieved on saw-damage removed and textured Cz-Si surfaces, respectively. It was found that the use of thermal SiO x , high active doping in the poly-Si, and hydrogenation improve the passivation quality. In addition, while post-LPCVD annealing was also beneficial, dopant loss from poly-Si at high annealing thermal budgets was observed to be detrimental to the specific contact resistivity and passivation quality, thus making it crucial to mitigate such dopant losses.

The current work is aimed at the development of the building blocks for the integration of polysilicon-based passivating contacts in co-plated n-PERT front junction solar cells. We show that both n-type poly and p-type poly layers (called n-poly and p-poly hereafter) can be obtained simultaneously by the sintering of undoped (i-poly) layers during the POCI 3 diffusion that induces the auto-doping from an existing B-doped emitter. State of the art J 0 values with very high uniformity were measured for n-poly, auto doped p-poly, and boron emitter. The total area weighted J 0 of a passivated cell before metallization is calculated to be around 32 fA/cm2• We also show the viability of a laser oxidation process to pattern the front p-poly Si layer without measurable damage. Finally, we demonstrate laser ablation and plating processes that induce only very limited damage, leading to a high iVoc of around 700 mV for asymmetric samples with p and n-poly passivated surfaces.