Pulsed Laser Melting of polycrystalline silicon for advanced solar cells.

Polycrystalline silicon (poly-Si) on ultrathin SiOx passivating contacts are one of the most promising candidates for the development of high-efficiency crystalline Silicon (c-Si) based solar cells. In this framework, Boron- doped p-type poly-Si/SiOx contacts demonstrate inferior surface passivation of c-Si when compared to the Phosphorus-doped counterpart. As a matter of fact Boron tends to accumulate at the interface between SiOx and c-Si, causing degradation in passivation quality. For this reason, in this work we explored nanosecond scale pulsed laser melting (PLM) technique to induce melting and subsequent recrystallization of the poly-Si layer, obtaining spatial and temporal confinement of the dopant atoms during diffusion and incorporation stages, while electrically activating them. Furthermore, in addition to boron, we also used gallium as a novel p- type dopant. The aim is to hyperdope the poly-Si layer as much as possible, overcoming the solid solubility limit of Boron, Gallium and Phosphorus in Si, and at the same time avoiding the degradation of the underlying SiOx. Electrical, chemical and morphological characterization of the samples has been performed, demonstrating a successful outcome in terms of hyperdoping and dopant confinement, eventually proving PLM to be a particularly suitable annealing method for precisely tuning the doping profiles, while achieving highly activated doping concentrations for all types of dopants.