Laser Ablation of Passivating SINx Layers for Locally Contacting Emitters of High-Efficiency Solar Cells

Local contacts through dielectric layers are an important prerequisite for the production of very high efficiency SiO₂-or SiN_x-passivated silicon solar cells. We use laser ablation as a contactless process for local removal of dielectric layers. This contactless process is suitable for processing very thin wafers without cell breakage. Carrier lifetime measurements indicate that our laser ablation process produces no or only negligible damage to the silicon crystal. Open-circuit voltages of solar cells which were locally contacted through laser ablated SiN_x underline the finding that the crystal damage is negligible. High fill factors and low series resistances of 0.6 Ohmcm² reveal the successful local opening of the passivating dielectric layer. These properties qualify local laser ablation of passivating dielectric layers for the production of high-efficiency solar cells. In addition, the contactless nature of laser ablation makes this technique attractive for processing very thin silicon wafers