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Interdigitated back contact silicon solar cells with tunnel oxide passivated contacts formed by ion implantation
In this work interdigitated back contact (IBC) silicon solar cells featuring tunnel oxide passivated contacts (TOPCon) formed by ion implantation into amorphous silicon (a-Si) layers are proposed. Ion implantation is applied to locally overcompensate an in-situ boron-doped TOPCon layer with phosphorus which opens a promising route to a simplified fabrication process for IBC solar cells featuring passivated contacts. The impact of ion implantation doses and annealing conditions on the passivation quality of the phosphorus-doped TOPCon layers was studied. It was found that excellent surface passivation with implied open-circuit voltages (iVoc) of 710 mV can be achieved for phosphorus implantations overcompensating the in-situ boron-doped TOPCon layers which exhibit iVoc values of 680 mV. The TOPCon layers were implemented into small area IBC silicon solar cells leading to opencircuit voltages (Voc) of 681 mV and pseudo fill factors (pFF) of 82.2% showing the potential of this concept. However, further investigations are required to reduce the contact resistance which at the current status of the development limits the extraction of charge carriers and thus the conversion efficiency.