21.7% Large Area n-PERT Silicon Solar Cells Using Screen-Printed Aluminium with Open Circuit Voltage above 690mV

32nd European Photovoltaic Solar Energy Conference and Exhibition; 439-442
Large area n-type rear-junction Passivated Emitter Rear Totally-diffused (PERT) solar cells with efficiency of 22.5% were recently reported by imec using rear sputtered Al. To develop a more industrially relevant process, screenprinting of Al is also currently investigated as the rear metallization. In this case, an Al p+ emitter is locally formed by Al- Si alloying during a firing step. The quality of this p+ emitter is crucial to the performance of the final devices. However, this is a challenging and less controlled process in terms of thickness of the doping layer and possible formation of voids. In this work, the contact geometry and the firing are optimized and their impact on the void and Al p+ layer formation is studied. Using the optimized processing parameters, large area n-PERT solar cells with screen-printed Al with efficiency up to 21.7% are fabricated. These cells demonstrate high values for the open circuit voltage (Voc) up to 690mV. This proves the feasibility of using screen-printed Al for high performance n-PERT cells.