Ion-implanted and screen-printed large area 20% efficient N-type front junction Si solar cells

This paper reports on the fabrication of high efficiency (~20%) front junction n-type Si solar cells on 239 cm2 Cz using ion implanted boron emitter and phosphorus back surface field (BSF) in combination with screen printed metallization. Cell efficiencies of 19.8% and 20.0% were achieved with SiO2/SiNx and Al2O3/SiNx passivation of boron implanted emitter, respectively, supporting the superiority of Al2O3 passivation. This is consistent with low boron emitter saturation current densities of 76 and 45 fA/cm2 achieved for boron emitter passivated with SiO2/SiNx and Al2O3/SiNx stacks, respectively. Saturation current density in metal contact area of boron emitter and phosphorus BSF was measured directly by varying the metal contact coverage. Detailed analysis of saturation current density showed that the performance of our 20% is largely limited by saturation current density associated with recombination on metal contact area of boron emitter and bulk of phosphorus BSF, which accounted for almost ~50% of the total saturation current density.