Modelling of the PERC structure with stripe and dot back contacts

Abstract

The PERC cell design offers the possibility of signficantly improved performance over conventional commercial cell designs with only a small increase in process complexity. Optimisation of the PERC structure to date has been aimed at high efficiency cells. This paper reports the results of comprehensive modeling to determine what advantage the PERC structure with dot or stripe contacts has over conventional screen printed rear cells for lower quality substrate wafers. The efficiency trade-offs of contact spacing and contact area are investigated as a function of wafer resistivity, diffusion length and wafer thickness, taking into account recombination elsewhere in the device. The efficiency for a PERC cell and a cell with a silver screen printed rear are compared for different wafer resistivities.