Bifacial Solar Cells with Selective B-BSF by Laser Doping

Abstract

We report on bifacial solar cells with selectively laser doped boron back surface fields reaching an efficiency = 15.9% on solar grade Cz-Silicon. Before laser doping the rear sides of the solar cells are borondiffused in an open tube furnace using a purpose optimized diffusion process. Our patented, scanned laser doping process locally increases the doping under the rear metallization, thus allowing for a shallow doped rear side between the contacts. The laser doping process offers an elegant and reliable approach for the local formation of selectively doped rear surfaces on silicon solar cells. This one additional processing step together with the optimized diffusion process increases the cell performance by D = 1.0% absolute compared to reference bifacial solar cells processed with our standard furnace diffusion process.