Development of industrial processes for the fabrication of high efficiency n-type PERT cells

International audienceIn this work, two process simplifications for n-type PERT (passivated emitter rear totally diffused) bifacial solar cells are investigated. Both are based on a single thermal treatment for elaborating boron and phosphorus doped regions aiming at reducing the number of high temperature steps of standard process. The first simplification shows a mixed co-diffusion from a gaseous source of phosphorus and a boron doped dielectric layer elaborated by low frequency plasma enhanced chemical vapor deposition (PECVD). The second exhibits two independent ion implantations, followed by a co-anneal/activation step. In both cases, implied open-circuit voltages are similar to standard process ($\sim$660-670 mV) and emitters allow good contacting by screen-printing ($ρc$= 3.0-5.0 m$\Omega$ cm$^2$). PERT cells resulting from these processes show very promising performances with efficiency up to 19.7% on industrial 156 x 156 mm$^2$ pseudo square Cz wafers