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

• Two process simplifications for n-type PERT bifacial solar cells were investigated.
• Good quality emitters were achieved without bulk degradation.
• The processes step number was significantly reduced.
• Efficiencies up to 19.7% on industrial 239 cm² Cz wafers were reached.

In 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 (~660–670 mV) and emitters allow good contacting by screen-printing (ρc=3.0–5.0 mΩ cm2). PERT cells resulting from these processes show very promising performances with efficiency up to 19.7% on industrial 156×156 mm2 pseudo square Cz wafers.