Polysilicon tunnel junctions as alternates to diffused junctions

We report use of heavily doped polysilicon combined with a tunnel dielectric to provide an alternate to diffused junctions for silicon solar cells. Thin tunnel dielectrics (6-12Ã ) are fabricated using methods adapted from IC processing. These serve as diffusion barriers and passivation layers. When combined with heavily doped polysilicon, they can form an ideal step junction with interface passivation, enabling low dark currents not possible with diffused emitters. We show that it is possible to obtain hyper-abrupt junctions with the tunnel layer providing interface passivation, and that these junctions obtain a VOC of 676 mV on 780 µm thick substrates.