Large area tunnel oxide passivated rear contact n-type Si solar cells with 21.2% efficiency

This paper reports on the implementation of carrier-selective tunnel oxide passivated rear contact for high-efficiency screen-printed large area n-type front junction crystalline Si solar cells. It is shown that the tunnel oxide grown in nitric acid at room temperature (25 degrees C) and capped with n(+) polysilicon layer provides excellent rear contact passivation with implied open-circuit voltage iV(oc) of 714mV and saturation current density J(ob)' of 10.3 fA/cm(2) for the back surface field region. The durability of this passivation scheme is also investigated for a back-end high temperature process. In combination with an ion-implanted Al2O3-passivated boron emitter and screen-printed front metal grids, this passivated rear contact enabled 21.2% efficient front junction Si solar cells on 239 cm(2) commercial grade n-type Czochralski wafers. Copyright (C) 2016 John Wiley & Sons, Ltd.