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°C) and capped with n + polysilicon layer provides excellent rear contact passivation with implied open‐circuit voltage iV oc of 714 mV and saturation current density J 0b ′ 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 Al 2 O 3 ‐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.