Large-Area n-Type PERT Solar Cells Featuring Rear p+ Emitter Passivated by ALD Al2 O3

We present large-area n-type PERT solar cells featuring a rear boron emitter passivated by a stack of ALD Al
₂
O
₃
and PECVD SiO
_x
. After illustrating the technological and fundamental advantages of such a device architecture, we show that the Al
₂
O
₃
/SiO
_x
stack employed to passivate the boron emitter is unaffected by the rear metallization processes and can suppress the Shockley-Read-Hall surface recombination current to values below 2 fA/cm
²
, provided that the Al
₂
O
₃
thickness is larger than 7 nm. Efficiencies of 21.5% on 156-mm commercial-grade Cz-Si substrates are demonstrated in this study, when the rear Al
₂
O
₃
/SiO
_x
passivation is applied in combination with a homogeneous front-surface field (FSF). The passivation stack developed herein can sustain cell efficiencies in excess of 22% and V
_oc
above 685 mV when a selective FSF is implemented, despite the absence of passivated contacts. Finally, we demonstrate that such cells do not suffer from light-induced degradation.