Passivation mechanism in silicon heterojunction solar cells with intrinsic hydrogenated amorphous silicon oxide layers

In this work, we use intrinsic hydrogenated amorphous silicon oxide layers (a-SiO x :H) with varying oxygen content (c O) but similar hydrogen content to passivate the crystalline silicon wafers. Using our deposition conditions, we obtain an effective lifetime (τ eff) above 5 ms for c O ≤ 6 at. % for passivation layers with a thickness of 36 ± 2 nm. We subsequently reduce the thickness of the layers using an accurate wet etching method to ∼7 nm and deposit p- and n-type doped layers fabricating a device structure. After the deposition of the doped layers, τ eff appears to be predominantly determined by the doped layers themselves and is less dependent on the c O of the a-SiO x :H layers. The results suggest that τ eff is determined by the field-effect rather than by chemical passivation.