To considerably improve the conversion efficiency of industrial solar cells, the effective passivation of the rear surface is a prerequisite. Thermal grown silicon oxides provide an excellent level of surface passivation on lowly doped p-type surfaces. However, dry thermal oxidation processes require relatively high temperatures (?1000°C) and, due to the low growth rate, long process times. To decrease both oxidation temperature and process time, the dry oxidation process can be replaced by a wet oxidation. The most common way to introduce high purity water vapor into the oxidation tube is the pyrolytic generation from high purity gases (H2 and O2). A more easy and cost effective option for the supply of water vapor that was applied within this work is the direct purification of steam. The passivation quality of dry and wet oxides, the latter grown from pyrolytic generated water vapor and purified steam was compared within this work. The passivation quality obtained for the wet oxides grown from purified steam was found to be comparable to those oxides grown from pyrolytic generated water vapor. On laser fired contacts (LFC) solar cells conversion efficiencies well above 20% could be achieved independent of the oxide that was applied for the rear side passivation

In this investigation we compare intrinsic hydrogen diluted amorphous a-Si:H(i) layers deposited by inductively coupled plasma (ICP) to the standard parallel plate (PP) plasma, driven by 13.5 MHz power source. We analyze and compare the growth rate, optical energy gap, homogeneity, passivation quality, and most importantly silicon heterojunction solar cell performance. The ICP a-Si:H(i) layer shows superior properties regarding the growth rate, however, we obtain a slightly better passivation quality with the PP a-Si:H(i) layer, with Voc values up to 723 mV. Looking at the overall solar cell performance we were not able to see any difference between ICP and PP silicon heterojunction solar cell. The best solar cell (with an ICP a-Si:H(i) layer) has an efficiency of 18.7%

Industrial mass production of solar cells is at a transition toward carrier‐selective junction solar cells with passivating contacts such as TOPCon, POLO, or heterojunction technology (HJT). At the same time, many manufacturers consider switching from p‐type Cz‐Si to n‐type Cz‐Si wafers. This contribution indicates that Ga‐doped p‐type Cz‐Si material is still a viable option for the new type of devices while giving an opportunity to benefit from lower wafer cost. The minority carrier diffusion lengths that are an order of magnitude larger than the thickness of the studied HJT and TOPCoRE devices are reported. Stability aspects for operation in the field are discussed. Best TOPCoRE solar cells on Ga‐doped Cz‐Si show a 0.2% higher efficiency than their co‐processed n‐type counterparts.

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