An ultrathin layer of SiO formed on the surface of a silicon solar cell can significantly reduce the potential induced degradation effect in solar cell modules. In this work, a liquid oxidation (LO) technique was developed to oxidize silicon surfaces by using a Ti/IrO2 CoO2 anode that can produce a large amount of hydroxyl radicals ((OH)-O-center dot) and other species. Our results indicate that the LO SiOx (2.5 nm) layer is very dense, thus the modules made from LO treated cells are better able to mitigate potential induced degradation than modules made from ozone oxidized cells.