Electrodeposited Al2O3 composite Cr-C alloy coatings were produced from an oxalic acid bath prepared by adding oxalic acid to a hot CrO3 solution. Chromium ions in the oxalic bath include Cr3＋ oxalate complex and Cr6＋ ions. The Al2O3 particles were co-deposited easily along with the Cr-C alloy coating from the oxalic bath. The content was controlled up to about 3 wt% by plating conditions. The Al2O3 contents of the coatings decreased with current density and increased with bath temperature. The added amount of oxalic acid at make-up of the bath increased the Al2O3 contents of the coatings. The co-deposition mechanism was supported with a two-step adsorption mechanism proposed by Guglielmi, but the adsorption of Al2O3 tothe cathode in the oxalic bath was much weaker than that of either Ni composite plating or Cr composite plating.
Antireflection of a silicon surface is an important means of increasing the photocurrent density and thereby improving solar cell conversion efficiency. We have produced thin nanohole arrays on silicon solar cells using metal-assisted-etching with electrolessly deposited silver nanoparticles. The nanohole array acts as an optical film, decreasing silicon surface reflectance, increasing photocurrent, and causing no damage to the pn-junction.