Photoconductivity and optical properties of silicon coated by thin TiO ₂ film in situ doped by Au nanoparticles

Light trapping enhancement by plasmonic-active metal nanoparticles (NPs) is believed to be a promising approach to increase silicon-based solar cell efficiency. Therefore, we investigated TiO₂ films in situ doped by Au NPs (TiO₂:AuNPs) deposited by spin coating on a silicon substrate. Photoconductivity and optical properties of the TiO₂:AuNPs/Si structures were studied in comparison with those of TiO₂/Si reference samples. We found that an introduction of the 40-50 nm diameter AuNPs into the antireflective TiO₂ layer deteriorates the antireflection properties and decreases the external yield of photogeneration of charge carriers. This is due to an increase of the layer reflection in the red-IR part of the spectrum, and due to the parasitic absorption of light by AuNPs in the blue-green part. Charge carrier recombination effect at the TiO₂:AuNPs/Si interface is also found to decrease the external yield. We conclude that the TiO ₂:AuNPs layers could potentially be applied on the rear but not on the front side of Si solar cells.