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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 TiO 2 films in situ doped by Au NPs (TiO 2 :AuNPs) deposited by spin coating on a silicon substrate. Photoconductivity and optical properties of the TiO 2 :AuNPs/Si structures were studied in comparison with those of TiO 2 /Si reference samples. We found that an introduction of the 40-50 nm diameter AuNPs into the antireflective TiO 2 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 TiO 2 :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.

The synthesis of Si/SiO2 nanostructures for the application as hetero‐emitter and passivation layer in high‐efficiency solar cells is explored with the long‐term perspective of exploiting quantum size effects for next‐generation photovoltaics. Ultra‐thin oxides are developed by means of oxidizing crystalline silicon using neutral oxygen atoms supplied by a RF plasma source. These oxides are characterized by an abrupt Si/SiO2 junction and good passivation of Si dangling bonds at the interface, a precondition for the implementation of Si/SiO2 nanostructures in photovoltaic devices. Another decisive issue is carrier transport across the SiO2 barrier which is demonstrated in form of a tunneling current in I–V measurements. Such tunneling oxides on Si(111) wafers are used as substrates for the subsequent deposition of Si nanodots. Nanodot synthesis is accomplished by first depositing a few nanometer thick layer of amorphous Si. During a subsequent recrystallization step at T > 600 °C, the surface tension between c‐Si and SiO2 causes a dewetting and, thus, the formation of crystalline Si nanodots, the size of which can be controlled by the thickness of the initial amorphous Si layer. Finally the dots are cladded with a shell of tunneling oxide. A close‐packing of spheres with dots stacked on top of each other is approximated by a repetition of this process.

Abstract:Ultrathin SiO 2 layers for potential applications in nano-scale electronic and photovoltaic devises were prepared by exposure to thermalized atomic oxygen under UHV conditions. Wet-chemical substrate pretreatment, layer deposition and annealing processes were applied to improve the electronic Si/SiO 2 interface properties. This favourable effect of optimized wet-chemical pre-treatment can be preserved during the subsequent oxidation. The corresponding atomic-scale analysis of the electronic interface states after substrate pre-treatment and the subsequent silicon oxide layer formation is performed by field-modulated surface photovoltage (SPV), atomic force microscopy (AFM) and spectroscopic ellipsometry in the ultraviolet and visible region (UV-VIS-SE).