Noriyoshi Kohama

Effect of perforated transparent electrodes on light transmittance and light scattering in substrates used for microcrystalline silicon thin-film solar cells

The effect of a perforated transparent electrode, which is an electrode punctuated with holes, on light transmittance and light scattering was studied using textured ZnO:Ga formed by wet etching. The perforations were found to play a role not only in improving transmittance but also in maintaining high haze factor. The influence of the surface morphology of textured ZnO:Ga on the growth of hydrogenated microcrystalline silicon and on solar cell performance was also studied. It was found that, while the ZnO:Ga surface is not steep, a height difference is present on the substrate surface at the edge of the perforations. To resolve this problem, an additional thin ZnO:Ga layer was deposited on a substrate which already had a perforated transparent electrode. Improvements in solar cell performance were obtained while high open circuit voltage and high fill factor were maintained.