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

Abstract

The effect of a perforated transparent electrode, which is an electrode punctuated with holes, on light transmittance and light scattering was studied using textured $\mathrm{ZnO}:\mathrm{Ga}$ 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 $\mathrm{ZnO}:\mathrm{Ga}$ on the growth of hydrogenated microcrystalline silicon and on solar cell performance was also studied. It was found that, while the $\mathrm{ZnO}:\mathrm{Ga}$ 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 $\mathrm{ZnO}:\mathrm{Ga}$ 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.