Etching Modulated Surface Textures into Sputtered ZnO:Al Films

Abstract

Zinc oxide is often used as the transparent conductive layer in thin-film solar cells. In thin-film silicon solar cells the ZnO layer is additionally used as a source of light trapping; light scattering features can be introduced by sputter deposition and etching of ZnO in a dilute HCl solution. To further improve light trapping modulated surface textures, surfaces with more than one size texture, are of interest. It has recently been shown that etching in HF yields a higher crater density than HCl on polycrystalline ZnO surfaces. Here we use the different etching characteristics of HCl and HF to create modulated surfaces using a fairly simple two-step etching process. Additionally, amorphous silicon solar cells are fabricated on the modulated surface.