Enhancement of the light trapping by double-layered surface texture of ITO/AZO and AZO/AZO transparent conductive films

• Double-layered surface textures are designed to improve the light trapping.
• 400–600 nm feature sizes and ~68 nm RMS value are obtained in AZO/AZO films.
• The Fe(III) catalyst can greatly increase the etching rate.
• The double-textured AZO samples exhibit higher haze values (>50%) at 550 nm.

Double-layered surface textures of ITO/AZO (In2O3:Sn/ZnO:Al) and AZO/AZO transparent conductive films are conducted with a process of deposition, first-etching, re-deposition and re-etching. Light trapping ability can be greatly reinforced by the induced double broad feature distributions. For the re-etching process, stronger etching pits with 400–600 nm feature sizes and ~68 nm Root Mean Square (RMS) roughness are obtained in AZO/AZO films compared to that of the first-etching samples. The use of Fe(III) catalyst can greatly increase the etching rate. Diffuse transmittance with the largest value (56.97%) is observed for the double-layered AZO–HCl/AZO–HCl+FeCl3 sample due to the formation of crater-like morphology in the mezzanine and the surface of the films. The double-textured AZO samples exhibit higher haze values (50.73% and 55.50%) at 550 nm, corresponding to the AZO/AZO samples using HCl+FeCl3 or HCl alternately. For ITO related samples, the resistivity keeps the order of 10−4 Ω cm after the re-deposition. While, for AZO/AZO films, a slight increment of resistivity and carrier concentration is observed due to the chemical etching. These double-textured structures imply that the films have potential application in thin film silicon (TFS) solar cells for light trapping.