Semitransparent TiO2 nanotube arrays with both ends open by electrochemical anodization and ion-beam etching process

Abstract

Free-standing TiO2 nanotube arrays were prepared by electrochemical anodization method. The as-prepared film was not opaque, but it was a semi-transparent. The mechanical stability of the film gradually increased with increasing film thickness. The TiO2 nanotube array films have different surface morphologies. The surface morphology of the top-surface of film was rough and all the nanotubes of top-surface were open. The compact oxide layer covered bottom-surface was smooth and all the TiO2 nanotube arrays have closed end surface morphologies. The preparation conditions were optimized and the repeatability of the film prepared at 60 V showed good results. Usually, chemical etching method was used to remove the compact oxide layer of nanotube cap. In the present work, low-energy ion-beam etching method was used to remove the compact oxide layer. The orderliness and uniformity of the bottom-surface nanotube arrays were much better than that of chemical etching method. The as-prepared film thickness was calculated as 25 μm. After the ion-beam etching process for an etching time of 1 h, the film thickness was 24 μm. The etch rate of the film was calculated as 1.6 nm min−1. The power conversion efficiency of dye-sensitized solar cell (DSC) increased with increasing film thickness.