Abstract
•We investigate the photoresponse of single crystalline VE-anatase layers.•We find a significantly higher IPCE (47%) value than for comparable anodic TiO2 nanotube arrays (35%).•The single crystalline layers have >100 times faster electron transport.•To make effective electrodes, F-termination of VE-anatase needs to be removed.•The VE-anatase TiO2 layers may have a high potential for future photoanodes.
In the present work, we compare the photoresponse of vertically erected (VE) single crystal anatase layers with that of widely used TiO2 nanotube layers. These VE-anatase layers were grown hydrothermally, directly on fluorine-doped tin oxide (FTO) glass, and consist of an array of anatase single crystal flakes with preferred (001) facets. As formed, these single crystal layers are fluorine terminated – this termination can be removed by a thermal treatment in air. We compare the photocurrent magnitude and photocurrent transients using intensity-modulated photocurrent spectroscopy (IMPS). We find that the “de-fluorinated” VE-anatase layers show significantly higher photocurrents than the comparable nanotube layers. This high efficiency of the VE-anatase layers is due to the electron transport being 100 times faster in these single crystal electrodes, provided that the blocking fluorine termination is removed.