TiO2 Nanotube/Chalcogenide-Based Photoelectrochemical Cell: Nanotube Diameter Dependence Study

Abstract

We present photoelectrochemical results for anodic TiO2 nanotube layers grown with different diameter sizes (21, 35, 56, and 95 nm) with a thickness of approximately 560 nm using a novel anodization protocol. These tube layers were utilized as highly ordered n-type conductive scaffold for the inorganic chromophore Sn–S–Se. While downscaling the nanotube diameter significantly increased the number of nanotubes per square unit (from 5.6 × 109 to 7.2 × 1010 pcs/cm2) and thus the active surface area increased as well, we found that the photoelectrochemical response in the UV light was identical and thus independent of the TiO2 nanotube diameter in the range of nanotube diameters from 35 to 95 nm. Further, we demonstrate that a heterostructured photoelectrochemical cell consisting of TiO2 nanotubes sensitized with crystalline Sn–S–Se chromophore showed higher photocurrent density (from 6 to 32 μA/cm2 for the wavelength of 460 nm) with increasing nanotube diameter size. Upon detailed SEM analyses it was reveale...