Influence of a sputtered compact TiO2 layer on the properties of TiO2 nanotube photoanodes for solid-state DSSCs

Abstract

TiO2 nanotube arrays (TNA) elaborated on transparent and conducting substrates are promising materials for photoanodes in dye-sensitized solar cells as the reduced dimensionality enhances their transport properties. TNA were obtained by anodization of Ti films deposited by magnetron sputtering on transparent conducting oxide-coated glass. This study presents the impact of introducing a compact TiO2 underlayer on the morphological, optical and electrochemical properties of the TNA photoanodes.The TNA morphology was found to be more regular with a TiO2 underlayer and the macroscopic homogeneity of the samples was also increased. This is ascribed to a strong reduction, in the presence of the compact TiO2 underlayer, of a side reaction leading to oxygen evolution and destructuring the TNA film during anodization.As a consequence, the optical and transport properties (characterized by UV–vis and electrochemical impedance spectroscopy, respectively) were improved, together with an increased photovoltaic efficiency. Keywords: Dye solar cells, Nanotubes, Thin films, Sputtering, Anodization