Influence of the organic electrolyte and anodization conditions on the preparation of well-aligned TiO2 nanotube arrays in dye-sensitized solar cells

Abstract

► Dye-sensitized solar cells (DSSCs) were fabricated using well ordered TiO 2 nanotubes . ► Nanotubes were prepared by electrochemical etching of Ti foil in fluorinated organic solvents . ► Using NH 4 F-EG as an anodizing electrolyte, longer nanotube length of 18 μm was achieved. ► NH 4 F-EG system showed higher energy conversion efficiency ( η = 2.13%) than HF-DMSO system ( η = 1.16%). ► We conclude that the lower efficiency may be due to the lower dye adsorption surface area. Dye-sensitized solar cells (DSSCs) comprising randomly networked titanium nanoparticles usually exhibit lower energy conversion efficiency and limited electron mobility due to the scattering and trapping of free electrons. In this study, attempts were made to improve the electron mobility in DSSCs using vertically aligned and well ordered TiO 2 nanotubes. These nanotubes were prepared by the electrochemical etching of Ti foil under potentiostatic conditions in four different fluorinated organic solvents under varying anodizing conditions like reaction time, and annealing before/after anodization. Sonoelectrochemistry was found to be more effective to synthesize well-ordered TiO 2 nanotubes than just stirring the electrolyte as in conventional electrochemistry. Using NH 4 F-EG as an anodizing electrolyte, unique TiO 2 nanomorphology with longer nanotubes length of 18 μm was achieved. The photo-electrochemical properties of the DSSCs with back illumination under UV (<400 nm) and simulated sunlight (AM 1.5) were also studied, and exhibited an efficiency of 2.13%. The results are reported in detail here.