Anodic TiO2 Nanotube Arrays for Dye-Sensitized Solar Cells Characterized by Electrochemical Impedance Spectroscopy

Abstract

This paper reports on the microstructure of anodic titanium oxide (TiO2) and its use in a dye-sensitized solar cell (DSSC) device. When voltages of 60 V were applied to titanium foil for 2 hr under 0.25 wt% NH4F + 2 vol% H2O+C2H4(OH)(2), TiO2 with a nanotube structure was formed. The film, which had a large surface area, was used as an electron transport film in the DSSC. The DSSC device had a short-circuit current density (J(sc)) of 12.52 mA cm(-2), a fill factor (FF) of 0.65, an open-voltage (V-oc) of 0.77 V, and a photocurrent efficiency of 6.3% under 100% AM 1.5 light. The internal impedance values under 100%, 64%, 11%, and 0% (dark) AM 1.5 light intensities were measured and simulated using the electrical impedance spectroscopy (EIS) technique. The impedance characteristics of the DSSC device were simulated using inductors, resistors, and capacitors. The Ti/TiO2, TiO2/Electrolyte, electrolyte, and electrolyte/ (Pt/ITO) interfaces were simulated using an RC parallel circuit, and the bulk materials, such as the Ti, ITO and conducting wire, were simulated using a series of resistors and inductors. The impedance of the bulk materials was simulated using L-0+R-0+R-b, the impedance of the working electrode was simulated using (C-1//R-1)//(R-a+(C-2//R-2), the electrolyte was simulated using C-3//R-3, and the counter electrode was simulated using C-4//R-4. (C) 2012 Elsevier Ltd and Techna Group Sri. All rights reserved.