The effect of first step anodization time on morphology and photocurrent response of TiO2 nanotube arrays for application in backside illuminated dye-sensitized solar cells

We report on the effect of the first step anodization time on the morphology of TiO2 nanotube arrays grown by the two-step anodization and their photocurrent response in the backside-illuminated dye-sensitized solar cells. Results show a remarkable increase of tube ordering by increasing the first step anodization time. The Fill factor and open circuit voltage of all dye-sensitized solar cells were approximately 60% and 0.77 V respectively, for a range of first step anodic oxidation from 0.5 to 6 h, whereas the short circuit current increased from 0.94 to 1.57 mA/cm2 leading to an enhanced photo-to-current efficiency by 73%. According to open circuit voltage decay and electrochemical impedance spectroscopy (the Nyquist and Bode plots), we attributed such an enhanced cell performance to lower recombination rates due to higher ordered TNAs associated with the actual surface area and coherency of the cells' components.