A bilayer structure of a titania nanoparticle/highly-ordered nanotube array for low-temperature dye-sensitized solar cells

Abstract

A chemical-free, environmentally friendly and harmless water immersion method is developed to delaminate anode oxidationtitania nanotube (TNT) arrays from Ti foils to obtain a free-standing TNT membrane. The as-synthesized TNT membrane with tunable thickness which is controlled by anodization time are used in low-temperature dye-sensitized solar cells (DSSCs) as a second layer to improve the DSSC efficiency. Compared with the common titania nanoparticle electrode, a water-delaminated TNT membrane electrode of 16 μm in thickness can significantly enhance the DSSCs photovoltaic performance with a short-circuit current density from 3.87 to 7.63 mA cm⁻² and a fill factor from 0.637 to 0.708, which combinatorially lead to a remarkable increment of photo conversion efficiency from 1.70% to 3.68%. The results show that, owing to its vertically aligned ordered nanotube structure, the TNT arrays exhibit trifunctional behavior when used as an electrode, which are charge generation, light scattering and I₃⁻ diffusion improvement.