TiO₂ Nanotube Arrays Formed on Ti Meshes with Periodically Arranged Holes for Flexible Dye-Sensitized Solar Cells

Vertically oriented TiO2 nanotubes (VOTNs) were prepared on Ti mesh substrates with periodically arranged holes by electrochemical anodization, which were then used as the photoanodes for flexible dye-sensitized solar cell (DSSC) fabrication. The VOTNs were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of the anodization on the physical features of the VOTNs, such as nanotube diameter, wall thickness, and nanotube length, were studied in detail. The Ti mesh is an ideal candidate for DSSC substrates due to its highly bending ability under external force. The photo-to-electric conversion efficiency (η) of the mesh-VOTN-based DSSCs is dependent on the TiO2 nanotube length, which can achieve an efficiency of 2.66% at 100 mW cm–2 under AM 1.5 simulated full light when the nanotube length is ∼18 μm. The DSSC performance dependence on the Ti mesh geometry and the incident angle of the illuminated light were characterized by current density vs voltage (I–V) measurements. The DSSC efficiency is also in close relation to the incident angle of the incoming light, which slowly decreases as the incident angle increases from 0 to 90° but does not decrease much even under 30° bending. The excellent transparency and bendability subjected to external force make this kind of flexible VOTN-based DSSC show great potential in the future energy applications.