Ordered crystalline TiO₂ nanohexagon arrays for improving conversion efficiency of dye-sensitized solar cells

Anatase TiO₂ nanohexagon arrays were grown by using an anodization process of Ti foil in fluoride containing electrolytes. Photoanode based on the as-grown anatase TiO₂ nanohexagon arrays for DSSCs showed a power photoconversion efficiency of 4.01% and incident photon-to-current conversion efficiency of 68%, which are significantly higher than those of the device based on anatase TiO₂ nanotube arrays. This improvement in power conversion efficiency should be attributed to the fact that the nanotubes with hexagonal structure have higher surface area to allow the uploading of more dye molecules for light harvesting. Also, the spacing introduced inside the hexagon might allow the dye molecules to cover the interior of the walls. In addition, it is believed that the photoconversion efficiency can be further increased by optimizing the hexagonal structure through the electrochemical conditions. - Graphical abstract: Nanotubes with hexagonal structure have higher surface area to allow the uploading of more dye molecules for light harvesting in dye-sensitized solar cells. - Highlights: • A unique TiO₂ nanohexagon arrays were grown by an anodization process. • Higher surface area for dye uploading provided by the hexagon structure. • TiO₂ nanohexagon based photoanode has PCE of 4.01% and IPCE of 68%