Crystals with Octahedron-like Morphology for Dye-Sensitized

anostructured TiO2 is of great inter-est to researchers because the re-latedmaterials have been utilized in many applications such as photocatalysis, sensors, batteries, photovoltaics, water splitt-ing, and so forth.1,2 In particular, TiO2 plays a key role as a mediator of electron transport in working electrodes for dye-sensitized solar cells (DSSCs);36 in such cells, dyemolecules are sensitized on the surface of TiO2 films. Photoexcitation of the dye produces an effective charge separation through rapid injection of electrons from the excited state of the dye into the conduction band of TiO2; these injected electrons in TiO2 subsequ-ently migrate toward the electrode, with minimal loss through charge recombina-tion, to generate sufficient photocurrents for the device. An ideal TiO2 film should thus have adequate porosity and a large specific surface area to attain dye loading (DL) to a sufficient extent and for feasible transport of the redox couple of the electrolyte across the network of mesoporous particles.4,5 To fulfill the functionality of such TiO2, the effects of particle size,711 particle shape,1218 film composition,1923 morphology,2432 cry-stalline phase,3335 and peptization condi-tion36 on photovoltaic performance of the device have been investigated. For typical highly efficient DSSCs, the TiO2 films feature a double-layer structure: a scat-tering layer (SL) with a thickness of 25 μm on top of a transparent TiO2 active layer (AL) with a thickness of 1214 μm.59,3740 For an AL, anatase TiO2 nanoparticles of size ∼20 nm exhibit optimal dye adsorption and light harvesting in the visible spectral region; for SL, the size of particles was increased to 200400 nm to enhance the light har-vesting in the wavelength region of 600 800 nm. Although a TiO2 SL advantageously * Address correspondence t