TiO2 nanoparticles embedded in hollow cube with highly exposed {001} facets: Facile synthesis and photovoltaic applications

A hollow anatase titania (HAT) composed of irregularly arranged micro-cube with highly exposed {001} facets was obtained by sintering a TiOF2 solid precursor at 773 K, which was prepared using one-steep hydrothermal reaction of titanium precursor under the mediation of HF and HAc. The synthesized samples were investigated by X-ray powder diffraction (XRD), field emission-scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM). FE-SEM and TEM images indicate that the TiO2 hollow structures with a diameter of 1–2 μm are assembled by cube-like subunits with flat and smooth surfaces. The exposed surface with a thickness of about 100 nm of the TiO2 micro-cube is {001} facet. Inside the micro-cube, some TiO2 particles exist. XRD pattern shows the as-prepared samples are anatase phase. A possible temperature-induced solid-phase oriented rearrangement process is proposed to understand the formation mechanism of the hollow anatase TiO2 structure from the TiOF2 precursor. UV–Vis spectrum demonstrates that the as-prepared samples have high light scattering ability, which is important for the good performance of dye-sensitized solar cells. When used in dye-sensitized solar cells, the device employing the photoanode with two layers of HAT as top scattering layer demonstrates improved short-circuit current density (Jsc) therefore higher energy conversion efficiency (η) of 6.39% in comparison to 4.84% from the cell with P25 photoanode.