Preparation And Application Of TiO₂ Microspheres In The Dye-sensitized Solar Cells

Dye-sensitized solar cells?DSSCs?have been regarded as one of the most promising devices for solar-to-electricity energy conversion due to their extraordinary efficiency,low fabrication cost and ease of fabrication.The traditional photoanode made of TiO₂ nanoparticles with a diameter of 10-30 nm exhibited a weak light-scattering ability.Worse still,the traditional nanoparticles photoanode could not always give the best performance due to the added grain boundaries and defects on the particle surfaces,which could delay electron transport.A possible solution is to construct a double-layered photoanode made of a nanocrystalline TiO₂ film as transparent active layer and relatively large TiO₂ particles;Another versatile strategy to improve the transport and collection of electrons is the use of 1D nanostructures,such as nanorods,nanowirs and nanotubes,which are able to provide vectorial pathway for fast electron transport along the axial direction for rapid collection of photogenerated electrons.However,TiO₂ arrays of 1D nanostructures did not show a significant enhancement of PCE of DSSCs because of low internal surface area ascribed to nanorods,nanowires or nanotubes with a larger diameter and a wider distance between neighbour nanorods or nanowires.In view of this bottleneck,surface-modified method like introducing branches or light-scattering layer on 1D nanostructures was developed.In this paper,from the two solutions,the mesoporous TiO₂ microspheres used as the light scattering layer were prepared respectively.The surface modification of the 1D nanotubes was carried out by the method of chemical bath deposition.The nanofibers were prepared by hydrothermal method the hierarchical petaloid TiO₂ microspheres.1.Three-dimensional and thermally stable mesoporous TiO₂ submicrospheres are synthesized without the use of any surfactants via treatment with high intensity ultrasound irradiation for a short period of time.Techniques of X-ray diffraction,field emission scanning electron microscopy,nitrogen adsorption-desorption,and UV–vis spectrum are used to characterize the structure and morphology of the product.The specific surface area of the mesoporous TiO₂ submicrospheres is calculated to be 53 cm2g-1.The UV-Vis spectrum shows that the mesoporous TiO₂ submicrospheres have high light-scattering ability and light absorption by dye.In addition,when applied as the light-scattering layer in dye-sensitized solar cell,an overall photovoltaic conversion efficiency of 7.92% has been achieved.2.We have proposed a novel engineered multifunctional photoanode which consists of one-dimensional?1D?TiO₂ nanotube arrays modified by TiO₂ nanoparticles as a bottom layer and three-dimensional?3D?TiO₂ submicrospheres as a top layer by a simple one-time chemical bath deposition method.This 1D-3D bilayer photoanode simultaneously possesses the incompatible features such as high specific surface area,pronounced light-scattering ability,and fast electron transport.The novel 1D-3D bilayer photoanode demonstrates a power conversion efficiency?PCE?of 6.93%,leading to a 26.5% increment of PCE compared with that of TiO₂ bare nanotube arrays?5.48%?.3.The petaloid TiO₂ submicron sphere composed of nanosheets and submicron spheres was synthesized by simple hydrothermal synthesis.The TiO₂ microspheres obtained by hydrothermal method and annealed have good crystallinity and high stability of anatase and show excellent light scattering ability.In order to study its applicability in DSSC,we use this structure as a light scattering layer,assembled into a battery,to characterize the conversion efficiency of 7.36%,exceeding the conversion efficiency of commercial P25?6.14%?under the same conditions of 19.9 %.