Preparation Of Hierarchy TiO₂ Photoanode And Applications In Dye-sensitized Solar Cells

As a type of third-generation solar cell,dye-sensitized solar cell?DSSC?has great prospect due to the simple fabrication,low cost,and environmental-friendly properties.Until now,the highest recorded photoelectric efficiency up to 14.7% has been reported in DSSCs.Photoelectric conversion efficiency act as the most important parameter to evaluate the performance of cells.There are three factors influence the photoelectric conversion efficiency: light harvesting efficiency,electron injection efficiency and charge collection efficiency.Among them,the light harvesting efficiency is mainly related to the photoanode materials and dye sensitizers.The photoanode plays the important role in the DSSCs.Generally,nanocrystalline with high specific surface area is regarded as the most popular DSSCs photoanode material for its large dye-loading amount,thereby improving the photoelectric conversion efficiency of the cell.The size and morphology of TiO₂ nanomaterials have a great impact on DSSCs.TiO₂ nanoparticles with high specific surface area have been used in most popular DSSCs,however,the photoanode films composed of these TiO₂ particles show low light scattering capability for small particle size,thus leading to a poor light-harvesting efficiency.Therefore,large-scale TiO₂ nanomaterials with hierarchical structure are prepared as photoanode material with enhanced photoelectric performance by improving the light scattering capability of the photoanode film.In this work,three-dimensional?3D?hierarchical microspheres constructed with branched rutile TiO₂ nanorods?BMS?and TiO₂ nanoparticles decorated microspheres?NP-MS?have been successfully synthesized with two-step solvothermal methods.Meanwhile,a series of structural tests and characterizations are applied.These results show that the crystal phase of BMS is identified as tetragonal rutile phase.BMS with uniform size about 2 ?m and the length of branches about 21-24 nm.It is speculated that the branches grow vertically on the trunk nanorods.The crystal phase of NP-MS is identified as the typical anatase and rutile phase.The size of NP-MS is about 2.3 ?m.There are many nanoparticles compactly grown in the nanorodsand and the nanoparticles are filling on the top of the nanorods.These synthesized materials are applied as the photoanode material of DSSCs to investigate the corresponding photoelectric properties.The branched nanorod structure of BMS accelerates electron transport.At the weight ratio of 20% BMS embedded into P25 layer,the optimal conversion efficiency of DSSCs reached 6.66%.Similarly,NP-MS with the advantages of increased specific surface area,enhanced light scattering capability and improved electron transport,could greatly enhanced the light-harvesting efficiency and photoelectron generation/separation efficiency.The optimal photoelectric efficiency of pure NP-MS reached 6.68 %.