Preparation Of Ag-loaded TiO₂ Nanotube Composites And Their Applications In DSSCs

Energy is the foundation of modern social and economic development.Mastering the new energy technology is the driving force of the future society..Solar energy is a clean energy.The utilization of solar energy conforms to the trend of sustainable development of human society Dye-sensitized solar cells(DSSCs)are photovoltaic devices that use solar energy to generate electricity,and therefore have attracted the attention of researchers all over the world.The most widely used materials for dye-sensitized solar cell photoanode are TiO2 and ZnO.Anatase TiO2 is a direct bandgap semiconductor material,which can only absorb the short wavelength ultraviolet light.Moreover,the recombination rate of photogenerated electron and hole in TiO2 is higher.So,the utilization efficiency of sunlight is low.The photo-electric transfer efficiency of DSSCs using pure TiO2 film photoanode is reduced.ZnO is also a direct wide bandgap semiconductor material,which is one of the most widely used semiconductor materials in the field of photocatalysis.Recently,more researchers have investigated the application of ZnO on dye-sensitized solar cells for its simple preparation method and various morphologies.Graphene is a light-transmitting material with zero band gap structure,high electron mobility and excellent electrical properties.It has attracted the more attention of DSSCs researchers.The graphene-semiconductor composite is not only beneficial to improve the light absorption of the semiconductor material,but also to promote the interfacial charge separation and reduce the photogenerated electron and hole recombination rate.Precious metals can cause surface plasmon resonance effects,so the combination of precious metals and semiconductor materials can enhance the light absorption and utilization of the wide-bandgap semiconductor photoanode.In addition,the good electron conductivity of the noble metal is also beneficial to reduce the resistance of the battery.In this thesis,we studied the effect of TiO2 nanotubes loaded Ag composites on the photoelectric performance of the DSSCs by controlling the morphology of TiO2.At the same time,we also discussed the effects of different substrate materials on the performance of the solar cell device.The specific content of the study is as follows:(1)Tetrabutyl titanate was used as the titanium source to synthesize TiO2 nanotubes(TNTs)by sol-gel/hydrothermal method.The effects of different pH values of rinsing solution and annealing temperatures on TNTs were investigated.The results showed that the crystalline anatase TNTs can be obtained after rinsing by pH=5 acid solution and annealing at 400 ?.The Ag-TNTs-xH composites were prepared by photodeposition.The experimental results showed that Ag loading could increase the light absorption of the materials and improve the surface structure of TNTs.The double-layer photoanode dye-sensitized battery was prepared by the doctor-blade method.The photoelectric performance of the solar cell was studied by electrochemical workstation and solar cell quantum efficiency system.The results show that the photoelectric conversion efficiency of the photoanode with Ag-loaded TNTs can reach the maximum of 7.2%,which is more than two times higher than that of Ag loaded-free solar cells.(2)The TNTs@GO composite was synthesized by hydrothermal method,and Ag was loaded on the surface of TNTs@GO by photodeposition.The infrared and Raman were used to prove that GO was reduced during hydrothermal process.After the Ag was loaded by photodeposition,it was found that GO was further reduced,indicating that GO can remove the oxygen-containing functional groups at the edge of the graphene oxide under ultraviolet irradiation.When investigating the graphene loading amount,we found that excessive loading of graphene accelerated the electron back-reaction and reduced the current density.The final experimental results show that the Ag-TNTs@GO-8H has the highest current density and the photoelectric efficiency of 5.76%.(3)TiO2 nanotubes were prepared by three different titanium sources,and the effects of annealing on TiO2 nanotubes under different atmospheres were investigated.Based on the experimental results,Ag-TNTs were synthesized using P25 as the titanium source.At the same time,ZnO conductive substrates wee also fabricated using three different zinc sources.After testing the photoelectric properties of anode films prepared from three different zinc sources,It was found that ZnO film prepared by Zn(ZO3)2 has the best photoelectric performance.The SEM results indicated that the ZnO nanorods array prepared by Zn(ZO3)2 has a smaller size and closed contact with the FTO conductive glass to facilitate charge transport.After loading Ag,it was found that the photoelectric performance of the cell increased significantly,which is the same as the results of the previous two chapters.The photoelectric performance of the cell fabricated with 8H deposition composite reached 2.462%,.It shows that the influence of Ag on the photoelectric performance of the battery is regular.