Preparation Of Noble Metal Loaded TiO₂ Composite And Its Application In DSSCs

Due to the demand for energy in the development of human society and economy,the global energy consumption is increasing exponentially,and the supply of fossil energy cannot meet the demand in a sustainable way.In addition,some toxic gases released into the atmosphere by burning fossil fuels,such as carbon dioxide,sulfur dioxide and nitrous oxide etc,are the main factors causing environmental pollution.The utilization of solar energy in renewable energy has become one of the research directions,among which dye-sensitized solar cells(DSSC)have become the research hotspot of photovoltaic devices.Compared with other solar cells,DSSC has the advantages of low cost,easy assembly and low toxicity,and has great potential for development.In this paper,different functionalized TiO₂scattering materials were prepared by morphology control and precious metal loading methods,and introduced into the photoanode of DSSC to improve the performance of DSSC.The effects of different scattering materials on the optical properties,electrical properties and interface impedance of the electrode were investigated.Specific research contents are as follows:(1)SiO₂@TiO₂(ST)and Ag-loaded ST(STA)scattering nanospheres were synthesized by hydrothermal reaction.The prepared ST and STA microspheres samples were mixed into P25 respectively to fabricate two kinds of composite photoanodes.The added ST microspheres can increase the reflectivity of the photoanode in the visible region by the scattering effect.When 33 wt%ST microspheres sample was added,the maximum Jsc was increased to 13.4 mA cm^-2,but excessive added ST will reduce the amount of adsorbed dye,and the increase of impedance was not conducive to the electron transfer process.The STA sample loaded with Ag nanoparticles can increase the visible light absorption of the photoanode through the LSPR effect and promote the separation of photogenerated electron hole pairs.When 2 wt%STA is added into photoelectrode,the Jsc increased to 15.97 mA cm^-2and the?reaches 7.3%,which is significantly higher than that of DSSC with pure P25 photoelectrode.Impedance analysis showed that the interfacial transfer impedance of the 2 wt%STA electrode reached the minimum value of 35.71?,and the electron lifetime was 15.9 ms,while the electron lifetime of the pure P25 electrode DSSCs was 7.4 ms.(2)Urchin-like TiO₂(UT)and carbon nanofibers embedded titanium dioxide,CNF@TiO₂(CT)microspheres formed by hydrothermal synthesis method.The layered microstructure meets both the requirements of increasing specific surface area and improving light capture performance.The specific surface area of CT composite is as high as 222 m²/g.The maximum Jsc of DSSCs prepared by CT-3 was 11.28 mA cm^-2.The CTA composite material prepared by loading Au nanoparticles(Au-NPs)on the surface of CT had LSPR effect.The composite photoanode was formed by mixing CTA and CT-3 powder.The results show that the LSPR effect of Au-NPs could significantly improve the photovoltaic performance of DSSC devices.When the doping amount of CTA in the electrode material is 1 wt%,the highest Jsc and?values of the DSSC are 15.97 mA cm^-2and 8.4%,respectively.AC impedance analysis showed that the interface transfer impedance of the electrode was the minimum of38.04?,and the electron lifetime was the maximum of 23.3 ms,indicating that Au-NPs could inhibit the recombination of charge,but excessive Au-NP would also act as the recombination center of photogenerated electrons,resulting in the reduction of photoelectric conversion efficiency.(3)TiO₂/SnO₂(TS)scattering microspheres,TiO₂and SnO₂hollow spheres were successfully synthesized by hydrothermal reaction.The maximum specific surface area of TS-2 microspheres was 97.3 m²/g.When TS-2 scattering microspheres were prepared into photoanode,the corresponding Jsc and?of the DSSC cells were 14.96mA cm^-2and 8.1%,respectively.Compared with the hollow TiO₂spheres,the Jsc and?values increased by 23.8%and 39.7%,respectively.The performance of solar cells is enhanced because the high electron mobility of SnO₂,which can promote electron transfer and inhibit charge recombination,and the high specific surface area of the scatterers is helpful to improve the performance of DSSC.SnO₂itself has a wider band gap than TiO₂,which can also effectively inhibit the generation of holes in valence bands and reduce the recombination of electron holes.However,due to the weak photon capture rate and low dye adsorption capacity of SnO₂,the performance of solar cells decreases with the further increase of excessive SnO₂content in electrode materials.