Preparation And Application Properties Of Photo Anode Materials Based On Monodisperse Nanoparticles

Dye-sensitized solar cells(DSSC)have good development and application potential due to many advantages,such as environmentally friendly,the rich raw materials,facile preparation process,low production cost and relatively high photoelectric conversion efficiency(PCE).The research on photoanodes has always been the focus of DSSC research.Multi-branched TiO2 nanowires array is one of the most promising photoanode materials due to their fast electron transport channels,good light scattering capability and high specific surface area.In addition,because of the exist of local surface plasmon resonance effect of noble metal,using the noble metal nanomaterial to incorporate with TIO2 can greatly improve the absorption and utilization of incident light by the photoanode,thereby improving the PCE of DSSC.This thesis used monodisperse TiO2 nanoparticles as seed crystals to prepare multi-branched TiO2 nanowire photoanode materials.And then they were incorporated with monodisperse silver nanoparticles(Ag NPs)synthesized by high-gravity technology to prepare TiO2/Ag composite materials with excellent photoelectric performance.The research focused on the effects of preparation conditions on the morphology and photoelectric properties of photoanode materials.The main research contents and conclusions are as follows.TiO2 nanowires array photoanode materials with multi-branched structure were prepared by solvothermal method using TiO2 nanoparticles with an average particle size of about 5 nm and monodispersed in toluene as seed crystals.The effect of process conditions on the photoelectric properties of photoanode materials was systematically studied.These process conditions include the concentration of TiO2 toluene dispersion,the ratio of reaction materials ratio and concentration,solvothermal reaction temperature and time,annealing temperature and time,etc.Therefore,the optimal process conditions were determined as follows.The concentration of TiO2 dispersion is 5 wt%,the volume ratio of water/diethylene glycol is 5:15,the concentration of potassium titanium oxalate is 0.05 mol/L,solvothermal reaction temperature is 200℃,and reaction time is 12 h,TiC14 treatment solution concentration is 150 mmol/L,photoanode annealing temperature is 500℃,and annealing time is 30 min.The prepared photoanode material has a multi-branched interpenetrating tree-like structure with a thickness of about 22 μm,a highly crystalline anatase structure and a dye adsorption amount of 128.8 nmol/cm2.The transmission resistance among photoanode/dye/electrolyte interfaces is 61.4 Ω and the PCE of DSSC reaches 9.1%.Compared to the DSSC with TiO2 nanowires array photoanode prepared directly using FTO as seed crystals,its PCE is improved by about 17%.The monodisperse Ag NPs with different particle sizes were controllablely prepared by high-gravity technology.Then they were incorporated with multi-branched TiO2 nanowires by spin-coating method to form the TiO2/Ag composite photoanode materials,and further the DSSC was assembled.The effects of particle size and the amount of addition of Ag NPs on the composite materials and DSSC performance were studied.Thereby the superior composite process conditions were determined.The prepared Ag NPs are spherical-like,with a minimum average particle size of about 8 nm and a narrow particle size distribution.And the particles are uniformly dispersed in n-hexane and have good stability.The Ag NPs are evenly distributed in the photoanode in a form of metallic Ag,which reduces the band gap of the photoanode material and enhances the absorption of visible light by the photoanode,thus significantly improving the photoelectric conversion performance of the DSSC.When the average particle size of Ag NPs is 8 nm and the addition amount is 1.0 wt%,the band gap of photoanode material is reduced from 3.2 eV of pure TiO2 to 3.16 eV,and the short-circuit current density of DSSC is increased from 19.36 mA/cm2 to 24.01 mA/cm2.So the PCE of DSSC can reach 10.0%.Compared with the DSSC with the pure TiO2 nanowires array photoanode prepared directly on the FTO seed crystals,the PCE of DSSC with the TiO2/Ag composite photoanode prepared by using the monodisperse TiO2 particles as the seed crystals is improved by about 28%.