Preparation And Determination Of Photoelectric Properties Of ITO/TiO₂/CPs Electrodes

Conductive polymers, with its special band structure and optical absorption properties,has been applied in the dye sensitized solar cells. Study on the principles of its ensitized nanosemiconductor, not only can help us to understand the generation and transmission process ofthe electrons inside the battery from the molecular level, but also by molecular design for usto seek more efficient, cheap and easy to get a dye sensitizer theoretical guidance, so as toprovide substantial help to solve the energy crisis and environmental pollution. In this thesis,tetrabutyl titanate was used as titanium source, different particle sizes of TiO₂powders wereprepared by sol-gel method at different calcined temperatures. TiO₂nanocrystal wassensitized with PTh, PANI and N719, respectively, to produce a series of solar cell electrodes.（ITO/TiO₂electrode, ITO/TiO₂/PTh electrode, ITO/TiO₂/PANI electrode andITO/TiO₂/PTh/N719composite electrode） Back electrode was prepared by three differentmethods, respectively.Photoelectric properties of the various electrodes were studied, and the battery has beenoptimized with data reference. The results showed that the electrode, prepared with400℃calcining the resulting TiO₂nanoparticles, was higher than the other temperature ITO/TiO₂electrode in the overall performance. Electrode of the pair, the Pt back electrode showed goodphotoelectric properties.The photoelectric conversion efficiency of ITO/TiO₂/PTh electrodewas5.151%; the photoelectric conversion efficiency of ITO/TiO₂/PTh/N719compositeelectrode was up to6.219%. That description compound sensitized can play a role of dualsensitization. But the most significant exaltation was TiO₂in PTh sensitization.ITO/TiO₂/PTh electrodes exist in a p-n heterojunction effectively suppress the reverserecombination of electrons and reduce the loss of the electron.The crystal structure of TiO₂nanoparticles, ITO/TiO₂/PTh electrode, ITO/TiO₂/PANIelectrode was analysised by XRD technique. The results showed that, crystallizationtemperature was relatively low in the prepared sample of TiO₂.The difference crystallineform of TiO₂nanoparticles appeared in the different temperatures. The characteristic peaks ofPANI and PTh was observed in the XRD patterns of the ITO/TiO₂/PANI electrode and theITO/TiO₂/PTh electrodes, respectively, which means that the PANI and PTh are all of adegree of crystallinity.The morphology of TiO₂nanoparticles, ITO/TiO₂/PTh electrode, ITO/TiO₂/PANIelectrode were analysised by using TEM, AFM, SEM. AFM results showed that themorphology of nano-TiO₂prepared by sol-gel method was spherical and agglomerationbetween particles. The particle size of nano TiO₂was about15nm, it was consistent with theXRD results. Observe the AFM images of TiO₂/PANI composite membrane, contrasting with the TiO₂film, we concluded that the coated PANI made the film surface morphology of thegreat changes occurred. The surface of TiO₂/PANI composite film was roughness, pure TiO₂surface voids were filled by PANI in the figure. TiO₂small cubes particles have been evenlywrapped into a relatively large, irregular spherical particles by PANI, the particle diameterwas about35nm. PANI formed in the surface of TiO₂many high hill about50nm, theoriginal flat surface became rough, which will greatly increase the surface area of thecomposite film. Light has to go through multiple reflections can leave the surface the batterylight absorption and utilization will be increased, which is conducive to the conduct of thephotoelectric reaction.SEM results showed that, the sectional thickness of TiO₂films was about2.5μm. Thefilm surface was flat, showing the porous, ane there was similar to the cylindrical voids. Webelieve that the presence of a cylindrical void conducive TiO₂coating for the light absorptionand utilization, is conducive to the sensitizer and the electrolyte and the surface of TiO₂particles, or even within the coating the innermost layer of TiO₂particles in a contact,therebyphotoelectric activity conducive to the of photoelectric chemical reaction occurs, andimprove the battery, so that the photoelectric conversion efficiency of the battery can beimproved.The TiO₂/PTh TEM images showed that PTh prepared with solid-phase method wasneedle-like particles which was different with pure TiO₂morphology. The particle shape ofTiO₂/PTh by the solid-phase method occurs a change, compared to the pure PTh particles,was stubby short rod.UV-Vis absorption spectroscopy was to be used to study the optical properties of the twoconductive polymer sensitized electrode, ITO/TiO₂/PTh electrode and ITO/TiO₂/PANIelectrode. Both UV-visible absorption spectra are observed “blue shift "phenomenon causedby the quantum size effect. Compared to pure TiO₂and pure PANI, TiO₂/PANI compositefilm in the visible region, especially in the visible region between470-780nm, showed a verystrong light absorption; while TiO₂/PTh composite film in the visible region, especiallyperformance in the range of200-600nm TiO₂and pure PTh absorption.In addition, the twoconductive polymer electrode showed the "red shift" phenomenon, which were conducive toimprove the optical performance of the composite membrane. The calculated band gap ofTiO₂/PANI composite film was3.18eV and the TiO₂/PTh band gap energy was2.03eV.Meanwhile, The redox potential of ITO/TiO₂/PTh electrode was determined by usingcyclic voltammetry. The oxidation peak bit of ITO/TiO₂/PTh electrode was1.88V, reductionpeak positions was1.28V. Ground state level is about1.58V （vs. SCE）,1.82V （vs. NHE）.