Photoelectrochemical Study On Conducting Polymers Modified Composite Sulfides Quantum Dots Anchored Nanostructured TiO₂

In this dissertation, the CdS, Q-PbS quantum dots were formed in situ on the nanocrystalline TiO₂ electrode using chemical bath deposition techniques and the poly(3-Methylthiophene)(PmeT) was prepared with electrochemical method on TiO₂/(Q-CdS, Q-PbS) film. The photoelectrochemical properties of PMeT modified Q-CdS, Q-PbS anchored nanostmctured TiO₂ film were studied. The experiment results showed as follows:1)The photon-current conversion properties of nanostmctured TiO₂/Q-PbS film electrode were studied by using the photocurrent action spectra and the photocurrent dependence of potential. Because of quantum size effect, the particle size of Q-PbS which was prepared by dipping with different time in saturated Pb(CH₃COO)₂ solution was different, the bandgap of Q-PbS film was reduced along with prolongation of dipping time._The bandgap of Q-PbS particles was 1.68 eV which was prepared at the drying temperature of 80℃and the immersion time of 40 s. The diagram of energy level of Q-PbS film was determined with the photocurrent-potential curves and photoelect-rochemical method. The conduction band of Q-PbS film was -5.538 eV. The nanostructured TiO₂/Q-PbS film electrode could enlarge the visible optical absorption region and obviously increase the photocurrent in visible region. The photon-electron conversion efficiency could be improved.2)The photon-current conversion properties of nanostructured TiO₂/Q-CdS film electrode were studied by using the photocurrent action spectra and the photocurrent dependence of potential. Because of quantum size effect, the bandgap of Q-CdS particles was widened to 2.51 eV which was prepared at the drying temperature of 80℃and the immersion time of 60 s. The diagram of energy level of Q-CdS film was determined with the photocurrent-potential curves and photoelectrochemical method. The conduction band of Q-CdS film was—6.168 eV (vs Vaccum). The nanostructured TiO₂/Q-CdS film electrode could enlarge absorption region and obviously increase the photocurrent. The photon-electron conversion efficiency could be improved.3)The photoelectrochemical properties of TiO₂/Q-PbS film and poly(3-Methy-lthiophere)(PMeT) modified Q-PbS anchored nanostructured TiO₂ film were studied by using the photocurrent action spectra and the photocurrent dependence of potential. The bandgap of Q-PbS films was 1.68 eV. The energy level of Q-PbS film was determined with photoelectroehemieal method. The results showed that PMeT and Q-PbS respectively modified TiO₂ film and PMeT modified Q-PbS anchored nanostructured TiO₂ film produced photoeurrent in the longer wavelength region under certain condition. In infrared light region, the conversion efficiency of light to electricity for the composite semiconductor nanoporous films was greatly improved comparing with that of the nanostructured TiO₂. The experiment result showed that the p-n heterojunetion existed in the nanostructure TiO₂/Q-PbS/PMeT film electrode, which redounded to the separation of electron/hole pairs generated by photoexcitation, thus photoelectric conversion performance was improved.4)The photoelectrochemical properties of poly(3-Methylthiophene)(PMeT) modified Q-CdS anchored nanostructured TiO₂ film were studied. The results showed PMeT and Q-CdS respectively modified TiO₂ film and PMeT modified Q-CdS anchored nanostructured TiO₂ film produced photocurrent in the longer wavelength region. In infrared light region, the conversion efficiency of light to electricity for the composite semiconductor nanoporous films was greatly improved when it was compared with nanostructured TiO₂. The experiment result showed that the p-n heterojuction existed in the nanostrueture TiO₂/Q-CdS/PMeT film electrode, which favored the separation of electron/hole pairs generated by photoexcitation.5)The photoelectrochemical properties of poly(3-Methylthiophene)(PMeT) modified Q-CdS, Q-PbS anchored nanostructured TiO₂ film were studied. The results showed PMeT and Q-CdS, Q-PbS respectively modified TiO₂ film and PMeT modified Q-CdS, Q-PbS anchored nanostructured TiO₂ film produced photocurrent in the longer wavelength region under certain condition. In infrared light region, the conversion efficiency of light to electricity for the composite semiconductor nanoporous films was greatly improved comparing to that of the nanostructured TiO₂. The experiment result showed that the p-n heterojunction existed in the nanostructure TiO₂/(Q-CdS, Q-PbS)/PMeT film electrode, which favored the separation of electron/hole pairs generated by photoexcitation. It cound be seen that the maximum value of incident photon to current conversion of efficiency(IPCE) for PMeT modified Q-CdS, Q-PbS anchored nanostructure TiO₂ film respectively was 11% and 7%.