TiO <sub> 2 </ Sub> Electrode Controlled Deposition Heterojunction Photoelectric Conversion Performance

Inorganic semiconductor material, especially nanostructure semiconductor withthe properties of light, electricity and catalysis, appears to be a promising technologythat has a number of applications such as photocatalysis, photoelectron conversion,sensor and molecule-device. And it has become a hotspot in research of materialsscience. The technology of semiconductor photocatalysis and photoelectron conversionwill become the best way to solve the crisis of energy sources and the problem ofenvironment pollution in exploring the solar energy. The keys of how to restrain therecombination of the photoexcited electron-hole pair and improve the utilization ratioof solar energy in the research were found by people.In this paper, we used electrodeposition method to carry our controllabledeposition CdS nanometer films on ITO/TiO₂ film substrates. The samples weremeasured by EDS,XRD,N₂ absorption-desorption,SPS,SEM,Fluorescence,Photoelectric testing system,Impedance spectrum. We in detail discussed the pHvalues,deposition times,deposition potentials of deposition system about the controlof electrodeposition of TiO₂-CdS heterojunction, and researched the photoelectric andphotocatalytic capability of TiO₂-CdS heterojunction.The results showed that ITO/TiO₂ film prepared by dip-coating method hascumulate holes structure, and aperture distribute from 3.8 nm to 4.7 nm. WithITO/TiO₂ film as substrate, 0.1 M CdCl₂ solution and 0.01 M Na₂S₂O₃ acted as Cd andS deposition sources, respectively. We could gain CdS film with 1:1 ratio of Cd/SWhen electrolyte pH was 1.5 and deposition potential was-1.0 V. Single CdS gaindiameter of about 13 nm. CdS crystal prepared by electrodeposition had mainlyhexagonal phase and mixed a little cubic phase, and on (002) crystal plane CdS crystalgrew epitaxially along c-axis of substrate. Although CdS crystal was not past throughtemperature disposal, crystal degree was still quite high. Through SEM and SPS measurements, we found that CdS deposited firstly inholes formed by three layers TiO₂ accumulation, when holes were filled with CdSparticles, CdS continued to deposit on film surface with TiO₂ particle acted as growthdot. CdS deposited in holes and TiO₂ formed heterojunction.Through fluorescence spectrum and photocurrent action spectrum measurements,we found that fluorescence signal of CdS weakened after TiO₂ film was deposited CdSby electrodeposition, and accordingly improved photoelectric capability of TiO₂ filmand achieved sensitization action. By changing electrodeposition conductions ofdeposition times and deposition potential, we could control the deposition quantity ofCdS film, the change of composition and the grain diameter of CdS particles.Photoelectric catalysis data indicated that addition of static field appeared toseparate action of photogenerated carrier. The potential was very high, separate effectof photogenerated carrier was also better. But if addition of static field was overhigh,RhB would directly take place electric oxidation, ITO/TiO₂/CdS composite films justacted as a conductive electrode with very large resistance, so the degradation rate ofITO/TiO₂/CdS composite films to RhB reduced instead.