Preparation Of Thin Films Of CdSe Nano Semiconductors And Their Photoelectro Chemical Properties

Cd Se is an n-type semiconductor with a narrow direct-transition band gap（¹.76 eV）. It can absorb visible light effectively and has great applicable potential in electronic, optoelectronic, photoelectrochemical（PEC） solar cells, PEC detection, photocatalyst, and gas sonsor, etc. In this thesis, we prepared several thin films of Cd Se nanoparticles by electrochemistry, gas/liquid interface reactions and self-assembly, and solution soaking. We characterized these films and studied their PEC perfromances. The main research contents are as follows:（1） A smooth Cd electrode was first anodized in a 0.2 M KNO₃ aqueous solution at- 0.9 V（vs. Hg|Hg2SO4（s）|K2SO4（saturated）） into layered porous structures covered with Cd（OH）₂ precipitation, and the Cd（OH）₂ deposits on the Cd anode was then selenized in a 0.2 M Na2SeSO3 aqueous solution. The produced CdSe nanoparticles self-assembled into strawberry-like nano-aggregates. The anodization time and selenization time were optimized separately. XRD and Raman spectra confirmed the formation of Cd（OH）₂ and CdSe thin films under our experimental conditions. The PEC performances of CdSe films prepared by varying the applied potentials, polarization time and selenization time were investigated and discussed.（2） Thin films of CdSe nanoparticles were fabricated at gas/liquid interface by contacting a CdCl2 solution containing a surfactant of sodium dodecyl sulfate（SDS） with the H2 Se vapor in a desiccator for some time.CdSe nanoparticles were produced through reaction between Cd2+ and Se2-. These nanoparticles formed a uniform and compact thin film under the action of surface pressure from SDS. Then the CdSe films floating on the solution’s surface were transfered noto a conductive glass substrateand calcined in a Muffle furnace to improve the crystallinity of CdSe.XRD and Raman spectra confirmed the formation of CdSe thin films under our experimental conditions. The PEC performances of CdSe prepared by varying the assembly time were investigated and discussed.（3） CdSe thin films of red nanoparticles were obtained by immersing the smooth Cd electrode into Na2SeSO3 solution for several hours. The Cd surface can be oxidized easily in wet air and O2-containing solution into Cd O and/or Cd（OH）₂, and Se2-can be produced from Na2SeSO3 solution. Therefore, Cd Se thin films can be obtained on the surface of Cd electrodes. XRD and Raman spectra confirmed the formation of CdSe thin films in this way. The PEC performances of CdSe thin films prepared by varying the soaking time were investigated and discussed.