Fabrication and Photoelectric Properties of CdTe/TiO2 Nanocrystals Multilayer

In this paper, we report the fabrication and photoelectric properties of CdTe/TiO2 nanocrystal multilayer. Negatively charged CdTe nanocrystal hydrosols were synthesized in the aqueous phase with 3-mercaptopropionic acid as a surface modifier. The characterization of transmission electron microscopy (TEM) and UV-visible absorption spectrum indicates the resultant CdTe nanocrystal hydrosols are monodisperse and have a very narrow size distribution with a mean diameter of about 5 nm. Clear TiO2 aqueous colloidal nanocrystals with positive surface charges were prepared by using tetrabutyl titanate as precursor. Through the electrostatic interaction between the positive surface charges on TiO2 nanocrystals and those on CdTe nanocrystal hydrosols, multilayer of CdTe/TiO2 nanocrystals were fabricated on the pretreated quartz substrate by layer-by-layer electrostatic self-assembly method. UV-Vis absorption spectrum and atomic force microscopy (AFM) were used to characterize the as-prepared CdTe/TiO2 multilayer. The results show that the surface of the CdTe/TiO2 multilayer are flat and the adsorption intensity in UV-Vis spectrum increases with the layer numbers of the CdTe/TiO2 complex, indicating that CdTe/TiO2 multilayer could be fabricated successfully on the surface of quartz glass and the resultant multilayer have good quality. In the same way, CdTe/TiO2 multilayer were fabricated on the surface of Indium Tin Oxides (ITO) substrate disposed by the poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS). The CdTe/TiO2 complex is measured under AM1.5G simulated solar illumination with 100mWcm(-2) in air. The results show the maximum open circuit current density (Voc) and short circuit current density (Isc) of CdTe/TiO2 complex on ITO substrate is 0.45V and 0.050mA, which were better than TiO2 or CdTe nanocrystal hydrosols individual due to the interfacial hole-electron converter between the adjacent layers of CdTe and TiO2 nanocrystals.