Fabrication and Photoelectric Properties of CdTe/TiO_2 Nanocrystals Multilayer

摘要

In this paper, we report the fabrication and photoelectric properties of CdTe/TiO_2 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 TiO_2 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 TiO_2 nanocrystals and those on CdTe nanocrystal hydrosols, multilayer of CdTe/TiO_2 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/TiO_2 multilayer. The results show that the surface of the CdTe/TiO_2 multilayer are flat and the adsorption intensity in UV-Vis spectrum increases with the layer numbers of the CdTe/TiO_2 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/TiO_2 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/TiO_2 complex is measured under AM1.5G simulated solar illumination with 100 mWcm~(-2) in air. The results show the maximum open circuit current density (V_(oc)) and short circuit current density (I_(sc)) of CdTe/TiO_2 complex on ITO substrate is 0.45 V and 0.050 mA, which were better than TiO_2 or CdTe nanocrystal hydrosols individual due to the interfacial hole-electron converter between the adjacent layers of CdTe and TiO_2 nanocrystals.