After the introduction of 15 cycles of CdS deposition, the size of the CdS nanoparticle increased slightly. Importantly, the roughness is about 80 nm, which is higher than that of the ITO/nc-TiO2/CdS(5) film, suggesting that the roughness of the ITO/nc-TiO2/CdS thin film increases with the
cycle number of CdS deposition. TEM was carried out to characterize the detailed microscopic structure of the ITO/nc-TiO2/CdS(5) film. Figure 3a shows the low-resolution TEM image of the ITO/nc-TiO2/CdS(5) film. It can be found that CdS nanoparticles with average diameters of about 10 nm can be distinguished as dark spots, in which TiO2 P25 nanoparticles with average diameters of about Ixazomib in vitro 25 nm can be distinguished as GSI-IX in vivo bright spots. The inset of Figure 3a shows the high-resolution (HR) TEM image of TiO2/CdS(5), in which the lattice spacing of 0.357 nm is assigned to the (100) plane of the hexagonal phase of CdS (JCPDS 80–0006), which is in good agreement with our previous report [22]. Figure 3 TEM images and XRD patterns of the films. (a) TEM images of the ITO/nc-TiO2/CdS(5) film at low and high (inset) magnifications. (b) XRD patterns
of the as-prepared ITO/nc-TiO2 and ITO/nc-TiO2/CdS(10) films. C represents CdS. The large particles are titania Degussa P25 nanoparticles. The small dark spots belong to CdS nanoparticles with diameters of about 10 to15 nm. Figure 3b shows the XRD patterns of the as-prepared ITO/nc-TiO2/CdS(10) (curve 1) and ITO/nc-TiO2 (curve 2) films. By carefully comparing the diffraction peaks in curves 1 and 2, it can be found that the intensities of two peaks at 2θ = 28.3° and 43.9° eltoprazine (corresponding to the (101) and (110) faces of CdS, respectively) in the ITO/nc-TiO2/CdS(10) film are greater than the intensities of those in the plain ITO/nc-TiO2 film, indicating the formation of the hexagonal-phase CdS. To investigate the influence of CdS on the optical properties of the ITO/nc-TiO2 and ITO/nc-TiO2/P3HT:PCBM films, the UV–vis absorption spectra of the ITO/nc-TiO2, ITO/nc-TiO2/CdS(5), ITO/nc-TiO2/P3HT:PCBM, and ITO/nc-TiO2/CdS(10)/P3HT:PCBM films are shown in Figure 4.
It can be seen that compared to that of the ITO/nc-TiO2 film without CdS, the absorbance of the spectra of the ITO/nc-TiO2/CdS(5) film increases largely in the 300- to 950-nm wavelength region, which is similar to that for the CdS nanoparticle-coated TiO2 nanotube film [22, 23]. Apparently, the deposited CdS nanoparticles contribute to the spectral response. Similarly, compared to that of the ITO/nc-TiO2/P3HT:PCBM film, after the introduction of CdS deposition, the light absorption of the ITO/nc-TiO2/CdS(10)/P3HT:PCBM film in the measured wavelength region increased, which is similar to that of CdS/P3HT composite layers [25]. It is known that the optical properties of CdS QD-sensitized TiO2 are directly affected by the size of the CdS QDs due to the quantum size effect [26–28].