Comparing Figure 2a, b, the compressed film is homogeneous and smooth which may enhance the electron transport between NPs. Although the compressed film is smooth, there is still a porous Mocetinostat structure, as shown in the inset of Figure 2b, which enhances the following dye absorption. The cross-sectional FESEM image of the TiO2 NP thin film prepared by doctor blading method with the

compression process is shown in Figure 2c. The result indicates that the compressed film is also condensing in the plane-normal Savolitinib nmr direction. Figure 2 FESEM images of TiO 2 nanoparticle thin film on FTO glass fabricated by doctor blading method. (a, b) The top-view images of the as-deposited and the compressed film, respectively. (c) The cross-sectional image. The insets in (a) and (b) are high-magnification images. In order to reveal the effect of dyes adsorbed on the TiO2 NPs, a compressed TiO2 NP thin film with a thickness that is the same as that of sample D (26.6 μm) but without dye adsorption was prepared. Its UV–vis adsorption spectrum was compared with those of samples A to F, as shown in Figure 3. The range of spectral absorbance learn more was between

0 and 6 which is related to air, to which 0 absorbance was assigned. The absorbance of the films with dye adsorption (samples A to F) is larger than that of the films without dye adsorption. The absorbance increases as the thickness

increases which may be attributed to the increase of the number of absorbed dye molecules in the TiO2 NP thin film. In the short light wavelength region (less than 590 nm), the absorbance is almost the same among samples B to F whose thickness is greater than or equal to 14.2 nm, as shown in the inset of Figure 3. It is because the adsorption characteristic of N3 dye is located at the light wavelength of 6-phosphogluconolactonase 540 nm. On the other hand, in the long light wavelength region, the absorbance increases as the thickness increases. The result is shown in the inset of Figure 3 by comparison of the absorbance of samples B to F at 650 nm. It is because long-wavelength light has high transmittance resulting in high absorbance for the thick film. Figure 3 The UV–vis absorption spectra of compressed TiO 2 NP thin films with various thicknesses. Samples A to F have a photoanode thickness of 12.7, 14.2, 25.0, 26.6, 35.3, and 55.2 μm, respectively, with dye adsorption. Sample D’ is the TiO2 NP thin film of 26.6 μm in thickness (the same as sample D) but without dye adsorption. To further understand the electron transport processes in the DSSCs made of TiO2 photoanodes, the EIS spectrum was analyzed. Figure 4 shows the Nyquist plots, minus the imaginary part of the impedance -Z” as a function of the real part of the impedance Z’ while the frequency sweeps from 10 mHz to 100 kHz, of samples A to F.