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Microscopic observation of dye molecules for solar cells on a titania surface.

Koshiya S, Yamashita S, Kimoto K - Sci Rep (2016)

Bottom Line: A single dye molecule on the titania nanosheet was visualized for the first time.The quantitative STEM images revealed an inhomogeneous dye-molecule distribution at the early stage of its absorption, i.e., the aggregation of the dye molecules.The majority of the titania surface was not covered by dye molecules, suggesting that optimization of the dye molecule distribution could yield further improvement of the DSC conversion efficiencies.

View Article: PubMed Central - PubMed

Affiliation: Surface Physics and Structure Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.

ABSTRACT
The lateral distribution and coverage of Ru-based dye molecules, which are used for dye-sensitized solar cells (DSCs), were directly examined on a titania surface using high-resolution scanning transmission electron microscopy (STEM). The clean surface of a free-standing titania nanosheet was first confirmed with atomic resolution, and then, the nanosheet was used as a substrate. A single dye molecule on the titania nanosheet was visualized for the first time. The quantitative STEM images revealed an inhomogeneous dye-molecule distribution at the early stage of its absorption, i.e., the aggregation of the dye molecules. The majority of the titania surface was not covered by dye molecules, suggesting that optimization of the dye molecule distribution could yield further improvement of the DSC conversion efficiencies.

No MeSH data available.


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Dye molecule distribution on titania nanosheet.(a,b) Experimental ADF image (a) and Fourier filtered image (b) of dye molecules attached on a titania nanosheet. The insets show the Fourier transform patterns. The inset in (b) shows the masked areas to construct the Fourier filtered image. The QADF scales of (a,b) were set to the ranges of 0–0.5% and 0.2–0.5%, respectively. Considering the monolayer titania nanosheet contrast, the ADF scattering cross sections of the open circular areas in (b) were estimated to be 0.0014 ± 0.0004 nm2. These values are consistent with the cross section of one N3 dye molecule (σDye = 0.0011 nm2).
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f3: Dye molecule distribution on titania nanosheet.(a,b) Experimental ADF image (a) and Fourier filtered image (b) of dye molecules attached on a titania nanosheet. The insets show the Fourier transform patterns. The inset in (b) shows the masked areas to construct the Fourier filtered image. The QADF scales of (a,b) were set to the ranges of 0–0.5% and 0.2–0.5%, respectively. Considering the monolayer titania nanosheet contrast, the ADF scattering cross sections of the open circular areas in (b) were estimated to be 0.0014 ± 0.0004 nm2. These values are consistent with the cross section of one N3 dye molecule (σDye = 0.0011 nm2).

Mentions: Figure 3a present a high-resolution ADF image of the dye molecules on a titania nanosheet. The presence of the dye molecules on titania nanosheets was also confirmed by EELS (see Supplementary Fig. S4). As indicated by the open circles, there are several bright peaks whose quantitative contrast is close to 0.8% at the maximum. The inset in Fig. 3a presents the Fourier transform of the ADF image, revealing the spots corresponding to the atomic lattice of the titania nanosheet. To clarify the dye-molecule contrast, all the spots were masked (see the yellow areas in the inset of Fig. 3b), and the inverse Fourier transformed image was calculated, as presented in Fig. 3b. The periodic contrasts of the titania nanosheet are reduced, and the bright peaks (open circles) are easily distinguished. Note that the averaged intensity is not changed by this image processing. We evaluated the ADF scattering cross section of each bright peak area, assuming an averaged intensity of the titania nanosheet of 0.21% (see Fig. 1b). The ADF scattering cross sections of the circular areas were found to be 0.0014 ± 0.0004 nm2. These values are comparable to the cross section of the dye molecule σDye (see Table 1), namely, each circular area contains a single dye molecule. This analysis of the dye-molecule distribution becomes possible for the first time in this study. This procedure visualizes the distribution of dye molecules and, moreover, can be applied to distinguish the type of the attaching molecules.


Microscopic observation of dye molecules for solar cells on a titania surface.

Koshiya S, Yamashita S, Kimoto K - Sci Rep (2016)

Dye molecule distribution on titania nanosheet.(a,b) Experimental ADF image (a) and Fourier filtered image (b) of dye molecules attached on a titania nanosheet. The insets show the Fourier transform patterns. The inset in (b) shows the masked areas to construct the Fourier filtered image. The QADF scales of (a,b) were set to the ranges of 0–0.5% and 0.2–0.5%, respectively. Considering the monolayer titania nanosheet contrast, the ADF scattering cross sections of the open circular areas in (b) were estimated to be 0.0014 ± 0.0004 nm2. These values are consistent with the cross section of one N3 dye molecule (σDye = 0.0011 nm2).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834531&req=5

f3: Dye molecule distribution on titania nanosheet.(a,b) Experimental ADF image (a) and Fourier filtered image (b) of dye molecules attached on a titania nanosheet. The insets show the Fourier transform patterns. The inset in (b) shows the masked areas to construct the Fourier filtered image. The QADF scales of (a,b) were set to the ranges of 0–0.5% and 0.2–0.5%, respectively. Considering the monolayer titania nanosheet contrast, the ADF scattering cross sections of the open circular areas in (b) were estimated to be 0.0014 ± 0.0004 nm2. These values are consistent with the cross section of one N3 dye molecule (σDye = 0.0011 nm2).
Mentions: Figure 3a present a high-resolution ADF image of the dye molecules on a titania nanosheet. The presence of the dye molecules on titania nanosheets was also confirmed by EELS (see Supplementary Fig. S4). As indicated by the open circles, there are several bright peaks whose quantitative contrast is close to 0.8% at the maximum. The inset in Fig. 3a presents the Fourier transform of the ADF image, revealing the spots corresponding to the atomic lattice of the titania nanosheet. To clarify the dye-molecule contrast, all the spots were masked (see the yellow areas in the inset of Fig. 3b), and the inverse Fourier transformed image was calculated, as presented in Fig. 3b. The periodic contrasts of the titania nanosheet are reduced, and the bright peaks (open circles) are easily distinguished. Note that the averaged intensity is not changed by this image processing. We evaluated the ADF scattering cross section of each bright peak area, assuming an averaged intensity of the titania nanosheet of 0.21% (see Fig. 1b). The ADF scattering cross sections of the circular areas were found to be 0.0014 ± 0.0004 nm2. These values are comparable to the cross section of the dye molecule σDye (see Table 1), namely, each circular area contains a single dye molecule. This analysis of the dye-molecule distribution becomes possible for the first time in this study. This procedure visualizes the distribution of dye molecules and, moreover, can be applied to distinguish the type of the attaching molecules.

Bottom Line: A single dye molecule on the titania nanosheet was visualized for the first time.The quantitative STEM images revealed an inhomogeneous dye-molecule distribution at the early stage of its absorption, i.e., the aggregation of the dye molecules.The majority of the titania surface was not covered by dye molecules, suggesting that optimization of the dye molecule distribution could yield further improvement of the DSC conversion efficiencies.

View Article: PubMed Central - PubMed

Affiliation: Surface Physics and Structure Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.

ABSTRACT
The lateral distribution and coverage of Ru-based dye molecules, which are used for dye-sensitized solar cells (DSCs), were directly examined on a titania surface using high-resolution scanning transmission electron microscopy (STEM). The clean surface of a free-standing titania nanosheet was first confirmed with atomic resolution, and then, the nanosheet was used as a substrate. A single dye molecule on the titania nanosheet was visualized for the first time. The quantitative STEM images revealed an inhomogeneous dye-molecule distribution at the early stage of its absorption, i.e., the aggregation of the dye molecules. The majority of the titania surface was not covered by dye molecules, suggesting that optimization of the dye molecule distribution could yield further improvement of the DSC conversion efficiencies.

No MeSH data available.


Related in: MedlinePlus