1. Interfacial structure of dye solar cells under redox electrolyte.
J. McCree-Grey, J.M. Cole, S.A. Holt, P.J. Evans and Y. Gong

2. Dye Sensitised Solar Cells
Metal-centred complexes face issues
Environmental regulations
Scarcity / cost of metal centres
Organic Dyes
Cheaper and more flexible synthesis
Low cost efficient environmentally friendly power generation
Transparent, good in diffuse light conditions
 Smart window applications
Dye interactions at molecular level ?
Niche prospects - electricity generating windows
Greater molecular design flexibility

3. Background Highlight XRR and NR results.
Supported by UV/Vis and DFT calculations.
Full details can be found at
McCree-Grey et al. Nanoscale, 2017, 9, 11793
DOI: /c7nr03936k

4. Preferred TiO2 binding modes
Molecular Structures
MK-2
MK-44
0.3 mM solution of Dye in 1:1:1 acetonitrile : tert-butanol : toluene
Preferred TiO2 binding modes

5. Reflectivity Structure perpendicular to interface
X-rays
Sensitised TiO2
Silicon
Structure perpendicular to interface
Neutrons travel ‘through’ the silicon substrate
Buried interface
X-rays through air

6. MK-44 on TiO2
MK-2
Thickness 23.3
Mass density 1.11
XRR data at four different locations on substrate 9.6 Å thick. Mass density 1.09 g/cm3

7. Surface attachment by XRR
MK-2
MK-44
Models were created using ChemBio3D (Perkin Elmer)

8. Lithium (yellow) Iodide (pink)
Schematic illustration of the dye sensitised TiO2 sample within the solid-liquid environment
iodide:tri-iodide
neat d3-MeCN
iodide:tri-iodide is the (pink, tri-atomic structure) in d3-MeCN formed upon addition of I2 to the previously stated LiI solution
Lithium (yellow) Iodide (pink)
in d3-MeCN

9. Schematic illustration of the dye sensitised TiO2 sample within the solid-liquid environment
iodide:tri-iodide is the (pink, tri-atomic structure) in d3-MeCN formed upon addition of I2 to the previously stated LiI solution

10. MK MK44
Figure 5 Reflectivity profiles for (a) MK-2 and (b) MK-44 dyes sensitised on an amorphous TiO2 thin-film and submerged within solution 1 (d3-MeCN, red), 2 (d3-MeCN + LiI, orange), or 3 (d3-MeCN + LiI + I2, green). The thin overlaid lines represent the co-refined models fitted to their corresponding datasets. Corresponding SLD profiles are presented as Figure insets

11. MK-44 SLD profile

12. Dye Layer
TiO2 Layer
Solution
Dye
t /Å
SLD (x10-6) /Å-2
R / Å
R /Å
MK-2 1
23.6±1.9
1.9±0.1
6.0
108.6±2.1
2.1
3.5
4.60 2
23.8±1.9
2.5±0.1
4.74 3
22.2±1.5
2.4±0.1
4.86
MK-44
9.2 ±0.7
2.9 ±0.6
4.0
107.6 ±2.3
4.51
15.9 ±1.0
3.6 ±0.4
4.67
3.8 ±0.4

13. Dye Layer
Dye
Solution
t /Å
SLD (x10-6) /Å-2
MK-2 1
23.6±1.9
1.9±0.1 2
23.8±1.9
2.5±0.1 3
22.2±1.5
2.4±0.1
MK-44
9.2 ±0.7
2.9 ±0.6
15.9 ±1.0
3.6 ±0.4
3.8 ±0.4

14. Change in MK-44 surface attachment
Figure 6 Molecular structure of MK-44 with bidentate bridging geometry adopted in the presence of Li+ ions, indicating the dmax (15.74 Å) and molecular width (7.74 Å). The red shaded boxes indicate sections of the TiO2 surface which are potentially exposed to solvent/electrolyte upon the change in dye geometry.

15. Conclusions Suggest that initial surface arrangement is crucial
Possible mechanism contributing to lower efficiency of MK-44
First application of NR to DSCs.
In situ experiments in simple model of DSC cell.