Structural and optoelectronic properties of hybrid bulk-heterojunction
materials based on conjugated small molecules and mesostructured TiO2
Hung Phan,a Justin P. Jahnkeb, Bradley F. Chmelkab, Thuc-Quyen Nguyen*a
aDepartment
of Chemistry and Biochemistry, bDepartment of Chemical Engineering, University of California, Santa Barbara, California
93106, Unites States. Email: quyen@chem.ucsb.edu.
SUPPLEMENTAL MATERIALS
Figure S1. Nitrogen absorption (circles) and desorption (triangles) isotherms of mesostructured TiO2
film, measured using a TriStar 3000 Micrometritics Gas Absorption Analyzer.
Loading calculation of absorption method
A series of neat DPP(TBFu)2 films at different thicknesses were prepared by spin-coating DPP(TBFu)2
solutions at different concentration on glass substrate. The absorbance of these films at 600 nm
(maximum absorption wavelength) was plotted against their thicknesses to get a calibration curve,
presented in Figure S2. The relative thickness of DPP(TBFu)2 in hybrid TiO2-DPP(BTFu)2 films was
extrapolated by fitting its absorbance at 600 nm to the calibration curve. The average relative thickness
of DPP(TBFu)2 was 43.9 nm. The average thickness of hybrid film was 400 nm, with its void volume
having an equivalent thickness of 400 nm × 0.43 (void fraction) = 172 nm. The loading is (43.9/172) ×
100=25% of the pore volume.
1
0.9
0.8
Absorbance
0.7
0.6
0.5
0.4
0.3
0.2
0
15
30
45
60
75
Film thickness (nm)
90
Figure S2. Calibration curve of absorbance at 600 nm at different thicknesses of neat DPP(TBFu)2
films.
Loading calculation by SIMS method
Figure S3. SIMS traces of hybrid TiO2-DPP(TBFu)2 drop-cast film.
In this method, we drop-casted the small molecule solution on mesostructured TiO2 films and
characterized it by SIMS. Drop-casting results in a neat small molecule layer formed on top of hybrid
layer. The
12
C intensity is much higher than
64
TiO for the top surface which comprises of mostly
DPP(TBFu)2 (Figure S3). As it reaches to the interface of the hybrid layer, 12C intensity drops and 64TiO
intensity enhances significantly. The 12C signal from the hybrid layer is 12% of its signal from neat top
layer. By assuming the etching rate among different elements is similar, we conclude that DPP(TBFu)2
comprised of 12 vol. % of the hybrid film, corresponding to an overall loading of approximately 29% of
the total TiO2 pore volume (=12/0.43, the void fraction of the mesostructured TiO2 film).
2
Figure S4. Absorption spectra of neat DPP(TBFu)2 and hybrid TiO2-DPP(TBFu)2.
3