Adv. Mater. 2011, 23, 5624–5628 normal incidence of unpolarized light, a broad peak centered at around 430 nm (purple sample in air) was observed, with maximum reflectance of around 60% and additional features at longer wavelengths. The reflectance spectra were strongly affected by the refractive index contrast. For example, when the sample was infiltrated with ethanol, a red-shift of the reflection peak could be observed, compared with that of the sample in air. When the refractive index contrast was further lowered by infiltration with the liquid electrolyte (the hole-transporting medium of DSSCs), the reflection peak of the PC layer shifted to an even longer wavelength which was close to one of the absorption peaks (∼ 500 nm) of the N719 dye. Numerical simulations were conducted on the TiO 2 PC layer and the simulated reflectance spectra agreed well with the experimental results in terms of peak position (Figure 3 and Figure S5, Supporting Information). The secondary oscillating feature in the simulated spectra was not experimentally observed because of microstructure imperfections. Moreover, the intensity of the Bragg