This strong visible light reflection is also supported by the pic-tures (Fig. S1 (b) and (c)). The TiO2 coatings made of paste-3 shows the lowest light reflection and is semi-transparent (Fig. S1(a)),as compared to that made of paste-1, paste-2, and paste-4. The nanoparticle coating has high light transmittance, but it was used as the dye-adsorbing layer in present research as it is composed of tiny nanoparticles (ca. 8 nm) with high specific surface area (85 m2g−1) and suitable pore size.