Fluorine doped tin oxide coated glass

Mesoporous ATO nanoparticle layers were prepared on fluorine-doped tin oxide coated glass (∼7 Ω sq⁻¹, Sigma Aldrich) by the doctor blade method. Prior to doctor blading, the substrates were cleaned by repeated ultrasonication in water and acetone followed by plasma cleaning (Diener Femto). A paste was prepared by mixing 2 g of the synthesized ATO nanoparticles and 0.5 g of hydroxypropylcellulose (Alfa Aesar) in 10 mL of a 1/1 water/ethanol mixture. After doctor blading, the electrodes were heated to 450 °C with a ramp of 5 °C min⁻¹ and a dwelling time of 1 h at 450 °C. The resulting films had a thickness of approx. 3.5 μm. In a similar way, mesoporous TiO₂ electrodes (approx. 3.2 μm) were prepared from a commercial TiO₂ paste (Ti-Nanoxide T/SP, Solaronix). For the modification of the electrodes with a redox-active dye, the mesoporous layers were immersed into a 4 mM solution of 1-(4-cyanophenyl)-1′-(2-phosphonoethyl)-4,4′-bipyridin-1-ium (Vio) in ethanol for 16 h.