ITO nanoparticles (18 nm, 99.99%) were sonicated in 10mL EtOH for 10 min when a mixture of ethyl cellulose (200 mg), alcohol surfactant (proprietary nanopowder dispersant, 225 mg), and terpineol (5.0 g) in 5mL EtOH was added and the suspension was sonicated for 5 min. The volatiles were removed by rotary evaporation to form a blue paste. The paste was diluted with EtOH (1:4) and is used for spincoating as reported in our previous work. Electrode preparation: The electrode surfaces were prepared by cutting 1.25 cm x 2.5 cm or 1.0 cm x 3.5 cm FTO (fluorine-doped tin oxide) glass plates and washing them for 10 min in acetone, 10 min in soap and H2O, 10 min in H2O, followed by 10 min of EtOH (7:3) in an ultrasonic bath. Afterwards, the plates were dried under an N2 stream (30 sec.), and half of the plate (~1 cm) was wrapped in Kaptontape, followed by spin coating with an mITO (mesoporous indium tin oxide) mixture (in EtOH). For the first mITO layer, 25-30 μL of the mixture was pipetted onto the plates, and the samples were spin-coated and afterwards dried on a heat plate at 120ºC for 10 min. This process was repeated twice with the second and third layers using 25 μL of mITO mixture volume. For the H-cell 3.5 cm x 1cm plates were prepared. Therefore, 180 μL of the spin-coating suspension was used. In the last cycle, the mITO (on FTO) plates were dried for 60 minutes at 450 ºC after the tape was removed.