These submicron-sized light scatterers can either be mixed into the nanocrystalline film [14, 15] or form a scattering layer on the top of the nanocrystalline Copanlisib chemical structure film [16–20]. In addition to submicron-sized particles, some other nanostructures, such as nanowires [21–23] and nanotubes [24, 25] have also been studied as light scatterers in DSCCs. Recently, a promising three-dimensional nanostructure that has been developed to fulfill multiple functions in DSSCs is nanocrystallite aggregates [26–29]. These aggregates

not only provide a large interfacial surface area, but also generate light scattering because they are composed of nanoparticles that assemble into submicron aggregates. Employing nanocrystallite aggregates can avoid the drawbacks of using large particles as light scatterers in conventional DSSCs. Mixing the large particles into the nanocrystalline film unavoidably causes a decrease in the interfacial surface area of the film, whereas placing the large particles on top of the nanocrystalline film brings about a limited increase in the interfacial surface area of the film. Regardless of the film nanoarchitecture employed, film

thickness and dye adsorption time are two important factors that must be considered during photoanode fabrication. Increasing the total interfacial surface area of the porous Vistusertib cost film by raising the film thickness is simple, which boosts the amount of dye adsorbed and, thus, light absorption. Thus, raising the film thickness can increase the short-current density (J SC) [21, 30]. However, a thick film also aggravates unwanted charge recombination and poses more restrictions on mass transfer. Consequently, both the open-current voltage (V OC) and overall conversion efficiency decline [14, 21, 30, 31]. Therefore, film thickness must be optimized to obtain efficient cells. Another key fabrication factor is the dye adsorption time, which determines the quantity and the nature of the adsorbed dye molecules. The dye adsorption time

should be sufficiently long so that the interfacial surface of the oxide film is completely covered with a monolayer of dye molecules. In fabricating TiO2-based photoanodes, the length of the dye Doxacurium chloride adsorption time is first determined and then applied to all film thicknesses during the subsequent thickness optimization process [32–34]. This is because TiO2 is insensitive to prolonged sensitization times because of its higher chemical LB-100 order stability. Conversely, a prolonged dye adsorption time in ZnO-based photoanodes often significantly deteriorates cell performance. Thus, varying film thicknesses may require different dye adsorption times for optimal cell performance. Compared to TiO2, ZnO is less stable with acidic dyes, such as Ru-based N3 and N719 dyes. The formation of Zn2+/dye aggregates is a result of ZnO dissolution in these acidic dye solutions [32, 35–37].