Effects of electrode film modifications on the open-circuit photovoltage in enhanced dye-sensitized solar cells

In this study, the open-circuit photovoltage (V oc) decay technique was used to investigate the relationship between the electrode film morphology and the open-circuit photovoltage. Results indicate that dye-sensitized solar cells (DSCs) based on ordered arrays of TiO2 nanostructures (100 nm external diameters and 20–50 nm internal diameters) generally show higher open-circuit photovoltage (V oc) values than those based on sintered TiO2 nanoparticles (20–40 nm diameters). In particular, cells based on thick nanotubules (wall thickness ≥ 45 nm in our research) and on nanorods (100 nm diameters) show particularly high V oc values, indicating slow recombination kinetics under open-circuit conditions. It can be argued that the nanorods and the thick nanotubules act like singles crystals and therefore the injected electrons in the inner TiO2 molecules are shielded from holes in the electrolyte under open-circuit conditions. The open-circuit recombination time constant of electrons accumulated in the TiO2 conduction band is therefore prolonged and resulting in high V oc values.