Enhanced photovoltaic properties of overlayer-coated nanocrystalline TiO2 dye-sensitized solar cells (DSSCs)

TiO2 dye-sensitized solar cells (DSSCs) coated with various oxide layers were fabricated via a screen printing method and the effects of the oxide layers on the photovoltaic properties were systematically investigated. The open circuit voltage (V (oc)) was closely dependent to the conduction band (CB) edge position and the band gap energy (E (g)) of the oxide layers, while the short circuit current density (J (sc)) was related to the iso-electric point (IEP). V (oc) showed an increasing behavior with the CB edge position of the oxide layers, which could be explained by the blocking effect of the insulating layers. Although J (sc) was basically proportional to the IEP and the resulting dye adsorption, there were other factors like the resistance of oxide layers. The cell efficiency could be enhanced by 60% when the cells were coated with the oxide layers of high E (g) and IEP.