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.