Fabrication of n–p junction electrodes made of n-type SnO2 and p-type NiO for control of charge recombination in dye sensitized solar cells

Abstract

Abstract The n–p junction electrode fabricated coating nanocrystalline SnO 2 thin film with a thin layer of p-type NiO was found to increase the sensitized photocurrent and photovoltage. In addition, increase in the fill factor was noticed due to inhibition of electron back transfer from SnO 2 to the redox electrolyte (I 3 − ) by both junction effect and presence of NiO barrier, resulting in much better energy conversion efficiencies. The highest cell efficiency was obtained for the cell fabricated by immersing SnO 2 thin films in soluble Ni salts, and converting them to NiO by firing. The optimum NiO coating thickness was found to be only a few angstroms and the energy levels of the excited dye and the conduction band position of NiO suggest that the electron transfer from the excited dye to the underlying SnO 2 layer occurs by tunneling through the p-type NiO layer.