Fabrication a thin nickel oxide layer on photoanodes for control of charge recombination in dye-sensitized solar cells

A thin NiO layer (∼164 nm in thickness) is fabricated on the surface of TiO2 photoanode by a simple hydrothermal method. The TiO2/NiO photoanode prepared on the hydrothermal temperature of 100 °C (TiO2/NiO-100) shows enhancement of light-harvesting ability and excellent dye adsorption amount. Moreover, the intensity-modulated photovoltage spectroscopy, intensity-modulated photocurrent spectroscopy and electrochemical impedance spectroscopy measurements illustrate that the NiO layer makes the dye-sensitized solar cells (DSSCs) with TiO2/NiO photoanodes shorten electron transport time, lengthen electron lifetime and obtain a higher charge collection efficiency than that of DSSCs with TiO2 photoanodes. Hence, the TiO2/NiO photoanode can efficiently decrease the electron transport resistance and charge recombination action. The DSSCs with TiO2/NiO-100 have an improvement photovoltaic performance and can obtain a higher value of power conversion efficiency (8.93 ± 0.34%) than that of DSSCs with TiO2 photoanodes (8.17 ± 0.33%) under full sunlight illumination (100 mW cm−2, AM 1.5 G).