Enhanced open-circuit photovoltage and charge collection realized in pearl-like NiO/CuO composite nanowires based p-type dye sensitized solar cells

Low open-circuit photovoltage and poor hole transfer character of semiconductors have limited the development of p-type dye-sensitized solar cells (p-DSSCs) owing to the minor energy-gap between the conduction band of NiO and the Nernstian potential of the I₃⁻/I⁻ electrolyte, as well as the low intrinsic hole-conductivity of NiO semiconductor. Hereby, a novel NiO/CuO nanocomposite was well-designed and successfully fabricated as photocathode material of p-DSSCs. Combined with Co²⁺/Co³⁺ electrolyte, the devices showed noticeable enhancement of both open-circuit photovoltage and short-circuit photocurrent. Compared to NiO, a deeper valence-band of NiO/CuO resulted in a 140 mV improvement of photovoltage of p-DSSCs. Electrochemical impedance spectroscopy indiates an improved hole transport of NiO/CuO nanocomposite due to modified effect by CuO. Charge recombinations are also suppressed to achieve increased charge collection efficiencies and improved photoelectrochemical performance.