Remarkable photocurrent of p-type dye-sensitized solar cell achieved by size controlled CuGaO2 nanoplates

Abstract

In this paper, we report the successful hydrothermal synthesis of CuGaO₂ nanoplates with a critically small size and deposition methods to fabricate effective p-type semiconductive photocathodes in dye-sensitized solar cells (DSCs). Based on an efficient P1 dye and an iodide electrolyte, the optimal CuGaO₂ photocathode has achieved remarkably high photocurrent density, up to 2.05 mA cm⁻². To the best of our knowledge, this is the highest achieved by nanocrystalline p-type semiconductors besides NiO. The light harvesting, charge collection in CuGaO₂ and NiO based DSCs have been compared. Owing to size control of the CuGaO₂ nanoplates and subsequent mechanical pressing for photocathode film deposition, the light harvesting efficiency of the CuGaO₂ photocathode is greatly increased to a comparable level to that of the NiO reference. Another noteworthy feature is the remarkably high charge collection efficiency of the CuGaO₂ photocathode, which should benefit from the nature of delafossite oxides with a high conductivity leading to a much higher hole diffusion coefficient in the DSC system. The open-circuit voltage is 199.3 mV, about twice as high as that of the NiO reference, benefiting from the valence band position shifting from −5.15 eV for NiO to −5.29 eV for CuGaO₂versus the vacuum level.