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