Cu2O@CuO core-shell nanoparticles as photocathode for p-type dye sensitized solar cell

Abstract

Cu2O@CuO core-shell nanoparticles were synthesized via a facile precipitation-thermal oxidation method consisting in the preparation of Cu2O nanoparticles in solution followed by a post-treatment at 300 °C, 350 °C or 400 °C in air. From HRTEM micrographs, it was evidenced that Cu2O particles were uniformly covered by a 5 nm thick CuO layer to form a core-shell structure. This shell may be viewed as a passivating layer that overcomes the natural chemical instability of Cu2O towards electrolytes for instance. The as-obtained Cu2O@CuO nanoparticles were characterized by X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. Both techniques concluded to the p-type conductivity of the Cu2O@CuO hetero-structures. These nanoparticles were then deposited as a film on a FTO glass by screen printing and used after sintering as photocathodes for p-DSSCs. Photovoltaic activity was confirmed with DPP-NDI dye as sensitizer and tris(4,4′-ditert-butyl-2,2′-bipyridine)cobalt(III/II) as redox mediator.