Reproducible electrochemical analysis of nanostructured Cu2O using a non-aqueous 3-methoxypropionitrile-based electrolyte

Cu2O is an attractive material in terms of semiconducting properties and is considered a leading candidate in all-oxide photovoltaics. Electrochemical analysis of Cu2O, including Mott-Schottky (MS) and impedance spectroscopy (IS), provides a wealth of data on charge carriers, Fermi level and interface properties. MS and IS are usually measured in aqueous solutions. However, Cu2O is easily reduced or oxidized to Cu or CuO in aqueous solutions, the layer peels off after the analysis and there is a small voltage window for the tests. In some cases, an anti-corrosive n-type barrier layer is employed on top of the bare Cu2O electrode to make the measurement possible, which could result in deviation from actual values. Here we introduce a non-aqueous electrolyte based on tetrabutylammonium-tetrafluoroborate in 3-methoxypropionitrile for electrochemical analysis of Cu2O. MS analysis shows reproducible results in terms of dopant density and flat band potential, while the analysis in aqueous (0.5 M Na2SO4) electrolyte shows inconsistent, irreproducible results. In the case of IS, the transport resistivity of the layers was evaluated using the new electrolyte and shows a linear trend with thickness, as expected. The proposed non-aqueous electrolyte can potentially be used for the electrochemical analysis of other sensitive semiconductors.