Defect Structure and Photovoltaic Characteristics of Internally Stacked CuO/Cu₂O Photoactive Layer Prepared by Electrodeposition and Heating

The internally stacked CuO/Cu2O photoactive layers were prepared by electrodeposition of the Cu2O layer followed by heating in air. The 1.4 eV-p-CuO layer was heteroepitaxially grown on the Cu2O layer accompanied by the formation of nanopores by heating at 573 K, and both the CuO and Cu2O layers possessed excellent semiconductor qualities with band-edge emission in the visible light region. The internally stacked CuO/Cu2O photoactive layer revealed the photovoltaic performance in a corresponding wide photon energy range due to the utilization of the photovoltaic ability for both the CuO and Cu2O layers by applying a bias voltage. Heating at 673 K induced transfer of the thickened CuO layer to the polycrystalline phase and coalescence of nanopores, resulting in the disappearance of the light emission and photovoltaic performance, irrespective of the bias voltage. The crystal and semiconductor qualities for both the CuO and Cu2O layers affected the photovoltaic performance for the internally stacked CuO/Cu2O photoactive layer.