The conduction band of the DOS with and without the U parameter is predominantly composed of empty Fe-3d states. Only very weak contributions of O states can be seen for higher energy values in the conduction band. This agrees with previously reported experimental and theoretical studies. In the DOS calculated by DFT+U , the Fe-3d states cover a larger region from 1.33 to 3 eV. The lowest optical transition is thereby achieved by an electron excitation from O-2p states to Fe-3d states. Studies suggest that the electron excitation is followed by an electron transfer from Cu-3d states to deeper O-2p states, facilitating the charge separation process in the surface. This effect enhances the charge carrier lifetime and improves the stability significantly compared to the binary oxide Cu 2 O. Despite the longevity of excited electrons in CFO, studies indicate a self-trapping effect due to polaron hopping, which is based on an electron excitation into a Fe-3d orbital in the conduction band. Consequently, a reduction of Fe 3+ to Fe 2+ occurs, leading to a change in the Fe-O bond length. For CFO the DFT+U approach yields a band gap of 1.33 eV, which agrees with experimental and theoretical values reported in literature. However, the band gap calculated without the U parameter almost yields a metallic character. Thus, applying Hubbard corrections is required for realistic predictions of the semiconducting behavior of both materials.