Fe/Li Co-doped CuO: enhanced photosensing and conductivity correlated with structural modifications

The photocatalytic and electronic properties of sol–gel-prepared divalent Fe³⁺ and Li⁺ co-doped monoclinic (c2/c) Cu_0.945Fe_0.055-xLi_xO powders were investigated. O-ions are in excess in Fe-rich samples, whereas O-vacancies (Vo) are prevalent in Li-rich samples due to the valence state differences between Fe³⁺ and Li⁺ ions. The bandgap remained largely unaffected, but lattice disorder increased with higher Li content. The electrical conductivity (σ) increased with increasing Li content. While the p-type nature decreased with increasing Li content, the electron mobility decreased with increasing Li content. The photocatalytic decomposition of harmful methylene blue (MB) dye was maximum for Cu_0.945Fe_0.0275Li_0.0275O. For both Cu_0.945Fe_0.055O and Cu_0.945Li_0.055O, the degradation was lesser due to other physical processes, e.g., changes in the photocurrent. Light detection was faster in Fe-rich samples compared to pure and Li-rich samples. An attempt was made to form a heterojunction of ZnO/Cu_0.945Fe_0.014Li_0.041O that exhibited significantly faster response times than their bulk counterparts for both pure and Li-rich samples. These findings highlight the potential of Cu_0.945Fe_0.055-xLi_xO samples and heterojunction configurations for enhanced photocatalytic and sensing applications.