Electrical and optical properties of copper-complexes thin films grown by the vacuum thermal evaporation technique

In this work, the synthesis and characterization of molecular materials formed from K₂[Cu(C₂O₄)₂], 1,8-dihydroxyanthraquinone and its potassium salt are reported. These complexes have been used to prepare thin films by vacuum thermal evaporation. The synthesized materials were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), fast atomic bombardment (FAB+) mass and ultraviolet-visible (UV-vis) spectroscopy. Electrical transport properties were studied by dc conductivity measurements. The electrical activation energies of the complexes, which were in the range of 0.36-0.65 eV, were calculated from their Arrhenius plots. Optical absorption studies in the 100-1100 nm wavelength range at room temperature showed thin films' optical band gaps in the 2.3-3.9 eV range for direct transitions. On the other hand, strong visible photoluminescence (PL) at room temperature was noticed from the thermally-evaporated thin solid films. The PL of all investigated samples were observed with the naked eye in a bright background. The PL and absorption spectra of the investigated compounds are strongly influenced by the molecular structure and nature of the organic ligand.