Abstract
Strong visible photoluminescence (PL) at room temperature is obtained from thermal-evaporated thin solid films of Metallophthalocyanine (M = Co, Fe, Pb) and double potassium salt from 1,8 dihydroxyan-thraquinone. The PL of all the investigated samples is observed with the naked eye in a bright background. The deconvolution of the normalized PL spectra shows that each PL spectrum is composed of four emission bands which peak at approximately the same energies of 2.1, 2.2 and 2.4 eV and whose intensities and widths depend upon the structure of the complexes. FTIR and ellipsometry are employed to investigate the structural differences among the films. The optical absorption of the films is also investigated to evaluate the changes in the electronic structure of these metal organic compounds, with respect to other metalphtalocya-nines thin films. Our results suggest that the visible PL comes from radiative transitions between energy lev-els associated to the double potassium salt coordination to the metallic ion in the phthalocyanine.
Highlights
Since the report, more than two decades ago, of efficient electroluminescence (EL) from organic thin films [1], the use of small organic molecules and organic polymers in the fabrication of organic light emitting diodes (OLED’s) attracts considerable interest for solid state displays and lighting applications [2]
Strong visible photoluminescence (PL) at room temperature is obtained from thermal-evaporated thin solid films of Metallophthalocyanine (M = Co, Fe, Pb) and double potassium salt from 1,8-dihydroxyanthraquinone
Our results suggest that the visible PL comes from radiative transitions between energy levels associated to the double potassium salt coordination to the metallic ion in the phthalocyanine
Summary
More than two decades ago, of efficient electroluminescence (EL) from organic thin films [1], the use of small organic molecules and organic polymers in the fabrication of organic light emitting diodes (OLED’s) attracts considerable interest for solid state displays and lighting applications [2]. One of the foremost class of planar organic molecular semiconductors, used as electron or hole transport layer, is that of the metallophthalocyanines (MPcs). Optical properties of these materials, among them the luminescence, are strongly related to the valence band electronic configuration, as well as the excitation and the de-excitation processes between highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) [3]. Molecules crystallize and their interaction is significant, so that dramatic changes occur in their optical properties, making them much more complicated [5] Since these organic materials in the solid film form are applied in the production of the majority of modern optoelectronic devices, the knowledge of their excited electronic states and relaxation processes is important [5]. Vibrational spectra are obtained and the refractive indices and absorption coefficients are determined for the studied samples
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