New hybrid materials for organic light-emitting diode devices

The regularities of polymorphism in high-purity crystalline tris(8-hydroxyquinoline) aluminum, gallium, and indium (Meq 3) have been studied in the temperature range of 300–712 K. From the results of an analysis of photoluminescence and Raman spectra and X-ray diffraction data, a generalized picture has been produced, according to which, for all the studied compounds, a series of polymorphic transitions is the same: β → α → δ → γ → ɛ. Based on high-purity single-phase specimens of the investigated metal complexes and boron oxide, new hybrid materials have been synthesized: bulk samples (alloying technique) and thin films (vacuum thermal evaporation). The photo- and electroluminescent properties of the hybrid materials at room temperature have been investigated. It has been established that, as the synthesis duration of the bulk hybrid materials increases from 5 to 60 min, a photoluminescence maximum shifts to a short-wavelength domain from the value typical of pure δ(γ)-Meq 3 by 40, 15, and 10 nm for Alq 3, Gaq 3, and Inq 3, respectively.