Synthesis and Optical Characterization of Mixed Ligands Beryllium Complexes for Display Device Applications

Synthesis and photoluminescent behaviour of mixed ligand based beryllium complexes with 2-(2-hydroxyphenyl)benzoxazole (HPB) and 5-chloro-8-hydroxyquinoline (Clq) or 5,7-dichloro-8-hydroxyquinoline (Cl2q) or 2-methyl-8-hydroxyquinoline (Meq) or 8-hydroxyquinoline (q) are reported in this work. These complexes, that is, [BeHPB(Clq)], [BeHPB(Cl2q)], [BeHPB(Meq)], and [BeHPB(q)], were prepared and their structures were confirmed by elemental analysis, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and thermal analysis. The beryllium complexes exhibited good thermal stability up to ~300°C temperature. The photophysical properties of beryllium complexes were studied using ultraviolet-visible absorption and photoluminescence emission spectroscopy. The complexes showed absorption peaks due to π-π∗ and n-π∗ electronic transitions. The complexes emitted greenish blue light with peak wavelength at 496 nm, 510 nm, 490 nm, and 505 nm, respectively, consisting of high intensity. Color tuning was observed with changing the substituents in quinoline ring ligand in metal complexes. The emitted light had Commission Internationale d’Eclairage color coordinates values at x=0.15 and y=0.43 for [BeHPB(Clq)], x=0.21 and y=0.56 for [BeHPB(Cl2q)], x=0.14 and y=0.38 for [BeHPB(Meq)], x=0.17 and y=0.41 for [BeHPB(q)]. Theoretical calculations using DFT/B3LYP/6-31G(d,p) method were performed to reveal the three-dimensional geometries and the frontier molecular orbital energy levels of these synthesized metal complexes

Optoelectronic characterization of zinc complexes for display device applications

2-(2-Pyridyl)benzimidazolato)-2-methyl-8-hydroxyquinolinatozinc(II)[ZnPBI(Meq)], 2-(2-pyridyl)benzimidazolato)-5-chloro-8-hydroxyquinolinatozinc(II) [ZnPBI(Clq)] and 2-(2-pyridyl)benzimidazolato)-8-hydroxyquinolinatozinc(II) [ZnPBI(q)] were synthesized and characterized for the purpose to be used as electroluminescent materials. All complexes emitted bright colored light on excitation by ultra-violet light source which showed their suitability for the operation in opto-electronic devices. Using a selected complex [ZnPBI(Meq)] as emissive layer, multilayered organic electroluminescent device was fabricated having structure ITO/alpha-NPD/Zinc complex/BCP/Alq(3)/LiF/Al, that produced bright bluish green emission at 532 nm. Maximum luminescence observed was 4038 cd/m(2) at 18 V while the turn on voltage of the device was 7 V. The Commission Internationale d'Eclairage chromaticity of the device had color coordinates at x = 0.35, y = 0.44 and was found to be independent of the operating voltages. The [ZnPBI(Meq)] complex exhibited high thermal stability (> 300 A degrees C) and high glass transition temperature (> 150 A degrees C)