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Volatile Eu complexes, namely Eu(TTA)3Phen, Eu(x)Y(1-x)(TTA)3Phen; Eu(x)Tb(1-x)(TTA)3Phen; Eu, europium; Y, yttrium; Tb, Terbium; TTA, thenoyltrifluoroacetone; and Phen, 1,10 phenanthroline were synthesized by maintaining stichiometric ratio. Various characterization techniques such as X-ray diffraction (XRD), photoluminescence (PL) and thermo gravimetric analysis/differential thermal analysis (TGA/DTA) were carried out for the synthesized complexes. Diffractograms of all the synthesized complexes showed well-resolved peaks, which revealed that pure and doped organic Eu(3+) complexes were crystalline in nature. Of all the synthesized complexes, Eu0.5Tb0.5(TTA)3Phen showed maximum peak intensity, while the angle of maximum peak intensity for all complexes was almost the same with slightly different d-values. A prominent sharp red emission line was observed at 611 nm when excited with light at 370 nm. It was observed that the intensity of red emissions increased for doped europium complexes Eu(x)Y(1-x)(TTA)3Phen and Eu(x)Tb(1-x)(TTA)3Phen, when compared with Eu complexes. Emission intensity increased in the following order: Eu(TTA)3Phen > Eu0.5Tb0.5(TTA)3Phen > Eu0.4Tb0.6(TTA)3Phen > Eu0.5Y0.5(TTA)3Phen > Eu0.4Y0.6(TTA)3Phen, proving their potential application in organic light-emitting diodes (OLEDs). TGA showed that Eu complexes doped in Y(3+) and Tb(3+) have better thermal stability than pure Eu complex. DTA analysis showed that the melting temperature of Eu(TTA)3Phen was lower than doped Eu complexes. These measurements infer that all complexes were highly stable and could be used as emissive materials for the fabrication of OLEDs.

The mechanism of energy transfer leading to electroluminescence (EL) of a lanthanide complex, Eu x Y (1-x) (TTA) 3 Phen (TTA= thenoyltrifluoro-acetone, phen=1,10-phenanthroline), doped into TPBi(1,3,5-tris(N-Phenyl-benzimidizol-2-yl) benzene host at 15 wt% of host is investigated. With the device structure of anode/hole transport layer/Eu x Y (1-x) (TTA) 3 Phen (15%): TPBi/electron transport layer/cathode, maximum luminescence of 185.6 cd/m 2 and 44.72 cd/m 2 was obtained from device I made of Eu 0.4 Y 0.6 (TTA) 3 Phen and device II made of Eu 0.5 Y 0.5 (TTA) 3 Phen, respectively at 18 volts. Saturated red Eu 3+ emission based on 5 D 0 → 7 F 2 transition is centered at a wavelength of 612 nm with a full width at half maximum of 5 nm. From the analysis of I-V, J-V-L characteristics and electroluminescent (EL) spectra, we conclude that direct trapping of holes and electrons and subsequent formation of the excitation occur on the dopant, leading to high quantum efficiencies at low current densities. These results show that fabricated OLED devices can successfully emit saturated red light and can be used in applications such as opto-electronic OLED devices, displays and solid state lighting technology.

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Pure and Na(+) -doped Alq3 complexes were synthesized by a simple precipitation method at room temperature, maintaining a stoichiometric ratio. These complexes were characterized by X-ray diffraction, Fourier transform infrared (FTIR), UV/Vis absorption and photoluminescence (PL) spectra. The X-ray diffractogram exhibits well-resolved peaks, revealing the crystalline nature of the synthesized complexes, FTIR confirms the molecular structure and the completion of quinoline ring formation in the metal complex. UV/Vis absorption and PL spectra of sodium-doped Alq3 complexes exhibit high emission intensity in comparison with Alq3 phosphor, proving that when doped in Alq3 , Na(+) enhances PL emission intensity. The excitation spectra of the synthesized complexes lie in the range 242-457 nm when weak shoulders are also considered. Because the sharp excitation peak falls in the blue region of visible radiation, the complexes can be employed for blue chip excitation. The emission wavelength of all the synthesized complexes lies in the bluish green/green region ranging between 485 and 531 nm. The intensity of the emission wavelength was found to be elevated when Na(+) is doped into Alq3 . Because both the excitation and emission wavelengths fall in the visible region of electromagnetic radiation, these phosphors can also be employed to improve the power conversion efficiency of photovoltaic cells by using the solar spectral conversion principle. Thus, the synthesized phosphors can be used as bluish green/green light-emitting phosphors for organic light-emitting diodes, flat panel displays, solid-state lighting technology - a step towards the desire to reduce energy consumption and generate pollution free light.

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