Optical and computational analysis of red light emitting Eu(III) complexes for applications in luminescent devices

Abstract

Eight co-ordinated Eu(III) complexes of type [Eu (L3). X] were synthesized for applications in organic light emitting devices. The complexes are reported in solid state, where L is 6-methyl-chromone-3-aldehyde and X represent 2H2O(C1), 1,10-phenanthroline (C2), neocuproine (C3), biquinoline (C4), bathophenanthroline (C5), 5,6-Dimethyl-1,10-phenanthroline (C6). The prepared Eu complexes were characterized by elemental analysis, FT-IR and 13C, 1H NMR, photoluminescence (PL) and thermo-gravimetric analysis/differential thermal gravimetric analysis (TGA/DTA) studies. The photoluminescence emission spectra of solid and solution phase showed five characteristic peaks arising from 5D0→7FJ (J = 0–4) transitions of europium ion obtained at excitation of λex = 370 nm (solid state) and λex = 385 nm (solution). The highest intensity of peak at 615 nm in solid form whereas at 612 nm in solution, indicated strong emission because of 5D0→7F2 transition. This peak is sharp and responsible for superior red color purity. The optical band gap, refractive index and energy transfer mechanism were also obtained for all complexes. Luminescence decay time (τ), radiative and non-radiative transition rate, luminescence efficiency and Judd-Ofelt intensity parameters were analyzed by PL spectroscopy. The CIE color coordinates value and branching ratio values were determined for all synthesized complexes in both solid and solution form. The outcomes revealed that synthesized complexes are magnificent emitters with wide applications in electroluminescent materials, display devices and laser materials.