Exploring vivid red light emanating europium complexes incorporating a β-ketoester antenna for advanced displays: a detailed photophysical, Judd–Ofelt and computational investigation

Abstract

Five new organo-europium samples consisting of β-ketoester (diethyl oxalpropionate) together with secondary sensitizers (neocuproine, bathophenanthroline, 1,10-phenanthroline and 4,4′-dimethyl-2,2′-bipyridyl) were successfully synthesized as well as characterized. The structural compositions of the samples were elucidated using EDAX and elemental analysis. The PXRD profile disclosed the crystalline nature of the samples, and the surface morphology possessing rod-shaped agglomerates was further confirmed by the FESEM micrograph. The complexation of Eu(III) with DO occurs via the O atom of the CO moiety, as indicated by FT-IR spectroscopy and NMR spectroscopy investigations. The theoretical evaluation of the optical band gap using DFT aligns closely with the values derived experimentally from Tauc plots. The band gap range of 3.36–3.79 eV indicates its applicability in semiconductors. The emission spectra procured by exciting the samples at 360 nm portrayed peaks at 655, 616, 596 and 584 nm associated with ⁵D₀ → ⁷F_J (J = 3, 2, 1, 0, respectively) transitions. The pronounced red photoluminescence is mainly governed by the prominent ⁵D₀ → ⁷F₂ transition of the Eu(III) ions. The photophysical parameters of the samples were further analysed to evaluate the photoluminescence decay time, Judd–Ofelt intensity parameter, intrinsic quantum efficiency, and radiative and nonradiative decay rates. Colorimetric investigations authenticate these samples as warm red light emitters, validating their promising utility as red components in light emitting sources. A study of the energy transmission pathway revealed a correlation between the triplet state of the sensitizers and the resonating levels of the metal center. These results highlight the incredible potential of these luminous europium samples for photonic and display devices.