Effect of carbon backbone on luminescence properties of Eu-organic hybrid thin films prepared by ALD/MLD

Here we show that the backbone of the organic ligand has a profound impact on the luminescence characteristics of lanthanide-organic materials. We employ the emerging atomic/molecular layer deposition (ALD/MLD) technique to deposit europium-based thin films where the organic ligands vary in terms of the number of aromatic rings in their backbone (benzene, naphthalene and anthracene). Enlarging the backbone shifts the excitation towards visible wavelengths, but it simultaneously decreases the emission intensity. Moreover, for the Eu-terephthalate films with the single benzene ring as the organic backbone, we investigate the effects of diluting the Eu³⁺ concentration with Y³⁺ to reveal that the emission intensity is optimized around 12% Eu³⁺ concentration. Interestingly, such a dependence of luminescence intensity on the concentration of emitting species suggests that our (Eu,Y)-organic thin films behave more like ionic phosphors than discrete metal–ligand molecules. Graphical abstract: [Figure not available: see fulltext.]