![]() ![]() Chemical structures of the precursors are shown in Fig. Also note that we selected the organic precursors so that the positions of the carboxylic acid groups were in para positions in all these precursors. 1,4-benzenedicarboxylic acid (terephthalic acid, TPA), 1,4-naphthalenedicarboxylic acid (NDA) and 9,10-anthracenedicarboxylic acid (ADA), as the carboxylic acid groups have turned out to readily react with typical metal-bearing precursors in ALD/MLD. For the precursors for these organic backbones, we selected their dicarboxylic acid derivatives, i.e. The chosen aromatic backbones, benzene, naphthalene and anthracene, contain one, two and three benzene rings in their structure, respectively. Here we investigate the effect of the size of the carbon backbone on the luminescence properties of Eu-based hybrid thin films prepared by ALD/MLD. However, so far, the literature lacks details about the influence of different organic moieties on the luminescence properties of metal–organic hybrid thin films. Compared to the inorganic luminescent thin films deposited using ALD, the ALD/MLD approach offers some additional benefits, such as material deposition on polymeric substrates for flexible devices and appreciably high growth rates. The technique has also been used to deposit Ln-based hybrid thin films, which have demonstrated interesting photoluminescence (down-shifting) and upconversion characteristics. for thermoelectric devices, lithium-ion batteries and catalysis. The metal–organic materials grown by ALD/MLD have already proven their potential, e.g. The thus grown hybrid thin films are precisely thickness-controlled, conformal and uniform over large-area and complex substrate surfaces, like the inorganic thin films deposited using the parent ALD technology. This enables, through self-limiting gas-surface chemical reactions, the growth of metal–organic materials with atomic/molecular level accuracy. In ALD/MLD, mutually reactive gaseous/vaporized metal-bearing and purely organic precursors are sequentially pulsed into the reactor chamber. atomic/molecular layer deposition (ALD/MLD), could open up new horizons to the field as it allows us to combine organic linkers to the Ln species. Moreover, the currently strongly emerging counterpart of ALD for hybrid metal–organic thin films, i.e. ![]() Atomic layer deposition (ALD) is the state-of-the-art thin film technology in microelectronics and in other high-tech industrial applications and would also intuitively fit to the quality needs of the inorganic Ln-based luminescent thin films, as well as modern photonic and quantum technologies. Conventional coating methods, such as spin coating and spray drying, suffer from the poor film thickness control and the unwanted incorporation of solvent impurities into the film. A majority of these applications require the luminescent material in the form of a thin film or coating. Lanthanide (Ln)-based luminescent materials exhibit all of the aforementioned photon conversion processes and can be implemented for a breadth of applications, such as solar cells, lasers, displays, lighting, sensors, bioimaging, disease diagnostics and therapy, (bio)chemical analysis and security tags. In downconversion, the UV photon absorption produces two or more Vis photons, while in downshifting only a single Vis photon is emitted. The high- to low-energy photon conversion can be of downconversion or downshifting type. ![]() The low- to high-energy photon conversion process (IR to Vis) is called upconversion, and it involves sequential absorption of two or more IR photons to emit single Vis photon. Luminescence is a photo-physical phenomenon leading to light emission (typically in the visible range) upon absorption of higher (typically ultraviolet, UV) or lower energy (infrared, IR) photons in certain materials. 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. Moreover, for the Eu-terephthalate films with the single benzene ring as the organic backbone, we investigate the effects of diluting the Eu 3+ concentration with Y 3+ to reveal that the emission intensity is optimized around 12% Eu 3+ concentration. Enlarging the backbone shifts the excitation towards visible wavelengths, but it simultaneously decreases the emission intensity. 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). Here we show that the backbone of the organic ligand has a profound impact on the luminescence characteristics of lanthanide-organic materials. ![]()
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