Thermal quenching and luminescence lifetime of saturated green Sr1−xEuxGa2S4 phosphors

Joos, Jonas; Meert, Katrien; Parmentier, Anthony; Poelman, Dirk; Smet, Philippe

doi:10.1016/j.optmat.2012.05.025

Cited by 30 publications

(33 citation statements)

References 35 publications

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“…In addition to the thermal quenching affecting the emission intensity we also find that it affects emission lifetime, which is consistent with previous measurements of other lanthanide-doped complexes [77,[81][82][83]. We characterize the influence of thermal quenching on the lifetime of [Y 1−x Dy x (acac) 3 (phen)] by measuring the lifetime of the emission at 482 nm and 575 nm for the 10 mol% sample, as shown in Figure 12.…”

Section: Luminescence Lifetimesupporting

confidence: 89%

“…From Figure 8 we find that as the concentration increases the lifetime becomes shorter, with the largest change occurring when going from 1 mol% to 5 mol%. The influence of concentration quenching on lanthanide luminescence lifetimes has been studied in depth [48,[62][63][64][65][66][76][77][78][79][80] with the two main mechanisms of concentration quenching in solid-state materials being: long-range Energy Transfer (LRET) [62][63][64][65]80], and short-range Dexter electron exchange [66]. These mechanisms result in different functional behavior of the lifetime as a function of concentration.…”

Section: Concentration Dependencementioning

confidence: 99%

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Two-color thermosensors based on [Y $$_{1-x}$$ 1 - x Dy $$_x$$ x (acetylacetonate) $$_3$$ 3 (1,10-phenanthroline)] molecular crystals

2017

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We develop a two-color thermometry (TCT) phosphor based on [Y1−xDyx(acetylacetonate)3(1,10-phenanthroline)] ([Y1−xDyx(acac)3(phen)]) molecular crystals for use in heterogeneous materials. We characterize the optical properties of [Y1−xDyx(acac)3(phen)] crystals at different temperatures and Dy concentrations and find that the emission is strongly quenched by increasing temperature and concentration. We also observe a broad background emission (due to the ligands) and find that [Y1−xDyx(acac)3(phen)] photodegrades under 355 nm illumination with the photodegradation resulting in decreased luminescence intensity. However, while decreasing the overall emission intensity, photodegradation is not found to influence the integrated intensity ratio of the 4 I 15/2 → 6 H 15/2 and 4 F 9/2 → 6 H 15/2 transitions. This ratio allows us to compute the temperature of the complex Based on the temperature dependence of these ratios we calculate that [Y1−xDyx(acac)3(phen)] has a maximum sensitivity of 1.5 % K −1 and our TCT system has a minimum temperature resolution of 1.8 K. Finally, we demonstrate the use of [Y1−xDyx(acac)3(phen)] as a TCT phosphor by determining a dynamic temperature profile using the emission from [Y1−xDyx(acac)3(phen)].

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Section: Luminescence Lifetimesupporting

confidence: 89%

Section: Concentration Dependencementioning

confidence: 99%

Two-color thermosensors based on [Y $$_{1-x}$$ 1 - x Dy $$_x$$ x (acetylacetonate) $$_3$$ 3 (1,10-phenanthroline)] molecular crystals

2017

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“…Eu 2+ doping is expected to deform the coordination polyhedron only minimally due to the comparable ionic radii of Eu 2+ and Sr 2+ and given that EuGa 2 S 4 is isostructural with SrGa 2 S 4 [53,54,55]. Doped with Eu 2+ or Ce 3+ , this compound has been thoroughly described in view of multiple applications such as electroluminescent displays, field-emissive devices and more recently LED phosphor [56,57,58,59,60,61].…”

Section: Crystal Structurementioning

confidence: 99%

Nonequivalent lanthanide defects: Energy level modeling

2016

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Empirical charge-state transition level schemes are popular tools to model the properties of lanthanide-doped materials and their construction has become standard practice. Typically, it is implicitly assumed that all lanthanide ions form isostructural defects. However, in practice, multiple nonequivalent defects related to the same lanthanide can occur or different lanthanides can even incorporate in different ways. The consequences of these complications on the impurity energy levels are discussed in this article. It seems that small structural differences around the lanthanide dopant can give rise to important spectral differences in its emission. These are not always clearly reproduced by the charge-state transition level schemes. Improvements to the existing procedure are suggested and applied to the lanthanide ions in the well-studied host crystals SrAl2O4, Sr2Si5N8 and SrGa2S4.

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“…isolated Eu ions, showing a textbook-like behavior and Eu clusters, responsible for accelerated thermal quenching. 33 It is our aim to validate this simple model by a microscopic study of the thermal quenching behavior. …”

mentioning

confidence: 99%

“…This material is known as a saturated green phosphor, especially suitable for display applications. 9,[29][30][31][32][33] It was deduced from macroscopic TQ and luminescence decay measurements that two types of Eu ions determine the luminescent properties, i.e. isolated Eu ions, showing a textbook-like behavior and Eu clusters, responsible for accelerated thermal quenching.…”

mentioning

confidence: 99%

Microscopic Study of Dopant Distribution in Europium Doped SrGa₂S₄: Impact on Thermal Quenching and Phosphor Performance

Martin¹,

Poelman²,

Smet³

et al. 2017

ECS J. Solid State Sci. Technol.

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White light emitting diodes start to dominate lighting and display applications. However, the properties of the phosphors used in these devices strongly depend on synthesis conditions. A better understanding of how performance-determining mechanisms such as thermal quenching are influenced by synthesis conditions and sample composition is necessary to achieve the required standards in a goal-oriented strategy. In this paper, a microscopic thermal quenching study on green-emitting SrGa 2 S 4 :Eu 2+ phosphors by means of cathodoluminescence spectroscopy and energy dispersive X-ray analysis in a scanning electron microscope is used to extend our knowledge beyond averaged information obtained on bulk material. Elemental and cathodoluminescence mapping at different temperatures made it possible to determine thermal quenching profiles for sub-micrometer sized areas. These revealed a broad range of local quenching temperatures for samples with ill-distributed dopant ions. For the associated activation energy an upper limit of 0.61 eV was identified, corresponding to the intrinsic thermal quenching of isolated europium ions. Furthermore, the results confirm a previously suggested thermal quenching model which involves the presence of both isolated and clustered dopant ions. Inorganic luminescent materials or phosphors are currently applied on a large scale in various novel technologies. Most notably, white light-emitting diodes (LEDs), which are applied in lighting and display technologies, rely on high-performance phosphors. [1][2][3] Here, the emission of a blue light source, based on a Ga 1-x In x N LED chip is partly absorbed by the phosphor blend that is applied on top of this chip or in a remote fashion. [4][5][6] The phosphor re-emits the absorbed energy as green, yellow and red light, which is mixed with the remaining blue LED emission as to get an overall white emission. This requires subtle fine-tuning, both in terms of material composition, 7,8 as well as device manufacturing 5,9 to achieve white LED devices with the desired properties.From the materials point of view, phosphor properties are highly dependent on synthesis conditions, often in an unpredictable and hardto-control way. This can be attributed to an incomplete understanding of the underlying physical mechanisms for various macroscopic properties. 10 As an example, thermal quenching (TQ), i.e. the decreased internal quantum efficiency of luminescent materials at elevated temperatures, has been attributed to various causes, either intrinsic to the luminescent center itself or due to external influences such as the presence of defects or the local clustering of luminescent ions. 10,11 The undetermined nature of TQ makes it difficult to engineer synthesis routines to yield phosphors with a minimized TQ and an optimized performance.Phosphors are generally studied at the macroscopic level, i.e measurements are typically performed on milligram quantities, a scale which is of relevance for applications. Nonetheless, if materials are inhomogeneous in terms...

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Thermal quenching and luminescence lifetime of saturated green Sr1−xEuxGa2S4 phosphors

Cited by 30 publications

References 35 publications

Two-color thermosensors based on [Y $$_{1-x}$$ 1 - x Dy $$_x$$ x (acetylacetonate) $$_3$$ 3 (1,10-phenanthroline)] molecular crystals

Two-color thermosensors based on [Y $$_{1-x}$$ 1 - x Dy $$_x$$ x (acetylacetonate) $$_3$$ 3 (1,10-phenanthroline)] molecular crystals

Nonequivalent lanthanide defects: Energy level modeling

Microscopic Study of Dopant Distribution in Europium Doped SrGa₂S₄: Impact on Thermal Quenching and Phosphor Performance

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Thermal quenching and luminescence lifetime of saturated green Sr1−xEuxGa2S4 phosphors

Cited by 30 publications

References 35 publications

Two-color thermosensors based on [Y $$_{1-x}$$ 1 - x Dy $$_x$$ x (acetylacetonate) $$_3$$ 3 (1,10-phenanthroline)] molecular crystals

Two-color thermosensors based on [Y $$_{1-x}$$ 1 - x Dy $$_x$$ x (acetylacetonate) $$_3$$ 3 (1,10-phenanthroline)] molecular crystals

Nonequivalent lanthanide defects: Energy level modeling

Microscopic Study of Dopant Distribution in Europium Doped SrGa2S4: Impact on Thermal Quenching and Phosphor Performance

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Product

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Microscopic Study of Dopant Distribution in Europium Doped SrGa₂S₄: Impact on Thermal Quenching and Phosphor Performance