Selecting Conversion Phosphors for White Light-Emitting Diodes

Smet, Philippe; Parmentier, Anthony; Poelman, Dirk

doi:10.1149/1.3568524

Cited by 677 publications

(506 citation statements)

References 155 publications

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“…These europium doped oxynitrides have been proposed as excellent conversion phosphors for white-light-emitting LED applications based on near ultraviolet (UV) to blue emitting InGaN LEDs [18]. Persistent luminescence in europium doped MSi 2 O 2 N 2 (with M = Ba, Sr, Ca) has been reported recently [19].…”

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confidence: 99%

Mechanoluminescence in BaSi2O2N2:Eu

et al. 2012

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Mechanoluminescence (ML), a general term for the phenomenon in which light emission occurs during any mechanical action on a solid, can be divided roughly into two classes: destructive ML and non-destructive ML. For practical use in high-end applications (e.g. pressure sensors), materials with non-destructive ML properties are preferred. This paper reports on the strong non-destructive ML in BaSi 2 O 2 N 2 :Eu. When irradiated in advance with UV or blue light, this phosphor shows intense blue-green light emission upon mechanical stimulation such as friction or pressure. The ML has an emission band peaking at 498 nm, which is about 4 nm red-shifted compared to the steady state photoluminescence. The origin of the ML is discussed and related to the persistent luminescence of BaSi 2 O 2 N 2 :Eu. The same traps are responsible for both the phenomena.Based on the occurrence of ML in this phosphor, we were able to derive that the predominant crystallographic structure of BaSi 2 O 2 N 2 :Eu belongs to space group Cmc2 1 .

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Mechanoluminescence in BaSi2O2N2:Eu

et al. 2012

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“…T 0.5 is a parameter which is typically used to quantify the bulk performance of a phosphor. 3 In this equation, A is given by the ratio of the radiative and non-radiative decay rates of the excited state governing the luminescence. Despite the careful alignment of the CL maps for different temperatures, some pixel groups can still suffer from a bad alignment.…”

Section: Resultsmentioning

confidence: 99%

“…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.…”

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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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“…43 However, the relatively narrow lines in the NUV part of the excitation spectrum are not ideal for WLED application. The emission spectrum of the pumping LED changes slightly due to variations in the driving current and/or the junction temperature.…”

Section: Discussionmentioning

confidence: 99%

Octoxy capped Si nanoparticles synthesized by homogeneous reduction of SiCl₄with crown ether alkalide

et al. 2014

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Modified Pechini synthesis routes were developed for synthesis of the novel red phosphor materials NaLa(WO4)(MoO4):Eu 3+ and Ba2CaMoO6:Eu 3+ . Phase pure NaLa(WO4)(MoO4):Eu 3+ was obtained at calcination temperature ≥ 600 °C using malic acid or tartaric acid as complexing agents. Phase pure Ba2CaMoO6:Eu 3+ was attained using EDTA and citric acid, at calcination temperature ≥ 800 °C. Choice of complexing agents were discussed on the basis of precursor solubility, metal complex stability constants and conformations of the complexes. The powder properties were characterised using X-ray diffraction, thermal analysis and electron microscopy. Photoluminescence emission intensity was studied as a function of the complexing agents used and calcination temperature of the powders. Maximum emission intensity for NaLa(WO4)(MoO4):Eu 3+ was obtained at a calcination temperature of 600 °C.

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Selecting Conversion Phosphors for White Light-Emitting Diodes

Cited by 677 publications

References 155 publications

Mechanoluminescence in BaSi2O2N2:Eu

Mechanoluminescence in BaSi2O2N2:Eu

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

Octoxy capped Si nanoparticles synthesized by homogeneous reduction of SiCl₄with crown ether alkalide

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Selecting Conversion Phosphors for White Light-Emitting Diodes

Cited by 677 publications

References 155 publications

Mechanoluminescence in BaSi2O2N2:Eu

Mechanoluminescence in BaSi2O2N2:Eu

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

Octoxy capped Si nanoparticles synthesized by homogeneous reduction of SiCl4with crown ether alkalide

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

Octoxy capped Si nanoparticles synthesized by homogeneous reduction of SiCl₄with crown ether alkalide