Study of photophosphors for white LEDs

Tsvetkova, M. N.; Chernovets, B. V.; Itkinson, G. V.; Korsakov, V. G.; Sychev, M. M.

doi:10.1364/jot.78.000403

Cited by 7 publications

(2 citation statements)

References 3 publications

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“…Thus, lower conversion efficiencies cause to local high temperatures at the phosphor layer that lead to a decrease in the quantum efficiency of phosphor exponentially inducing local stress and even delamination, and ultimately degrading reliability and lifetime. [5][6][7][8] Although the heat generation is higher on the chip level compared to phosphor layer, phosphor particles may reach higher temperatures in LED systems 9,10 due to low thermal conductivity of phosphor and mixed elastomer (silicone, epoxy, etc). Therefore, a better heat removal method is preferred to distribute and remove the heat from system to ambient.…”

Section: Introductionmentioning

confidence: 99%

Investigation of combined optical and thermal effects on phosphor converted light-emitting diodes with liquid immersion cooling

2018

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The inclusion of phosphor into a high brightness light-emitting diode (LED) package is a complicated task since LEDs are encapsulated with a phosphor and epoxy mixture to convert blue photons to white light. Moreover, this common practice may cause high temperatures and fractures in the gold wire bonds of the chip or solder balls due to local heating and thermal stresses leading to device failures. Furthermore, at elevated junction temperatures, the light conversion efficiency of the phosphor reduces and decreases the overall optical efficiency of an LED. Although, remote phosphor technique has been already applied to LED systems, the high power requirements have needed better performing methods. Thus, an immersion liquid cooled remote phosphor-coated system has been proposed and experimentally and computationally investigated. First, a set of experiments was performed, which includes the combined effects coming from both optical and thermal improvements with the proposed liquid cooled remote phosphor-coated technique, where the total light extraction enhancement was obtained in excess of 25%. Then, the same problem has been computationally studied for investigation of solely optical enhancements, which has shown that remote phosphor-coated LED package with a liquid coolant of suitable refractive index at the optical path has enhanced the overall lumen performance about 13%, whereas the rest of the improvements of 12% were due to thermal enhancements.

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Section: Introductionmentioning

confidence: 99%

Investigation of combined optical and thermal effects on phosphor converted light-emitting diodes with liquid immersion cooling

2018

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“…[1][2][3][4][5][6][7][8][9][10] More and more researches have proved that the RE-doped Sialon phosphors have quantum efficiency comparable to the commercial yttrium-aluminum-garnet (YAG):Ce and silicate phosphors but with a low thermal quenching due to the rigid crystal structure of Sialon. [11][12][13] Partial substitution of Si and N with Al and O, respectively, maintains the crystal structures of Si 3 N 4 , among which a-phase is stabilized via introduction of metal ions into the interstitial sites. Our recent work using atom-resolved electron microscopy directly viewed Ce atoms locating inside the interstices in the a-structure.…”

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Atomic-scaled investigation of structure-dependent luminescence in Sialon:Ce phosphors

Sourty¹

2012

Applied Physics Letters

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Here, we present direct correlation of luminescence properties to the atomic structures of Sialon:Ce phosphors. Luminescence of β-Sialon is revealed attributed to the intergrowth of a unit layer of α-Sialon:Ce-type structure on β-grain surfaces. The dense doping at fault sites either on the surface of or inside the α-Sialon crystallites might lead to intensified emission of light depending on the fault morphology. It seems that concentration quenching would not appear for Sialon:Ce phosphors unless high density of dislocations is created upon dense doping. Finally, structural evolution has been discussed aiming to greatly enhance the luminescence of Sialon phosphors.

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Calculation of the phosphor heat generation in phosphor-converted light-emitting diodes

Luo

Qiu

2014

International Journal of Heat and Mass Transfer

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Study of photophosphors for white LEDs

Cited by 7 publications

References 3 publications

Investigation of combined optical and thermal effects on phosphor converted light-emitting diodes with liquid immersion cooling

Investigation of combined optical and thermal effects on phosphor converted light-emitting diodes with liquid immersion cooling

Atomic-scaled investigation of structure-dependent luminescence in Sialon:Ce phosphors

Calculation of the phosphor heat generation in phosphor-converted light-emitting diodes

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