APPLIED PHYSICS LETTERS 112, 132101 (2018)
Marie Anne van de Haar,1 Jan Werner,2 Nadja Kratz,2 Tom Hilgerink,1 Mohamed Tachikirt,1
Jürgen Honold,1 and Michael R. Krames3
1 Seaborough Research BV, Cruquiusweg 111C, 1019 AG Amsterdam, The Netherlands
2 Forschungsinstitut für Anorganische Werkstoffe – Glas/Keramik – GmbH, Heinrich-Meister-Str. 2, 56203 Höhr-Grenzhausen, Germany
3 Arkesso LLC, 2625 Middlefield Rd. 687, Palo Alto, California 94306, USA
(Received 22 November 2017; accepted 7 March 2018; published online 26 March 2018)
White light emitting diodes (LEDs) composed of a blue LED and a green/yellow downconverter material (phosphor) can be very efficient, but the color is often not considered very pleasant. Although the color rendering can be improved by adding a second, red-emitting phosphor, this generally results in significantly reduced efficacy of the device due to the broad emission of available conventional red-emitting phosphors. Trivalent europium is well-known for its characteristic narrow-band emission in the red region, with little radiation outside the eye sensitivity area, making it an ideal candidate for enabling high color quality as well as a high lumen equivalent of radiation from a spectrum point of view. However, a thorough study of the practical potential and challenges of Eu3+ as a red emitter for white LEDs has remained elusive so far due to the low excitation probability in the blue spectral range which is often even considered a fundamental limitation. Here, we show that the absorption in the blue region can be brought into an interesting regime for white LEDs and show that it is possible to increase both the color rendering and efficacy simultaneously using Eu3+ as a red emitter, compared to warm white LEDs comprising conventional materials.
Published by AIP Publishing. https://doi.org/10.1063/1.5016948
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