Luminescence properties of SrSi2O2N2 doped with divalent rare earth ions |
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Authors: | Volker Bachmann,Thomas Jü stel,Andries Meijerink,Peter J. Schmidt |
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Affiliation: | a Philips Research Laboratories, Weisshausstr. 2, D-52066 Aachen, Germany b Department of Condensed Matter, Debye Institute, Utrecht University, P.O. Box 80 000, 3508 TA Utrecht, The Netherlands c University of Applied Sciences Münster, Stegerwaldstr. 39, D-48565 Steinfurt, Germany |
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Abstract: | The optical properties of SrSi2O2N2 doped with divalent Eu2+ and Yb2+ are investigated. The Eu2+ doped material shows efficient green emission peaking at around 540 nm that is consistent with 4f7→4f65d transitions of Eu2+. Due to the high quantum yield (90%) and high quenching temperature (>500 K) of luminescence, SrSi2O2N2:Eu2+ is a promising material for application in phosphor conversion LEDs. The Yb2+ luminescence is markedly different from Eu2+ and is characterized by a larger Stokes shift and a lower quenching temperature. The anomalous luminescence properties are ascribed to impurity trapped exciton emission. Based on temperature and time dependent luminescence measurements, a schematic energy level diagram is derived for both Eu2+ and Yb2+ relative to the valence and conduction bands of the oxonitridosilicate host material. |
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Keywords: | Luminescence conversion Divalent lanthanides Oxonitrides Phosphor converted LEDs Ytterbium Europium |
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