Mr. Sivakumar Vaidyanathan Profile

Sivakumar Vaidyanathan

at IIT Madras

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Proceedings Article | 14 September 2005 Paper

A novel green phosphor for three band white LEDs

Sivakumar Vaidyanathan, Varadaraju Upadhyayula

Proceedings Volume 5941, 594110 (2005) https://doi.org/10.1117/12.614299

KEYWORDS: Europium, Cerium, Barium, Light emitting diodes, Luminescence, Absorption, Ions, Energy transfer, Solid state lighting, Lithium

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Current technology of lighting is Solid state lighting using LED's (SSL-LED). The aim of the present study is to find the critical concentration of Eu²⁺ for high emission intensity and also the role of Ce³⁺ co-doping on the absorption and emission properties in the host BaMgSiO₄. Photoluminescence emission of Eu²⁺ in BaMgSiO₄ when excited with 370 nm shows a broad band in the region 450 to 550 nm with a maximum at 502 nm and a shoulder at ~480 nm and one more band at ~ 400nm. The three emissions are due to Eu²⁺ in three different Ba sites in the lattice. Studies on Ba_{1 x}Eu_xMgSiO₄ [x = 0.0025 - 0.1 in steps of 0.0025] show that the emission intensity is maximum for x = 0.075 and a decrease in emission intensity is observed for higher x values. Ce³⁺ luminescence is studied for the first time in BaMgSiO₄. Ce³+ emission occurs as a broad band with maximum at 430 nm when excited with 356 nm. The Eu²⁺ excitation that occurs in the region 250 - 420 nm covers both the Ce³⁺ absorption and emission. Hence Ce³⁺ to Eu²⁺ energy transfer is possible in BaMgSiO₄. In the case of Ba_{0.99 x}Eu_0.01Ce_xMgSiO₄ [ x = 0.0025 - 0.1 ], it is observed that the emission intensity of Eu²⁺ increases with increasing Ce³⁺ content up to 0.01. This result proves the energy transfer from Ce³⁺ to Eu²⁺. Thus, the co-doping of Ce³⁺ also enhances the absorption of Eu²⁺ in the near UV to blue region where the LED emission occurs. BaMgSiO₄:Eu²⁺, Ce³⁺ with bright green emission can find potential application as a green phosphor for SSL-LED technology.

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