A novel green phosphor for three band white LEDs

Abstract

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 Eu 2+ for high emission intensity and also the role of Ce 3+ co-doping on the absorption and emission properties in the host BaMgSiO 4 . Photoluminescence emission of Eu 2+ in BaMgSiO 4 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 Eu 2+ in three different Ba sites in the lattice. Studies on Ba 1-x Eu x MgSiO 4 [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. Ce 3+ luminescence is studied for the first time in BaMgSiO 4 . Ce 3+ emission occurs as a broad band with maximum at 430 nm when excited with 356 nm. The Eu 2+ excitation that occurs in the region 250 -420 nm covers both the Ce 3+ absorption and emission. Hence Ce 3+ to Eu 2+ energy transfer is possible in BaMgSiO 4 . In the case of Ba 0.99-x Eu 0.01 Ce x MgSiO 4 [ x = 0.0025 -0.1 ], it is observed that the emission intensity of Eu 2+increases with increasing Ce 3+ content up to 0.01. This result proves the energy transfer from Ce 3+ to Eu 2+ . Thus, the co-doping of Ce 3+ also enhances the absorption of Eu 2+ in the near UV to blue region where the LED emission occurs. BaMgSiO 4 :Eu 2+ , Ce 3+ with bright green emission can find potential application as a green phosphor for SSL-LED technology.

SiO2effect on spectral and colorimetric properties of europium doped SrO2–MgO–xSiO2(0.8 ⩽x⩽ 1.6) phosphor for white LEDs

“…In 1996, the white LED combining the blue InGaN LED and the yellow-emitting phosphor YAG : Ce was first developed by Nichia [3]. Since then, the luminous efficiency of the white LEDs has rapidly improved, and an efficiency higher than traditional incandescent lamps was achieved [4]. However, the white LEDs combining blue LEDs and yellow phosphors displayed a lower colour rendering index due to the lack of red component.…”