Photoluminescence and Crystal Structure of Green-Emitting Ca[sub 3]Sc[sub 2]Si[sub 3]O[sub 12]:Ce[sup 3+] Phosphor for White Light Emitting Diodes

Abstract

We have developed a new oxide-based phosphor Ca 3 Sc 2 Si 3 O 12 :Ce 3+ , which is applicable as a green-emitting color converter for white light emitting diodes ͑LEDs͒. This phosphor absorbs blue light around 450 nm and emits green luminescence, with a peak wavelength around 505 nm. It is a promising candidate for application in LEDs as quenching of the phosphor at 150°C was smaller than that of Y 3 Al 5 O 12 :Ce yellow phosphor. A white LED with high color rendering was fabricated by combining this phosphor with a blue GaN LED and a red phosphor. The luminescence of this phosphor is derived from the 5d-4f transition of the Ce ion and the luminescence decay curve fit a single exponential function. This phosphor has a garnet-type host crystal structure. X-ray absorption fine structure analysis showed that Ce ions replaced the Ca position of the host crystal as Ce 3+ .

Controlling Ce3+ Emission Color in Silicate Garnet Phosphor

“…It is known that stabilizing a silicate garnet under ambient pressure conditions is a challenge and there are limited reports available on the synthesis of silicate garnets versus aluminate and germanate garnets (5)(6)(7). Among these, we demonstrated synthesis of a stable silicate garnet under ambient pressure conditions with RE 3+ ions partially occupying the {A} (dodecahedral) site (5).…”

Inorganic Phosphor Materials for Lighting

“…The material can be synthesized by high temperature solid state reaction under reducing atmosphere; it was thoroughly characterized from a structural and morphological point of view. The luminescence spectra demonstrate a (1 mol%), adapted from [32] very broad excitation band spanning the range 250-450 nm, and emission peaking at 502 nm with a FWHM of 70 nm. The emission intensity reaches a maximum for the 5 % sample, whilst the decay times decrease from 0.68 to 0.25 ls in the 0.5-20 % concentration range.…”

“…The quantum efficiency is high (90 % of the value observed for Ca 3 Sc 2 Si 3 O 12 :Ce 3? [32]) and the thermal stability is good. The effects of the introduction of other cations, such Mg 2?…”

“…The antisite defects are known to act as electron traps and to affect the structure, luminescence, and other properties of doped and undoped YAG. Moreover, in garnets not containing a large trivalent cation, such as Ca 3 Sc 2 Si 3 O 12 , the localization of the trivalent dopant is not generally trivial [32]. It can be concluded that it is important to get more insight on this subject.…”

“…For this reason, silicate compounds are important hosts for green emitting phosphors for pcLEDs. Shimomura et al [32] reported in 2007 on the luminescence and crystal structure of Ca 3 Sc 2 Si 3 O 12 :Ce 3? prepared by solid state reaction.…”