Luminescence properties of SrSi2O2N2 doped with divalent rare earth ions

Abstract

The optical properties of SrSi 2 O 2 N 2 doped with divalent Eu 2+ and Yb 2+ are investigated. The Eu 2+ doped material shows efficient green emission peaking at around 540 nm that is consistent with 4f 7 -4f 6 5d transitions of Eu 2+ . Due to the high quantum yield (90%) and high quenching temperature (4500 K) of luminescence, SrSi 2 O 2 N 2 :Eu 2+ is a promising material for application in phosphor conversion LEDs. The Yb 2+ luminescence is markedly different from Eu 2+ 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 Eu 2+ and Yb 2+ relative to the valence and conduction bands of the oxonitridosilicate host material. r

Research challenges to ultra‐efficient inorganic solid‐state lighting

“…The thermal quenching temperature of this phosphor is reported to be >500 K [4]. Thus, the oxonitridosilicates seem to be a promising alternative for SSL.…”

“…For traditional lighting technologies, CCT spans a wide range, from 2,700 K to 6,500 K or so. For incandescent lamps, the luminous efficacy of radiation (LER) 4 is higher for higher CCT (up to 6,620 K, as mentioned in Sect. 1).…”

“…6 Color rendering index A second characteristic is the ability of the white light to render the colors of objects in the environment to the hu- 3 The locus of points on the chromaticity diagram representing Planckian (or blackbody) radiation at various temperatures. 4 The luminous efficacy of radiation (LER, lm/W) is the ratio between the luminous flux (in lumens) and the optical power of radiation (in watts, W). This metric differs from a related but distinct metric, the luminous efficacy of a source (LES, lm/W), which is the ratio between the luminous flux (in lumens) and the input electrical power (in watts, W) used to produce that luminous flux.…”

“…The challenges are divided into three types: those associated with the synthesis and physics of semiconducting materials, discussed in Sect. 4; those associated with photon manipulation in materials and nanostructures, discussed in Sect. 5; and those associated with the synthesis and physics of downconversion materials, discussed in Sect.…”

Structure and luminescence of (Ca,Sr)2SiS4 : Eu2+ phosphors

“…For high-power LEDs, the LED chip can reach temperatures of 450K [19]. Unless a remote phosphor approach is used, both the emission colour and the quantum efficiency should remain stable at this elevated temperature.…”