Abstract
Rapid development of solid-state lighting technology requires new materials with highly efficient and stable luminescence, and especially relies on blue light pumped red phosphors for improved light quality. Herein, we discovered an unprecedented red-emitting Mg2Al4Si5O18:Eu2+ composite phosphor (λex = 450 nm, λem = 620 nm) via the crystallization of MgO–Al2O3–SiO2 aluminosilicate glass. Combined experimental measurement and first-principles calculations verify that Eu2+ dopants insert at the vacant channel of Mg2Al4Si5O18 crystal with six-fold coordination responsible for the peculiar red emission. Importantly, the resulting phosphor exhibits high internal/external quantum efficiency of 94.5/70.6%, and stable emission against thermal quenching, which reaches industry production. The maximum luminous flux and luminous efficiency of the constructed laser driven red emitting device reaches as high as 274 lm and 54 lm W−1, respectively. The combinations of extraordinary optical properties coupled with economically favorable and innovative preparation method indicate, that the Mg2Al4Si5O18:Eu2+ composite phosphor will provide a significant step towards the development of high-power solid-state lighting.
Highlights
Solid-state lighting (SSL) has advanced rapidly over the past decades, and will definitely dominate the future lighting market[1,2,3]
Glass is a thermodynamically metastable solid. After it is heat-treated for a sufficiently long time at higher than glass transition temperature Tg, it will enter into super-cooled state, and glass structure relaxation could occur, leading to the movement/diffusion of multiple structural building blocks simultaneously or atomic rearrangements orderly
Aluminosilicate precursor glass (PG) with the nominal chemical composition of 2MgOAl2O3−3SiO2, which is at the boundary between cordierite and spinel (Fig. 1b), was specially designed and prepared via meltquenching method
Summary
Solid-state lighting (SSL) has advanced rapidly over the past decades, and will definitely dominate the future lighting market[1,2,3]. The current standard architecture for SSL is the phosphor-converted light-emitting diode (pcLED), where the blue LED chip is covered with one or more down-shifting phosphors dispersed in organic binder to produce composite white light[4,5,6,7] Despite those spectacular success in the pc-LED, the notorious “efficiency drop”, that is nonthermal drop in efficiency with increasing input power density[8,9] precludes pc-LED operation in the fields, where high luminance and various types of bulk phosphors have been designed and constructed successfully so far, almost all reports are limited to Ce3+-doped garnet-type yellow-emitting PiG/ceramic composite phosphors[17,18]. The reasons are (1) CaAlSiN3:Eu2+ phosphor unavoidably suffers from erosion when co-sintering it with glass frit at hightemperature[17], which leads an inferior luminescent performance, viz., a lower quantum efficiency and stronger thermal emission quenching compared with the fresh CaAlSiN3:Eu2+ phosphor powder. (2) The construction of ceramic is strictly constrained by high-pressure and highvacuum conditions[15,18,22], and such complex and economically unfavorable preparation processes hinder it from industrial production
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