Correlating doping with the stability and color rendition of red phosphors†
Abstract
Although near-infrared phosphors have been widely reported, discovering efficient red-emitting phosphor materials with superior photophysical properties and high color quality is still a challenge for optimizing white light-emitting diodes (wLEDs). In this regard, a series of Eu2+ and Ce3+ doped SrS phosphors were synthesized via a one-step solid-state method at 1100 °C. The SrS:(Eu2+)n and SrS:(Ce3+)0.01,(Eu2+)n powders show substantial spectral broadening (∼80 nm) along with a significant thermal quenching resistance. The phosphor of SrS:(Eu2+)0.002 exhibits the most intense luminescence with a high color purity of 99.94% and an afterglow luminescence lasting several seconds. The luminescence intensity and peak position were modulated by the resonance-type energy transfer from Ce3+ to Eu2+ ions, which is proposed to follow the dipole–dipole interaction mechanism by Dexter's energy transfer theory and Reisfeld's approximation. The outstanding photoluminescence properties of Eu2+ are attributed to the nephelauxetic effect and crystal field splitting of rock-salt. The wLED device of SrS:(Eu2+)0.05 packaged with a blue chip and (Sr,Ba)2SiO4:Eu2+ shows a super-high color rendering index of 87.9, suggesting great potential for superior luminescence and promising wide applications.
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