7 research outputs found

    Aluminate red phosphor in light-emitting diodes : theoretical calculations, charge varieties and high-pressure luminescence analysis

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    This work was supported by the Ministry of Science and Technology of Taiwan (Contract Nos. MOST 104-2113-M- 002-012-MY3 and MOST 104-2923-M-002-007-MY3). This research was also supported by National Centre for Re- search and Development, Poland (Grant No. PL- TW2/8/2015).Searching for a non-rare earth-based oxide red-emitting phosphor is crucial for phosphor-converted light- emitting diodes (LEDs). In this study, we optimized a blue and UV-light excited Sr4Al14O25:Mn phosphor exhibiting red emission peaked at ~653 nm, which was successfully synthesized by solid-state reaction. The crystal structure, micromorphology, and luminescent properties of Sr4Al14O25:Mn phosphors were characterized by X-ray Rietveld refinement, high-resolution transmission electron microscopy, and photoluminescence spectra. The band gap and electronic structure of Sr4Al14O25 were analyzed by density functional theory calculation using the hybrid exchange- correlation functional. The crystal field environment effect of Al sites from introducing activator Mn ions was investigated with the aid of Raman 27Al nuclear magnetic resonance spectra and electron spin resonance. The pressure dependent on the luminescent properties and decay time of this compound were presented. The tricolor display spectrum by combining blue InGaN chips, commercial Ξ²-SiAlON:Eu2+ green phosphor, and Sr4Al14O25:Mn red phosphor were evaluated for commercial applications: using the present Sr4Al14O25:Mn red phosphor converted LED as backlighting source.PostprintPeer reviewe

    Site-Dependent Luminescence and Thermal Stability of Eu<sup>2+</sup> Doped Fluorophosphate toward White LEDs for Plant Growth

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    Eu<sup>2+</sup> activated fluorophosphate Ba<sub>3</sub>GdNaΒ­(PO<sub>4</sub>)<sub>3</sub>F (BGNPF) with blue and red double-color emitting samples were prepared via a solid-state method in a reductive atmosphere. Their crystal structure and cationic sites were identified in light of X-ray diffraction pattern Rietveld refinement. Three different Ba<sup>2+</sup> sites, coordinated by six O atoms referred to as Ba1, two F and five O atoms as Ba2, and two F and six O atoms as Ba3, were partially substituted by Eu<sup>2+</sup>. Photoluminescence emission (PL) and excitation (PLE) spectra of phosphor BGNPF:Eu<sup>2+</sup> along with the lifetimes were characterized at the liquid helium temperature (LHT), which further confirm the existence of three Eu<sup>2+</sup> emitting centers resulting in 436, 480, and 640 nm emission from the 5d β†’ 4f transitions of Eu<sup>2+</sup> in three different Ba<sup>2+</sup> crystallographic sites. These emissions overlap with the absorption spectra of carotenoids and chlorophylls from plants, which could directly promote the photosynthesis. Temperature-dependent PL spectra were used to investigate the thermal stability of phosphor, which indicates that the PL intensity of BGNPF:0.9% Eu<sup>2+</sup> with optimal composition at 150 Β°C still keeps 60% of its PL intensity at room temperature, in which blue emission has higher thermal-stability than the red emission. Furthermore, the approaching white LED devices have also been manufactured with a 365 nm n-UV LED chip and present phosphor, which make operators more comfortable than that of the plant growth purple emitting LEDs system composed of blue and red light. Results indicate that this phosphor is an attractive dual-responsive candidate phosphor in the application n-UV light-excited white LEDs for plant growth

    Aluminate red phosphor in light-emitting diodes:theoretical calculations, charge varieties and high-pressure luminescence analysis

    No full text
    Searching for a non-rare earth-based oxide red-emitting phosphor is crucial for phosphor-converted light- emitting diodes (LEDs). In this study, we optimized a blue and UV-light excited Sr4Al14O25:Mn phosphor exhibiting red emission peaked at ~653 nm, which was successfully synthesized by solid-state reaction. The crystal structure, micromorphology, and luminescent properties of Sr4Al14O25:Mn phosphors were characterized by X-ray Rietveld refinement, high-resolution transmission electron microscopy, and photoluminescence spectra. The band gap and electronic structure of Sr4Al14O25 were analyzed by density functional theory calculation using the hybrid exchange- correlation functional. The crystal field environment effect of Al sites from introducing activator Mn ions was investigated with the aid of Raman 27Al nuclear magnetic resonance spectra and electron spin resonance. The pressure dependent on the luminescent properties and decay time of this compound were presented. The tricolor display spectrum by combining blue InGaN chips, commercial Ξ²-SiAlON:Eu2+ green phosphor, and Sr4Al14O25:Mn red phosphor were evaluated for commercial applications: using the present Sr4Al14O25:Mn red phosphor converted LED as backlighting source
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