Laser excitation of red, green, blue and trichromatic white rare-earth phosphors for solid-state lighting applications (original) (raw)
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Dy 3+-doped CaAl 12 O 19 phosphors were synthesized utilizing a combustion method. Crystal structure and morphological examinations were performed respectively using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques to identify the phase and morphology of the synthesized samples. Fourier transform infrared spectroscopy (FTIR) estimations were carried out using the KBr method. Photoluminescence properties (excitation and emission) were recorded at room temperature. CaAl 12 O 19 :Dy 3+ phosphor showed two emission peaks respectively under a 350-nm excitation wavelength, centered at 477 nm and 573 nm. Dipole-dipole interaction via nonradiative energy shifting has been considered as the major cause of concentration quenching when Dy 3+ concentration was more than 3 mol%. The CIE chromaticity coordinates positioned at (0.3185, 0.3580) for the CaAl 12 O 19 :0.03Dy 3+ phosphor had a correlated color temperature (CCT) of 6057 K, which is situated in the cool white area. Existing results point out that the CaAl 12 O 19 :0.03Dy 3+ phosphor could be a favorable candidate for use in white light-emitting diodes (WLEDs). KEYWORDS aluminate, concentration quenching, Dy 3 + , photoluminescence, WLEDs 1 | INTRODUCTION At the present time, the development of energy-saving lighting is an essential core interest for researchers. Large amounts of power can be saved by using efficient energy-saving light sources. Traditional incandescent and fluorescent lamps, with their resulting heat or gas release, have related colossal energy losses. [1] The use of energy proficient solid-state lighting appliances, for example compact fluorescent lamps (CFLs) and light-emitting diodes (LEDs), to deliver white light is an attractive alternative. Due to the above concern, the production of phosphors with excellent properties is an essential prerequisite. The efficacy of white light-emitting diodes (WLEDs) has surpassed that of incandescent lamps and fluorescent lamps. Due to their exceptional luminescence features, improved stability, energy-efficient nature, prominent luminescence efficiency, ecological amicability, and low cost, research into WLEDs has become more important. [2-4] WLEDs are mostly fabricated by applying three different techniques: (i) by making use of a mixture of red-green-blue (RGB) LEDs; (ii) through the utilization of ultraviolet (UV) LEDs to excite RGB phos-phors; and (iii) by employing blue LEDs to pump single-phase yellow or blended green and red phosphors. [1,5] At the present time, blue emitting chips combined with yellow phosphors (YAG:Ce 3+) are acknowledged as existing industrial WLEDs. Nevertheless, inferable from red light effect insufficiency, low color rendering index and high correlated color temperature (CCT) are commonly experienced by phosphors in this group. High CCT and low color rendering index (CRI) are not good factors when providing domiciliary or office lighting. This hindrance can be resolved by utilizing tricolor WLEDs dependent on red, green, and blue phosphors [6-8]. This purpose can be achieved by spreading these three phosphors on a transpicuous silicone that is then enclosed and then combined with blue or UV chips to excite the phosphors [1]. This factor is a major obstacle in field of materials science for the
Bulletin of Electrical Engineering and Informatics, 2023
Researchers propose the phosphors emit many colors SrMg2La2W2O12:Tb3+, Sm3+, Tm3+ (SMLLW:RE3+) (RE3+=Tb3+, Sm3+, Tm3+) synthesized using the solid-status reacting technique as promising downward-transformation luminous substances for diodes emit white illumination and screens in the current study. The structural and binding data given by X-ray diffraction (XRD) data and fourier transform infrared (FTIR) spectroscopy suggest the corresponding orthorhombic configuration and vibrational powers, respectively. The stimulation and radiation bands of color of SMLLW:RE 3+ phosphor show that such phosphors may be successfully stimulated via ultraviolet (UV) illumination and generate green, orange-red, and blue (stands for G, OR , B) illumination, in turn. For different doses of the triggers Tb3+, Sm3+, and Tm3+ within the SMLW phosphor base, luminescence, decomposition periods, Commission Internationale De L'eclairage (CIE) color coordination, along with correlated hue heats (Tcct) are specified. When a triple-doped SMLW phosphor is activated using a ligand-to-metal charge transition (LMCT), it produces G, OR , B hues at the same time and can be adjustable to white light, according to the results. An effective power transfer among rare-earth ions was found and investigated using decay curve analysis. According to the findings, SMLW:RE3+ (RE=Tb, Sm, Tm) are suitable options to use for light-emitting diodes (LEDs) and screens creation.
Indonesian Journal of Electrical Engineering and Computer Science
Using a high temperature solid-state technique, various phosphors Sr4La(PO4)3O:Ce3+, Tb3+,Mn2+ (SLPO:Ce,Tb,Mn) were produced. In Sr4La(PO4)3O, the luminescence characteristics, thermal stability, and energy conversion between Ce3+ and Tb3+-Mn2+ have been thoroughly studied. The sensitizer Ce3+ particles inclusion could considerably improve the feeble Tb3+ green radiation and Mn2+ red radiation via energy transfer. By adjusting the scale of Ce3+/Tb3+ over Ce3+/Mn2+ atoms, the color of the emission may be changed. White light was produced in the Sr4La(PO4)3O:0.12Ce3+,0.3Mn2+ specimen with chromatism coordinates of (0.3326, 0.3298), showing that the phosphors SLPO:Ce,Tb,Mn possess promising application on WLEDs. The conclusion is supported by Mie-scattering theory and Lambert-Beer's law.
Application of green-emitting Sr3WO6:U phosphor to enhance lumen efficiency of WLEDs
Bulletin of Electrical Engineering and Informatics, 2022
The article demonstrates a sample of spectrum in the phosphor-covered WLED (abbreviated as p-WLED) containing one blue chip, one red chip along with phosphors of green and yellow colors. We acquired the p-WLEDs' ideal spectrum in the CCTs, which is short for correlated color temperature range from 2700 K to 6500 K using a nonlinear program in order to optimize the radiation's lumen efficiency (LER) when the R9 strong red's color rendering indexes (CRIs) and special CRIs exceed 98. From the outcomes of the recreation, p-WLEDs containing an InGaN blue chip with 450 nm wavelength, an AlGaInP red chip with 634 nm wavelength, along with green and yellow silicate phosphors with the value of 507 and 580 nm wavelength correspondingly; can produce white lights with CRI values of around 98 and particular CRI values of R9 for intense reds above 98. For saturated red, yellow, green, and blue colors, the average values of the particular CRIs R9 through R12 exceed 95. In CCT values of 2700 K to 6500 K, the R13 value in female figures is around 100, with LER values reaching 296 lm/W.
Functional Materials Letters, 2013
The aim of the present investigation was to develop a phosphor to solve the flickering luminescence of alternating current (AC) lightemitting diodes (LED) by compensating the dark duration with appropriately persistent luminescence. The phosphor SrAl 2 O 4 :Eu 2þ co-doped with Y 3þ or Dy 3þ was synthesized via solid-state reaction with H 3 BO 3 as flux. The crystal structure and morphology were characterized by using X-ray diffraction (XRD) and Scanning Electron Microscope (SEM), respectively. The photoluminescence spectra were collected with a fluorescence spectrometer. The results demonstrated that appropriate amount of Y 3þ or Dy 3þ doped was beneficial to suppress the by-product of Sr 4 Al 14 O 25 which easily co-existed with the SrAl 2 O 4 phase brought by the flux of H 3 BO 3 . However, too much Y 3þ or Dy 3þ doped resulted in the formation of another impurity phase, i.e., the yttrium aluminum garnet of Y 3 Al 5 O 12 and Dy 3 Al 5 O 12 . Comparatively, the doped Dy 3þ was more helpful in prolonging the persistent luminescence, while Y 3þ was more efficient in enhancing luminescence intensity. To demonstrate the feasibility of the phosphor applied in AC LEDs, a nearly white AC LED was fabricated by coating the phosphor on a blue AC LED chip. The persistent luminescence was radiated from the AC LED device after turning power off. Moreover, the effect of the phosphor on compensating the AC LED dark duration through persistent luminescence was revealed by using the Keyence VW-9000 High-speed Microscope for the first time.
Luminescence in the Concentrated Phosphor
Radiation Measurements, 2007
Powder samples of EuAl 2 O 4 and (Eu, Sr)Al 2 O 4 with a quantum efficiency (QE) of the Eu 2+ emission more than 0.30 were synthesized. A modified method of QE determination is described and results of the QE measurements for EuAl 2 O 4 , (Eu 0.8 Sr 0.2 )Al 2 O 4 , (Eu 0.65 Sr 0.35 )Al 2 O 4 , and a diluted sample (Sr 0.98 Eu 0.02 )Al 2 O 4 are presented. Excitation and emission spectra as well as decay behaviour of the Eu 2+ luminescence in (Eu 1−x Sr x )Al 2 O 4 in the temperature region of 20-300 K are studied. It is concluded that the main reason for the high QE is a pronounced relaxation of the crystal lattice after excitation of the Eu 2+ ions resulting in an emission with a large Stokes shift and, therefore, in a restriction of energy migration. Eu ions occupying the crystallographic sites with the higher coordination number (Eu II ) are supposed to be the luminescence centres in (EuSr)Al 2 O 4 lattice.
Phosphors for Solid-State White Lighting
Since the mid-1990s, phosphors have played a key role in emerging solid-state white-lighting technologies that are based on combining a III-nitride-based near-UV or blue solid-state light source with downconversion to longer wavelengths. Almost all widely used phosphors comprise a crystalline oxide, nitride, or oxynitride host that is appropriately doped with either Ce3+ or Eu2+. These ions, with [Xe] 4f(n)5d(0) configurations (n = 1 for Ce3+ and 7 for Eu2+) have proximal excited states that are [Xe] 4f(n-1)5d(1). Optical excitation into these states and concomitant reemission can be tuned into the appropriate regions of the visible spectrum by the crystal these ions are hosted in. In this article, we review the current needs and key aspects of the conversion process. We describe some currently used families of phosphors and consider why they are suitable for solid-state lighting. Finally, we describe some empirical rules for new and improved host materials.
Eu3+-activated potential red-emitting phosphor for solid-state lighting
Optik, 2017
The intense red-emitting NaCaY0.2Eu0.8(MoO4)3 phosphor was prepared by using a sol-gel method for the first time. Thermogravimetric-diferential thermal analysis, X-ray diffraction, field-emission scanning electron microscopy, FT-IR and luminescent measurements were used to characterize the NaCaY0.2Eu0.8(MoO4)3 particles. The resulting products obtained by using the sol-gel method have a narrower size distribution and a more regular particle shape than those obtained by using the solid-state reaction. The spectra analysis indicated that the obtained phosphor could be excited by UV light of 395 nm and visible light of 466 nm, also emits intense red light with a maximum at about 614 nm. The luminescent intensity of sol-gel derived is comparable with the solid state product and it is about 84 % of solid-state product under 395 nm light excitation. Comparative study with YAG:Ce and CaS:Eu 2+ phosphors, suggested that our synthesized phosphor can be used as an efficient red-emitting phosphor to compensate the red deficiency of YAG:Ce phosphor and also can serve as an alternative phosphor to replace sulfide based phosphors in the solid-state lighting applications.