Synthesis, energy transfer and tunable emission properties of SrSb2O6:Eu3 +, Bi3 + phosphor

NASA Astrophysics Data System (ADS)

Cao, Renping; Fu, Ting; Peng, Dedong; Cao, Chunyan; Ruan, Wen; Yu, Xiaoguang

2016-12-01

Host SrSb2O6, SrSb2O6:Bi3 +, SrSb2O6:Eu3 +, and SrSb2O6:Eu3 +, Bi3 + phosphors are synthesized by solid state reaction method in air. Host SrSb2O6 with excitation 254 nm shows weak green-yellow emission in the range of 320-780 nm due to Sb5 + → O2- transition. SrSb2O6:Bi3 + phosphor with excitation 365 nm emits green light within the range 400-650 nm owing to the 3P1 → 1S0 transition of Bi3 + ion. SrSb2O6:Eu3 + phosphor with excitation 254 nm exhibits a systematically varied hue from green to orange-red light by increasing Eu3 + concentration from 0 to 7 mol%, and that with excitation 394 nm only shows orange-red light. The optimal Eu3 + concentration is 4 mol% in SrSb2O6:Eu3 + phosphor. SrSb2O6:Eu3 +, Bi3 + phosphor with excitation 254 and 394 nm emits orange-red light. Emission intensity of SrSb2O6:Eu3 + phosphor may be enhanced > 2 times by co-doping Bi3 + ion because of the fluxing agent and energy transfer roles of Bi3 + ion in SrSb2O6:Eu3 +, Bi3 + phosphor. The luminous mechanism of SrSb2O6:Eu3 +, Bi3 + phosphor is analyzed and explained by the simplified energy level diagrams of Sb2O62 - group, Bi3 + and Eu3 + ions, and energy transfer processes between them.

Structure, luminescence and thermal quenching properties of Eu doped Sr2-xBaxSi5N8 red phosphors

NASA Astrophysics Data System (ADS)

Liu, Y. H.; Chen, L.; Zhou, X. F.; Liu, R. H.; Zhuang, W. D.

2017-02-01

Eu2+ doped Sr2-xBaxSi5N8 phosphors were synthesized at 1610 ℃ for 4 h via the solid-state reaction method. The XRD results confirm that the complete solid solutions are formed. With the increase of x, the emission spectra show an obvious blue-shift from 610 nm to 585 nm under the excitation of 460 nm. The color tone can be tuned from yellow to red. The corresponding mechanism for the blue-shift of peak-wavelength is studied in detail. The results of decomposed Gaussian spectra and fluorescence lifetime show that the local coordination structure surrounding activator ions changes with increasing x value. It is found that the probability of Eu occupying Sr1 and Sr2 site is dependent on Ba/Sr ratio. The variation of thermal quenching properties and the corresponding mechanism is discussed in detail. The results indicate that Eu2+ doped Sr2-xBaxSi5N8 is a promising orange red-emitting phosphor for near UV or blue light-pumped white light-emitting-diodes (wLEDs).

Synthesis and Luminescence Properties of Rare Earth Activated Phosphors for near UV-Emitting LEDs for Efficacious Generation of White Light

NASA Astrophysics Data System (ADS)

Han, Jinkyu

Solid state white-emitting lighting devices based on LEDs outperform conventional light sources in terms of lifetime, durability, and luminous efficiency. Near UV-LEDs in combination with blue-, green-, and red-emitting phosphors show superior luminescence properties over the commercialized blue-emitting LED with yellow-emitting phosphors. However, phosphor development for near UV LEDs is a challenging problem and a vibrant area of research. In addition, using the proper synthesis technique is an important consideration in the development of phosphors. In this research, efficient blue-, green-yellow, red-emitting, and color tunable phosphors for near UV LEDs based white light are identified and prepared by various synthetic methods such as solid state reaction, sol-gel/Pechini, co-precipitation, hydrothermal, combustion and spray-pyrolysis. Blue-emittingLiCaPO4:Eu2+, Green/yellow-emitting (Ba,Sr)2SiO4:Eu2+, color tunable solid solutions of KSrPO4-(Ba,Ca)2SiO4:Eu 2+, and red-emitting (Ba,Sr,Ca)3MgSi2O 8:Eu2+,Mn2+ show excellent excitation profile in the near UV region, high quantum efficiency, and good thermal stability for use in solid state lighting applications. In addition, different synthesis methods are analyzed and compared, with the goal of obtaining ideal phosphors, which should have not only have high luminous output but also optimal particle size (˜150--400 nm) and spherical morphology. For Sr2SiO 4:Eu2+, the sol-gel method appears to be the best method. For Ba2SiO4:Eu2+, the co-precipitation method is be the best. Lastly, the fabrication of core/SiO2 shell particles alleviate surface defects and improve luminescence output and moisture stability of nano and micron sized phosphors. For nano-sized Y2O 3:Eu3+, Y2SiO5:Ce3+,Tb 3+, and (Ba,Sr)2SiO4, the luminescence emission intensity of the core/shell particles were significantly higher than that of bare cores. Additionally, the moisture stability is also improved by SiO 2 shells, the luminescence output of

Tunable Yellow-Red Photoluminescence and Persistent Afterglow in Phosphors Ca4LaO(BO3)3:Eu3+ and Ca4EuO(BO3)3.

PubMed

Chen, Zhen; Pan, Yuexiao; Xi, Luqing; Pang, Ran; Huang, Shaoming; Liu, Guokui

2016-11-07

In most Eu 3+ activated phosphors, only red luminescence from the 5 D 0 is obtainable, and efficiency is limited by concentration quenching. Herein we report a new phosphor of Ca 4 LaO(BO 3 ) 3 :Eu 3+ (CLBO:Eu) with advanced photoluminescence properties. The yellow luminescence emitted from the 5 D 1,2 states is not thermally quenched at room temperature. The relative intensities of the yellow and red emission bands depend strongly on the Eu 3+ doping concentration. More importantly, concentration quenching of Eu 3+ photoluminescence is absent in this phosphor, and the stoichiometric compound of Ca 4 EuO(BO 3 ) 3 emits stronger luminescence than the Eu 3+ doped compounds of CLBO:Eu; it is three times stronger than that of a commercial red phosphor of Y 2 O 3 :Eu 3+ . Another beneficial phenomenon is that ligand-to-metal charge transfer (CT) transitions occur in the long UV region with the lowest charge transfer band (CTB) stretched down to about 3.67 eV (∼330 nm). The CT transitions significantly enhance Eu 3+ excitation, and thus result in stronger photoluminescence and promote trapping of excitons for persistent afterglow emission. Along with structure characterization, optical spectra and luminescence dynamics measured under various conditions as a function of Eu 3+ doping, temperature, and excitation wavelength are analyzed for a fundamental understanding of electronic interactions and for potential applications.

Orange-red emitting Gd2Zr2O7:Sm3+: Structure-property correlation, optical properties and defect spectroscopy

NASA Astrophysics Data System (ADS)

Gupta, Santosh K.; Reghukumar, C.; Sudarshan, K.; Ghosh, P. S.; Pathak, Nimai; Kadam, R. M.

2018-05-01

Local structure analysis of dopant ion, understanding host to dopant energy transfer dynamics and defects characterization in a doped material which plays an important role in the designing a highly efficient opto-electronic material. In this connection a new Sm3+ doped Gd2Zr2O7 pyrochlore material was synthesized using gel-combustion technique and was characterized systematically using X-ray diffraction (XRD), time resolved photoluminescence spectroscopy (TRPLS), positron annihilation lifetime spectroscopy (PALS) and density functional theory (DFT) based ab-initio calculation. Based on DFT site selective energetics calculation and luminescence decay measurement, it was observed that the Sm3+ was distributed at both Gd3+ and Zr4+ site with higher Sm3+ fraction at the Gd3+ site. PALS was used to probe the presence of defects in the phosphor. In this work intense orange-red emission is realized through manipulating the energy transfer from host defect emission (oxygen vacancies) to Sm3+ which allows color emission from green in undoped to orange-red in doped samples. Effect of dopant concentration and annealing temperature was probed using TRPLS and PALS. These all information is highly important for researcher looking to achieve pyrochlore based phosphor materials with high quantum yield.

Low temperature solution process-based defect-induced orange-red light emitting diode

PubMed Central

Biswas, Pranab; Baek, Sung-Doo; Hoon Lee, Sang; Park, Ji-Hyeon; Jeong Lee, Su; Il Lee, Tae; Myoung, Jae-Min

2015-01-01

We report low-temperature solution-processed p-CuO nanorods (NRs)/n-ZnO NRs heterojunction light emitting diode (LED), exploiting the native point defects of ZnO NRs. ZnO NRs were synthesized at 90 °C by using hydrothermal method while CuO NRs were synthesized at 100 °C by using microwave reaction system. The electrical properties of newly synthesized CuO NRs revealed a promising p-type nature with a hole concentration of 9.64 × 1018 cm−3. The current-voltage characteristic of the heterojunction showed a significantly high rectification ratio of 105 at 4 V with a stable current flow. A broad orange-red emission was obtained from the forward biased LED with a major peak at 610 nm which was attributed to the electron transition from interstitial zinc to interstitial oxygen point defects in ZnO. A minor shoulder peak was also observed at 710 nm, corresponding to red emission which was ascribed to the transition from conduction band of ZnO to oxygen vacancies in ZnO lattice. This study demonstrates a significant progress toward oxide materials based, defect-induced light emitting device with low-cost, low-temperature methods. PMID:26648420

The development of Ce3+-activated (Gd,Lu)3Al5O12 garnet solid solutions as efficient yellow-emitting phosphors

NASA Astrophysics Data System (ADS)

Li, Jinkai; Li, Ji-Guang; Liu, Shaohong; Li, Xiaodong; Sun, Xudong; Sakka, Yoshio

2013-10-01

Ce3+-activated Gd3Al5O12 garnet, effectively stabilized by Lu3+ doping, has been developed for new yellow-emitting phosphors. The powder processing of [(Gd1-xLux)1-yCey]3Al5O12 solid solutions was achieved through precursor synthesis via carbonate precipitation, followed by annealing. The resultant (Gd,Lu)AG:Ce3+ phosphor particles exhibit typical yellow emission at ˜570 nm (5d-4f transition of Ce3+) upon blue-light excitation at ˜457 nm (the 2F5/2-5d transition of Ce3+). The quenching concentration of Ce3+ was determined to be ˜1.0 at% (y = 0.01) and the quenching mechanism was suggested to be driven by exchange interactions. The best luminescent [(Gd0.9Lu0.1)0.99Ce0.01]AG phosphor is comparative to the well-known YAG:Ce3+ in emission intensity but has a substantially red-shifted emission band that is desired for warm-white lighting. The effects of processing temperature (1000-1500 °C) on the spectroscopic properties of the phosphors, especially those of Lu3+/Ce3+, were thoroughly investigated and discussed from the centroid position and crystal field splitting of the Ce3+ 5d energy levels.

A novel orange-red emitting NaCaVO{sub 4}:Sm{sup 3+} phosphor for solid state lighting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biswas, Pankaj, E-mail: pankaj79biswas@gmail.com; Kumar, Vinay, E-mail: vinaykdhiman@yahoo.com; Ntwaeaborwa, O. M.

2016-05-06

The samarium doped NaCaVO{sub 4} phosphor was synthesized by the combustion method. The X-ray powder diffraction (XRD) analysis confirmed that the phosphor powder crystallized as orthorhombic structure belonging to space group Cmcm. From Williamson-Hall analysis the grain size and microstrain in the powder was estimated. The Fourier- transform infrared (FT-IR) studies further validated the formation of vanadate phase of the phosphor. Photoluminescence (PL) study revealed that the phosphor could be efficiently excited by UV-VIS from 200 nm to 500 nm. The 565 nm, 602 nm, 648 nm and 713 nm emissions were ascribed to {sup 4}G{sub 5/2} to {sup 6}H{submore » J} (J = 5/2, 7/2, 9/2 and 11/2) transitions of the Sm{sup 3+} ion. The present material may be explored as a novel phosphor to be excited by UV light emitting diodes (LEDs) chips for solid-state lighting and display applications.« less

Red carbon dots-based phosphors for white light-emitting diodes with color rendering index of 92.

PubMed

Zhai, Yuechen; Wang, Yi; Li, Di; Zhou, Ding; Jing, Pengtao; Shen, Dezhen; Qu, Songnan

2018-05-29

Exploration of solid-state efficient red emissive carbon dots (CDs) phosphors is strongly desired for the development of high performance CDs-based white light-emitting diodes (WLEDs). In this work, enhanced red emissive CDs-based phosphors with photoluminescence quantum yields (PLQYs) of 25% were prepared by embedding red emissive CDs (PLQYs of 23%) into polyvinyl pyrrolidone (PVP). Because of the protection of PVP, the phosphors could preserve strong luminescence under long-term UV excitation or being mixed with conventional packaging materials. By applying the red emissive phosphors as the color conversion layer, WLEDs with high color rendering index of 92 and color coordinate of (0.33, 0.33) are fabricated. Copyright © 2018 Elsevier Inc. All rights reserved.

Red-emitting phosphor Rb2TiF6:Mn4+ with high thermal-quenching resistance for wide color-gamut white light-emitting diodes

NASA Astrophysics Data System (ADS)

Wang, Zhengliang; Yang, Zhiyu; Tan, Huiying; Brik, Mikhail G.; Zhou, Qiang; Chen, Guo; Liang, Hongbin

2017-10-01

Red-emitting phosphor plays a critical role in improving performance of the phosphor-converted white light-emitting diodes (pc-WLEDs). Herein, a red-emitting phosphor, Rb2TiF6:Mn4+, was synthesized via the ion exchange method under mild condition. The crystal structure and morphology were characterized by the powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The Rietveld refinements of Rb2TiF6:Mn4+ indicate that this sample is of single phase with hexagonal crystal structure. The as-prepared Rb2TiF6:Mn4+ has sharp red emissions with broad excitation band at ∼460 nm. The luminescent behavior of Mn4+ was discussed in detail. The temperature-dependent emission spectra of Rb2TiF6:Mn4+ indicate that this phosphor shares high thermal quenching resistance and excellent color stability. A series of WLEDs with tunable color rendering index and color temperature were fabricated by combining commercial Y3Al5O12:Ce3+ and Rb2TiF6:Mn4+ on blue GaN-LED chips. With the addition of Rb2TiF6:Mn4+, WLED with wide gamut was obtained with low color temperature (3123 K), high color rendering index (91.5) and high luminous efficacy (187.9 lm/W). These findings show this phosphor could be a promising commercial red phosphor in wide color-gamut WLEDs.

The synthesis and luminescence properties of a novel red-emitting phosphor: Eu3+-doped Ca9La(PO4)7

NASA Astrophysics Data System (ADS)

Liang, Zehui; Mu, Zhongfei; Wang, Qiang; Zhu, Daoyun; Wu, Fugen

2017-10-01

A series of novel red-emitting phosphors Ca9La1- x (PO4)7: xEu3+ were synthesized by high-temperature solid state reactions. The photoluminescence excitation and photoluminescence spectra of these phosphors were investigated in detail. O2--Eu3+ charge transfer band peaking at about 261 nm is dominant in the PLE spectra of Eu3+-doped Ca9La(PO4)7, indicating that the phosphors are suitable for tricolor fluorescent lamps. The phosphors also show a good absorption in near ultraviolet (around 395 nm) and blue (around 465 nm) spectral region, which indicates that it can be pumped with NUV and blue chips for white light-emitting diodes. The transition of 5D0 → 7F2 of Eu3+ in this lattice can emit bright red light. Ca9La(PO4)7 could accommodate a large amount of Eu3+ with an optimal concentration of 60 mol%. The dipole-dipole interaction between Eu3+ is the dominant mechanism for concentration quenching of Eu3+. The calculated color coordinates lie in red region ( x = 0.64, y = 0.36), which is close to Y2O3: 0.05Eu3+ ( x = 0.65, y = 0.34). The integral emission intensity of Ca9La0.4(PO4)7: 0.6Eu3+ is 1.9 times stronger than that of widely used commercial red phosphor Y2O3: 0.05Eu3+. All these results indicate that Eu3+-doped Ca9La(PO4)7 is a promising red-emitting phosphor which can be used in tricolor fluorescent lamps and white light-emitting diodes.

Novel rare-earth-free yellow Ca5Zn3.92In0.08(V0.99Ta0.01O4)6 phosphors for dazzling white light-emitting diodes

PubMed Central

Pavitra, E.; Raju, G. Seeta Rama; Park, Jin Young; Wang, Lili; Moon, Byung Kee; Yu, Jae Su

2015-01-01

White light-emitting diode (WLED) products currently available on the market are based on the blue LED combined with yellow phosphor approach. However, these WLEDs are still insufficient for general illumination and flat panel display (FPD) applications because of their low color-rendering index (CRI < 75) and high correlated color temperature (CCT = 6000 K). Although near-ultraviolet (UV) LED chips provide more efficient excitation than blue chips, YAG:Ce3+ phosphors have very weak excitation in the near-UV spectral region. Hence, there is an increasing demand for novel yellow phosphor materials with excitation in the near-UV region. In this work, we report novel self-activated yellow Ca5Zn3.92In0.08(V0.99Ta0.01O4)6 (CZIVT) phosphors that efficiently convert near-UV excitation light into yellow luminescence. The crystal structure and lattice parameters of these CZIVT phosphors are elucidated through Rietveld refinement. Through doping with In3+ and Ta5+ ions, the emission intensity is enhanced in the red region, and the Stokes shift is controlled to obtain good color rendition. When a near-UV LED chip is coated with a combination of CZIVT and commercial blue Ba0.9Eu0.1MgAl10O17 phosphors, a pleasant WLED with a high CRI of 82.51 and a low CCT of 5231 K, which are essential for indoor illumination and FPDs, is achieved. PMID:25993044

Novel rare-earth-free yellow Ca5Zn3.92In0.08(V0.99Ta0.01O4)6 phosphors for dazzling white light-emitting diodes.

PubMed

Pavitra, E; Raju, G Seeta Rama; Park, Jin Young; Wang, Lili; Moon, Byung Kee; Yu, Jae Su

2015-05-20

White light-emitting diode (WLED) products currently available on the market are based on the blue LED combined with yellow phosphor approach. However, these WLEDs are still insufficient for general illumination and flat panel display (FPD) applications because of their low color-rendering index (CRI < 75) and high correlated color temperature (CCT = 6000 K). Although near-ultraviolet (UV) LED chips provide more efficient excitation than blue chips, YAG:Ce(3+) phosphors have very weak excitation in the near-UV spectral region. Hence, there is an increasing demand for novel yellow phosphor materials with excitation in the near-UV region. In this work, we report novel self-activated yellow Ca(5)Zn(3.92)In(0.08)(V(0.99)Ta(0.01)O(4))(6) (CZIVT) phosphors that efficiently convert near-UV excitation light into yellow luminescence. The crystal structure and lattice parameters of these CZIVT phosphors are elucidated through Rietveld refinement. Through doping with In(3+) and Ta(5+) ions, the emission intensity is enhanced in the red region, and the Stokes shift is controlled to obtain good color rendition. When a near-UV LED chip is coated with a combination of CZIVT and commercial blue Ba(0.9)Eu(0.1)MgAl(10)O(17) phosphors, a pleasant WLED with a high CRI of 82.51 and a low CCT of 5231 K, which are essential for indoor illumination and FPDs, is achieved.

Oxycarbonitride phosphors and light emitting devices using the same

DOEpatents

Li, Yuanqiang; Romanelli, Michael Dennis; Tian, Yongchi

2013-10-08

Disclosed herein is a novel family of oxycarbidonitride phosphor compositions and light emitting devices incorporating the same. Within the sextant system of M--Al--Si--O--N--C--Ln and quintuplet system of M--Si--O--N--C--Ln (M=alkaline earth element, Ln=rare earth element), the phosphors are composed of either one single crystalline phase or two crystalline phases with high chemical and thermal stability. In certain embodiments, the disclosed phosphor of silicon oxycarbidonitrides emits green light at wavelength between 530-550 nm. In further embodiments, the disclosed phosphor compositions emit blue-green to yellow light in a wavelength range of 450-650 nm under near-UV and blue light excitation.

Oxycarbonitride phosphors and light emitting devices using the same

DOEpatents

Li, Yuanqiang; Romanelli, Michael Dennis; Tian, Yongchi

2014-07-08

Disclosed herein is a novel family of oxycarbonitride phosphor compositions and light emitting devices incorporating the same. Within the sextant system of M--Al--Si--O--N--C--Ln and quintuplet system of M--Si--O--N--C--Ln (M=alkaline earth element, Ln=rare earth element), the phosphors are composed of either one single crystalline phase or two crystalline phases with high chemical and thermal stability. In certain embodiments, the disclosed phosphor of silicon oxycarbonitrides emits green light at wavelength between 530-550 nm. In further embodiments, the disclosed phosphor compositions emit blue-green to yellow light in a wavelength range of 450-650 nm under near-UV and blue light excitation.

Photoluminescence and thermal stability of yellow-emitting Na{sub 2}Ba{sub 2}Si{sub 2}O{sub 7}:Sm{sup 3+} phosphor for light-emitting diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Jiayue, E-mail: jiayue_sun@126.com; Di, Qiumei; Cui, Dianpeng

2014-12-15

Highlights: • Na{sub 2}Ba{sub 2}Si{sub 2}O{sub 7}:Sm{sup 3+} phosphors are obtained via a solid-state reaction method. • Excitation at 402 nm, the yellow color purity is close to 100%. • The mechanism of concentration quenching is dipole–dipole interaction. • The temperature-dependent luminescence property exceed that of YAG:Ce{sup 3+}. - Abstract: A series of yellow-emitting Na{sub 2}(Ba{sub 2−x}Sm{sub x})Si{sub 2}O{sub 7} phosphors have been prepared via solid-state reaction technique. X-ray diffraction (XRD), photoluminescence (PL) spectra, temperature-dependent luminescence property, concentration quenching mechanism and luminescence lifetime are applied to characterize the obtained samples. Under 402 nm near ultraviolent excitation, the samples emit yellowmore » light and the color purity is close to 100%. The critical quenching concentration of Sm{sup 3+} in the Na{sub 2}Ba{sub 2}Si{sub 2}O{sub 7} host is about 3.6 mol% and corresponding quenching behavior is ascribed to be electric dipole–dipole interaction. Furthermore, the phosphor has good thermal stability property, superior to the commercial yellow Y{sub 3}Al{sub 5}O{sub 12}:Ce{sup 3+} phosphor and the activation energy for thermal quenching is calculated as 0.18 eV.« less

Photoluminescence properties of Eu(3+)/ Sm(3+) activated CaZr4(PO4)6 phosphors.

PubMed

Nair, Govind B; Dhoble, S J

2016-09-01

Solid state reaction method was employed for the synthesis of a series of CaZr4(PO4)6: Eu(3+)/Sm(3+) phosphors. The red-emitting CaZr4(PO4)6:Eu(3+) phosphors can be efficiently excited at 396 nm and thereby, exhibit a strong red luminescence predominantly corresponding to the electric dipole transition at 615 nm. Under 405 nm excitation, CaZr4(PO4)6:Sm(3+) phosphors display orange emission with color temperatures approximately around 2200 K. The acquired results reveal that CaZr4(PO4)6: RE(3+) (RE = Eu, Sm) phosphors could be potential candidates for red and orange emitting phosphor, respectively, for UV/blue-pump LEDs.

Synthesis and luminescence characterization of a new yellowish-orange phosphor: Ba2 B10 O17 :Sm3.

PubMed

Li, Jiangong; Yan, Huifang; Yan, Fengmei

2017-02-01

A new yellowish-orange emitting phosphor, Ba 2 B 10 O 17 :Sm 3 + for use as a white light-emitting diode (W-LED) was synthesized by a solid-state reaction method. The X-ray diffraction results indicated that a pure Ba 2 B 10 O 17 material was obtained. As a potential yellowish-orange luminescent material for W-LEDs, the Ba 2 B 10 O 17 :Sm 3 + phosphor could be excited effectively by near-ultraviolet (n-UV) light and exhibited yellowish-orange emission centered at 560 nm corresponding to the 4 G 5/2  →  6 H 5/2 transition of Sm 3 + ions. The optimum concentration of Sm 3 + ions in Ba 2 B 10 O 17 , critical transfer distance (Ra) and concentration quenching mechanism of the presented phosphor were investigated. Moreover, CIE chromaticity coordinates and color purity performance of the Ba 2 B 10 O 17 :Sm 3 + phosphor were also discussed. The present work suggests that the Ba 2 B 10 O 17 :Sm 3 + phosphor has potential as a type of yellowish-orange emitting phosphor. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Red-emitting manganese-doped aluminum nitride phosphor

NASA Astrophysics Data System (ADS)

Cherepy, Nerine J.; Payne, Stephen A.; Harvey, Nicholas M.; Åberg, Daniel; Seeley, Zachary M.; Holliday, Kiel S.; Tran, Ich C.; Zhou, Fei; Martinez, H. Paul; Demeyer, Jessica M.; Drobshoff, Alexander D.; Srivastava, Alok M.; Camardello, Samuel J.; Comanzo, Holly A.; Schlagel, Deborah L.; Lograsso, Thomas A.

2016-04-01

We report high efficiency luminescence with a manganese-doped aluminum nitride red-emitting phosphor under 254 nm excitation, as well as its excellent lumen maintenance in fluorescent lamp conditions, making it a candidate replacement for the widely deployed europium-doped yttria red phosphor. Solid-state reaction of aluminum nitride powders with manganese metal at 1900 °C, 10 atm N2 in a reducing environment results in nitrogen deficiency, as revealed diffuse reflectance spectra. When these powders are subsequently annealed in flowing nitrogen at 1650 °C, higher nitrogen content is recovered, resulting in white powders. Silicon was added to samples as an oxygen getter to improve emission efficiency. NEXAFS spectra and DFT calculations indicate that the Mn dopant is divalent. From DFT calculations, the UV absorption band is proposed to be due to an aluminum vacancy coupled with oxygen impurity dopants, and Mn2+ is assumed to be closely associated with this site. In contrast with some previous reports, we find that the highest quantum efficiency with 254 nm excitation (Q.E. = 0.86 ± 0.14) is obtained in aluminum nitride with a low manganese doping level of 0.06 mol.%. The principal Mn2+ decay of 1.25 ms is assigned to non-interacting Mn sites, while additional components in the microsecond range appear with higher Mn doping, consistent with Mn clustering and resultant exchange coupling. Slower components are present in samples with low Mn doping, as well as strong afterglow, assigned to trapping on shallow traps followed by detrapping and subsequent trapping on Mn.

Blue-green phosphor for fluorescent lighting applications

DOEpatents

Srivastava, Alok; Comanzo, Holly; Manivannan, Venkatesan; Setlur, Anant Achyut

2005-03-15

A fluorescent lamp including a phosphor layer including Sr.sub.4 Al.sub.14 O.sub.25 :Eu.sup.2+ (SAE) and at least one of each of a red, green and blue emitting phosphor. The phosphor layer can optionally include an additional, deep red phosphor and a yellow emitting phosphor. The resulting lamp will exhibit a white light having a color rendering index of 90 or higher with a correlated color temperature of from 2500 to 10000 Kelvin. The use of SAE in phosphor blends of lamps results in high CRI light sources with increased stability and acceptable lumen maintenance over, the course of the lamp life.

Synthesis and luminescence properties of Eu3+-doped KLa(MoO4)2 red-emitting phosphor

NASA Astrophysics Data System (ADS)

Zuo, Haoqiang; Liu, Yun; Li, Jinyang; Shi, Xiaolei; Gao, Weiping

2015-09-01

Eu3+-doped KLa(MoO4)2 phosphors were synthesized by a simple hydrothermal method. X-ray diffraction (XRD) analysis demonstrated that the as-prepared products were pure monoclinic phase of KLa(MoO4)2. Field emission scanning electron microscopy (FE-SEM) images indicated that the morphology of the prepared phosphors evolved from uniform spherical-like to irregular elliposid-like with increase of the concentration. The photoluminescence (PL) spectra displayed that the phosphors show strong red light around 618 nm, attributed to 5D0 → 7F2 transition of Eu3+ ion under 465 nm excitation, and the optimal Eu3+ doping concentration was about 15 mol.% based on the concentration dependent emission spectra. According to Dexter's theory the electric dipole-dipole interaction (D-D) is the main mechanism for energy transfer between Eu3+ and Eu3+ ions. The CIE chromaticity (x, y) of the phosphors were about (0.65, 0.35) and it is close to the standard red chromaticity of NTSC. Therefore, the phosphors could be used as red phosphors for white light-emitting diodes.

High-brightness and high-color purity red-emitting Ca3Lu(AlO)3(BO3)4:Eu3+ phosphors with internal quantum efficiency close to unity for near-ultraviolet-based white-light-emitting diodes.

PubMed

Huang, Xiaoyong; Wang, Shaoying; Li, Bin; Sun, Qi; Guo, Heng

2018-03-15

In this work, we reported on high-brightness Eu 3+ -activated Ca 3 Lu(AlO) 3 (BO 3 ) 4 (CLAB) red-emitting phosphors. Under 397 nm excitation, the CLAB:Eu 3+ phosphors showed intense red emissions at around 621 nm with CIE coordinates of (0.657, 0.343). The optimal doping concentration of Eu 3+ ions was found to be 30 mol. %, and the CLAB:0.3Eu 3+ sample possessed high-color purity of 93% and ultra-high internal quantum efficiency as great as 98.5%. Importantly, the CLAB:0.3Eu 3+ also had good thermal stability. Finally, a white-light-emitting diode (WLED) lamp with good color-rendering index was fabricated by using a 365 nm ultraviolet chip and the phosphor blends of CLAB:0.3Eu 3+ red-emitting phosphors, (Ba,Sr) 2 SiO 4 :Eu 2+ green-emitting phosphors, and BaMgAl 10 O 7 :Eu 2+ blue-emitting phosphors.

Smart design to resolve spectral overlapping of phosphor-in-glass for high-powered remote-type white light-emitting devices.

PubMed

Lee, Jin Seok; Arunkumar, P; Kim, Sunghoon; Lee, In Jae; Lee, Hyungeui; Im, Won Bin

2014-02-15

The white light-emitting diode (WLED) is a state-of-the-art solid state technology, which has replaced conventional lighting systems due to its reduced energy consumption, its reliability, and long life. However, the WLED presents acute challenges in device engineering, due to its lack of color purity, efficacy, and thermal stability of the lighting devices. The prime cause for inadequacies in color purity and luminous efficiency is the spectral overlapping of red components with yellow/green emissions when generating white light by pumping a blue InGaN chip with yellow YAG:Ce³⁺ phosphor, where red phosphor is included, to compensate for deficiencies in the red region. An innovative strategy was formulated to resolve this spectral overlapping by alternatively arranging phosphor-in-glass (PiG) through cutting and reassembling the commercial red CaAlSiN₃:Eu²⁺ and green Lu₃Al₅O₁₂:Ce³⁺ PiG. PiGs were fabricated using glass frits with a low softening temperature of 600°C, which exhibited excellent thermal stability and high transparency, improving life time even at an operating temperature of 200°C. This strategy overcomes the spectral overlapping issue more efficiently than the randomly mixed and patented stacking design of multiple phosphors for a remote-type WLED. The protocol for the current design of PiG possesses excellent thermal and chemical stability with high luminous efficiency and color purity is an attempt to make smarter solid state lighting for high-powered remote-type white light-emitting devices.

Red-emitting manganese-doped aluminum nitride phosphor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cherepy, Nerine J.; Payne, Stephen A.; Harvey, Nicholas M.

2016-02-10

Here, we report high efficiency luminescence with a manganese-doped aluminum nitride red-emitting phosphor under 254 nm excitation, as well as its excellent lumen maintenance in fluorescent lamp conditions, making it a candidate replacement for the widely deployed europium-doped yttria red phosphor. Solid-state reaction of aluminum nitride powders with manganese metal at 1900 °C, 10 atm N2 in a reducing environment results in nitrogen deficiency, as revealed diffuse reflectance spectra. When these powders are subsequently annealed in flowing nitrogen at 1650 °C, higher nitrogen content is recovered, resulting in white powders. Silicon was added to samples as an oxygen getter tomore » improve emission efficiency. NEXAFS spectra and DFT calculations indicate that the Mn dopant is divalent. From DFT calculations, the UV absorption band is proposed to be due to an aluminum vacancy coupled with oxygen impurity dopants, and Mn2+ is assumed to be closely associated with this site. In contrast with some previous reports, we find that the highest quantum efficiency with 254 nm excitation (Q.E. = 0.86 ± 0.14) is obtained in aluminum nitride with a low manganese doping level of 0.06 mol.%. The principal Mn2+ decay of 1.25 ms is assigned to non-interacting Mn sites, while additional components in the microsecond range appear with higher Mn doping, consistent with Mn clustering and resultant exchange coupling. Slower components are present in samples with low Mn doping, as well as strong afterglow, assigned to trapping on shallow traps followed by detrapping and subsequent trapping on Mn.« less

Efficient rare-earth free red-emitting Ca2YSbO6:Mn4+,M(M = Li+, Na+, K+, Mg2+) phosphors for white light-emitting diodes.

PubMed

Zhong, Jiasong; Chen, Daqin; Chen, Xiao; Wang, Keyuan; Li, Xinyue; Zhu, Yiwen; Ji, Zhenguo

2018-05-08

Owing to its low-cost and satisfactory luminescent-emission performance in warm white light-emitting diodes (w-LEDs), the non-rare-earth Mn4+-activated red phosphor has become a promising competitor of commercial rare-earth doped phosphor. In this study, a series of novel red-light emitting phosphors based on Ca2YSbO6:Mn4+ have been developed successfully by a conventional solid-state reaction. The structural and luminescent properties of these phosphors are systematically investigated. The as-prepared Ca2YSbO6:Mn4+ product exhibits a broad excitation band ranging from 250 to 600 nm and an abnormal intense deep-red emission centered at 680 nm with a full width at half maximum (FWHM) of ∼46 nm. The optimal Mn4+ doping concentration is about 0.3 mol%, and the concentration quenching mechanism is determined to be a dipole-dipole interaction. Impressively, the Ca2YSbO6:0.003Mn4+ phosphor shows an outstanding quantum efficiency of 62.6% and an excellent thermal stability. In addition, the effect of Li+, Mg2+, Na+ and K+ dopants on the luminescent properties of Mn4+-doped Ca2YSbO6 phosphors is elucidated. Furthermore, by employing the as-prepared Ca2YSbO6:Mn4+ as a red component, a warm w-LED with high color rendering index (Ra = 87.5) and low correlated color temperature (CCT = 3255 K) can be acquired. It is believed that the present phosphor has a potential application as a supplement of the red component for warm w-LEDs.

Photoluminescence properties and structure of double perovskite Ba2ZnWO6:Eu3+, Li+ as a novel red emitting phosphor

NASA Astrophysics Data System (ADS)

Chen, Peng; Yang, Dingming; Hu, Wenyuan; Zhang, Jing; Wu, Yadong

2017-12-01

Novel red-emitting Ba2Zn1-x-yWO6:xEu3+, yLi+ phosphors were prepared using a high-temperature solid-state method, and the crystal structure, the photoluminescence properties and the doping concentrations of Eu3+ and Li+ were investigated. The results show that these phosphors can be excited by near-ultraviolet light (250-400 nm) and co-doped Li+ can significantly enhance their PL performance. An intense red emission peak at 598 nm (5D0-7F1 transitions) was observed with an excitation wavelength of 316 nm. The CIE chromaticity coordinates of the phosphors are located in the red region, indicating that the BZW:Eu3+, Li+ phosphor holds promise as a red phosphor for near-ultraviolet excited WLEDs.

Novel yellow-emitting Sr8MgLn(PO4)7:Eu2+ (Ln=Y, La) phosphors for applications in white LEDs with excellent color rendering index.

PubMed

Huang, Chien-Hao; Chen, Teng-Ming

2011-06-20

Eu(2+)-activated Sr(8)MgY(PO(4))(7) and Sr(8)MgLa(PO(4))(7) yellow-emitting phosphors were successfully synthesized by solid-state reactions for applications in excellent color rendering index white light-emitting diodes (LEDs). The excitation and reflectance spectra of these phosphors show broad band excitation and absorption in the 250-450 nm near-ultraviolet region, which is ascribed to the 4f(7) → 4f(6)5d(1) transitions of Eu(2+). Therefore, these phosphors meet the application requirements for near-UV LED chips. Upon excitation at 400 nm, the Sr(8)MgY(PO(4))(7):Eu(2+) and Sr(8)MgLa(PO(4))(7):Eu(2+) phosphors exhibit strong yellow emissions centered at 518, 610, and 611 nm with better thermal stability than (Ba,Sr)(2)SiO(4) (570 nm) commodity phosphors. The composition-optimized concentrations of Eu(2+) in Sr(8)MgLa(PO(4))(7):Eu(2+) and Sr(8)MgY(PO(4))(7):Eu(2+) phosphors were determined to be 0.01 and 0.03 mol, respectively. A warm white-light near-UV LED was fabricated using a near-UV 400 nm chip pumped by a phosphor blend of blue-emitting BaMgAl(10)O(17):Eu(2+) and yellow-emitting Sr(8)MgY(PO(4))(7):0.01Eu(2+) or Sr(8)MgLa(PO(4))(7):0.03Eu(2+), driven by a 350 mA current. The Sr(8)MgY(PO(4))(7):0.01Eu(2+) and Sr(8)MgLa(PO(4))(7):0.03Eu(2+) containing LEDs produced a white light with Commission International de I'Eclairage (CIE) chromaticity coordinates of (0.348, 0.357) and (0.365, 0.328), warm correlated color temperatures of 4705 and 4100 K, and excellent color rendering indices of 95.375 and 91.75, respectively. © 2011 American Chemical Society

Low driving voltage blue, green, yellow, red and white organic light-emitting diodes with a simply double light-emitting structure.

PubMed

Zhang, Zhensong; Yue, Shouzhen; Wu, Yukun; Yan, Pingrui; Wu, Qingyang; Qu, Dalong; Liu, Shiyong; Zhao, Yi

2014-01-27

Low driving voltage blue, green, yellow, red and white phosphorescent organic light-emitting diodes (OLEDs) with a common simply double emitting layer (D-EML) structure are investigated. Our OLEDs without any out-coupling schemes as well as n-doping strategies show low driving voltage, e.g. < 2.4 V for onset and < 3 V for 1000 cd/m2, and high efficiency of 32.5 lm/W (13.3%), 58.8 lm/W (14.3%), 55.1 lm/W (14.6%), 24.9 lm/W (13.7%) and 45.1 lm/W (13.5%) for blue, green, yellow, red and white OLED, respectively. This work demonstrates that the low driving voltages and high efficiencies can be simultaneously realized with a common simply D-EML structure.

Photoluminescence studies of high-efficient red-emitting K{sub 2}Y(WO{sub 4})(PO{sub 4}):Eu{sup 3+} phosphor for NUV LED

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Xinguo; State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275; Chen, Mengyang

Highlights: • Novel K{sub 2}Y(WO{sub 4})(PO{sub 4}):Eu{sup 3+} red phosphors were prepared by solid-state method. • Phosphors exhibit strong red light under NUV excitation with quantum efficiency of 70.5 %. • Judd–Ofelt analysis ascertains the presence of Eu{sup 3+} in a highly asymmetric environment. • The red LED prototype was fabricated with KYWP:Eu{sup 3+} phosphor and InGaN chip. - Abstract: A series of high-efficient red-emitting phosphors K{sub 2}Y(WO{sub 4})(PO{sub 4}):Eu{sup 3+} have been successfully synthesized by conventional solid-state reaction, and its photoluminescence (PL) properties have been investigated. The phosphors can be excited efficiently by NUV light, then exhibit strong redmore » emission with quantum efficiency of 70.5%. The concentration quenching takes place at relatively high concentration of Eu{sup 3+} (x = 0.70), which is further confirmed by the variation of decay curves of the entitled phosphors. Judd–Ofelt analysis ascertains the presence of Eu{sup 3+} in a highly asymmetric environment. The phosphor exhibits good thermal stability (92.5% at 100 °C and 84.1% at 180 °C). The red LED prototype fabricated by opyimized-composition K{sub 2}Y(WO{sub 4})(PO{sub 4}):0.70Eu{sup 3+} phosphor and 395 nm-emitting InGaN chips exhibit bright red emission. The results indicate that the K{sub 2}Y(WO{sub 4})(PO{sub 4}):Eu{sup 3+} phosphors are promising red phosphors for NUV LED.« less

A novel double perovskite tellurate Eu3+-doped Sr2MgTeO6 red-emitting phosphor with high thermal stability

NASA Astrophysics Data System (ADS)

Liang, Jingyun; Zhao, Shancang; Yuan, Xuexia; Li, Zengmei

2018-05-01

A series of novel double perovskite tellurate red-emitting phosphors Sr2MgTeO6:xEu3+ (x = 0.05-0.40) were successfully synthesized by a high-temperature solid-state reaction method. The phase structure, photoluminescence properties and thermal stability of the phosphor were investigated in detail. The phosphor shows dominant emission peak at 614 nm belonging to the 5D0 → 7F2 electric dipole transition under 465 nm excitation. The luminescence intensity keeps increasing with increasing the content of Eu3+ to 25 mol%, and the critical transfer distance of Eu3+ was calculated to be 12 Å. The quenching temperature for Sr2MgTeO6:0.25Eu3+ was estimated to be above 500 K. This spectral feature reveals high color purity and excellent chromaticity coordinate characteristics. Therefore, Eu3+-doped Sr2MgTeO6 phosphors are potential red phosphors for blue chip-based white light-emitting diode and display devices.

Red Emission of SrAl2O4:Mn4+ Phosphor for Warm White Light-Emitting Diodes

NASA Astrophysics Data System (ADS)

Chi, N. T. K.; Tuan, N. T.; Lien, N. T. K.; Nguyen, D. H.

2018-05-01

In this work, SrAl2O4:Mn4+ phosphor is prepared by co-precipitation. The phase structure, morphology, composition and luminescent performance of the phosphor are investigated in detail with x-ray diffraction, field emission scanning electron microscopy, steady-state photoluminescence (PL) spectra, and temperature-dependent PL measurements. The phosphor shows a strong red emission peak at ˜ 690 nm, which is due to the transition between electronic levels and the electric dipole transition 2Eg to 4A2g of Mn4+ ions located at the sites with D3d local symmetry. The sample doped with 0.04 mol.% Mn4+ exhibits intense red emission with high thermal stability and appropriate International Commission on Illumination (CIE) coordinates (x = 0.6959, y = 0.2737). It is also found that the phosphor absorption in an extended band from 250 nm to 500 nm has three peaks at 320 nm, 405 nm, and 470 nm, which match well with the emission band of ultraviolet (UV) lighting emission diode (LED) or blue LED chips. These results demonstrate that SrAl2O4:Mn4+ phosphor can play the role of activator in narrow red-emitting phosphor, which is potentially useful in UV (˜ 320 nm) or blue (˜ 460 nm) LED.

Red-emitting LaOF:Eu{sup 3+} phosphors: Synthesis, structure and their Judd–Ofelt analysis for LED applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dhananjaya, N., E-mail: ndhananjayas@gmail.com; Shivakumara, C.; Saraf, Rohit

Highlights: • Red-emitting LaOF:Eu{sup 3+} phosphors were synthesized via facile solid state route. • Judd–Ofelt intensity parameters and radiative properties were determined from PL data. • CIE color coordinates of LaOF:Eu{sup 3+} phosphor is close to the commercial red phosphors. • Eu{sup 3+}-activated LaOF phosphor is a potential candidate for the production of red component in white LEDs. - Abstract: In the present study, we have synthesized a series of La{sub 1−x}Eu{sub x}OF (0.01 ≤ x ≤ 0.09) phosphors by the conventional solid-state reaction route at relatively low temperature (500 °C) and shorter duration of 2 h. The compounds weremore » crystallized in the rhombohedral structure with the space group R-3m (No. 166). Upon UV excitation (254 nm), the photoluminescence spectra exhibit characteristic luminescence {sup 5}D{sub 0} → {sup 7}F{sub J} (J = 1, 2, 3, and 4) intra-4f shell Eu{sup 3+} ion transitions. An intense red emission peak at 610 nm was observed due to electric dipole ({sup 5}D{sub 0} → {sup 7}F{sub 2}) transition. Judd–Ofelt theory was employed to evaluate various radiative parameters such as radiative emission rates, lifetime, branching and asymmetry ratios. CIE color coordinates confirmed the red emission of the phosphors. The luminescent results reveal that LaOF:Eu{sup 3+} phosphor can be used as potential candidate for developing red component in white LED applications.« less

Facile Atmospheric Pressure Synthesis of High Thermal Stability and Narrow-Band Red-Emitting SrLiAl3N4:Eu(2+) Phosphor for High Color Rendering Index White Light-Emitting Diodes.

PubMed

Zhang, Xuejie; Tsai, Yi-Ting; Wu, Shin-Mou; Lin, Yin-Chih; Lee, Jyh-Fu; Sheu, Hwo-Shuenn; Cheng, Bing-Ming; Liu, Ru-Shi

2016-08-03

Red phosphors (e.g., SrLiAl3N4:Eu(2+)) with high thermal stability and narrow-band properties are urgently explored to meet the next-generation high-power white light-emitting diodes (LEDs). However, to date, synthesis of such phosphors remains an arduous task. Herein, we report, for the first time, a facile method to synthesize SrLiAl3N4:Eu(2+) through Sr3N2, Li3N, Al, and EuN under atmospheric pressure. The as-synthesized narrow-band red-emitting phosphor exhibits excellent thermal stability, including small chromaticity shift and low thermal quenching. Intriguingly, the title phosphor shows an anomalous increase in theoretical lumen equivalent with the increase of temperature as a result of blue shift and band broadening of the emission band, which is crucial for high-power white LEDs. Utilizing the title phosphor, commercial YAG:Ce(3+), and InGaN-based blue LED chip, a proof-of-concept warm white LEDs with a color rendering index (CRI) of 91.1 and R9 = 68 is achieved. Therefore, our results highlight that this method, which is based on atmospheric pressure synthesis, may open a new means to explore narrow-band-emitting nitride phosphor. In addition, the underlying requirements to design Eu(2+)-doped narrow-band-emitting phosphors were also summarized.

A dual-emitting core-shell carbon dot-silica-phosphor composite for white light emission

NASA Astrophysics Data System (ADS)

Chen, Yonghao; Lei, Bingfu; Zheng, Mingtao; Zhang, Haoran; Zhuang, Jianle; Liu, Yingliang

2015-11-01

A unique dual-emitting core-shell carbon dot-silica-phosphor (CDSP) was constructed from carbon dots (CDs), tetraethoxysilane (TEOS) and Sr2Si5N8:Eu2+ phosphor through a one-pot sol-gel method. Blue emitting CDs uniformly disperse in the silica layer covering the orange emitting phosphor via a polymerization process, which makes CDSP achieve even white light emission. Tunable photoluminescence of CDSP is observed and the preferable white light emission is achieved through changing the excitation wavelength or controlling the mass ratio of the phosphor. When CDSP powders with a phosphor rate of 3.9% and 5.1% are excited at a wavelength of 400 nm, preferable white light emission is observed, with Commission Internationale de l'Eclairage (CIE) coordinates of (0.32, 0.32) and (0.34, 0.32), respectively. Furthermore, CDSP can mix well with epoxy resin to emit strong and even white light, and based on this, a CDSP-based white LED with a high colour rendering index (CRI) of 94 was fabricated.A unique dual-emitting core-shell carbon dot-silica-phosphor (CDSP) was constructed from carbon dots (CDs), tetraethoxysilane (TEOS) and Sr2Si5N8:Eu2+ phosphor through a one-pot sol-gel method. Blue emitting CDs uniformly disperse in the silica layer covering the orange emitting phosphor via a polymerization process, which makes CDSP achieve even white light emission. Tunable photoluminescence of CDSP is observed and the preferable white light emission is achieved through changing the excitation wavelength or controlling the mass ratio of the phosphor. When CDSP powders with a phosphor rate of 3.9% and 5.1% are excited at a wavelength of 400 nm, preferable white light emission is observed, with Commission Internationale de l'Eclairage (CIE) coordinates of (0.32, 0.32) and (0.34, 0.32), respectively. Furthermore, CDSP can mix well with epoxy resin to emit strong and even white light, and based on this, a CDSP-based white LED with a high colour rendering index (CRI) of 94 was fabricated

Photoluminescence in Sm3+ doped Ba2P2O7 phosphor prepared by solution combustion method

NASA Astrophysics Data System (ADS)

Ghawade, Sonal P.; Deshmukh, Kavita A.; Dhoble, S. J.; Deshmukh, Abhay D.

2018-05-01

In this paper, Sm3+ doped Ba2P2O7 phosphors were synthesized via a Solution combustion method. The crystal structure of the phosphor was characterized by XRD. Orange-red emission was observed from these phosphors under near-ultraviolet (UV) excitation at 404 nm. The luminescence properties of the obtained phosphors were characterized by different techniques. The Ba2P2O7:Sm3+ phosphor can be efficiently excited by near-UV and blue light, and their emission spectrum consists of three emission peaks, at 564, 602, and 646 nm, respectively. Based on the results, the as prepared Ba2P2O7:Sm3+ phosphors are promising orange-red-emitting phosphors exhibit great potential may be applicable as a spectral convertor in c-Si solar cell to enhance the efficiency of solar cell in future.

Light Converting Inorganic Phosphors for White Light-Emitting Diodes

PubMed Central

Chen, Lei; Lin, Chun-Che; Yeh, Chiao-Wen; Liu, Ru-Shi

2010-01-01

White light-emitting diodes (WLEDs) have matched the emission efficiency of florescent lights and will rapidly spread as light source for homes and offices in the next 5 to 10 years. WLEDs provide a light element having a semiconductor light emitting layer (blue or near-ultraviolet (nUV) LEDs) and photoluminescence phosphors. These solid-state LED lamps, rather than organic light emitting diode (OLED) or polymer light-emitting diode (PLED), have a number of advantages over conventional incandescent bulbs and halogen lamps, such as high efficiency to convert electrical energy into light, reliability and long operating lifetime. To meet with the further requirement of high color rendering index, warm light with low color temperature, high thermal stability and higher energy efficiency for WLEDs, new phosphors that can absorb excitation energy from blue or nUV LEDs and generate visible emissions efficiently are desired. The criteria of choosing the best phosphors, for blue (450−480 nm) and nUV (380−400 nm) LEDs, strongly depends on the absorption and emission of the phosphors. Moreover, the balance of light between the emission from blue-nUV LEDs and the emissions from phosphors (such as yellow from Y3Al5O12:Ce3+) is important to obtain white light with proper color rendering index and color temperature. Here, we will review the status of phosphors for LEDs and prospect the future development.

Cyan-emitting and orange-emitting fluorescent proteins as a donor/acceptor pair for fluorescence resonance energy transfer.

PubMed

Karasawa, Satoshi; Araki, Toshio; Nagai, Takeharu; Mizuno, Hideaki; Miyawaki, Atsushi

2004-07-01

GFP (green fluorescent protein)-based FRET (fluorescence resonance energy transfer) technology has facilitated the exploration of the spatio-temporal patterns of cellular signalling. While most studies have used cyan- and yellow-emitting FPs (fluorescent proteins) as FRET donors and acceptors respectively, this pair of proteins suffers from problems of pH-sensitivity and bleeding between channels. In the present paper, we demonstrate the use of an alternative additional donor/acceptor pair. We have cloned two genes encoding FPs from stony corals. We isolated a cyan-emitting FP from Acropara sp., whose tentacles exhibit cyan coloration. Similar to GFP from Renilla reniformis, the cyan FP forms a tight dimeric complex. We also discovered an orange-emitting FP from Fungia concinna. As the orange FP exists in a complex oligomeric structure, we converted this protein into a monomeric form through the introduction of three amino acid substitutions, recently reported to be effective for converting DsRed into a monomer (Clontech). We used the cyan FP and monomeric orange FP as a donor/acceptor pair to monitor the activity of caspase 3 during apoptosis. Due to the close spectral overlap of the donor emission and acceptor absorption (a large Förster distance), substantial pH-resistance of the donor fluorescence quantum yield and the acceptor absorbance, as well as good separation of the donor and acceptor signals, the new pair can be used for more effective quantitative FRET imaging.

High Color-Purity Green, Orange, and Red Light-Emitting Didoes Based on Chemically Functionalized Graphene Quantum Dots

NASA Astrophysics Data System (ADS)

Kwon, Woosung; Kim, Young-Hoon; Kim, Ji-Hee; Lee, Taehyung; Do, Sungan; Park, Yoonsang; Jeong, Mun Seok; Lee, Tae-Woo; Rhee, Shi-Woo

2016-04-01

Chemically derived graphene quantum dots (GQDs) to date have showed very broad emission linewidth due to many kinds of chemical bondings with different energy levels, which significantly degrades the color purity and color tunability. Here, we show that use of aniline derivatives to chemically functionalize GQDs generates new extrinsic energy levels that lead to photoluminescence of very narrow linewidths. We use transient absorption and time-resolved photoluminescence spectroscopies to study the electronic structures and related electronic transitions of our GQDs, which reveals that their underlying carrier dynamics is strongly related to the chemical properties of aniline derivatives. Using these functionalized GQDs as lumophores, we fabricate light-emitting didoes (LEDs) that exhibit green, orange, and red electroluminescence that has high color purity. The maximum current efficiency of 3.47 cd A-1 and external quantum efficiency of 1.28% are recorded with our LEDs; these are the highest values ever reported for LEDs based on carbon-nanoparticle phosphors. This functionalization of GQDs with aniline derivatives represents a new method to fabricate LEDs that produce natural color.

Warm White Light-Emitting Diodes Based on a Novel Orange Cationic Iridium(III) Complex.

PubMed

Tang, Huaijun; Meng, Guoyun; Chen, Zeyu; Wang, Kaimin; Zhou, Qiang; Wang, Zhengliang

2017-06-16

A novel orange cationic iridium(III) complex [(TPTA)₂Ir(dPPOA)]PF₆ (TPTA: 3,4,5-triphenyl-4 H -1,2,4-triazole, dPPOA: N,N-diphenyl-4-(5-(pyridin-2-yl)-1,3,4-oxadiazol-2-yl)aniline) was synthesized and used as a phosphor in light-emitting diodes (LEDs). [(TPTA)₂Ir(dPPOA)]PF₆ has high thermal stability with a decomposition temperature ( T d ) of 375 °C, and its relative emission intensity at 100 °C is 88.8% of that at 25°C. When only [(TPTA)₂Ir(dPPOA)]PF₆ was used as a phosphor at 6.0 wt % in silicone and excited by a blue GaN (GaN: gallium nitride) chip (450 nm), an orange LED was obtained. A white LED fabricated by a blue GaN chip (450 nm) and only yellow phosphor Y₃Al₅O 12 :Ce 3+ (YAG:Ce) (1.0 wt % in silicone) emitted cold white light, its CIE (CIE: Commission International de I'Eclairage ) value was (0.32, 0.33), color rendering index (CRI) was 72.2, correlated color temperature (CCT) was 6877 K, and luminous efficiency ( η L ) was 128.5 lm∙W -1 . Such a cold white LED became a neutral white LED when [(TPTA)₂Ir(dPPOA)]PF₆ was added at 0.5 wt %; its corresponding CIE value was (0.35, 0.33), CRI was 78.4, CCT was 4896 K, and η L was 85.2 lm∙W -1 . It further became a warm white LED when [(TPTA)₂Ir(dPPOA)]PF₆ was added at 1.0 wt %; its corresponding CIE value was (0.39, 0.36), CRI was 80.2, CCT was 3473 K, and η L was 46.1 lm∙W -1 . The results show that [(TPTA)₂Ir(dPPOA)]PF₆ is a promising phosphor candidate for fabricating warm white LEDs.

Warm White Light-Emitting Diodes Based on a Novel Orange Cationic Iridium(III) Complex

PubMed Central

Tang, Huaijun; Meng, Guoyun; Chen, Zeyu; Wang, Kaimin; Zhou, Qiang; Wang, Zhengliang

2017-01-01

A novel orange cationic iridium(III) complex [(TPTA)2Ir(dPPOA)]PF6 (TPTA: 3,4,5-triphenyl-4H-1,2,4-triazole, dPPOA: N,N-diphenyl-4-(5-(pyridin-2-yl)-1,3,4-oxadiazol-2-yl)aniline) was synthesized and used as a phosphor in light-emitting diodes (LEDs). [(TPTA)2Ir(dPPOA)]PF6 has high thermal stability with a decomposition temperature (Td) of 375 °C, and its relative emission intensity at 100 °C is 88.8% of that at 25°C. When only [(TPTA)2Ir(dPPOA)]PF6 was used as a phosphor at 6.0 wt % in silicone and excited by a blue GaN (GaN: gallium nitride) chip (450 nm), an orange LED was obtained. A white LED fabricated by a blue GaN chip (450 nm) and only yellow phosphor Y3Al5O12:Ce3+ (YAG:Ce) (1.0 wt % in silicone) emitted cold white light, its CIE (CIE: Commission International de I’Eclairage) value was (0.32, 0.33), color rendering index (CRI) was 72.2, correlated color temperature (CCT) was 6877 K, and luminous efficiency (ηL) was 128.5 lm∙W−1. Such a cold white LED became a neutral white LED when [(TPTA)2Ir(dPPOA)]PF6 was added at 0.5 wt %; its corresponding CIE value was (0.35, 0.33), CRI was 78.4, CCT was 4896 K, and ηL was 85.2 lm∙W−1. It further became a warm white LED when [(TPTA)2Ir(dPPOA)]PF6 was added at 1.0 wt %; its corresponding CIE value was (0.39, 0.36), CRI was 80.2, CCT was 3473 K, and ηL was 46.1 lm∙W−1. The results show that [(TPTA)2Ir(dPPOA)]PF6 is a promising phosphor candidate for fabricating warm white LEDs. PMID:28773020

Recent developments in white light emitting diodes

NASA Astrophysics Data System (ADS)

Lohe, P. P.; Nandanwar, D. V.; Belsare, P. D.; Moharil, S. V.

2018-05-01

In the recent years solid state lighting based on LEDs has revolutionized lighting technology. LEDs have many advantages over the conventional lighting based on fluorescent and incandescent lamps such as mercury free, high conversion efficiency of electrical energy into light, long lifetime reliability and ability to use with many types of devices. LEDs have emerged as a new potentially revolutionary technology that could save up to half of energy used for lighting applications. White LEDs would be the most important light source in the future, so much so that this aspect had been highlighted by the Nobel committee during the award of 2014 Nobel Prize for Physics. Recent advancement in the fabrication of GaN chip capable of emitting in blue and near UV region paved way for fabrication of white LED lamps. Mainly there are two approaches used for preparing white emitting solid state lamp. In the first approach blue light (λ=450 nm) emitted from the InGaN LED chip is partially absorbed by the YAG:Ce3+ phosphor coated on it and re-emitted as yellow fluorescence. A white light can be generated by the combination of blue + yellow emission bands. These lamps are already available. But they are suffering from major drawback that their Colour Rendering Index (CRI) is low. In the second approach, white LEDs are made by coating near ultraviolet emitting (360 to 410nm) LED with a mixture of high efficiency red, green and blue emitting phosphors, analogous to the fluorescent lamp. This method yields lamps with better color rendition. Addition of a yellow emitting phosphor improves CRI further. However conversion efficiency is compromised to some extent. Further the cost of near UV emitting chip is very high compared to blue emitting chips. Thus cost and light output wise, near UV chips are much inferior to blue chips. Recently some rare earth activated oxynitrides, silicates, fluorides have emerged as an important family of luminescent materials for white LED application

Optical Properties of ZnCdS:I Orange and ZnSTe:I White Thin Film Phosphor for High Ra White LED

NASA Astrophysics Data System (ADS)

Fujii, Satoshi; Tasaki, Norio; Shinomura, Naohiko; Kurai, Satoshi; Yamada, Yoichi; Taguchi, Tsunemasa

In order to develop visible thin film phosphors, we have for the first time prepared ZnCdS and ZnSTe doped with Iodine (I) using low-pressure MOCVD method. ZnCdS:I, of which Cd composition was calibrated to match the lattice constant to that of substrate and the band gap to absorption peak, showed a orange broad emission consist of yellow near band edge emission and red SA emission. Isoelectronic Te in ZnS indicates strong blue-green emissions, whilst I donor impurity in ZnS shows strong red SA emissions. A typical ZnSTe:I thin film shows two broad emission bands locating at around 500 and 680 nm, respectively, indicating Ra˜90. It was shown that high Ra thin film phosphor can be realized by single material (ZnSTe:I), and that MOCVD method is capable for controlling the thickness and doping profile to obtain uniform white emission pattern.

[Effect of transparent yellow and orange colored contact lenses on color discrimination in the yellow color range].

PubMed

Schürer, M; Walter, A; Brünner, H; Langenbucher, A

2015-08-01

Colored transparent filters cause a change in color perception and have an impact on the perceptible amount of different colors and especially on the ability to discriminate between them. Yellow or orange tinted contact lenses worn to enhance contrast vision by reducing or blocking short wavelengths also have an effect on color perception. The impact of the yellow and orange tinted contact lenses Wöhlk SPORT CONTRAST on color discrimination was investigated with the Erlangen colour measurement system in a study with 14 and 16 subjects, respectively. In relation to a yellow reference color located at u' = 0.2487/v' = 0.5433, measurements of color discrimination thresholds were taken in up to 6 different color coordinate axes. Based on these thresholds, color discrimination ellipses were calculated. These results are given in the Derrington, Krauskopf and Lennie (DKL) color system. Both contact lenses caused a shift of the reference color towards higher saturated colors. Color discrimination ability with the yellow and orange colored lenses was significantly enhanced along the blue-yellow axis in comparison to the reference measurements without a tinted filter. Along the red-green axis only the orange lens caused a significant reduction of color discrimination threshold distance to the reference color. Yellow and orange tinted contact lenses enhance the ability of color discrimination. If the transmission spectra and the induced changes are taken into account, these results can also be applied to other filter media, such as blue filter intraocular lenses.

Intercrossed carbon nanorings with pure surface states as low-cost and environment-friendly phosphors for white-light-emitting diodes.

PubMed

Li, Xiaoming; Liu, Yanli; Song, Xiufeng; Wang, Hao; Gu, Haoshuang; Zeng, Haibo

2015-02-02

As an important energy-saving technique, white-light-emitting diodes (W-LEDs) have been seeking for low-cost and environment-friendly substitutes for rare-earth-based expensive phosphors or Pd(2+)/Cd(2+)-based toxic quantum dots (QDs). In this work, precursors and chemical processes were elaborately designed to synthesize intercrossed carbon nanorings (IC-CNRs) with relatively pure hydroxy surface states for the first time, which enable them to overcome the aggregation-induced quenching (AIQ) effect, and to emit stable yellow-orange luminescence in both colloidal and solid states. As a direct benefit of such scarce solid luminescence from carbon nanomaterials, W-LEDs with color coordinate at (0.28, 0.27), which is close to pure white light (0.33, 0.33), were achieved through using these low-temperature-synthesized and toxic ion-free IC-CNRs as solid phosphors on blue LED chips. This work demonstrates that the design of surface states plays a crucial role in exploring new functions of fluorescent carbon nanomaterials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Luminescence properties of red-emission Mg4 Nb2 O9:Eu3+ phosphor.

PubMed

Cao, Renping; Cao, Chunyan; Yu, Xiaoguang; Qiu, Jianrong

2015-03-01

Red-emitting Mg4 Nb2 O9 :Eu(3+) phosphor is synthesized via a solid-state reaction method in air, and its crystal structure and luminescence are investigated. The phosphor can be excited efficiently by ~ 395 nm light, coupled well with a ~ 395 nm near-ultraviolet chip and emits red light at ~ 613 nm with sharp spectra due to (5) D0  → (7)  F2 transition of the Eu(3+) ion. Mg4 Nb2 O9 :Eu(3+) phosphor sintered at 1350 ºC shows Commission international de I'Eclairage (CIE) chromaticity coordinates of x = 0.6354, y = 0.3592, and is a potential red-emitting phosphor candidate for white light-emitting diodes (W-LEDs) under ~ 395 nm near-ultraviolet LED chip excitation. Copyright © 2014 John Wiley & Sons, Ltd.

Green emitting phosphors and blends thereof

DOEpatents

Setlur, Anant Achyut; Siclovan, Oltea Puica; Nammalwar, Prasanth Kumar; Sathyanarayan, Ramesh Rao; Porob, Digamber G.; Chandran, Ramachandran Gopi; Heward, William Jordan; Radkov, Emil Vergilov; Briel, Linda Jane Valyou

2010-12-28

Phosphor compositions, blends thereof and light emitting devices including white light emitting LED based devices, and backlights, based on such phosphor compositions. The devices include a light source and a phosphor material as described. Also disclosed are phosphor blends including such a phosphor and devices made therefrom.

A novel yellow-emitting SrAlSi{sub 4}N{sub 7}:Ce{sup 3+} phosphor for solid state lighting: Synthesis, electronic structure and photoluminescence properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruan, Jian; Laboratory of Glasses and Nanostructured Functional Materials, 122 Luoshi Road, Wuhan, Hubei 430070; Xie, Rong-Jun, E-mail: Xie.Rong-Jun@nims.go.jp

2013-12-15

Ce{sup 3+}-doped and Ce{sup 3+}/Li{sup +}-codoped SrAlSi{sub 4}N{sub 7} phosphors were synthesized by gas pressure sintering of powder mixtures of Sr{sub 3}N{sub 2}, AlN, α-Si{sub 3}N{sub 4}, CeN and Li{sub 3}N. The phase purity, electronic crystal structure, photoluminescence properties of SrAlSi{sub 4}N{sub 7}:Ce{sup 3+}(Ce{sup 3+}/Li{sup +}) were investigated in this work. The band structure calculated by the DMol{sup 3} code shows that SrAlSi{sub 4}N{sub 7} has a direct band gap of 3.87 eV. The single crystal analysis of Ce{sup 3+}-doped SrAlSi{sub 4}N{sub 7} indicates a disordered Si/Al distribution and nitrogen vacnacy defects. SrAlSi{sub 4}N{sub 7} was identified as a majormore » phase of the fired powders, and Sr{sub 5}Al{sub 5}Si{sub 21}N{sub 35}O{sub 2} and AlN as minor phases. Both Ce{sup 3+} and Ce{sup 3+}/Li{sup +} doped SrAlSi{sub 4}N{sub 7} phosphors can be efficiently excited by near-UV or blue light and show a broadband yellow emission peaking around 565 nm. A highest external quantum efficiency of 38.3% under the 450 nm excitation was observed for the Ce{sup 3+}/Li{sup +}-doped SrAlSi{sub 4}N{sub 7} (5 mol%). A white light LED lamp with color temperature of 6300 K and color rendering index of Ra=78 was achieved by combining Sr{sub 0.97}Al{sub 1.03}Si{sub 3.997}N/94/maccounttest14=t0005{sub 1}8193 {sub 7}:Ce{sup 3+}{sub 0.03} with a commercial blue InGaN chip. It indicates that SrAlSi{sub 4}N{sub 7}:Ce{sup 3+} is a promising yellow emitting down-conversion phosphor for white LEDs. - Graphical abstract: One-phosphor converted white light-emitting diode (LED) was fabricated by combining a blue LED chip and a yellow-emitting SrAlSi4N7:Ce{sup 3+} phosphor (see inset), which has the color rendering index of 78 and color temperature of 6300 K. - Highlights: • We reported a new yellow nitride phosphor suitable for solid state lighting. • We solved the crystal structure and evidenced a disordered Si/Al distribution. • We fabricated a high color

Luminescent properties of MAl(SO4)2 Br:Eu(3+) (M = Sr or Mg) red phosphors for near-UV light-emitting diodes.

PubMed

Deshmukh, Priti B; Puppalwar, S P; Dhoble, N S; Dhoble, S J

2015-02-01

Eu(3+) -activated MAl(SO4 )2 Br phosphors (where M = Mg or Sr) are successfully prepared using a wet chemical reaction technique. The samples are characterized by X-ray diffraction (XRD) and photoluminescence (PL) spectroscopies. The XRD pattern revealed that both the samples are microcrystalline in nature. PL of Eu(3+) -doped SrAl(SO4 )2 Br and MgAl(SO4 )2 Br phosphors exhibited characteristic red emission coming from the (5) D0  → (7) F2 (616 nm) electron transition, when excited by 396 nm wavelength of light. The maximum intensity of luminescence was observed at a concentration of 1 mol% Eu(3+) . The intensity of the electric dipole transition at 616 nm is greater than that of the magnetic dipole transition at 594 nm. The results showed that MAl(SO4 )2 Br:Eu(3+) , (M = Mg, Sr) phosphors have potential application in near-UV light-emitting diodes as efficient red-emitting phosphor. Copyright © 2014 John Wiley & Sons, Ltd.

Sr(1.7)Zn(0.3)CeO4: Eu3+ novel red-emitting phosphors: synthesis and photoluminescence properties.

PubMed

Li, Haifeng; Zhao, Ran; Jia, Yonglei; Sun, Wenzhi; Fu, Jipeng; Jiang, Lihong; Zhang, Su; Pang, Ran; Li, Chengyu

2014-03-12

A series of novel red-emitting Sr1.7Zn0.3CeO4:Eu(3+) phosphors were synthesized through conventional solid-state reactions. The powder X-ray diffraction patterns and Rietveld refinement verified the similar phase of Sr1.7Zn0.3CeO4:Eu(3+) to that of Sr2CeO4. The photoluminescence spectrum exhibits that peak located at 614 nm ((5)D0-(7)F2) dominates the emission of Sr1.7Zn0.3CeO4:Eu(3+) phosphors. Because there are two regions in the excitation spectrum originating from the overlap of the Ce(4+)-O(2-) and Eu(3+)-O(2-) charge-transfer state band from 200 to 440 nm, and from the intra-4f transitions at 395 and 467 nm, the Sr1.7Zn0.3CeO4:Eu(3+) phosphors can be well excited by the near-UV light. The investigation of the concentration quenching behavior, luminescence decay curves, and lifetime implies that the dominant mechanism type leading to concentration quenching is the energy transfer among the nearest neighbor or next nearest neighbor activators. The discussion about the dependence of photoluminescence spectra on temperature shows the better thermal quenching properties of Sr1.7Zn0.3CeO4:0.3Eu(3+) than that of Sr2CeO4:Eu(3+). The experimental data indicates that Sr1.7Zn0.3CeO4:Eu(3+) phosphors have the potential as red phosphors for white light-emitting diodes.

A novel tunable white light emitting multiphase phosphor obtained from Ba2TiP2O9 by introducing Eu3+

NASA Astrophysics Data System (ADS)

Zhou, Zhenzhen; Liu, Guanghui; Wan, Jieqiong; Ni, Jia; Lu, Zhouguang; Ma, Ruguang; Zhou, Yao; Wang, Jiacheng; Liu, Qian

2016-04-01

Tunable white light was realized in samples Ba2(1- x)TiP2O9:2 xEu ( x = 0-0.80) by introducing orange-red light emitting Eu3+ in self-activated blue-green light emitting matrix Ba2TiP2O9. The sample Ba2(1- x)TiP2O9:2 xEu is a multiphase system consisting of Ba2TiP2O9, EuPO4 and TiO2 when x is greater than or equal to 0.20. The tunable light from blue-green to bluish-white, to white, and eventually to pinky-white of samples Ba2(1- x)TiP2O9:2 xEu under UV light excitation is attributed to the light mixture of tunable blue-green light from Ti4+-O2- charge transfer transition in Ba2TiP2O9 and orange-red light from Eu3+ 4f-4f transition mostly in EuPO4. The Commission International de l'Eclairage chromaticity coordinates, correlated color temperature and color rendering index were tuned from (0.262, 0.339), 9492 K and 74 for matrix sample Ba2TiP2O9 to (0.324, 0.346), 5876 K and 87 for sample Ba2(1- x)TiP2O9:2 xEu ( x = 0.40) under UV light excitation. Therefore, a kind of promising UV-excited white light emitting multiphase phosphor was obtained.

Structural, electrical and optical characterization of high brightness phosphor-free white light emitting diodes

NASA Astrophysics Data System (ADS)

Omiya, Hiromasa

Much interest currently exists in GaN and related materials for applications such as light-emitting devices operating in the amber to ultraviolet range. Solid-state lighting (SSL) using these materials is widely being investigated worldwide, especially due to their high-energy efficiency and its impact on environmental issues. A new approach for solid-state lighting uses phosphor-free white light emitting diodes (LEDs) that consist of blue, green, and red quantum wells (QW), all in a single device. This approach leads to improved color rendering, and directionality, compared to the conventional white LEDs that use yellow phosphor on blue or ultraviolet emitters. Improving the brightness of these phosphor-free white LEDs should enhance and accelerate the development of SSL technology. The main objective of the research reported in this dissertation is to provide a comprehensive understanding of the nature of the multiple quantum wells used in phosphor-free white LEDs. This dissertation starts with an introduction to lighting history, the fundamental concepts of nitride semiconductors, and the evolution of LED technology. Two important challenges in LED technology today are metal-semiconductor contacts and internal piezoelectric fields present in quantum well structures. Thus, the main portion of this dissertation consists of three parts dealing with metal-semiconductor interfaces, single quantum well structures, and multiple quantum well devices. Gold-nickel alloys are widely used as contacts to the p-region of LEDs. We have performed a detailed study for its evolution under standard annealing steps. The atomic arrangement of gold at its interface with GaN gives a clear explanation for the improved ohmic contact performance. We next focus on the nature of InGaN QWs. The dynamic response of the QWs was studied with electron holography and time-resolved cathodoluminescence. Establishing the correlation between energy band structure and the light emission spectra

Highly Efficient Broadband Yellow Phosphor Based on Zero-Dimensional Tin Mixed-Halide Perovskite.

PubMed

Zhou, Chenkun; Tian, Yu; Yuan, Zhao; Lin, Haoran; Chen, Banghao; Clark, Ronald; Dilbeck, Tristan; Zhou, Yan; Hurley, Joseph; Neu, Jennifer; Besara, Tiglet; Siegrist, Theo; Djurovich, Peter; Ma, Biwu

2017-12-27

Organic-inorganic hybrid metal halide perovskites have emerged as a highly promising class of light emitters, which can be used as phosphors for optically pumped white light-emitting diodes (WLEDs). By controlling the structural dimensionality, metal halide perovskites can exhibit tunable narrow and broadband emissions from the free-exciton and self-trapped excited states, respectively. Here, we report a highly efficient broadband yellow light emitter based on zero-dimensional tin mixed-halide perovskite (C 4 N 2 H 14 Br) 4 SnBr x I 6-x (x = 3). This rare-earth-free ionically bonded crystalline material possesses a perfect host-dopant structure, in which the light-emitting metal halide species (SnBr x I 6-x 4- , x = 3) are completely isolated from each other and embedded in the wide band gap organic matrix composed of C 4 N 2 H 14 Br - . The strongly Stokes-shifted broadband yellow emission that peaked at 582 nm from this phosphor, which is a result of excited state structural reorganization, has an extremely large full width at half-maximum of 126 nm and a high photoluminescence quantum efficiency of ∼85% at room temperature. UV-pumped WLEDs fabricated using this yellow emitter together with a commercial europium-doped barium magnesium aluminate blue phosphor (BaMgAl 10 O 17 :Eu 2+ ) can exhibit high color rendering indexes of up to 85.

A novel red phosphor of seven-coordinated Mn4+ ion-doped tridecafluorodizirconate Na5Zr2F13 for warm WLEDs.

PubMed

Xi, Luqing; Pan, Yuexiao; Huang, Shaoming; Lian, Hongzhou; Lin, Jun

2018-04-24

Herein, a novel red phosphor based on seven-coordinated Mn4+ ion-doped tridecafluorodizirconate, Na5Zr2F13 (NZF), has been synthesized by stirring a mixture of K2MnF6, NaF, and H2ZrF6 at room temperature. The crystal structure and morphology of the as-obtained phosphor NZF:Mn have been determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The composition and distribution of Mn4+ ions in NZF have been confirmed by energy-dispersive spectroscopy (EDS) and element mapping via transmission electron microscopy (TEM). The phosphor NZF:Mn exhibits a strong zero phonon line (ZPL) at 616 nm under excitation of blue light from a GaN light-emitting diode (LED) chip; this is attributed to the low symmetry of Mn4+ ions occupied in a seven-coordinated environment. The luminescence intensity of NZF:Mn has been optimized by controlling the synthesis procedure and synthetic parameters. The luminescence mechanism of the red phosphor NZF:Mn has been investigated according to the detailed experimental results. A warm white light has been produced by a WLED fabricated with the red phosphor NZF:Mn and the commercial yellow phosphor Y3Al5O12:Ce3+ (YAG:Ce) on a GaN LED chip.

Enhanced red fluorescence in Sr2Si1-xGexO4:Eu3+ phosphors by the substitution of Si by Ge for white light emitting diodes

NASA Astrophysics Data System (ADS)

Huang, Lihui; Xu, Shiqing; Guo, Meiquan; Wang, Chenyue; Hua, Youjie; Zhao, Shilong; Deng, Degang; Wang, Huanping; Jia, Guohua

2012-07-01

Eu3+-doped Sr2Si1-xGexO4 (x=0-1) phosphors have been prepared by the high temperature solid-state reaction method. The luminescent properties of these phosphors were investigated. Red fluorescence of Eu3+ is enhanced gradually in the samples with increasing substitution of Si by Ge upon the excitation of 393 nm light. The intensity is increased by 50% with full substitution of Si by Ge. These results are originated from the structural changes and the phonon energy reduction in the samples due to the substitution of Si by Ge. The CIE chromaticity coordinates of the phosphors vary slightly around (0.62, 0.37) and all are in the red color region. The results indicate that these phosphors could be promising red phosphors for white light emitting diodes.

Optimization of photoluminescence of GdAl3(BO3)4:Sm3+ phosphors for solid state lighting devices

NASA Astrophysics Data System (ADS)

Jamalaiah, Bungala Chinna

2017-10-01

The GdAl3(BO3)4:Sm3+ phosphors prepared by solid-state reaction method were characterized through thermal, structural and photoluminescence studies at room temperature only. The observed X-ray diffraction peaks were well consistent with JCPDS No. 83-1907. When excited with 406 nm wavelength, the studied phosphors exhibit orange-red luminescence through 4G5/2 → 6H5/2, 4G5/2 → 6H7/2 and 4G5/2 → 6H9/2 transitions. The concentration of Sm3+ ions was optimized to be 0.01 mol% for intense luminescence in GdAl3(BO3)4:Sm3+ phosphors. Beyond 0.01 mol% of Sm3+ ions concentration, luminescence quenching was observed due to energy transfer among the excited Sm3+ ions through cross-relaxation and dipole-dipole interaction mechanisms. The GdAl3(BO3)4:0.01 mol% Sm3+ phosphor was identified as a notable host material to emit intense orange-red luminescence for various solid state lighting devices under 406 nm excitation.

Sintering temperature effect of divalent europium ion doped tetra-calcium phosphate phosphors for latent fingerprint detection

NASA Astrophysics Data System (ADS)

Hong, Woo Tae; Park, Jin Young; Je, Jae-Yong; Yang, Hyun Kyoung

2018-07-01

Ca4(PO4)2O:Eu2+ (CPO:Eu2+) phosphors were successfully synthesized by high-energy ball milling. In order to study the effect of sintering temperature, the phosphors were synthesized at various sintering temperatures. The crystal structure of CPO:Eu2+ was determined to be monoclinic P21. Owing to the f-d transitions of the Eu2+ ions in the CPO:Eu2+ phosphors, the PL spectra of the phosphors showed an intense red emission centered at 635 nm with 418 nm excitation. Using high-energy ball milling, a more intense emission (compared to that reported from other research) can be visually observed with human eyes in the form of orange-red light, which is helpful in latent fingerprint detection. In addition, high-temperature sintering results in an increase of the PL intensity owing to the larger particle size and lower levels of impurities in the CPO:Eu2+ phosphors. The latent fingerprint image obtained by using CPO:Eu2+ phosphors reveals a high contrast for various substrate materials, because the phosphors exhibit strong red emission and adhere to the residue of the fingerprint after flowing. On the basis of these results, red-emitting CPO:Eu2+ phosphors can be used for the detection of latent fingerprints in solving criminal cases.

Blue light emitting thiogallate phosphor

DOEpatents

Dye, Robert C.; Smith, David C.; King, Christopher N.; Tuenge, Richard T.

1998-01-01

A crystalline blue emitting thiogallate phosphor of the formula RGa.sub.2 S.sub.4 :Ce.sub.x where R is selected from the group consisting of calcium, strontium, barium and zinc, and x is from about 1 to 10 atomic percent, the phosphor characterized as having a crystalline microstructure on the size order of from about 100 .ANG. to about 10,000 .ANG. is provided together with a process of preparing a crystalline blue emitting thiogallate phosphor by depositing on a substrate by CVD and resultant thin film electroluminescent devices including a layer of such deposited phosphor on an ordinary glass substrate.

White polymer light-emitting diodes based on star-shaped polymers with an orange dendritic phosphorescent core.

PubMed

Zhu, Minrong; Li, Yanhu; Cao, Xiaosong; Jiang, Bei; Wu, Hongbin; Qin, Jingui; Cao, Yong; Yang, Chuluo

2014-12-01

A series of new star-shaped polymers with a triphenylamine-based iridium(III) dendritic complex as the orange-emitting core and poly(9,9-dihexylfluorene) (PFH) chains as the blue-emitting arms is developed towards white polymer light-emitting diodes (WPLEDs). By fine-tuning the content of the orange phosphor, partial energy transfer and charge trapping from the blue backbone to the orange core is realized to achieve white light emission. Single-layer WPLEDs with the configuration of ITO (indium-tin oxide)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/polymer/CsF/Al exhibit a maximum current efficiency of 1.69 cd A(-1) and CIE coordinates of (0.35, 0.33), which is very close to the pure white-light point of (0.33, 0.33). To the best of our knowledge, this is the first report on star-shaped white-emitting single polymers that simultaneously consist of fluorescent and phosphorescent species. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Improved color stability of white organic light-emitting diodes without interlayer between red, orange and blue emission layers

NASA Astrophysics Data System (ADS)

Xue, Kaiwen; Chen, Ping; Duan, Yu; Sheng, Ren; Han, Guangguang; Zhao, Yi

2016-03-01

We demonstrated color stability improved white phosphorescent organic light-emitting diodes (WOLEDs) based on red, orange and blue emission layers. Iridium(III) Bis(3,5-diflouro)-2-(2-pyridyl)phenyl-(2-carboxypyridyl) was doped into red emission layer (R-EML) and orange emission layer (O-EML) to lower the electrons injection barrier and facilitate the ambipolar charge carriers balance. Consequently, the recombination region was extended to the R-EML and O-EML, leading to the excellently stable spectra and the reduction of triplet-triplet annihilation. Then the resulting device with a negligible Commission International de L'Eclairage coordinates shift of (0.003, 0.007) within a wide luminance range as well as a high color rendering index of 90 was gained, which was comparable to the profit caused by the conventional method of introducing the interlayer. And the emission mechanism of the WOLEDs was also discussed.

High color rendering index of remote-type white LEDs with multi-layered quantum dot-phosphor films and short-wavelength pass dichroic filters

NASA Astrophysics Data System (ADS)

Yoon, Hee Chang; Oh, Ji Hye; Do, Young Rag

2014-09-01

This paper introduces high color rendering index (CRI) white light-emitting diodes (W-LEDs) coated with red emitting (Sr,Ca)AlSiN3:Eu phosphors and yellowish-green emitting AgIn5S8/ZnS (AIS/ZS) quantum dots (QDs) on glass or a short-wavelength pass dichroic filter (SPDF), which transmit blue wavelength regions and reflect yellow wavelength regions. The red emitting (Sr,Ca)AlSiN3:Eu phosphor film is coated on glass and a SPDF using a screen printing method, and then the yellowish-green emitting AIS/ZS QDs are coated on the red phosphor (Sr,Ca)AlSiN3:Eu film-coated glass and SPDF using the electrospray (e-spray) method.To fabricate the red phosphor film, the optimum amount of phosphor is dispersed in a silicon binder to form a red phosphor paste. The AIS/ZS QDs are mixed with dimethylformamide (DMF), toluene, and poly(methyl methacrylate) (PMMA) for the e-spray coating. The substrates are spin-coated with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) to fabricate a conductive surface. The CRI of the white LEDs is improved through inserting the red phosphor film between the QD layer and the glass substrate. Furthermore, the light intensities of the multi-layered phosphor films are enhanced through changing the glass substrate to the SPDF. The correlated color temperatures (CCTs) vary as a function of the phosphor concentration in the phosphor paste. The optical properties of the yellowish-green AIS/ZS QDs and red (Sr,Ca)AlSiN3:Eu phosphors are characterized using photoluminescence (PL), and the multi-layered QD-phosphor films are measured using electroluminescence (EL) with an InGaN blue LED (λmax = 450 nm) at 60 mA.

A WLED based on LuAG:Ce3+ PiG coated red-emitting K2SiF6:Mn4+ phosphor by screen-printing

NASA Astrophysics Data System (ADS)

Cao, Rui; Wu, Lingchao; Di, Xiaoxuan; Li, Pengzhi; Hu, Guangcai; Liang, Xiaojuan; Xiang, Weidong

2017-08-01

It is high-profile that the use of phosphor-in-glass (PiG) is extensive because of its excellent advantages in thermal resistance and lifetime aspects, and so on. Here, white light-emitting diodes (WLED) based on LuAG:Ce3+ PiG coated red-emitting K2SiF6:Mn4+ (KSF) phosphors by screen-printing are fabricated. Among all of these, the commercial LuAG phosphors and glass raw materials of TeO2-based glass, were weighted and milled in an agate thoroughly. Then, the mixture was melted and sintered at 850 K or so for 20 min in the ambient atmosphere through low temperature co-fired method, cold-forming LuAG PiG clump and cut into different LuAG PiG thicknesses. After that, the commercial red phosphor KSF was coated on LuAG PiG by screen-printing technique. Finally, high-performance WLEDs based on the TeO2-based glass were obtained, tested and characterized, which exhibit a highest color rendering index of 94.1, a lowest color temperature of 3744 K and a largest luminous efficiency of 101.02 lm·W-1. Most noticeably of all, the promising method has excellent developing potential for industrialization in high-power WLED.

Facile solution-precipitation assisted synthesis and luminescence property of greenish-yellow emitting Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} phosphor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ji, Haipeng; Huang, Zhaohui, E-mail: huang118@cugb.edu.cn; Xia, Zhiguo, E-mail: xiazg@ustb.edu.cn

2016-03-15

Highlights: • Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} phosphor was prepared by the solution-precipitation assisted route. • The phosphors have satisfactory smooth grain surface and particle size. • It shows greenish-yellow color emission (maximum at 540 nm) upon blue light excitation. • Eu{sup 2+} is coordinated with isolated oxygen atoms and those from PO{sub 4} polyhedra. - Abstract: Greenish-yellow emitting microcrystalline Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} phosphor was successfully prepared by a solution-precipitation assisted high temperature reaction method. Phase structure, morphology and/or luminescence properties of the precursor and the as-prepared phosphors were characterized. The phase-pure Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} phosphorsmore » were obtained with smooth grain surface and particle size of 2–8 μm. Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} exhibits bright greenish-yellow color emission with its maximum at 540 nm upon UV-blue light excitation. The maximum position of the broad emission band is independent on the calcination temperature. The emission intensity increases with increasing calcination temperature due to improved crystallinity. Besides, the presence of two Eu{sup 2+} emission centers in the Ca{sub 6}Ba(PO{sub 4}){sub 4}O crystal lattice was confirmed and the coordination effects are considered concerning the roles of isolated O atoms and those from the PO{sub 4} tetrahedra.« less

Abnormal site occupancy and high performance in warm WLEDs of a novel red phosphor, NaHF2:Mn4+, synthesized at room temperature.

PubMed

Xi, Luqing; Pan, Yuexiao; Zhu, Mengmeng; Lian, Hongzhou; Lin, Jun

2017-10-17

A novel red phosphor, NaHF 2 :Mn 4+ (NHF:Mn), was obtained via substituting Na + located at the center of the octahedron coordinated with six F - ions with Mn 4+ in the host lattice of NHF. The phase purity and the exact composition of the obtained NHF:Mn were confirmed by X-ray powder diffraction (XRD), Rietveld refinement, energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and infrared (IR) spectroscopy, respectively. The luminescence intensity of NHF:Mn was enhanced by optimizing the synthetic conditions. A series of warm white light-emitting diodes (WLEDs) with a color rendering index (CRI) higher than 88.0 and correlated color temperatures (CCT) between 3146 and 5172 K were obtained by encapsulating the as-prepared red phosphor NHF:Mn with the yellow one Y 3 Al 5 O 12 :Ce 3+ (YAG:Ce) on blue chips. The advantage of the synthetic strategy to obtain NHF:Mn can be extended to develop novel Mn 4+ doped red phosphors via substituting for central ions with unequal electric charge in the centers of octahedra.

Synthesis and properties of Rb2GeF6:Mn4+ red-emitting phosphors

NASA Astrophysics Data System (ADS)

Sakurai, Shono; Nakamura, Toshihiro; Adachi, Sadao

2018-02-01

Rb2GeF6:Mn4+ red-emitting phosphors were synthesized by coprecipitation and their structural and optical properties were investigated by laser microscopy observation, X-ray diffraction (XRD) analysis, photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, and PL decay measurement. Single-crystalline ingots in the form of a hexagonal pyramid were prepared with a basal plane diameter of ˜2 mm. The XRD analysis suggested that Rb2GeF6 crystallizes in the hexagonal structure (C6v4 = P63mc) with a = 0.5955 nm and c = 0.9672 nm. The phosphor exhibited the strong Mn4+-related zero-phonon line (ZPL) emission peak typically observed in host crystals with piezoelectrically active lattices such as a hexagonal lattice. The quantum efficiencies of the bulk ingot and powdered samples were 87 and 74%, respectively, with nearly the same luminescence decay time of ˜6 ms. The exact ZPL energies and related crystal-field and Racah parameters were obtained from the PL and PLE spectra by Franck-Condon analysis. Temperature-dependent PL intensities were analyzed from T = 20 to 500 K using a thermal quenching model by considering Bose-Einstein phonon statistics. A comparative discussion on the phosphor properties of Rb2GeF6:Mn4+ and Rb2MF6:Mn4+ with M = Si and Ti was also given.

Structure, luminescence and thermal quenching properties of Eu doped Sr{sub 2−x}Ba{sub x}Si{sub 5}N{sub 8} red phosphors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Y.H.; Chen, L.; Zhou, X.F.

Eu{sup 2+} doped Sr{sub 2-x}Ba{sub x}Si{sub 5}N{sub 8} phosphors were synthesized at 1610 ℃ for 4 h via the solid-state reaction method. The XRD results confirm that the complete solid solutions are formed. With the increase of x, the emission spectra show an obvious blue-shift from 610 nm to 585 nm under the excitation of 460 nm. The color tone can be tuned from yellow to red. The corresponding mechanism for the blue-shift of peak-wavelength is studied in detail. The results of decomposed Gaussian spectra and fluorescence lifetime show that the local coordination structure surrounding activator ions changes with increasingmore » x value. It is found that the probability of Eu occupying Sr1 and Sr2 site is dependent on Ba/Sr ratio. The variation of thermal quenching properties and the corresponding mechanism is discussed in detail. The results indicate that Eu{sup 2+} doped Sr{sub 2-x}Ba{sub x}Si{sub 5}N{sub 8} is a promising orange red-emitting phosphor for near UV or blue light-pumped white light-emitting-diodes (wLEDs). - Graphical abstract: Eu{sup 2+} doped Sr{sub 2-x}Ba{sub x}Si{sub 5}N{sub 8} solid solutions were prepared by the solid-state reaction method. The structure, luminescence and thermal quenching properties with varying Ba/Sr ratio were investigated in detail. - Highlights: • The stucture and luminescence properties of Eu doped Sr{sub 2-x}Ba{sub x}Si{sub 5}N{sub 8} phosphors were investigated. • The samples with the intermediate compositions(x=1.0,1.5) show better stability than the end members of both Sr{sub 2}Si{sub 5}N{sub 8}:Eu{sup 2+} and Ba{sub 2}Si{sub 5}N{sub 8}:Eu{sup 2+}. • The possible mechanism for the improvement of thermal quenching properties was proposed.« less

Postharvest responses of red and yellow sweet peppers grown under photo-selective nets.

PubMed

Selahle, Kamogelo M; Sivakumar, Dharini; Jifon, John; Soundy, Puffy

2015-04-15

Postharvest responses of red ('HTSP-3') and yellow ('Celaya') sweet pepper fruit yield, quality parameters and bioactive compounds (to three types of photo-selective nets and a standard black net) were investigated in this study. Red and yellow peppers produced under the black net retained higher β-carotene, lower total phenolic contents and showed deep red and orange colour after storage. Both peppers produced under the pearl net retained a higher ascorbic content, antioxidant scavenging activity, fruit firmness and also reduced weight loss after storage. Red and yellow peppers grown under pearl and yellow nets resulted in a higher percentage of marketable fruit, after storage. Red pepper grown under the yellow net showed a higher number of odour active aroma compounds in the fruit, while black nets significantly affected the synthesis of odour active aroma compounds during storage. Sensory analysis indicated a preference for red pepper fruits after storage from plants grown under pearl nets. Copyright © 2014 Elsevier Ltd. All rights reserved.

Fluorescent lighting with aluminum nitride phosphors

DOEpatents

Cherepy, Nerine J.; Payne, Stephen A.; Seeley, Zachary M.; Srivastava, Alok M.

2016-05-10

A fluorescent lamp includes a glass envelope; at least two electrodes connected to the glass envelope; mercury vapor and an inert gas within the glass envelope; and a phosphor within the glass envelope, wherein the phosphor blend includes aluminum nitride. The phosphor may be a wurtzite (hexagonal) crystalline structure Al.sub.(1-x)M.sub.xN phosphor, where M may be drawn from beryllium, magnesium, calcium, strontium, barium, zinc, scandium, yttrium, lanthanum, cerium, praseodymium, europium, gadolinium, terbium, ytterbium, bismuth, manganese, silicon, germanium, tin, boron, or gallium is synthesized to include dopants to control its luminescence under ultraviolet excitation. The disclosed Al.sub.(1-x)M.sub.xN:Mn phosphor provides bright orange-red emission, comparable in efficiency and spectrum to that of the standard orange-red phosphor used in fluorescent lighting, Y.sub.2O.sub.3:Eu. Furthermore, it offers excellent lumen maintenance in a fluorescent lamp, and does not utilize "critical rare earths," minimizing sensitivity to fluctuating market prices for the rare earth elements.

Thin-Film Photoluminescent Properties and the Atomistic Model of Mg2TiO4 as a Non-rare Earth Matrix Material for Red-Emitting Phosphor

NASA Astrophysics Data System (ADS)

Huang, Chieh-Szu; Chang, Ming-Chuan; Huang, Cheng-Liang; Lin, Shih-kang

2016-12-01

Thin-film electroluminescent devices are promising solid-state lighting devices. Red light-emitting phosphor is the key component to be integrated with the well-established blue light-emitting diode chips for stimulating natural sunlight. However, environmentally hazardous rare-earth (RE) dopants, e.g. Eu2+ and Ce2+, are commonly used for red-emitting phosphors. Mg2TiO4 inverse spinel has been reported as a promising matrix material for "RE-free" red light luminescent material. In this paper, Mg2TiO4 inverse spinel is investigated using both experimental and theoretical approaches. The Mg2TiO4 thin films were deposited on Si (100) substrates using either spin-coating with the sol-gel process, or radio frequency sputtering, and annealed at various temperatures ranging from 600°C to 900°C. The crystallinity, microstructures, and photoluminescent properties of the Mg2TiO4 thin films were characterized. In addition, the atomistic model of the Mg2TiO4 inverse spinel was constructed, and the electronic band structure of Mg2TiO4 was calculated based on density functional theory. Essential physical and optoelectronic properties of the Mg2TiO4 luminance material as well as its optimal thin-film processing conditions were comprehensively reported.

Health-friendly high-quality white light using violet-green-red laser and InGaN nanowires-based true yellow nanowires light-emitting diodes

NASA Astrophysics Data System (ADS)

Janjua, Bilal; Ng, Tien K.; Zhao, Chao; Anjum, Dalaver H.; Prabaswara, Aditya; Consiglio, Giuseppe Bernardo; Shen, Chao; Ooi, Boon S.

2017-02-01

White light based on blue laser - YAG: Ce3+ phosphor has the advantage of implementing solid-state lighting and optical wireless communications combined-functionalities in a single lamp. However, the blue light was found to disrupt melatonin production, and therefore the human circadian rhythm in general; while the yellow phosphor is susceptible to degradation by laser irradiation and also lack tunability in color rendering index (CRI). In this investigation, by using a violet laser, which has 50% less impact on circadian response, as compared to blue light, and an InGaN-quantum-disks nanowires-based light-emitting diode (NWs-LED), we address both issues simultaneously. The white light is therefore generated using violet-green-red lasers, in conjunction with a yellow NWs-LED realized using molecular beam epitaxy technique, on titanium-coated silicon substrates. Unlike the conventional quantum-well-based LED, the NWs-LED showed efficiency-droop free behavior up to 9.8 A/cm2 with peak output power of 400 μW. A low turn-on voltage of 2.1 V was attributed to the formation of conducting titanium nitride layer at NWs nucleation site and improved fabrication process in the presence of relatively uniform height distribution. The 3D quantum confinement and the reduced band bending improve carriers-wavefunctions overlap, resulting in an IQE of 39 %. By changing the relative intensities of the individual color components, CRI of >85 was achieved with tunable correlated color temperature (CCT), thus covering the desired room lighting conditions. Our architecture provides important considerations in designing smart solid-state lighting while addressing the harmful effect of blue light.

Luminescence properties of Na2Sr2Al2PO4Cl9:Sm3+ phosphor

NASA Astrophysics Data System (ADS)

Tamboli, Sumedha; Shahare, D. I.; Dhoble, S. J.

2018-04-01

A series of Sm3+ ions doped Na2Sr2Al2PO4Cl9 phosphors were synthesized via solid state synthesis method. Photoluminescence (PL) emission spectra were obtained by keeping excitation wavelength at 406 nm. Emission spectra show three emission peaks at 563 nm, 595 nm and 644 nm. The CIE chromaticity diagram shows emission colour of the phosphor in the orange-red region of the visible spectrum, indicating that the phosphor may be useful in preparing orange light-emitting diodes. Na2Sr2Al2PO4Cl9:Sm3+ phosphors were irradiated by γ-rays from a 60Co source and β-rays from a 90Sr source. Their thermoluminescence (TL) glow curves were obtained by Nucleonix 1009I TL reader. TL Trapping parameters such as activation energy of trapped electrons and order of kinetics were obtained by using Chen's peak shape method, Glow curve fitting method and initial rise method.

A photoswitchable orange-to-far-red fluorescent protein, PSmOrange.

PubMed

Subach, Oksana M; Patterson, George H; Ting, Li-Min; Wang, Yarong; Condeelis, John S; Verkhusha, Vladislav V

2011-07-31

We report a photoswitchable monomeric Orange (PSmOrange) protein that is initially orange (excitation, 548 nm; emission, 565 nm) but becomes far-red (excitation, 636 nm; emission, 662 nm) after irradiation with blue-green light. Compared to its parental orange proteins, PSmOrange has greater brightness, faster maturation, higher photoconversion contrast and better photostability. The red-shifted spectra of both forms of PSmOrange enable its simultaneous use with cyan-to-green photoswitchable proteins to study four intracellular populations. Photoconverted PSmOrange has, to our knowledge, the most far-red excitation peak of all GFP-like fluorescent proteins, provides diffraction-limited and super-resolution imaging in the far-red light range, is optimally excited with common red lasers, and can be photoconverted subcutaneously in a mouse. PSmOrange photoswitching occurs via a two-step photo-oxidation process, which causes cleavage of the polypeptide backbone. The far-red fluorescence of photoconverted PSmOrange results from a new chromophore containing N-acylimine with a co-planar carbon-oxygen double bond.

Highly efficient phosphor-converted white organic light-emitting diodes with moderate microcavity and light-recycling filters.

PubMed

Cho, Sang-Hwan; Oh, Jeong Rok; Park, Hoo Keun; Kim, Hyoung Kun; Lee, Yong-Hee; Lee, Jae-Gab; Do, Young Rag

2010-01-18

We demonstrate the combined effects of a microcavity structure and light-recycling filters (LRFs) on the forward electrical efficiency of phosphor-converted white organic light-emitting diodes (pc-WOLEDs). The introduction of a single pair of low- and high-index layers (SiO(2)/TiO(2)) improves the blue emission from blue OLED and the insertion of blue-passing and yellow-reflecting LRFs enhances the forward yellow emission from the YAG:Ce(3+) phosphors layers. The enhancement of the luminous efficacy of the forward white emission is 1.92 times that of a conventional pc-WOLED with color coordinates of (0.34, 0.34) and a correlated color temperature of about 4800 K.

Synthesis and photoluminescence properties of Ca{sub 19}Mg{sub 2}(PO{sub 4}){sub 14}:Sm{sup 3+} red phosphor for white light emitting diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Ge; Ci, Zhipeng; Shi, Yurong

2014-07-01

Highlights: • A novel red phosphor Ca{sub 19}Mg{sub 2}(PO{sub 4}){sub 14}:Sm{sup 3+} was synthesized and investigated firstly. • The structure and characteristic luminescence properties are discussed. • The excellent thermal stability was found and investigated. • It has good color saturation, the CIE is close to that of commercial Y{sub 2}O{sub 3}:Eu{sup 3+}. - Abstract: A series of Sm{sup 3+} doped Ca{sub 19}Mg{sub 2}(PO{sub 4}){sub 14} red phosphors were successfully synthesized. X-ray diffraction analysis indicates that all the samples are single phased. The luminescence property is investigated in detail by measuring their photoluminescence excitation and emission spectra. Ca{sub 19}Mg{sub 2}(PO{submore » 4}){sub 14}:Sm{sup 3+} phosphors show strong absorption in 400–410 nm region, which is suitable for application in LEDs. When excited at 403 nm, Ca{sub 19}Mg{sub 2}(PO{sub 4}){sub 14}:Sm{sup 3+} phosphor can emit red emission with CIE chromaticity coordinates (0.615, 0.384). The optimal doping concentration of Sm{sup 3+} doped Ca{sub 19}Mg{sub 2}(PO{sub 4}){sub 14} is measured to be 0.02. The thermal quenching property is also measured and compared with the commercial red phosphor Y{sub 2}O{sub 3}:Eu{sup 3+} (Topstar, TXC-RIA). The results indicate Ca{sub 19}Mg{sub 2}(PO{sub 4}){sub 14}:Sm{sup 3+} phosphors have potential to serve as a red phosphor for white LEDs.« less

Gigabit-per-second white light-based visible light communication using near-ultraviolet laser diode and red-, green-, and blue-emitting phosphors.

PubMed

Lee, Changmin; Shen, Chao; Cozzan, Clayton; Farrell, Robert M; Speck, James S; Nakamura, Shuji; Ooi, Boon S; DenBaars, Steven P

2017-07-24

Data communication based on white light generated using a near-ultraviolet (NUV) laser diode (LD) pumping red-, green-, and blue-emitting (RGB) phosphors was demonstrated for the first time. A III-nitride laser diode (LD) on a semipolar (2021¯)  substrate emitting at 410 nm was used for the transmitter. The measured modulation bandwidth of the LD was 1 GHz, which was limited by the avalanche photodetector. The emission from the NUV LD and the RGB phosphor combination measured a color rendering index (CRI) of 79 and correlated color temperature (CCT) of 4050 K, indicating promise of this approach for creating high quality white lighting. Using this configuration, data was successfully transmitted at a rate of more than 1 Gbps. This NUV laser-based system is expected to have lower background noise from sunlight at the LD emission wavelength than a system that uses a blue LD due to the rapid fall off in intensity of the solar spectrum in the NUV spectral region.

A novel red phosphor Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2}:Eu{sup 3+} for near UV white light-emitting diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Zhigang; Zhao, Zhengyan; Shi, Yurong

2013-10-15

Graphical abstract: - Highlights: • Novel red phosphor Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2}:Eu{sup 3+} was prepared by solid-state reaction. • Excitation spectra suggested an obvious absorption in near-ultraviolet region. • Under 392 nm excitation, the phosphors exhibited a red emission at 614 nm. • Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2}:Eu{sup 3+} could be potentially applied in near UV white LEDs. - Abstract: A novel red phosphor Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2}:Eu{sup 3+} was synthesized using a solid-state reaction method, and its luminescence characteristics and charge compensators effect (Li{sup +}, Na{sup +}, K{sup +}) were investigated. The excitation spectra showed a obviousmore » absorption in near-ultraviolet region. Under 392 nm excitation, the phosphors exhibited an intense red emission at 614 nm. The Commission Internationale de l’Eclairage (CIE) chromaticity coordinates and quantum efficiency (QE) were (0.65, 0.35) and 62.3%, respectively. The good color saturation, high quantum efficiency and small thermal-quenching properties indicate that Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2}:Eu{sup 3+} could be potentially applied in near UV white light-emitting diodes.« less

Red emission phosphor for real-time skin dosimeter for fluoroscopy and interventional radiology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakamura, Masaaki, E-mail: QYJ05476@nifty.com; Chida, Koichi; Zuguchi, Masayuki

2014-10-15

Purpose: There are no effective real-time direct skin dosimeters for interventional radiology. Such a scintillation dosimeter would be available if there was a suitable red emission phosphor in the medical x-ray range, since the silicon photodiode is a highly efficient device for red light. However, it is unknown whether there is a suitable red emission phosphor. The purpose of this study is to find a suitable red emission phosphor that can be used in x-ray dosimeters. Methods: Five kinds of phosphors which emit red light when irradiated with electron beams or ultraviolet rays in practical devices were chosen. For themore » brightness measurement, phosphor was put into transparent plastic cells or coated onto plastic sheets. The phosphors were irradiated with medical range x-rays [60–120 kV(peak), maximum dose rate of 160 mGy min{sup −1}], and the emission was measured by a luminance meter. Several characteristics, such as brightness, dose rate dependence, tube voltage dependence, and brightness stability, were investigated. Results: The luminescence of Y V O{sub 4}:Eu, (Y,Gd,Eu) BO{sub 3}, and Y{sub 2}O{sub 3}:Eu significantly deteriorated by 5%–10% when irradiated with continuous 2 Gy x-rays. The 0.5MgF{sub 2}⋅3.5MgO⋅GeO{sub 2}:Mn phosphor did not emit enough. Only the Y{sub 2}O{sub 2}S:Eu,Sm phosphor had hardly any brightness deterioration, and it had a linear relationship so that the x-ray dose rate could be determined from the brightness with sufficient accuracy. For the tube voltage dependence of the Y{sub 2}O{sub 2}S:Eu,Sm phosphor, the brightness per unit dose rate with 120 kV(peak) x-rays was 30% higher than that with 60 kV(peak) x-rays. Conclusions: Five kinds of phosphors were chosen as an x-ray scintillator for a real-time direct skin dosimeter. The Y V O{sub 4}:Eu, (Y,Gd,Eu)BO{sub 3}, and Y{sub 2}O{sub 3}:Eu phosphors had brightness deterioration caused by the x-rays. Only the Y{sub 2}O{sub 2}S:Eu,Sm phosphor had hardly any brightness

Blue light hazard performance comparison of phosphor-converted LED sources with red quantum dots and red phosphor

NASA Astrophysics Data System (ADS)

Zhang, Jingjing; Xie, Bin; Yu, Xingjian; Luo, Xiaobing; Zhang, Tao; Liu, Shishen; Yu, Zhihua; Liu, Li; Jin, Xing

2017-07-01

In this study, the blue light hazard performances of phosphor converted-light-emitting diodes (pc-LEDs) with red phosphor and red quantum dots (QDs) were compared and analyzed by spectral optimization, which boosts the minimum attainable blue light hazard efficiency of radiation (BLHER) at high values of color rendering index (CRI) and luminous efficacy of radiation (LER) when the correlated color temperature (CCT) value changes from 1800 to 7800 K. It is found that the minimal BLHER value increases with the increase in the CCT value, and the minimal BLHER values of the two spectral models are nearly the same. Note that the QDs' model has advantages at CCT coverage under the same constraints of CRI and LER. Then, the relationships between minimal BLHER, CRI, CCT, and LER of pc-LEDs with QDs' model were analyzed. It is found that the minimal BLHER values are nearly the same when the CRI value changes from 50 to 90. Therefore, the influence of CRI on minimal BLHER is insignificant. Minimal BLHER increases with the increase in the LER value from 240 to 360 lm/W.

High performance flexible top-emitting warm-white organic light-emitting devices and chromaticity shift mechanism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Hongying; Deng, Lingling; Chen, Shufen, E-mail: iamsfchen@njupt.edu.cn, E-mail: wei-huang@njupt.edu.cn

2014-04-15

Flexible warm-white top-emitting organic light-emitting devices (TEOLEDs) are fabricated onto PET substrates with a simple semi-transparent cathode Sm/Ag and two-color phosphors respectively doped into a single host material TCTA. By adjusting the relative position of the orange-red EML sandwiched between the blue emitting layers, the optimized device exhibits the highest power/current efficiency of 8.07 lm/W and near 13 cd/A, with a correlated color temperature (CCT) of 4105 K and a color rendering index (CRI) of 70. In addition, a moderate chromaticity variation of (-0.025, +0.008) around warm white illumination coordinates (0.45, 0.44) is obtained over a large luminance range ofmore » 1000 to 10000 cd/m{sup 2}. The emission mechanism is discussed via delta-doping method and single-carrier device, which is summarized that the carrier trapping, the exciton quenching, the mobility change and the recombination zone alteration are negative to color stability while the energy transfer process and the blue/red/blue sandwiched structure are contributed to the color stability in our flexible white TEOLEDs.« less

New localized/delocalized emitting state of Eu 2+ in orange-emitting hexagonal EuAl 2O 4

DOE PAGES

Liu, Feng; Meltzer, Richard S.; Li, Xufan; ...

2014-11-18

Eu 2+-activated phosphors are being widely used in illuminations and displays. Some of these phosphors feature an extremely broad and red-shifted Eu 2+ emission band; however, convincing explanation of this phenomenon is lacking. Here we report a new localized/delocalized emitting state of Eu 2+ ions in a new hexagonal EuAl 2O 4 phosphor whose Eu 2+ luminescence exhibits a very large bandwidth and an extremely large Stokes shift. At 77 K, two luminescent sites responsible for 550 nm and 645 nm broadband emissions are recognized, while at room temperature only the 645 nm emission band emits. The 645 nm emissionmore » exhibits a typical radiative lifetime of 1.27 μs and an unusually large Stokes shift of 0.92 eV. We identify the 645 nm emission as originating from a new type of emitting state whose composition is predominantly that of localized 4f 65d character but which also contains a complementary component with delocalized conduction-band-like character. This investigation gives new insights into a unique type of Eu 2+ luminescence in solids whose emission exhibits both a very large bandwidth and an extremely large Stokes shift.« less

Low roll-off and high efficiency orange OLEDs using green and red dopants in an exciplex forming co-host

NASA Astrophysics Data System (ADS)

Lee, Sunghun; Kim, Kwon-Hyeon; Yoo, Seung-Jun; Park, Young-Seo; Kim, Jang-Joo

2013-09-01

We present high efficiency orange emitting OLEDs with low driving voltage and low roll-off of efficiency using an exciplex forming co-host by (1) co-doping of green and red emitting phosphorescence dyes in the host and (2) red and green phosphorescent dyes doped in the host as separate red and green emitting layers. The orange OLEDs achieved a low turn-on voltage of 2.4 V and high external quantum efficiencies (EQE) of 25.0% and 22.8%, respectively. Moreover, the OLEDs showed low roll-off of efficiency with an EQE of over 21% and 19.6% at 10,000 cd/m2, respectively. The devices displayed good orange color with very little color shift with increasing luminance. The transient electroluminescence of the OLEDs indicated that both energy transfer and direct charge trapping took place in the devices.

Low-Yellowing Phosphor-in-Glass for High-Power Chip-on-board White LEDs by Optimizing a Low-Melting Sn-P-F-O Glass Matrix.

PubMed

Yoon, Hee Chang; Yoshihiro, Kouhara; Yoo, Heeyeon; Lee, Seung Woo; Oh, Ji Hye; Do, Young Rag

2018-05-09

We introduce a low-melting-point (MP) Sn-P-F-O glass ceramic material into the phosphor-in-glass (PIG) material to realize an 'on-chip' chip-on-board (COB) type of phosphor-converted (pc) white light-emitting diode (WLED) with green (BaSr) 2 SiO 4 :Eu 2+ and red (SrCa)AlSiN 3 :Eu 2+ (SCASN) phosphors. The optimum Sn-P-F-O-based ceramic components can be sintered into the glass phase with a facile one-step heating process at 285 °C for 1 min. Specifically, these soft-fabrication conditions can be optimized to minimize the degradation of the luminescent properties of the red SCASN phosphor as well as the green silicate phosphor in PIG-based white COB-type pc-LEDs owing to the low thermal loss of the phosphors at low fabrication temperatures below 300 °C. Moreover, the constituents of the COB package, in this case the wire bonding and plastic exterior, can be preserved simultaneously from thermal damage. That is, the low sintering temperature of the glass ceramic encapsulant is a very important factor to realize excellent optical qualities of white COB LEDs. The optical performances of low-MP Sn-P-F-O-based PIG on-chip COB-type pc-WLEDs exhibit low yellowing phenomena, good luminous efficacy of 70.9-86.0 lm/W, excellent color rendering index of 94-97 with correlated color temperatures from 2700 to 10000 K, and good long-term stability.

Hydrothermal synthesis infrared to visible upconversion luminescence of SrMoO4: Er3+/Yb3+ phosphor

NASA Astrophysics Data System (ADS)

Sinha, Shriya; Kumar, Kaushal

2018-04-01

The upconversion emission properties in Er3+/Yb3+ doped SrMoO4 phosphor synthesized via hydrothermal method is investigated upon 980 nm laser light excitation. The crystal structure and morphology of the synthesized phosphor are characterized by X-ray diffraction and field emission scanning electron microscopy. The X-ray diffraction pattern suggests that SrMoO4 phosphor has tetragonal phase structure. The phosphor emits strong green (525 and 552 nm) and red (665 nm) UC emissions along with weak blue (410 and 488 nm) and near infrared (798 nm) emission bands. The color emitted from the phosphor is shifted from yellow to green region with increasing the power density from 15 to 65 W/cm2. The result indicates that the present material is suitable for making infrared to visible up-converts and display devices.

Degradation of phosphor-in-glass encapsulants with various phosphor types for high power LEDs

NASA Astrophysics Data System (ADS)

Iqbal, Fauzia; Kim, Sunil; Kim, Hyungsun

2017-10-01

In order to replace conventional silicone-based phosphor light emitting diodes (LEDs), inorganic color converters with high thermal stabilities and transparencies, i.e., phosphors-in-glass (PiGs), have been investigated as encapsulants for high-power LEDs. In this paper, the effect of various types of phosphors, i.e., LuAG (green, Lu3Al5O12:Ce3+), silicate (yellow, Sr2SiO4:Eu2+), CASN (red, CaAlSiN3:Eu2+), and oxynitride (yellow, (Sr,Ba) Si2O2N2:Eu2+), on the reliability/degradation of the remote PiG encapsulants is explored for high power LEDs. For this purpose, a glass composition (SiO2-B2O3-ZnO-Na2O) was separately mixed with each type of phosphor and then sintered at appropriate temperatures to make the corresponding PiG. The reliabilities of the formed PiGs were evaluated by standard accelerated-aging tests (85 °C/85% RH) for 1000 h. Luminosity losses and shifts in the Commission Internationale de l'Eclairage (CIE) coordinates of the PiGs were measured before and after aging. Thermal, and moisture-induced quenching behavior was also analyzed. The surface of PiGs with different phosphors degraded differently, possibly because of structural incompatibilities between the glass matrix and phosphor type. Determining the compatibility of the glass composition with the type of phosphor used is therefore important in order to ensure the long-term stabilities of encapsulants for use in commercial LEDs.

A novel yellow-emitting SrAlSi4N7:Ce3+ phosphor for solid state lighting: Synthesis, electronic structure and photoluminescence properties

NASA Astrophysics Data System (ADS)

Ruan, Jian; Xie, Rong-Jun; Funahashi, Shiro; Tanaka, Yoshinori; Takeda, Takashi; Suehiro, Takayuki; Hirosaki, Naoto; Li, Yuan-Qiang

2013-12-01

Ce3+-doped and Ce3+/Li+-codoped SrAlSi4N7 phosphors were synthesized by gas pressure sintering of powder mixtures of Sr3N2, AlN, α-Si3N4, CeN and Li3N. The phase purity, electronic crystal structure, photoluminescence properties of SrAlSi4N7:Ce3+(Ce3+/Li+) were investigated in this work. The band structure calculated by the DMol3 code shows that SrAlSi4N7 has a direct band gap of 3.87 eV. The single crystal analysis of Ce3+-doped SrAlSi4N7 indicates a disordered Si/Al distribution and nitrogen vacnacy defects. SrAlSi4N7 was identified as a major phase of the fired powders, and Sr5Al5Si21N35O2 and AlN as minor phases. Both Ce3+ and Ce3+/Li+ doped SrAlSi4N7 phosphors can be efficiently excited by near-UV or blue light and show a broadband yellow emission peaking around 565 nm. A highest external quantum efficiency of 38.3% under the 450 nm excitation was observed for the Ce3+/Li+-doped SrAlSi4N7 (5 mol%). A white light LED lamp with color temperature of 6300 K and color rendering index of Ra=78 was achieved by combining Sr0.97Al1.03Si3.997N\\94\\maccounttest14=t0005_18193 7:Ce3+0.03 with a commercial blue InGaN chip. It indicates that SrAlSi4N7:Ce3+ is a promising yellow emitting down-conversion phosphor for white LEDs.

2D photonic crystal layer assisted thiosilicate ceramic plate with red-emitting film for high quality w -LEDs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dai, Wubin; Lei, Yifeng; Zhou, Jia

In this work, we have succeeded in obtaining high quality warm w-light-emitting-diodes (LEDs) by adopting hybrid two-dimensional (2D) structure of SiNx photonic crystal layer (PCL) assisted cyan-emitting ceramic-plate thiosilicate SrLa2Si2S8:Ce3+ with red-emitting film SrLiAl3N4:Eu2+ phosphor on a 430 nm blue LED chip at 350 mA. 2D SiNx PCL was capped with thiosilicate is because it can enhance the luminous efficacy and maintain the low correlated color temperature (CCT) and high color-rendering index (CRI). High luminous efficacy (82.3 lm/W), high special CRI (R9=75) as well as the low CCT (5431 K) of the optimal w-LED was obtained due to the assistancesmore » of 2D SiNx PCL and narrow-band red-emitting phosphor with the doping percentage at 10 wt%. The synthesis processes, structural analysis, optical properties and LED device performances were detailed investigated to find out the relationship between the optimum composition and good optical properties. Based on intriguing luminescence properties by the 2D SiNx PCL and red-emitting film phosphor introducing, we proclaim this method could also have high potential application in other phosphor-converted w-LEDs.« less

Novel Br-DPQ blue light-emitting phosphors for OLED.

PubMed

Dahule, H K; Thejokalyani, N; Dhoble, S J

2015-06-01

A new series of blue light-emitting 2,4-diphenylquinoline (DPQ) substituted blue light-emitting organic phosphors namely, 2-(4-methoxy-phenyl)-4-phenyl-quinoline (OMe-DPQ), 2-(4-methyl-phenyl)-4-phenylquinoline (M-DPQ), and 2-(4-bromo-phenyl)-4-phenylquinoline (Br-DPQ) were synthesized by substituting methoxy, methyl and bromine at the 2-para position of DPQ, respectively by Friedländer condensation of 2-aminobenzophenone and corresponding acetophenone. The synthesized phosphors were characterized by different techniques, e.g., Fourier transform infra-red (FTIR), differential scanning calorimeter (DSC), UV-visible absorption and photoluminescence spectra. FTIR spectra confirms the presence of chemical groups such as C=O, NH, or OH in all the three synthesized chromophores. DSC studies show that these complexes have good thermal stability. Although they are low-molecular-weight organic compounds, they have the potential to improve the stability and operating lifetime of a device made out of these complexes. The synthesized polymeric compounds demonstrate a bright emission in the blue region in the wavelength range of 405-450 nm in solid state. Thus the attachment of methyl, methoxy and bromine substituents to the diphenyl quinoline ring in these phosphors results in colour tuning of the phosphorescence. An electroluminescence (EL) cell of Br-DPQ phosphor was made and its EL behaviour was studied. A brightness-voltage characteristics curve of Br-DPQ cell revealed that EL begins at 400 V and then the brightness increases exponentially with applied AC voltage, while current-voltage (I-V) characteristics revealed that the turn on voltage of the fabricated EL cell was 11 V. Hence this phosphor can be used as a promising blue light material for electroluminescent devices. Copyright © 2014 John Wiley & Sons, Ltd.

UV-emitting phosphors: synthesis, photoluminescence and applications

NASA Astrophysics Data System (ADS)

Thakare, D. S.; Omanwar, S. K.; Muthal, P. L.; Dhopte, S. M.; Kondawar, V. K.; Moharil, S. V.

2004-02-01

UV-emitting phosphors find uses in various applications, such as photocopying, phototherapy, sun tanning, etc. The phosphor requirements for these applications vary. Simple methods for preparing different UV-emitting phosphors are described. Novel syntheses for some borates (SrB4O7:Eu, CeMgB5O10:Gd, GdBO3:Pr, LaB3O6:Ce,Bi, LaB3O6:Gd,Bi, LaB3O6:Ce, Ba2B5O9Cl:Eu), a silicate (Ba2SiO5:Pb), phosphates (Sr2-xMgxP2O7:Eu) and a sulphate (CaSO4:Eu) are reported. Photoluminescence spectra of the phosphors so prepared are presented and discussed in the context of applications like phototherapy and photocopying lamps, photoluminescent liquid crystal displays, radiophotoluminescence, etc.

Enhanced performances for top-emitting white organic light-emitting diodes by utilizing green phosphor as energy transfer medium

NASA Astrophysics Data System (ADS)

Deng, Lingling; Bao, Yiyang; Zhang, Yanan; Peng, Ling; Zhu, Wenjing; Zhao, Yue; Xu, Yewen; Chen, Shufen

2016-06-01

In top-emitting white organic light-emitting diodes (TWOLEDs), the device performances attribute to the several important factors, such as exciton profile, energy transfer, and microcavity effect. In this paper, a TWOLED containing a heterojunction blue emission layer (EML) and a red EML is reported. A host material with high triplet energy level is employed for the adjacent blue and red EML, while the inefficient red emission reduces the emission efficiency of the TWOLED. In order to enhance the red emission efficiency, mixed-host and co-doping technologies are used in the red EML. By mixing the hole transporting and electron transporting host materials, the exciton recombination zone extends to the red EML to increase the red emission intensity and reduce the efficiency roll-off. And by co-doping a green phosphor into the red EML as the energy transfer medium, the energy transfer rate is enhanced, and then the current efficiency increases. Besides, both the mixed-host and co-doping change the carrier transport and the exciton recombination zone, which further affects the microcavity resonance in the devices. Due to the enhancement on the red emission intensity and the shift of resonant wavelength, the chromaticity of the TWOLED is improved.

The photoluminescent properties of Y2O3:Bi3+, Eu3+, Dy3+ phosphors for white-light-emitting diodes.

PubMed

Han, Xiumei; Feng, Xu; Qi, Xiwei; Wang, Xiaoqiang; Li, Mingya

2014-05-01

Bi3+, Eu3+, Dy3+ activated Y2O3 phosphors were prepared through the sol-gel process. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, and photoluminescence (PL) spectra were used to characterize the resulting phosphors. The XRD patterns show the refined crystal structure of Y2O3. The energy transfer processes of Bi(3+)-Eu3+ occurred in the host lattices. The thermal stability of Y2O3:Bi3+, Eu3+, Dy3+ phosphors was studied. Under short wavelength UV excitation, the phosphors show excellent characteristic red, blue, and yellow emission with medium intensity.

Synthesis and photoluminescence properties of a cyan-emitting phosphor Ca3(PO4)2:Eu2+ for white light-emitting diodes

NASA Astrophysics Data System (ADS)

Zhou, Wenli; Han, Jin; Zhang, Xuejie; Qiu, Zhongxian; Xie, Qingji; Liang, Hongbin; Lian, Shixun; Wang, Jing

2015-01-01

In this paper, a cyan-emitting phosphor Ca3(PO4)2:Eu2+ (TCP:Eu2+) was synthesized and evaluated as a candidate for white light emitting diodes (WLEDs). This phosphor shows strong and broad absorption in 250-450 nm region, but the emission spectrum is prominent at around 480 nm. The emission intensity of the TCP:Eu2+ was found to be 60% and 82% of that of the commercial BaMgAl10O17:Eu2+ (BAM) under excitation at 340 nm and 370 nm, respectively. Upon excitation at 370 nm, the absolute internal and external quantum efficiencies of the Ca3(PO4)2:1.5%Eu2+ are 60% and 42%, respectively. Moreover, a white LED lamp was fabricated by coating TCP:Eu2+ with a blue-emitting BAM and a red-emitting CaAlSiN3:Eu2+ on a near-ultraviolet (375 nm) LED chip, driven by a 350 mA forward bias current, and it produces an intense white light with a color rendering index of 75.

Development of Eu3+ activated monoclinic, perovskite, and garnet compounds in the Gd2O3-Al2O3 phase diagram as efficient red-emitting phosphors

NASA Astrophysics Data System (ADS)

Li, Jinkai; Li, Ji-Guang; Li, Jing; Liu, Shaohong; Li, Xiaodong; Sun, Xudong; Sakka, Yoshio

2013-10-01

Eu3+ doped Gd4Al2O9 (GdAM), GdAlO3 (GdAP), and Gd3Al5O12 (GdAG, containing 10 at% of Lu3+ for lattice stabilization) have been developed in this work as efficient red-emitting phosphors. With coprecipitated carbonate precursors, phase evolution studies found minimum processing temperatures of ~1000, 1100, and 1300 °C for the three phosphors to crystallize as pure phases, respectively. Compared with their yttrium aluminate counterparts, the gadolinium-based phosphors exhibit red-shifted O2--Eu3+ charge transfer excitation band (CTB) centers due to the lower electronegativity of Gd3+ and appreciably higher quantum yields of photoluminescence owing to the occurrence of efficient Gd3+→Eu3+energy transfer. The optimal Eu3+ contents were determined to be ~7.5 at% for GdAM and 5.0 at% for both GdAP and GdAG, and concentration quenching of luminescence was suggested to be due to exchange interactions. Fluorescence decay analysis found a shorter lifetime for the phosphor powder processed at a higher temperature or with a higher Eu3+ content, and the underlying mechanism was discussed. Fluorescence lifetimes were also compared between the yttrium and gadolinium phosphor systems for the dominant emissions.

Increasing the effective absorption of Eu3+-doped luminescent materials towards practical light emitting diodes for illumination applications

NASA Astrophysics Data System (ADS)

van de Haar, Marie Anne; Werner, Jan; Kratz, Nadja; Hilgerink, Tom; Tachikirt, Mohamed; Honold, Jürgen; Krames, Michael R.

2018-03-01

White light emitting diodes (LEDs) composed of a blue LED and a green/yellow downconverter material (phosphor) can be very efficient, but the color is often not considered very pleasant. Although the color rendering can be improved by adding a second, red-emitting phosphor, this generally results in significantly reduced efficacy of the device due to the broad emission of available conventional red-emitting phosphors. Trivalent europium is well-known for its characteristic narrow-band emission in the red region, with little radiation outside the eye sensitivity area, making it an ideal candidate for enabling high color quality as well as a high lumen equivalent of radiation from a spectrum point of view. However, a thorough study of the practical potential and challenges of Eu3+ as a red emitter for white LEDs has remained elusive so far due to the low excitation probability in the blue spectral range which is often even considered a fundamental limitation. Here, we show that the absorption in the blue region can be brought into an interesting regime for white LEDs and show that it is possible to increase both the color rendering and efficacy simultaneously using Eu3+ as a red emitter, compared to warm white LEDs comprising conventional materials.

Rare-earth free self-luminescent Ca2KZn2(VO4)3 phosphors for intense white light-emitting diodes.

PubMed

Bharat, L Krishna; Jeon, Soo-Kun; Krishna, Kurugundla Gopi; Yu, Jae Su

2017-02-09

The commercially available white-light-emitting diodes (WLEDs) are made with a combination of blue LEDs and yellow phosphors. These types of WLEDs lack certain properties which make them meagerly applicable for general illumination and flat panel displays. The solution for such problem is to use near-ultraviolet (NUV) chips as an excitation source because of their high excitation efficiency and good spectral distribution. Therefore, there is an active search for new phosphor materials which can be effectively excited within the NUV wavelength range (350-420 nm). In this work, novel rare-earth free self-luminescent Ca 2 KZn 2 (VO 4 ) 3 phosphors were synthesized by a citrate assisted sol-gel method at low calcination temperatures. Optical properties, internal quantum efficiency and thermal stability as well as morphology and crystal structure of Ca 2 KZn 2 (VO 4 ) 3 phosphors for their application to NUV-based WLEDs were studied. The crystal structure and phase formation were confirmed with XRD patterns and Rietveld refinement. The optical properties of these phosphor materials which can change the NUV excitation into visible yellow-green emissions were studied. The synthesized phosphors were then coated onto the surface of a NUV chip along with a blue phosphor (LiCaPO 4 :Eu 2+ ) to get brighter WLEDs with a color rendering index of 94.8 and a correlated color temperature of 8549 K.

Efficient white-light-emitting diodes based on poly(N-vinylcarbazole) doped with blue fluorescent and orange phosphorescent materials

NASA Astrophysics Data System (ADS)

Shih, Ping-I.; Shu, Ching-Fong; Tung, Yung-Liang; Chi, Yun

2006-06-01

We have fabricated polymer white-light-emitting devices possessing a single emitting layer containing a hole-transporting host polymer, poly(N-vinylcarbazole), and an electron-transporting auxiliary, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole, doped with a blue-light-emitting amino-substituted distyrylarylene fluorescent dye and an orange-light-emitting osmium phosphor. The doubly doped device exhibited an intense white emission having Commission Internationale de l'Eclairage coordinates of (0.33, 0.34), a high external quantum efficiency of 6.12% (13.2cd/A), and a maximum brightness of 11306cd/m2. The color coordinates remained unchanged over a range of operating voltages, even at luminance as high as 1×104cd/m2.

Photoconversion in orange and red fluorescent proteins

PubMed Central

Kremers, Gert-Jan; Hazelwood, Kristin L.; Murphy, Christopher S.; Davidson, Michael W.; Piston, David W.

2009-01-01

We report that photoconversion is fairly common among orange and red fluorescent proteins, as a screen of 12 variants yielded 8 that exhibit photoconversion. Specifically, three red fluorescent proteins can be switched into a green state, and two orange variants can be photoconverted to the far red. The orange highlighters are ideal for dual-probe highlighter applications, and they exhibit the most red-shifted excitation of all fluorescent protein described to date. PMID:19363494

Full down-conversion of amber-emitting phosphor-converted light-emitting diodes with powder phosphors and a long-wave pass filter.

PubMed

Oh, Jeong Rok; Cho, Sang-Hwan; Park, Hoo Keun; Oh, Ji Hye; Lee, Yong-Hee; Do, Young Rag

2010-05-24

This paper reports the possibility of a facile optical structure to realize a highly efficient monochromatic amber-emitting light-emitting diode (LED) using a powder-based phosphor-converted LED combined with a long-wave pass filter (LWPF). The capping of a blue-reflecting and amber-passing LWPF enhances both the amber emission from the silicate amber phosphor layer and the color purity due to the blocking and recycling of the pumping blue light from the InGaN LED. The enhancement of the luminous efficacy of the amber pc-LED with a LWPF (phosphor concentration 20 wt%, 39.4 lm/W) is 34% over that of an amber pc-LED without a LWPF (phosphor concentration 55 wt%, 29.4 lm/W) at 100 mA and a high color purity (>96%) with Commission International d'Eclairage (CIE) color coordinates of x=0.57 and y=0.42.

Photoluminescence Properties of Red-Emitting Ca3Sr3-x(PO4)4:xEu3+ Phosphors for White Light-Emitting Diodes.

PubMed

Hakeem, D A; Park, K

2015-07-01

The photoluminescent properties of the Eu(3+)-activated Ca3Sr3(PO4)4 phosphors prepared by a solution combustion method were investigated. The excitation spectra of Ca3Sr3-x(PO4)4:xEu3+ (0.05 ≤ x ≤ 0.6) phosphors under 614 nm wavelength showed a broad band centered at 266 nm along with other peaks at 320, 362, 381, 394, 414, 464, and 534 nm. The emission spectra observed in the range of 450 to 750 nm under excitation at 394 nm were ascribed to the 5D0-7F1-4 transitions of Eu3+ ions. The Ca3Sr3-x(PO4)4:xEu3+ phosphors showed the strongest red emission at 614 nm due to the electric dipole 5DO -->7F2 transition of Eu3+. The strongest emission intensity was obtained for the Eu3+ ions of x = 0.5. The prepared Ca3Sr3-x(PO4)4:xEu3+ can be used as an efficient red phosphor for UV-based white LEDs.

Inheritance of flower color in periwinkle: orange-red corolla and white eye.

PubMed

Sreevalli, Y; Kulkarni, R N; Baskaran, K

2002-01-01

The commonly found flower colors in periwinkle (Catharanthus roseus)--pink, white, red-eyed, and pale pink center--are reported to be governed by the epistatic interaction between four genes--A, R, W, and I. The mode of inheritance of an uncommon flower color, orange-red corolla and white eye, was studied by crossing an accession possessing this corolla color with a white flowered variety (Nirmal). The phenotype of the F(1) plants and segregation data of F(2) and backcross generations suggested the involvement of two more interacting and independently inherited genes, one (proposed symbol E) determining the presence or absence of red eye and another (proposed symbol O) determining orange-red corolla.

Imaging camera system of OYGBR-phosphor-based white LED lighting

NASA Astrophysics Data System (ADS)

Kobashi, Katsuya; Taguchi, Tsunemasa

2005-03-01

The near-ultraviolet (nUV) white LED approach is analogous to three-color fluorescent lamp technology, which is based on the conversion of nUV radiation to visible light via the photoluminescence process in phosphor materials. The nUV light is not included in the white light generation from nUV-based white LED devices. This technology can thus provide a higher quality of white light than the blue and YAG method. A typical device demonstrates white luminescence with Tc=3,700 K, Ra > 93, K > 40 lm/W and chromaticity (x, y) = (0.39, 0.39), respectively. The orange, yellow, green and blue OYGB) or orange, yellow, red, green and blue (OYRGB) device shows a luminescence spectrum broader than of an RGB white LED and a better color rendering index. Such superior luminous characteristics could be useful for the application of several kinds of endoscope. We have shown the excellent pictures of digestive organs in a stomach of a dog due to the strong green component and high Ra.

Preparation and Luminescence Properties of Ca9NaZn(PO4)7:Dy3+ Single-Phase White Light-Emitting Phosphor

NASA Astrophysics Data System (ADS)

Zhu, Daoyun; Liao, Min; Mu, Zhongfei; Wu, Fugen

2018-05-01

Dy3+-doped Ca9NaZn(PO4)7 has been synthesized by high-temperature solid-state reaction. X-ray diffraction analysis revealed that the obtained phosphors existed as single phase. Doping with Dy3+ at low concentration had no obvious effect on the crystal structure of the host. Dy3+-doped samples showed strong emission at approximately 480 nm and 571 nm under excitation at 350 nm. The blue and yellow emissions showed almost the peak intensity. The combination of blue and yellow light formed white light. The color coordinates (0.323, 0.372) of the composite light are located in the white light region. The optimum doping concentration of Dy3+ ions was experimentally determined to be 10 mol.%. The concentration quenching mechanism was ascertained to be electric dipole-dipole interaction among Dy3+ ions. The obtained phosphors exhibited good thermal stability. These results indicate potential applications as single-phase white light-emitting phosphors.

Preparation and photoluminescence properties of red-emitting phosphor ZnAl2O4:Eu3+ with an intense 5D0 → 7F2 transition

NASA Astrophysics Data System (ADS)

He, Can; Ji, Haipeng; Huang, Zhaohui; Zhang, Xiaoguang; Liu, Haitao; Liu, Silin; Liu, Yangai; Fang, Minghao; Wu, Xiaowen; Min, Xin

2018-02-01

A series of ZnAl2-x O4:xEu3+ phosphors was synthesized by a modified co-precipitation method. The phase structure and photoluminescence properties were examined and extensively discussed. Composition-optimized ZnAl1.97O4:0.03Eu3+ exhibited sharp, intense red characteristic emissions with the Commission Internationale de l’Eclairage coordinates of (0.62, 0.33) peaking at 620 nm under an excitation at 394 nm, corresponding to the 5D0 → 7F2 transition of Eu3+. The quenching concentration of Eu3+ in ZnAl2-x O4:xEu3+ phosphors was approximately 0.03. In addition, the concentration quenching mechanism, fluorescence decay curves, and thermally stable luminescence properties of ZnAl2-x O4:xEu3+ phosphors were investigated. The results indicated that ZnAl2-x O4:xEu3+ phosphors demonstrate potential applications in near-ultraviolet light-emitting diode pumped white light lamps.

A Systematic Approach to Achieving High Performance Hybrid Lighting Phosphors with Excellent Thermal- and Photostability

DOE PAGES

Fang, Yang; Liu, Wei; Teat, Simon J.; ...

2016-12-07

We have designed and synthesized a family of high-performance inorganic-organic hybrid phosphor materials composed of extended and robust networks of one-, two- and three-dimensions. Following a bottom-up solution-based synthetic approach, these structures are constructed by connecting highly emissive Cu 4I 4 cubic clusters via carefully selected ligands that form strong Cu-N bonds. They emit intensive yellow-orange light with high luminescence quantum efficiency, coupled with large Stokes shift which greatly reduces self-absorption. They also demonstrate exceptionally high framework- and photo-stability, comparable to those of commercial phosphors. The high stabilities are the result of significantly enhanced Cu-N bonds, as confirmed by themore » DFT binding energy and electron density calculations. Possible emission mechanisms are analyzed based on the results of theoretical calculations and optical experiments. Two-component white phosphors obtained by blending blue and yellow emitters reach an internal quantum yield (IQY) as high as 82% and correlated color temperature (CCT) as low as 2534 K. The performance level of this sub-family exceeds all other types of Cu-I based hybrid systems. The combined advantages make them excellent candidates as alternative rare-earth element (REE) free phosphors for possible use in energy-efficient lighting devices.« less

Luminescent Enhancement of Na+ and Sm3+ Co-doping Reddish Orange SrCa3Si2O8 Phosphors

NASA Astrophysics Data System (ADS)

Chun, Fengjun; Zhang, Binbin; Li, Wen; Liu, Honggang; Deng, Wen; Chu, Xiang; Osman, Hanan; Zhang, Haitao; Yang, Weiqing

2018-04-01

Reddish orange SrCa3Si2O8 phosphors, prepared by the facile solid state reaction method, are a luminescent enhancement of Na+ and Sm3+ co-doping luminescent material. Na+ was designed to compensate the charge imbalance of Sm3+ ion substituting for the Sr2+ ion of orthorhombic SrCa3Si2O8 crystals. The results suggest that Na+ can effectively enhance the luminescent intensity of the reddish orange light peaked at about 562 nm (4 G 5/2 → 6 H 5/2), 600 nm (4 G 5/2 → 6 H 7/2) and 645 nm (4 G 5/2 → 6 H 9/2) excited by the near ultraviolet excited light 404 nm (4 L 13/2 → 6 H 5/2). The energy transfer has been further verified by the florescence lifetime. Additionally, the luminescent lifetime τ of as-grown phosphors was separated into two parts, a rapid lifetime and a slow lifetime. The average lifetime results ranged from 2.098 to 1.329 ms which were influenced by the concentration of Sm3+ doping. The systematic researches of as-grown phosphors have clearly suggested a potential application for white-light-emitting diodes ( w-LEDs).

Rare-earth free self-luminescent Ca2KZn2(VO4)3 phosphors for intense white light-emitting diodes

PubMed Central

Bharat, L. Krishna; Jeon, Soo-Kun; Krishna, Kurugundla Gopi; Yu, Jae Su

2017-01-01

The commercially available white-light-emitting diodes (WLEDs) are made with a combination of blue LEDs and yellow phosphors. These types of WLEDs lack certain properties which make them meagerly applicable for general illumination and flat panel displays. The solution for such problem is to use near-ultraviolet (NUV) chips as an excitation source because of their high excitation efficiency and good spectral distribution. Therefore, there is an active search for new phosphor materials which can be effectively excited within the NUV wavelength range (350–420 nm). In this work, novel rare-earth free self-luminescent Ca2KZn2(VO4)3 phosphors were synthesized by a citrate assisted sol-gel method at low calcination temperatures. Optical properties, internal quantum efficiency and thermal stability as well as morphology and crystal structure of Ca2KZn2(VO4)3 phosphors for their application to NUV-based WLEDs were studied. The crystal structure and phase formation were confirmed with XRD patterns and Rietveld refinement. The optical properties of these phosphor materials which can change the NUV excitation into visible yellow-green emissions were studied. The synthesized phosphors were then coated onto the surface of a NUV chip along with a blue phosphor (LiCaPO4:Eu2+) to get brighter WLEDs with a color rendering index of 94.8 and a correlated color temperature of 8549 K. PMID:28181549

Toward scatter-free phosphors in white phosphor-converted light-emitting diodes

PubMed Central

Park, Hoo Keun; Oh, Ji Hye; Rag Do, Young

2012-01-01

Scatter-free phosphors promise to suppress the scattering loss of conventional micro-size powder phosphors in white phosphor-converted light-emitting diodes (pc-LEDs). Large micro-size cube phosphors (~100 μm) are newly designed and prepared as scatter-free phosphors, combining the two scatter-free conditions of particles based on Mie’s scattering theory; the grain size or grain boundary was smaller than 50 nm and the particle size was larger than 30 μm. A careful evaluation of the conversion efficiency and packaging efficiency of the large micro-size cube phosphor-based white pc-LED demonstrated that large micro-size cube phosphors are an outstanding potential candidate for scatter-free phosphors in white pc-LEDs. The luminous efficacy and packaging efficiency of the Y3Al5O12:Ce3+ large micro-size cube phosphor-based pc-LEDs were 123.0 lm/W and 0.87 at 4300 K under 300 mA, which are 17% and 34% higher than those of commercial powder phosphor-based white LEDs (104.8 lm/W and 0.65), respectively. In addition, the introduction of large micro-size cube phosphors can reduce the wide variation in optical properties as a function of both the ambient temperature and applied current compared with those of conventional powder phosphor-based white LEDs. PMID:22535113

High color rendering index WLED based on YAG:Ce phosphor and CdS/ZnS core/shell quantum dots

NASA Astrophysics Data System (ADS)

Shen, Changyu; Li, Ke

2009-08-01

White LED combining of blue chip and YAG:Ce phosphor suffers from a red spectral deficiency, resulting in a relatively low value of color rendering index (CRI). In our study, for an effort to improve color rendering properties of YAG:Ce phosphor-based white LEDs, highly luminescent red-orange emitting CdS/ZnS QDs were blended with YAG:Ce phosphors. Core/shell CdS/ZnS quantum dots with the emission wavelength of 618nm, was synthesized by thermal deposition using cadmium oxide and selenium as precursors in a hot lauric acid and hexadecylamine trioctylphosphine oxide hybrid. YAG:Ce phosphor was synthesized by high-temperature solid state reaction at 900-1200°C in a slightly reducing atmosphere for 4 hours. Blends of phosphors and QDs exhibited the prominent spectral evolution with an increasing content of QDs. A hybrid white LED, which combines a blue LED with the blend of YAG phosphor and QDs with a weight ratio of 1.5:1,was demonstrated with an improved CRI value of 86.

Highly Regular, Uniform K3ScF6:Mn4+ Phosphors: Facile Synthesis, Microstructures, Photoluminescence Properties, and Application in Light-Emitting Diode Devices.

PubMed

Ming, Hong; Liu, Shuifu; Liu, Lili; Peng, Jiaqing; Fu, Junxiang; Du, Fu; Ye, Xinyu

2018-06-13

A new generation of red phosphors of complex fluoride matrices activated with Mn 4+ has gained a broad interest in getting high color quality and low color temperature of solid-state white light-emitting diodes (WLEDs). However, besides their instability toward moisture, the extremely irregular and nonuniform morphologies of these phosphors have limited their practical industry applications. In the present study, a novel type of K 3 ScF 6 :Mn 4+ red phosphor with highly regular, uniform, and high color purity was obtained successfully through a facile coprecipitation route under mild conditions. The crystal structure was identified with aids of the powder X-ray diffraction, Rietveld refinement, and density functional theory calculations. The prototype crystallizes in the space group Fm3 m with a cubic structure, and the lattice parameters are fitted well to be a = b = c = 8.4859(8) Å and V = 611.074(2) Å 3 . The Mn 4+ ions occupy Sc 3+ sites and locate at the centers of the distorted ScF 6 octahedrons. A wide band gap of approximately 6.15 eV can provide sufficient space to accommodate impurity energy levels. Unlike most other Mn 4+ ion-activated fluoride phosphors, the as-prepared K 3 ScF 6 :Mn 4+ phosphors demonstrate highly uniform and regular morphologies with shapes transforming from cube to octahedron with increasing Mn 4+ ion concentration. Under blue light excitation, the as-prepared K 3 ScF 6 :Mn 4+ sample exhibits intense sharp-line red fluorescence (the strongest peak located at 631 nm) with high color purity. An excellent recovery in luminescence upon heating and cooling processes implies high stability of K 3 ScF 6 :Mn 4+ . Furthermore, a warm WLED fabricated with blue GaN chips merged with the mixture of K 3 ScF 6 :Mn 4+ and the well-known commercial YAG:Ce 3+ yellow phosphors exhibits wonderful color quality with lower correlated color temperature (3250 K) and higher color-rendering index ( R a = 86.4). These results suggest that the K 3 ScF 6 :Mn

7 CFR 29.1044 - Orange Red (FR).

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 2 2010-01-01 2010-01-01 false Orange Red (FR). 29.1044 Section 29.1044 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Type 92) § 29.1044 Orange Red (FR). A yellowish red. [42 FR 21092, Apr. 25, 1977. Redesignated at 47 FR...

Discovery of a Red-Emitting Li3RbGe8O18:Mn4+ Phosphor in the Alkali-Germanate System: Structural Determination and Electronic Calculations.

PubMed

Singh, Satendra Pal; Kim, Minseuk; Park, Woon Bae; Lee, Jin-Woong; Sohn, Kee-Sun

2016-10-17

A solid-state combinatorial chemistry approach, which used the A-Ge-O (A = Li, K, Rb) system doped with a small amount of Mn 4+ as an activator, was adopted in a search for novel red-emitting phosphors. The A site may have been composed of either a single alkali metal ion or of a combination of them. This approach led to the discovery of a novel phosphor in the above system with the chemical formula Li 3 RbGe 8 O 18 :Mn 4+ . The crystal structure of this novel phosphor was solved via direct methods, and subsequent Rietveld refinement revealed a trigonal structure in the P3̅1m space group. The discovered phosphor is believed to be novel in the sense that neither the crystal structure nor the chemical formula matches any of the prototype structures available in the crystallographic information database (ICDD or ICSD). The measured photoluminescence intensity that peaked at a wavelength of 667 nm was found to be much higher than the best intensity obtained among all the existing A 2 Ge 4 O 9 (A = Li, K, Rb) compounds in the alkali-germanate system. An ab initio calculation based on density function theory (DFT) was conducted to verify the crystal structure model and compare the calculated value of the optical band gap with the experimental results. The optical band gap obtained from diffuse reflectance measurement (5.26 eV) and DFT calculation (4.64 eV) results were in very good agreement. The emission wavelength of this phosphor that exists in the deep red region of the electromagnetic spectrum may be very useful for increasing the color gamut of LED-based display devices such as ultrahigh-definition television (UHDTV) as per the ITU-R BT.2020-2 recommendations and also for down-converter phosphors that are used in solar-cell applications.

Amber light-emitting diode comprising a group III-nitride nanowire active region

DOEpatents

Wang, George T.; Li, Qiming; Wierer, Jr., Jonathan J.; Koleske, Daniel

2014-07-22

A temperature stable (color and efficiency) III-nitride based amber (585 nm) light-emitting diode is based on a novel hybrid nanowire-planar structure. The arrays of GaN nanowires enable radial InGaN/GaN quantum well LED structures with high indium content and high material quality. The high efficiency and temperature stable direct yellow and red phosphor-free emitters enable high efficiency white LEDs based on the RGYB color-mixing approach.

[A novel yellow organic light-emitting device].

PubMed

Ma, Chen; Wang, Hua; Hao, Yu-Ying; Gao, Zhi-Xiang; Zhou, He-Feng; Xu, Bing-She

2008-07-01

The fabrication of a novel organic yellow-light-emitting device using Rhodamine B as dopant with double quantum-well (DQW) structure was introduced in the present article. The structure and thickness of this device is ITO/CuPc (6 nm) /NPB (20 nm) /Alq3 (3 nm)/Alq3 : Rhodamine B (3 nm) /Alq3 (3 nm) /Al q3 : Rhodamine B(3 nm) /Alq3 (30 nm) /Liq (5 nm)/Al (30 nm). With the detailed investigation of electroluminescence of the novel organic yellow-light-emitting device, the authors found that the doping concentration of Rhodamine B (RhB) had a very big influence on luminance and efficiency of the organic yellow-light-emitting device. When doping concentration of Rhodamine B (RhB) was 1.5 wt%, the organic yellow-light-emitting device was obtained with the maximum current efficiency of 1.526 cd x A(-1) and the maximum luminance of 1 309 cd x m(-2). It can be seen from the EL spectra of the devices that there existed energy transferring from Alq3 to RhB in the organic light-emitting layers. When the doping concentration of RhB increased, lambda(max) of EL spectra redshifted obviously. The phenomenon was attributed to the Stokes effect of quantum wells and self-polarization of RhB dye molecules.

Optical properties of Dy3+ and Eu3+ -Codoped SrWO4 phosphors for white light-emitting diodes

NASA Astrophysics Data System (ADS)

Cho, Shinho

2018-01-01

Dy3+ - and Eu3+ -codoped SrWO4 phosphor powders were prepared using a solid-state reaction technique by changing the molar concentration of Eu3+ within the range of 0 to 15 mol% at a fixed Dy3+ concentration of 5 mol%. The effects of Dy3+ and Eu3+ doping on the structural, morphological, and optical properties of SrWO4:Dy3+, Eu3+ phosphors were investigated via Xray diffraction, scanning electron microscopy, and photoluminescence spectrophotometry, respectively. Irrespective of the concentrations of Dy3+ and Eu3+ ions, the crystal structures of all the phosphors were tetragonal, and the grains exhibited a tendency to agglomerate. The emission spectra of Sr0.925WO4:5 mol% Dy3+ contained an intense yellow band at 573 nm arising from the 4 F 9/2 → 6 H 13/2 electric dipole transition of Dy3+, as well as three weak emission lines. When the Eu3+ ions were incorporated into the SrWO4:Dy3+ phosphors, a strong red emission peak at 615 nm originating from the 5D0 → 7F2 transition of Eu3+ appeared in addition to the four emission bands centered at 481, 573, 662, and 750 nm, which result from the 4 f-4 f transitions of Dy3+. The emission intensity decreased as the Eu3+ concentration increased up to 15 mol% due to concentration quenching, which resulted from dipole-dipole interactions. The results suggest that the color emissions and intensities of SrWO4:Dy3+, Eu3+ phosphors can be tuned from yellow to white to red by varying the types of ions used and the ratio of Dy3+ to Eu3+ ions.

Red Anthocyanins and Yellow Carotenoids Form the Color of Orange-Flower Gentian (Gentiana lutea L. var. aurantiaca).

PubMed

Berman, Judit; Sheng, Yanmin; Gómez Gómez, Lourdes; Veiga, Tania; Ni, Xiuzhen; Farré, Gemma; Capell, Teresa; Guitián, Javier; Guitián, Pablo; Sandmann, Gerhard; Christou, Paul; Zhu, Changfu

2016-01-01

Flower color is an important characteristic that determines the commercial value of ornamental plants. Gentian flowers occur in a limited range of colors because this species is not widely cultivated as a cut flower. Gentiana lutea L. var. aurantiaca (abbr, aurantiaca) is characterized by its orange flowers, but the specific pigments responsible for this coloration are unknown. We therefore investigated the carotenoid and flavonoid composition of petals during flower development in the orange-flowered gentian variety of aurantiaca and the yellow-flowered variety of G. lutea L. var. lutea (abbr, lutea). We observed minor varietal differences in the concentration of carotenoids at the early and final stages, but only aurantiaca petals accumulated pelargonidin glycosides, whereas these compounds were not found in lutea petals. We cloned and sequenced the anthocyanin biosynthetic gene fragments from petals, and analyzed the expression of these genes in the petals of both varieties to determine the molecular mechanisms responsible for the differences in petal color. Comparisons of deduced amino acid sequences encoded by the isolated anthocyanin cDNA fragments indicated that chalcone synthase (CHS), chalcone isomerase (CHI), anthocyanidin synthase 1 (ANS1) and ANS2 are identical in both aurantiaca and lutea varieties whereas minor amino acid differences of the deduced flavonone 3-hydroxylase (F3H) and dihydroflavonol 4-reductase (DFR) between both varieties were observed. The aurantiaca petals expressed substantially higher levels of transcripts representing CHS, F3H, DFR, ANS and UDP-glucose:flavonoid-3-O-glucosyltransferase genes, compared to lutea petals. Pelargonidin glycoside synthesis in aurantiaca petals therefore appears to reflect the higher steady-state levels of pelargonidin synthesis transcripts. Moreover, possible changes in the substrate specificity of DFR enzymes may represent additional mechanisms for producing red pelargonidin glycosides in petals of

Red Anthocyanins and Yellow Carotenoids Form the Color of Orange-Flower Gentian (Gentiana lutea L. var. aurantiaca)

PubMed Central

Gómez Gómez, Lourdes; Veiga, Tania; Ni, Xiuzhen; Farré, Gemma; Capell, Teresa; Guitián, Javier; Guitián, Pablo; Sandmann, Gerhard; Christou, Paul

2016-01-01

Flower color is an important characteristic that determines the commercial value of ornamental plants. Gentian flowers occur in a limited range of colors because this species is not widely cultivated as a cut flower. Gentiana lutea L. var. aurantiaca (abbr, aurantiaca) is characterized by its orange flowers, but the specific pigments responsible for this coloration are unknown. We therefore investigated the carotenoid and flavonoid composition of petals during flower development in the orange-flowered gentian variety of aurantiaca and the yellow-flowered variety of G. lutea L. var. lutea (abbr, lutea). We observed minor varietal differences in the concentration of carotenoids at the early and final stages, but only aurantiaca petals accumulated pelargonidin glycosides, whereas these compounds were not found in lutea petals. We cloned and sequenced the anthocyanin biosynthetic gene fragments from petals, and analyzed the expression of these genes in the petals of both varieties to determine the molecular mechanisms responsible for the differences in petal color. Comparisons of deduced amino acid sequences encoded by the isolated anthocyanin cDNA fragments indicated that chalcone synthase (CHS), chalcone isomerase (CHI), anthocyanidin synthase 1 (ANS1) and ANS2 are identical in both aurantiaca and lutea varieties whereas minor amino acid differences of the deduced flavonone 3-hydroxylase (F3H) and dihydroflavonol 4-reductase (DFR) between both varieties were observed. The aurantiaca petals expressed substantially higher levels of transcripts representing CHS, F3H, DFR, ANS and UDP-glucose:flavonoid-3-O-glucosyltransferase genes, compared to lutea petals. Pelargonidin glycoside synthesis in aurantiaca petals therefore appears to reflect the higher steady-state levels of pelargonidin synthesis transcripts. Moreover, possible changes in the substrate specificity of DFR enzymes may represent additional mechanisms for producing red pelargonidin glycosides in petals of

LaAlO3:Mn4+ as Near-Infrared Emitting Persistent Luminescence Phosphor for Medical Imaging: A Charge Compensation Study

PubMed Central

De Clercq, Olivier Q.; Korthout, Katleen

2017-01-01

Mn4+-activated phosphors are emerging as a novel class of deep red/near-infrared emitting persistent luminescence materials for medical imaging as a promising alternative to Cr3+-doped nanomaterials. Currently, it remains a challenge to improve the afterglow and photoluminescence properties of these phosphors through a traditional high-temperature solid-state reaction method in air. Herein we propose a charge compensation strategy for enhancing the photoluminescence and afterglow performance of Mn4+-activated LaAlO3 phosphors. LaAlO3:Mn4+ (LAO:Mn4+) was synthesized by high-temperature solid-state reaction in air. The charge compensation strategies for LaAlO3:Mn4+ phosphors were systematically discussed. Interestingly, Cl−/Na+/Ca2+/Sr2+/Ba2+/Ge4+ co-dopants were all found to be beneficial for enhancing LaAlO3:Mn4+ luminescence and afterglow intensity. This strategy shows great promise and opens up new avenues for the exploration of more promising near-infrared emitting long persistent phosphors for medical imaging. PMID:29231901

Sol-gel synthesis and luminescent properties of red-emitting Y(P,V)O4:Eu(3+) phosphors.

PubMed

Zhang, Xinguo; Zhou, Fangxiang; He, Pei; Zhang, Min; Gong, Menglian

2016-02-01

Eu(3+)-activated Y(P,V)O4 phosphors were prepared by the EDTA sol-gel method, and the corresponding morphologies and luminescent properties were investigated. The sample particles were relatively spheroid with size of 2-3 µm and had a smooth surface. The excitation spectra for Y(P,V)O4:Eu(3+) consisted of three strong excitation bands in the 200-350 nm range, which were attributed to a Eu(3+)- O(2-) charge-transfer band and (1)A1-(1) T1/(1) T2 transitions in VO4(3-). The as-synthesized phosphors exhibited a highly efficient red luminescence at 613 nm due to the Eu(3+5) D0-(7) F2 electric dipole transition. With the increase in the V(5+)/P(5+) ratio, the luminescence intensity of the red phosphor under UV excitation was greatly improved due to enhanced VO4(3-) → Eu(3+) energy transfer. Copyright © 2015 John Wiley & Sons, Ltd.

Electroplex as a New Concept of Universal Host for Improved Efficiency and Lifetime in Red, Yellow, Green, and Blue Phosphorescent Organic Light‐Emitting Diodes

PubMed Central

Song, Wook; Cho, Yong Joo; Yu, Hyeonghwa; Aziz, Hany; Lee, Kang Mun

2017-01-01

Abstract A new concept of host, electroplex host, is developed for high efficiency and long lifetime phosphorescent organic light‐emitting diodes by mixing two host materials generating an electroplex under an electric field. A carbazole‐type host and a triazine‐type host are selected as the host materials to form the electroplex host. The electroplex host is found to induce light emission through an energy transfer process rather than charge trapping, and universally improves the lifetime of red, yellow, green, and blue phosphorescent organic light‐emitting diodes by more than four times. Furthermore, the electroplex host shows much longer lifetime than a common exciplex host. This is the first demonstration of using the electroplex as the host of high efficiency and long lifetime phosphorescent organic light‐emitting diodes. PMID:29610726

The Radiative Decay of Green and Red Photoluminescent Phosphors: An Undergraduate Kinetics Experiment for Materials Chemistry

ERIC Educational Resources Information Center

Esposti, C. Degli; Bizzocchi, L.

2008-01-01

This article describes a laboratory experiment that allows the students to investigate the radiative properties of the green and red emitting phosphors that are employed in commercial fluorescent lamps. Making use of a spectrofluorometer, students first record the emission spectrum of a fluorescent lamp under normal operating conditions, and then…

Recombination zone in white organic light emitting diodes with blue and orange emitting layers

NASA Astrophysics Data System (ADS)

Tsuboi, Taiju; Kishimoto, Tadashi; Wako, Kazuhiro; Matsuda, Kuniharu; Iguchi, Hirofumi

2012-10-01

White fluorescent OLED devices with a 10 nm thick blue-emitting layer and a 31 nm thick orange-emitting layer have been fabricated, where the blue-emitting layer is stacked on a hole transport layer. An interlayer was inserted between the two emitting layers. The thickness of the interlayer was changed among 0.3, 0.4, and 1.0 nm. White emission with CIE coordinates close to (0.33, 0.33) was observed from all the OLEDs. OLED with 0.3 nm thick interlayer gives the highest maximum luminous efficiency (11 cd/A), power efficiency (9 lm/W), and external quantum efficiency (5.02%). The external quantum efficiency becomes low with increasing the interlayer thickness from 0 nm to 1.0 nm. When the location of the blue- and orange-emitting layers is reversed, white emission was not obtained because of too weak blue emission. It is suggested that the electron-hole recombination zone decreases nearly exponentially with a distance from the hole transport layer.

Highly Stable K2SiF6:Mn4+@K2SiF6 Composite Phosphor with Narrow Red Emission for White LEDs.

PubMed

Huang, Lin; Liu, Yong; Yu, Jinbo; Zhu, Yiwen; Pan, Fengjuan; Xuan, Tongtong; Brik, Mikhail G; Wang, Chengxin; Wang, Jing

2018-05-30

Poor water resistance and nongreen synthesis remain great challenges for commercial narrow red-emitting phosphor A 2 MF 6 :Mn 4+ (A = alkali metal ion; M = Si, Ge, Ti) for solid-state lighting and display. We develop here a simple and green growth route to synthesize homogeneous red-emitting composite phosphor K 2 SiF 6 :Mn 4+ @K 2 SiF 6 (KSFM@KSF) with excellent water resistance and high efficiency without the usage of toxic and volatile hydrogen fluoride solution. After immersing into water for 6 h, the as-obtained water-resistant products maintain 76% of the original emission intensity, whereas the emission intensity of non-water-resistant ones steeply drops down to 11%. A remarkable result is that after having kept at 85% humidity and at 85 °C for 504 h (21 days), the emission intensity of the as-obtained water-resistant products is at 80-90%, from its initial value, which is 2-3 times higher than 30-40% for the non-water-resistant products. The surface deactivation-enabled growth mechanism for these phosphors was proposed and investigated in detail. We found that nontoxic H 3 PO 4 /H 2 O 2 aqueous solution promotes the releasing and decomposition of the surface [MnF 6 ] 2- ions and the transformation of the KSFM surface to KSF, which finally contributes to the homogeneous KSFM@KSF composite structure. This composite structure strategy was also successfully used to treat KSFM phosphor prepared by other methods. We believe that the results obtained in the present paper will open the pathway for the large-scale environmentally friendly synthesis of the excellent antimoisture narrow red-emitting A 2 MF 6 :Mn 4+ phosphor to be used for white light-emitting diode applications.

Top-emitting white organic light-emitting devices with down-conversion phosphors: theory and experiment.

PubMed

Ji, Wenyu; Zhang, Letian; Gao, Ruixue; Zhang, Liming; Xie, Wenfa; Zhang, Hanzhuang; Li, Bin

2008-09-29

White top-emitting organic light-emitting devices (TEOLEDs) with down-conversion phosphors are investigated from theory and experiment. The theoretical simulation was described by combining the microcavity model with the down-conversion model. A White TEOLED by the combination of a blue TEOLED with organic down-conversion phosphor 3-(4-(diphenylamino)phenyl)-1-pheny1prop-2-en-1-one was fabricated to validate the simulated results. It is shown that this approach permits the generation of white light in TEOLEDs. The efficiency of the white TEOLED is twice over the corresponding blue TEOLED. The feasible methods to improve the performance of such white TEOLEDs are discussed.

Hybrid 2D photonic crystal-assisted Lu3Al5O12:Ce ceramic-plate phosphor and free-standing red film phosphor for white LEDs with high color-rendering index.

PubMed

Park, Hoo Keun; Oh, Ji Hye; Kang, Heejoon; Zhang, Jian; Do, Young Rag

2015-03-04

This paper reports the combined optical effects of a two-dimensional (2D) SiNx photonic crystal layer (PCL)-assisted Lu3Al5O12:Ce (LuAG:Ce) green ceramic-plate phosphor (CPP) and a free-standing (Sr,Ca)AlSiN3:Eu red film phosphor to enhance luminous efficacy, color rendering index (CRI), and special CRI (R9) of LuAG:Ce CPP-capped white light-emitting diodes (LEDs) for high-power white LEDs at 350 mA. By introducing the 2D SiNx PCL, the luminous efficacy was improved by a factor of 1.25 and 1.15 compared to that of the conventional flat CPP-capped LED and the thickness-increased CPP-capped LED (with a thickness of 0.15 mm), respectively, while maintaining low color-rendering properties. The combining of the free-standing red film phosphor in the flat CPP-capped, the 2D PCL-assisted CPP-capped, and the thickness-increased CPP-capped LEDs led to enhancement of the CRI and the special CRI (R9); it also led to a decrease of the correlated color temperature (CCT) due to broad wavelength coverage via the addition of red emission. High CRI (94), natural white CCT (4450 K), and acceptable luminous efficacy (71.1 lm/W) were attained from the 2D PCL-assisted LuAG:Ce CPP/free-standing red film phosphor-based LED using a red phosphor concentration of 7.5 wt %. It is expected that the combination of the 2D PCL and the free-standing red film phosphor will be a good candidate for achieving a high-power white CPP-capped LED with excellent CRI.

Synthesis and Photoluminescence Properties of Ca2Ga2SiO7:Eu(3+) Red Phosphors with an Intense (5)D0 → (7)F4 Transition.

PubMed

Behrh, Gaganpreet Kaur; Gautier, Romain; Latouche, Camille; Jobic, Stéphane; Serier-Brault, Hélène

2016-09-19

Novel melilite-type Ca2Ga2SiO7:Eu(3+) red-emitting phosphors with different Eu(3+) contents were synthesized via high-temperature solid-state reaction. The crystal structure, optical absorption, and photoluminescence properties were investigated, while density functional theory calculations were performed on the host lattice. The excitation spectra indicate that phosphors can be effectively excited by near-UV light for a potential application in white-light-emitting diodes. Because of the abnormally high intensity emission at about 700 nm arising from the (5)D0 → (7)F4 transition of Eu(3+), the phosphors Ca2Ga2SiO7:Eu(3+) show a deep-red emission with chromaticity coordinates (0.639, 0.358).

Novel tunable green-red-emitting oxynitride phosphors co-activated with Ce3+, Tb3+, and Eu3+: photoluminescence and energy transfer.

PubMed

Huo, Jiansheng; Dong, Langping; Lü, Wei; Shao, Baiqi; You, Hongpeng

2017-07-14

A series of novel Ce 3+ , Tb 3+ and Eu 3+ ion doped Y 4 SiAlO 8 N-based oxynitride phosphors were synthesized by the solid-state method and characterized by X-ray powder diffraction, scanning electron microscopy, photoluminescence, lifetimes and thermo-luminescence. The excitation of the Ce 3+ /Tb 3+ co-doped and Ce 3+ /Tb 3+ /Eu 3+ tri-doped phosphor with near-UV radiation results in strong linear Tb 3+ green and Eu 3+ red emission. The occurrence of Ce 3+ -Tb 3+ and Ce 3+ -Tb 3+ -Eu 3+ energy transfer processes is responsible for the bright green or red luminescence. The Tb 3+ ion acting as an energy transfer bridge can alleviate MMCT quenching between the Ce 3+ -Eu 3+ ion pairs. The lifetime measurements demonstrated that the energy-transfer mechanisms of Ce 3+ → Tb 3+ and Tb 3+ → Eu 3+ are dipole-quadrupole and quadrupole-quadrupole interactions, respectively. The temperature dependent luminescence measurements showed that as-prepared green/red phosphors have good thermal stability against temperature quenching. The obtained results indicate that these phosphors might serve as promising candidates for n-UV LEDs.

Bluish-green color emitting Ba2Si3O8:Eu2+ ceramic phosphors for white light-emitting diodes.

PubMed

Xiao, F; Xue, Y N; Zhang, Q Y

2009-10-15

This paper reports on the structural and optical properties of Eu(2+) activated Ba(2)Si(3)O(8) ceramic phosphors synthesized by a sol-gel method. The ceramic phosphors have been characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and fluorescence measurements. The structural characterization results suggest that the as-prepared phosphors are of single phase monoclinic Ba(2)Si(3)O(8) with rod-like morphology. A broad excitation band ranging from 300 to 410 nm matches well with the ultraviolet (UV) radiation of light-emitting diodes (LEDs). Upon 380 nm UV light excitation, these phosphors emit bluish-green emission centered at 500 nm with color coordination (x=0.25, y=0.40). All the obtained results indicate that the Ba(2)Si(3)O(8):Eu(2+) ceramic phosphors are promising bluish-green candidates for the phosphor-converted white LEDs.

Double perovskite Ca2GdNbO6:Mn4+ deep red phosphor: Potential application for warm W-LEDs

NASA Astrophysics Data System (ADS)

Lu, Zuizhi; Huang, Tianjiao; Deng, Ruopeng; Wang, Huan; Wen, Lingling; Huang, Meixin; Zhou, Liya; Yao, Chunying

2018-05-01

A novel Mn4+-doped Ca2GdNbO6 (CGN) phosphor was prepared by high-temperature solid-state reaction. The crystal structure was investigated by X-ray diffraction patterns and unit cell structure. Mn4+ replaced the location of Nb5+ in the CGN lattice, and the value of energy gap (Egap) decreased from 2.16 eV to 1.13 eV, indicating that Mn4+ ions play a great influence on the absorption of CGN hosts. The broad excitation band from 250 nm to 550 nm matches well with commercial near-UV light emitting diodes, and the emission peak centered at 680 nm is due to 2E→4A2g transition in Mn4+ ions. The CIE chromaticity coordinates (0.698, 0.303) of CGN:Mn4+ phosphor was close to standard red color coordinates (0.666, 0.333). These investigations demonstrate CGN:Mn4+ phosphor as an efficient red phosphor for potential applications.

Crystal structure and Temperature-Dependent Luminescence Characteristics of KMg4(PO4)3:Eu2+ phosphor for White Light-emitting diodes

PubMed Central

Chen, Jian; Liu, Yangai; Mei, Lefu; Liu, Haikun; Fang, Minghao; Huang, Zhaohui

2015-01-01

The KMg4(PO4)3:Eu2+ phosphor was prepared by the conventional high temperature solid-state reaction. The crystal structure, luminescence and reflectance spectra, thermal stability, quantum efficiency and the application for N-UV LED were studied respectively. The phase formation and crystal structure of KMg4(PO4)3:Eu2+ were confirmed from the powder X-ray diffraction and the Rietveld refinement. The concentration quenching of Eu2+ in the KMg4(PO4)3 host was determined to be 1mol% and the quenching mechanism was certified to be the dipole–dipole interaction. The energy transfer critical distance of as-prepared phosphor was calculated to be about 35.84Å. Furthermore, the phosphor exhibited good thermal stability and the corresponding activation energy ΔE was reckoned to be 0.24eV. Upon excitation at 365nm, the internal quantum efficiency of the optimized KMg4(PO4)3:Eu2+ was estimated to be 50.44%. The white N-UV LEDs was fabricated via KMg4(PO4)3:Eu2+, green-emitting (Ba,Sr)2SiO4:Eu2+, and red-emitting CaAlSiN3:Eu2+ phosphors with a near-UV chip. The excellent color rendering index (Ra = 96) at a correlated color temperature (5227.08K) with CIE coordinates of x = 0.34, y = 0.35 of the WLED device indicates that KMg4(PO4)3:Eu2+ is a promising blue-emitting phosphor for white N-UV light emitting diodes (LEDs). PMID:25855866

Crystal structure and temperature-dependent luminescence characteristics of KMg4(PO4)3:Eu(2+) phosphor for white light-emitting diodes.

PubMed

Chen, Jian; Liu, Yangai; Mei, Lefu; Liu, Haikun; Fang, Minghao; Huang, Zhaohui

2015-04-09

The KMg4(PO4)3:Eu(2+) phosphor was prepared by the conventional high temperature solid-state reaction. The crystal structure, luminescence and reflectance spectra, thermal stability, quantum efficiency and the application for N-UV LED were studied respectively. The phase formation and crystal structure of KMg4(PO4)3:Eu(2+) were confirmed from the powder X-ray diffraction and the Rietveld refinement. The concentration quenching of Eu(2+) in the KMg4(PO4)3 host was determined to be 1 mol% and the quenching mechanism was certified to be the dipole-dipole interaction. The energy transfer critical distance of as-prepared phosphor was calculated to be about 35.84 Å. Furthermore, the phosphor exhibited good thermal stability and the corresponding activation energy ΔE was reckoned to be 0.24 eV. Upon excitation at 365 nm, the internal quantum efficiency of the optimized KMg4(PO4)3:Eu(2+) was estimated to be 50.44%. The white N-UV LEDs was fabricated via KMg4(PO4)3:Eu(2+), green-emitting (Ba,Sr)2SiO4:Eu(2+), and red-emitting CaAlSiN3:Eu(2+) phosphors with a near-UV chip. The excellent color rendering index (Ra = 96) at a correlated color temperature (5227.08 K) with CIE coordinates of x = 0.34, y = 0.35 of the WLED device indicates that KMg4(PO4)3:Eu(2+) is a promising blue-emitting phosphor for white N-UV light emitting diodes (LEDs).

Red-fleshed sweet orange juice improves the risk factors for metabolic syndrome.

PubMed

Silveira, Jacqueline Q; Dourado, Grace K Z S; Cesar, Thais B

2015-01-01

Orange juice consumption can promote lower levels of oxidative stress and inflammation due to the antioxidant activity of citrus flavonoids and carotenoids. In addition, red-fleshed sweet orange juice (red orange juice) also contains lycopene. This study investigated the effects of red orange juice consumption on risk factors for metabolic syndrome. Volunteers consumed red orange juice daily for 8 weeks, with clinical and biochemical assessments performed at baseline and on the final day. There was no change in the abdominal obesity, but low-density lipoprotein cholesterol, C-reactive protein decreased, while there was an increase of the antioxidant activity in serum after red orange juice consumption. Insulin resistance and systolic blood pressure were reduced in normal-weight volunteers, while diastolic blood pressure decreased in overweight volunteers after intervention. Red orange juice showed anti-inflammatory, antioxidant, and lipid-lowering properties that may prevent the development of metabolic syndrome.

Synthesis, energy transfer and luminescence properties of Ca{sub 2}MgWO{sub 6}:Sm{sup 3+}, Bi{sup 3+} phosphor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Renping, E-mail: jxcrp@163.com; Xu, Haidong; Luo, Wenjie

Graphical abstract: PL spectra of Ca{sub 2}MgWO{sub 6}:Sm{sup 3+} and Ca{sub 2}MgWO{sub 6}:Sm{sup 3+}, Bi{sup 3+} phosphors with excitation at 407 nm, and the corresponding CIE chromaticity diagram and chromaticity coordinates. - Highlights: • Novel Ca{sub 2}MgWO{sub 6}:Sm{sup 3+}, Bi{sup 3+} phosphor is synthesized by solid-state reaction method in air. • Emission intensity of Ca{sub 2}MgWO{sub 6}:Sm{sup 3+} phosphor is enhanced ∼2 times after co-doped Bi{sup 3+} ion. • Charge compensation and energy transfer may be explained via luminescence properties. • Luminous mechanism is analyzed by energy level diagrams of WO{sub 6}{sup 6−} group, Sm{sup 3+} and Bi{sup 3+} ions.more » - Abstract: Novel Ca{sub 2}MgWO{sub 6}:Sm{sup 3+}, Bi{sup 3+} phosphor is synthesized by solid-state reaction method in air. Host Ca{sub 2}MgWO{sub 6} with excitation 300 nm emits blue light. Ca{sub 2}MgWO{sub 6}:Bi{sup 3+} phosphor with excitation 300 and 338 nm emits yellow light. Ca{sub 2}MgWO{sub 6}:Sm{sup 3+} phosphor with excitation 300 nm exhibits tunable emission from blue to red light by increasing Sm{sup 3+} doping concentration from 0 to 8 mol%, however, only emits red light with excitation 407 nm. Ca{sub 2}MgWO{sub 6}:Sm{sup 3+}, Bi{sup 3+} phosphor with excitation 300 and 338 nm emits red light. The optimal Sm{sup 3+} doping concentration is ∼5 mol% in Ca{sub 2}MgWO{sub 6}:Sm{sup 3+} phosphor. After Bi{sup 3+} ion is co-doped, luminescence properties of Ca{sub 2}MgWO{sub 6}:Sm{sup 3+} phosphor can be improved obviously because of Bi{sub 2}O{sub 3} as fluxing agent role and energy transfer from Bi{sup 3+} to Sm{sup 3+} ions. The possible luminous mechanism of Ca{sub 2}MgWO{sub 6}:Sm{sup 3+}, Bi{sup 3+} phosphor is analyzed and explained by simplified energy level diagrams of WO{sub 6}{sup 6−} group, Bi{sup 3+} and Sm{sup 3+} ions.« less

AZO/Ag/AZO anode for resonant cavity red, blue, and yellow organic light emitting diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gentle, A. R., E-mail: angus.gentle@uts.edu.au; Smith, G. B.; Yambem, S. D.

Indium tin oxide (ITO) is the transparent electrode of choice for organic light-emitting diodes (OLEDs). Replacing ITO for cost and performance reasons is a major drive across optoelectronics. In this work, we show that changing the transparent electrode on red, blue, and yellow OLEDs from ITO to a multilayer buffered aluminium zinc oxide/silver/aluminium zinc oxide (AZO/Ag/AZO) substantially enhances total output intensity, with better control of colour, its constancy, and intensity over the full exit hemisphere. The thin Ag containing layer induces a resonant cavity optical response of the complete device. This is tuned to the emission spectra of the emissivemore » material while minimizing internally trapped light. A complete set of spectral intensity data is presented across the full exit hemisphere for each electrode type and each OLED colour. Emission zone modelling of output spectra at a wide range of exit angles to the normal was in excellent agreement with the experimental data and hence could, in principle, be used to check and adjust production settings. These multilayer transparent electrodes show significant potential for both eliminating indium from OLEDs and spectrally shaping the emission.« less

Synthesis and Luminescence Properties of Novel Ce(3+)- and Eu(2+)-Doped Lanthanum Bromothiosilicate La3Br(SiS4)2 Phosphors for White LEDs.

PubMed

Lee, Szu-Ping; Liu, Shuang-De; Chan, Ting-Shan; Chen, Teng-Ming

2016-04-13

Novel Ce(3+)- and Eu(2+)-doped lanthanum bromothiosilicate La3Br(SiS4)2:Ce(3+)and La3Br(SiS4)2:Eu(2+) phosphors were prepared by solid-state reaction in an evacuated and sealed quartz glass ampule. The La3Br(SiS4)2:Ce(3+) phosphor generates a cyan emission upon excitation at 375 nm, whereas the La3Br(SiS4)2:Eu(2+) phosphor could be excited with extremely broad range from UV to blue region (300 to 600 nm) and generates a reddish-orange broadband emission centered at 640 nm. In addition, thermal luminescence properties of La3Br(SiS4)2:Ce(3+)and La3Br(SiS4)2:Eu(2+) phosphors from 20 to 200 °C were investigated. The combination of a 450 nm blue InGaN-based LED chip with the red-emitting La3Br(SiS4)2:Eu(2+) phosphor, and green-emitting BOSE:Eu(2+) commercial phosphor produced a warm-white light with the CRI value of ∼95 and the CCT of 5,120 K. Overall, these results show that the prepared phosphors may have potential applications in pc-WLED.

Down-conversion phosphors as noble-metal-free co-catalyst in ZnO for efficient visible light photocatalysis

NASA Astrophysics Data System (ADS)

Chu, Haipeng; Liu, Xinjuan; Liu, Jiaqing; Lei, Wenyan; Li, Jinliang; Wu, Tianyang; Li, Ping; Li, Huili; Pan, Likun

2017-01-01

Exploring novel visible light responsive photocatalysts is one of greatly significant issues from the viewpoint of using solar energy. Here we report the yellow-orange emitting α-Si3N4-doped Lu3Al5O12:Ce3+ (Lu3Al5-xSixO12-xNx:Ce3+) phosphors as a noble-metal-free co-catalyst for enhanced visible light photocatalytic activity of ZnO. The results show that ZnO-Lu3Al5-xSixO12-xNx:Ce3+ hybrid photocatalysts using a fast microwave-assisted approach exhibits a 91% methylene blue (MB) degradation under visible light irradiation at 240 min, which evidence the synergistic effect of ZnO and Lu3Al5-xSixO12-xNx:Ce3+ that suppress the rate of charge recombination and increase the self-sensitized degradation of MB. ZnO-down conversion phosphors can be envisaged as potential candidate in environmental engineering and solar energy applications.

Enhance luminescence by introducing alkali metal ions (R+ = Li+, Na+ and K+) in SrAl2O4:Eu3+ phosphor by solid-state reaction method

NASA Astrophysics Data System (ADS)

Prasad Sahu, Ishwar

2016-05-01

In the present article, the role of charge compensator ions (R+ = Li+, Na+ and K+) in europium-doped strontium aluminate (SrAl2O4:Eu3+) phosphors was synthesized by the high-temperature, solid-state reaction method. The crystal structures of sintered phosphors were in a monoclinic phase with space group P21. The trap parameters which are mainly activation energy (E), frequency factor (s) and order of the kinetics (b) were evaluated by using the peak shape method. The calculated trap depths are in the range from 0.76 to 0.84 eV. Photoluminescence measurements showed that the phosphor exhibited emission peak with good intensity at 595 nm, corresponding to 5D0-7F1 (514 nm) orange emission and weak 5D0-7F2 (614 nm) red emission. The excitation spectra monitored at 595 nm show a broad band from 220 to 320 nm ascribed to O-Eu charge-transfer state transition and the other peaks in the range of 350-500 nm originated from f-f transitions of Eu3+ ions. The strongest band at 394 nm can be assigned to 7F0-5L6 transition of Eu3+ ions due to the typical f-f transitions within Eu3+ of 4f6 configuration. The latter lies in near ultraviolet (350-500 nm) emission of UV LED. CIE color chromaticity diagram and thermoluminescence spectra confirm that the synthesized phosphors would emit an orange-red color. Incorporating R+ = Li+, Na+ and K+ as the compensator charge, the emission intensity of SrAl2O4:Eu3+ phosphor can be obviously enhanced and the emission intensity of SrAl2O4:Eu3+ doping Li+ is higher than that of Na+ or K+ ions.

Synthesis of Green-Emitting (La,Gd)OBr:Tb3+ Phosphors

PubMed Central

Kim, Sun Woog; Jyoko, Kazuya; Masui, Toshiyuki; Imanaka, Nobuhito

2010-01-01

Green-emitting phosphors based on lanthanum-gadolinium oxybromide were synthesized in a single phase form by the conventional solid state reaction method, and photoluminescence properties of them were characterized. The excitation peak wavelength of (La1-xGdx)OBr:Tb3+ shifted to the shorter wavelength side with the increase in the crystal field around the Tb3+ ions by doping Gd3+ ions into the La3+ site, and, as a result, the green emission intensity was successfully enhanced. The maximum emission intensity was obtained for (La0.95Gd0.05)OBr:5%Tb3+, where the relative emission intensity was 45% of that of a commercial green-emitting LaPO4:Ce3+,Tb3+ phosphor.

Lighting theory and luminous characteristics of white light-emitting diodes

NASA Astrophysics Data System (ADS)

Uchida, Yuji; Taguchi, Tsunemasa

2005-12-01

A near-ultraviolet (UV)-based white light-emitting diode (LED) lighting system linked with a semiconductor InGaN LED and compound phosphors for general lighting applications is proposed. We have developed for the first time a novel type of high-color rendering index (Ra) white LED light source, which is composed of near-UV LED and multiphosphor materials showing orange (O), yellow (Y), green (G), and blue (B) emissions. The white LED shows the superior characteristics of luminous efficacy and high Ra to be about 40 lm/W and 93, respectively. Luminous and chromaticity characteristics, and their spectral distribution of the present white LED can be evaluated using the multipoint LED light source theory. It is revealed that the OYGB white LED can provide better irradiance properties than that of conventional white LEDs. Near-UV white LED technologies, in conjunction with phosphor blends, can offer superior color uniformity, high Ra, and excellent light quality. Consequently we are carrying out a "white LEDs for medical applications" program in the second phase of this national project from 2004 to 2009.

Flesh color inheritance and gene interactions among canary yellow, pale yellow and red watermelon

USDA-ARS?s Scientific Manuscript database

Two loci, C and i-C were previously reported to determine flesh color between canary yellow and red watermelon. Recently LCYB was found as a color determinant gene for canary yellow (C) and co-dominant CAPS marker was developed to identify canary yellow and red alleles. Another report suggested th...

White- and blue-light-emitting dysprosium(III) and terbium(III)-doped gadolinium titanate phosphors.

PubMed

Antić, Ž; Kuzman, S; Đorđević, V; Dramićanin, M D; Thundat, T

2017-06-01

Here we report the synthesis and structural, morphological, and photoluminescence analysis of white- and blue-light-emitting Dy 3 + - and Tm 3 + -doped Gd 2 Ti 2 O 7 nanophosphors. Single-phase cubic Gd 2 Ti 2 O 7 nanopowders consist of compact, dense aggregates of nanoparticles with an average size of ~25 nm for Dy 3 + -doped and ~50 nm for Tm 3 + -doped samples. The photoluminescence results indicated that ultraviolet (UV) light excitation of the Dy 3 + -doped sample resulted in direct generation of white light, while a dominant yellow emission was obtained under blue-light excitation. Intense blue light was obtained for Tm 3 + -doped Gd 2 Ti 2 O 7 under UV excitation suggesting that this material could be used as a blue phosphor. Copyright © 2016 John Wiley & Sons, Ltd.

Preparation and Characterization of UV Emitting Fluoride Phosphors for Phototherapy Lamps

NASA Astrophysics Data System (ADS)

Belsare, P. D.; Moharil, S. V.; Joshi, C. P.; Omanwar, S. K.

2011-10-01

The use of ultraviolet radiation for the treatment of various skin diseases is well known for long time. Phototherapy employs ultraviolet-blue radiation to cure skin diseases. The basis of phototherapy is believed to be the direct interaction of light of certain frequencies with tissue to cause a change in immune response. Currently dermatologists use UV lamps having specific emissions in UV region for treating various skin diseases. The treatment of skin diseases using artificial sources of UV radiation is now well established and more than 50 types of skin diseases are treated by phototherapy. This is an effective treatment for many skin disorders, such as psoriasis, vitiligo, ofujis disease, morphea , scleroderma, cutaneous T-cell lymphoma, lupus erythematosus, hyperbilirubinemia commonly known as infant jaundice, acne vulgaris, This paper reports photoluminescence properties of UV emitting fluoride phosphors prepared by wet chemical method. Emission characteristics of these phosphors are found similar to those of commercial UV lamp phosphors with comparable intensities. The usefulness of UV emitting fluoride phosphor is discussed in the paper.

Laser discrimination by stimulated emission of a phosphor

NASA Technical Reports Server (NTRS)

Mathur, V. K.; Chakrabarti, K.

1991-01-01

A method for discriminating sources of UV, near infrared, and far infrared laser radiation was discovered. This technology is based on the use of a single magnesium sulfide phosphor doubly doped with rare earth ions, which is thermally/optically stimulated to generate colors correlatable to the incident laser radiation. The phosphor, after initial charging by visible light, exhibits green stimulated luminescence when exposed to a near infrared source (Nd: YAG laser). On exposure to far infrared sources (CO2 laser) the phosphor emission changes to orange color. A UV laser produces both an orange red as well as green color. A device using this phosphor is useful for detecting the laser and for discriminating between the near infrared, far infrared, and UV lasers. The technology is also capable of infrared laser diode beam profiling since the radiation source leaves an imprint on the phosphor that can be photographed. Continued development of the technology offers potential for discrimination between even smaller bandwidths within the infrared spectrum, a possible aid to communication or wavemixing devices that need to rapidly identify and process optical signals.

Multichannel Luminescence Properties of Mixed-Valent Eu2+/Eu3+ Coactivated SrAl3BO7 Nanocrystalline Phosphors for Near-UV LEDs.

PubMed

Liu, Xiaoming; Xie, Weijie; Lü, Ying; Feng, Jingchun; Tang, Xinghua; Lin, Jun; Dai, Yuhua; Xie, Yu; Yan, Liushui

2017-11-20

Up to now, orchestrating the coexistence of Eu 2+ and Eu 3+ activators in a single host lattice has been an extremely difficult task, especially for the appearance of the characteristic emission of Eu 2+ and Eu 3+ in order to generate white light. Nevertheless, here we demonstrate a new Eu 2+ /Eu 3+ coactivated SrAl 3 BO 7 nanocrystalline phosphor with abundant and excellent multichannel luminescence properties. A series of Eu 2+ /Eu 3+ coactivated SrAl 3 BO 7 nanocrystalline phosphors were prepared through a Pechini-type sol-gel method followed by a reduction process. With excitation of UV/NUV light, the prepared SrAl 3 BO 7 :Eu 2+ ,Eu 3+ phosphors show not only the characteristic f-f transitions of Eu 3+ ion ( 5 D J → 7 F J,J' , J, J' = 0-3), but also the 5d → 4f transitions of Eu 2+ ion with comparable intensity from 400 to 700 nm in the whole visible spectral region. The luminescence color of the SrAl 3 BO 7 :Eu 2+ ,Eu 3+ phosphor can be tuned from blue, blue-green, white, and orange to orange-red by changing the excitation wavelength, the overall doping concentration of europium ions (Eu 2+ , Eu 3+ ), and the relative ratio of Eu 2+ to Eu 3+ ions to some extent. A single-phase white-light emission has been realized in SrAl 3 BO 7 :Eu 2+ ,Eu 3+ phosphor. The obtained SrAl 3 BO 7 :Eu 2+ ,Eu 3+ phosphor has potential application in the area of NUV white-light-emitting diodes.

Host composition dependent tunable multicolor emission in the single-phase Ba2(Ln(1-z)Tb(z))(BO3)2Cl:Eu phosphors.

PubMed

Xia, Zhiguo; Zhuang, Jiaqing; Meijerink, Andries; Jing, Xiping

2013-05-14

A new strategy based on the host composition design has been adopted to obtain efficient color-tunable emission from Ba2Ln(0.97-z)Tb(z)(BO3)2Cl:0.03Eu (Ln = Y, Gd and Lu, z = 0-0.97) phosphors. This study reveals that the single-phase Ba2Ln(1-z)Tb(z)(BO3)2Cl compounds can be applied to use allowed Eu(2+) absorption transitions to sensitize Eu(3+) emission via the energy transfer Eu(2+) → (Tb(3+))n → Eu(3+). The powder X-ray diffraction (XRD) and Rietveld refinement analysis shows single-phase Ba2Ln(1-z)Tb(z)(BO3)2Cl. As-prepared Ba2Ln(0.97-z)Tb(z)(BO3)2Cl:0.03Eu phosphors show intense green, yellow, orange and red emission under 377 nm near ultraviolet (n-UV) excitation due to a variation in the relative intensities of the Eu(2+), Tb(3+) and Eu(3+) emission depending on the Tb content (z) in the host composition, allowing color tuning. The variation in emission color is explained by energy transfer and has been investigated by photoluminescence and lifetime measurements and is further characterized by the Commission Internationale de l'éclairage (CIE) chromaticity indexes. The quantum efficiencies of the phosphors are high, up to 74%, and show good thermal stabilities up to 150 °C. This investigation demonstrates the possibility to sensitize Eu(3+) line emission by Eu(2+)via energy migration over Tb(3+) resulting in efficient color tunable phosphors which are promising for use in solid-state white light-emitting diodes (w-LEDs).

Multilayer design of hybrid phosphor film for application in LEDs

NASA Astrophysics Data System (ADS)

Güner, Tuğrul; Köseoğlu, Devrim; Demir, Mustafa M.

2016-10-01

Crosslinked polydimethylsiloxane (PDMS) composite coatings containing luminescent micrometer-sized yellow Y3Al5O12:Ce3+ (YAG:Ce3+) particles were prepared by spraying for potential applications in solid-state lighting. Blue light was down converted by phosphor particles to produce white light, yet poor color properties of YAG:Ce3+ stemmed from a deficiency of red. When nitride-based red phosphor was simply blended into the system, the electrostatic interaction of negatively charged YAG:Ce3+ and positively charged red phosphor particles caused remarkable clustering and heterogeneity in particle dispersion. Consequently, the light is dominantly blue and shifted to cold white. In other case, phosphor particles were sprayed onto the diffused polycarbonate substrate in stacked layers. Coatings with >80% inorganic content by mass with a thickness of 60 μm were subjected to thermal crosslinking, which the presence of the phosphor particles obstructed, presumably due to the hindrance of large phosphor particles in the diffusion of PDMS precursors. The coating of YAG:Ce3+ first followed by red phosphor in stacked layers produced better light output and color properties than the coating obtained by spraying the mixture at once. Monte Carlo simulation validated the hypothesis.

[Red reflex: prevention way to blindness in childhood].

PubMed

de Aguiar, Adriana Sousa Carvalho; Cardoso, Maria Vera Lúcia Moreira Leitão; Lúcio, Ingrid Martins Leite

2007-01-01

This study had as objective to investigate the result and the colour gradation of red reflex test in newborns (NB). It is a exploratory, quantitative study and the sample was 180 NB from maternity ward in Fortaleza-CE. From this, 156 showed result "no altered" and 24 "suspect". About the aspect of red reflex, 144 NB showed the same coloration in the two eyes, in 35 of this, the colour was red, in 33, orange reddish, in 46 orange colour, in 24 light yellow, in 6 yellow with whitish stains central. Of the suspect cases, the reflex was light yellow with whitish stains with lines. The nurse trained to accomplish the red reflex test can have important role at Neonatal Unit with actions about the prevention of ocular alterations in the childhood.

Effects of Sm3+ on Luminescent Properties of LiEu(0.55-x)Y0.45 (WO4)2Smx Red Phosphor

NASA Astrophysics Data System (ADS)

Zailani, N. S.; Ghazli, M. F.; Hussin, R.; Rahim, S. Z. Abd; Mat Saad, M. N.

2018-06-01

Phosphor materials have been widely applied in lighting and displays. Rare earth elements are amongst important elements in giving luminescent properties to the phosphor. The needs to reduce rare earth element in phosphor is of interest due to cost and environmental issue. The red phosphor LiEu(0.55-x)Y0.45(WO4)2 were synthesized by substituting Sm3+ in the lattice using solid-state reaction. The effect on the substitution of Sm3+ which acts as an activator will be analysed using X-ray powder diffraction (XRPD), scanning electron microscope (SEM) and photoluminescence spectra (PL). The structure of the compound was found to be as a monoclinic which referred to the reference patterns. The optimum amount was recorded for the activator to be obtained in the host lattice for replacing the Eu3+ place as well as enhancing the intensity of the emission. The findings reveal that LiEu(0.55-x)Y0.45(MoO4)2Smx can be a more efficient red phosphor candidate used white light emitting diodes (WLEDs) applications.

A potential single-phased emission-tunable silicate phosphor Ca3Si2O7:Ce3+,Eu2+ excited by ultraviolet light for white light emitting diodes

NASA Astrophysics Data System (ADS)

Lv, Wenzhen; Guo, Ning; Jia, Yongchao; Zhao, Qi; You, Hongpeng

2013-03-01

Single-phased Ca3Si2O7:Ce3+,Eu2+ phosphor has been successfully prepared by the high temperature solid-state method. The phosphor shows efficient excitation bands from 200 to 400 nm and adjustable emission bands through the energy transfer from the Ce3+ to Eu2+ ions. The color hues can change from blue towards white ultimately to orange by adjusting the percentage content of doping ions. The investigation reveals that an electric dipole-dipole reaction mechanism should be responsible for the energy transfer from the Ce3+ to Eu2+ ions. The critical distance was obtained from the spectral overlap in terms of Dexter's theory. The developed phosphor Ca3Si2O7:Ce3+,Eu2+ exhibits two bands at 440 and 625 nm, respectively, which reveling that it has a great potentiality to be an UV-convertible phosphor for white-light emitting diodes with low color temperature.

Organic light-emitting device with a phosphor-sensitized fluorescent emission layer

DOEpatents

Forrest, Stephen [Ann Arbor, MI; Kanno, Hiroshi [Osaka, JP

2009-08-25

The present invention relates to organic light emitting devices (OLEDs), and more specifically to OLEDS that emit light using a combination of fluorescent emitters and phosphorescent emitters. The emissive region of the devices of the present invention comprise at least one phosphor-sensitized layer which has a combined emission from a phosphorescent emitter and a fluorescent emitter. In preferred embodiments, the invention relates to white-emitting OLEDS (WOLEDs).

Luminescence properties of phosphate phosphor Ba{sub 3}Y(PO{sub 4}){sub 3}:Sm{sup 3+}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Fu; Liu, Yufeng, E-mail: liuyufeng4@126.com; Tian, Xiaodong

2015-05-15

A series of reddish orange-emitting phosphate phosphors Ba{sub 3}Y{sub 1−x}(PO{sub 4}){sub 3}:xSm{sup 3+}(0.01≤x≤0.20) were synthesized by solid-state reaction. X-ray diffraction and photoluminescence spectra were utilized to characterize the structure and luminescence properties of as-synthesized phosphors. The optimized phosphors Ba{sub 3}Y{sub 0.95}(PO{sub 4}){sub 3}:0.05Sm{sup 3+} present several excitation bands from 300 to 500 nm, and exhibit intense reddish orange-emitting properties. The energy transfer type between Sm{sup 3+} ions was confirmed as d–d interaction by using Van Uitert model. The chromatic properties of the typical sample Ba{sub 3}Y(PO{sub 4}){sub 3}:0.05Sm{sup 3+} phosphor have been found to have chromaticity coordinates of (0.583, 0.405),more » which are located in reddish orange region under the excitation of 401 nm. These results indicated that Ba{sub 3}Y(PO{sub 4}){sub 3}:Sm{sup 3+} phosphors have potential applications in the field of lighting and display due to their effective excitation in the near-ultraviolet range. - Graphical abstract: The color coordinates for 5 mol% Sm{sup 3+} doped Ba{sub 3}Y(PO{sub 4}){sub 3} phosphor were calculated to be (0.583, 0.405), which are located in reddish orange region under the excitation of 401 nm. The peaks of Ba{sub 3}Y{sub 0.95}(PO{sub 4}){sub 3}:0.05Sm{sup 3+} phosphor with the highest emission intensity at 600 nm are broader than those of Y{sub 2}O{sub 3}:Eu{sup 3+} and Y{sub 2}O{sub 2}S:Eu{sup 3+} phosphors. All these characteristics suggest that Ba{sub 3}Y(PO{sub 4}){sub 3}:Sm{sup 3+} phosphors are suitable for near-UV (370–410 nm) excitation and can be applicable to near UV-based WLEDs. ▪ - Highlights: • Different concentration Sm{sup 3+}-doped Ba{sub 3}Y(PO{sub 4}){sub 3} phosphors were fabricated by solid state method. • The optimized phosphors present the several excitation bands from 300 to 500 nm. • The Ba{sub 3}Y(PO{sub 4}){sub 3}:Sm{sup 3+} shows bright reddish

Cesium lead halide perovskite quantum dot-based warm white light-emitting diodes with high color rendering index

NASA Astrophysics Data System (ADS)

Bi, Ke; Wang, Dan; Wang, Peng; Duan, Bin; Zhang, Tieqiang; Wang, Yinghui; Zhang, Hanzhuang; Zhang, Yu

2017-05-01

White light-emitting diodes (WLEDs) were fabricated by employing a combination of a commercial yellow emission Ce3+-doped Y3Al5O12 (YAG:Ce)-based phosphor and all-inorganic perovskite quantum dots pumped with blue LED chip. Perovskite quantum dot solution was used as the color conversion layer with liquid-type structure. Red-emitting materials based on cesium lead halide (CsPb(X)3) perovskite quantum dots were introduced to generate WLEDs with high efficacy and high color rendering index through compensating the red emission of the YAG:Ce phosphor-based commercialized WLEDs. The experimental results suggested that the luminous efficiency and color rendering index of the as-prepared WLED device could reach up to 84.7 lm/W and 89, respectively. The characteristics of those devices including correlated color temperature (CCT), color rendering index (CRI), and color coordinates were observed under different forward currents. The as-fabricated warm WLEDs showed excellent color stability against the increasing current, while the color coordinates shifted slightly from (0.3837, 0.3635) at 20 mA to (0.3772, 0.3592) at 120 mA and color temperature tuned from 3803 to 3953 K.

Poly(vinylpyrrolidone) supported copper nanoclusters: glutathione enhanced blue photoluminescence for application in phosphor converted light emitting devices

NASA Astrophysics Data System (ADS)

Wang, Zhenguang; Susha, Andrei S.; Chen, Bingkun; Reckmeier, Claas; Tomanec, Ondrej; Zboril, Radek; Zhong, Haizheng; Rogach, Andrey L.

2016-03-01

Poly(vinylpyrrolidone) supported Cu nanoclusters were synthesized by reduction of Cu(ii) ions with ascorbic acid in water, and initially showed blue photoluminescence with a quantum yield of 8%. An enhancement of the emission quantum yield has been achieved by treatment of Cu clusters with different electron-rich ligands, with the most pronounced effect (photoluminescence quantum yield of 27%) achieved with glutathione. The bright blue emission of glutathione treated Cu NCs is fully preserved in the solid state powder, which has been combined with commercial green and red phosphors to fabricate down-conversion white light emitting diodes with a high colour rendering index of 92.Poly(vinylpyrrolidone) supported Cu nanoclusters were synthesized by reduction of Cu(ii) ions with ascorbic acid in water, and initially showed blue photoluminescence with a quantum yield of 8%. An enhancement of the emission quantum yield has been achieved by treatment of Cu clusters with different electron-rich ligands, with the most pronounced effect (photoluminescence quantum yield of 27%) achieved with glutathione. The bright blue emission of glutathione treated Cu NCs is fully preserved in the solid state powder, which has been combined with commercial green and red phosphors to fabricate down-conversion white light emitting diodes with a high colour rendering index of 92. Electronic supplementary information (ESI) available: The optical spectra of control experiments for Cu NC synthesis, optimization of the reaction conditions, and spectra for LEDs chips and blue LEDs. See DOI: 10.1039/c6nr00806b

Fabrication of white light-emitting diodes based on UV light-emitting diodes with conjugated polymers-(CdSe/ZnS) quantum dots as hybrid phosphors.

PubMed

Jung, Hyunchul; Chung, Wonkeun; Lee, Chang Hun; Kim, Sung Hyun

2012-07-01

White light-emitting diodes (LEDs) were fabricated using GaN-based 380-nm UV LEDs precoated with the composite of blue-emitting polymer (poly[(9,9-dihexylfluorenyl-2,7-diyl)-alt-co-(2-methoxy-5-{2-ethylhexyloxy)-1 ,4-phenylene)]), yellow green-emitting polymer (poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1',3}-thiadiazole)]), and 605-nm red-emitting quantum dots (QDs). CdSe cores were obtained by solvothermal route using CdO, Se precursors and ZnS shells were synthesized by using diethylzinc, and hexamethyldisilathiane precursors. The optical properties of CdSe/ZnS QDs were characterized by UV-visible and photoluminescence (PL) spectra. The structural data and composition of the QDs were transmission electron microscopy (TEM), and EDX technique. The quantum yield and size of the QDs were 58.7% and about 6.7 nm, respectively. Three-band white light was generated by hybridizing blue (430 nm), green (535 nm), and red (605 nm) emission. The color-rendering index (CRI) of the device was extremely improved by introducing the QDs. The CIE-1931 chromaticity coordinate, color temperature, and CRI of a white LED at 20 mA were (0.379, 0.368), 3969 K, and 90, respectively.

UV excited downconversion luminescence properties of Eu3+: NaZnPO4 phosphors

NASA Astrophysics Data System (ADS)

Mukhopadhyay, Lakshmi; Rai, Vineet Kumar

2018-05-01

The structural and optical properties of Eu3+: NaZnPO4 phosphors prepared by chemical coprecipitation method have been studied. The phase formation and morphology of the phosphors have been confirmed by the X-ray diffraction (XRD) and Field emission scanning electron microscopy (FESEM) analysis. The downconversion emission spectra upon 392 nm excitation exhibit five emission bands centred at ˜ 575 nm, ˜ 590 nm, ˜ 612 nm, ˜ 660 nm and ˜ 702 nm corresponding to the 5D0→7F0, 5D0→7F1, 5D0→7F2, 5D0→7F3 and 5D0→7F4 transitions of Eu3+ ions respectively. The observed downconversion emission peaks can be explained with the help of suitable energy level diagram. The CIE chromaticity diagram shows the purity of the emitted colour from the prepared phosphors. The present phosphors emit in intense red region which shows the applicability of the phosphors in red light emitting display devices.

Luminescence Properties of Ca19Ce(PO4)14:A (A = Eu3+/Tb3+/Mn2+) Phosphors with Abundant Colors: Abnormal Coexistence of Ce4+/3+-Eu3+ and Energy Transfer of Ce3+ → Tb3+/Mn2+ and Tb3+-Mn2.

PubMed

Shang, Mengmeng; Liang, Sisi; Lian, Hongzhou; Lin, Jun

2017-06-05

A series of Eu 3+ /Tb 3+ /Mn 2+ -ion-doped Ca 19 Ce(PO 4 ) 14 (CCPO) phosphors have been prepared via the conventional high-temperature solid-state reaction process. Under UV radiation, the CCPO host presents a broad blue emission band from Ce 3+ ions, which are generated during the preparation process because of the formation of deficiency. The Eu 3+ -doped CCPO phosphors can exhibit magenta to red-orange emission as a result of the abnormal coexistence of Ce 3+ /Ce 4+ /Eu 3+ and the metal-metal charge-transfer (MMCT) effect between Ce 3+ and Eu 3+ . When Tb 3+ /Mn 2+ are doped into the hosts, the samples excited with 300 nm UV light present multicolor emissions due to energy transfer (ET) from the host (Ce 3+ ) to the activators with increasing activator concentrations. The emitting colors of CCPO:Tb 3+ phosphors can be tuned from blue to green, and the CCPO:Mn 2+ phosphors can emit red light. The ET mechanism from the host (Ce 3+ ) to Tb 3+ /Mn 2+ is demonstrated to be a dipole-quadrapole interaction for Ce 3+ → Tb 3+ and an exchange interaction for Ce 3+ → Mn 2+ in CCPO:Tb 3+ /Mn 2+ . Abundant emission colors containing white emission were obtained in the Tb 3+ - and Mn 2+ -codoped CCPO phosphors through control of the levels of doped Tb 3+ and Mn 2+ ions. The white-emitted CCPO:Tb 3+ /Mn 2+ phosphor exhibited excellent thermal stability. The photoluminescence properties have shown that these materials might have potential for UV-pumped white-light-emitting diodes.

Reduced graphene oxide enwrapped phosphors for long-term thermally stable phosphor converted white light emitting diodes

NASA Astrophysics Data System (ADS)

Anoop, Gopinathan; Rani, Janardhanan R.; Lim, Juhwan; Jang, Myoung Soo; Suh, Dong Wook; Kang, Shinill; Jun, Seong Chan; Yoo, Jae Soo

2016-09-01

The long-term instability of the presently available best commercial phosphor-converted light-emitting diodes (pcLEDs) is the most serious obstacle for the realization of low-cost and energy-saving lighting applications. Emission from pcLEDs starts to degrade after approximately 200 h of operation because of thermal degradation of the phosphors. We propose a new strategy to overcome this thermal degradation problem of phosphors by wrapping the phosphor particles with reduced graphene oxide (rGO). Through the rGO wrapping, we have succeeded in controlling the thermal degradation of phosphors and improving the stability of fabricated pcLEDs. We have fabricated pcLEDs with long-term stability that maintain nearly 98% of their initial luminescence emission intensity even after 800 h of continuous operation at 85 °C and 85% relative humidity. The pcLEDs fabricated using SrBaSi2O2N2:Eu2+ phosphor particles wrapped with reduced graphene oxide are thermally stable because of enhanced heat dissipation that prevents the ionization of Eu2+ to Eu3+. We believe that this technique can be applied to other rare-earth doped phosphors for the realization of highly efficient and stable white LEDs.

Antioxidant effectiveness of organically and non-organically grown red oranges in cell culture systems.

PubMed

Tarozzi, A; Hrelia, S; Angeloni, C; Morroni, F; Biagi, P; Guardigli, M; Cantelli-Forti, G; Hrelia, P

2006-03-01

Consumers consider plant food products from organic origin healthier than the corresponding conventional plant foods. Clear experimental evidence supporting this assumption is still lacking. To determine if the organic red oranges have a higher phyto-chemical content (i. e., phenolics, anthocyanins and ascorbic acid), total antioxidant activity and in vitro bioactivity, in terms of protective effect against oxidative damage at cellular level, than nonorganic red oranges. Total phenolics were measured using the Folin Ciocalteau assay, while total anthocyanins and ascorbic acid levels were determined by spectrophotometric and HPLC analysis, respectively. In addition, the total antioxidant activity of red orange extracts was measured by the ABTS(*+) test. The ability of red orange extracts to counteract conjugated diene containing lipids and free radical production in cultured rat cardiomyocytes and differentiated Caco-2 cells, respectively, was assessed. Organic oranges had significantly higher total phenolics, total anthocyanins and ascorbic acid levels than the corresponding non-organic oranges (all p < 0.05). Moreover, the organic orange extracts had a higher total antioxidant activity than non-organic orange extracts (p < 0.05). In addition, our results indicate that red oranges have a strong capacity of inhibiting the production of conjugated diene containing lipids and free radicals in rat cardiomyocytes and differentiated Caco-2 cells, respectively. Statistically higher levels of antioxidant activity in both cell models were found in organically grown oranges as compared to those produced by integrated agriculture practice. Our results clearly show that organic red oranges have a higher phytochemical content (i. e., phenolics, anthocyanins and ascorbic acid), total antioxidant activity and bioactivity than integrated red oranges. Further studies are needed to confirm whether the organic agriculture practice is likely to increase the antioxidant activity of

Polymorphism in molecular solids: an extraordinary system of red, orange, and yellow crystals.

PubMed

Yu, Lian

2010-09-21

Diamond and graphite are polymorphs of each other: they have the same composition but different structures and properties. Many other substances exhibit polymorphism: inorganic and organic, natural and manmade. Polymorphs are encountered in studies of crystallization, phase transition, materials synthesis, and biomineralization and in the manufacture of specialty chemicals. Polymorphs can provide valuable insights into crystal packing and structure-property relationships. 5-Methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile, known as ROY for its red, orange, and yellow crystals, has seven polymorphs with solved structures, the largest number in the Cambridge Structural Database. First synthesized by medicinal chemists, ROY has attracted attention from solid-state chemists because it demonstrates the remarkable diversity possible in organic solids. Many structures of ROY polymorphs and their thermodynamic properties are known, making ROY an important model system for testing computational models. Though not the most polymorphic substance on record, ROY is extraordinary in that many of its polymorphs can crystallize simultaneously from the same liquid and are kinetically stable under the same conditions. Studies of ROY polymorphs have revealed a new crystallization mechanism that invalidates the common view that nucleation defines the polymorph of crystallization. A slow-nucleating polymorph can still dominate the product if it grows rapidly and nucleates on another polymorph. Studies of ROY have also helped understand a new, surprisingly fast mode of crystal growth in organic liquids cooled to the glass transition temperature. This growth mode exists only for those polymorphs that have more isotropic, and perhaps more liquid-like, packing. The rich polymorphism of ROY results from a combination of favorable thermodynamics and kinetics. Not only must there be many polymorphs of comparable energies or free energies, many polymorphs must be kinetically stable and

Boron-Containing Red Light-Emitting Phosphors And Light Sources Incorporating The Same

DOEpatents

Srivastava, Alok Mani; Comanzo, Holly Ann; Manivannan, Venkatesan

2006-03-28

A boron-containing phosphor comprises a material having a formula of AD1-xEuxB9O16, wherein A is an element selected from the group consisting of Ba, Sr, Ca, Mg, and combinations thereof; D is at least an element selected from the group consisting of rare-earth metals other than europium; and x is in the range from about 0.005 to about 0.5. The phosphor is used in a blend with other phosphors in a light source for generating visible light with a high color rendering index.

2D SiNx photonic crystal coated Y3Al5O12:Ce3+ ceramic plate phosphor for high-power white light-emitting diodes.

PubMed

Park, Hoo Keun; Oh, Jeong Rok; Do, Young Rag

2011-12-05

This paper reports the optical effects of a two-dimensional (2D) SiNx photonic crystal layer (PCL) on Y3Al5O12:Ce3+ (YAG:Ce) yellow ceramic plate phosphor (CPP) in order to enhance the forward emission of YAG:Ce CPP-capped high-power white light-emitting diodes (LEDs). By adding the 2D SiNx PCL with a 580 nm lattice constant, integrated yellow emission was improved by a factor of 1.72 compared to that of a conventional YAG:Ce CPP capped on a blue LED cup. This enhanced forward yellow emission is attributed to increased extraction of yellow emission light and improved absorption of blue excitation light through Bragg scattering and/or the leaky modes produced by the 2D PCLs. The introduction of 2D PCL can also reduce the wide variation of optical properties as a function of both ambient temperature and applied current, compared to those of a high-power YAG:Ce CPP-capped LED.

Application of a novel red-emitting cationic iridium(III) coordination polymer in warm white light-emitting diodes

NASA Astrophysics Data System (ADS)

Chen, Mingxian; Sun, Riyong; Ye, Yanchun; Tang, Huaijun; Dong, Xueyan; Yan, Jialun; Wang, Kaimin; Zhou, Qiang; Wang, Zhengliang

2018-02-01

A novel red-emitting cationic iridium(III) coordination polymer using 2-(9-(2-ethylhexyl)-9H-carbazol-3-yl)benzo[d]thiazole as main ligands, 4,4‧-bipyridine as bridging auxiliary ligands and Clˉ as anions was synthesized. It had high thermal stability with a thermal decomposition temperature (Td) of 345 °C and low thermal quenching with an activation energy (Ea) of 0.2760 eV, with the temperature increasing from 20 °C to 100 °C, its photoluminescent intensity decreased to 76.7%. It can be efficiently excited by blue light of GaN chips, the cold white light of GaN-based LEDs using only Y3Al5O12:Ce3+ (YAG:Ce, 7.0 wt% in silicone) as phosphors can become warmer when it was blended in. When blending concentrations were 0.1 wt% and 0.2 wt%, the cold white light became neutral white light, the correlated color temperature (CCT) decreased from 6157 K to 5240 K, then to 4043 K, the color rendering index (CRI) changed from 72.7 to 81.3, then to 78.6, the luminous efficiency (ηL) changed from 134.1 lm·w-1 to 61.9 lm·w-1, then to 46.3 lm·w-1, the Commission Internationale de L'Eclairage (CIE) chromaticity coordinates changed from (0.32, 0.33) to (0.34, 0.33), then to (0.38, 0.36). At 0.3 wt%, the light became warm white light, the corresponding CCT was 3475 K, CRI was 75.6, ηL was 36.9 lm·w-1, and CIE value was (0.41, 0.40). The results suggest the coordination polymer is a promising red-emitting phosphor candidate for neutral and warm white LEDs, especially for warm white LEDs.

Conversion of Biowaste Asian Hard Clam (Meretrix lusoria) Shells into White-Emitting Phosphors for Use in Neutral White LEDs.

PubMed

Chang, Tsung-Yuan; Wang, Chih-Min; Lin, Tai-Yuan; Lin, Hsiu-Mei

2016-12-02

The increasing volume and complexity of waste associated with the modern economy poses a serious risk to ecosystems and human health. However, the remanufacturing and recycling of waste into usable products can lead to substantial resource savings. In the present study, clam shell waste was first transformed into pure and well-crystallized single-phase white light-emitting phosphor Ca₉Gd(PO₄)₇:Eu 2+ ,Mn 2+ materials. The phosphor Ca₉Gd(PO₄)₇:Eu 2+ ,Mn 2+ materials were synthesized by the solid-state reaction method and the carbothermic reduction process, and then characterized and analyzed by means of X-ray diffraction (XRD) and photoluminescence (PL) measurements. The structural and luminescent properties of the phosphors were investigated as well. The PL and quantum efficiency measurements showed that the luminescence properties of clam shell-based phosphors were comparable to that of the chemically derived phosphors. Moreover, white light-emitting diodes were fabricated through the integration of 380 nm chips and single-phase white light-emitting phosphors (Ca 0.979 Eu 0.006 Mn 0.015 )₉Gd(PO₄)₇ into a single package of a white light emitting diode (WLED) emitting a neutral white light of 5298 K with color coordinates of (0.337, 0.344).

Conversion of Biowaste Asian Hard Clam (Meretrix lusoria) Shells into White-Emitting Phosphors for Use in Neutral White LEDs

PubMed Central

Chang, Tsung-Yuan; Wang, Chih-Min; Lin, Tai-Yuan; Lin, Hsiu-Mei

2016-01-01

The increasing volume and complexity of waste associated with the modern economy poses a serious risk to ecosystems and human health. However, the remanufacturing and recycling of waste into usable products can lead to substantial resource savings. In the present study, clam shell waste was first transformed into pure and well-crystallized single-phase white light-emitting phosphor Ca9Gd(PO4)7:Eu2+,Mn2+ materials. The phosphor Ca9Gd(PO4)7:Eu2+,Mn2+ materials were synthesized by the solid-state reaction method and the carbothermic reduction process, and then characterized and analyzed by means of X-ray diffraction (XRD) and photoluminescence (PL) measurements. The structural and luminescent properties of the phosphors were investigated as well. The PL and quantum efficiency measurements showed that the luminescence properties of clam shell-based phosphors were comparable to that of the chemically derived phosphors. Moreover, white light-emitting diodes were fabricated through the integration of 380 nm chips and single-phase white light-emitting phosphors (Ca0.979Eu0.006Mn0.015)9Gd(PO4)7 into a single package of a white light emitting diode (WLED) emitting a neutral white light of 5298 K with color coordinates of (0.337, 0.344). PMID:28774101

Luminescence properties and warm white LED application of a ternary-alkaline fluoride red phosphor K2NaAlF6:Mn4+ .

PubMed

Wang, L Y; Song, E H; Deng, T T; Zhou, Y Y; Liao, Z F; Zhao, W R; Zhou, B; Zhang, Q Y

2017-08-14

Herein, a Mn 4+ ion doped complex ternary-alkaline fluoride red phosphor K 2 NaAlF 6 :Mn 4+ has been synthesized through a facile two-step co-precipitation method at room temperature. The crystal structure, morphological properties and influence of the dopant concentration, temperature and humidity on luminescence properties as well as the performance of the as-synthesized phosphor used in white light emitting diodes (WLEDs) were investigated carefully. Intense absorption in the blue region (∼460 nm) and bright narrow-band red emission (∼630 nm) with high color purity were observed from this resultant powder. Temperature-dependent investigation and reliability examination in a HTHH environment (85 °C high temperature and 85% high humidity) indicate that the obtained ternary-alkaline fluoride phosphor K 2 NaAlF 6 :Mn 4+ presents more exceptional thermal quenching behavior and longevity compared to some other binary-alkaline fluorides. Moreover, using K 2 NaAlF 6 :Mn 4+ as a red light component, a warm WLED with a preferable color rendering index (R a = 85.5) and luminous efficacy (LE = 91.2 lm W -1 ) as well as a low corresponding color temperature (CCT = 3650 K) is easily achieved, further revealing the great potential of the as-prepared ternary-alkaline fluoride red phosphor K 2 NaAlF 6 :Mn 4+ for WLED applications.

Triple energy transfer and color tuning in Tb3+ and Eu3+-coactivated apatite-type gadolinium-containing phosphors

NASA Astrophysics Data System (ADS)

Guo, Ning; Liang, Qimeng; Li, Shuo; Ouyang, Ruizhuo; Lü, Wei

2017-11-01

A family of apatite-type fluorophosphate phosphors with general formula Sr3Gd(1-m-n)Na(PO4)3F:mTb3+,nEu3+ (SGN:mTb3+,nEu3+) have been synthesized via the high-temperature solid-state reaction method. Triple energy transfer processes from Gd3+ in the host to both Tb3+ and Eu3+, as well as from Tb3+ to Eu3+ have been verified by the photoluminescence spectra. Under the excitation of UV light, both green line from the transitions of Tb3+ and red line origin from the transitions of Eu3+ have been simultaneously observed in a single phase phosphor, which makes a promise for tunable color emissions from yellowish-green through yellow and ultimately to reddish-orange by simply adjusting the Eu3+ content (n) in SGN:0.20Tb3+,nEu3+ phosphors. Additionally, the energy transfer from the Tb3+ to the Eu3+ ions has been demonstrated to be a resonant type via a quadrupole-quadrupole mechanism based on the Dexter's theoretical model, and the energy transfer efficiency increases with an increase in Eu3+ concentration.

LED lamp

DOEpatents

Galvez, Miguel; Grossman, Kenneth; Betts, David

2013-11-12

There is herein described a lamp for providing white light comprising a plurality of light sources positioned on a substrate. Each of said light sources comprises a blue light emitting diode (LED) and a dome that substantially covers said LED. A first portion of said blue light from said LEDs is transmitted through said domes and a second portion of said blue light is converted into a red light by a first phosphor contained in said domes. A cover is disposed over all of said light sources that transmits at least a portion of said red and blue light emitted by said light sources. The cover contains a second phosphor that emits a yellow light in response to said blue light. The red, blue and yellow light combining to form the white light and the white light having a color rendering index (CRI) of at least about 80.

Ultrafast Self-Crystallization of High-External-Quantum-Efficient Fluoride Phosphors for Warm White Light-Emitting Diodes.

PubMed

Zhou, Wenli; Fang, Mu-Huai; Lian, Shixun; Liu, Ru-Shi

2018-05-30

In this study, we used HF (as good solvent) to dissolve K 2 GeF 6 and K 2 MnF 6 and added ethanol (as poor solvent) to cause ultrafast self-crystallization of K 2 GeF 6 :Mn 4+ crystals, which had an unprecedentedly high external quantum efficiency that reached 73%. By using the red phosphor, we achieved a high-quality warm white light-emitting diode with color-rendering index of R a = 94, R9 = 95, luminous efficacy of 150 lm W -1 , and correlated color temperature at 3652 K. Furthermore, the good-poor solvent strategy can be used to fast synthesize other fluorides.

Crystal structure, energy transfer and tunable luminescence properties of Ca8ZnCe(PO4)7:Eu2+,Mn2+ phosphor

NASA Astrophysics Data System (ADS)

Ding, Chong; Tang, Wanjun

2018-02-01

Single-phased Ca8ZnCe(PO4)7:Eu2+,Mn2+ phosphors with whitlockite-type structure have been prepared via the combustion-assisted synthesis technique. The XRD pattern show that the as-obtained phosphors crystallize in a trigonal phase with space group of R-3c (161). Ca8ZnCe(PO4)7 host is full of sensitizers (Ce3+) and the Ce3+ emission at different lattice sites has been discussed. The efficient energy transfers from Ce3+ ions to Eu2+/Mn2+ ions and from Eu2+ to Mn2+ have been validated. Under UV excitation, the emitting color of Ca8ZnCe(PO4)7:Eu2+/Mn2+ samples can be modulated from violet blue to green and from violet blue to red-orange by the energy transfers of Ce3+→Eu2+ and Ce3+→Mn2+, respectively. Additionally, white emission has been obtained through adjusting the relative concentrations of Eu2+ and Mn2+ ions in the Ca8ZnCe(PO4)7 host under UV excitation. These results indicate that as-prepared Ca8ZnCe(PO4)7:Eu2+,Mn2+ may be a potential candidate as color-tunable white light-emitting phosphors.

Enhanced efficiency of luminescence with stoichiometry control in LiGd(W(1-x)MoxO4)2:Eu3+ red phosphors

NASA Astrophysics Data System (ADS)

Kavi Rasu, K.; Balaji, D.; Moorthy Babu, S.

2017-06-01

A series of LiGd(W(1-x)MoxO4)2 [hereafter LGWM]:Eu3+(x=0.00 to 1.00) red-emitting phosphors were synthesized by sol-gel method. Metal nitrates were used as starting materials with citric acid as chelator and ethylene glycol as binder. Synthesized gel was pre-fired at 523 K and calcined at 1073 K using resistive furnace in air atmosphere. The crystallinity, surface morphology and luminescent properties of the phosphors were investigated using powder X-ray diffraction (XRD), scanning electron microscope (SEM) and fluorescence spectrophotometry respectively. The intensity of the red emission at 615 nm for 5D0→7F2 electric dipole transition increases as the content of Mo6+ was increased and reach a maximum, when the relative ratio of W/Mo is 1:1 under 396 nm excitation.

Combination of carbon dot and polymer dot phosphors for white light-emitting diodes.

PubMed

Sun, Chun; Zhang, Yu; Sun, Kai; Reckmeier, Claas; Zhang, Tieqiang; Zhang, XiaoYu; Zhao, Jun; Wu, Changfeng; Yu, William W; Rogach, Andrey L

2015-07-28

We realized white light-emitting diodes with high color rendering index (85-96) and widely variable color temperatures (2805-7786 K) by combining three phosphors based on carbon dots and polymer dots, whose solid-state photoluminescence self-quenching was efficiently suppressed within a polyvinyl pyrrolidone matrix. All three phosphors exhibited dominant absorption in the UV spectral region, which ensured the weak reabsorption and no energy transfer crosstalk. The WLEDs showed excellent color stability against the increasing current because of the similar response of the tricolor phosphors to the UV light variation.

A potential green emitting citrate gel synthesized NaSrBO3:Tb3+ phosphor for display application

NASA Astrophysics Data System (ADS)

Bedyal, A. K.; Kumar, Vinay; Swart, H. C.

2018-04-01

A potential green emitting NaSrBO3:Tb3+ (1-9 mol%) phosphor was synthesized by a citrate gel combustion method. X-ray diffraction patterns confirmed the monoclinic phase of the phosphor. The phosphor emitted intense green emission under near-UV and electron excitation due to the characteristic transitions 5D4→7F6(488 nm),5D4→7F5(544 nm),5D4→7F4(586 nm) and 5D4→7F3(622 nm) of Tb3+ ions. The optimal molar concentration of Tb3+ ions was found to be 6 mol%, after that concentration quenching occurred. The dipole-dipole interaction was found to be accountable for energy transfer between the Tb3+ ions. X-ray photoelectron spectroscopy was carried out to analyze the chemical states of the elements and suggest that terbium was mostly presented in the (+3) valance state in the phosphor. The approximated Commission Internationale de l‧Eclairage coordinates for the PL (0.31, 0.61) and CL (0.33, 0.57) were found to be very close to the well-known green emitting phosphor. The obtained results suggest that the studied phosphor could be an ultimate choice for green emission in display applications.

Luminescence properties of Eu 3+ and Sm 3+ coactivated Gd(III) tungstate phosphor for light-emitting diodes

NASA Astrophysics Data System (ADS)

Wei, Qiong; Chen, Donghua

2009-09-01

Rare-earth ions coactivated red phosphors Gd 0.2RE 1.8(WO 4) 3 (RE=Eu 3+ and Sm 3+) were synthesized by conventional solid-state reaction using boric acid as a flux agent. The samples were characterized by X-ray diffractometer (XRD), energy-dispersive X-ray spectrometer (EDS) and luminescence spectrometer (LS). The results showed that the Eu-Sm system exhibits higher emission intensity than those of the Eu single-doped system and Sm separate-doped system under ultraviolet (UV) radiation. Samarium(III) ions are effective in broadening and strengthened absorptions around 400 nm. Furthermore, it exhibits enhanced luminescence emission. when the mole ratio of boric acid is about 0.16, the luminescence capability is optimum. Two strongest lines at ultraviolet (394 nm) and blue (465 nm) in excitation spectra of these phosphors match well with the output wavelengths of UV and blue GaN-based light-emitting diodes (LEDs) chips.

Highly Efficient Carbon Dots with Reversibly Switchable Green-Red Emissions for Trichromatic White Light-Emitting Diodes.

PubMed

Yuan, Biao; Guan, Shanyue; Sun, Xingming; Li, Xiaoming; Zeng, Haibo; Xie, Zheng; Chen, Ping; Zhou, Shuyun

2018-05-09

Carbon dots (CDs) have potentials to be utilized in optoelectronic devices, bioimaging, and photocatalysis. The majority of the current CDs with high quantum yield to date were limited in the blue light emission region. Herein, on the basis of surface electron-state engineering, we report a kind of CDs with reversible switching ability between green and red photoluminescence with a quantum yield (QY) of both up to 80%. Highly efficient green and red solid-state luminescence is realized by doping CDs into a highly transparent matrix of methyltriethoxysilane and 3-triethoxysilylpropylamine to form CDs/gel glasses composites with QYs of 80 and 78%. The CDs/gel glasses show better transmittance in visible light bands and excellent thermal stability. A blue-pumped CDs/gel glasses phosphor-based trichromatic white light-emitting diode (WLED) is realized, whose color rendering index is 92.9. The WLED gets the highest luminous efficiency of 71.75 lm W -1 in CDs-based trichromatic WLEDs. This work opens a door for developing highly efficient green- and red-emissive switching CDs which were used as phosphors for WLEDs and have the tendency for applications in other fields, such as sensing, bioimaging, and photocatalysis.

Study on photoluminescence and energy transfer of Eu3+/Sm3+ single-doped and co-doped BaB8O13 phosphors

NASA Astrophysics Data System (ADS)

Lephoto, Mantwa A.; Tshabalala, Kamohelo G.; Motloung, Selepe J.; Ahemen, Iorkyaa; Ntwaeaborwa, Odireleng M.

2018-04-01

A series of Sm3+, Eu3+ and Eu3+- Sm3+ doped BaB8O13 were synthesized by using a solution combustion method. When excited at 394 nm, BaB8O13: Eu3+ emits red light, and the strongest peak was located at 614 nm, which is attributed to the 5D0→7F2 transition of Eu3+. BaB8O13: Sm3+ produced red-orange light, and the major emission peak was located at 596 nm under the 402 nm radiation excitation, which is assigned to the 4G5/2→6H7/2 transition of Sm3+. When excited at 402 nm, the PL emission intensity from BaB8O13: 0.05Eu3+; 0.005Sm3+ at 614 nm was enhanced considerably compared to that of the sample without Sm3+, suggesting that energy was transferred from Sm3+ to Eu3+. The Commission International de I‧Eclairage (CIE) chromaticity coordinates of BaB8O13: 0.05Eu3+; 0.005Sm3+ powder phosphor (0.637, 0.362) are located in the red region indicating that the phosphor can serve as a source of red light in LEDs.

High-efficiency orange and tandem white organic light-emitting diodes using phosphorescent dyes with horizontally oriented emitting dipoles.

PubMed

Lee, Sunghun; Shin, Hyun; Kim, Jang-Joo

2014-09-03

Tandem white organic light-emitting diodes (WOLEDs) using horizontally oriented phosphorescent dyes in an exciplex-forming co-host are presented, along with an orange OLED. A high external quantum efficiency of 32% is achieved for the orange OLED at 1000 cd m(-2) and the tandem WOLEDs exhibit a high maximum EQE of 54.3% (PE of 63 lm W(-1)). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of K2SiF6:Mn4+ phosphor for LED lamp

NASA Astrophysics Data System (ADS)

Takarkhede, M. G.; Patil, R. R.; Moharil, S. V.; Joshi, C. P.; Talewar, Rupesh

2018-05-01

Now a days red emitting Mn4+ activated dialkali fluorosilicate phosphors have found applications in solid state lighting and displays. In this paper we describe development of K2SiF6 phosphor doped with Mn synthesized by simple method using Si metal powder with addition of oxidizing agent KMnO4. The photoluminescence spectra of K2SiF6:Mn show that emission is in the red region. In addition to this we studied LED spectra by coating the LED with phosphor mixed in different proportions with epoxy.

Structural studies of a green-emitting terbium doped calcium zinc phosphate phosphor

NASA Astrophysics Data System (ADS)

Ramesh, B.; Dillip, G. R.; Rambabu, B.; Joo, S. W.; Raju, B. Deva Prasad

2018-03-01

In this study, a new green emitting CaZn2(PO4)2:Tb3+ phosphors were synthesized through solid-state reaction route. The phosphors were characterized structurally by X-ray diffraction, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). All the synthesized phosphors were crystallized in triclinic crystal structure with P 1 bar space group. The phosphate groups in the phosphors were confirmed by FTIR analysis. The surface elements O 1s, P 2p, Ca 2p, Zn 2p and Tb 3d were studied by high-resolution XPS spectra. Upon excitation at 378 nm, the dominant green emission of CaZn2(PO4)2:Tb3+ phosphors at 542 nm were noticed in the emission spectra. For various emission wavelengths (at 435 and 489 nm) and constant excitation wavelength (at 378 nm), the decay curves have shown two different decay dynamics of phosphors. The lighting properties such as Commission International de l'Eclairage (x = 0.319, y = 0.398) and color temperature (5995 K) were calculated.

Synthesis and electrophosphorescence of iridium complexes containing benzothiazole-based ligands.

PubMed

Liu, Di; Ren, Huicai; Deng, Lijun; Zhang, Ting

2013-06-12

Four heteroleptic bis-cyclometalated iridium(III) complexes containing 2-aryl-benzothiazole ligands, in which the aryl is dibenzofuran-2-yl [Ir(O-bt)2(acac)], dibenzothiophene-2-yl [Ir(S-bt)2(acac)], dibenzothiophene-S,S-dioxide-2-yl [Ir(SO2-bt)2(acac)] and 4-(diphenylphosphoryl)phenyl [Ir(PO-bt)2(acac)], have been synthesized and characterized for use in organic light-emitting diodes (OLEDs). These complexes emit bright yellow (551 nm) to orange-red (598 nm) phosphorescence at room temperature, the peak wavelengths of which can be finely tuned depending upon the electronic properties of the aryl group in the 2-position of benzothiazole. The strong electron-withdrawing aryls such as dibenzothiophene-S,S-dioxide2-yl and 4-(diphenylphosphoryl)phenyl caused bathochromatic shift of the iridium complex phosphorescence. These iridium complexes were used as doped emitters to fabricate yellow to orange-red OLEDs and good performance was obtained. In particular, a maximum luminance efficiency of 58.4 cd A(-1) (corresponding to 30.6 lm W(-1) and 19%) with CIE coordinates of (0.45, 0.52) was achieved for Ir(O-bt)2(acac)-based yellow device. Furthermore, the yellow emitting Ir(S-bt)2(acac) was used to fabricate two-element white OLED that exhibited a high efficiency of 32.4 cd A(-1) with CIE coordinates of (0.28, 0.44).

Composite phase ceramic phosphor of Al₂O₃-Ce:YAG for high efficiency light emitting.

PubMed

Tang, Yanru; Zhou, Shengming; Chen, Chong; Yi, Xuezhuan; Feng, Yue; Lin, Hui; Zhang, Shuai

2015-07-13

We present our achievement which is a ceramic plate phosphorable to produce white light when directly combined with commercially available blue light emitting diodes. The ceramic phase structure is that the Al₂O₃ particle is uniformly distributed in the Ce:YAG matrix. The Al₂O₃-Ce:YAG ceramic phosphor has a better luminous efficacy than the transparent Ce:YAG ceramic phosphor under the same test condition. The Al₂O₃ particle plays an important role in promoting the luminous efficacy. The Al₂O₃ particle changes the propagation of the light in ceramic, and it reduces the total internal reflection. That is why the composite phase ceramic phosphor improves extraction efficiency of light.

Red Orange: Experimental Models and Epidemiological Evidence of Its Benefits on Human Health

PubMed Central

Galvano, Fabio; Mistretta, Antonio; Marventano, Stefano; Nolfo, Francesca; Calabrese, Giorgio; Buscemi, Silvio; Drago, Filippo; Veronesi, Umberto; Scuderi, Alessandro

2013-01-01

In recent years, there has been increasing public interest in plant antioxidants, thanks to the potential anticarcinogenic and cardioprotective actions mediated by their biochemical properties. The red (or blood) orange (Citrus sinensis (L.) Osbeck) is a pigmented sweet orange variety typical of eastern Sicily (southern Italy), California, and Spain. In this paper, we discuss the main health-related properties of the red orange that include anticancer, anti-inflammatory, and cardiovascular protection activities. Moreover, the effects on health of its main constituents (namely, flavonoids, carotenoids, ascorbic acid, hydroxycinnamic acids, and anthocyanins) are described. The red orange juice demonstrates an important antioxidant activity by modulating many antioxidant enzyme systems that efficiently counteract the oxidative damage which may play an important role in the etiology of numerous diseases, such as atherosclerosis, diabetes, and cancer. The beneficial effects of this fruit may be mediated by the synergic effects of its compounds. Thus, the supply of natural antioxidant compounds through a balanced diet rich in red oranges might provide protection against oxidative damage under differing conditions and could be more effective than, the supplementation of an individual antioxidant. PMID:23738032

A Phosphine-Free Route to Size-Adjustable CdSe and CdSe/CdS Core-Shell Quantum Dots for White-Light-Emitting Diodes.

PubMed

Zhang, Yugang; Li, Guopeng; Zhang, Ting; Song, Zihang; Wang, Hui; Zhang, Zhongping; Jiang, Yang

2018-03-01

The selenium dioxide was used as the precursor to synthesize wide-size-ranged CdSe quantum dots (2.4-5.7 nm) via hot-injection route. The CdSe quantum dots are featured with high crystalline, monodisperse, zinc blende structure and wide emission region (530-635 nm). In order to improve the stability and quantum yield, a phosphine-free single-molecular precursor approach is used to obtain CdSe/CdS core/shell quantum dots. The CdSe/CdS quantum dots are highly fluorescent with quantum yield up to 65%, and persist the good monodispersity and high crystallinity. Moreover, the quantum dots white light-emitting-diodes are fabricated by using the resultant red emission core/shell quantum dots and Y3Al5O12:Ce3+ yellow phosphors as color-conversion layers on a blue InGaN chip. The prepared light-emitting-diodes show good performance with CIE-1931 coordinated of (0.3583, 0.3349), an Ra of 92.9, and a Tc of 4410 K at 20 mA, which indicate that the combination of red-emission QDs and yellow phophors as a promising approach to obtain warm WLEDs with good color rendering.

Unique photoluminescence degradation/recovery phenomena in trivalent ion-activated phosphors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sawada, Kenji; Adachi, Sadao, E-mail: adachi@el.gunma-u.ac.jp

Photo-induced luminescence intensity degradation in red-emitting Tb{sub 3}Ga{sub 5}O{sub 12}:Eu{sup 3+} (TGG:Eu{sup 3+}) phosphor is observed and studied using x-ray diffraction measurement, photoluminescence (PL) analysis, PL excitation spectroscopy, and PL decay analysis. The red-emitting TGG:Eu{sup 3+} phosphor exhibits remarkable degradation in the PL intensity under weak UV light (λ < 350 nm) exposure in the seconds time scale. The PL degradation characteristics can be well expressed by the exponential formulation with respect to exposure time. Interestingly, the PL intensity recovers after a few minutes when the phosphor is stored in a dark room or exposed to the long-wavelength (λ > 350 nm) light. The luminescence decaymore » dynamics measured by excitation at λ{sub ex} = 355 and 266 nm suggest that the present degradation/recovery processes are caused by the electron traps formed in the TGG:Eu{sup 3+} phosphor. The Tb{sup 3+} emission in TGG shows the essentially same degradation characteristics as those observed in the TGG:Eu{sup 3+} phosphor. The present luminescence degradation/recovery phenomena of the trivalent ions (4f → 4f transitions) may universally occur in various oxide phosphors such as TGG (Tb{sup 3+} emission) and CaTiO{sub 3}:Eu{sup 3+}.« less

Y 3-xMg 2AlSi 2O 12: Cex3+ phosphors - prospective for warm-white light emitting diodes

NASA Astrophysics Data System (ADS)

Katelnikovas, Arturas; Bareika, Tomas; Vitta, Pranciškus; Jüstel, Thomas; Winkler, Holger; Kareiva, Aivaras; Žukauskas, Artūras; Tamulaitis, Gintautas

2010-07-01

Y 3-xMg 2AlSi 2O 12: Cex3+ (YMASG:Ce) phosphors were synthesized by sol-gel combustion technique at different temperatures from 1400 to 1550 °C. Samples with x = 0.015, 0.03, 0.045, and 0.06 were fabricated and characterized using powder X-ray diffraction (XRD), photoluminescence spectroscopy, and fluorescence lifetime measurements in frequency domain. XRD patterns confirmed single-phase garnet crystal structure for all the samples independently of their substitutional level and annealing temperature. In respect to Y 3Al 5O 12:Ce 3+ (YAG:Ce) phosphor, which was synthesized for comparison by a different sol-gel procedure, the photoluminescence band of these garnets is red shifted, indicating a prospective for application of this novel phosphor in warm-white light emitting diodes (LEDs). The luminescence decays bi-exponentially. The main component has a characteristic decay time decreasing from 72 to of 50 ns with increasing sintering temperature and cerium content, while ˜2% of the excitation decays with a characteristic decay time of ˜8 ns.

Is Red Heavier Than Yellow Even for Blind?

PubMed

Barilari, Marco; de Heering, Adélaïde; Crollen, Virginie; Collignon, Olivier; Bottini, Roberto

2018-01-01

Across cultures and languages, people find similarities between the products of different senses in mysterious ways. By studying what is called cross-modal correspondences, cognitive psychologists discovered that lemons are fast rather than slow, boulders are sour, and red is heavier than yellow. Are these cross-modal correspondences established via sensory perception or can they be learned merely through language? We contribute to this debate by demonstrating that early blind people who lack the perceptual experience of color also think that red is heavier than yellow but to a lesser extent than sighted do.

Synthesis and luminescent properties of Tb3Al5O12:Ce3+ phosphors for warm white light emitting diodes

NASA Astrophysics Data System (ADS)

Meng, Qinghuan; Liu, Ying; Fu, Yujie; Zu, Yuangang; Zhou, Zhenbao

2018-01-01

A series of Tb3Al5O12:Ce3+ phosphors were successfully synthesized by a precipitation method. The pure Tb3Al5O12 phase was obtained in the synthesized Tb3Al5O12:Ce3+ phosphors after heat treatments at 500 °C in air for 3 h. The excitation spectra of Tb3Al5O12:Ce3+ phosphors include excitation bands corresponding to Tb3+ and Ce3+ ions. Under the excitation at 455 nm, Tb3Al5O12:Ce3+ phosphors show emission band at around 553 nm. The critical doping concentration of Ce3+ in Tb3Al5O12 is 6mol%, which shows the highest emission intensity. White light-emitting diodes were fabricated by combining InGaN-based blue light-emitting diodes with Tb3Al5O12:Ce3+ and Y3Al5O12:Ce3+ phosphors. The Tb3Al5O12:Ce3+ based white light-emitting diode shows a lower color temperature than that of Y3Al5O12:Ce3+ based white light-emitting diode. The experimental results clearly indicate that the prepared Tb3Al5O12:Ce3+ has potential applications in white light emitting diodes.

Red Mn4+-Doped Fluoride Phosphors: Why Purity Matters.

PubMed

Verstraete, Reinert; Sijbom, Heleen F; Joos, Jonas J; Korthout, Katleen; Poelman, Dirk; Detavernier, Christophe; Smet, Philippe F

2018-06-06

Traditional light sources, e.g., incandescent and fluorescent lamps, are currently being replaced by white light-emitting diodes (wLEDs) because of their improved efficiency, prolonged lifetime, and environmental friendliness. Much effort has recently been spent to the development of Mn 4+ -doped fluoride phosphors that can enhance the color gamut in displays and improve the color rendering index, luminous efficacy of the radiation, and correlated color temperature of wLEDs used for lighting. Purity, stability, and degradation of fluoride phosphors are, however, rarely discussed. Nevertheless, the typical wet chemical synthesis routes (involving hydrogen fluoride (HF)) and the large variety of possible Mn valence states often lead to impurities that drastically influence the performance and stability of these phosphors. In this article, the origins and consequences of impurities formed during synthesis and aging of K 2 SiF 6 :Mn 4+ are revealed. Both crystalline impurities such as KHF 2 and ionic impurities such as Mn 3+ are found to affect the phosphor performance. While Mn 3+ mainly influences the optical absorption behavior, KHF 2 can affect both the optical performance and chemical stability of the phosphor. Moisture leads to decomposition of KHF 2 , forming HF and amorphous hydrated potassium fluoride. As a consequence of hydrate formation, significant amounts of water can be absorbed in impure phosphor powders containing KHF 2 , facilitating the hydrolysis of [MnF 6 ] 2- complexes and affecting the optical absorption of the phosphors. Strategies are discussed to identify impurities and to achieve pure and stable phosphors with internal quantum efficiencies of more than 90%.

Direct Growth of III-Nitride Nanowire-Based Yellow Light-Emitting Diode on Amorphous Quartz Using Thin Ti Interlayer

NASA Astrophysics Data System (ADS)

Prabaswara, Aditya; Min, Jung-Wook; Zhao, Chao; Janjua, Bilal; Zhang, Daliang; Albadri, Abdulrahman M.; Alyamani, Ahmed Y.; Ng, Tien Khee; Ooi, Boon S.

2018-02-01

Consumer electronics have increasingly relied on ultra-thin glass screen due to its transparency, scalability, and cost. In particular, display technology relies on integrating light-emitting diodes with display panel as a source for backlighting. In this study, we undertook the challenge of integrating light emitters onto amorphous quartz by demonstrating the direct growth and fabrication of a III-nitride nanowire-based light-emitting diode. The proof-of-concept device exhibits a low turn-on voltage of 2.6 V, on an amorphous quartz substrate. We achieved 40% transparency across the visible wavelength while maintaining electrical conductivity by employing a TiN/Ti interlayer on quartz as a translucent conducting layer. The nanowire-on-quartz LED emits a broad linewidth spectrum of light centered at true yellow color ( 590 nm), an important wavelength bridging the green-gap in solid-state lighting technology, with significantly less strain and dislocations compared to conventional planar quantum well nitride structures. Our endeavor highlighted the feasibility of fabricating III-nitride optoelectronic device on a scalable amorphous substrate through facile growth and fabrication steps. For practical demonstration, we demonstrated tunable correlated color temperature white light, leveraging on the broadly tunable nanowire spectral characteristics across red-amber-yellow color regime.

Direct Growth of III-Nitride Nanowire-Based Yellow Light-Emitting Diode on Amorphous Quartz Using Thin Ti Interlayer.

PubMed

Prabaswara, Aditya; Min, Jung-Wook; Zhao, Chao; Janjua, Bilal; Zhang, Daliang; Albadri, Abdulrahman M; Alyamani, Ahmed Y; Ng, Tien Khee; Ooi, Boon S

2018-02-06

Consumer electronics have increasingly relied on ultra-thin glass screen due to its transparency, scalability, and cost. In particular, display technology relies on integrating light-emitting diodes with display panel as a source for backlighting. In this study, we undertook the challenge of integrating light emitters onto amorphous quartz by demonstrating the direct growth and fabrication of a III-nitride nanowire-based light-emitting diode. The proof-of-concept device exhibits a low turn-on voltage of 2.6 V, on an amorphous quartz substrate. We achieved ~ 40% transparency across the visible wavelength while maintaining electrical conductivity by employing a TiN/Ti interlayer on quartz as a translucent conducting layer. The nanowire-on-quartz LED emits a broad linewidth spectrum of light centered at true yellow color (~ 590 nm), an important wavelength bridging the green-gap in solid-state lighting technology, with significantly less strain and dislocations compared to conventional planar quantum well nitride structures. Our endeavor highlighted the feasibility of fabricating III-nitride optoelectronic device on a scalable amorphous substrate through facile growth and fabrication steps. For practical demonstration, we demonstrated tunable correlated color temperature white light, leveraging on the broadly tunable nanowire spectral characteristics across red-amber-yellow color regime.

Synthesis and luminescence properties of blue-emitting phosphor Ca12 Al14 O32 F2 :Eu2+ for white light-emitting diode.

PubMed

Chen, Wanping; Zhang, Xinzhu; Wang, Liping

2017-09-01

A blue-emitting phosphor Ca 12 Al 14 O 32 F 2 :Eu 2+ was synthesized using a high-temperature solid-state reaction under a reductive atmosphere. The X-ray diffraction measurements indicate that a pure phase Ca 12 Al 14 O 32 F 2 :Eu 2+ can be obtained for low doping concentration of Eu 2+ . The phosphor has a strong absorption in the range 270-420 nm with a maximum at ~340 nm and blue emission in the range 400-500 nm with chromatic coordination of (0.152, 0.045). The optimal doping concentration is ~0.24. In addition, the luminescence properties of the as-synthesized phosphor were evaluated by comparison with those of Ca 12 Al 14 O 32 Cl 2 :Eu 2+ and the commercially available phosphor BaMgAl 10 O 17 :Eu 2+ . The emission intensity of Ca 12 Al 14 O 32 F 2 :Eu 2+ was ~72% that of BaMgAl 10 O 17 :Eu 2+ under excitation at λ = 375 nm. The results indicate that Ca 12 Al 14 O 32 F 2 :Eu 2+ has potential application as a near-UV-convertible blue phosphor for white light-emitting diodes. Copyright © 2017 John Wiley & Sons, Ltd.

Co-Precipitation Synthesis and Optical Properties of Mn4+-Doped Hexafluoroaluminate w-LED Phosphors

PubMed Central

Geitenbeek, Robin G.; Meijerink, Andries

2017-01-01

Mn4+-activated hexafluoroaluminates are promising red-emitting phosphors for white light emitting diodes (w-LEDs). Here, we report the synthesis of Na3AlF6:Mn4+, K3AlF6:Mn4+ and K2NaAlF6:Mn4+ phosphors through a simple two-step co-precipitation method. Highly monodisperse large (~20 μm) smoothed-octahedron shaped crystallites are obtained for K2NaAlF6:Mn4+. The large size, regular shape and small size distribution are favorable for application in w-LEDs. All Mn4+-doped hexafluoroaluminates show bright red Mn4+ luminescence under blue light excitation. We compare the optical properties of Na3AlF6:Mn4+, K3AlF6:Mn4+ and K2NaAlF6:Mn4+ at room temperature and 4 K. The luminescence measurements reveal that multiple Mn4+ sites exist in M3AlF6:Mn4+ (M = Na, K), which is explained by the charge compensation that is required for Mn4+ on Al3+ sites. Thermal cycling experiments show that the site distribution changes after annealing. Finally, we investigate thermal quenching and show that the luminescence quenching temperature is high, around 460–490 K, which makes these Mn4+-doped hexafluoroaluminates interesting red phosphors for w-LEDs. The new insights reported on the synthesis and optical properties of Mn4+ in the chemically and thermally stable hexafluoroaluminates can contribute to the optimization of red-emitting Mn4+ phosphors for w-LEDs. PMID:29149083

Engineered core/shell quantum dots as phosphors for solid-state lighting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klimov, Victor Ivanovich; Pietryga, Jeffrey Michael; McDaniel, Hunter

2015-01-14

Light-emitting diodes (LEDs) for solid state light ing (SSL) typically combine a blue or near- ultraviolet drive LED with one or more dow nconverting phosphors to produce “white” light. Further advances in both efficiency and wh ite-light quality will re quire new phosphors with narrow-band, highly efficient emission, particul arly in the red. A team led by principal investigator Dr. Victor Klim ov of Los Alamos National Labo ratory proposes to develop engineered semiconductor nanocrystal quantum dots (QDs) that combine optimal luminescent properties with long-term stability under ty pical downconverting conditions to enable new performance levels in SSL. The whitemore » LED phosphor industry is estimated to have sales of roughly $400 million in 2018 and would significantly benefit from the development of bright and narrow red-emitting QD phosphors because they woul d enable warmer whites without wasting energy by emission of light beyond the response of the human eye. In order to capitalize on the market opportunity, the LANL team is partnering with a local company called UbiQD that will facilitate US manufacturing.« less

Enhanced luminescence in SrMgAl(x)O(17±δ):yMn4+ composite phosphors.

PubMed

Cao, Renping; Sharafudeen, Kaniyarakkal N; Qiu, Jianrong

2014-01-03

Red-emitting SrMgAlxO17±δ:yMn(4+) composite phosphors (x=10-100; y=0.05-4.0 mol%) are synthesized by solid-state reaction method in air. Addition of Al2O3 leads to the formation of two concomitant phases, i.e., SrMgAl10O17 and Al2O3 phases in the composite phosphor. Red emission from Mn(4+) ions in the composite phosphors is greatly enhanced due to multiple scattering and absorption of excitation light between SrMgAl10O17 and Al2O3 phases. SrMgAlxO17±δ:yMn(4+) composite phosphors would be a promising candidate as red phosphor in the application of a 397 nm near UV-based W-LED. Copyright © 2013 Elsevier B.V. All rights reserved.

When red lights look yellow.

PubMed

Wood, Joanne M; Atchison, David A; Chaparro, Alex

2005-11-01

Red signals are typically used to signify danger. This study was conducted to investigate a situation identified by train drivers in which red signals appear yellow when viewed at long distances (approximately 900 m) through progressive-addition lenses. A laboratory study was conducted to investigate the effects of defocus, target size, ambient illumination, and surround characteristics on the extent of the color misperception of train signals by nine visually normal participants. The data from the laboratory study were validated in a field study by measuring the amounts of defocus and the distances at which the misperception of the color of train signals was apparent and whether these distances varied as a function of time of day. The laboratory study demonstrated that small red targets (approximately 1 min arc) can appear yellow when viewed through small amounts of defocus (approximately +0.75 D) under bright illumination (1910 cd/m(2)). In the field study, the defocus needed to produce the color misperception was similar to that found in the laboratory study. Time of day affected the color misperception, and there was no misperception at night. The color misperception is not solely associated with progressive-addition lenses, but occurs in the presence of small amounts of positive defocus. The potential for the misperception to result in collisions and fatalities presents a major safety concern.

Comparative analysis of pigments in red and yellow banana fruit.

PubMed

Fu, Xiumin; Cheng, Sihua; Liao, Yinyin; Huang, Bingzhi; Du, Bing; Zeng, Wei; Jiang, Yueming; Duan, Xuewu; Yang, Ziyin

2018-01-15

Color is an important characteristic determining the fruit value. Although ripe bananas usually have yellow peels, several banana cultivars have red peels. As details of the pigments in banana fruits are unknown, we investigated these pigments contents and compositions in the peel and pulp of red cultivar 'Hongjiaowang' and yellow cultivar 'Baxijiao' by UPLC-PDA-QTOF-MS and HPLC-PDA techniques. The 'Hongjiaowang' peel color was mainly determined by the presence of anthocyanin-containing epidermal cells. Rutinoside derivatives of cyanidin, peonidin, petunidin, and malvidin were unique to the red peel, and possibly responsible for the red color. 'Hongjiaowang' contained higher total content of carotenoids than 'Baxijiao' in both pulp and peel. Lutein, α-carotene, and β-carotene were main carotenoids, which might play a more important role than flavonoids in producing the yellow banana color owing to the properties and distribution in the fruit. The information will help us understand a complete profile of pigments in banana. Copyright © 2017 Elsevier Ltd. All rights reserved.

Optical enhancement of phosphor-converted wLEDs using glass beads

NASA Astrophysics Data System (ADS)

Güner, Tuğrul; Şentürk, Ufuk; Demir, Mustafa M.

2017-10-01

YAG:Ce3+ is a yellow-source compound commonly used in phosphor conversion layers for direct coating or remote phosphor configurations in LED illumination. This material, however, suffers from a high correlated color temperature, and low color-rendering index due to its deficiency in the red spectrum. In this study, glass beads (GB) with an average particle diameter of 10 μm were introduced to the conversion layer of a YAG:Ce3+ particulate-filled polydimethylsiloxane matrix composite structure and found to improve the optical features of the resulting composite.

Antihyperglucolipidaemic and anticarbonyl stress properties in green, yellow and red sweet bell peppers (Capsicum annuum L.).

PubMed

Shukla, Srishti; Kumar, Dommati Anand; Anusha, Sanga Venkata; Tiwari, Ashok Kumar

2016-01-01

Effect of aqueous methanol extract of different colour sweet bell peppers (Capsicum annuum L.) on parameters of diabesity and carbonyl stress was analysed in vitro. Yellow pepper displayed significantly (p < 0.001) higher intestinal α-glucosidase inhibitory activity than green and red pepper. Porcine pancreatic lipase inhibitory activity was significantly (p < 0.01) high in yellow and red pepper than in green pepper. Green and red pepper inhibited vesperlysine-type advanced glycation end products (AGEs) more potently than yellow pepper; however, pentosidine-type AGEs were similarly inhibited by all three peppers. Yellow and red pepper inhibited lipid peroxidation more potently (p < 0.01) than green pepper. Total polyphenol content and free radicals scavenging activities in yellow and red bell peppers were higher than in green pepper. Total flavonoid content was high in green pepper than that present in yellow and red peppers. Green pepper displayed presence of proanthocyanins; however, oligomeric anthocyanins were detected in yellow and red peppers.

Infrared spectroscopy and upconversion luminescence behaviour of erbium doped yttrium (III) oxide phosphor

NASA Astrophysics Data System (ADS)

Dubey, Vikas; Tiwari, Ratnesh; Tamrakar, Raunak Kumar; Rathore, Gajendra Singh; Sharma, Chitrakant; Tiwari, Neha

2014-11-01

The paper reports upconversion luminescence behaviour and infra-red spectroscopic pattern of erbium doped yttrium (III) oxide phosphor. Sample was synthesized by solid state reaction method with variable concentration or erbium (0.5-2.5 mol%). The conventional solid state method is suitable for large scale production and eco-friendly method. The prepared sample was characterized by X-ray diffraction (XRD) technique. From structural analysis by XRD technique shows cubic structure of prepared sample with variable concentration of erbium and no impurity phase were found when increase the concentration of Er3+. Particle size was calculated by Scherer's formula and it varies from 67 nm to 120 nm. The surface morphology of prepared phosphor was determined by field emission gun scanning electron microscopy (FEGSEM) technique. The surface morphology of the sample shows good connectivity with grains as well as some agglomerates formation occurs in sample. The functional group analysis was done by Fourier transform infra-red technique (FTIR) analysis which confirm the formation of Y2O3:Er3+ phosphor was prepared. The results indicated that the Y2O3:Er3+ phosphors might have high upconversion efficiency because of their low vibrational energy. Under 980 nm laser excitation sample shows intense green emission at 555 nm and orange emission at 590 nm wavelength. For green emission transition occurs 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 for upconversion emissions. Excited state absorption and energy transfer process were discussed as possible upconversion mechanisms. The near infrared luminescence spectra was recorded. The upconversion luminescence intensity increase with increasing the concentration or erbium up to 2 mol% after that luminescence intensity decreases due to concentration quenching occurs. Spectrophotometric determinations of peaks are evaluated by Commission Internationale de I'Eclairage (CIE) technique. From CIE technique the dominant peak of from PL spectra shows

Synthesis and luminescence characterization of Pr3+ doped Sr1.5Ca0.5SiO4 phosphor

NASA Astrophysics Data System (ADS)

Vidyadharan, Viji; Mani, Kamal P.; Sajna, M. S.; Joseph, Cyriac; Unnikrishnan, N. V.; Biju, P. R.

2014-12-01

Luminescence properties of Pr3+ activated Sr1.5Ca0.5SiO4 phosphors synthesized by solid state reaction method are reported in this work. Blue, orange red and red emissions were observed in the Pr3+ doped sample under 444 nm excitation and these emissions are assigned as 3P0 → 3H4, 3P0 → 3H6 and 3P0 → 3F4 transitions. The emission intensity shows a maximum corresponding to the 0.5 wt% Pr3+ ion. The decay analysis was done for 0.05 and 0.5 wt% Pr3+ doped samples for the transition 3P0 → 3H6. The life times of 0.05 and 0.5 wt% Pr3+ doped samples were calculated by fitting to exponential and non-exponential curve respectively, and are found to be 156 and 105 μs respectively. The non-exponential behaviour arises due to the statistical distribution of the distances between the ground state Pr3+ ions and excited state Pr3+ ions, which cause the inhomogeneous energy transfer rate. The XRD spectrum confirmed the triclinic phase of the prepared phosphors. The compositions of the samples were determined by the energy dispersive X-ray spectra. From the SEM images it is observed that the particles are agglomerated and are irregularly shaped. IR absorption bands were assigned to different vibrational modes. The well resolved peaks shown in the absorption spectra are identical to the excitation spectra of the phosphor samples. Pr3+ activated Sr1.5Ca0.5SiO4 phosphors can be efficiently excited with 444 nm irradiation and emit multicolour visible emissions. From the CIE diagram it can be seen that the prepared phosphor samples give yellowish-green emission.

Yellow to orange-reddish glass phosphors: Sm3+, Tb3+ and Sm3+/Tb3+ in zinc tellurite-germanate glasses

NASA Astrophysics Data System (ADS)

Alvarez-Ramos, M. E.; Alvarado-Rivera, J.; Zayas, Ma. E.; Caldiño, U.; Hernández-Paredes, J.

2018-01-01

An optical spectroscopy analysis of TeO-GeO2-ZnO glass co-activating Sm3+/Tb3+ ions was carried out through Raman, photoluminescence spectra and decay time profiles as a function of Sm3+ concentration. According to the estimated CIE1931 chromaticity coordinates, the color of the emission can be adjusted from the yellow light region (0.4883, 0.4774), towards the reddish light region (0.5194,0.4144) by increasing the Sm3+ content from 1, 3, 5% mol, co-doped with 1% mol Tb3+ under co-excitation of Sm3+ and Tb3+ at 378 nm. The color temperatures are in the range of 1379-2804 K. Such photoluminescence is generated by the 4G 5/2 → 4H 5/2, 4H 7/2, 4H9/2 emissions of Sm3+ in addition to the 5D4→7F6,5,4,3 emissions of Tb3+; the single doped Sm3+ glass displayed an intense orange light. Meanwhile, co-doped Sm3+/Tb3+ glasses excited at 378 nm showed a significant reduction in Tb3+ emission, with a simultaneous increment in the reddish-orange emission of Sm3+, due to a non-radiative resonant energy transfer from Tb3+ to Sm3+. Decay time profile analysis of the Tb3+ emission as function of Sm3+ ion content suggests that an electric dipole-dipole interaction into Tb3+-Sm3+ clusters might dominate in the energy transfer process, with an efficiency and probability of 0.22, 0.27, 0.38 and 122.8, 327.6, 522.7 s-1, respectively.

Energy transfer and color tunable emission in Tb3+,Eu3+ co-doped Sr3LaNa(PO4)3F phosphors.

PubMed

Li, Shuo; Guo, Ning; Liang, Qimeng; Ding, Yu; Zhou, Huitao; Ouyang, Ruizhuo; Lü, Wei

2018-02-05

A group of color tunable Sr 3 LaNa(PO 4 ) 3 F:Tb 3+ ,Eu 3+ phosphors were prepared by conventional high temperature solid state method. The phase structures, luminescence properties, fluorescence lifetimes and energy transfer were investigated in detail. Under 369nm excitation, owing to efficient energy transfer of Tb 3+ →Eu 3+ , the emission spectra both have green emission of Tb 3+ and red emission of Eu 3+ . An efficient energy transfer occur in Tb 3+ , Eu 3+ co-doped Sr 3 LaNa(PO 4 ) 3 F phosphors. The most possible mechanism of energy transfer is dipole-dipole interaction by Dexter's theoretical model. The energy transfer of Tb 3+ and Eu 3+ was confirmed by the variations of emission and excitation spectra and Tb 3+ /Eu 3+ decay lifetimes in Sr 3 LaNa(PO 4 ) 3 F:Tb 3+ ,Eu 3+ . The color tone can tuned from yellowish-green through yellow and eventually to reddish-orange with fixed Tb 3+ content by changing Eu 3+ concentrations. The results show that the prepared Tb 3+ , Eu 3+ co-doped color tunable Sr 3 LaNa(PO 4 ) 3 F phosphor can be used for white LED. Copyright © 2017 Elsevier B.V. All rights reserved.

Energy transfer and color tunable emission in Tb3 +,Eu3 + co-doped Sr3LaNa(PO4)3F phosphors

NASA Astrophysics Data System (ADS)

Li, Shuo; Guo, Ning; Liang, Qimeng; Ding, Yu; Zhou, Huitao; Ouyang, Ruizhuo; Lü, Wei

2018-02-01

A group of color tunable Sr3LaNa(PO4)3F:Tb3 +,Eu3 + phosphors were prepared by conventional high temperature solid state method. The phase structures, luminescence properties, fluorescence lifetimes and energy transfer were investigated in detail. Under 369 nm excitation, owing to efficient energy transfer of Tb3 + → Eu3 +, the emission spectra both have green emission of Tb3 + and red emission of Eu3 +. An efficient energy transfer occur in Tb3 +, Eu3 + co-doped Sr3LaNa(PO4)3F phosphors. The most possible mechanism of energy transfer is dipole-dipole interaction by Dexter's theoretical model. The energy transfer of Tb3 + and Eu3 + was confirmed by the variations of emission and excitation spectra and Tb3 +/Eu3 + decay lifetimes in Sr3LaNa(PO4)3F:Tb3 +,Eu3 +. The color tone can tuned from yellowish-green through yellow and eventually to reddish-orange with fixed Tb3 + content by changing Eu3 + concentrations. The results show that the prepared Tb3 +, Eu3 + co-doped color tunable Sr3LaNa(PO4)3F phosphor can be used for white LED.

Exciplex-Forming Co-Host-Based Red Phosphorescent Organic Light-Emitting Diodes with Long Operational Stability and High Efficiency.

PubMed

Lee, Jeong-Hwan; Shin, Hyun; Kim, Jae-Min; Kim, Kwon-Hyeon; Kim, Jang-Joo

2017-02-01

The use of exciplex forming cohosts and phosphors incredibly boosts the efficiency of organic light-emitting diodes (OLEDs) by providing a barrier-free charge injection into an emitting layer and a broad recombination zone. However, most of the efficient OLEDs based on the exciplex forming cohosts has suffered from the short operational lifetime. Here, we demonstrated phosphorescent OLEDs (PhOLEDs) having both high efficiency and long lifetime by using a new exciplex forming cohost composed of N,N'-diphenyl-N,N'-bis(1,1'-biphenyl)-4,4'-diamine (NPB) and (1,3,5-triazine-2,4,6-triyl)tris(benzene-3,1-diyl))tris(diphenylphosphine oxide) (PO-T2T). The red-emitting PhOLEDs using the exciplex forming cohost achieved a maximum external quantum efficiency (EQE) of 34.1% and power efficiency of 62.2 lm W 1- with low operating voltages and low efficiency roll-offs. More importantly, the device demonstrated a long lifetime around 2249 h from 1000 cd m -2 to 900 cd m -2 (LT 90 ) under a continuous flow of constant current. The efficiencies of the devices are the highest for red OLEDs with an LT 90 > 1000 h.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chu, Yaoqing; School of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai 201418; Zhang, Qinghong

A new silicate garnet phosphor, Lu{sub 2−x}CaMg{sub 2}Si{sub 2.9}Ti{sub 0.1}O{sub 12}:xCe was synthesized by a high temperature solid-state reaction under reductive atmosphere. X-ray diffraction (XRD) showed that the powder was pure garnet phase. The emission and excitation spectrum indicated that the Lu{sub 2−x}CaMg{sub 2}Si{sub 2.9}Ti{sub 0.1}O{sub 12}:xCe phosphors could absorb blue light in the spectral range of 400–550 nm efficiently and exhibit bright yellow–orange emission in the range of 520–750 nm. With the increase of Ce{sup 3+} concentration, the emission band of Ce{sup 3+} showed a red shift. Interestingly, the concentration quenching occurred when the Ce{sup 3+} concentration exceeded 4more » mol%. The temperature-dependent luminescent properties of the phosphors were discussed and the Lu{sub 1.96}CaMg{sub 2}Si{sub 2.9}Ti{sub 0.1}O{sub 12}:0.04Ce phosphors showed good performances in color temperature (2430 K) and potential applications for warm white LEDs. - Graphical Abstract: This image shows that the phosphor of Lu{sub 1.96}CaMg{sub 2}Si{sub 2.9}Ti{sub 0.1}O{sub 12}:0.04Ce can generate a uniform yellow tint under natural light illumination and emit orange–red light when excited by blue light. With a fixed 467 nm emission light, warm white light can be produced by this phosphor, which indicates that the phosphor is potentially applicable in warm white light emitting diodes based on GaN chips. - Highlights: • A new silicate garnet phosphor was synthesized by solid-state method. • Secondary phases can be avoided when a small amount of Si{sup 4+} were replaced by Ti{sup 4+}. • A broad emission band of Ce{sup 3+} in the phosphors was described. • The phosphors are potentially applicable in warm white light emitting diodes.« less

A bright cyan-excitable orange fluorescent protein facilitates dual-emission microscopy and enhances bioluminescence imaging in vivo

PubMed Central

Chu, Jun; Oh, Young-Hee; Sens, Alex; Ataie, Niloufar; Dana, Hod; Macklin, John J.; Laviv, Tal; Welf, Erik S.; Dean, Kevin M.; Zhang, Feijie; Kim, Benjamin B.; Tang, Clement Tran; Hu, Michelle; Baird, Michelle A.; Davidson, Michael W.; Kay, Mark A.; Fiolka, Reto; Yasuda, Ryohei; Kim, Douglas S.; Ng, Ho-Leung; Lin, Michael Z.

2016-01-01

Orange-red fluorescent proteins (FPs) are widely used in biomedical research for multiplexed epifluorescence microscopy with GFP-based probes, but their different excitation requirements make multiplexing with new advanced microscopy methods difficult. Separately, orange-red FPs are useful for deep-tissue imaging in mammals due to the relative tissue transmissibility of orange-red light, but their dependence on illumination limits their sensitivity as reporters in deep tissues. Here we describe CyOFP1, a bright engineered orange-red FP that is excitable by cyan light. We show that CyOFP1 enables single-excitation multiplexed imaging with GFP-based probes in single-photon and two-photon microscopy, including time-lapse imaging in light-sheet systems. CyOFP1 also serves as an efficient acceptor for resonance energy transfer from the highly catalytic blue-emitting luciferase NanoLuc. An optimized fusion of CyOFP1 and NanoLuc, called Antares, functions as a highly sensitive bioluminescent reporter in vivo, producing substantially brighter signals from deep tissues than firefly luciferase and other bioluminescent proteins. PMID:27240196

Internal photoluminescence in ZnSe homoepitaxy and application in blue green orange mixed-color light-emitting diodes

NASA Astrophysics Data System (ADS)

Wenisch, H.; Fehrer, M.; Klude, M.; Ohkawa, K.; Hommel, D.

2000-06-01

We discuss the controllable color-range in ZnSe-based light-emitting diodes (LEDs) realized by ZnSe homoepitaxy and internal photoluminescence. ZnSe-based LED structures were grown by molecular-beam epitaxy (MBE) on mostly conductive ZnSe substrates, which exhibit under short wavelength light excitation at room temperature strong orange emission around 600 nm. This fact is exploited to fabricate integrated mixed-color LED chips, where light from the active layer sandwiched in a p-n-junction acts as internal excitation source. We named this effect recently "Internal Photoluminescence" (Wenisch et al., J. Appl. Phys. 82 (1997) 4690). It leads to electroluminescence spectra with two distinct emission peaks originated from the active layer and from the ZnSe substrate, respectively. In view of color impression, just by varying the Cd xZn 1- xSe quantum-well composition and the radiant recombination rate in the substrate by it's choice, as much as two thirds of the visible color space is covered. Under conditions, when only the substrate emission is present, Commission Internationale d'Eclairage (CIE) chromaticity coordinates for orange color LEDs of (0.54, 0.45, 0.01) for the red, green and blue color, respectively, were determined. 490-nm quantum-well-emitting LEDs were found to be best suited in reaching the technologically important balanced white emission ("White Point") and a value of (0.31, 0.39, 0.30) for the color coordinates close to it was experimentally achieved.

Red Light-Emitting Diode Based on Blue InGaN Chip with CdTe x S(1 - x) Quantum Dots

NASA Astrophysics Data System (ADS)

Wang, Rongfang; Wei, Xingming; Qin, Liqin; Luo, Zhihui; Liang, Chunjie; Tan, Guohang

2017-01-01

Thioglycolic acid-capped CdTe x S(1 - x) quantum dots (QDs) were synthesized through a one-step approach in an aqueous medium. The CdTe x S(1 - x) QDs played the role of a color conversion center. The structural and luminescent properties of the obtained CdTe x S(1 - x) QDs were investigated. The fabricated red light-emitting hybrid device with the CdTe x S(1 - x) QDs as the phosphor and a blue InGaN chip as the excitation source showed a good luminance. The Commission Internationale de L'Eclairage coordinates of the light-emitting diode (LED) at (0.66, 0.29) demonstrated a red LED. Results showed that CdTe x S(1 - x) QDs can be excited by blue or near-UV regions. This feature presents CdTe x S(1 - x) QDs with an advantage over wavelength converters for LEDs.

Origin and Luminescence of Anomalous Red-Emitting Center in Rhombohedral Ba9Lu2Si6O24:Eu(2+) Blue Phosphor.

PubMed

Liu, Yongfu; Zhang, Changhua; Cheng, Zhixuan; Zhou, Zhi; Jiang, Jun; Jiang, Haochuan

2016-09-06

We obtain a blue phosphor, Ba9Lu2Si6O24:Eu(2+) (BLS:Eu(2+)), which shows a strong emission peak at 460 nm and a weak tail from 460 to 750 nm. A 610 nm red emission is observed for the first time in this kind of rhombohedral structure material, which is much different from the same crystal structure of Ba9Sc2Si6O24:Eu(2+) and Ba9Y2Si6O24:Eu(2+). The luminescence properties and decays from 10 to 550 K are discussed. The new red emission arises from a trapped exciton state of Eu(2+) at the Ba site with a larger coordination number (12-fold). It exhibits abnormal luminescence properties with a broad bandwidth and a large Stokes shift. Under the 400 nm excitation, the external quantum efficiency of BLS:Eu(2+) is 45.4%, which is higher than the 35.7% for the commercial blue phosphor BAM:Eu(2+). If the thermal stability of BLS:Eu(2+) can be improved, it will show promising applications in efficient near-UV-based white LEDs.

[The spectrogram characteristics of organic blue-emissive light-emitting excitated YAG : Ce phosphor].

PubMed

Xi, Jian-Fei; Zhang, Fang-Hui; Mu, Qiang; Zhang, Mai-Li

2011-09-01

It is demonstrated that the panchromatic luminescence devices with organic blue-emissive light-emitting was fabricated. This technique used down conversion, which was already popular in inorganic power LEDs to obtain white light emission. A blue OLED device with a configuration of ITO/2T-NATA (30 nm)/AND : TBPe (50 Wt%, 40 nm)/Alq3 (100 nm)/LiF(1 nm)/Al(100 nm) was prepared via vacuum deposition process, and then coated with YAG : Ce phosphor layers of different thicknesses to obtain a controllable and uniform shape while the CIE coordinates were fine tuned. This development not only decreased steps of technics and degree of difficulty, but also applied the mature technology of phosphor. The results showed that steady spectrogram was obtained in the devices with phosphor, with a best performance of a maximum luminance of 13 840 cd x m(-2) which was about 2 times of that of the devices without phosphor; a maximum current efficiency of 17.3 cd x A(-1) was increased more two times more than the devices without phosphor. The emission spectrum could be adjusted by varying the concentration and thickness of the phosphor layers. Absoulte spectrogram of devices was in direct proportion with different driving current corresponding.

Purely Organic Thermally Activated Delayed Fluorescence Materials for Organic Light-Emitting Diodes.

PubMed

Wong, Michael Y; Zysman-Colman, Eli

2017-06-01

The design of thermally activated delayed fluorescence (TADF) materials both as emitters and as hosts is an exploding area of research. The replacement of phosphorescent metal complexes with inexpensive organic compounds in electroluminescent (EL) devices that demonstrate comparable performance metrics is paradigm shifting, as these new materials offer the possibility of developing low-cost lighting and displays. Here, a comprehensive review of TADF materials is presented, with a focus on linking their optoelectronic behavior with the performance of the organic light-emitting diode (OLED) and related EL devices. TADF emitters are cross-compared within specific color ranges, with a focus on blue, green-yellow, orange-red, and white OLEDs. Organic small-molecule, dendrimer, polymer, and exciplex emitters are all discussed within this review, as is their use as host materials. Correlations are provided between the structure of the TADF materials and their optoelectronic properties. The success of TADF materials has ushered in the next generation of OLEDs. © 2017 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Protective effect of red orange extract supplementation against UV-induced skin damages: photoaging and solar lentigines.

PubMed

Puglia, Carmelo; Offerta, Alessia; Saija, Antonella; Trombetta, Domenico; Venera, Cardile

2014-06-01

Exposure of the skin to solar ultraviolet (UV) radiations causes important oxidative damages that result in clinical and hystopathological changes, contributing to premature skin aging. Hyperpigmented lesions, also known as age spots, are one of the most visible alterations in skin photoaging. Skin is naturally equipped with antioxidant systems against UV-induced ROS generation; however, these antioxidant defenses are not completely efficient during exposure to sunlight. Oral antioxidants are able to counteract the harmful effects of UV radiation and to strengthen the physiological skin antioxidant defenses. The present study was performed to evaluate the in vivo skin photo-protecting and anti-aging effects of a red orange (Citrus sinensis varieties Moro, Tarocco and Sanguinello) extract supplementation. Previous studies showed that red orange extracts possess strong in vitro free radical scavenging/antioxidant activity and photo-protective effects on human skin. The photo-protective effects of red orange extract intake against UV-induced skin erythema and melanin production in solar lentigo was evaluated on healthy volunteers by an objective instrumental method (reflectance spectrophotometry). Data obtained from in vivo studies showed that supplementation of red orange extract (100 mg/daily) for 15 days brought a significant reduction in the UV-induced skin erythema degree. Moreover, skin age spots pigmentation (melanin content) decreased from 27% to 7% when subjects were exposed to solar lamp during red orange extract supplementation. Red orange extract intake can strengthen physiological antioxidant skin defenses, protecting skin from the damaging processes involved in photo-aging and leading to an improvement in skin appearance and pigmentation. © 2014 Wiley Periodicals, Inc.

Luminescence properties of Ca2 Ga2 SiO7 :RE phosphors for UV white-light-emitting diodes.

PubMed

Jiao, Mengmeng; Lv, Wenzhen; Lü, Wei; Zhao, Qi; Shao, Baiqi; You, Hongpeng

2015-03-16

A series of Eu(2+) -, Ce(3+) -, and Tb(3+) -doped Ca2 Ga2 SiO7 phosphors is synthesized by using a high-temperature solid-state reaction. The powder X-ray diffraction and structure refinement data indicate that our prepared phosphors are single phased and the phosphor crystalizes in a tetrahedral system with the ${P\\bar 42m}$ (113) space group. The Eu(2+) - and Ce(3+) -doped phosphors both have broad excitation bands, which match well with the UV light-emitting diodes chips. Under irradiation of λ=350 nm, Ca2 Ga2 SiO7 :Eu(2+) and Ca2 Ga2 SiO7 :Ce(3+) , Li(+) have green and blue emissions, respectively. Luminescence of Ca2 Ga2 SiO7 :Tb(3+) , Li(+) phosphor varies with the different Tb(3+) contents. The thermal stability and energy-migration mechanism of Ca2 Ga2 SiO7 :Eu(2+) are also studied. The investigation results indicate that the prepared Ca2 Ga2 SiO7 :Eu(2+) and Ca2 Ga2 SiO7 :Ce(3+) , Li(+) samples show potential as green and blue phosphors, respectively, for UV-excited white-light-emitting diodes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Phosphor-free nanopyramid white light-emitting diodes grown on (101{sup ¯}1) planes using nanospherical-lens photolithography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Kui; Department of Electronic Engineering, Tsinghua National Laboratory for Information Science and Technology/State Key Lab on Integrated Optoelectronics, Tsinghua University, Beijing 100084; Wei, Tongbo, E-mail: tbwei@semi.ac.cn

2013-12-09

We reported a high-efficiency and low-cost nano-pattern method, the nanospherical-lens photolithography technique, to fabricate a SiO{sub 2} mask for selective area growth. By controlling the selective growth, we got a highly ordered hexagonal nanopyramid light emitting diodes with InGaN/GaN quantum wells grown on nanofacets, demonstrating an electrically driven phosphor-free white light emission. We found that both the quantum well width and indium incorporation increased linearly along the (101{sup ¯}1) planes towards the substrate and the perpendicular direction to the (101{sup ¯}1) planes as well. Such spatial distribution was responsible for the broadband emission. Moreover, using cathodoluminescence techniques, it was foundmore » that the blue emission originated from nanopyramid top, resembling the quantum dots, green emission from the InGaN quantum wells layer at the middle of sidewalls, and yellow emission mainly from the bottom of nanopyramid ridges, similar to the quantum wires.« less

The Enhanced Red Emission and Improved Thermal Stability of CaAlSiN3:Eu2+ Phosphors by Using Nano-EuB6 as Raw Material

PubMed Central

Liu, Wen-Quan; Wu, Dan; Chang, Hugejile; Duan, Ru-Xia; Wu, Wen-Jie; Amu, Guleng; Bao, Fu-Quan; Tegus, Ojiyed

2018-01-01

Synthesizing phosphors with high performance is still a necessary work for phosphor-converted white light-emitting diodes (W-LEDs). In this paper, three series of CaAlSiN3:Eu2+ (denoted as CASN:Eu2+) phosphors using Eu2O3, EuN and EuB6 as raw materials respectively are fabricated by under the alloy precursor normal pressure nitridation synthesis condition. We demonstrate that CASN:Eu2+ using nano-EuB6 as raw material shows higher emission intensity than others, which is ascribed to the increment of Eu2+ ionic content entering into the crystal lattice. An improved thermal stability can also be obtained by using nano-EuB6 due to the structurally stable status, which is assigned to the partial substitution of Eu–O (Eu–N) bonds by more covalent Eu–B ones that leads to a higher structural rigidity. In addition, the W-LEDs lamp was fabricated to explore its possible application in W-LEDs based on blue LEDs. Our results indicate that using EuB6 as raw materials can provide an effective way of enhancing the red emission and improving the thermal stability of the CASN:Eu2+ red phosphor. PMID:29370148

Luminescence properties of Ca{sub 3}Ti{sub 2}O{sub 7}:Eu{sup 3+}, Bi{sup 3+}, R{sup +} (R{sup +}=Li{sup +}, Na{sup +}, and K{sup +}) red emission phosphor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Renping, E-mail: jxcrp@163.com; Chen, Guo; Yu, Xiaoguang

2014-12-15

A series of Ca{sub 3}Ti{sub 2}O{sub 7}:Eu{sup 3+}, Ca{sub 3}Ti{sub 2}O{sub 7}:Eu{sup 3+}, Bi{sup 3+}, Ca{sub 3}Ti{sub 2}O{sub 7}:Eu{sup 3+}, R{sup +}, and Ca{sub 3}Ti{sub 2}O{sub 7}:Eu{sup 3+}, Bi{sup 3+}, R{sup +} (R{sup +}=Li{sup +}, Na{sup +}, and K{sup +}) phosphors are synthesized by solid-state reaction method in air. All phosphors show bright red emissions centered at ∼617 nm upon excitation with UV light of 397 nm. Bi{sup 3+} is a sensitizer for the luminescence of Eu{sup 3+}, and can improve significantly the PL intensity of Ca{sub 3}Ti{sub 2}O{sub 7}:Eu{sup 3+} phosphor due to energy transfer between Bi{sup 3+} andmore » Eu{sup 3+} ions. The sensitization mechanism is investigated and discussed by energy level diagrams of Bi{sup 3+} and Eu{sup 3+} ions. R{sup +} ion is used as the charge compensator to improve the luminescence intensity of Ca{sub 3}Ti{sub 2}O{sub 7}:Eu{sup 3+} and Ca{sub 3}Ti{sub 2}O{sub 7}:Eu{sup 3+}, Bi{sup 3+} phosphors, and their PL intensities are enhanced in the sequence K{sup +}→Na{sup +}→Li{sup +}. These phosphors can be promising red emitting candidate for white LED with a ∼397 nm near UV chip excitation owing to the high brightness. - Graphical abstract: Energy transfer and charge compensation can enhance PL intensity of phosphors obviously. - Highlights: • Ca{sub 3}Ti{sub 2}O{sub 7}:Eu{sup 3+}, Bi{sup 3+} phosphor is synthesized. • Energy transfer between Eu{sup 3+} and Bi{sup 3+} ions benefit PL intensity of Ca{sub 3}Ti{sub 2}O{sub 7}:Eu{sup 3+}, Bi{sup 3+} phosphor. • Alkaline metal ions can further improve the PL intensity of Ca{sub 3}Ti{sub 2}O{sub 7}:Eu{sup 3+}, Bi{sup 3+} phosphor. • Ca{sub 3}Ti{sub 2}O{sub 7}:Eu{sup 3+}, Bi{sup 3+}, R{sup +} phosphor may be promising red emitting candidate for white LED.« less

White light emission and effect of annealing on the Ho{sup 3+}–Yb{sup 3+} codoped BaCa{sub 2}Al{sub 8}O{sub 15} phosphor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumari, Astha; Rai, Vineet Kumar, E-mail: vineetkrrai@yahoo.co.in

Graphical abstract: The upconversion emission spectra of the Ho{sup 3+}/Yb{sup 3+} doped/codoped BaCa{sub 2}Al{sub 8}O{sub 15} phosphors with different doping concentrations of Ho{sup 3+}/Yb{sup 3+} ions along with UC emission spectrum of the white light emitting phosphor annealed at 800 °C. - Highlights: • BaCa{sub 2}Al{sub 8}O{sub 15} phosphors codoped with Ho{sup 3+}–Yb{sup 3+} have been prepared by combustion method. • Phosphor annealed at 800 °C, illuminate an intense white light upon NIR excitation. • The sample annealed at higher temperatures emits in the pure green region. • The colour emitted persists in the white region even at high pumpmore » power density. • Developed phosphor is suitable for making upconverters and WLEDs. - Abstract: The BaCa{sub 2}Al{sub 8}O{sub 15} (BCAO) phosphors codoped with suitable Ho{sup 3+}–Yb{sup 3+} dopant concentration prepared by combustion method illuminate an intense white light upon near infrared diode laser excitation. The structural analysis of the phosphors and the detection of impurity contents have been performed by using the X-Ray Diffraction, FESEM and FTIR analysis. The purity of white light emitted from the sample has been confirmed by the CIE chromaticity diagram. Also, the white light emitted from the sample persists with the variation of pump power density. The phosphors emit upconversion (UC) emission bands in the blue, green and red region (three primary colours required for white light emission) along with one more band in the near infrared region of the electromagnetic spectrum. On annealing the white light emitting sample at higher temperatures, the sample starts to emit green colour and also the intensity of green and red UC emission bands get enhanced largely.« less

Sol–gel synthesis, structure and luminescence properties of Ba{sub 2}ZnMoO{sub 6}:Eu{sup 3+} phosphors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Yuntong; Liu, Xiaohua, E-mail: xhliuxhliu@tom.com

2015-04-15

Graphical abstract: The phosphor powders of Ba{sub 2}ZnMoO{sub 6}:Eu{sup 3+} were prepared by sol–gel method. The dependence of luminescence intensity on the Eu{sup 3+} concentration was investigated. - Highlights: • We synthesize Ba{sub 2}ZnMoO{sub 6}:Eu{sup 3+} phosphors by the sol–gel method. • The effect of temperature on the crystallinity and morphology is investigated. • The phosphor presents an intense CT band in near UV range (370–410 nm). • The concentration quenching mechanism is the exchange interaction. - Abstract: Double-perovskite Ba{sub 2}Zn{sub 1−x}MoO{sub 6}:xEu{sup 3+} (x = 0, 0.02, 0.04, 0.06, 0.08, 0.1) orange–red emitting phosphors were synthesized by using themore » sol–gel method. The crystalline structure and photoluminescence properties of the phosphors were investigated. The X-ray diffraction (XRD) patterns indicate that the structure of matrix Ba{sub 2}ZnMoO{sub 6} is cubic double-perovskite with space group Fm-3m. The Ba{sub 2}ZnMoO{sub 6}:Eu{sup 3+} phosphors present an intense broad charge transfer (CT) band absorption in near UV range (370–410 nm), which attributes to the charge transfer state of MoO{sub 6}, and performs orange–red emission of Eu{sup 3+} ({sup 5}D{sub 0} → {sup 7}F{sub 1} transition) at around 596 nm. A low concentration quenching occurs in Ba{sub 2}ZnMoO{sub 6}:Eu{sup 3+} and the optimal doping concentration is about 6 mol%. The Ba{sub 2}ZnMoO{sub 6}:Eu{sup 3+} phosphors are considered to be a promising orange–red emitting phosphor for near ultraviolet GaN-based white light emitting diode.« less

Synthesis of Sr2Si5N8:Ce3+ phosphors for white LEDs via an efficient chemical deposition

PubMed Central

Yang, Che-Yuan; Som, Sudipta; Das, Subrata; Lu, Chung-Hsin

2017-01-01

Novel chemical vapor deposition (CVD) process was successfully developed for the growth of Sr2Si5N8:Ce3+ phosphors with elevated luminescent properties. Metallic strontium was used as a vapor source for producing Sr3N2 vapor to react with Si3N4 powder via a homogeneous gas-solid reaction. The phosphors prepared via the CVD process showed high crystallinity, homogeneous particle size ranging from 8 to 10 μm, and high luminescence properties. In contrast, the phosphors prepared via the conventional solid-state reaction process exhibited relative low crystallinity, non-uniform particle size in the range of 0.5–5 μm and relatively lower luminescent properties than the phosphors synthesized via the CVD process. Upon the blue light excitation, Sr2−xCexSi5N8 phosphors exhibited a broad yellow band. A red shift of the emission band from 535 to 556 nm was observed with the increment in the doping amount of Ce3+ ions from x = 0.02 to x = 0.10. The maximum emission was observed at x = 0.06, and the external and internal quantum efficiencies were calculated to be 51% and 71%, respectively. Furthermore, the CVD derived optimum Sr1.94Ce0.06Si5N8 phosphor exhibited sufficient thermal stability for blue-LEDs and the activation energy was calculated to be 0.33 eV. The results demonstrate a potential synthesis process for nitride phosphors suitable for light emitting diodes. PMID:28361999

Synthesis of Sr2Si5N8:Ce3+ phosphors for white LEDs via an efficient chemical deposition

NASA Astrophysics Data System (ADS)

Yang, Che-Yuan; Som, Sudipta; Das, Subrata; Lu, Chung-Hsin

2017-03-01

Novel chemical vapor deposition (CVD) process was successfully developed for the growth of Sr2Si5N8:Ce3+ phosphors with elevated luminescent properties. Metallic strontium was used as a vapor source for producing Sr3N2 vapor to react with Si3N4 powder via a homogeneous gas-solid reaction. The phosphors prepared via the CVD process showed high crystallinity, homogeneous particle size ranging from 8 to 10 μm, and high luminescence properties. In contrast, the phosphors prepared via the conventional solid-state reaction process exhibited relative low crystallinity, non-uniform particle size in the range of 0.5-5 μm and relatively lower luminescent properties than the phosphors synthesized via the CVD process. Upon the blue light excitation, Sr2-xCexSi5N8 phosphors exhibited a broad yellow band. A red shift of the emission band from 535 to 556 nm was observed with the increment in the doping amount of Ce3+ ions from x = 0.02 to x = 0.10. The maximum emission was observed at x = 0.06, and the external and internal quantum efficiencies were calculated to be 51% and 71%, respectively. Furthermore, the CVD derived optimum Sr1.94Ce0.06Si5N8 phosphor exhibited sufficient thermal stability for blue-LEDs and the activation energy was calculated to be 0.33 eV. The results demonstrate a potential synthesis process for nitride phosphors suitable for light emitting diodes.

A green-yellow emitting oxyfluoride solid solution phosphor Sr[subscript 2]Ba(AlO[subscript 4]F)[subscript 1;#8722;x](SiO[subscript 5])x:Ce[superscript 3+] for thermally stable, high color rendition solid state white lighting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denault, Kristin A.; George, Nathan C.; Paden, Sara R.

2012-10-23

A near-UV excited, oxyfluoride phosphor solid solution Sr{sub 1.975}Ce{sub 0.025}Ba(AlO{sub 4}F){sub 1-x}(SiO{sub 5}){sub x} has been developed for solid state white lighting applications. An examination of the host lattice, and the local structure around the Ce{sup 3+} activator ions through a combination of density functional theory, synchrotron X-ray and neutron powder diffraction and total scattering, and electron paramagnetic resonance, points to how chemical substitutions play a crucial role in tuning the optical properties of the phosphor. The maximum emission wavelength can be tuned from green ({lambda}{sub em} = 523 nm) to yellow ({lambda}{sub em} = 552 nm) by tuning themore » composition, x. Photoluminescent quantum yield is determined to be 70 {+-} 5% for some of the examples in the series. Excellent thermal properties were found for the x = 0.5 sample, with the photoluminescence intensity at 160 C only decreased to 82% of its room temperature value. Phosphor-converted LED devices fabricated using an InGaN LED ({lambda}{sub max} = 400 nm) exhibit high color rendering white light with R{sub a} = 70 and a correlated color temperature near 7000 K. The value of R{sub a} could be raised to 90 by the addition of a red component, and the correlated color temperature lowered to near 4000 K.« less

Excitation-dependent local symmetry reversal in single host lattice Ba2A(BO3)2:Eu3+ [A = Mg and Ca] phosphors with tunable emission colours.

PubMed

Jayakiruba, S; Chandrasekaran, S Selva; Murugan, P; Lakshminarasimhan, N

2017-07-05

Eu 3+ activated phosphors are widely used as red emitters in various display devices and light emitting diodes (LEDs). The emission characteristics of Eu 3+ depend on the local site symmetry. The present study demonstrates the role of excitation-dependent local symmetry changes due to the structural reorganization on the emission colour tuning of Eu 3+ from orange-red to orange in single host lattices, Ba 2 Mg(BO 3 ) 2 and Ba 2 Ca(BO 3 ) 2 . The choice of these lattices was based on the difference in the extent of strain experienced by the oxygen atoms. The samples with Eu 3+ at Ba or Mg (Ca) sites were synthesized using the conventional high-temperature solid-state reaction method. The samples were characterized using powder XRD, 11 B MAS-NMR, FT-IR, and diffuse reflectance UV-Vis spectroscopic techniques. The room temperature photoluminescence (PL) recorded using different excitation wavelengths revealed a clear difference in the PL emission features due to symmetry reversal from non-inversion to inversion symmetry around Eu 3+ . The reorganization of highly strained oxygen atoms leads to such symmetry reversal. First-principles calculations were used to deduce the optimized structures of the two borate host lattices, and local geometries and their distortions upon Eu 3+ substitution. The outcomes of these calculations support the experimental findings.

Crystal structure of phototoxic orange fluorescent proteins with α tryptophan-based chromophore

DOE PAGES

Pletneva, Nadya V.; Pletnev, Vladimir Z.; Sarkisyan, Karen S.; ...

2015-12-23

Phototoxic fluorescent proteins represent a sparse group of genetically encoded photosensitizers that could be used for precise light-induced inactivation of target proteins, DNA damage, and cell killing. Only two such GFP-based fluorescent proteins (FPs), KillerRed and its monomeric variant SuperNova, were described up to date. We present a crystallographic study of their two orange successors, dimeric KillerOrange and monomeric mKiller-Orange, at 1.81 and 1.57 Å resolution, respectively. They are the first orange-emitting protein photosensitizers with a tryptophan-based chromophore (Gln65-Trp66-Gly67). Same as their red progenitors, both orange photosensitizers have a water-filled channel connecting the chromophore to the β-barrel exterior and enablingmore » transport of ROS. In both proteins, Trp66 of the chromophore adopts an unusual trans-cis conformation stabilized by H-bond with the nearby Gln159. This trans-cis conformation along with the water channel was shown to be a key structural feature providing bright orange emission and phototoxicity of both examined orange photosensitizers.« less

Crystal Structure of Phototoxic Orange Fluorescent Proteins with a Tryptophan-Based Chromophore

PubMed Central

Pletneva, Nadya V.; Pletnev, Vladimir Z.; Sarkisyan, Karen S.; Gorbachev, Dmitry A.; Egorov, Evgeny S.; Mishin, Alexander S.; Lukyanov, Konstantin A.; Dauter, Zbigniew; Pletnev, Sergei

2015-01-01

Phototoxic fluorescent proteins represent a sparse group of genetically encoded photosensitizers that could be used for precise light-induced inactivation of target proteins, DNA damage, and cell killing. Only two such GFP-based fluorescent proteins (FPs), KillerRed and its monomeric variant SuperNova, were described up to date. Here, we present a crystallographic study of their two orange successors, dimeric KillerOrange and monomeric mKillerOrange, at 1.81 and 1.57 Å resolution, respectively. They are the first orange-emitting protein photosensitizers with a tryptophan-based chromophore (Gln65-Trp66-Gly67). Same as their red progenitors, both orange photosensitizers have a water-filled channel connecting the chromophore to the β-barrel exterior and enabling transport of ROS. In both proteins, Trp66 of the chromophore adopts an unusual trans-cis conformation stabilized by H-bond with the nearby Gln159. This trans-cis conformation along with the water channel was shown to be a key structural feature providing bright orange emission and phototoxicity of both examined orange photosensitizers. PMID:26699366

A promising RVO4:Eu(3+), Li(+)@SiO2 (R = Gd, Y and Gd/Y) red-emitting phosphor with improved luminescence (cd/m(2)) and colour purity for optical display applications.

PubMed

Rambabu, Urlagaddala; Munirathnam, Nagegownivari Ramachandra; Reddy, Busireddy Sudhakar; Chatterjee, Sandip

2016-02-01

Red emission intensity was optimized in three stages, by investigating the effects of: (i) host composition (Gd, Y and Gd/Y), (ii) codoping Li(+) as a sensitizer and, finally, (iii) with a SiO2 shell coating as a protecting layer. Lanthanide vanadate powder phosphors were synthesized using a modified colloidal precipitation technique. The effects of SiO2 coating on phosphor particles were characterized using scanning electron microscopy (SEM)-EDAX, transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and photoluminescence (PL) measurements. An improvement in the PL intensity on Li codoping was due to improved crystallinity, which led to higher oscillating strengths for the optical transitions, and also a lowering of the inversion symmetry of Eu(3+) ions. Red emission intensity due to (5)D0  → (5)D2 transition of the phosphor Y0.94VO4:Eu(3+)0.05, Li(+)0.01 was enhanced by 22.28% compared with Y0.95VO4:Eu(3+)0.05, and was further improved by 58.73% with SiO2 coating. The luminescence intensity (I) and colour coordinates (x, y) of the optimized phosphor Y0.94VO4:Eu(3+)0.05, Li(+)0.01@SiO2, where I = 13.07 cd/m(2) and (x = 0.6721, y = 0.3240), were compared with values for a commercial red phosphor (Y2O2S:Eu(3+)), where I = 27 cd/m(2) and (x = 0.6522, y = 0.3437). The measured colour coordinates are superior to those of the commercial red phosphor, and moreover, match well with standard NTSC values (x = 0.67, y = 0.33). Copyright © 2015 John Wiley & Sons, Ltd.

White thin-film flip-chip LEDs with uniform color temperature using laser lift-off and conformal phosphor coating technologies.

PubMed

Lin, Huan-Ting; Tien, Ching-Ho; Hsu, Chen-Peng; Horng, Ray-Hua

2014-12-29

We fabricated a phosphor-conversion white light emitting diode (PC-WLED) using a thin-film flip-chip GaN LED with a roughened u-GaN surface (TFFC-SR-LED) that emits blue light at 450 nm wavelength with a conformal phosphor coating that converts the blue light into yellow light. It was found that the TFFC-SR-LED with the thin-film substrate removal process and surface roughening exhibits a power enhancement of 16.1% when compared with the TFFC-LED without a sapphire substrate. When a TFFC-SR-LED with phosphors on a Cu-metal packaging-base (TFFC-SR-Cu-WLED) was operated at a forward-bias current of 350 mA, luminous flux and luminous efficacy were increased by 17.8 and 11.9%, compared to a TFFC-SR-LED on a Cup-shaped packaging-base (TFFC-SR-Cup-WLED). The angular correlated color temperature (CCT) deviation of a TFFC-SR-Cu-WLED reaches 77 K in the range of -70° to + 70° when the average CCT of white LEDs is around 4300 K. Consequently, the TFFC-SR-LED in a conformal coating phosphor structure on a Cu packaging-base could not only increase the luminous flux output, but also improve the angular-dependent CCT uniformity, thereby reducing the yellow ring effect.

Comparative Photoluminescence Properties and Judd-Ofelt Analysis of Eu3+ Ion-Activated Metal Molybdate Phosphors A2MoO6:Eu3+ (A = La, Y, Gd and Bi)

NASA Astrophysics Data System (ADS)

Han, Bing; Liu, Bingkun; Zhang, Jie; Li, Pengju; Shi, Hengzhen

2017-07-01

A class of red-emitting Eu3+ ion-activated metal molybdate A2MoO6:Eu3+ (A = La, Y, Gd and Bi) phosphors were synthesized by a conventional high-temperature solid-state reaction method. The x-ray diffraction patterns, scanning electron microscope images, Fourier transform infrared spectra, ultraviolet-visible diffuse reflection spectra as well as photoluminescence properties were measured to characterize the as-prepared samples. The photoluminescence properties including excitation/emission spectra, decay curves, Commission Internationale de L'Eclairage chromaticity coordinates and quantum efficiency were comparatively investigated in detail. The Judd-Ofelt theory was also applied to understand the radiative properties of f-f transitions of Eu3+ ions in this system for the first time. The as-prepared phosphors can be effectively excited with near-ultraviolet and/or blue light, and exhibit red emission belonging to the prevailing 5D0 → 7F2 transitions of Eu3+ with short decay time (millisecond level). The results demonstrated that A2MoO6:Eu3+ (A = La, Y, Gd and Bi) phosphors could have potential application as red-emitting phosphors in white light-emitting diodes based on near-ultraviolet and/or blue light-emitting diode chips.

Luminescence enhancement in Eu3+, Sm3+ co-doped liy(MoO4)2 nano-phosphors by sol-gel process.

PubMed

Zhou, Xianju; Wang, Guangchuan; Zhou, Tonghui; Zhou, Kaining; Li, Qingxu; Wang, Zhongqing

2014-05-01

A series of LiY(0.95-x)Eu(0.05)Sm(x)(MoO4)2 red light emitting phosphors were synthesized by sol-gel technique. The phase impurity and spectroscopic properties were characterized by X-ray Diffraction (XRD), Photo-Luminescence (PL) and Photo-Luminescence Excitation (PLE) spectra, respectively. It is found that the PLE spectra of the Eu3+, Sm3+ co-doped nanoparticles are enhanced and broadened as compared with the solely doped samples, which will make the co-doped phosphors match better with blue and/or UV GaN based LED chips. The red emission intensity of Eu3+ is largely enhanced by the energy transfer from Sm3+. The mechanism of the enhancement is clearly proven to be the increase in the quantum efficiency of 5D0 state of Eu3+ rather than the increase in the absorption of Eu3+. Meanwhile, the characteristic f-f transitions of Sm3+ are greatly reduced, resulting in little influence in the color purity of the co-doped phosphors. The present material is an amendatory promising red light emitting phosphor for white LEDs.

Mn2- x Y x (MoO4)3 Phosphor Excited by UV GaN-Based Light-Emitting Diode for White Emission

NASA Astrophysics Data System (ADS)

Chen, Lung-Chien; Tseng, Zong-Liang; Hsu, Ting-Chun; Yang, Shengyi; Chen, Yuan-Bin

2017-04-01

One option for low-cost white light-emitting diodes (LEDs) is the combination of a near-ultraviolet (UV) LED chip (382 nm) and a single phosphor. Such Mn2- x Y x (MoO4)3 single phosphors have been fabricated by a simple solid-state reaction route and their emission color tuned by controlling the Mn doping amount. The chromaticity coordinates of the white light emitted by the UV GaN LED with the MnY(MoO4)3 phosphor were x = 0.5204 and y = 0.4050 [correlated color temperature (CCT) = 7958 K].

The development of new phosphors of Tb3+/Eu3+ co-doped Gd3Al5O12 with tunable emission

NASA Astrophysics Data System (ADS)

Teng, Xin; Wang, Wenzhi; Cao, Zhentao; Li, Jinkai; Duan, Guangbin; Liu, Zongming

2017-07-01

The gadolinium aluminum garnets Gd3Al5O12 (GdAG) activated with Tb3+/Eu3+ were successfully prepared via co-precipitation method at 1500 °C in this work. The crystal structure stabilization, elements analysis, microphotograph, PL/PLE spectra, decay behavior and quantum efficiency were discussed in detail. The metastable GdAG compounds been effectively stabilized by doping with smaller 10 at.% Tb3+, which then allows the development of new phosphors of (Gd0.9-xTb0.1Eux)3Al5O12 (GdAG:Tb3+/Eu3+, x = 0-0.03) for opto-functionality explorations. The PLE/PL spectra displays that the strongest PLE peak was located at ∼276 nm, which overlaps the 8S7/2 → 6IJ transition of Gd3+. Under 276 nm excitation, the phosphors exhibited both Tb3+ and Eu3+ emissions at 548 nm (green, 5D4 → 7F5 transition of Tb3+) and 592 nm (orange-red, 5D0 → 7F1 transition of Eu3+), respectively. The emission intensities of Tb3+ and Eu3+ remarkably varied with the Eu3+ incorporation. As a consequence, the emission color can be readily tuned from approximately green to orange-red. Fluorescence decay analysis found that the lifetime for the Tb3+ emission rapidly decreased conforming to the Tb3+ → Eu3+ energy transfer, and the energy transfer efficiency was calculated. Owing to the Gd3+ → Eu3+ and Gd3+ → Tb3+ energy transfer, the emission intensities of Tb3+ and Eu3+ in (Gd0.9-xTb0.1Eux)AG phosphor were higher than (Y0.87Tb0.1Eu0.03)AG and (Lu0.87Tb0.1Eu0.03)AG system. The (Gd0.9-xTb0.1Eux)AG garnet phosphors developed in this work may serve as a new type of phosphor which hopefully meets the requirements of various lighting and optical display applications.

A far-red fluorescent protein evolved from a cyanobacterial phycobiliprotein.

PubMed

Rodriguez, Erik A; Tran, Geraldine N; Gross, Larry A; Crisp, Jessica L; Shu, Xiaokun; Lin, John Y; Tsien, Roger Y

2016-09-01

Far-red fluorescent proteins (FPs) are desirable for in vivo imaging because with these molecules less light is scattered, absorbed, or re-emitted by endogenous biomolecules compared with cyan, green, yellow, and orange FPs. We developed a new class of FP from an allophycocyanin α-subunit (APCα). Native APC requires a lyase to incorporate phycocyanobilin. The evolved FP, which we named small ultra-red FP (smURFP), covalently attaches a biliverdin (BV) chromophore without a lyase, and has 642/670-nm excitation-emission peaks, a large extinction coefficient (180,000 M(-1)cm(-1)) and quantum yield (18%), and photostability comparable to that of eGFP. smURFP has significantly greater BV incorporation rate and protein stability than the bacteriophytochrome (BPH) FPs. Moreover, BV supply is limited by membrane permeability, and smURFPs (but not BPH FPs) can incorporate a more membrane-permeant BV analog, making smURFP fluorescence comparable to that of FPs from jellyfish or coral. A far-red and near-infrared fluorescent cell cycle indicator was created with smURFP and a BPH FP.

Effect of Annealing Time of YAG:Ce3+ Phosphor on White Light Chromaticity Values

NASA Astrophysics Data System (ADS)

Abd, Husnen R.; Hassan, Z.; Ahmed, Naser M.; Almessiere, Munirah Abdullah; Omar, A. F.; Alsultany, Forat H.; Sabah, Fayroz A.; Osman, Ummu Shuhada

2018-02-01

Yttrium and aluminium nitrate phosphors doped with cerium nitrate and mixed with urea (fuel) are prepared by using microwave-induced combustion synthesis according to the formula Y(3-0.06)Al5O12:0.06Ce3+ (YAG:Ce3+) to produce white light emitting diodes by conversion from blue indium gallium nitride-light emitting diode chips. The sintering time with fixed temperature (1050°C) for phosphor powder was optimized and found to be 5 h. The crystallinity, structure, chemical composition, luminescent properties with varying currents densities and chromaticity were characterized by x-ray diffraction, field emission-scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, photoluminescence emission, electroluminescence and standard CIE 1931 chromaticity diagram, respectively. The energy levels of Ce3+ in YAG were discussed based on its absorption and excitation spectra. The results show that the obtained YAG:Ce3+ phosphor sintered for 5 h has good crystallinity with pure phase, low agglomerate with spherical shaped particles and strong yellow emission, offering cool-white LED with tuneable correlated color temperature and a good color rendering index compared to those prepared by sintering for 2 h and as-prepared phosphor powders.

Yellow and the Novel Aposematic Signal, Red, Protect Delias Butterflies from Predators.

PubMed

Wee, Jocelyn Liang Qi; Monteiro, Antónia

2017-01-01

Butterflies of the South Asian and Australian genus Delias possess striking colours on the ventral wings that are presumed to serve as warning signals to predators. However, this has not been shown empirically. Here we experimentally tested whether the colours of one member of this diverse genus, Delias hyparete, function as aposematic signals. We constructed artificial paper models with either a faithful colour representation of D. hyparete, or with all of its colours converted to grey scale. We also produced models where single colours were left intact, while others were converted to grey-scale or removed entirely. We placed all model types simultaneously in the field, attached to a live mealworm, and measured relative attack rates at three separate field sites. Faithful models of D. hyparete, suffered the least amount of attacks, followed by grey-scale models with unaltered red patches, and by grey-scale models with unaltered yellow patches. We conclude that red and yellow colours function as warning signals. By mapping dorsal and ventral colouration onto a phylogeny of Delias, we observed that yellow and red colours appear almost exclusively on the ventral wing surfaces, and that basal lineages have mostly yellow, white, and black wings, whereas derived lineages contain red colour in addition to the other colours. Red appears to be, thus, a novel adaptive trait in this lineage of butterflies.

Yellow and the Novel Aposematic Signal, Red, Protect Delias Butterflies from Predators

PubMed Central

Wee, Jocelyn Liang Qi

2017-01-01

Butterflies of the South Asian and Australian genus Delias possess striking colours on the ventral wings that are presumed to serve as warning signals to predators. However, this has not been shown empirically. Here we experimentally tested whether the colours of one member of this diverse genus, Delias hyparete, function as aposematic signals. We constructed artificial paper models with either a faithful colour representation of D. hyparete, or with all of its colours converted to grey scale. We also produced models where single colours were left intact, while others were converted to grey-scale or removed entirely. We placed all model types simultaneously in the field, attached to a live mealworm, and measured relative attack rates at three separate field sites. Faithful models of D. hyparete, suffered the least amount of attacks, followed by grey-scale models with unaltered red patches, and by grey-scale models with unaltered yellow patches. We conclude that red and yellow colours function as warning signals. By mapping dorsal and ventral colouration onto a phylogeny of Delias, we observed that yellow and red colours appear almost exclusively on the ventral wing surfaces, and that basal lineages have mostly yellow, white, and black wings, whereas derived lineages contain red colour in addition to the other colours. Red appears to be, thus, a novel adaptive trait in this lineage of butterflies. PMID:28060944

Red persistent luminescence in rare earth-free AlN:Mn 2+ phosphor

DOE PAGES

Xu, Jian; Cherepy, Nerine J.; Ueda, Jumpei; ...

2017-07-03

Here, we investigated the persistent luminescence (PersL) properties of a rare earth-free Mn 2+ doped AlN (AlN:Mn) red phosphor together with a commercial SrAl 2O 4:Eu 2+, Dy 3+ green persistent phosphor as a reference. Similar to its photoluminescence (PL) spectrum, the PersL spectrum of the AlN:Mn phosphor exhibited a red emission band centered at 600 nm due to the Mn 2+: 4T 1( 4G) → 6A 1( 6S) transition with a relatively narrow full width at half maximum (FWHM) of 43 nm. The luminance of AlN:Mn powders was 0.65 mcd/m 2 at 60 min after ceasing ultraviolet (UV) illumination,more » and its duration upon 0.32 mcd/m 2 could reach over 110 min. An extremely broad thermoluminescence (TL) glow curve was observed ranging from 100 K to 600 K and peaked at around 310 K, indicating a wide trap distribution in this material.« less

Red persistent luminescence in rare earth-free AlN:Mn 2+ phosphor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Jian; Cherepy, Nerine J.; Ueda, Jumpei

Here, we investigated the persistent luminescence (PersL) properties of a rare earth-free Mn 2+ doped AlN (AlN:Mn) red phosphor together with a commercial SrAl 2O 4:Eu 2+, Dy 3+ green persistent phosphor as a reference. Similar to its photoluminescence (PL) spectrum, the PersL spectrum of the AlN:Mn phosphor exhibited a red emission band centered at 600 nm due to the Mn 2+: 4T 1( 4G) → 6A 1( 6S) transition with a relatively narrow full width at half maximum (FWHM) of 43 nm. The luminance of AlN:Mn powders was 0.65 mcd/m 2 at 60 min after ceasing ultraviolet (UV) illumination,more » and its duration upon 0.32 mcd/m 2 could reach over 110 min. An extremely broad thermoluminescence (TL) glow curve was observed ranging from 100 K to 600 K and peaked at around 310 K, indicating a wide trap distribution in this material.« less

Synthesis and luminescence studies of Eu (III) doped Sr2P2O7 phosphor for white LED applications

NASA Astrophysics Data System (ADS)

Khan, Z. S.; Ingale, N. B.; Omanwar, S. K.

2018-05-01

Europium (III) doped distrontium diphosphate (Sr2P2O7) is synthesized by slow vaporization method and its luminescence properties are carried out. Using X-Ray diffraction, the crystal structure of this material was confirmed. Photoluminescence (PL) measurement make clear the phosphor exhibited intense emission at 593 nm (yellow) and 612 nm (orange) respectively corresponding to 5D0→7F1 and 5D0→7F2 transitions of Eu3+ on excitation with most favourable 394 nm wavelengths. The remaining excitation peaks at 381 nm and 465 nm with broad band 200-310 nm are also witness in the excitation spectra. The particle morphology using SEM images shows micro level particles for this phosphor. The effect of concentration of Eu3+ ions on the PL intensity has also been investigated. It has been observed that the powder sample exhibits highest PL emission intensity for Eu3+ concentration of about 0.02 moles. The emission spectra exhibit orange performance (CIE chromaticity coordinates: X = 0.672, Y = 0.328), which is due to the 5D0→7F2 transitions of Eu3+ ions. This phosphor is very good for white LED applications.

Method to generate high efficient devices which emit high quality light for illumination

DOEpatents

Krummacher, Benjamin C.; Mathai, Mathew; Choong, Vi-En; Choulis, Stelios A.

2009-06-30

An electroluminescent apparatus includes an OLED device emitting light in the blue and green spectrums, and at least one down conversion layer. The down conversion layer absorbs at least part of the green spectrum light and emits light in at least one of the orange spectra and red spectra.

Highly efficient and stable white organic light emitting diode base on double recombination zones of phosphorescent blue/orange emitters.

PubMed

Lee, Seok Jae; Koo, Ja Ryong; Lim, Dong Hwan; Park, Hye Rim; Kim, Young Kwan; Ha, Yunkyoung

2011-08-01

We demonstrated efficient and stable white phosphorescent organic light-emitting diodes (OLEDs) with double-emitting layers (D-EMLs), which were comprised of two emissive layers with a hole transport-type host of N,N'-dicarbazolyl-3,5-benzene (mCP) and a electron transport-type host of 2,2',2"-(1,3,5-benzenetryl)tris(1-phenyl)-1H-benzimidazol (TPBi) with blue/orange emitters, respectively. We fabricated two type white devices with single emitting layer (S-EML) and D-EML of orange emitter, maintaining double recombination zone of blue emitter. In addition, the device architecture was developed to confine excitons inside the D-EMLs and to manage triplet excitons by controlling the charge injection. As a result, light-emitting performances of white OLED with D-EMLs were improved and showed the steady CIE coordinates compared to that with S-EML of orange emitter, which demonstrated the maximum luminous efficiency and external quantum efficiency were 21.38 cd/A and 11.09%. It also showed the stable white emission with CIE(x,y) coordinates from (x = 0.36, y = 0.37) at 6 V to (x = 0.33, y = 0.38) at 12 V.

Blue, green, orange, and red upconversion laser

DOEpatents

Xie, Ping; Gosnell, Timothy R.

1998-01-01

A laser for outputting visible light at the wavelengths of blue, green, orange and red light. This is accomplished through the doping of a substrate, such as an optical fiber or waveguide, with Pr.sup.3+ ions and Yb.sup.3+ ions. A light pump such as a diode laser is used to excite these ions into energy states which will produce lasing at the desired wavelengths. Tuning elements such as prisms and gratings can be employed to select desired wavelengths for output.

Understanding the links between composition, polyhedral distortion, and luminescence properties in green-emitting β-Si 6–zAl zO zN 8–z:Eu 2+ phosphors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cozzan, Clayton; Laurita, Geneva; Gaultois, Michael W.

Inorganic phosphor materials play a crucial role in the creation of white light from blue and near-UV solid-state light-emitting diodes. Understanding the intricacies of the phosphor structure is key for setting the stage for improved, more efficient functionality. Average structure and coordination environment analysis of the robust and efficient green-emitting phosphor, β-SiAlON:Eu 2+ (β-Si 6–zAl zO zN 8–zEu 0.009), is combined here with a range of property measurements to elucidate the role of Al content ( z) in luminescence properties, including the red shift of emission and the thermal quenching of luminescence as a function of increasing Al content z.more » Average structure techniques reveal changes in polyhedral distortion with increasing z for the 9-coordinate Eu site in β-SiAlON:Eu 2+. X-ray absorption near edge structure (XANES) is used to confirm that the majority of the activator Eu is in the Eu 2+ state, exhibiting the symmetry-allowed and efficient 4f 75d 0 → 4f 65d 1 transitions. As a result, room temperature and temperature-dependent luminescence indicate a curious increase in thermal stability with increasing z over a small range due to an increasing barrier for thermal ionization, which is correlated to an increase in the quantum yield of the phosphor.« less

Understanding the links between composition, polyhedral distortion, and luminescence properties in green-emitting β-Si 6–zAl zO zN 8–z:Eu 2+ phosphors

DOE PAGES

Cozzan, Clayton; Laurita, Geneva; Gaultois, Michael W.; ...

2017-09-21

Inorganic phosphor materials play a crucial role in the creation of white light from blue and near-UV solid-state light-emitting diodes. Understanding the intricacies of the phosphor structure is key for setting the stage for improved, more efficient functionality. Average structure and coordination environment analysis of the robust and efficient green-emitting phosphor, β-SiAlON:Eu 2+ (β-Si 6–zAl zO zN 8–zEu 0.009), is combined here with a range of property measurements to elucidate the role of Al content ( z) in luminescence properties, including the red shift of emission and the thermal quenching of luminescence as a function of increasing Al content z.more » Average structure techniques reveal changes in polyhedral distortion with increasing z for the 9-coordinate Eu site in β-SiAlON:Eu 2+. X-ray absorption near edge structure (XANES) is used to confirm that the majority of the activator Eu is in the Eu 2+ state, exhibiting the symmetry-allowed and efficient 4f 75d 0 → 4f 65d 1 transitions. As a result, room temperature and temperature-dependent luminescence indicate a curious increase in thermal stability with increasing z over a small range due to an increasing barrier for thermal ionization, which is correlated to an increase in the quantum yield of the phosphor.« less

Characterization of chromoplasts and carotenoids of red- and yellow-fleshed papaya (Carica papaya L.).

PubMed

Schweiggert, Ralf M; Steingass, Christof B; Heller, Annerose; Esquivel, Patricia; Carle, Reinhold

2011-11-01

Chromoplast morphology and ultrastructure of red- and yellow-fleshed papaya (Carica papaya L.) were investigated by light and transmission electron microscopy. Carotenoid analyses by LC-MS revealed striking similarity of nutritionally relevant carotenoid profiles in both the red and yellow varieties. However, while yellow fruits contained only trace amounts of lycopene, the latter was found to be predominant in red papaya (51% of total carotenoids). Comparison of the pigment-loaded chromoplast ultrastructures disclosed tubular plastids to be abundant in yellow papaya, whereas larger crystalloid substructures characterized most frequent red papaya chromoplasts. Exclusively existent in red papaya, such crystalloid structures were associated with lycopene accumulation. Non-globular carotenoid deposition was derived from simple solubility calculations based on carotenoid and lipid contents of the differently colored fruit pulps. Since the physical state of carotenoid deposition may be decisive regarding their bioavailability, chromoplasts from lycopene-rich tomato fruit (Lycopersicon esculentum L.) were also assessed and compared to red papaya. Besides interesting analogies, various distinctions were ascertained resulting in the prediction of enhanced lycopene bioavailability from red papaya. In addition, the developmental pathway of red papaya chromoplasts was investigated during fruit ripening and carotenogenesis. In the early maturation stage of white-fleshed papaya, undifferentiated proplastids and globular plastids were predominant, corresponding to incipient carotenoid biosynthesis. Since intermediate plastids, e.g., amyloplasts or chloroplasts, were absent, chromoplasts are likely to emerge directly from proplastids.

Synthesis and Electroluminescent Property of New Orange Iridium Compounds for Flexible White Organic Light Emitting Diodes.

PubMed

Lee, Ho Won; Jeong, Hyunjin; Kim, Young Kwan; Ha, Yunkyoung

2015-10-01

Recently, white organic light-emitting diodes (OLEDs) have aroused considerable attention because they have the potential of next-generation flexible displays and white illuminated applications. White OLED applications are particularly heading to the industry but they have still many problems both materials and manufacturing. Therefore, we proposed that the new iridium compounds of orange emitters could be demonstrated and also applied to flexible white OLEDs for verification of potential. First, we demonstrated the chemical properties of new orange iridium compounds. Secondly, conventional two kinds of white phosphorescent OLEDs were fabricated by following devices; indium-tin oxide coated glass substrate/4,4'-bis[N-(napthyl)-N-phenylamino]biphenyl/N,N'-dicarbazolyl-3,5-benzene doped with blue and new iridium compounds for orange emitting 8 wt%/1,3,5-tris[N-phenylbenzimidazole-2-yl]benzene/lithium quinolate/aluminum. In addition, we fabricated white OLEDs using these emitters to verify the potential on flexible substrate. Therefore, this work could be proposed that white light applications can be applied and could be extended to additional research on flexible applications.

Ultrathin nondoped emissive layers for efficient and simple monochrome and white organic light-emitting diodes.

PubMed

Zhao, Yongbiao; Chen, Jiangshan; Ma, Dongge

2013-02-01

In this paper, highly efficient and simple monochrome blue, green, orange, and red organic light emitting diodes (OLEDs) based on ultrathin nondoped emissive layers (EMLs) have been reported. The ultrathin nondoped EML was constructed by introducing a 0.1 nm thin layer of pure phosphorescent dyes between a hole transporting layer and an electron transporting layer. The maximum external quantum efficiencies (EQEs) reached 17.1%, 20.9%, 17.3%, and 19.2% for blue, green, orange, and red monochrome OLEDs, respectively, indicating the universality of the ultrathin nondoped EML for most phosphorescent dyes. On the basis of this, simple white OLED structures are also demonstrated. The demonstrated complementary blue/orange, three primary blue/green/red, and four color blue/green/orange/red white OLEDs show high efficiency and good white emission, indicating the advantage of ultrathin nondoped EMLs on constructing simple and efficient white OLEDs.

Ca 1-xMo 1-ySi yO 4:Eu x3+: A novel red phosphor for white light emitting diodes

NASA Astrophysics Data System (ADS)

Ci, Zhipeng; Wang, Yuhua; Zhang, Jiachi; Sun, Yunkui

2008-03-01

Single phase of Ca 1-xMo 1-ySi yO 4:Eu x3+ (0.18⩽ x⩽0.26, 0⩽ y⩽0.04) was synthesized by solid-state method. The photoluminescence investigation indicated that Ca 1-xMoO 4:Eu x3+ (0.18⩽ x⩽0.26) could be effectively excited by 393 and 464 nm, and it exhibited an intense red emission at 615 nm. The introduction of Si 4+ ions did not change the position of the peaks but strongly enhanced the emission intensity of Eu 3+ under 393 and 464 nm excitations and showed very good color purity. The emission intensity of optimal Ca 0.8Mo 0.98Si 0.02O 4:Eu 0.23+ sample (excited by 393 nm) was about 5.5 times higher than that of the phosphor Y 2O 2S:0.05Eu 3+. So this phosphor could be nicely suitable for the application of the UV LED chips.

In situ X-ray fluorescence-based method to differentiate among red ochre pigments and yellow ochre pigments thermally transformed to red pigments of wall paintings from Pompeii.

PubMed

Marcaida, Iker; Maguregui, Maite; Fdez-Ortiz de Vallejuelo, Silvia; Morillas, Héctor; Prieto-Taboada, Nagore; Veneranda, Marco; Castro, Kepa; Madariaga, Juan Manuel

2017-06-01

Most of the magnificent wall paintings from the ancient city of Pompeii are decorated with red and yellow colors coming from the ochre pigments used. The thermal impact of the pyroclastic flow from the eruption of Vesuvius, in AD 79, promoted the transformation of some yellow painted areas to red. In this work, original red ochre, original yellow ochre, and transformed yellow ochre (nowadays showing a red color) of wall paintings from Pompeian houses (House of Marcus Lucretius and House of Gilded Cupids) were analyzed by means of a handheld energy-dispersive X-ray fluorescence spectrometer to develop a fast method that allows chemical differentiation of the original red ochre and the transformed yellow ochre. Principal component analysis of the multivariate obtained data showed that arsenic is the tracer element to distinguish between both red colored ochres. Moreover, Pompeian raw red and yellow ochre pigments recovered from the burial were analyzed in the laboratory with use of a benchtop energy-dispersive X-ray fluorescence spectrometer to confirm the elemental composition and the conclusions drawn from the in situ analysis according to the yellow ochre pigment transformation in real Pompeian wall paintings.

Blue, green, orange, and red upconversion laser

DOEpatents

Xie, P.; Gosnell, T.R.

1998-09-08

A laser is disclosed for outputting visible light at the wavelengths of blue, green, orange and red light. This is accomplished through the doping of a substrate, such as an optical fiber or waveguide, with Pr{sup 3+} ions and Yb{sup 3+} ions. A light pump such as a diode laser is used to excite these ions into energy states which will produce lasing at the desired wavelengths. Tuning elements such as prisms and gratings can be employed to select desired wavelengths for output. 11 figs.

Synthesis of europium- or terbium-activated calcium tungstate phosphors

NASA Astrophysics Data System (ADS)

Forgaciu, Flavia; Popovici, Elisabeth-Jeanne; Ungur, Laura; Vadan, Maria; Vasilescu, Marilena; Nazarov, Mihail

2001-06-01

Utilization of luminescent substances in various optoelectronic devices depends on their luminescent properties and sensitivity to various excitation radiation as well as on particle size distribution and crystalline structure of luminous powders. Calcium tungstate phosphors are well excited with roentgen radiation, so that they are largely used for manufacture of x-ray intensifying screens. Being sensitive to short UV-radiation as well, they could be utilized in Plasma Display Panels or in advertising signs fluorescent tubes. In order to diversify the utilization possibilities of this tungstate class, luminescent powders based on CaWO4:Eu3+ and CaWO4:Tb3+ were synthesized and characterized. As compared with the starting self-activated phosphor, larger excitation wavelength domain and emission colors from blue-to-green-to- yellow-to-red were obtained. The good UV excitability and variable luminescence color recommend these phosphors for optoelectronic device manufacture.

Phosphor-Free InGaN White Light Emitting Diodes Using Flip-Chip Technology

PubMed Central

Li, Ying-Chang; Chang, Liann-Be; Chen, Hou-Jen; Yen, Chia-Yi; Pan, Ke-Wei; Huang, Bohr-Ran; Kuo, Wen-Yu; Chow, Lee; Zhou, Dan; Popko, Ewa

2017-01-01

Monolithic phosphor-free two-color gallium nitride (GaN)-based white light emitting diodes (LED) have the potential to replace current phosphor-based GaN white LEDs due to their low cost and long life cycle. Unfortunately, the growth of high indium content indium gallium nitride (InGaN)/GaN quantum dot and reported LED’s color rendering index (CRI) are still problematic. Here, we use flip-chip technology to fabricate an upside down monolithic two-color phosphor-free LED with four grown layers of high indium quantum dots on top of the three grown layers of lower indium quantum wells separated by a GaN tunneling barrier layer. The photoluminescence (PL) and electroluminescence (EL) spectra of this white LED reveal a broad spectrum ranging from 475 to 675 nm which is close to an ideal white-light source. The corresponding color temperature and color rendering index (CRI) of the fabricated white LED, operated at 350, 500, and 750 mA, are comparable to that of the conventional phosphor-based LEDs. Insights of the epitaxial structure and the transport mechanism were revealed through the TEM and temperature dependent PL and EL measurements. Our results show true potential in the Epi-ready GaN white LEDs for future solid state lighting applications. PMID:28772792

Chlorine-Free Red-Burning Pyrotechnics.

PubMed

Sabatini, Jesse J; Koch, Ernst-Christian; Poret, Jay C; Moretti, Jared D; Harbol, Seth M

2015-09-07

The development of a red, chlorine-free pyrotechnic illuminant of high luminosity and spectral purity was investigated. Red-light emission based solely on transient SrOH(g) has been achieved by using either 5-amino-1H-tetrazole or hexamine to deoxidize the combustion flame of a Mg/Sr(NO3 )2 /Epon-binder composition and reduce the amount of both condensed and gaseous SrO, which emits undesirable orange-red light. The new formulations were found to possess high thermal onset temperatures. Avoiding chlorine in these formulations eliminates the risk of the formation of PCBs, PCDDs, and PCDFs. This finding, hence, will have a great impact on both military pyrotechnics and commercial firework sectors. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural and photoluminescence properties of stannate based displaced pyrochlore-type red phosphors: Ca(3-x)Sn₃Nb₂O₁₄:xEu³⁺.

PubMed

Sreena, T S; Prabhakar Rao, P; Francis, T Linda; Raj, Athira K V; Babu, Parvathi S

2015-05-14

New stannate based displaced pyrochlore-type red phosphors, Ca(3-x)Sn3Nb2O14:xEu(3+), were prepared via a conventional solid state method. The influence of partial occupancy of Sn in both A and B sites of the pyrochlore-type oxides on the photoluminescence properties was studied using powder X-ray diffraction, FT-Raman, transmission electron microscopy, scanning electron microscopy with energy dispersive spectrometry, UV-visible absorption spectroscopy, and photoluminescence excitation and emission spectra with lifetime measurements. The structural analysis establishes that these oxides belong to a cubic displaced pyrochlore type structure with a space group Fd3̄m. These phosphors exhibit strong absorptions at near UV and blue wavelength regions and emit intense multiband emissions due to Eu(3+ 5)D0-(7)F(0, 1, 2) transitions. The absence of characteristic MD transition splitting points out that local cation disorder exists in this type of displaced pyrochlores, reducing the D(3d) inversion symmetry, which is not evidenced by such disorder in the X-ray diffraction analysis. The unusual forbidden intense sharp (5)D0-(7)F0 transition indicates single site occupancy of Eu(3+) with a narrower range of bonding environment, preventing the cluster formation. This is supported by the stable (5)D0 lifetime with Eu(3+) concentration. The Judd-Ofelt intensity parameter assessment corroborates these results. The CIE color coordinates of these phosphors were found to be (0.60, 0.40), which are close to the NTSC standard values (0.67, 0.33) for a potential red phosphor.

Intrinsic Polarization and Tunable Color of Electroluminescence from Organic Single Crystal-based Light-Emitting Devices

PubMed Central

Ding, Ran; Feng, Jing; Zhou, Wei; Zhang, Xu-Lin; Fang, Hong-Hua; Yang, Tong; Wang, Hai-Yu; Hotta, Shu; Sun, Hong-Bo

2015-01-01

A single crystal-based organic light-emitting device (OLED) with intrinsically polarized and color-tunable electroluminescence (EL) has been demonstrated without any subsequent treatment. The polarization ratio of 5:1 for the transversal-electric (TE) and transversal-magnetic (TM) polarization at the emission peak of 575 nm, and 4.7:1 for the TM to TE polarization at the emission peak of 635 nm, respectively, have been obtained. The emitting color is tunable between yellow, yellow-green and orange by changing the polarization angle. The polarized EL and the polarization-induced color tunability can be attributed to the anisotropic microcavity formed by the BP3T crystal with uniaxial alignment of the molecules. PMID:26207723

New red Y 0.85Bi 0.1Eu 0.05V 1-yM yO 4 (M=Nb, P) phosphors for light-emitting diodes

NASA Astrophysics Data System (ADS)

Wang, Yuhua; Sun, Yunkui; Zhang, Jiachi; Ci, Zhipeng; Zhang, Zhiya; Wang, Lei

2008-06-01

The Y 0.85Bi 0.1Eu 0.05V 1-yM yO 4 (M=Nb, P) as new near-ultraviolet excited phosphors were synthesized and their luminescence properties under 365 nm excitation were investigated in detail. It indicated that by doping small amount of P 5+ into V 5+ sites, the excitation intensity of charge transfer (CT) band of Bi-O (330-400 nm) was greatly improved. By substituting Nb 5+ for V 5+, both the CT bands of Bi-O and Eu-O (240-320 nm) were significantly enhanced. As a result, the emission intensity of Y 0.85Bi 0.1Eu 0.05V 1-yM yO 4 (M=Nb, P) could be improved about 90% by doping 5 mol% P 5+ and 110% by doping 5 mol% Nb 5+. Comparing with the commercial Y 2O 2S:Eu 3+ phosphors, the Y 0.85Bi 0.1Eu 0.05V 0.95M 0.05O 4 (M=Nb, P) phosphors exhibited excellent color purity and much higher brightness. The results showed that these Y 0.85Bi 0.1Eu 0.05V 1-yM yO 4 (M=Nb, P) phosphors could be considered as promising red phosphors for application in LED.

Bright luminescence from pure DNA-curcumin–based phosphors for bio hybrid light-emitting diodes

PubMed Central

Reddy, M. Siva Pratap; Park, Chinho

2016-01-01

Recently, significant advances have occurred in the development of phosphors for bio hybrid light-emitting diodes (Bio-HLEDs), which have created brighter, metal-free, rare-earth phosphor-free, eco-friendly, and cost-competitive features for visible light emission. Here, we demonstrate an original approach using bioinspired phosphors in Bio-HLEDs based on natural deoxyribonucleic acid (DNA)-curcumin complexes with cetyltrimethylammonium (CTMA) in bio-crystalline form. The curcumin chromophore was bound to the DNA double helix structure as observed using field emission tunnelling electron microscopy (FE-TEM). Efficient luminescence occurred due to tightly bound curcumin chromophore to DNA duplex. Bio-HLED shows low luminous drop rate of 0.0551 s−1. Moreover, the solid bio-crystals confined the activating bright luminescence with a quantum yield of 62%, thereby overcoming aggregation-induced quenching effect. The results of this study herald the development of commercially viable large-scale hybrid light applications that are environmentally benign. PMID:27572113

Bright luminescence from pure DNA-curcumin-based phosphors for bio hybrid light-emitting diodes

NASA Astrophysics Data System (ADS)

Reddy, M. Siva Pratap; Park, Chinho

2016-08-01

Recently, significant advances have occurred in the development of phosphors for bio hybrid light-emitting diodes (Bio-HLEDs), which have created brighter, metal-free, rare-earth phosphor-free, eco-friendly, and cost-competitive features for visible light emission. Here, we demonstrate an original approach using bioinspired phosphors in Bio-HLEDs based on natural deoxyribonucleic acid (DNA)-curcumin complexes with cetyltrimethylammonium (CTMA) in bio-crystalline form. The curcumin chromophore was bound to the DNA double helix structure as observed using field emission tunnelling electron microscopy (FE-TEM). Efficient luminescence occurred due to tightly bound curcumin chromophore to DNA duplex. Bio-HLED shows low luminous drop rate of 0.0551 s-1. Moreover, the solid bio-crystals confined the activating bright luminescence with a quantum yield of 62%, thereby overcoming aggregation-induced quenching effect. The results of this study herald the development of commercially viable large-scale hybrid light applications that are environmentally benign.

Identification and phylogenetic analysis of local yellow and orange sweet potatoes genotypes in Sumatera Utara

NASA Astrophysics Data System (ADS)

Rosmayati; Bakti, D.

2018-02-01

The objectives of this research was to identify and create database about the diversity of local yellow and orange sweet potatoes accessions in Sumatera Utara, have diversity accession local sweet potatoes genotype in Sumatera Utara selection for classifying populations get high production and good fruit quality. The experiment was conducted in areas of production centers of sweet potatoes in the exploration survey methods in 2 districts in Sumatera Utara, which is in the Kabupaten Simalungun and Dairi. The study was conducted on June to July 2017. Observations were made based on the identification and characterization Description List of International Board for Plant Genetic Resources standard and purposive random sampling technique. The result of this research indicate there 15 genotype of sweet potato yellow and orange in KabupatenSimalungun consistedof KecamatanPurba (G3, G4 and G7), Silimakuta (G5, G6 and G14), and Pamatang Silimahuta (G15) in Kabupaten Dairi consists of Kecamatan Parbuluan (G1, G2, G8 and G9), Sidikalang (G10 and G13), Sumbul (G11), and Sitinjo (G12) with nearest relationship is G13 and G15 with a coefficient similarity 23.908 and farthest relationship is G2 and G7 with a coefficient similarity 140.029.

A novel single-phase white phosphor NaBaBO{sub 3}:Dy{sup 3+},K{sup +} for near-UV white light-emitting diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Jianghui; Cheng, Qijin; Wu, Jieyang

Highlights: • A white phosphor NaBaBO{sub 3}:Dy{sup 3+},K{sup +} with CIE coordinate (0.301, 0.308) was synthesized. • The optimum doping concentration of Dy{sup 3+} ions was found. • The effect and mechanism of K{sup +} ion as a charge compensator were discussed. • Temperature-dependent PL property of NaBaBO{sub 3}:Dy{sup 3+},K{sup +} was studied. • PL decay and quantum efficiency behaviors of the samples were investigated. - Abstract: A novel Dy{sup 3+}-doped NaBaBO{sub 3} white-emitting phosphor has been prepared by high temperature solid-state reaction method. The phase structure and luminescence properties of NaBaBO{sub 3}:Dy{sup 3+},K{sup +} samples were investigated. Photoluminescence resultsmore » show that the as-prepared samples could be effectively excited by near-ultraviolet (NUV) light and generate white light emission due to the {sup 4}F{sub 9/2} → {sup 6}H{sub 15/2} (blue) transition and {sup 4}F{sub 9/2} → {sup 6}H{sub 13/2} (yellow) transition of Dy{sup 3+} ions, respectively. The optimum doping concentration of Dy{sup 3+} ions in the NaBaBO{sub 3} host was determined to be 5.0 mol% and the CIE chromaticity of the sample was determined to be (0.301, 0.308). Moreover, the mechanism of K{sup +} ion as a charge compensator on the improvement of photoluminescence property and the effect of temperature on the photoluminescence property of NaBaBO{sub 3}:Dy{sup 3+},K{sup +} were investigated. Furthermore, photoluminescence decay and quantum efficiency behaviors of NaBaBO{sub 3}:Dy{sup 3+},K{sup +} were also studied. The present work demonstrates that the NaBaBO{sub 3}:Dy{sup 3+},K{sup +} phosphor is a potential candidate for NUV white light emitting diodes.« less

Seasonal variation in the structure of red reflectance of leaves from yellow poplar, red oak, and red maple

NASA Technical Reports Server (NTRS)

Brakke, Thomas W.; Wergin, William P.; Erbe, Eric F.; Harnden, Joann M.

1993-01-01

The light scattered from leaves was measured as a function of view angle in the principal plane for yellow poplar, red oak, and red maple. The source was a parallel-polarized helium-neon laser. Yellow poplar leaves had the highest reflectance of the three species, which may have been due to its shorter palisade cells and more extensive spongy mesophyll. Prior to senescence, there was a significant decrease, but not total extinction, in the reflectance of the beam incident at 60 deg from nadir on the adaxial side of the leaves of all three species. Low-temperature SEM observations showed differences in the surface wax patterns among the three species but did not indicate a cause of the reflectance changes other than possibly the accumulation and aging of the wax.

Orange and red upconversion laser pumped by an avalanche mechanism in Pr3+, Yb3+:BaY2F8

NASA Astrophysics Data System (ADS)

Osiac, E.; Heumann, E.; Huber, G.; Kück, S.; Sani, E.; Toncelli, A.; Tonelli, M.

2003-06-01

The letter reports on upconverted orange (607.5 nm, 3P0→3H6) and red (638.7 nm, 3P0→3F2) laser oscillation at room temperature observed in Pr3+, Yb3+:BaY2F8 under excitation at 822 or 841 nm at 300 K. The upconversion mechanism that populates the emitting level is an avalanche excitation mechanism. Output powers up to 55 mW and slope efficiencies up to 27% were demonstrated at 607.5 nm. At 638.7 nm, the maximum output power was 26 mW with a slope efficiency of about 13.5%.

When yellow lights look red: tinted sunglasses on the railroads.

PubMed

Hovis, Jeffery K

2011-02-01

A major Canadian railway company purchased safety eyewear sunglasses that were purported to have a neutral gray tint and that met the North American occupational and fashion sunglass requirements for signal light transmittance. After several weeks, the company began to receive reliable reports from employees that the yellow wayside signal appeared red when viewed through these sunglasses. Furthermore, the lenses themselves appeared to have a greenish brown tint rather than gray as the labeling implied. The transmission properties of the lenses were measured with a spectrophotometer, and color shifts were calculated for both roadway and railway signal lights. The lenses did have a brown tint and they did meet the North American and European occupational sunglass transmittance requirements for roadway traffic signal lights. However, they did not meet the Australian occupational requirements because the red signal visibility factor was too high. Calculations using typical railroad wayside signal lights showed that the lenses would shift the yellow signal chromaticity coordinates beyond the boundaries for the railway yellow signals and toward the red end of the International Commission on Illumination chromaticity diagram, confirming the employees' reports. Although the lenses met the North American and European sunglass transmittance requirements for traffic signal lights, the results showed that these standards are inappropriate for the railroad environment because the yellow wayside signal lights are redder and smaller in angular size than typical North American and European traffic lights. Some suggestions on a modified transmittance requirement are given to avoid this problem in the future.

Nearly suppressed photoluminescence blinking of small-sized, blue-green-orange-red emitting single CdSe-based core/gradient alloy shell/shell quantum dots: correlation between truncation time and photoluminescence quantum yield.

PubMed

Roy, Debjit; Mandal, Saptarshi; De, Chayan K; Kumar, Kaushalendra; Mandal, Prasun K

2018-04-18

CdSe-based core/gradient alloy shell/shell semiconductor quantum dots (CGASS QDs) have been shown to be optically quite superior compared to core-shell QDs. However, very little is known about CGASS QDs at the single particle level. Photoluminescence blinking dynamics of four differently emitting (blue (λem = 510), green (λem = 532), orange (λem = 591), and red (λem = 619)) single CGASS QDs having average sizes <∼7 nm have been probed in our home-built total internal reflection fluorescence (TIRF) microscope. All four samples possess an average ON-fraction of 0.70-0.85, which hints towards nearly suppressed PL blinking in these gradiently alloyed systems. Suppression of blinking has been so far achieved with QDs having sizes greater than 10 nm and mostly emitting in the red region (λem > 600 nm). In this manuscript, we report nearly suppressed PL blinking behaviour of CGASS QDs with average sizes <∼7 nm and emitting in the entire range of the visible spectrum, i.e. from blue to green to orange to red. The probability density distribution of both ON- and OFF-event durations for all of these CGASS QDs could be fitted well with a modified inverse truncated power law with an additional exponential model equation. It has been found that unlike most of the literature reports, the power law exponent for OFF-event durations is greater than the power law exponent for ON-event durations for all four samples. This suggests that relatively large ON-event durations are interrupted by comparatively small OFF-event durations. This in turn is indicative of a suppressed non-radiative Auger recombination process for these CGASS systems. However, in these four different samples the ON-event truncation time varies inversely with the OFF-event truncation time, which hints that both the ON- and OFF-event truncation processes are dictated by some common factor. We have employed 2D joint probability distribution analysis to probe the correlation between the event durations and

(In,Ga,Al)P-GaP laser diodes grown on high-index GaAs surfaces emitting in the green, yellow and bright red spectral range

NASA Astrophysics Data System (ADS)

Ledentsov, N. N.; Shchukin, V. A.; Shernyakov, Yu M.; Kulagina, M. M.; Payusov, A. S.; Gordeev, N. Yu; Maximov, M. V.; Cherkashin, N. A.

2017-02-01

We report on low threshold current density (<400 A cm-2) injection lasing in (Al x Ga1-x )0.5In0.5P-GaAs-based diodes down to the green spectral range (<570 nm). The epitaxial structures are grown on high-index (611)A and (211)A GaAs substrates by metal-organic vapor phase epitaxy and contain tensile-strained GaP-enriched insertions aimed at reflection of the injected nonequilibrium electrons preventing their escape from the active region. Extended waveguide concept results in a vertical beam divergence with a full width at half maximum of 15° for (611)A substrates. The lasing at the wavelength of 569 nm is realized at 85 K. In an orange-red laser diode structure low threshold current density (190 A cm-2) in the orange spectral range (598 nm) is realized at 85 K. The latter devices demonstrated room temperature lasing at 628 nm at ˜2 kA cm-2 and a total power above 3 W. The red laser diodes grown on (211)A substrates demonstrated a far field characteristic for vertically multimode lasing indicating a lower optical confinement factor for the fundamental mode as compared to the devices grown on (611)A. However, as expected from previous research, the temperature stability of the threshold current and the wavelength stability were significantly higher for (211)A-grown structures.

An oxadiazole-functionalized ligand and its yellow-emitting Re(I) complex for organoelectronic application

NASA Astrophysics Data System (ADS)

Hu, Ge; Guo, Lei; Wei, Sheng; Zhang, Shuang

2012-06-01

A Re(I) complex of Re(CO)3(PTO)Br with 2-(pyridin-2-yl)-5-p-tolyl-1,3,4-oxadiazole (PTO) as the diamine ligand is synthesized, resulting in a phosphorescent emitter which contains oxadiazole functional moiety. Single crystal analysis confirms that oxadiazole moiety of PTO ligand participates in the coordination with Re center. Coordination ability difference between N atom from pyridine ring and that from oxadiazole moiety is found. Density functional theory calculation on the crystal suggests that the onset electronic transition owns a mixed character of metal-to-ligand-charge-transfer and ligand-to-ligand-charge-transfer. Upon photon excitation, Re(CO)3(PTO)Br exhibits a yellow emission peaking at 549 nm with a short excited state lifetime of 0.15 μs. Further measurements suggest that Re(CO)3(PTO)Br owns HOMO and LUMO energy levels of -5.79 V and -3.49 V and a high decomposition temperature of 322 °C. The optimal electroluminescence device using Re(CO)3(PTO)Br as the emitting dopant shows an orange light of 598 nm, with a maximum luminance of 4600 cd/m2 and a maximum current efficiency of 11.5 cd/A.

Synthesis, Luminescence Properties and Energy Transfer of CaZrO3:Sm3+, Bi3+ Phosphor

NASA Astrophysics Data System (ADS)

Cao, Renping; Han, Peng; Luo, Wenjie; Fu, Ting; Luo, Zhiyang; Liu, Pan; Chen, Zhiquan; Yu, Xiaoguang

2016-07-01

Novel CaZrO3:Sm3+, Bi3+ phosphor is synthesized by a solid-state reaction method in air and the crystal structures and luminescence properties are investigated. The emission spectrum with excitation 308 nm contains emission of Sm3+ and Bi3+ ions at the same time; however, it only has an emission of Sm3+ ion with excitation 408 nm. Emission intensity of CaZrO3:Sm3+ phosphor can be enhanced about four times owing to energy transfer from the Bi3+ ion to the Sm3+ ion and with the fluxing agent role of Bi3+ ion when Bi3+ ion is co-doped. The possible luminous mechanism is analyzed by energy level diagrams of Bi3+ and Sm3+ ions and the energy transfer process in CaZrO3:Sm3+, Bi3+ phosphor. The experimental results indicate that, hopefully, CaZrO3:Sm3+, Bi3+ phosphor can be used as a reddish orange phosphor candidate for white light-emitting diodes based on near an ultraviolet (~408 nm) chip.

Decolorizing of azo dye Reactive red 24 aqueous solution using exfoliated graphite and H2O2 under ultrasound irradiation.

PubMed

Li, Mei; Li, Ji-Tai; Sun, Han-Wen

2008-07-01

At its natural pH (6.95), the decolorization of Reactive red 24 in ultrasound, ultrasound/H2O2, exfoliated graphite, ultrasound/exfoliated graphite, exfoliated graphite/H2O2 and ultrasound/exfoliated graphite/H2O2 systems were compared. An enhancement was observed for the decolorization in ultrasound/exfoliated graphite/H2O2 system. The effect of solution pH, H2O2 and exfoliated graphite dosages, and temperature on the decolorization of Reactive red 24 was investigated. The sonochemical treatment in combination with exfoliated graphite/H2O2 showed a synergistic effect for the decolorization of Reactive red 24. The results indicated that under proper conditions, there was a possibility to remove Reactive red 24 very efficient from aqueous solution. The decolorization of other azo dyes (Reactive red 2, Methyl orange, Acid red 1, Acid red 73, Acid red 249, Acid orange 7, Acid blue 113, Acid brown 75, Acid green 20, Acid yellow 42, Acid mordant brown 33, Acid mordant yellow 10 and Direct green 1) was also investigated, at their natural pH.

Inorganic yellow-red pigments without toxic metals

NASA Astrophysics Data System (ADS)

Jansen, M.; Letschert, H. P.

2000-04-01

Inorganic pigments have been utilized by mankind since ancient times, and are still widely used to colour materials exposed to elevated temperatures during processing or application. Indeed, in the case of glasses, glazes and ceramics, there is no alternative to inorganic pigments for colouring. However, most inorganic pigments contain heavy metals or transition metals that can adversely effect the environment and human health if critical levels are exceeded. Cadmium-based pigments in particular are a cause of concern: although the pigments are not toxic due to their very low solubility in water and dilute mineral acids, cadmium itself is toxic and can enter the environment in a bioavailable form through waste-disposal sites and incineration plants. This has led to regulations, based on the precautionary principle, that strongly restrict the use of cadmium pigments. And even though recent assessments have concluded that the risk to humans or the environment might be not as significant as originally feared, a strong demand for inherently safer substitutes remains. Here we demonstrate that solid solutions of the perovskites CaTaO 2N and LaTaON2 constitute promising candidates for such substitutes: their brilliance, tinting strength, opacity, dispersability, light-fastness and heat stability rival that of the cadmium pigments, while their colour can be tuned through the desired range, from yellow through orange to deep red, by simple composition adjustments. Because all the constituent elements are harmless, this perovskite-based inorganic pigment system seems a promising replacement that could eliminate one of the sources for cadmium emissions to the environment and some of the remaining concerns about pigment safety.

2-(4-Ethoxy phenyl)-4-phenyl quinoline organic phosphor for solution processed blue organic light-emitting diodes.

PubMed

Ghate, Minakshi; Kalyani, N Thejo; Dhoble, S J

2018-05-31

This paper reports the synthesis and characterization of 2-(4-ethoxyphenyl)-4-phenyl quinoline (OEt-DPQ) organic phosphor using an acid-catalyzed Friedlander reaction and the preparation of blended thin films by molecularly doping OEt-DPQ in poly(methyl methacrylate) (PMMA) at different wt%. The molecular structure of the synthesized phosphor was confirmed by Fourier transform infra-red (FTIR) spectroscopy and nuclear magnetic resonance spectra (NMR). Surface morphology and percent composition of the elements were assessed by scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDAX). The thermal stability and melting point of OEt-DPQ and thin films were probed by thermo-gravimetric analysis (TGA)/differential thermal analysis (DTA) and were found to be 80°C and 113.6°C, respectively. UV-visible optical absorption spectra of OEt-DPQ in the solid state and blended films produced absorption bands in the range 260-340 nm, while photoluminescence (PL) spectra of OEt-DPQ in the solid state and blended thin films demonstrated blue emission that was registered at 432 nm when excited at 363-369 nm. However, solvated OEt-DPQ in chloroform, tetrahydrofuran or dichloromethane showed a blue shift of 31-43 nm. Optical absorption and emission parameters such as molar extinction coefficient (ε), energy gap (E g ), transmittance (T), reflectance (R), refractive index (n), oscillator energy (E 0 ) and oscillator strength (f), quantum yield (φ f ), oscillator energy (E 0 ), dispersion energy (E d ), Commission Internationale de l'Éclairage (CIE) co-ordinates and energy yield fluorescence (E F ) were calculated to assess the phosphor's suitability as a blue emissive material for opto-electronic applications such as organic light-emitting diodes (OLEDs), flexible displays and solid-state lighting technology. Copyright © 2018 John Wiley & Sons, Ltd.

Novel Design of Iridium Phosphors with Pyridinylphosphinate Ligands for High-Efficiency Blue Organic Light-emitting Diodes

PubMed Central

Wu, Zheng-Guang; Jing, Yi-Ming; Lu, Guang-Zhao; Zhou, Jie; Zheng, You-Xuan; Zhou, Liang; Wang, Yi; Pan, Yi

2016-01-01

Due to the high quantum efficiency and wide scope of emission colors, iridium (Ir) (III) complexes have been widely applied as guest materials for OLEDs (organic light-emitting diodes). Contrary to well-developed Ir(III)-based red and green phosphorescent complexes, the efficient blue emitters are rare reported. Like the development of the LED, the absence of efficient and stable blue materials hinders the widely practical application of the OLEDs. Inspired by this, we designed two novel ancillary ligands of phenyl(pyridin-2-yl)phosphinate (ppp) and dipyridinylphosphinate (dpp) for efficient blue phosphorescent iridium complexes (dfppy)2Ir(ppp) and (dfppy)2Ir(dpp) (dfppy = 2-(2,4-difluorophenyl)pyridine) with good electron transport property. The devices using the new iridium phosphors display excellent electroluminescence (EL) performances with a peak current efficiency of 58.78 cd/A, a maximum external quantum efficiency of 28.3%, a peak power efficiency of 52.74 lm/W and negligible efficiency roll-off ratios. The results demonstrated that iridium complexes with pyridinylphosphinate ligands are potential blue phosphorescent materials for OLEDs. PMID:27929124

Lithium-aluminum-zinc phosphate glasses activated with Tb3+ and Tb3+/Eu3+ for green laser medium, reddish-orange and white phosphor applications

NASA Astrophysics Data System (ADS)

Francisco-Rodriguez, H. I.; Lira, A.; Soriano-Romero, O.; Meza-Rocha, A. N.; Bordignon, S.; Speghini, A.; Lozada-Morales, R.; Caldiño, U.

2018-05-01

A spectroscopic analysis of Tb3+ and Tb3+/Eu3+ doped lithium-aluminum-zinc phosphate glasses is performed through their absorbance and photoluminescence spectra, and decay time profiles. Laser parameter values (stimulated emission cross section, effective bandwidth, gain bandwidth and optical gain) were obtained for the terbium 5D4 → 7F5 green emission from the Tb3+ singly-doped glass (LAZT) excited at 350 nm to judge the suitability of the glass phosphor for fiber lasers. A quantum yield of (47.68 ± 0.49)% was measured for the 5D4 level luminescence. Upon 350 nm excitation the LAZT glass phosphor emits green light with a color purity of 65.6% and chromaticity coordinates (0.285, 0.585) very close to those (0.29, 0.60) of European Broadcasting Union illuminant green. The Tb3+/Eu3+codoped glass emission color can be tuned from reddish-orange of 1865 K upon 318 nm excitation to warm white of 3599 K and neutral white of 4049 K upon 359 and 340 nm excitations, respectively. Upon Tb3+ excitation at 340 nm Eu3+ is sensitized by Tb3+ through a non-radiative energy transfer with an efficiency of 0.23-0.26. An electric dipole-dipole interaction might be the dominant mechanism in the Tb3+ to Eu3+ energy transfer taking place into Tb3+ - Eu3+ clusters.

Fumigant Activity of Sweet Orange Essential Oil Fractions Against Red Imported Fire Ants (Hymenoptera: Formicidae).

PubMed

Hu, Wei; Zhang, Ning; Chen, Hongli; Zhong, Balian; Yang, Aixue; Kuang, Fan; Ouyang, Zhigang; Chun, Jiong

2017-08-01

Sweet orange oil fractions were prepared by molecular distillation of cold-pressed orange oil from sample A (Citrus sinensis (L.) 'Hamlin' from America) and sample B (Citrus sinensis Osbeck 'Newhall' from China) respectively, and their fumigant activities against medium workers of red imported fire ants (Solenopsis invicta Buren) were investigated. The volatile composition of the orange oil fractions was identified and quantified using GC-MS. Fractions from sample A (A1, A2, and A3) contained 23, 37, and 48 chemical constituents, and fractions from sample B (B1, B2, and B3) contained 18, 29, and 26 chemical constituents, respectively. Monoterpenes were the most abundant components, accounting for 73.56% to 94.86% of total orange oil fractions, among which D-limonene (65.28-80.18%), β-pinene (1.71-5.58%), 3-carene (0.41-4.01%), β-phellandrene (0.58-2.10%), and linalool (0.31-2.20%) were major constituents. Fumigant bioassay indicated that all orange oil fractions exerted good fumigant toxicity against workers of fire ants at 3, 5, 10, and 20 mg/centrifuge tubes, and B1 had the strongest insecticidal potential, followed by A1, B2, A2, B3, and A3. The fractions composed of more high volatile molecules (A1 and B1) showed greater fumigant effects than others. Compounds linalool and D-limonene, which were the constituents of the orange oil, exhibited excellent fumigant toxicity against red imported fire ant workers. Linalool killed red imported fire ant workers completely at 5, 10, and 20 mg/tube after 8 h of treatment, and D-limonene induced >86% mortality at 8 h of exposure. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Controlling surface property of K2SiF6:Mn4+ for improvement of lighting-emitting diode reliability

NASA Astrophysics Data System (ADS)

Kim, Juseong; Jang, Inseok; Song, Gwang Yeom; Kim, Wan-Ho; Jeon, Sie-Wook; Kim, Jae-Pil

2018-05-01

The surface property of moisture-sensitive K2SiF6:Mn4+ (KSF) as a red-emitting phosphor was controlled through dry-type surface modification in order to improve the photo-performance and reliability of lighting-emitting diode (LED). The phosphor surface was modified with silane coupling agents having different carbon chain length by plasma-assisted method. Comparing between as-prepared and modified KSF, water-resistance and photo-emission efficiency were enhanced due to the formation of hydrophobic shell and the elimination of surface quenching sites. Moreover, the dispersibility of phosphor was increased as increasing the carbon chain length of silane because the interfacial affinity between phosphor and encapsulant was improved. After fabricating LED device, the enhancement of photo-performance and long-term reliability could be successfully achieved in LED device with modified phosphor. It is attributed to that the degradation of phosphor efficiency by moisture was suppressed and heat dissipation in LED PKG was improved through the surface modification.

Optimized photoluminescence of red phosphor K 2 TiF 6 :Mn 4+ synthesized at room temperature and its formation mechanism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lv, Lifen; Chen, Zhen; Liu, Guokui

2015-01-01

The formation mechanism for red phosphors K 2TiF 6:Mn 4+synthesized at room temperature has been discussed. The luminescence intensity has been improved by optimizing the synthetic process. Encapsulation of the red phosphor K 2TiF 6:Mn 4+with YAG:Ce on a GaN layer produces “warm” white LEDs with color rendering 86 at 3251 K.

Red photoluminescence BCNO synthesized from graphene oxide nanosheets

NASA Astrophysics Data System (ADS)

Kang, Yue; Chu, Zeng-yong; Ma, Tian; Li, Wei-ping; Zhang, Dong-jiu; Tang, Xiao-yu

2016-01-01

In this paper, we demonstrate the conversion of graphene oxide (GO) into boron carbon oxynitride (BCNO) hybrid nanosheets via a reaction with boric acid and urea, during which the boron and nitrogen atoms are incorporated into graphene nanosheets. The experimental results reveal that GO is important for the photoluminescence (PL) BCNO phosphor particles. More importantly, in this system, the prepared BCNO phosphors can be used to prepare the materials needed for red light emitting diodes (LEDs).

Skin photorejuvenation effects of light-emitting diodes (LEDs): a comparative study of yellow and red LEDs in vitro and in vivo.

PubMed

Kim, S K; You, H R; Kim, S H; Yun, S J; Lee, S C; Lee, J B

2016-10-01

Red-coloured light-emitting diodes (LEDs) can improve skin photorejuvenation and regeneration by increasing cellular metabolic activity. To evaluate the effectiveness of visible LEDs with specific wavelengths for skin photorejuvenation in vitro and in vivo. Normal human dermal fibroblasts (HDFs) from neonatal foreskin were cultured and irradiated in vitro by LEDs at different wavelengths (410-850 nm) and doses (0-10 J/cm(2) ). In vivo experiments were performed on the skin of hairless mice. Expression of collagen (COL) and matrix metalloproteinases (MMPs) was evaluated by semi-quantitative reverse transcription PCR (semi-qRT-PCR), western blotting and a procollagen type I C-peptide enzyme immunoassay (EIA). Haematoxylin and eosin and Masson trichrome stains were performed to evaluate histological changes. In HDFs, COL I was upregulated and MMP-1 was downregulated in response to LED irradiation at 595 ± 2 and 630 ± 8 nm. In the EIA, a peak result was achieved at a dose of 5 J/cm(2) with LED at 595 ± 2 nm. In vivo, COL I synthesis was upregulated in a dose-dependent manner to both 595 and 630 nm LED irradiation, and this effect was prolonged to 21 days after a single irradiation with a dose of 100 J/cm(2) . These histological changes were consistent with the results of semi-qRT-PCR and western blots. Specific LED treatment with 595 ± 2 and 630 ± 8 nm irradiation was able to modulate COL and MMPs in skin, with the effects persisting for at least 21 days after irradiation. These findings suggest that yellow and red LEDs might be useful tools for skin photorejuvenation. © 2016 British Association of Dermatologists.

Thermally stable green Ba(3)Y(PO(4))3:Ce(3+),Tb(3+) and red Ca(3)Y(AlO)(3)(BO(3))4:Eu(3+) phosphors for white-light fluorescent lamps.

PubMed

Huang, Chien-Hao; Kuo, Te-Wen; Chen, Teng-Ming

2011-01-03

A class of thermal stable of green-emitting phosphors Ba(3)Y(PO(4))(3):Ce(3+),Tb(3+) (BYP:Ce(3+),Tb(3+)) and red-emitting phosphors Ca(3)Y(AlO)(3)(BO(3))(4):Eu(3+) (CYAB:Eu(3+)) for white-light fluorescent lamps were synthesized by high temperature solid-state reaction. We observed a decay of only 3% at 150 °C for BYP:0.25Ce3+,0.25Tb3+ (3% for LaPO4:Ce(3+),Tb(3+)), and a decay of 4% for CYAB:0.5Eu(3+) (7% for Y(2)O(3):Eu(3+), 24% for Y(2)O(2)S:Eu(3+)). The emission intensity of composition-optimized Ba(3)(Y(0.5)Ce(0.25)Tb(0.25))(PO(4))(3) is 70% of that of commercial LaPO(4):Ce(3+),Tb(3+) phosphors, and the CIE chromaticity coordinates are found to be (0.323, 0.534). The emission intensity of Ca(3)(Y(0.5)Eu(0.5))(AlO)(3)(BO(3))(4) is 70% and 83% of those of Y(2)O(3):Eu(3+) and Y(2)O(2)S:Eu(3+) phosphors, respectively, and the CIE chromaticity coordinates are redder (0.652, 0.342) than those of Y(2)O(3):Eu(3+) (0.645, 0.347) and Y(2)O(2)S:Eu(3+) (0.647, 0.343). A white-light fluorescent lamp is fabricated using composition-optimized Ba(3)(Y(0.5)Ce(0.25)Tb(0.25))(PO(4))(3) and Ca(3)(Y(0.5)Eu(0.5))(AlO)(3)(BO(3))(4) phosphors and matching blue-emitting phosphors. The results indicate that the quality of the brightness and color reproduction is suitable for application in shortwave UV fluorescent lamps. The white-light fluorescent lamp displays CIE chromaticity coordinates of x = 0.33, y = 0.35, a warm white light with a correlated color temperature of 5646 K, and a color-rendering index of Ra = 70.

Radical scavenging activities of Rio Red grapefruits and Sour orange fruit extracts in different in vitro model systems.

PubMed

Jayaprakasha, G K; Girennavar, Basavaraj; Patil, Bhimanagouda S

2008-07-01

Antioxidant fractions from two different citrus species such as Rio Red (Citrus paradise Macf.) and Sour orange (Citrus aurantium L.) were extracted with five different polar solvents using Soxhlet type extractor. The total phenolic content of the extracts was determined by Folin-Ciocalteu method. Ethyl acetate extract of Rio Red and Sour orange was found to contain maximum phenolics. The dried fractions were screened for their antioxidant activity potential using in vitro model systems such as 1,1-diphenyl-2-picryl hydrazyl (DPPH), phosphomolybdenum method and nitroblue tetrazolium (NBT) reduction at different concentrations. The methanol:water (80:20) fraction of Rio Red showed the highest radical scavenging activity 42.5%, 77.8% and 92.1% at 250, 500 and 1000 ppm, respectively, while methanol:water (80:20) fraction of Sour orange showed the lowest radical scavenging activity at all the tested concentrations. All citrus fractions showed good antioxidant capacity by the formation of phosphomolybdenum complex at 200 ppm. In addition, superoxide radical scavenging activity was assayed using non-enzymatic (NADH/phenaxine methosulfate) superoxide generating system. All the extracts showed variable superoxide radical scavenging activity. Moreover, methanol:water (80:20) extract of Rio Red and methanol extract of Sour orange exhibited marked reducing power in potassium ferricyanide reduction method. The data obtained using above in vitro models clearly establish the antioxidant potential of citrus fruit extracts. However, comprehensive studies need to be conducted to ascertain the in vivo bioavailability, safety and efficacy of such extracts in experimental animals. To the best of our knowledge, this is the first report on antioxidant activity of different polar extracts from Rio Red and Sour oranges.

Luminescence optimization of MBO 3:Eu 3+ (M=Y, Gd, Al) red phosphor by spray pyrolysis using combinatorial chemistry

NASA Astrophysics Data System (ADS)

Youl Jung, Kyeong

2010-08-01

Conventional solution-based combinatorial chemistry was combined with spray pyrolysis and applied to optimize the luminescence properties of (Y x, Gd y, Al z)BO 3:Eu 3+ red phosphor under vacuum ultraviolet (VUV) excitation. For the Y-Gd-Al ternary system, a compositional library was established to seek the optimal composition at which the highest luminescence under VUV (147 nm) excitation could be achieved. The Al content was found to mainly control the relative peak ratio (R/O) of red and orange colors due to the 5D 0→ 7F 2 to 5D 0→ 7F 1 transitions of Eu 3+. The substitution of Gd atoms in the place of Y sites did not contribute to change the R/O ratio, but was helpful to enhance the emission intensity. As a result, the 613 nm emission peak due to the 5D 0→ 7F 2 transitions of Eu 3+ was intensified by increasing the Al/Gd ratio at a fixed Y content, resulting in the improvement of the color coordinate. Finally, the optimized host composition was (Y 0.11, Gd 0.10, Al 0.79)BO 3 in terms of the emission intensity at 613 nm and the color coordinate.

SrMoO4:Er3+-Yb3+ upconverting phosphor for photonic and forensic applications

NASA Astrophysics Data System (ADS)

Soni, Abhishek Kumar; Rai, Vineet Kumar

2016-08-01

The Er3+-Yb3+ codoped strontium molybdate (SrMoO4) phosphors have been synthesized via chemical co-precipitation method by adding ammonium hydroxide as a base reagent. The phase, crystal structure and formation of spindle-like particles present in the prepared phosphors have been recognized by using the X-ray powder diffraction (XRPD) and Field emission scanning electron microscopy (FE-SEM) techniques. The Fourier transform infrared (FTIR) spectroscopy of the developed phosphors has been analyzed to mark the different functional groups present in synthesized phosphors. The multicolour upconversion emissions observed upon excitation with 980 nm and 808 nm laser diode have been explained on the basis of dopants ions concentration, pump power dependence, energy level structure and decay curve analysis. The colour co-ordinate study confirmed that the codoped phosphor emits non-tunable green colour when excited with the 980 nm laser diode, whereas it shows the colour tunability from yellow to green region upon excitation with the 808 nm laser diode. The applicability of non-tunable green colour emission has been demonstrated in the security ink and latent finger print detection. This shows the utility of the developed phosphors in the photonic and forensic applications.

Efficient non-doped phosphorescent orange, blue and white organic light-emitting devices.

PubMed

Yin, Yongming; Yu, Jing; Cao, Hongtao; Zhang, Letian; Sun, Haizhu; Xie, Wenfa

2014-10-24

Efficient phosphorescent orange, blue and white organic light-emitting devices (OLEDs) with non-doped emissive layers were successfully fabricated. Conventional blue phosphorescent emitters bis [4,6-di-fluorophenyl]-pyridinato-N,C(2')] picolinate (Firpic) and Bis(2,4-difluorophenylpyridinato) (Fir6) were adopted to fabricate non-doped blue OLEDs, which exhibited maximum current efficiency of 7.6 and 4.6 cd/A for Firpic and Fir6 based devices, respectively. Non-doped orange OLED was fabricated utilizing the newly reported phosphorescent material iridium (III) (pbi)₂Ir(biq), of which manifested maximum current and power efficiency of 8.2 cd/A and 7.8 lm/W. The non-doped white OLEDs were achieved by simply combining Firpic or Fir6 with a 2-nm (pbi)₂Ir(biq). The maximum current and power efficiency of the Firpic and (pbi)₂Ir(biq) based white OLED were 14.8 cd/A and 17.9 lm/W.

Efficient non-doped phosphorescent orange, blue and white organic light-emitting devices

NASA Astrophysics Data System (ADS)

Yin, Yongming; Yu, Jing; Cao, Hongtao; Zhang, Letian; Sun, Haizhu; Xie, Wenfa

2014-10-01

Efficient phosphorescent orange, blue and white organic light-emitting devices (OLEDs) with non-doped emissive layers were successfully fabricated. Conventional blue phosphorescent emitters bis [4,6-di-fluorophenyl]-pyridinato-N,C2'] picolinate (Firpic) and Bis(2,4-difluorophenylpyridinato) (Fir6) were adopted to fabricate non-doped blue OLEDs, which exhibited maximum current efficiency of 7.6 and 4.6 cd/A for Firpic and Fir6 based devices, respectively. Non-doped orange OLED was fabricated utilizing the newly reported phosphorescent material iridium (III) (pbi)2Ir(biq), of which manifested maximum current and power efficiency of 8.2 cd/A and 7.8 lm/W. The non-doped white OLEDs were achieved by simply combining Firpic or Fir6 with a 2-nm (pbi)2Ir(biq). The maximum current and power efficiency of the Firpic and (pbi)2Ir(biq) based white OLED were 14.8 cd/A and 17.9 lm/W.

A Unique Collection of Palaeolithic Painted Portable Art: Characterization of Red and Yellow Pigments from the Parpalló Cave (Spain)

PubMed Central

Villaverde Bonilla, Valentín; Ródenas Marín, Isabel; Murcia Mascarós, Sonia

2016-01-01

In this work we analyze the pigments used in the decoration of red and yellow motifs present in the portable art of the Parpalló Cave (Gandía, Spain), one of the most important Palaeolithic sites in the Spanish Mediterranean region. Energy dispersive X-ray fluorescence spectrometry (EDXRF) and spectrophotometry in the visible region (CIEL*a*b*color coordinates and spectral reflectance curves) were used to perform in situ fast analyses of the red and yellow motifs with portable equipment and to characterize their elemental composition and their colorimetric perception, respectively. According to the elemental composition, the intensity of the fluorescence iron signals in red and yellow motifs are higher than average values in the rock substrates. As expected, red motifs possess high values of the chromatic coordinate a* and yellow motifs possess high values of b*. This characterization was complemented with FT-IR analyses of microsamples detached from the red and yellow colored zones of a small set of plaquettes. Our results show that the artists used red and yellow pigments in the decoration likely derived from natural iron oxides as hematite and goethite. PMID:27732605

A Unique Collection of Palaeolithic Painted Portable Art: Characterization of Red and Yellow Pigments from the Parpalló Cave (Spain).

PubMed

Roldán García, Clodoaldo; Villaverde Bonilla, Valentín; Ródenas Marín, Isabel; Murcia Mascarós, Sonia

2016-01-01

In this work we analyze the pigments used in the decoration of red and yellow motifs present in the portable art of the Parpalló Cave (Gandía, Spain), one of the most important Palaeolithic sites in the Spanish Mediterranean region. Energy dispersive X-ray fluorescence spectrometry (EDXRF) and spectrophotometry in the visible region (CIEL*a*b*color coordinates and spectral reflectance curves) were used to perform in situ fast analyses of the red and yellow motifs with portable equipment and to characterize their elemental composition and their colorimetric perception, respectively. According to the elemental composition, the intensity of the fluorescence iron signals in red and yellow motifs are higher than average values in the rock substrates. As expected, red motifs possess high values of the chromatic coordinate a* and yellow motifs possess high values of b*. This characterization was complemented with FT-IR analyses of microsamples detached from the red and yellow colored zones of a small set of plaquettes. Our results show that the artists used red and yellow pigments in the decoration likely derived from natural iron oxides as hematite and goethite.

Doping-free white organic light-emitting diodes without blue molecular emitter: An unexplored approach to achieve high performance via exciplex emission

NASA Astrophysics Data System (ADS)

Luo, Dongxiang; Xiao, Ye; Hao, Mingming; Zhao, Yu; Yang, Yibin; Gao, Yuan; Liu, Baiquan

2017-02-01

Doping-free white organic light-emitting diodes (DF-WOLEDs) are promising for the low-cost commercialization because of their simplified device structures. However, DF-WOLEDs reported thus far in the literature are based on the use of blue single molecular emitters, whose processing can represent a crucial point in device manufacture. Herein, DF-WOLEDs without the blue single molecular emitter have been demonstrated by managing a blue exciplex system. For the single-molecular-emitter (orange or yellow emitter) DF-WOLEDs, (i) a color rendering index (CRI) of 81 at 1000 cd/m2 can be obtained, which is one of the highest for the single-molecular-emitter WOLEDs, or (ii) a high efficiency of 35.4 lm/W can be yielded. For the dual-molecular-emitter (yellow/red emitters) DF-WOLED, a high CRI of 85 and low correlated color temperature of 2376 K at 1000 cd/m2 have been simultaneously achieved, which has not been reported by previous DF-WOLEDs. Such presented findings may unlock an alternative avenue to the simplified but high-performance WOLEDs.

Carbonitride based phosphors and light emitting devices using the same

DOEpatents

Li, Yuanqiang; Tian, Yongchi; Romanelli, Michael Dennis

2013-08-20

Disclosed herein is a novel group of carbidonitride phosphors and light emitting devices which utilize these phosphors. In certain embodiments, the present invention is directed to a novel family of carbidonitride-based phosphors expressed as follows: Ca.sub.1-xAl.sub.x-xySi.sub.1-x+xyN.sub.2-x-xyC.sub.xy:A; (1) Ca.sub.1-x-zNa.sub.zM(III).sub.x-xy-zSi.sub.1-x+xy+zN.sub.2-x-xyC.sub.xy:- A; (2) M(II).sub.1-x-zM(I).sub.zM(III).sub.x-xy-zSi.sub.1-x+xy+zN.sub.2-x- -xyC.sub.xy:A; (3) M(II).sub.1-x-zM(I).sub.zM(III).sub.x-xy-zSi.sub.1-x+xy+zN.sub.2-x-xy-2w/- 3C.sub.xyO.sub.w-v/2H.sub.v:A; and (4) M(II).sub.1-x-zM(I).sub.zM(III).sub.x-xy-zSi.sub.1-x+xy+zN.sub.2-x-xy-2w/- 3-v/3C.sub.xyO.sub.wH.sub.v:A, (4a) wherein 0xy+z, and 0

Carotenoids and Carotenoid Esters of Red and Yellow Physalis (Physalis alkekengi L. and P. pubescens L.) Fruits and Calyces.

PubMed

Wen, Xin; Hempel, Judith; Schweiggert, Ralf M; Ni, Yuanying; Carle, Reinhold

2017-08-02

Carotenoid profiles of fruits and calyces of red (Physalis alkekengi L.) and yellow (P. pubescens L.) Physalis were characterized by HPLC-DAD-APCI-MS n . Altogether 69 carotenoids were detected in red Physalis, thereof, 45 were identified. In yellow Physalis, 40 carotenoids were detected and 33 were identified. Zeaxanthin esters with various fatty acids were found to be the most abundant carotenoids in red Physalis, accounting for 51-63% of total carotenoids, followed by β-cryptoxanthin esters (16-24%). In yellow Physalis, mainly free carotenoids such as lutein and β-carotene were found. Total carotenoid contents ranged between 19.8 and 21.6 mg/100 g fresh red Physalis fruits and 1.28-1.38 mg/100 g fresh yellow Physalis fruits, demonstrating that Physalis fruits are rich sources of dietary carotenoids. Yellow Physalis calyces contained only 153-306 μg carotenoids/g dry weight, while those of red Physalis contained substantially higher amounts (14.6-17.6 mg/g dry weight), thus possibly exhibiting great potential as a natural source for commercial zeaxanthin extraction.

Chinese yellow wine and red wine inhibit matrix metalloproteinase-2 and improve atherosclerotic plaque in LDL receptor knockout mice.

PubMed

Guo, Hangyuan; Liu, Longbin; Shi, Yafei; Sun, Aijing; Xu, Fukang; Chi, Jufang; Huang, Dilai

2010-06-01

Our previous study found that Chinese yellow wine could inhibit the production of homocysteine (HCY) induced extracellular matrix metalloproteinase-2 (MMP-2) in the cultured rat vascular smooth muscle cells. Little is known about the relationship between Chinese yellow wine and atherosclerosis or MMP-2 in vivo. Thirty-two LDL Receptor knockout mice on a high-fat and L-methionine diet developed plasma hyperhomocysteinemia and atherosclerosis. They were randomly divided into yellow wine group (n = 8), red wine group (n = 8), ethanol group (n = 8), and control group (n = 8), they were sacrificed after 14 weeks. There were no significant differences with plasma total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) levels in the four groups. Plasma HCY was significantly decreased in the yellow wine group compared to the other three groups (P < 0.01). Yellow wine and red wine groups significantly reduced the atherosclerosis lesion area compared to ethanol and control groups (P < 0.001). However, there was no significant discrepancy between the yellow wine group and red wine group. Compared to the control group and ethanol group, the production of MMP-2 reduced 26.8% and 23.6% in the aortic sinus and the activation of MMP-2 reduced 32.6% and 27.3% in the aortic arch in the yellow wine group; the production of MMP-2 reduced 25.7% and 22.4% in the aortic sinus and the activation of MMP-2 reduced 30.2% and 26.6% in the aortic arch in the red wine group. These results suggest that Chinese yellow wine and red wine can inhibit MMP-2 and improve atherosclerosis, and maybe both Chinese yellow wine and red wine have beneficial effects on cardiovascular disease by inhibiting MMP-2.

ZnCuInS/ZnSe/ZnS quantum dot-based downconversion light-emitting diodes and their thermal effect

DOE PAGES

Liu, Wenyan; Zhang, Yu; Wang, Dan; ...

2015-08-13

The quantum dot-based light-emitting diodes (QD-LEDs) were fabricated using blue GaN chips and red-, yellow-, and green-emitting ZnCuInS/ZnSe/ZnS QDs. The power efficiencies were measured as 14.0 lm/W for red, 47.1 lm/W for yellow, and 62.4 lm/W for green LEDs at 2.6 V. The temperature effect of ZnCuInS/ZnSe/ZnS QDs on these LEDs was investigated using CIE chromaticity coordinates, spectral wavelength, full width at half-maximum (FWHM) and power efficiencies (PE). The thermal quenching induced by the increased surface temperature of the device was confirmed to be one of the important factors to decrease power efficiencies while the CIE chromaticity coordinates changed littlemore » due to the low emission temperature coefficients of 0.022, 0.050 and 0.068 nm/°C for red-, yellow- and green-emitting ZnCuInS/ZnSe/ZnS QDs. Lastly this indicates that ZnCuInS/ZnSe/ZnS QDs are more suitable for down-conversion LEDs compared to CdSe QDs.« less

Phosphor suspended in silicone, molded/formed and used in a remote phosphor configuration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kolodin, Boris; Deshpande, Anirudha R

A light emitting package comprising a support hosting at least one light emitting diode. A light transmissive dome comprised of a silicone including a phosphor material positioned to receive light emitted by the diode. A glass cap overlies said dome.

Eu2+-doped Ba2GaB4O9Cl blue-emitting phosphor with high color purity for near-UV-pumped white light-emitting diodes

NASA Astrophysics Data System (ADS)

Gao, Zhiwen; Deng, Huajuan; Xue, Na; Jeong, Jung Hyun; Yu, Ruijin

2018-01-01

Eu2+-doped borate fluoride Ba2GaB4O9Cl was synthesized by the conventional high-temperature solid-state reaction. The crystal structure and luminescence properties of the phosphors, as well as their thermal luminescence quenching capabilities and CIE chromaticity coordinates were systematically investigated. Under the excitation at 340 nm, the phosphor exhibited an asymmetric broad-band blue emission with a peak at 445 nm, which is ascribed to the 4f-5d transition of Eu2+. It was further proved that energy transfer among the nearest neighbor ions is the major mechanism for concentration quenching of Eu2+ in Ba2-xGaB4O9Cl:xEu2+ phosphors. The luminescence quenching temperature is 432 K. The CIE color coordinates are very close to those of BaMgAl10O17:Eu2+ (BAM). All the properties indicated that the blue-emitting Ba2GaB4O9Cl:Eu2+ phosphor has potential application in white LEDs.

Phosphor-free, white-light LED under alternating-current operation.

PubMed

Yao, Yu-Feng; Chen, Hao-Tsung; Su, Chia-Ying; Hsieh, Chieh; Lin, Chun-Han; Kiang, Yean-Woei; Yang, C C

2014-11-15

A light-emitting diode structure, consisting of a p-GaN layer, a CdZnO/ZnO quantum-well (QW) structure, a high-temperature-grown ZnO layer, and a GaZnO layer, is fabricated. Under forward bias, the device effectively emits green-yellow light, from the QW structure, at the rim of device mesa. Under reverse bias, electrons in the valence band of the p-GaN layer move into the conduction band of the GaZnO layer, through a QW-state-assisted tunneling process, to recombine with the injected holes in the GaZnO layer, for emitting yellow-red and shallow ultraviolet light over the entire mesa area. Also, carrier recombination in the p-GaN layer produces blue light. By properly designing the thickness of the high-temperature grown ZnO layer, the emission intensity under forward bias can be controlled such that, under alternating-current operation at 60 Hz, the spatial and spectral mixtures of the emitted lights of complementary colors, under forward and reverse biases, result in white light generation based on persistence of vision.

Phase transition and multicolor luminescence of Eu{sup 2+}/Mn{sup 2+}-activated Ca{sub 3}(PO{sub 4}){sub 2} phosphors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Kai; Chen, Daqin, E-mail: dqchen@fjirsm.ac.cn; Xu, Ju

2014-01-01

Graphical abstract: We have synthesized Eu{sup 2+} doped and Eu{sup 2+}/Mn{sup 2+} co-doped Ca{sub 3}(PO{sub 4}){sub 2} phosphors. The emitting color varies from blue to green with increasing of Eu{sup 2+} content for the Eu{sup 2+}-doped phosphor, and the quantum yield of the 0.05Eu{sup 2+}: Ca{sub 2.95}(PO{sub 4}){sub 2} sample reaches 56.7%. Interestingly, Mn{sup 2+} co-doping into Eu{sup 2+}: Ca{sub 3}(PO{sub 4}){sub 2} leads to its phase transition from orthorhombic to rhombohedral, and subsequently generates tunable multi-color luminescence from green to red via Eu{sup 2+} → Mn{sup 2+} energy transfer. - Highlights: • A series of novel Eu{sup 2+}: Ca{submore » 3}(PO{sub 4}){sub 2} phosphors were successfully synthesized. • Phase transition of Ca{sub 3}(PO{sub 4}){sub 2} from orthorhombic to rhombohedral occurred when Mn{sup 2+} ions were doped. • The phosphors exhibited tunable multi-color luminescence. • The quantum yield of 0.05Eu{sup 2+}: Ca{sub 2.95}(PO{sub 4}){sub 2} phosphor can reach 56.7%. • The analyses of phosphors were carried out by many measurements. - Abstract: Intense blue-green-emitting Eu{sup 2+}: Ca{sub 3}(PO{sub 4}){sub 2} and tunable multicolor-emitting Eu{sup 2+}/Mn{sup 2+}: Ca{sub 3}(PO{sub 4}){sub 2} phosphors are prepared via a solid-state reaction route. Eu{sup 2+}-doped orthorhombic Ca{sub 3}(PO{sub 4}){sub 2} phosphor exhibits a broad emission band in the wavelength range of 400–700 nm with a maximum quantum yield of 56.7%, and the emission peak red-shifts gradually from 479 to 520 nm with increase of Eu{sup 2+} doping content. Broad excitation spectrum (250–420 nm) of Eu{sup 2+}: Ca{sub 3}(PO{sub 4}){sub 2} matches well with the near-ultraviolet LED chip, indicating its potential applications as tri-color phosphors in white LEDs. Interestingly, Mn{sup 2+} co-doping into Eu{sup 2+}: Ca{sub 3}(PO{sub 4}){sub 2} leads to its phase transition from orthorhombic to rhombohedral, and subsequently generates tunable multi

There's More to Color than Red, Yellow, and Blue

ERIC Educational Resources Information Center

Goobich, Joel

2009-01-01

From an early age, so much emphasis goes into teaching children the fundamentals of color theory, in particular the primary colors of red, yellow, and blue. Toys, building blocks, furniture, and so many other items used in a preschool environment are manufactured in these three colors. Yet, recent research has uncovered that babies as young as…

Photoluminescence and cathodoluminescence of Mn doped zinc silicate nanophosphors for green and yellow field emissions displays

NASA Astrophysics Data System (ADS)

Omri, K.; Alyamani, A.; Mir, L. El

2018-02-01

Mn2+-doped Zn2SiO4 (ZSM2+) was synthesized by a facile sol-gel technique. The obtained samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, photoluminescence (PL) and cathodoluminescence (CL) techniques. Under UV excitation, spectra showed that the α-ZSM2+ phosphor exhibited a strong green emission around 525 nm and reached the highest luminescence intensity with the Mn doping concentration of 5 at.%. However, for the β-ZSM2+ phase, an interesting yellow emission band centered at 575 nm of Mn2+ at the Zn2+ tetrahedral sites was observed. In addition, an unusual red shift with increasing Mn2+ content was also found and attributed to an exchange interaction between Mn2+. Both PL and CL spectra exhibit an intense green and yellow emission centered at 525 and 573 nm, respectively, due to the 4T1 (4G)-6A1 (6S) transition of Mn2+. Furthermore, these results indicated that the Mn2+-doped zinc silicate phosphors may have potential applications in green and yellow emissions displays like field emission displays (FEDs).

Antioxidant activity, phenolic and flavonoids total of ethanolic extract of Ipomoea batata L. leaves (white, yellow, orange, and purple)

NASA Astrophysics Data System (ADS)

Dewijanti, Indah Dwiatmi; Banjarnahor, Sofna D.; Triyuliani, Maryani, Faiza; Meilawati, Lia

2017-11-01

Antioxidant activity, phenolic and total flavonoids from sweet potato ethanol extract (Ipomea batatas L.) of different varieties (white, yellow, orange and purple) were studied. Sweet potatoes were collected from Research Centre for Chemistry. Sweet potato leaves have been used for numerous oxidative-associated diseases such as cancer, allergy, aging, HIV and cardiovascular. 1,1-diphenyl-2-picryl hydrazyl (DPPH) method was used to investigate antioxidant activity in leaves, in which the yellow and purple varieties showed the highest and the lowest scavenging activities of 47.65 µg/ ml (IC50) and 87.402 µg/ ml (IC50), respectively. In this study, the yellow leaves showed the highest concentrations of total phenolic and flavonoids contents at 11.293 µg/g and 44.963 µg/g, respectively. Therefore, sweet potato leaves can be used as a prospective natural antioxidant.

Organic Fluorescent Dyes Supported on Activated Boron Nitride: A Promising Blue Light Excited Phosphors for High-Performance White Light-Emitting Diodes

PubMed Central

Li, Jie; Lin, Jing; Huang, Yang; Xu, Xuewen; Liu, Zhenya; Xue, Yanming; Ding, Xiaoxia; Luo, Han; Jin, Peng; Zhang, Jun; Zou, Jin; Tang, Chengchun

2015-01-01

We report an effective and rare-earth free light conversion material synthesized via a facile fabrication route, in which organic fluorescent dyes, i.e. Rhodamine B (RhB) and fluorescein isothiocyanate (FITC) are embedded into activated boron nitride (αBN) to form a composite phosphor. The composite phosphor shows highly efficient Förster resonance energy transfer and greatly improved thermal stability, and can emit at broad visible wavelengths of 500–650 nm under the 466 nm blue-light excitation. By packaging of the composite phosphors and a blue light-emitting diode (LED) chip with transparent epoxy resin, white LED with excellent thermal conductivity, current stability and optical performance can be realized, i.e. a thermal conductivity of 0.36 W/mk, a Commission Internationale de 1'Eclairage color coordinates of (0.32, 0.34), and a luminous efficiency of 21.6 lm·W−1. Our research opens the door toward to the practical long-life organic fluorescent dyes-based white LEDs. PMID:25682730

Orange River, Africa

NASA Image and Video Library

1996-01-20

STS072-738-036 (11-20 Jan. 1996) --- The astronauts used a 70mm handheld camera to expose this frame of the west-flowing Orange River, which constitutes the international boundary between Namibia and the Republic of South Africa. The railroad and highway connecting the two countries is seen as a ribbon crossing the corner of the view. The broad color difference between strong browns/reds in the northern half of the view and lighter yellows in the southern corresponds to two land surfaces. The darker is a higher, flat land surface developed on horizontal Nama Sandstone’s, with rock surfaces widely coated with a dark manganese stain, typical of desert regions. This region is known as Namaqualand and borders the Namib Desert. Where rivers have cut down into this surface, the lighter underlying rock and soil colors show up.

Luminescence in microcrystalline green emitting Li2Mg1-xZrO4:xTb3+ (0.1 ≤ x ≤ 2.0) phosphor

NASA Astrophysics Data System (ADS)

Panse, V. R.; Kokode, N. S.; Shinde, K. N.; Dhoble, S. J.

2018-03-01

Green emitting Li2Mg1-xZrO4:xTb3+ (0.1 ≤ x ≤ 2.0) phosphor powders were synthesized via the wet chemical synthesis and the luminescent proprieties were studied when excited at 380 nm and present a dominant and strong green luminescence peak at 543 nm, due to D-F transition. The preparation of Li2Mg1-xZrO4:xTb3+ (0.1 ≤ x ≤ 2.0) phosphor powders were confirmed by X-ray diffraction (XRD) results without any secondary or impurity phases. The size and morphology of the Li2Mg1-xZrO4:xTb3+ (0.1 ≤ x ≤ 2.0) phosphor powders were further examined by scanning electron microscopy (SEM). Photoluminescence (PL) results have shown strongest green emission at 543 nm, which is originated due to 5D4-7F5 transition of Tb3+ ion, for the Li2Mg1-xZrO4:xTb3+ (0.1 ≤ x ≤ 2.0) phosphor. The addition of concentration Tb3+ was greatly improved the photoluminescence properties of present phosphors. The present study suggests that the Li2Mg1-xZrO4:xTb3+ (0.1 ≤ x ≤ 2.0) phosphor is a strong candidate as a green component for phosphor-converted white light-emitting diodes (LEDs).

Lutein and zeaxanthin supplied by red/orange foods and fruits are more closely associated with macular pigment optical density than those from green vegetables in Spanish subjects.

PubMed

Estévez-Santiago, Rocío; Olmedilla-Alonso, Begoña; Beltrán-de-Miguel, Beatriz; Cuadrado-Vives, Carmen

2016-11-01

Lutein and zeaxanthin (L+Z) accumulate in the retina. Although vegetables are major contributors to their intake, a stronger association between fruits and macular pigment optical density (MPOD) has been reported. We hypothesized that L+Z intake from fruits would have a stronger association with L+Z status markers (MPOD, serum concentrations) than intake from vegetables or eggs, and that those associations would also differ according to plant foods color. One hundred eight subjects (57 men; age groups, 20-35 and 45-65 years) were enrolled in a cross-sectional study. L+Z intake from fruits, vegetables, and eggs was determined using three 24-hour diet recalls and a country-specific carotenoid database. Vegetables were the major contributors (75%) to L+Z intake, followed by eggs (10%) and fruits (4%). Vegetables supplied 86% and 84% of the LandZ intake, respectively, and fruits supplied 3% and 16%. Green foods supplied 78% and 52% of LandZ, respectively, followed by red/orange (9% and 38%) and white/yellow (14% and 9%). Factorial analysis showed associations in older subjects. The explained variance of the first 2 principal components was 54% considering L+Z intake from fruits, vegetables, and eggs, and 55% considering L+Z intake from plant foods grouped by color. Macular pigment optical density is related to L+Z intake from fruits (0.264, P=.003) and is independent of that from vegetables and eggs. It is related to L+Z intake from red/orange foods (0.320, P=.000) and the serum concentrations to that from green foods (0.222, P=.11). Although vegetables and green foods of plant origin are the major contributors to L+Z intake, red/orange foods and fruits have the strongest relationship to MPOD in study participants (45-65 years of age). Copyright © 2016 Elsevier Inc. All rights reserved.

"Red-Yellow-Green": Effect of an Initiative to Guide Surgeon Choice of Orthopaedic Implants.

PubMed

Okike, Kanu; Pollak, Rachael; O'Toole, Robert V; Pollak, Andrew N

2017-04-05

Orthopaedic procedures are expensive, and devices account for a large proportion of the overall costs. Hospitals have employed a variety of strategies to decrease implant costs, but many center on restricting surgeon choice. At our institution, we developed an implant selection tool that guides surgeons toward more cost-effective implants, while minimally restricting choice. The purpose of this study was to assess the effect of this tool on preferred implant usage rates, vendor attitudes toward pricing structure, and hospital implant expenditures. For 6 commonly used orthopaedic trauma devices, similar constructs were created for the 4 vendors used at our hospital, and the costs were determined. On the basis of these costs, the available options for each device type were categorized as "green" (preferred vendor), "yellow" (midrange), or "red" (used for patient-specific requirements). The "Red-Yellow-Green" chart was posted on the wall of each orthopaedic trauma operating room. To assess the effect of the tool, we compared implant usage patterns before and after implementation of the implant selection tool. We also assessed changes in vendor contract prices, as well as overall savings to our institution. Implant usage changed significantly from 30% "red," 56% "yellow," and 14% "green" prior to the intervention, to 9% "red," 21% "yellow," and 70% "green" after the intervention (p < 0.0001). As a result of price renegotiation with vendors following implementation, we observed average price decreases that ranged from 1.1% to 22.4%. Average expenditures on these 6 implants decreased 20% during the study period, which represented a savings of $216,495 per year. At our institution, we designed and implemented "Red-Yellow-Green," a simple tool that guides surgeons toward the selection of lower-cost implants without violating vendor confidentiality clauses, limiting the implants from which surgeons can choose, or requiring surgeons to discern the prices of complex

Highly Efficient Spectrally Stable Red Perovskite Light-Emitting Diodes.

PubMed

Tian, Yu; Zhou, Chenkun; Worku, Michael; Wang, Xi; Ling, Yichuan; Gao, Hanwei; Zhou, Yan; Miao, Yu; Guan, Jingjiao; Ma, Biwu

2018-05-01

Perovskite light-emitting diodes (LEDs) have recently attracted great research interest for their narrow emissions and solution processability. Remarkable progress has been achieved in green perovskite LEDs in recent years, but not blue or red ones. Here, highly efficient and spectrally stable red perovskite LEDs with quasi-2D perovskite/poly(ethylene oxide) (PEO) composite thin films as the light-emitting layer are reported. By controlling the molar ratios of organic salt (benzylammonium iodide) to inorganic salts (cesium iodide and lead iodide), luminescent quasi-2D perovskite thin films are obtained with tunable emission colors from red to deep red. The perovskite/polymer composite approach enables quasi-2D perovskite/PEO composite thin films to possess much higher photoluminescence quantum efficiencies and smoothness than their neat quasi-2D perovskite counterparts. Electrically driven LEDs with emissions peaked at 638, 664, 680, and 690 nm have been fabricated to exhibit high brightness and external quantum efficiencies (EQEs). For instance, the perovskite LED with an emission peaked at 680 nm exhibits a brightness of 1392 cd m -2 and an EQE of 6.23%. Moreover, exceptional electroluminescence spectral stability under continuous device operation has been achieved for these red perovskite LEDs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photoluminescence properties of Tb3Al5O12:Ce3+ garnet synthesized by the metal organic decomposition method

NASA Astrophysics Data System (ADS)

Onishi, Yuya; Nakamura, Toshihiro; Adachi, Sadao

2017-02-01

Tb3Al5O12:Ce3+ garnet (TAG:Ce3+) phosphor was synthesized by the metal organic decomposition (MOD) method and subsequent calcination at Tc = 800-1200°C for 1 h in air. The effects of Ce3+ concentration on the phosphor properties were investigated in detail using X-ray diffraction (XRD) analysis, photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, and PL decay measurements. The maximum intensity in the Ce3+ yellow emission was observed at the Ce3+ concentration of ∼0.20%. PLE and PL decay measurements suggested an evidence of the energy transfer from Tb3+ to Ce3+. Calcination temperature dependence of the XRD and PL intensities yielded an energy of ∼1.5 eV both for the TAG formation in the MOD process and for the optical activation of Ce3+ in its lattice sites. Temperature dependences of the PL intensity for the TAG:Ce3+ yellow-emitting and K2SiF6:Mn4+ red-emitting phosphors were also examined for the future solid-state lighting applications at T = 20-500 K in 10-K steps. The data of TAG:Ce3+ were analyzed using a theoretical model with considering a reservoir level of Et ∼9 meV, yielding a quenching energy of Eq ∼0.35 eV, whereas the K2SiF6:Mn4+ red-emitting phosphor data yielded a value of Eq ∼1.0 eV. The schematic energy-level diagrams for Tb3+ and Ce3+ were proposed for the sake of a better understanding of these ions in the TAG host.

White organic light-emitting diodes with ultra-thin mixed emitting layer

NASA Astrophysics Data System (ADS)

Jeon, T.; Forget, S.; Chenais, S.; Geffroy, B.; Tondelier, D.; Bonnassieux, Y.; Ishow, E.

2012-02-01

White light can be obtained from Organic Light Emitting Diodes by mixing three primary colors, (i.e. red, green and blue) or two complementary colors in the emissive layer. In order to improve the efficiency and stability of the devices, a host-guest system is generally used as an emitting layer. However, the color balance to obtain white light is difficult to control and optimize because the spectrum is very sensitive to doping concentration (especially when a small amount of material is used). We use here an ultra-thin mixed emitting layer (UML) deposited by thermal evaporation to fabricate white organic light emitting diodes (WOLEDs) without co-evaporation. The UML was inserted in the hole-transporting layer consisting of 4, 4'-bis[N-(1-naphtyl)-N-phenylamino]biphenyl (α-NPB) instead of using a conventional doping process. The UML was formed from a single evaporation boat containing a mixture of two dipolar starbust triarylamine molecules (fvin and fcho) presenting very similar structures and thermal properties and emitting in complementary spectral regions (orange and blue respectively) and mixed according to their weight ratio. The composition of the UML specifically allows for fine tuning of the emission color despite its very thin thickness down to 1 nm. Competitive energy transfer processes from fcho and the host interface toward fvin are key parameters to control the relative intensity between red and blue emission. White light with very good CIE 1931 color coordinate (0.34, 0.34) was obtained by simply adjusting the UML film composition.

Sol-gel synthesis of red-phosphors [Na xGd 1-x/3-zEu z]Mo yW 1-yO 4 powers and luminescence properties

NASA Astrophysics Data System (ADS)

Cao, Fa-Bin; Li, Liao-Sha; Tian, Yan-Wen; Gao, Zhi-Fang; Chen, Yong-Jie; Xiao, Lin-Jiu; Wu, Xing-Rong

2011-04-01

In this work, we report on the sol-gel synthesis of red-phosphors [Na xGd 1-x/3-zEu z]Mo yW 1-yO 4 powders doped with several dopants and its luminescence properties at room temperature. X-ray diffraction patters indicated that red-phosphors powders present tetragonal symmetry and cubic structure. The red-phosphors [Na xGd 1-x/3-zEu z]Mo yW 1-yO 4 powders doped exhibit characteristic of a ultraviolet visible-light emission diode. The SEM images for [ NaGdEu0.043+]Mo 0.4W 0.6O 4 phosphor exhibits irregular morphology and cottonlike shape. The size of the particles is estimated to be about 1 μm. Luminescence properties showed that the maximum emission in red region lies in the arrange of 613 nm and 617 nm.

Structure and Luminescence Properties of New Green-Emitting Phosphor BaAl12O19:Tb

NASA Astrophysics Data System (ADS)

Xiao, Linjiu; He, Mingrui; Tian, Yanwen; Chen, Yongjie; Karaki, Tomoaki; Zhang, Liqing; Wang, Ning

2007-09-01

New green-emitting BaAl12O19:Tb phosphors were prepared by using the sol-gel method, and their structure and luminescence property were characterized by X-ray diffraction (XRD) analysis and fluorescence spectrometry. The results of XRD analysis revealed that a Ba1-xAl12O19:Tbx crystal structure was obtained at 1300 °C and Tb3+ ions substituted Ba2+ ions into the BaAl12O19 phase in the ion range x=0.005--0.05. The excitation peak of BaAl12O19:Tb was a wide band at approximately 240 nm, originating from the 4 f8-4 f75d1 transition of Tb3+. The emission spectrum consisted of eight emission peaks, originating from the 5D3-7Fi (i=6,5,4,3) and 5D4-7Fj ( j=6,5,4,3) transitions of Tb3+. The emission intensity of BaAl12O19:Tb phosphors at 543 nm was strongest when the phosphors were crystallized at 1300 °C for 2 h, and the content of Tb3+ was 2 mol %.

Luminescent properties of Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} and its potential application in white light emitting diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Zhijun, E-mail: wangzhijunmail@yahoo.com.cn; Li, Panlai; Li, Ting

2013-06-01

Graphical abstract: Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} phosphor can be effectively excited by an ultraviolet and near-ultraviolet light, and produce a bright blue emission centered at 436 nm. The CIE chromaticity coordinations (x, y) of Na{sub 2}CaSiO{sub 4}:Eu{sup 2+}(NSCE)/Li{sub 2}SrSiO{sub 4}:Eu{sup 2+}(LSSE) vary with the molar ratio of the two constituents. When NSCE/LSSE is 1:3, the CIE chromaticity coordination is (0.332, 0.346), which is close to that of the natural sunlight (0.33, 0.33). The results indicate that Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} may be a promising blue phosphor for UV chip-based multi-phosphor converted white light emitting diodes. Highlights: ► Na{sub 2}CaSiO{sub 4}:Eu{supmore » 2+} shows the blue emission with a peak at 436 nm and broad excitation band in the UV/n-UV range. ► White light with CIE coordinates (0.332, 0.346) is generated by mixing the blue phosphor with the Li{sub 2}SrSiO{sub 4}:Eu{sup 2+} yellow phosphor. ► Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} would be a promising blue phosphor candidate for UV chip-based multi-phosphor converted white LEDs. - Abstract: A novel blue phosphor Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} is synthesized by a high temperature solid-state reaction, and its luminescent properties are systematically studied. Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} can be effectively excited by the 354 nm radiation, and create blue emission (436 nm). The emission intensity of Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} is influenced by the Eu{sup 2+} doping content, and the optimal doping content is 1.5%, and the concentration quenching mechanism of Eu{sup 2+} in Na{sub 2}CaSiO{sub 4} can be attributed to the multipolar interaction. The white light with CIE coordinates (0.332, 0.346) is generated by mixing the blue phosphor Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} with the yellow phosphor Li{sub 2}SrSiO{sub 4}:Eu{sup 2+}. The results indicate that Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} may be a potential blue emitting phosphor for UV chip-based multi-phosphor

Color stable white phosphorescent organic light emitting diodes with red emissive electron transport layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wook Kim, Jin; Yoo, Seung Il; Sung Kang, Jin

2015-06-28

We analyzed the performance of multi-emissive white phosphorescent organic light-emitting diodes (PHOLEDs) in relation to various red emitting sites of hole and electron transport layers (HTL and ETL). The shift of the recombination zone producing stable white emission in PHOLEDs was utilized as luminance was increased with red emission in its electron transport layer. Multi-emissive white PHOLEDs including the red light emitting electron transport layer yielded maximum external quantum efficiency of 17.4% with CIE color coordinates (−0.030, +0.001) shifting only from 1000 to 10 000 cd/m{sup 2}. Additionally, we observed a reduction of energy loss in the white PHOLED via Ir(piq){submore » 3} as phosphorescent red dopant in electron transport layer.« less

Determination of ACC-induced cell-programmed death in roots of Vicia faba ssp. minor seedlings by acridine orange and ethidium bromide staining.

PubMed

Byczkowska, Anna; Kunikowska, Anita; Kaźmierczak, Andrzej

2013-02-01

Fluorescence staining with acridine orange (AO) and ethidium bromide (EB) showed that nuclei of cortex root cells of 1-aminocyclopropane-1-carboxylic acid (ACC)-treated Vicia faba ssp. minor seedlings differed in color. Measurement of resultant fluorescence intensity (RFI) showed that it increased when the color of nuclear chromatin was changed from green to red, indicating that EB moved to the nuclei via the cell membrane which lost its integrity and stained nuclei red. AO/EB staining showed that changes in color of the nuclear chromatin were accompanied by DNA condensation, nuclei fragmentation, and chromatin degradation which were also shown after 4,6-diamidino-2-phenylindol staining. These results indicate that ACC induced programmed cell death. The increasing values of RFI together with the corresponding morphological changes of nuclear chromatin were the basis to prepare the standard curve; cells with green unchanged nuclear chromatin were alive while those with dark orange and bright red nuclei were dead. The cells with nuclei with green-yellow, yellow-orange, and bright orange chromatin with or without their condensation and fragmentation chromatin were dying. The prepared curve has became the basis to draw up the digital method for detection and determination of the number of living, dying, and dead cells in an in planta system and revealed that ACC induced death in about 20% of root cortex cells. This process was accompanied by increase in ion leakage, shortening of cells and whole roots, as well as by increase in weight and width of the apical part of roots and appearance of few aerenchymatic spaces while not by internucleosomal DNA degradation.

FAST TRACK COMMUNICATION Host-free, yellow phosphorescent material in white organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Lee, Meng-Ting; Chu, Miao-Tsai; Lin, Jin-Sheng; Tseng, Mei-Rurng

2010-11-01

A white organic light-emitting diode (WOLED) with a high power efficiency has been demonstrated by dispersing a host-free, yellow phosphorescent material in between double blue phosphorescent emitters. The device performance achieved a comparable value to that of using a complicated host-guest doping system to form the yellow emitter in WOLEDs. Based on this device concept as well as the molecular engineering of blue phosphorescent host material and light-extraction film, a WOLED with a power efficiency of 65 lm W-1 at a practical brightness of 1000 cd m-2 with Commission Internationale d'Echariage coordinates (CIEx,y) of (0.37, 0.47) was achieved.

Discovery of a phosphor for light emitting diode applications and its structural determination, Ba(Si,Al)5(O,N)8:Eu2+.

PubMed

Park, Woon Bae; Singh, Satendra Pal; Sohn, Kee-Sun

2014-02-12

Most of the novel phosphors that appear in the literature are either a variant of well-known materials or a hybrid material consisting of well-known materials. This situation has actually led to intellectual property (IP) complications in industry and several lawsuits have been the result. Therefore, the definition of a novel phosphor for use in light-emitting diodes should be clarified. A recent trend in phosphor-related IP applications has been to focus on the novel crystallographic structure, so that a slight composition variance and/or the hybrid of a well-known material would not qualify from either a scientific or an industrial point of view. In our previous studies, we employed a systematic materials discovery strategy combining heuristics optimization and a high-throughput process to secure the discovery of genuinely novel and brilliant phosphors that would be immediately ready for use in light emitting diodes. Despite such an achievement, this strategy requires further refinement to prove its versatility under any circumstance. To accomplish such demands, we improved our discovery strategy by incorporating an elitism-involved nondominated sorting genetic algorithm (NSGA-II) that would guarantee the discovery of truly novel phosphors in the present investigation. Using the improved discovery strategy, we discovered an Eu(2+)-doped AB5X8 (A = Sr or Ba, B = Si and Al, X = O and N) phosphor in an orthorhombic structure (A21am) with lattice parameters a = 9.48461(3) Å, b = 13.47194(6) Å, c = 5.77323(2) Å, α = β = γ = 90°, which cannot be found in any of the existing inorganic compound databases.

Investigation of yellow emission from a co-polymer utilizable as an emitting material for white OLED

NASA Astrophysics Data System (ADS)

Akimoto, I.; Tsuzuki, S.; Uzawa, H.; Hinatsu, M.; Nishide, Y.; Osuga, H.; Sakamoto, H.

A novel co-polymer, P-PBTx, is a promising emitting material for white OLED. Appearance of unexpected yellow emission in EL is a key point, but its origin has not been clarified yet. Photo-luminescence properties of the copolymer were investigated in comparison with those of its monomer as well as two component molecules. An PL yellow band was also observed even in a film of a chromophore molecule at low temperature, depending on the position of an inhomogeneous film. Then, modified molecule center such as a dimer or an excimer of neighboring chromophores is a possible origin of the PL yellow emission. PACS: 33.50.Dq; 33.70.-w; 78.60.Fi;

Sol-hydrothermal synthesis and optical properties of Eu3+, Tb(3+)-codoped one-dimensional strontium germanate full color nano-phosphors.

PubMed

Lin, Liangwu; Sun, Xinyuan; Jiang, Yao; He, Yuehui

2013-12-21

Novel near-UV and blue excited Eu(3+), Tb(3+)-codoped one dimensional strontium germanate full-color nano-phosphors have been successfully synthesized by a simple sol-hydrothermal method. The morphologies, internal structures, chemical constitution and optical properties of the resulting samples were characterized using FE-SEM, TEM, HRTEM, EDS, XRD, FTIR, XPS, PL and PLE spectroscopy and luminescence decay curves. The results suggested that the obtained Eu(3+), Tb(3+)-codoped strontium germanate nanowires are single crystal nanowires with a diameter ranging from 10 to 80 nm, average diameter of around 30 nm and the length ranging from tens to hundreds micrometers. The results of PL and PLE spectra indicated that the Eu(3+), Tb(3+)-codoped single crystal strontium germanate nanowires showed an intensive blue, blue-green, green, orange and red or green, orange and red light emission under excitation at 350-380 nm and 485 nm, respectively, which may attributed to the coexistent Eu(3+), Eu(2+) and Tb(3+) ions, and the defects located in the strontium germanate nanowires. A possible mechanism of energy transfer among the host, Eu(3+) and Tb(3+) ions was proposed. White-emission can be realized in a single-phase strontium germanate nanowire host by codoping with Tb(3+) and Eu(3+) ions. The Eu(3+), Tb(3+)-codoped one-dimensional strontium germanate full-color nano-phosphors have superior stability under electron bombardment. Because of their strong PL intensity, good CIE chromaticity and stability, the novel 1D strontium germanate full-color nano-phosphors have potential applications in W-LEDs.

Apollo 17 "Orange soil" and meteorite impact on liquid lava

USGS Publications Warehouse

Roedder, E.; Weiblen, P.W.

1973-01-01

THE 'orange soil' from Shorty Crater differs greatly from ordinary lunar soils in that it consists of ???99% 10-300 ??m smooth shiny spherules and broken fragments of spherules of transparent orange glass, about 20% of which contain partly crystallized to opaque material. The remaining 1 % is chiefly crystalline basalt fragments. Although the colour of the individual orange spherule varies with thickness from yellow-orange to red-brown, all orange glass in our sample (74220, 70; 0.25 g) has a uniform index of refraction (??? 1.712). By contrast, other lunar soils contain spherules ranging from 1.50 to 1.75. The orange glass is also completely free of bubbles, to the limit of resolution of the light microscope, whereas bubbles are present in many other spherule samples. The spherules generally appear spherical in a normal microscope mount, but when viewed from two directions many are found to be oblate spheroids with axial ratios varying from near 1.00 to as low as 0.42 (Fig. 1a). Some have fissioned during free flight1 and all stages of the fission process are found, as described for the Apollo 11 samples. Only a few spherules seem to have been distorted by landing while still soft. One notable exception is the occurrence of small spherules of orange glass conforming and adhering to the surface of larger black spherules (Fig. 1b). ?? 1973 Nature Publishing Group.

Enhanced photoluminescence property and broad color emission of ZnGa2O4 phosphor due to the synergistic role of Eu3+ and carbon dots

NASA Astrophysics Data System (ADS)

Huo, Qiuyue; Tu, Weixia; Guo, Lin

2017-10-01

ZnGa2O4 phosphors co-composited with nanoscale carbon dots (CDs) and Eu3+ were presented for the tunable color emission. Novel single phase CDs or/and Eu3+ composited ZnGa2O4 phosphors were synthesized by microwave hydrothermal method and their optical properties were investigated. The ZnGa2O4 phosphors composited with CDs exhibited an intense broad blue light emission at 421 nm and a more enhanced photoluminescence intensity than those without CDs. The Eu3+ composited ZnGa2O4 phosphors gave an ideal red color emission. The CDs/Eu3+ co-composited ZnGa2O4 phosphors exhibited a wide emission band peak at 450 nm and narrow emission peak at 618 nm. Furthermore, the tunable color emissions of CDs/Eu3+ co-composited ZnGa2O4 phosphors from blue to the white light region, and then to red were obtained with the increasing Eu3+ concentration, which can be a promising single phased phosphor candidate in light emitting diodes. Broadly tunable emission single phased phosphor is tuned firstly through the synergistic role of the non-metal element and the rare earth metal ions.

Color-tunable properties of Eu3+- and Dy3+-codoped Y2O3 phosphor particles

PubMed Central

2012-01-01

Rare-earth phosphors are commonly used in display panels, security printing, and fluorescent lamps, and have potential applications in lasers and bioimaging. In the present study, Eu3+- and Dy3+-codoped uniform-shaped Y2O3 submicron particles were prepared using the urea homogeneous precipitation method. The structure and morphology of the resulting particles were characterized by X-ray diffraction, field emission scanning electron microscope, and field emission transmission electron microscope, whereas their optical properties were monitored by photoluminescence spectroscopy. The room-temperature luminescence color emission of the synthesized particles can be tuned from red to yellow by switching the excitation wavelength from 254 to 350 nm. The luminescence intensities of red and yellow emissions could be altered by varying the dopant concentration. Strong quenching was observed at high Eu3+ and Dy3+ concentrations in the Y2O3 host lattice. PMID:23043645

Kimzeyite garnet phosphors

DOEpatents

Lyons, Robert Joseph

2013-05-14

A phosphor of formula I is included in a phosphor composition in a lighting apparatus capable of emitting white light, Ca.sub.3-x-zSr.sub.xCe.sub.zM.sup.1.sub.2M.sup.2AlSiO.sub.12 (I) wherein M.sup.1 is Hf, Zr, or a combination thereof; M.sup.2 is Al, or a combination of Al and Ga; z<3-x; and 0.2>x.gtoreq.0. The lighting apparatus includes a semiconductor light source in addition to the phosphor composition.

Yellow Hypergiants as Dynamically Unstable Post-Red-supergiant Stars

NASA Technical Reports Server (NTRS)

Stothers, Richard B.; Chin, Chao-wen; Hansen, James E. (Technical Monitor)

2001-01-01

According to recent theoretical studies, the majority of single stars more massive than 30 solar mass successfully evolve into red supergiants, but then lose most of their hydrogen envelopes and metamorphose into hot blue remnants. While they are cool, they become dynamically unstable as a result of high radiation pressure and partial ionization of the gases in their outer layers. It is shown here that these unstable red-supergiant models repeatedly shrink and re-expand on a thermal time scale when perturbed by heavy bursts of mass loss. Consequently, they fill up the domain of yellow hypergiants on the Hertzsprung-Russell diagram and display very fast rates of evolution there, as observed.

Synthesis and photoluminescence properties of Dy{sup 3+} doped white light emitting CdTa{sub 2}O{sub 6} phosphors

DOE Office of Scientific and Technical Information (OSTI.GOV)

İlhan, Mustafa, E-mail: mustafa.ilhan@marmara.edu.tr; Ekmekçi, Mete Kaan

2015-03-15

The undoped and CdTa{sub 2}O{sub 6}:Dy{sup 3+} (0.2≤x≤2.0 mol%) phosphors were synthesized at 1100 °C for 12 h by the conventional solid state reaction method. The synthesized CdTa{sub 2}O{sub 6}:Dy{sup 3+} phosphors were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS) and Photoluminescence (PL) analyses. The PL spectra showed the presence of excitation peaks between 310 and 440 nm due to the 4f–4f transitions of Dy{sup 3+}. The emission of Dy{sup 3+} ions at 353.0 nm excitation was observed at 487.1 nm (blue) and 577.8 nm (yellow) due to the {sup 4}F{sub 9/2}→{sup 6}H{sub 15/2}more » transitions and {sup 4}F{sub 9/2}→{sup 6}H{sub 13/2} transitions, respectively. The PL analysis results also showed that the emissions increase with the increasing Dy{sup 3+} ion content. The emissions increased with the doping concentration of up to 1 mol%, and above this level decreased due to concentration quenching effect. The CIE chromaticity color coordinates (x,y) of the CdTa{sub 2}O{sub 6}:Dy{sup 3+} phosphors were found to be in the white light region of the chromaticity diagram. - Graphical abstract: Emission spectra at λ{sub ex}=353.0 nm and CIE chromaticity coordinate diagram of CdTa{sub 2}O{sub 6}:Dy{sup 3+} phosphors. - Highlights: • Pure and CdTa{sub 2}O{sub 6}:Dy{sup 3+} was produced by solid state reaction method. • CdTa{sub 2}O{sub 6}:Dy{sup 3+} phosphor exhibited blue and yellow emissions due to the {sup 4}F{sub 9/2}→{sup 6}H{sub 15/2} and {sup 4}F{sub 9/2}→{sup 6}H{sub 13/2} transitions. • The CCT value for 1.0 mol% CdTa{sub 2}O{sub 6}:Dy{sup 3+} was 5133 K which was located in the cool white daylight region. • Dy{sup 3+} doped CdTa{sub 2}O{sub 6} phosphor has potential in the production of white LEDs.« less

Cyclometalated Iridium(III) Carbene Phosphors for Highly Efficient Blue Organic Light-Emitting Diodes.

PubMed

Chen, Zhao; Wang, Liqi; Su, Sikai; Zheng, Xingyu; Zhu, Nianyong; Ho, Cheuk-Lam; Chen, Shuming; Wong, Wai-Yeung

2017-11-22

Five deep blue carbene-based iridium(III) phosphors were synthesized and characterized. Interestingly, one of them can be fabricated into deep blue, sky blue and white organic light-emitting diodes (OLEDs) through changing the host materials and exciton blocking layers. These deep and sky blue devices exhibit Commission Internationale de l'Éclairage (CIE) coordinates of (0.145, 0.186) and (0.152, 0.277) with external quantum efficiency (EQE) of 15.2% and 9.6%, respectively. The EQE of the deep blue device can be further improved up to 19.0% by choosing a host with suitable energy level of its lowest unoccupied molecular orbital (LUMO).

7 CFR 29.1043 - Orange (F).

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 2 2010-01-01 2010-01-01 false Orange (F). 29.1043 Section 29.1043 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Type 92) § 29.1043 Orange (F). A reddish yellow. [42 FR 21092, Apr. 25, 1977. Redesignated at 47 FR...

Enhanced photoluminescence of SrWO{sub 4}:Eu{sup 3+} red phosphor synthesized by mechanochemically assisted solid state metathesis reaction method at room temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peter, Anthuvan John, E-mail: quantajohn@gmail.com; Banu, I. B. Shameem

2015-06-24

Optically efficient europium activated alkaline earth metal tungstate nano phosphor (SrWO{sub 4}) with different doping concentrations have been synthesized by mechanochemically assisted solid state metathesis reaction at room temperature for the first time. The XRD and Raman spectra results indicated that the prepared powders exhibit a scheelite-type tetragonal structure. FTIR spectra exhibited a high absorption band situated at around 854 cm{sup −1}, which was ascribed to the W–O antisymmetric stretching vibrations into the [WO{sub 4}]{sup 2−} tetrahedron groups. Analysis of the emission spectra with different Eu{sup 3+} concentrations revealed that the optimum dopant concentration for SrWO{sub 4}: x Eu{sup 3+} phosphormore » is about 8 mol% of Eu{sup 3+}.The red emission intensity of the SSM prepared SrWO{sub 4}: 0.08Eu{sup 3+} phosphors are 2 times greater than that of the commercial Y{sub 2}O{sub 2}S: Eu{sup 3+} red phosphor prepared by the conventional solid state reaction method. All the results indicate that the phosphor is a promising red phosphor pumped by NUV InGaN chip for fabricating WLED.« less

A new orange emitting luciferase from the Southern-Amazon Pyrophorus angustus (Coleoptera: Elateridae) click-beetle: structure and bioluminescence color relationship, evolutional and ecological considerations.

PubMed

Amaral, Danilo T; Oliveira, Gabriela; Silva, Jaqueline R; Viviani, Vadim R

2016-08-31

Bioluminescent click-beetles display a wide variation of bioluminescence colors ranging from green to orange, including an unusual intra-specific color variation in the Jamaican Pyrophorus plagiophthalamus. Recently, we collected individuals of the Pyrophorus angustus species from the Southern Amazon forest, in Brazil, which displays an orange light emitting abdominal lantern. This species was also previously described from Central America, but displaying a bioluminescence spectrum from 536 nm (dorsal) to 578 nm (ventral). The biogeographic variation of the bioluminescence color in this species could be an adaptation to environmental reflectance and inter/intraspecific sexual competition. Here, we cloned, sequenced, characterized and performed site-direct mutagenesis of this new orange emitting luciferase. The in vitro luciferase spectrum displayed a peak at 594 nm, KM values for ATP and d-luciferin of 160 μM and 17 μM, respectively, and an optimum pH of approximately 8.5. Comparative multialignment and site-directed mutagenesis using different color emitting click-beetle luciferases from P. angustus, Fulgeochlizus bruchi and Pyrearinus termitilluminans luciferases cloned by our group showed an integral role of residue 247 in bioluminescence color modulation.

Enhancing the photovoltaic performance of CdTe/CdS solar cell via luminescent downshifting using K{sub 2}SiF{sub 6}:Mn{sup 4+} phosphors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Talewar, R. A., E-mail: talewarrupesh@gmail.com; Joshi, C. P.; Moharil, S. V.

2016-05-23

The efficiency of CdTe/CdS solar cell can be significantly improved by using luminescent down-shifting material on their front surface. Taking this into account a red emitting phosphor K{sub 2}Si{sub 1-x}F{sub 6}:xMn{sup 4+} (x=10 to 25 mol %) has been synthesized through wet chemical method. The as-synthesized materials were characterized by powder x-ray diffraction (XRD) and photoluminescence (PL) techniques. The photoluminescence studies of K{sub 2}SiF{sub 6}:Mn{sup 4+} revealed enhancement in the emission intensity, when Mn{sup 4+} concentration was increased from 10 mol % to 25 mol %. This red emitting phosphor efficiently absorbs the photons typically in the region 300-500 nmmore » and re-emits in the region where the photovoltaic device exhibits significantly better response. The results show the possibility of enhancing the photovoltaic conversion efficiency of CdTe thin film solar cell by modifying the absorption spectra and utilising the energy in the UV-blue part of the solar spectrum.« less

Origin of a counterintuitive yellow light-emitting electrochemical cell based on a blue-emitting heteroleptic copper(i) complex.

PubMed

Weber, Michael D; Garino, Claudio; Volpi, Giorgio; Casamassa, Enrico; Milanesio, Marco; Barolo, Claudia; Costa, Rubén D

2016-06-07

This work provides the synthesis, structural characterization, electrochemical and photophysical features, as well as the application in light-emitting electrochemical cells (LECs) of a novel heteroleptic copper(i) complex - [Cu(impy)(POP)][PF6], where impy is 3-(2-methoxyphenyl)-1-(pyridine-2-yl)imidazo[1,5-a]pyridine and POP is bis{2-(diphenylphosphanyl)phenyl}ether. This compound shows blue photoluminescence (PL, λ = 450 nm) in solution and solid-state and excellent redox stability. Despite these excellent features, the electroluminescence (EL) response is located at ∼550 nm. Although the EL spectrum of LECs is typically red-shifted compared to the PL of the electroluminescent material, a shift of ca. 100 nm represents the largest one reported in LECs. To date, the large shift phenomena have been attributed to (i) a change in the nature of the lowest emitting state due to a concentration effect of the films, (ii) a reversible substitution of the ligands due to the weak coordination to the Cu(i), and (iii) a change in the distribution of the excited states due to polarization effects. After having discarded these along with others like the irreversible degradation of the emitter during device fabrication and/or under operation conditions, driving conditions, active layer composition, and changes in the excited states under different external electrical stimuli, we attribute the origin of this unexpected shift to a lack of a thermally activated delayed fluorescence (TADF) process due to the solely ligand-centered character of the excited states. As such, the lack of a charge transfer character in the excited states leads to a blue-fluorescence and yellow-phosphorescence photo- and electro-responses, respectively. This corroborates recent studies focused on the design of TADF for heteroleptic copper(i) complexes. Overall, this work is a clear insight into the design of new copper(i) complexes towards the preparation of blue LECs, which are still unexplored.

Using the red/yellow/green discharge tool to improve the timeliness of hospital discharges.

PubMed

Mathews, Kusum S; Corso, Philip; Bacon, Sandra; Jenq, Grace Y

2014-06-01

As part of Yale-New Haven Hospital (Connecticut)'s Safe Patient Flow Initiative, the physician leadership developed the Red/Yellow/Green (RYG) Discharge Tool, an electronic medical record-based prompt to identify likelihood of patients' next-day discharge: green (very likely), yellow (possibly), and red (unlikely). The tool's purpose was to enhance communication with nursing/care coordination and trigger earlier discharge steps for patients identified as "green" or "yellow." Data on discharge assignments, discharge dates/ times, and team designation were collected for all adult medicine patients discharged in October-December 2009 (Study Period 1) and October-December 2011 (Study Period 2), between which the tool's placement changed from the sign-out note to the daily progress note. In Study Period 1, 75.9% of the patients had discharge assignments, compared with 90.8% in Period 2 (p < .001). The overall 11 A.M. discharge rate improved from 10.4% to 21.2% from 2007 to 2011. "Green" patients were more likely to be discharged before 11 A.M. than "yellow" or "red" patients (p < .001). Patients with RYG assignments discharged by 11 A.M. had a lower length of stay than those without assignments and did not have an associated increased risk of readmission. Discharge prediction accuracy worsened after the change in placement, decreasing from 75.1% to 59.1% for "green" patients (p < .001), and from 34.5% to 29.2% (p < .001) for "yellow" patients. In both periods, hospitalists were more accurate than house staff in discharge predictions, suggesting that education and/or experience may contribute to discharge assignment. The RYG Discharge Tool helped facilitate earlier discharges, but accuracy depends on placement in daily work flow and experience.

Layered Crystal Structure, Color-Tunable Photoluminescence, and Excellent Thermal Stability of MgIn2P4O14 Phosphate-Based Phosphors.

PubMed

Zhang, Jing; Cai, Ge-Mei; Yang, Lv-Wei; Ma, Zhi-Yuan; Jin, Zhan-Peng

2017-11-06

Single-component white phosphors stand a good chance to serve in the next-generation high-power white light-emitting diodes. Because of low thermal stability and containing lanthanide ions with reduced valence state, most of reported phosphors usually suffer unstable color of lighting for practical packaging and comparably complex synthetic processes. In this work, we present a type of novel color-tunable blue-white-yellow-emitting MgIn 2 P 4 O 14 :Tm 3+ /Dy 3+ phosphor with high thermal stability, which can be easily fabricated in air. Under UV excitation, the MgIn 2 P 4 O 14 :Tm 0.02 Dy 0.03 white phosphor exhibits negligible thermal-quenching behavior, with a 99.5% intensity retention at 150 °C, relative to its initial value at room temperature. The phosphor host MgIn 2 P 4 O 14 was synthesized and reported for the first time. MgIn 2 P 4 O 14 crystallizes in the space group of C2/c (No. 15) with a novel layered structure built of alternate anionic and cationic layers. Its disordering structure, with Mg and In atoms co-occupying the same site, is believed to facilitate the energy transfer between rare-earth ions and benefit by sustaining the luminescence with increasing temperature. The measured absolute quantum yields of MgIn 2 P 4 O 14 :Dy 0.04 , MgIn 2 P 4 O 14 :Tm 0.01 Dy 0.04 , and MgIn 2 P 4 O 14 :Tm 0.02 Dy 0.03 phosphors under the excitation of 351 nm ultraviolet radiation are 70.50%, 53.24%, and 52.31%, respectively. Present work indicates that the novel layered MgIn 2 P 4 O 14 is a promising candidate as a single-component white phosphor host with an excellent thermal stability for near-UV-excited white-light-emitting diodes (wLEDs).

Long Persistent Light Emitting Diode Indicators

ERIC Educational Resources Information Center

Jia, Dongdong; Ma, Yiwei; Hunter, D. N.

2007-01-01

An undergraduate laboratory was designed for undergraduate students to make long persistent light emitting diode (LED) indicators using phosphors. Blue LEDs, which emit at 465 nm, were characterized and used as an excitation source. Long persistent phosphors, SrAl[subscript 2]O[subscript 4]:Eu[superscript 2+],Dy[superscript 3+] (green) and…

The Preparation and Optical Properties of Novel LiLa(MoO4)2:Sm3+,Eu3+ Red Phosphor

PubMed Central

Luo, Li; Huang, Baoyu; He, Jingqi; Zhang, Wei; Zhao, Weiren; Wang, Jianqing

2018-01-01

Novel LiLa1−x−y(MoO4)2:xSm3+,yEu3+ (in short: LL1−x−yM:xSm3+,yEu3+) double molybdate red phosphors were synthesized by a solid-state reaction at as low temperature as 610 °C. The optimal doping concentration of Sm3+ in LiLa1−x(MoO4)2:xSm3+ (LL1−xM:xSm3+) phosphor is x = 0.05 and higher concentrations lead to emission quenching by the electric dipole—electric dipole mechanism. In the samples co-doped with Eu3+ ions, the absorption spectrum in the near ultraviolet and blue regions became broader and stronger than these of the Sm3+ single-doped samples. The efficient energy transfer from Sm3+ to Eu3+ was found and the energy transfer efficiency was calculated. Under the excitation at 403 nm, the chromaticity coordinates of LL0.95−yM:0.05Sm3+,yEu3+ approach to the NTSC standard values (0.670, 0.330) continuously with increasing Eu3+ doping concentration. The phosphor exhibits high luminous efficiency under near UV or blue light excitation and remarkable thermal stability. At 150 °C, the integrated emission intensity of the Eu3+ remained 85% of the initial intensity at room temperature and the activation energy is calculated to be 0.254 eV. The addition of the LL0.83M:0.05Sm3+,0.12Eu3+ red phosphors can improve the color purity and reduce the correlated color temperature of WLED lamps. Hence, LL1−x−yM:xSm3+,yEu3+ is a promising WLED red phosphor. PMID:29443910

The Preparation and Optical Properties of Novel LiLa(MoO4)2:Sm3+,Eu3+ Red Phosphor.

PubMed

Wang, Jiaxi; Luo, Li; Huang, Baoyu; He, Jingqi; Zhang, Wei; Zhao, Weiren; Wang, Jianqing

2018-02-14

Novel LiLa1-x-y(MoO4)2:xSm3+,yEu3+ (in short: LL1-x-yM:xSm3+,yEu3+) double molybdate red phosphors were synthesized by a solid-state reaction at as low temperature as 610 °C. The optimal doping concentration of Sm3+ in LiLa1-x(MoO4)2:xSm3+ (LL1-xM:xSm3+) phosphor is x = 0.05 and higher concentrations lead to emission quenching by the electric dipole-electric dipole mechanism. In the samples co-doped with Eu3+ ions, the absorption spectrum in the near ultraviolet and blue regions became broader and stronger than these of the Sm3+ single-doped samples. The efficient energy transfer from Sm3+ to Eu3+ was found and the energy transfer efficiency was calculated. Under the excitation at 403 nm, the chromaticity coordinates of LL0.95-yM:0.05Sm3+,yEu3+ approach to the NTSC standard values (0.670, 0.330) continuously with increasing Eu3+ doping concentration. The phosphor exhibits high luminous efficiency under near UV or blue light excitation and remarkable thermal stability. At 150 °C, the integrated emission intensity of the Eu3+ remained 85% of the initial intensity at room temperature and the activation energy is calculated to be 0.254 eV. The addition of the LL0.83M:0.05Sm3+,0.12Eu3+ red phosphors can improve the color purity and reduce the correlated color temperature of WLED lamps. Hence, LL1-x-yM:xSm3+,yEu3+ is a promising WLED red phosphor.

Luminescence in Ba2 Sr2 Al2 O7 :RE (RE = Tb(3) (+) ,Eu(3) (+) and Dy(3) (+) ) novel aluminate phosphors.

PubMed

Pardhi, S A; Panse, V R; Dhoble, S J

2016-09-01

The luminescence of novel rare earth (Tb(3) (+) , Eu(3) (+) and Dy(3) (+) )-activated Ba2 Sr2 Al2 O7 phosphors for solid-state lighting is presented. The aluminate phosphors were synthesized using a one-step combustion method. X-Ray diffraction, scanning electron microscopy and photoluminescence characterizations were performed to understand the mechanism of excitation and the corresponding emission in the as-prepared phosphor, as characterized the phase purity and microstructure. Improvements in the luminescence properties of the phosphors with rare earth concentration were observed. The phosphor hue could be tuned from blue, green and red by proper selection of rare earth ions in typical concentrations. Effective absorption in the near-ultraviolet region was observed, which makes the phosphor a potential candidate for ultraviolet light-emitting diodes. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Organic light-emitting diodes with direct contact-printed red, green, blue, and white light-emitting layers

NASA Astrophysics Data System (ADS)

Chen, Sun-Zen; Peng, Shiang-Hau; Ting, Tzu-Yu; Wu, Po-Shien; Lin, Chun-Hao; Chang, Chin-Yeh; Shyue, Jing-Jong; Jou, Jwo-Huei

2012-10-01

We demonstrate the feasibility of using direct contact-printing in the fabrication of monochromatic and polychromatic organic light-emitting diodes (OLEDs). Bright devices with red, green, blue, and white contact-printed light-emitting layers with a respective maximum luminance of 29 000, 29 000, 4000, and 18 000 cd/m2 were obtained with sound film integrity by blending a polymeric host into a molecular host. For the red OLED as example, the maximum luminance was decreased from 29 000 to 5000 cd/m2 as only the polymeric host was used, or decreased to 7000 cd/m2 as only the molecular host was used. The markedly improved device performance achieved in the devices with blended hosts may be attributed to the employed polymeric host that contributed a good film-forming character, and the molecular host that contributed a good electroluminescence character.

Highly Efficient Red and White Organic Light-Emitting Diodes with External Quantum Efficiency beyond 20% by Employing Pyridylimidazole-Based Metallophosphors.

PubMed

Miao, Yanqin; Tao, Peng; Wang, Kexiang; Li, Hongxin; Zhao, Bo; Gao, Long; Wang, Hua; Xu, Bingshe; Zhao, Qiang

2017-11-01

Two highly efficient red neutral iridium(III) complexes, Ir1 and Ir2, were rationally designed and synthesized by selecting two pyridylimidazole derivatives as the ancillary ligands. Both Ir1 and Ir2 show nearly the same photoluminescence emission with the maximum peak at 595 nm (shoulder band at about 638 nm) and achieve high solution quantum yields of up to 0.47 for Ir1 and 0.57 for Ir2. Employing Ir1 and Ir2 as emitters, the fabricated red organic light-emitting diodes (OLEDs) show outstanding performance with the maximum external quantum efficiency (EQE), current efficiency (CE), and power efficiency (PE) of 20.98%, 33.04 cd/A, and 33.08 lm/W for the Ir1-based device and 22.15%, 36.89 cd/A, and 35.85 lm/W for the Ir2-based device, respectively. Furthermore, using Ir2 as red emitter, a trichromatic hybrid white OLED, showing good warm white emission with low correlated color temperature of <2200 K under the voltage of 4-6 V, was fabricated successfully. The white device also realizes excellent device efficiencies with the maximum EQE, CE, and PE reaching 22.74%, 44.77 cd/A, and 46.89 lm/W, respectively. Such high electroluminescence performance for red and white OLEDs indicates that Ir1 and Ir2 as efficient red phosphors have great potential for future OLED displays and lightings applications.

A robust yellow-emitting metallophosphor with electron-injection/-transporting traits for highly efficient white organic light-emitting diodes.

PubMed

Zhou, Guijiang; Yang, Xiaolong; Wong, Wai-Yeung; Wang, Qi; Suo, Si; Ma, Dongge; Feng, Jikang; Wang, Lixiang

2011-10-24

With the aim of endowing triplet emitters in the development of organic light-emitting devices (OLEDs) with electron-injection/-transporting (EI/ET) features, the phenylsulfonyl moiety was introduced into the phenyl ring of a 2-phenylpyridine (Hppy) ligand and the yellow phosphorescent heteroleptic iridium(III) complex 1 was developed. It was shown that the SO(2)Ph unit could provide EI/ET character to 1, as indicated from both electrochemical and computational data. Complex 1 is a promising yellow-emitting material for both monochromatic OLEDs and white OLEDs (WOLEDs). The outstanding electronic traits associated with 1, coupled with careful device design, afforded very attractive electroluminescent performances for two-element WOLEDs, including a low turn-on voltage of less than 3.7 V, a maximum brightness of 48,000 cd m(-2), an external quantum efficiency of 13.0%, a luminance efficiency of 34.7 cd A(-1), and a power efficiency of 24.3 Lm W(-1). In addition, a good color rendering index (CRI) of about 74, a stable white color with a Commission Internationale de L'Eclairage (CIE(x,y)) variation of Δ(x, y) < ±(0.02, 0.02), and a correlated color temperature higher than 5130 K were obtained. These encouraging results indicate the potential of these WOLEDs as good candidates for warm indoor lighting sources, as well as the critical contribution of such key EI/ET properties to triplet emitters to advance new OLED research. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spectral downshifting from blue to near infer red region in Ce3+-Nd3+ co-doped YAG phosphor

NASA Astrophysics Data System (ADS)

Sawala, N. S.; Omanwar, S. K.

2016-07-01

The YAG phosphors co-doped with Ce3+-Nd3+ ions by varying concentration of Nd3+ ion from 1 mol% to 15 mol% were successfully synthesized by conventional solid state reaction method. The phosphors were characterized by powder X-ray powder diffraction (XRD) and surface morphology was studied by scanning electronic microscope (SEM). The photoluminescence (PL) properties were studied in near infra red (NIR) and ultra violet visible (UV-VIS) region. The synthesized phosphors can convert a blue region photon (453 nm) into photons of NIR region (1063 nm). The energy transfer (ET) process was studied by time decay curve and PL spectra. The theoretical value of energy transfer efficiency (ETE) was calculated from time decay luminescence measurement and the maximum efficiency approached up to 82.23%. Hence this phosphor could be prime candidate as a downshifting (DS) luminescent convertor (phosphor) in front of crystalline silicon solar cell (c-Si) panels to reduce thermalization loss in the solar cells.

HPLC-DAD-MS Profiling of Polyphenols Responsible for the Yellow-Orange Color in Apple Juices of Different French Cider Apple Varieties.

PubMed

Le Deun, Erell; Van der Werf, Remmelt; Le Bail, Gildas; Le Quéré, Jean-Michel; Guyot, Sylvain

2015-09-09

The pigments responsible for the yellow-orange coloration of apple juices have remained largely unknown up to now. Four French cider apple juices were produced in conditions similar to those used in the cider-making industry. The oxidized juices, characterized using the CIE L a b parameters, displayed various colors depending on the apple variety and native phenolic composition. HPLC-DAD-MS revealed contrasting pigment profiles related to oxidized tanning and nontanning molecules. The latter were divided into two groups according to their polarity and their visible spectra. With regard to phenolic classes, flavanol monomers and hydroxycinnamic acids played an essential role in the formation of oxidation products. Interestingly, dihydrochalcones appeared to include precursors of some yellow compounds. Indeed, the yellow pigment phloretin xyloglucoside oxidation product (PXGOPj), derived from phloretin xyloglucoside, was clearly identified in apple juices as a xyloglucose analogue of the yellow pigment phloridzin oxidation product (POPj), previously characterized in a model solution by Le Guernevé et al. (Tetrahedron Lett. 2004, 45 (35), 6673-6677).

White Light Emission from Planar Remote Phosphor Based on NHC Cycloplatinated Complexes.

PubMed

Fuertes, Sara; Chueca, Andrés J; Perálvarez, Mariano; Borja, Pilar; Torrell, Marc; Carreras, Josep; Sicilia, Violeta

2016-06-29

We report on the generation of bright white luminescence through solid-state illumination of remote phosphors based on novel cycloplatinated N-heterocyclic carbene (NHC) compounds. Following a stepwise protocol we got the new NHC compound [{Pt(μ-Cl)(C(∧)C*)}2] (4) (HC(∧)C*-κC* = 1-(4-(ethoxycarbonyl)phenyl)-3-methyl-1H-imidazol-2-ylidene), which was used together with the related ones 4a (HC(∧)C*-κC*= 1-(4-cyanophenyl)-3-methyl-1H-imidazol-2-ylidene) and 4b (HC(∧)C*-κC*= 3-methyl-1-(naphthalen-2-yl)-1H-imidazol-2-ylidene) as starting materials for the synthesis of the new ionic derivatives [Pt(R-C(∧)C*) (CNR')2]PF6 (R = -COOEt, R' = t-Bu (5), Xyl (6); R = -CN, R' = t-Bu (7), Xyl (8); R(∧)C = Naph, R' = t-Bu (9), Xyl (10)). The X-ray structures of 6 and 8-10 have been determined. The photophysical properties of these cationic compounds have been studied and supported by the time-dependent-density functional theory (TD-DFT) calculations. The compounds 5, 8, and 9 have been revealed as the most efficient emitters in the solid state with quantum yields of 41%, 21%, and 40%, respectively. White-light remote-phosphors have been prepared just by stacking different combinations of these compounds and [Pt(bzq) (CN) (CN(t)Bu)] (R1) as blue (5, 8), yellow (9), and red (R1) components onto the same substrate. The CCT (correlated color temperature) and the CRI (color rendering index) of the emitted white-light have been tuned by accurately controlling the individual contributions.

Luminescence study of Eu(3+) doped Li6 Y(BO3 )3 phosphor for solid-state lighting.

PubMed

Yawalkar, Mrunal M; Zade, G D; Dabre, K V; Dhoble, S J

2016-06-01

In this study, Li6 Y1-x Eux (BO3 )3 phosphor was successfully synthesized using a modified solid-state diffusion method. The Eu(3+) ion concentration was varied at 0.05, 0.1, 0.2, 0.5 and 1 mol%. The phosphor was characterized for phase purity, morphology, luminescent properties and molecular transmission at room temperature. The XRD pattern suggests a result closely matching the standard JCPDS file (#80-0843). The emission and excitation spectra were followed to discover the luminescence traits. The excitation spectra indicate that the current phosphor can be efficiently excited at 395 nm and at 466 nm (blue light) to give emission at 595 and 614 nm due to the (5) D0  → (7) Fj transition of Eu(3+) ions. Concentration quenching was observed at 0.5 mol% Eu(3+) in the Li6 Y1-x Eux (BO3 )3 host lattice. Strong red emission with CIE chromaticity coordinates of phosphor is x = 0.63 and y = 0.36 achieved with dominant red emission at 614 nm the (5) D0  → (7)  F2 electric dipole transition of Eu(3+) ions. The novel Li6 Y1-x Eux (BO3 )3 phosphor may be a suitable red-emitting component for solid-state lighting using double-excited wavelengths, i.e. near-UV at 395 nm and blue light at 466 nm. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Highly pure yellow light emission of perovskite CsPb(BrxI1-x)3 quantum dots and their application for yellow light-emitting diodes

NASA Astrophysics Data System (ADS)

He, Yuandan; Gong, Jinhui; Zhu, Yiyuan; Feng, Xingcan; Peng, Hong; Wang, Wei; He, Haiyang; Liu, Hu; Wang, Li

2018-06-01

High-quality all-inorganic perovskite CsPb(BrxI1-x)3 quantum dots (QDs) with quantum yield of 50% were systematically studied as yellow light convertor for light emitting diodes (LEDs). A novel heat insulation structure was designed for the QD-converted yellow LEDs. In this structure, a silicone layer was set on top of the GaN LED chip to prevent directly heating of the QDs by the LED chip. Then the CsPb(BrxI1-x)3 QDs were filled in the bowl-shaped silicone layer after ultrasonic dispersion treatment. Finally, an Al2O3 passivation layer was grown on the QDs layer by Atomic Layer Disposition at 40 °C. When x = 0.55, highly pure yellow LEDs with an emission peak at ∼570 nm and a full width at half maximum of 25 nm were achieved. The chromaticity coordinates of the QD-converted yellow LEDs (0.4920 ± 0.0017, 0.4988 ± 0.0053) showed almost no variation under driving current from 5 mA to 150 mA. During an operation period of 60 min, the emission wavelength of the yellow LEDs showed no distinct shift. Moreover, the luminous efficiency of the QD-converted yellow LEDs achieved 13.51 l m/W at 6 mA. These results demonstrated that CsPb(BrxI1-x)3 QDs and the heat insulation structure are promising candidate for high purity yellow LEDs.

High-Performance Blue-Excitable Yellow Phosphor Obtained from an Activated Solvochromic Bismuth-Fluorophore Metal–Organic Framework

DOE PAGES

Deibert, Benjamin J.; Velasco, Ever; Liu, Wei; ...

2016-06-23

Here, we report the synthesis, structure, and photoluminescence properties of a new bismuth based luminescent metal-organic framework (LMOF). The framework is comprised of a 9-coordinated Bi 3+ building unit and 4', 4''', 4''''', 4'''''''-(ethene-1,1,2,2-tetrayl)tetrakis([1,1'-biphenyl]-4-carboxylic acid) (H 4tcbpe) organic linker, which has strong yellow aggregation induced emission (AIE). The structure can be viewed as two interpenetrated 4,4-anionic nets that are stabilized by K + ions forming one-dimensional helical inorganic chains by connecting bismuth nodes through shared oxygen bonds. The as-made LMOF has a bluish emission centered at 459 nm with an internal quantum yield of 57% when excited at 360 nm.more » The emission properties of the LMOF were found to be highly solvochromic with respect to DMF. Upon partial solvent removal, the framework undergoes significant red-shifting to a greenish emission centered at 500 nm. Complete removal of DMF results in additional red-shifting fluorescence coupled with structural changes. The resulting material has strong blue-excitable (455 nm) yellow emission centered at 553 nm, with a quantum yield of 74%, which is maintained after heating in air for 5 days at 90°C. This is the second highest quantum yield value for blue-excited yellow emission among all reported LMOFs.« less

High-Performance Blue-Excitable Yellow Phosphor Obtained from an Activated Solvochromic Bismuth-Fluorophore Metal–Organic Framework

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deibert, Benjamin J.; Velasco, Ever; Liu, Wei

Here, we report the synthesis, structure, and photoluminescence properties of a new bismuth based luminescent metal-organic framework (LMOF). The framework is comprised of a 9-coordinated Bi 3+ building unit and 4', 4''', 4''''', 4'''''''-(ethene-1,1,2,2-tetrayl)tetrakis([1,1'-biphenyl]-4-carboxylic acid) (H 4tcbpe) organic linker, which has strong yellow aggregation induced emission (AIE). The structure can be viewed as two interpenetrated 4,4-anionic nets that are stabilized by K + ions forming one-dimensional helical inorganic chains by connecting bismuth nodes through shared oxygen bonds. The as-made LMOF has a bluish emission centered at 459 nm with an internal quantum yield of 57% when excited at 360 nm.more » The emission properties of the LMOF were found to be highly solvochromic with respect to DMF. Upon partial solvent removal, the framework undergoes significant red-shifting to a greenish emission centered at 500 nm. Complete removal of DMF results in additional red-shifting fluorescence coupled with structural changes. The resulting material has strong blue-excitable (455 nm) yellow emission centered at 553 nm, with a quantum yield of 74%, which is maintained after heating in air for 5 days at 90°C. This is the second highest quantum yield value for blue-excited yellow emission among all reported LMOFs.« less

Microfluidic White Organic Light-Emitting Diode Based on Integrated Patterns of Greenish-Blue and Yellow Solvent-Free Liquid Emitters

NASA Astrophysics Data System (ADS)

Kobayashi, Naofumi; Kasahara, Takashi; Edura, Tomohiko; Oshima, Juro; Ishimatsu, Ryoichi; Tsuwaki, Miho; Imato, Toshihiko; Shoji, Shuichi; Mizuno, Jun

2015-10-01

We demonstrated a novel microfluidic white organic light-emitting diode (microfluidic WOLED) based on integrated sub-100-μm-wide microchannels. Single-μm-thick SU-8-based microchannels, which were sandwiched between indium tin oxide (ITO) anode and cathode pairs, were fabricated by photolithography and heterogeneous bonding technologies. 1-Pyrenebutyric acid 2-ethylhexyl ester (PLQ) was used as a solvent-free greenish-blue liquid emitter, while 2,8-di-tert-butyl-5,11-bis(4-tert-butylphenyl)-6,12-diphenyltetracene (TBRb)-doped PLQ was applied as a yellow liquid emitter. In order to form the liquid white light-emitting layer, the greenish-blue and yellow liquid emitters were alternately injected into the integrated microchannels. The fabricated electro-microfluidic device successfully exhibited white electroluminescence (EL) emission via simultaneous greenish-blue and yellow emissions under an applied voltage of 100 V. A white emission with Commission Internationale de l’Declairage (CIE) color coordinates of (0.40, 0.42) was also obtained; the emission corresponds to warm-white light. The proposed device has potential applications in subpixels of liquid-based microdisplays and for lighting.

High efficiency yellow organic light-emitting diodes with optimized barrier layers

NASA Astrophysics Data System (ADS)

Mu, Ye; Zhang, Shiming; Yue, Shouzhen; Wu, Qingyang; Zhao, Yi

2015-12-01

High efficiency Iridium (III) bis (4-phenylthieno [3,2-c] pyridinato-N,C2‧) acetylacetonate (PO-01) based yellow organic light-emitting devices are fabricated by employing multiple emission layers. The efficiency of the device using 4,4‧,4″-tris(N-carbazolyl) triphenylamine (TCTA) as potential barrier layer (PBL) outperforms those devices based on other PBLs and detailed analysis is carried out to reveal the mechanisms. A forward-viewing current efficiency (CE) of 65.21 cd/A, which corresponds to a maximum total CE of 110.85 cd/A is achieved at 335.8 cd/m2 in the optimized device without any outcoupling enhancement structures.

Comparison of carotenoid accumulation and biosynthetic gene expression between Valencia and Rohde Red Valencia sweet oranges

USDA-ARS?s Scientific Manuscript database

Carotenoid accumulation and biosynthetic gene expression levels during fruit maturation were compared between ordinary Valencia (VAL) and its more deeply colored mutant Rohde Red Valencia orange (RRV). The two cultivars exhibited different carotenoid profiles and regulatory mechanisms in flavedo and...

Preparation and Characterization of Chromium(III)-Activated Yttrium Aluminum Borate: A New Thermographic Phosphor for Optical Sensing and Imaging at Ambient Temperatures

PubMed Central

2010-01-01

A new thermographic phosphor based on chromium(III)-doped yttrium aluminum borate (YAB) is obtained as single crystals by high temperature flux growth and as a microcrystalline powder via solution combustion synthesis. The phosphor is excitable both in the blue (λmax 422 nm) and in the red part of the spectrum (λmax 600 nm) and shows bright NIR emission. The brightness of the phosphor is comparable to that of a well-known lamp phosphor Mn(IV)-doped magnesium fluorogermanate. At ambient temperatures, the Cr(III)-doped YAB shows high temperature dependence of the luminescence decay time, which approaches 1% per deg. The material shows no decrease in luminescence intensity at higher temperatures. The new phosphor is particularly promising for applications in temperature-compensated optical chemosensors (including those based on NIR-emitting indicators) and in pressure-sensitive paints. PMID:20473368

Introducing Eu{sup 2+} into yellow phosphor LiBaB{sub 9}O{sub 15}:Ce{sup 3+}, Dy{sup 3+} as blue emitting source to realize white emission

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Ting; Li, Panlai, E-mail: li_panlai@126.com; Fu, Nian, E-mail: funian3678@163.com

A series of Dy{sup 3+}, Ce{sup 3+}/Dy{sup 3+}, Eu{sup 2+}/Dy{sup 3+} and Ce{sup 3+}/Eu{sup 2+}/Dy{sup 3+} doping LiBaB{sub 9}O{sub 15} (LBB) phosphors were synthesized via a high temperature solid-state method. LBB:Dy{sup 3+} cannot create light under ultraviolet radiation, however, LBB:Ce{sup 3+}, Dy{sup 3+} can produce yellow emission under 295 nm excitation. The energy transfer occurs from Ce{sup 3+} to Dy{sup 3+} ions via electric dipole-dipole interaction and the critical distance is estimated to be 21.15 Å based on concentration quenching model. Generally, Eu{sup 2+} ion is a sensitizer to Dy{sup 3+} ion, however, there is only the emission of Eu{supmore » 2+} in LBB:Eu{sup 2+}, Dy{sup 3+}, which means there is no energy transfer from Eu{sup 2+} to Dy{sup 3+} ions. Interestingly enough, when doping Eu{sup 2+} ion into LBB:Ce{sup 3+}, Dy{sup 3+}, white emission can be achieved by increase the blue (350–425 nm) emission intensity. The spectral property, quantum efficiency, CIE chromaticity coordinates and thermal quenching property of LBB:Ce{sup 3+}, Eu{sup 2+}, Dy{sup 3+} are investigated. The results indicate that LBB:Ce{sup 3+}, Eu{sup 2+}, Dy{sup 3+} may be a potential application to white light emitting diodes. - Graphical abstract: LBB:Ce{sup 3+}, Dy{sup 3+} can create white emission by doping Eu{sup 2+} ions. - Highlights: • LBB:Ce{sup 3+}, Dy{sup 3+} can produce white emission by doping Eu{sup 2+} ion. • There is no energy transfer from Eu{sup 2+} to Dy{sup 3+} ions. • Energy transfer occurs from Ce{sup 3+} to Dy{sup 3+} ions. • LBB:Ce{sup 3+}, Eu{sup 2+}, Dy{sup 3+} may be a potential application for white LEDs.« less

First-principle study of phosphors for white-LED applications : absorption and emission energies for Ce- and Eu-doped hosts.

NASA Astrophysics Data System (ADS)

Gonze, Xavier; Jia, Yongchao; Miglio, Anna; Giantomassi, Matteo; Ponce, Samuel; Mikami, Masayoshi

After the invasion of compact fluorescent lamps, white LED lighting is becoming a major contender in ecofriendly light sources, with a combination of yellow-, green- and/or red-emitting phosphors partly absorbing the blue light emitted by an InGaN LED. After introducing the semi-empirical Dorenbos model for 4f' 5d transition energies of rare earth ions, I present a first-principle study of two dozen compounds, pristine as well as doped with Ce3+ or Eu2+ ions, in view of explaining their different emission color. The neutral excitation of the ions is simulated through a constrained density functional theory method coupled with a delta SCF analysis of total energies, yielding absorption energies. Then, atomic positions in the excited state are relaxed, yielding emission energies and Stokes shifts, and identification of luminescent centers. In case of the Ce doped materials, the first-principle approach matches experimental data within 0.3 eV for both absorption and emission energies, covering a range of values between 2.0 eV and 5.0 eV, and provides Stokes shifts within 30%, with two exceptions. This is significantly better than the semi-empirical Dorenbos model. A similar analysis is performed for Eu-doped materials, also examining the thermal quenching of two oxynitride hosts. The work was supported by the FRS-FNRS Belgium (PDR Grant T.0238.13 - AIXPHO).

The Use of Light-Emitting Diodes (LEDs) as Green and Red/Far-Red Light Sources in Plant Physiology.

ERIC Educational Resources Information Center

Jackson, David L.; And Others

1985-01-01

The use of green, red, and far-red light-emitting diodes (LEDs) as light sources for plant physiological studies is outlined and evaluated. Indicates that LED lamps have the advantage over conventional light sources in that they are lightweight, low-cost, portable, easily constructed, and do not require color filters. (Author/DH)

Phosphor blends for high-CRI fluorescent lamps

DOEpatents

Setlur, Anant Achyut [Niskayuna, NY; Srivastava, Alok Mani [Niskayuna, NY; Comanzo, Holly Ann [Niskayuna, NY; Manivannan, Venkatesan [Clifton Park, NY; Beers, William Winder [Chesterland, OH; Toth, Katalin [Pomaz, HU; Balazs, Laszlo D [Budapest, HU

2008-06-24

A phosphor blend comprises at least two phosphors each selected from one of the groups of phosphors that absorb UV electromagnetic radiation and emit in a region of visible light. The phosphor blend can be applied to a discharge gas radiation source to produce light sources having high color rendering index. A phosphor blend is advantageously includes the phosphor (Tb,Y,LuLa,Gd).sub.x(Al,Ga).sub.yO.sub.12:Ce.sup.3+, wherein x is in the range from about 2.8 to and including 3 and y is in the range from about 4 to and including 5.

Dual color emitting Eu doped strontium orthosilicate phosphors synthesized by bio-template assisted ultrasound for solid state lightning and display applications.

PubMed

Venkataravanappa, M; Nagabhushana, H; Daruka Prasad, B; Darshan, G P; Basavaraj, R B; Vijayakumar, G R

2017-01-01

A novel Sr 2 SiO 4 :Eu (1-5mol %) superstructures (SS) were synthesized using bio-sacrificial A.V. gel assisted ultrasound method. Powder X-ray diffraction patterns confirmed the presence of both α and β phase formation. It was evident that the morphological growth was highly reliant on A.V. gel concentration, sonication time, pH and sonication power. The formation mechanisms for different hierarchical SS were proposed. From diffuse reflectance spectra, the energy band gap was estimated and found to be ∼4.70-5.11eV. The photoluminescence emission spectra for the excitation at 392nm, shows characteristic emission peaks at 593, 613, 654 and 702nm which were attributed to 5 D 0 → 7 F 0 , 7 F 1, 7 F 2 and 7 F 3 transitions of Eu 3+ ions respectively. Conversely, when the samples were subjected to the heat treatment at 850°C for 3h under argon atmosphere, display an intense broad emission peak with two de-convoluted peaks at 490 and 550nm due to 4f 6 5d 1 →4f 1 ( 8 S 7/2 ) transitions of Eu 2+ ions. The concentration quenching phenomenon was discussed which attributes to energy transfer, electron-phonon coupling and ion-ion interaction. The Judd-Ofelt intensity parameters and other radiative properties were estimated by using emission spectra. The CIE chromaticity coordinate values of Sr 2 SiO 4 :Eu 2+ and Eu 3+ nanophosphors were located in green and red regions respectively. The calculated CCT and CRI values specify that the present phosphor can be fairly useful for both green and red components of white LED's. Luminescence decay and quantum yield suggest the suitability of this phosphor as an efficient luminescent medium for light emitting diodes. Overall, the results elucidated a rapid, environmentally benign, cost-effective and convenient method for Sr 2 SiO 4 :Eu 3+ synthesis and for the possible applications such as solid state lighting and display devices. Copyright © 2016 Elsevier B.V. All rights reserved.

Fertilization Increases Growth of Sawlog-Size Yellow-Poplar and Red Oak in West Virginia

Treesearch

N. I. Lamson

1978-01-01

Sawlog-size even-aged hardwood stands in north-central West Virginia were fertilized with N, P, and K, singly and in combinations. Applications of N alone increased the annual basal area growth of yellow-poplar more than that of red oak during the first 7 years after fertilization, whereas P alone increased the annual basal area growth of red oak more than that of...

Phosphor thermometry system

DOEpatents

Beshears, David L.; Sitter, Jr., David N.; Andrews, William H.; Simpson, Marc L.; Abston, Ruth A.; Cates, Michael R.; Allison, Steve W.

2000-01-01

An apparatus for measuring the temperature of a moving substrate includes an air gun with a powder inlet port in communication with the outlet port of a powder reservoir, an air inlet port in communication with a pressurized air source, and an outlet nozzle spaced from and directed toward the moving substrate. The air gun is activated by the air pulses to spray controlled amounts of the powdered phosphor onto the moving substrate, where the phosphor assumes the temperature of the moving substrate. A laser produces light pulses, and optics direct the light pulses onto the phosphor on the moving substrate, in response to which the phosphor emits a luminescence with a decay rate indicative of the temperature of the phosphor. A collection lens is disposed to focus the luminescence, and a photodetector detects the luminescence focused by the collection lens and produces an electrical signal that is characteristic of the brightness of the luminescence. A processor analyzes the electrical signal to determine the decay characteristic of the luminescence and to determine the temperature of the phosphor from the decay characteristic.

Molten-salt synthesis and composition-dependent luminescent properties of barium tungsto-molybdate-based solid solution phosphors

NASA Astrophysics Data System (ADS)

Xiang-Hong, He; Zhao-Lian, Ye; Ming-Yun, Guan; Ning, Lian; Jian-Hua, Sun

2016-02-01

Pr3+-activated barium tungsto-molybdate solid solution phosphor Ba(Mo1-zWz)O4:Pr3+ is successfully fabricated via a facile molten-salt approach. The as-synthesized microcrystal is of truncated octahedron and exhibits deep-red-emitting upon blue light excitation. Powder x-ray diffraction and Raman spectroscopy techniques are utilized to investigate the formation of solid solution phosphor. The luminescence behaviors depend on the resulting composition of the microcrystals with fixed Pr3+-doping concentration, while the host lattices remain in a scheelite structure. The forming solid solution via the substitution of [WO4] for [MoO4] can significantly enhance its luminescence, which may be due to the fact that Ba(Mo1-zWz)O4:Pr3+ owns well-defined facets and uniform morphologies. Owing to its properties of high phase purity, well-defined facets, highly uniform morphologies, exceptional chemical and thermal stabilities, and stronger emission intensity, the resulting solid solution phosphor is expected to find potential applications in phosphor-converted white light-emitting diodes (LEDs). Project supported by the Construction Fund for Science and Technology Innovation Group from Jiangsu University of Technology, China, the Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, China (Grant No. KHK1409), the Priority Academic Program Development of Jiangsu Higher Education Institutions, China, and the National Natural Science Foundation of China (Grant No. 21373103).

Zero- and two-dimensional hybrid carbon phosphors for high colorimetric purity white light-emission.

PubMed

Ding, Yamei; Chang, Qing; Xiu, Fei; Chen, Yingying; Liu, Zhengdong; Ban, Chaoyi; Cheng, Shuai; Liu, Juqing; Huang, Wei

2018-03-01

Carbon nanomaterials are promising phosphors for white light emission. A facile single-step synthesis method has been developed to prepare zero- and two-dimensional hybrid carbon phosphors for the first time. Zero-dimensional carbon dots (C-dots) emit bright blue luminescence under 365 nm UV light and two-dimensional nanoplates improve the dispersity and film forming ability of C-dots. As a proof-of-concept application, the as-prepared hybrid carbon phosphors emit bright white luminescence in the solid state, and the phosphor-coated blue LEDs exhibit high colorimetric purity white light-emission with a color coordinate of (0.3308, 0.3312), potentially enabling the successful application of white emitting phosphors in the LED field.

The site occupation and valence of Mn ions in the crystal lattice of Sr{sub 4}Al{sub 14}O{sub 25} and its deep red emission for high color-rendering white light-emitting diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Lei, E-mail: shanggan2009@qq.com; Xue, Shaochan; Chen, Xiuling

2014-12-15

Highlights: • Different valences of Mn ions in Sr{sub 4}Al{sub 14}O{sub 25} were identified using XANES and EPR. • Red luminescence was attributed to Mn{sup 4+} occupying the center of AlO{sub 6} octahedron. • The Mn{sup 3+} incorporated in the center of AlO{sub 4} tetrahedron was non-luminescent. • The bond-valence theory was used to analyze the effective valences of cations. • A white LED device with CRI up to Ra 93.23 was packaged by using the red phosphor. - Abstract: The synthesis and component of red phosphor, Sr{sub 4}Al{sub 14}O{sub 25}: Mn, were optimized for application in white light-emitting diodes.more » The microstructure and morphology were investigated by the X-ray diffraction and scanning electron microscopy. Different valences of Mn ions in Sr{sub 4}Al{sub 14}O{sub 25} were discriminated using the electron paramagnetic resonance and X-ray absorption near-edge structure spectroscopy techniques. The bond-valence theory was used to analyze the effective valences of Sr{sup 2+} and Al{sup 3+} in Sr{sub 4}Al{sub 14}O{sub 25}. As a result, the strong covalence of Al{sup 3+} in the AlO{sub 4} tetrahedron other than in the AlO{sub 6} octahedron is disclosed. The deep red emission is attributed to Mn{sup 4+} occupying the center of AlO{sub 6} octahedron. The mechanism of energy transfer is mainly through dipole–dipole interaction, revealed by the analyses of critical distance and concentration quench. A high color rendering white LED prototype with color-rendering index up to Ra 93.23 packaged by using the red phosphor demonstrates its applicability.« less

Up-conversion white light of Tm 3+/Er 3+/Yb 3+ tri-doped CaF 2 phosphors

NASA Astrophysics Data System (ADS)

Cao, Chunyan; Qin, Weiping; Zhang, Jisen; Wang, Yan; Wang, Guofeng; Wei, Guodong; Zhu, Peifen; Wang, Lili; Jin, Longzhen

2008-03-01

Tm3+/Er3+/Yb3+ tri-doped CaF2 phosphors were synthesized using a hydrothermal method. The phosphors were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and up-conversion (UC) emission spectra. After annealing, the phosphors emitted white light under a 980 nm continuous wave diode laser (CW LD 2 W) excitation. As the excitation power density changed in the range of 20-260 W/cm2, the chromaticity coordinates of the UC light of the phosphor Ca0.885Tm0.005Er0.01Yb0.1F2 fell well in the white region of the 1931 CIE diagram. For the proportion of red, green and blue (RGB) in white light is strict, key factors for achieving UC white light, such as host materials, rare earth ions doping concentrations, annealing temperatures, as well as the excitation power densities, were investigated and discussed.

PileSort Module Usage

DTIC Science & Technology

2010-05-25

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Rare earth activated yttrium aluminate phosphors with modulated luminescence.

PubMed

Muresan, L E; Popovici, E J; Perhaita, I; Indrea, E; Oro, J; Casan Pastor, N

2016-06-01

Yttrium aluminate (Y3 A5 O12 ) was doped with different rare earth ions (i.e. Gd(3+) , Ce(3+) , Eu(3+) and/or Tb(3+) ) in order to obtain phosphors (YAG:RE) with general formula,Y3-x-a Gdx REa Al5 O12 (x = 0; 1.485; 2.97 and a = 0.03). The synthesis of the phosphor samples was done using the simultaneous addition of reagents technique. This study reveals new aspects regarding the influence of different activator ions on the morpho-structural and luminescent characteristics of garnet type phosphor. All YAG:RE phosphors are well crystallized powders containing a cubic-Y3 Al5 O12 phase as major component along with monoclinic-Y4 Al2 O9 and orthorhombic-YAlO3 phases as the impurity. The crystallites dimensions of YAG:RE phosphors vary between 38 nm and 88 nm, while the unit cell slowly increase as the ionic radius of the activator increases. Under UV excitation, YAG:Ce exhibits yellow emission due to electron transition in Ce(3+) from the 5d level to the ground state levels ((2) F5/2 , (2) F7/2 ). The emission intensity of Ce(3+) is enhanced in the presence of the Tb(3+) ions and is decreased in the presence of Eu(3+) ions due to some radiative or non-radiative processes that take place between activator ions. By varying the rare earth ions, the emission colour can be modulated from green to white and red. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Variability of Carotenoid Biosynthesis in Orange Colored Capsicum spp.

PubMed Central

Guzman, Ivette; Hamby, Shane; Romero, Joslynn; Bosland, Paul W.; O’Connell, Mary A.

2010-01-01

Pepper, Capsicum spp., is a worldwide crop valued for heat, nutrition, and rich pigment content. Carotenoids, the largest group of plant pigments, function as antioxidants and as vitamin A precursors. The most abundant carotenoids in ripe pepper fruits are β-carotene, capsanthin, and capsorubin. In this study, the carotenoid composition of orange fruited Capsicum lines was defined along with the allelic variability of the biosynthetic enzymes. The carotenoid chemical profiles present in seven orange pepper varieties were determined using a novel UPLC method. The orange appearance of the fruit was due either to the accumulation of β-carotene, or in two cases, due to only the accumulation of red and yellow carotenoids. Four carotenoid biosynthetic genes, Psy, Lcyb, CrtZ-2, and Ccs were cloned and sequenced from these cultivars. This data tested the hypothesis that different alleles for specific carotenoid biosynthetic enzymes are associated with specific carotenoid profiles in orange peppers. While the coding regions within Psy and CrtZ-2 did not change in any of the lines, the genomic sequence contained introns not previously reported. Lcyb and Ccs contained no introns but did exhibit polymorphisms resulting in amino acid changes; a new Ccs variant was found. When selectively breeding for high provitamin A levels, phenotypic recurrent selection based on fruit color is not sufficient, carotenoid chemical composition should also be conducted. Based on these results, specific alleles are candidate molecular markers for selection of orange pepper lines with high β-carotene and therefore high pro-vitamin A levels. PMID:20582146

Tunable color and energy transfer in single-phase white-emitting Ca{sub 20}Al{sub 26}Mg{sub 3}Si{sub 3}O{sub 68}:Ce{sup 3+},Dy{sup 3+} phosphors for UV white light-emitting diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuan, Bo; Song, Yanhua; Sheng, Ye

Ce{sup 3+} and/or Dy{sup 3+} activated Ca{sub 20}Al{sub 26}Mg{sub 3}Si{sub 3}O{sub 68} phosphors were synthesized by high temperature solid state reaction and their luminescent properties were studied. There are two emissions peaking at 407 and 577 nm in the emission spectra of Ca{sub 20}Al{sub 26}Mg{sub 3}Si{sub 3}O{sub 68}:Ce{sup 3+}, Dy{sup 3+}, which are due to the transitions of Ce{sup 3+} and Dy{sup 3+} ions, respectively. More importantly, the effective energy transfer from Ce{sup 3+} to Dy{sup 3+} ions has been confirmed and investigated by emission/excitation spectra and luminescent decay behaviors. Furthermore, the energy level scheme and mechanism of energy transfermore » were investigated and it was demonstrated to be resonant type via dipole–dipole reaction. Under the excitation of 345 nm, the emitting color can change from blue to white by adjusting the relative doping concentration of Ce{sup 3+} and Dy{sup 3+} ions, indicating that the phosphors Ca{sub 20}Al{sub 26}Mg{sub 3}Si{sub 3}O{sub 68}:Ce{sup 3+}, Dy{sup 3+} are promising single-phase white-emitting phosphors for application in pc-white LEDs. - Highlights: • The Ca{sub 20}Al{sub 26}Mg{sub 3}Si{sub 3}O{sub 68}:Ce{sup 3+},Dy{sup 3+} are novel luminescent materials that have not been reported before. • The crystal structure of Ca{sub 20}Al{sub 26}Mg{sub 3}Si{sub 3}O{sub 68} and energy transfer from Ce{sup 3+} to Dy{sup 3+} were investigated. • The emission color of Ca{sub 20}Al{sub 26}Mg{sub 3}Si{sub 3}O{sub 68}:Ce{sup 3+},Dy{sup 3+} can be adjusted from blue to white. • The phosphors have great application value in WLEDs as a kind of blue-to-white emitting phosphors.« less

Synthesis and Luminescence Properties of Blue Na(Sr0.97-xCa(x))PO4:0.03Eu2+ Phosphors for White Light Emitting Diode Applications.

PubMed

Hakeem, D A; Park, K

2015-07-01

The crystal structure and luminescence properties of Na(Sr0.97-xCax)PO4:0.03Eu2+ (0 < x < 1.0) phosphors were studied, depending on the Ca2+ concentration. All the Na(Sr0.97-xCax)PO4:0.03Eu2+ phosphors had a hexagonal crystal structure. The excitation spectra of the prepared phosphors showed a broad band ranging from 250 to 420 nm, which arises due to the 4f-5d transitions of Eu2+ ions. Upon the excitation of 334 nm wavelength, the emission spectra showed a broad blue band ranging from 400 to 700 nm peaking at 450 nm. Among the prepared phosphors, the Na(Sr0.72Ca0.25)PO4:0.03Eu2+ showed the strongest emission intensity and could be applied as a blue emitting phosphor for UV-based w-LEDs.

Controllable upconversion luminescence and temperature sensing behavior in NaGdF4:Yb3+/Ho3+/Ce3+ nano-phosphors

NASA Astrophysics Data System (ADS)

Pang, Tao; Wang, Jiajun

2018-01-01

The hexagonal NaGdF4:Yb3+/Ho3+/Ce3+ nano-phosphors are synthesized by a hydrothermal method. Under 980 nm excitation, the phosphor emits green, red and far-red light in the visible wavelength region, corresponding to the 5S2/5F4 → 5I8, 5F5 → 5I8 and 5S2/5F4 → 5I7 transitions of Ho3+ ions, respectively. When adjusting the Ce3+ concentration from 0% to 16%, the dominant wavelength shifts ˜43 nm toward the longer wavelength. Two cross-relaxation processes between Ho3+ and Ce3+ are responsible for the change in chromaticity. Also, the ability of the Ce3+ concentration to regulate the luminescence color depends on the pumping power and temperature of samples. More interestingly, the phosphors are potentially applicable as the optical thermometric materials. In the case of 16% Ce3+ doping, the maximum sensitivity (0.1446 K-1) about 4-35 times as high as the reported values of several typical thermometric materials is obtained.

Selection of reference genes for expression analyses of red-fleshed sweet orange (Citrus sinensis).

PubMed

Pinheiro, T T; Nishimura, D S; De Nadai, F B; Figueira, A; Latado, R R

2015-12-28

Red-fleshed oranges (Citrus sinensis) contain high levels of carotenoids and lycopene. The growing consumer demand for products with health benefits has increased interest in these types of Citrus cultivars as a potential source of nutraceuticals. However, little is known about the physiology of these cultivars under Brazilian conditions. Transcriptome and gene expression analyses are important tools in the breeding and management of red-fleshed sweet orange cultivars. Reverse transcription quantitative polymerase chain reaction is a method of quantifying gene expression, but various standardizations are required to obtain precise, accurate, and specific results. Among the standardizations required, the choice of suitable stable reference genes is fundamental. The objective of this study was to evaluate the stability of 11 candidate genes using various tissue and organ samples from healthy plants or leaves from citrus greening disease (Huanglongbing)-symptomatic plants of a Brazilian red-fleshed cultivar ('Sanguínea de Mombuca'), in order to select the most suitable reference gene for investigating gene expression under these conditions. geNorm and NormFinder identified genes that encoded translation initiation factor 3, ribosomal protein L35, and translation initiation factor 5A as the most stable genes under the biological conditions tested, and genes coding actin (ACT) and the subunit of the PSI reaction center subunit III were the least stable. Phosphatase, malate dehydrogenase, and ACT were the most stable genes in the leaf samples of infected plants.

Synthesis and luminescent properties of Sm3+ doped zinc aluminate phosphor

NASA Astrophysics Data System (ADS)

Mahajan, Rubby; Kumar, Sandeep; Prakash, Ram; Kumar, Vinay

2018-05-01

Zinc Aluminate (ZnAl2O4) is a well-known wide band gap oxide that belongs to a class of mixed-metal oxides knows as spinels (AB2O4) where A and B are divalent and trivalent cations. Herein, the structural and photoluminescence properties of Sm3+ ion doped with ZnAl2O4 phosphors are reported. The nanophosphors were synthesized via solution combustion synthesis route at temperature 570 °C. The synthesized samples were characterized by X-ray powder diffraction (XRD), Photoluminescence (PL) spectroscopy, and Ultraviolet-visible spectroscopy. The XRD pattern confirms the cubic phase of phosphor. The calculated lattice parameter were found as a = b = c = 8.0517Å and V = 521.85Å3. The crystallite size of the phosphor was calculated using the Debye-Scherrer formula and found to be ˜19 nm. The emission spectrum at excitation wavelength of 401 nm gave the emission peaks at 563 nm, 601 nm, 648 nm, 697 nm corresponding to the transitions 4G5/2→ 6H5/2, 4G5/2→6H7/2, 4G5/2→6H9/2, 4G5/2 → 6H11/2 of Sm3+ ions, respectively. The diffuse reflectance spectrum was used to calculate the band gap of material and found to be 5.12 eV. The CIE coordinates were found to be (x = 0.56, y = 0.40) that falls in the orange red region of the color gamut. The present phosphor may have potential applications as phosphor for near UV WLED for solid state lighting.

Orange a-plane InGaN/GaN light-emitting diodes grown on r-plane sapphire substrates.

PubMed

Seo, Yong Gon; Baik, Kwang Hyeon; Song, Hooyoung; Son, Ji-Su; Oh, Kyunghwan; Hwang, Sung-Min

2011-07-04

We report on orange a-plane light-emitting diodes (LEDs) with InGaN single quantum well (SQW) grown on r-plane sapphire substrates by metal organic chemical vapor deposition (MOCVD). The peak wavelength and the full-width at half maximum (FWHM) at a drive current of 20mA were 612.2 nm and 72 nm, respectively. The device demonstrated a blue shift in emission wavelength from 614.6 nm at 10 mA to 607.5 nm at 100 mA, representing a net shift of 7.1 nm over a 90 mA range, which is the longest wavelength compared with reported values in nonpolar LEDs. The polarization ratio values obtained from the orange LED varied between 0.36 and 0.44 from 10 to 100mA and a weak dependence of the polarization ratio on the injection current was observed.

Photoluminescence and afterglow luminescence properties of a green-emitting Na2BeGeO4:Mn2+ phosphor

NASA Astrophysics Data System (ADS)

Lu, Jie; Shen, Linjiang

2018-07-01

Recently, developing free rare-earth (RE) doped afterglow phosphors has received great attentions in the lighting field. In this work, we prepare and report a RE-free phosphor, Na2BeGeO4:Mn2+, which can simultaneously emit the green fluorescence and afterglow luminescence upon excitation at UV light. Our results reveal that the as-prepared samples crystallize in orthorhombic type with the space group of Pmn21 (31). The green emission is a broad band centered at 525 nm, corresponds to the 4T1(4G)-6A1(6S) transition of Mn2+ ions. After exposing to a 254 nm UV lamp for 10 min, the green afterglow luminescence seen with naked eyes can last more than 5 h. Together with the structural analysis and thermoluminescence (TL) spectra, the afterglow luminescence mechanism is also discussed in this work.

Preparation, characterization and luminescence properties of a new hydrous red phosphor CaB3 O5 (OH):Eu3+ with different morphologies.

PubMed

Huang, H S; Tang, A J; Yang, C; Jin, H F

2017-03-01

A new borate phosphor CaB 3 O 5 (OH):Eu 3 + with different morphologies was synthesized using a hydrothermal method and its luminescence properties were studied. The effects of surfactants on the crystal structures, morphologies and luminescence properties of the samples were studied. The results showed that the surfactants play an important role in controlling the morphology and improving the luminescence properties of phosphors. The luminescence intensity and R/O(I615/I592) value were enhanced for the prepared sample by adding PEG4000. The prepared sample exhibited a higher R/O than some anhydrous calcium borate phosphors, indicating that this product could serve as a new potential red phosphor. Copyright © 2016 John Wiley & Sons, Ltd.

Enhancement of red emission intensity of Ca2Al2SiO7:Eu3+ phosphor by MoO3 doping or excess SiO2 addition for application to white LEDs

NASA Astrophysics Data System (ADS)

Jiao, H. Y.; LiMao, C. R.; Chen, Q.; Wang, P. Y.; Cai, R. C.

2018-01-01

Ca1.86Al2(Si1-xMox)O7:0.14Eu3+ and Ca1.86Al2Si1+yO7+2y:0.14 Eu3+ were synthesized by solid-state reaction. X-ray powder diffraction, excitation and emission spectra were used to investigate their structures and photoluminescence properties. The results shows that the phosphor Ca1.86Al2SiO7:0.14Eu3+ cannot be excited efficiently by light of 393 nm. The introduced Mo ion does not change the position of the excitation peak, but increases both the absorption at 400nm and the emission intensity of Eu3+. The intense red emitting phosphor Ca1.86Al2(Si0.95Mo0.05)O7:0.14Eu3+ was obtained, which has 67% enhanced luminous intensity compared to that of the undoped sample Ca1.86Al2SiO7:0.14Eu3+. Otherwise, SiO2 excess of non-stoichiometric phosphors Ca1.86Al2Si1+yO7+2y:0.14Eu3+ showed the characteristic pattern of a tetragonal structure with a small SiO2 concentration. The optimal phosphor of Ca1.86Al2Si1.1O7.2:0.14Eu3+ has a luminous intensity about two times higher than that of the original stoichiometric phosphor Ca1.86Al2SiO7:0.14Eu3+. We confirmed that the photoluminescence intensity of the obtained phosphors is fairly enhanced by excessive SiO2. The mechanism of this photoluminescence enhancement is discussed in this paper.

Remarkable changes in the photoluminescent properties of Y2Ce2O7:Eu(3+) red phosphors through modification of the cerium oxidation states and oxygen vacancy ordering.

PubMed

Raj, Athira K V; Prabhakar Rao, P; Sreena, T S; Sameera, S; James, Vineetha; Renju, U A

2014-11-21

A new series of red phosphors based on Eu(3+)-doped yttrium cerate [Y1.9Ce2O7:0.1Eu(3+), Y2Ce1.9O7:0.1Eu(3+) and Y2Ce2-xO7:xEu(3+) (x = 0.05, 0.10, 0.15, 0.20, 0.25 and 0.50)] was prepared via a conventional solid-state method. The influence of the substitution of Eu(3+) at the aliovalent site on the photoluminescent properties was determined by powder X-ray diffraction, FT Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy with energy-dispersive spectroscopy, UV-visible absorption spectroscopy, photoluminescence spectroscopy and lifetime measurements. The substitution of Eu(3+) at the Ce(4+) site induces a structural transition from a defect fluorite to a C-type structure, which increases the oxygen vacancy ordering and the distortion of the Eu(3+) environment, and decreases the formation of Ce(3+) states. In contrast, phosphors with isovalent substitution at the Y(3+) site exhibit the biphasic nature of defect fluorite and a C-type structure, thereby increasing the number of Ce(3+) oxidation states. These modifications resulted in remarkable changes in the photoluminescent properties of Y2Ce1.9O7:0.1Eu(3+) red phosphors, with emission intensities 3.8 times greater than those of the Ce0.9O2:0.1Eu(3+) and Y1.9Ce2O7:0.1Eu(3+). The photoluminescent properties of Y2Ce2-xO7:xEu(3+) were studied at different Eu(3+) concentrations under excitation with blue light. These phosphors emit intense red light due to the (5)D0-(7)F2 transition under excitation at 466 nm and no concentration quenching is observed with up to 50 mol% Eu(3+). They show increased lifetimes in the range 0.62-0.72 ms at Eu(3+) concentrations. The cation ordering linked to the oxygen vacancy ordering led to the uniform distribution of Eu(3+) ions in the lattice, thus allowing higher doping concentrations without quenching and consequently increasing the lifetime of the (5)D0 states. Our results demonstrate that significant improvements in

Chemically modified maize cobs waste with enhanced adsorption properties upon methyl orange and arsenic.

PubMed

Elizalde-González, María P; Mattusch, J; Wennrich, R

2008-07-01

The surface chemistry of maize naturasorbent was altered in this work by the modifying agents: phosphoric acid and different amines (triethanolamine, diethylenetriamine and 1,4-diaminobutane). Removal of methyl orange (25 mg l(-1)) was <50% by maize corn cobs modified by phosphorylation and higher by the quaternized samples: 68% with the 1,4-diaminobutane and 73% with the diethylenetriamine modificators. Adsorption of arsenite by the samples modified with phosphoric acid/ammonia was 11 microg g(-1), which corresponds to 98% removal from a 550 microg As l(-1) solution for an adsorbent dose of 50 mg ml(-1). The samples modified by phosphoric acid/urea removed 0.4 microg g(-1) arsenate from a 300 mug As l(-1) solution. Adsorption of methyl orange, arsenite and arsenate was superior by the chemically modified maize cobs judged against the initial naturasorbent. For comparison, removal by the commercial anion exchanger was 100% for methyl orange, 45% (5 microg g(-1)) for arsenite and 99% (5 microg g(-1)) for arsenate.

Synthesis and photoluminescence characteristics of (Y,Gd)BO3:RE (RE = Eu(3+), Ce(3+), Dy(3+) and Tb(3+)) phosphors for blue chip and near-UV white LEDs.

PubMed

Rangari, V V; Singh, V; Dhoble, S J

2016-03-01

A series of Eu(3+)-, Ce(3+)-, Dy(3+)- and Tb(3+)-doped (Y,Gd)BO3 phosphors was synthesized by a solid-state diffusion method. X-Ray diffraction confirmed their hexagonal structure and the scanning electron microscopy results showed crystalline particles. The excitation spectra revealed that (Y,Gd)BO3 phosphors doped with Eu(3+), Ce(3+), Dy(3+) and Tb(3+) are effectively excited with near UV-light of 395 nm/blue light, 364, 351 and 314 nm, respectively. Photoluminescence spectra of Eu(3+)-, Ce(3+)- and Tb(3+)/Dy(3+)-doped phosphor showed intense emission of reddish orange, blue and white light, respectively. The phosphor Y0.60Gd0.38BO3:Ce0.02 showed CIE 1931 color coordinates of (0.158, 0.031) and better color purity compared with commercially available blue BAM:Eu(2+) phosphor. The phosphor (Y,Gd)BO3 doped with Eu(3+), Dy(3+) and Tb(3+) showed CIE 1931 color coordinates of (0.667, 0.332), (0.251, 0.299) and (0.333, 0.391) respectively. Significant photoluminescence characteristics of the prepared phosphors indicate that they might serve as potential candidates for blue chip and near-UV white light-emitting diode applications. Copyright © 2015 John Wiley & Sons, Ltd.

Novel Red-Emitting Ba₃Y(BO₃)₃:Bi3+, Eu3+ Phosphors for N-UV White Light-Emitting Diodes.

PubMed

Maggay, Irish Valerie B; Liu, Wei-Ren

2018-01-01

Ba3Y(BO3)3:Eu3+, Bi3+ were successfully prepared via a solid-state reaction. The crystallinity, photoluminescence properties, energy transfer and thermal quenching properties were studied. Subjecting Ba3Y(BO3)3:Bi3+ samples to different excitation wavelengths (340-370 nm), obtained blue and green emission ascribed to Bi3+(II) and Bi3+(I) sites, respectively. The influence of these two sites were systematically investigated. Bi3+ efficiently transferred its absorbed energy to neighboring Eu3+ sites by enhancing its luminescence intensity. Moreover, Bi3+ greatly enhanced the excitation spectra of Eu3+ in the N-UV region by 2.26 times which indicates that Ba3Y(BO3)3:Eu3+, Bi3+ can be used as a phosphor for w-LEDs using N-UV LED chips.

A colloidal quantum dot photonic crystal phosphor: nanostructural engineering of the phosphor for enhanced color conversion.

PubMed

Min, Kyungtaek; Jung, Hyunho; Park, Yeonsang; Cho, Kyung-Sang; Roh, Young-Geun; Hwang, Sung Woo; Jeon, Heonsu

2017-06-29

Phosphors, long-known color-converting photonic agents, are gaining increasing attention owing to the interest in white LEDs and related applications. Conventional material-based approaches to phosphors focus on obtaining the desired absorption/emission wavelengths and/or improving quantum efficiency. Here, we report a novel approach for enhancing the performance of phosphors: structural modification of phosphors. We incorporated inorganic colloidal quantum dots (CQDs) into a lateral one-dimensional (1D) photonic crystal (PhC) thin-film structure, with its photonic band-edge (PBE) modes matching the energy of 'excitation photons' (rather than 'emitted photons', as in most other PBE application devices). At resonance, we observed an approximately 4-fold enhancement of fluorescence over the reference bulk phosphor, which reflects an improved absorption of the excitation photons. This nano-structural engineering approach is a paradigm shift in the phosphor research area and may help to develop next-generation higher efficiency phosphors with novel characteristics.

Continuous tunable broadband emission of fluorphosphate glasses for single-component multi-chromatic phosphors.

PubMed

Zheng, Ruilin; Zhang, Qi; Yu, Kehan; Liu, Chunxiao; Ding, Jianyong; Lv, Peng; Wei, Wei

2017-10-15

A kind of Sn 2+ /Mn 2+ co-doped fluorphosphate (FP) glasses that served as single-component continuous tunable broadband emitting multi-chromatic phosphors are developed for the first time. Importantly, these FP glasses have high thermal conductivity (3.25-3.70  W/m·K) and good chemical stability in water (80°C). By combining with commercially available UV-LEDs directly, the emission colors can be tuned from blue/cold-white to warm-white/red through the energy transfer from Sn 2+ to Mn 2+ , and the broadband spectra covering the whole visible region from 380 nm to 760 nm. Notably, the FP glass can also serve as a white light phosphor by controlling the content of SnO/MnO, which has excellent optical properties. The CIE chromaticity coordinate, color rendering index, and quantum efficiency are (0.33, 0.29), 84, and 0.952, respectively. These new phosphors, possessing good optical and chemical properties, are promising for applications in solid-state lighting devices.

[The biological effects of a nuclear explosion. Introduction of a new system on a colorimetric scale (black, grey, red, orange, yellow and white zone) to estimate the effects of fall-out on civilian populations].

PubMed

Nacci, G

2002-08-01

Following September 11 the eventuality of terrorist attacks using bags containing nuclear devices is considered possible in western cities like New York, London, Paris, Rome, Berlin, Moscow etc. However, with a modern Civil Defence programme the effects of a catastrophe of this nature can be partially limited, at least as far as Fall-out is concerned. The present paper explains the medical reasons for building anti-fall-out shelters for the larger part of western populations: from the USA to Russia. The paper also sets out a new method for classifying levels of radioactive Fall-out based on a scale of colours (black, grey, red, orange, yellow and white) whatever kind of radioactivity is involved (total gamma levels, Cesium 137 levels, Strontium 90 levels). The arrival times for fall-out in each area of the scale are fixed, whatever the energy of the explosion and the speed of the wind might be. The radioactive decay in each area of the scale, from the time of arrival of the fall-out is described with precision. Also described are the acute radiation syndrome, tumours, miscarriages and genetic diseases. A nomogram is attached for civil defence purposes showing the leeward extension of these areas, easily measurable in just a few minutes, if four parameters are known: ground zero (locality) of the explosion, the energy of the explosion, the direction of the wind and the speed of the wind.

Controllable site occupation of Eu in intricate superstructure of perovskite Sr3Al2O6: Eu, Dy, Li to produce red luminescence

NASA Astrophysics Data System (ADS)

Zhu, Mei; Tian, Yunfei; Chen, Jie; Fei, Mi; He, Liangrui; Chen, Lei; Peng, Fang; Zhang, Qingli; Chan, Ting-Shan

An oxide red phosphor, with outstanding superiority in manufacturing cost, is particular desired for white light-emitting diodes (LEDs). In this work, a strategy to controllable site occupation of Eu in Sr3Al2O6 to give red light emission was employed with a three-step route: the combustion of sol-gel to prepare superfine precursor, the solid-sate reaction of precursor to incorporate Eu into small voids, and a second reduction in 25%H2+75%N2 atmosphere. Accordingly, a new red phosphor of Sr3Al2O6:Eu,Dy,Li was developed. The results shows the red luminescence of Sr3Al2O6:Eu could be improved by doping Dy3+ and be further improved by co-doping Li+. The red luminescence involves the 4f-5d transition of Eu2+ and the auto-ionization of electron from Eu2+ to conduction band. Dy3+ acts as a trap center of the thermally released electrons then with electrons returned to the 4f ground state of Eu2+, red light was emitted. The co-substitution of Sr2+-Sr2+ by Dy3+-Li+ is helpful to balance defects and improve crystallization.

Synthesis and luminescence properties of Sm3+ doped CaTiO3 nanophosphor for application in white LED under NUV excitation.

PubMed

Shivaram, M; Nagabhushana, H; Sharma, S C; Prashantha, S C; Daruka Prasad, B; Dhananjaya, N; Hari Krishna, R; Nagabhushana, B M; Shivakumara, C; Chakradhar, R P S

2014-07-15

CaTiO3:Sm(3+) (1-11 mol%) nanophosphors were successfully synthesized by a low temperature solution combustion method [LCS]. The structural and morphological properties of the phosphors were studied by using Powder X-ray diffractometer (PXRD), Fourier transform infrared (FTIR), X-ray photo electron spectroscopy (XPS), scanning electron microscope (SEM) and transmission electron microscopy (TEM). TEM studies indicate that the size of the phosphor is ∼20-35 nm. Photoluminescence (PL) properties of Sm(3+) (1-11 mol%) doped CaTiO3 for NUV excitation (407 nm) was studied in order to investigate the possibility of its use in White light emitting diode (WLED) applications. The emission spectra consists of intra 4f transitions of Sm(3+), such as (4)G5/2→(6)H5/2 (561 nm), (4)G5/2→(6)H7/2 (601-611 nm), (4)G5/2→(6)H9/2 (648 nm) and (4)G5/2→(6)H11/2 (703 nm) respectively. Further, the emission at 601-611 nm show strong orange-red emission and can be applied to the orange-red emission of phosphor for the application for near ultra violet (NUV) excitation. Thermoluminescence (TL) of the samples irradiated with gamma source in the dose range 100-500 Gy was recorded at a heating rate of 5°Cs(-1). Two well resolved glow peaks at 164°C and 214°C along with shouldered peak at 186°C were recorded. TL intensity increases up to 300 Gy and thereafter, it decreases with further increase of dose. The kinetic parameters namely activation energy (E), frequency factor (s) and order of kinetics were estimated and results were discussed in detail. Copyright © 2014 Elsevier B.V. All rights reserved.

Betalain, Acid Ascorbic, Phenolic Contents and Antioxidant Properties of Purple, Red, Yellow and White Cactus Pears

PubMed Central

Sumaya-Martínez, María Teresa; Cruz-Jaime, Sandra; Madrigal-Santillán, Eduardo; García-Paredes, Juan Diego; Cariño-Cortés, Raquel; Cruz-Cansino, Nelly; Valadez-Vega, Carmen; Martinez-Cardenas, Leonardo; Alanís-García, Ernesto

2011-01-01

Commercialization of cactus pears based on their antioxidant properties can generate competitive advantages, and these can turn into business opportunities and the development of new products and a high-value ingredient for the food industry. This work evaluated the antioxidant activities (1,1-diphenyl-2-picrylhydrazyl radical-scavenging, protection against oxidation of a β-carotene-linoleic acid emulsion, and iron (II) chelation), the content of total phenolic compounds, ascorbic acid, betacyanin, betaxanthin and the stability of betacyanin pigments in presence of Cu (II)-dependent hydroxyl radicals (OH•), in 18 cultivars of purple, red, yellow and white cactus pear from six Mexican states. Our results indicated that the antiradical activities from yellow and white cactus pear cultivars were not significantly different (p < 0.05) and were lower than the average antiradical activities in red and purple cultivars. The red cactus pear from the state of Zacatecas showed the highest antioxidant activity. The free radical scavenging activity for red cactus pears was significantly correlated (p < 0.05) to the concentration of total phenolic compounds (R2 = 0.90) and ascorbic acid (R2 = 0.86). All 18 cultivars of cactus pears studied showed significant chelating activity of ferrous ions. The red and purple cactus pears showed a great stability when exposed to OH•. PMID:22072899

DFT/TDDFT study on the photodissociation mechanism of the original monascus red and orange pigments

NASA Astrophysics Data System (ADS)

Liu, Yi; Wu, Li; Lv, Qingzhang

2015-06-01

The weak photostability has to some extent restricted the wide utilization of monascus pigments in food industries, and their photobleaching mechanism is unclear yet. Density functional theory and time-dependent density functional theory at B3LYP/6-311+G(d,p) level have been performed to optimize the geometries of ground states, single and triplet excited-states of the original monascus red and orange pigments, the possible photodissociation mechanism of which is analyzed according to the calculated data. It is the break of the chromophores, conjugated π bonds which has induced their decoloration. The photodissociation of these pigments involves three steps, excitation of the large conjugated π system, water addition to the singlet or triplet excited-state, and Norrish type I photochemical cleavage reactions of the side chains. The former two steps are much more important steps which have led to the destruction of the chromophores and the fading of the four original monascus red and orange pigments. According to the photobleaching mechanism obtained, one could find some solutions to enhance the photostability of these monascus colorants during the food processing process and extend the shelf life of the foods added with monascus pigments.

Modification of carotenoid levels by abscission agents and expression of carotenoid biosynthetic genes in 'valencia' sweet orange.

PubMed

Alferez, Fernando; Pozo, Luis V; Rouseff, Russell R; Burns, Jacqueline K

2013-03-27

The effect of 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP) and ethephon on peel color, flavedo carotenoid gene expression, and carotenoid accumulation was investigated in mature 'Valencia' orange ( Citrus sinensis L. Osbeck) fruit flavedo at three maturation stages. Abscission agent application altered peel color. CMNP was more effective than ethephon in promoting green-to-red (a) and blue-to-yellow (b) color at the middle and late maturation stages and total carotenoid changes at all maturation stages. Altered flow of carotenoid precursors during maturation due to abscission agents was suggested by changes in phytoene desaturase (Pds) and ζ-carotene desaturase (Zds) gene expression. However, each abscission agent affected downstream expression differentially. Ethephon application increased β-carotene hydroxilase (β-Chx) transcript accumulation 12-fold as maturation advanced from the early to middle and late stages. CMNP markedly increased β- and ε-lycopene cyclase (Lcy) transcript accumulation 45- and 15-fold, respectively, at midmaturation. Patterns of carotenoid accumulation in flavedo were supported in part by gene expression changes. CMNP caused greater accumulation of total flavedo carotenoids at all maturation stages when compared with ethephon or controls. In general, CMNP treatment increased total red carotenoids more than ethephon or the control but decreased total yellow carotenoids at each maturation stage. In control fruit flavedo, total red carotenoids increased and yellow carotenoids decreased as maturation progressed. Trends in total red carotenoids during maturation were consistent with measured a values. Changes in carotenoid accumulation and expression patterns in flavedo suggest that regulation of carotenoid accumulation is under transcriptional, translational, and post-translational control.

Preparation of balanced trichromatic white phosphors for solid-state white lighting.

PubMed

Al-Waisawy, Sara; George, Anthony F; Jadwisienczak, Wojciech M; Rahman, Faiz

2017-08-01

High quality white light-emitting diodes (LEDs) employ multi-component phosphor mixtures to generate light of a high color rendering index (CRI). The number of distinct components in a typical phosphor mix usually ranges from two to four. Here we describe a systematic experimental technique for starting with phosphors of known chromatic properties and arriving at their respective proportions for creating a blended phosphor to produce light of the desired chromaticity. This method is applicable to both LED pumped and laser diode (LD) pumped white light sources. In this approach, the radiometric power in the down-converted luminescence of each phosphor is determined and that information is used to estimate the CIE chromaticity coordinate of light generated from the mixed phosphor. A suitable method for mixing multi-component phosphors is also described. This paper also examines the effect of light scattering particles in phosphors and their use for altering the spectral characteristics of LD- and LED-generated light. This is the only approach available for making high efficiency phosphor-converted single-color LEDs that emit light of wide spectral width. Copyright © 2016 John Wiley & Sons, Ltd.

Yellow emitting Iridium (III) phenyl-benzothiazole complexes with different β-diketone ancillary ligands as dopants in white organic light-emitting diodes