White Emitting Research Articles

Improvement of Luminescence Properties of Eulytite Single-Phase White Emitting Ca3Bi (PO4)3: Ce3+/Dy3+ Phosphor.

To reduce the issue of tri-primary color reabsorption, a new approach for single-phase phosphors as light-emitting diodes (LEDs) has been recommended. The structures, morphology, photoluminescence, thermal stability, and luminescence mechanism of a variety of Ca3Bi (PO4)3 (CBPO): Ce3+/Dy3+ phosphors were investigated. XRD characterization showed that all CBPO samples were eulytite structures. Furthermore, the energy transfer process from Ce3+ to Dy3+ in CBPO is systematically investigated in this work, and the color of light can be adjusted by changing the ratio of doped ions. Under UV light, energy is transferred from Ce3+-Dy3+ mainly through quadrupole-quadrupole interactions in the CBPO host, and doping with different Dy3+ concentrations tunes the emission color from blue to white. The thermal stability of the CBPO: 0.04Ce3+, 0.08Dy3+ samples is outstanding, and the CIE coordinates of the samples after emission have little effect with temperature, while their emission intensity at 423 K is as strong as that at room temperature, reaching 90%. The above results indicate that this CBPO material has great potential as a white light phosphor under near-UV excitation at the optimized concentration of Ce3+ and Dy3+.

P‐11.2: Improved Stability and Brightness of CsPbX3 (X=Br, I) Nanocrystals for White Emitting

P‐11.2: Improved Stability and Brightness of CsPbX3 (X=Br, I) Nanocrystals for White Emitting

Synthesis and Photoluminescence Properties of White Emitting Alkaline Earth Chalcogenide Phosphors doped with Sn for Solid State Lighting

Sn2+ doped white emitting alkaline-earth chalcogenide CaS and SrS phosphors were synthesized by carbo-thermal reduction method. In this method special requirement such as H2S gas flow is not required as a source of sulphur and is comparatively easy method to prepare sulfides. The crystalline phase, morphology, and photoluminescence properties were characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), and fluorescence spectrophotometer, respectively. Phosphors exhibit broad band excitation which has excellent spread over nUV as well as blue region of visible light i.e. 440–480 nm. Emission is in the form of characteristic broad band of Sn2+ covering nUV and almost entire regions of visible spectrum i.e. 400–650 nm. The XRD pattern of prepared phosphor well matches with International Center for Diffraction Data. Synthesized phosphor particles are of different sizes, with smooth surfaces, from less than 1 micron to few microns. The chromaticity coordinates of synthesized phosphors have been calculated from its corresponding emission spectra monitored at their excitation wavelengths. They observed to falls in white region of CIE diagram. These points are close to standard white point D65, corresponding to daylight with correlated color temperature (CCT) 6500 °K, indicating better color purity of the synthesized phosphor and they are promising material for a color converter using blue LED as the primary light (pumping) source in phosphor converted white LED (pc wLED) for solid state lighting.

Near White Emitting Host Sensitized Dy3+ doped GdPO4 Nanoparticles: Luminescence Studies

Host sensitized GdPO4 nanoparticles doped with Dy3+ ions have been prepared by co-precipitation method with ethylene glycol as capping agent as well as solvent. The as-prepared samples exhibit crystalline monoclinic phase of GdPO4. From the luminescence study, 4F9/2→6H15/2 of Dy3+ is dominant over 4F9/2→6H13/2 transition indicating the occupation of inversion symmetry by Dy3+ ions in the host lattice. The steady state luminescence shows effective energy transfer from gadolinium (Gd3+) to dysprosium (Dy3+) ions in the doped samples with optimum emission of Dy3+ (2 at.%) doped sample. Decay lifetime values also decrease upon increasing Dy3+ ion concentration on account of cross-relaxation concentration quenching effect. The emission colour of single phase as-prepared Dy3+ doped GdPO4 nanoparticles can be tuned from blue-violet to near white light by changing the excitation wavelength. Tunability of the light and white light emission are supported by Commission Internationale de l’Eclairage (CIE) chromaticity.

Li+ Ion Induced Full Visible Emission in Single Eu2+‐Doped White Emitting Phosphor: Eu2+ Site Preference Analysis, Luminescence Properties, and WLED Applications

AbstractA series of Eu2+ single doped Ca9Na1–xLixSc0.667(PO4)7 phosphors with full‐spectrum emission have been synthesized. Under the 385 nm excitation, the Eu2+ single doped Ca9NaSc0.667(PO4)7 without Li+ doping displays a broad cold white light emission with the peaks at about 480 and 610 nm. With the introduction of Li+ ions, the Eu2+ ions selectively occupy the Ca1, Ca2/Ca3, and Na sites. The variation of local environment of Eu2+ ions caused by Li+ ions enhances the luminous intensity, solves the problem of the lack of a red light component, and realizes the emission color tuning from cold white via warm white to orange. A special charge compensation method caused by Li+ migration avoids the generation of defects and is beneficial to the improvement of luminescence properties. Eventually, a warm white light‐emitting diode device is prepared by combining the white emitting Ca9Na0.8Li0.2Sc0.667(PO4)7:2%Eu2+ phosphors with 385 nm LED chip, which exhibits a high color‐rendering of 92.9, low correlated color temperatures of 4529 K, and excellent color stability under working temperature. The as‐reported warm white emitting Eu2+‐doped phosphors have potential applications in full‐spectrum solid‐state lighting. The site engineering strategy provides an extensive guide for optimizing and designing novel single‐composition white‐emitting phosphor materials.

Dy3+ Activated Nearly White Emitting NaCdPO4 as Potential Phosphors for Solid State Light Applications

A series of phosphate based phosphors NaCd1−xPO4: xDy3+(x = 0.02–0.1) are prepared by adopting conventional solid state reaction routes. The prepared phosphors are well characterized by x-ray diffraction to establish the phase purity while a field emission scanning electron microscope is used to detect the microstructure. The surface chemical composition, an important aspect of this work, is established by x-ray photoelectron spectroscopy. The photoluminescence excitation spectra are recorded at room temperature, in which the excitation maxima are observed at 347 nm, indicating a near ultraviolet (UV) excitation which can be useful for light emitting diodes with a UV chip. The emission spectra show three major emission lines at 480 nm (4F9/2 → 6H15/2) a blue emission, a yellow emission around 570 nm (4F9/2 → 6H13/2) and a red emission around 662 nm (4F9/2 → 6H11/2). The CIE 1931 color chromaticity diagram shows the color coordinates around (0.32, 0.31) and such phosphors can be useful for solid state lighting applications as the emission spectrum lies in the near white region in the color space.

White Light Phosphors: A Nonrare‐Earth Ions Self‐Activated White Emitting Phosphor under Single Excitation (Adv. Funct. Mater. 44/2015)

White Light Phosphors: A Nonrare‐Earth Ions Self‐Activated White Emitting Phosphor under Single Excitation (Adv. Funct. Mater. 44/2015)

A Non‐rare‐Earth Ions Self‐Activated White Emitting Phosphor under Single Excitation

White light phosphors have many potential applications such as solid‐state lighting, full color displays, light source for plant growth, and crop improvement. However, most of these phosphors are rare‐earth‐based materials which are costly and would be facing the challenge of resource issue due to the extremely low abundance of these elements on earth. A new white color composite consisted of a graphitic‐phase nitrogen carbon (g‐C3N4) treated with nitric acid and copper‐cysteamine Cu3Cl(SR)2 is reported herein. Under a single wavelength excitation at 365 nm, these two materials show a strong blue and red luminescence, respectively. It is interesting to find that the white light emission with a quantum yield of 20% can be obtained by mixing these two self‐activated luminescent materials at the weight ratio of 1:1.67. Using a 365 nm near‐ultraviolet chip for excitation, the composite produces a white light‐emitting diode that exhibits an excellent color rendering index of 94.3. These white‐emitting materials are environment friendly, easy to synthesize, and cost‐effective. More importantly, this will potentially eliminate the challenge of rare earth resources. Furthermore, a single chip is used for excitation instead of a multichip, which can greatly reduce the cost of the devices.

Single-Component White Emitting Silicate Glass Triply Activated by Ce3+/Tb3+/Mn2+ for Organic-Resin-Free White LEDs

Thermal management is still a great challenge for high-power phosphor-converted white-light-emitting diodes (pc-WLEDs) intended for future general lighting. Luminescent glass based WLEDs (LG-WLEDs) are strongly expected to be an interesting and excellent alternative approach to traditional pc-WLEDs fabricated by combining InGaN based LED chips, with phosphor and organic resin. In the past years, many efforts have been made to develop luminescent glasses for LG-WLEDs. However, some of these glasses are poor in mechanical and chemical stability, some cannot be excited effectively owing to weak f-f absorption, and others are not very suitable for UV-LED chips ascribed to their maximum excitation wavelengths in deep UV. [1]In this paper, a series of single-component white emitting silicate SiO2–Li2O–SrO–Al2O3–K2O–P2O5: Ce3+, Tb3+, Mn2+(SLSAKP: Ce3+, Tb3+, Mn2+) glasses that simultaneously play key roles as a luminescent convertor and an encapsulating material for WLEDs were prepared via the conventional melt-quenching method. The as-synthesized SLSAKP: 0.3%Ce3+, 2.0%Tb3+, 2.0%Mn2+ glass shows good thermal stability, inconspicuous chromaticity shift, better high-temperature resistance, and higher thermal conductivity. These are rare but desirable characteristics that are not present in the phosphors used as luminescent convertor and the epoxy resin used as the encapsulating material in pc-WLEDs. Luminescent glass (LG-) WLEDs based on SLSAKP: 0.3%Ce3+, 2.0%Tb3+, 2.0%Mn2+glass and UV-COB was successfully fabricated. These results indicate that SLSAKP: Ce3+, Tb3+, Mn2+ glass may serve as a potential bifunctional white-light-emitting materialfor LG-WLEDs pumped by UV-LED chips, especially high-power UV-COB. Fig. 1. Photographic images of the mirror-polished (left) and rough-polished (right) SLSAKP: Ce3+, Tb3+, Mn2+glasses: (a) under white-emitting fluorescent lamp; (b) under 365 nm UV lamp. (c) The conceptual and actual fabrication process

ChemInform Abstract: Preparation of Sn/Mn Zirconium Phosphate as Rare Earth Free Possible White Emitting Phosphor.

AbstractSn0.5‐xMnxZr2(PO4)3 (0 ≤ x ≤ 0.5) are prepared by calcination of stoichiometric amounts of SnO, MnO, ZrO(NO3)2, and (NH4)H2PO4 in air or N2 or a 5%H2/N2 mixture (1200 °C, 3 h).

Development of Phosphors for White Emitting Near UV LEDs

not Available.

单一基质白色荧光粉Ca9Al(PO4)7∶Ce3+,Dy3+的制备与发光性能

单一基质白色荧光粉Ca₉Al(PO₄)₇∶Ce³⁺,Dy³⁺的制备与发光性能

Efficient Fluorescent Deep-Blue and Hybrid White Emitting Devices Based on Carbazole/Benzimidazole Compound

We report the synthesis, photophysics, and electrochemical characterization of carbazole/benzimidazole-based compound (Cz-2pbb) and efficient fluorescent deep-blue light emitting devices based on Cz-2pbb with the peak external quantum efficiency of 4.1% and Commission Internationale d’Énclairage coordinates of (0.16, 0.05). Efficient deep-blue emission as well as high triplet state energy of Cz-2pbb enables fabrication of hybrid white organic light emitting diodes with a single emissive layer. Hybrid white emitting devices based on Cz-2pbb show the peak external quantum efficiency exceeding 10% and power efficiency of 14.8 lm/W at a luminance of 500 cd/m2.

White Emitting ZnS Nanocrystals: Synthesis and Spectrum Characterization

Spherical organic-bonded ZnS nanocrystals with 4.0±0.2 nm in diameter are synthesized by a liquid-solid-solution method. The photoluminescence spectrum of sample ([S2−]/[Zn2+] = 1.0) shows a strong white emission with a peak at 490 nm and ∼ 170 nm full widths at half maximum. By Gauss fitting, the white emission is attributed to the overlap of a blue emission and a green-yellow emission, originating from electronic transitions from internal S2− vacancies level to valence band and to the internal Zn2+ vacancy level, respectively. After sealingZnS nanocrystals onto InGaN chips, the device shows CIE coordinates of (0.29,0.30), which indicates their potential applications for white light emitting diodes.

Ultraviolet Pumped Tricolor Phosphor Blend White Emitting LEDs

Near-UV and violet emitting AlGaInN single quantum well LED structures were grown by MOCVD on sapphire substrates. On-wafer tests before processing gave an output power at 40 mA between 1.4 mW at 380 nm and 6.7 mW at 420 nm. LED chips with wavelengths between 380 and 404 nm were selected for manufacturing radial UV LEDs and white emitting LEDs. The UV to white converters were prepared from broad band red, green and blue emitting powder phosphors with individual luminescence peaks near 610, 550 and 460 nm, respectively. White luminescence conversion (LUCO) LEDs with a warm hue and color temperatures in the range 4000-4300 K are demonstrated.

Ultraviolet Pumped Tricolor Phosphor Blend White Emitting LEDs

Near-UV and violet emitting AlGaInN single quantum well LED structures were grown by MOCVD on sapphire substrates. On-wafer tests before processing gave an output power at 40 mA between 1.4 mW at 380 nm and 6.7 mW at 420 nm. LED chips with wavelengths between 380 and 404 nm were selected for manufacturing radial UV LEDs and white emitting LEDs. The UV to white converters were prepared from broad band red, green and blue emitting powder phosphors with individual luminescence peaks near 610, 550 and 460 nm, respectively. White luminescence conversion (LUCO) LEDs with a warm hue and color temperatures in the range 4000-4300 K are demonstrated.

A White Emitting Organic Diode with a Doped Blocking Layer

A novel white emitting organic diode has been simply realized by inserting a doped hole-blocking layer between the hole transporting layer (HTL) and the electron transporting layer (ETL). The structure of this device is ITO/CuPc/NPB/blocking layer:rubrene/Alq/MgAg. Copper phthalocyanine(CuPc) was used as a buffer layer, N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB) as the HTL, and trimer of N-arylbenzimidazoles (TPBi) as the blocking layers, in which rubrene is doped. Tris(8-quinolinolato)aluminum complex(Alq) as ETL. Indium tin oxide and MgAg were the anode and cathode, respectively. The emission spectrum of this device covers a wide range of visible region and can be sensitively adjusted by the concentration of rubrene. The white emission with the CIE (Commission International de l'Eclairage) color coordinates x = 0.31, y = 0.32, a maximum luminance of 8635 cd/m2, and the luminous efficiency 1.39 lm/W at the luminance of 100 cd/m2 were obtained in the device with 1.5% rubrene concentration in TPBi.