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1.
We demonstrated a novel wide color-range tunable, highly efficient and low efficiency roll-off fluorescent organic light-emitting diode (OLED) using two undoped ultrathin emitters having complementary colors and an interlayer between them. The OLED can be tuned to emit sky blue (0.22, 0.30), cold white (0.29, 0.33), warm white (0.43, 0.42) and yellow (0.40, 0.45) according to the Commission Internationale de L’Eclairage (CIE) 1931 (x, y) chromaticity diagram. The device fabrication was simplified by eliminating doping process in the emission layers. The influence of interlayer thickness on luminous efficiency, efficiency roll-off and color tuning mechanism is thoroughly studied. The recombination zone is greatly broadened in the optimized device, which contributes to stable energy transfer to both emitters and suppressed concentration quenching. With a threshold voltage of 2.82 V, the color tunable organic light emitting diode (CT-OLED) shows a maximum luminance of 39,810 cd/m2, a peak external quantum efficiency (EQE) 6% and the efficiency roll-off as low as 11.1% at the luminance from 500 cd/m2 to 5000 cd/m2. This structure of CT-OLED has great advantages of easy fabrication and low reagent consumption. The fabricated CT-OLEDs are tunable from cold white (0.30, 0.36) to warm white (0.43, 0.42) with correlated color temperature (CCT) 6932 K and 3072 K, respectively, demonstrating that our proposed approach helps to meet the need for lighting with various CCTs. 相似文献
2.
《Ceramics International》2022,48(1):684-693
A series of optical thermometers based on Eu3+/Tb3+ doped Y3Ga5O12 with self-excited GaO6 group phosphors were designed through controllable energy transfer and local crystal field perturbation simulated using the density-functional theory approach and related structures. Color-tunable properties of the phosphors could be achieved through controllable energy transfer. In addition, the thermometers exhibited superb temperature sensitive properties. Over the entire temperature range (298.15–598.15 K), maximum values of the absolute sensitivity and relative sensitivity are 0.028 K?1 and 7.03 %K?1, respectively. Meanwhile, the thermometer has outstanding resolution (ΔT = 0.0043 K) and repeatability (98.37%). 相似文献
3.
《Ceramics International》2023,49(10):15320-15332
A variety of Bi3+ and/or Eu3+ doped KBaYSi2O7 phosphors with deep blue, cyan, orange-red, and white light multicolor emissions have been fabricated by a Pechini sol-gel (PSG) method. The KBaYSi2O7:Bi3+ phosphors exhibit an intense cyan emission or a unique narrow deep blue emission when excited by different wavelengths, which may bridge the cyan gap or act as a promising deep blue phosphor for white light-emitting diodes (WLEDs). The tunable multicolor emissions can be achieved by changing the Bi3+ doping concentrations. The Bi3+/Eu3+ co-doped KBaYSi2O7 phosphors display intrinsic emissions of Bi3+ and Eu3+ and an energy transfer process between Bi3+ and Eu3+ can be detected. The luminescence colors of KBaYSi2O7:Bi3+,Eu3+ regularly shift from blue, through cold and warm white, finally toward orange-red by adjusting the relative doping concentrations of Bi3+ and Eu3+. The single-phase white light-emitting material can be generated in both cold and warm white regions by simply varying the Eu3+ doping concentrations. Furthermore, three kinds of WLEDs devices are fabricated by KBaYSi2O7:Bi3+ or KBaYSi2O7:Bi3+,Eu3+ phosphors, which can exhibit dazzling white light emissions with eminent CIE coordinates, correlated color temperature, and color rendering index. The result offers direct evidence that the as-synthesized phosphors may be potentially applied in WLEDs and solid-state lighting. 相似文献
4.
《中国稀土学报(英文版)》2020,38(2):130-138
Investigation on the bright and stable upconversion(UC) phosphors with multicolor emissions is fundamental and significant for the frontier applications of display and tempe rature probe.He re,dive rse emitting colors with blue,cyan and yellowish green,which are caused by the energy transfer and crossrelaxation processes,are obtained by altering Er~(3+),Tm~(3+)and Yb~(3+) concentrations in Er~(3+)singly,Er~(3+)-Tm~(3+)-Yb~(3+)co-and tri-doped double perovskite La_2 ZnTiO_6(LZT) phosphors synthesized by a simple solid-state reaction.In addition,excellent infrared emission at 801 nm located at "first biological windo w" is collected in Tm~(3+)-Yb~(3+)co-doped phosphors.Meanwhile,the temperature sensing properties based on the thermally coupled levels(~2 H_(11/2)/~4S_(3/2)) of Er~(3+) ions were analyzed from 298 to 573 K of LZT:0.15 Er~(3+)/0.10 Yb~(3+)phosphor,demonstrating that the maximal sensitivity value is about56×10-4 K~(1-) at 448 K.All these results imply that this kind of UC material has potential applications in display,bioimaging and optical device. 相似文献
5.
Shao-An YanYee-Shin Chang Weng-Sing Hwang Yen-Hwei ChangMasahiro Yoshimura Chii-Shyang Hwang 《Journal of Alloys and Compounds》2011,509(19):5777-5782
Color-tunable phosphors BaLa2−xEuxWO7 were synthesized via a solid-state reaction. The absorption, excitation, emission and decay curves were obtained to study the luminescence properties. The experimental results indicate that BaLa2−xEuxWO7 phosphors have two regions in the excitation spectra: one is assigned to the charge-transfer state (CTS) band at about 338 nm, and the other is assigned to the intra-4f transitions at 360-600 nm. The emission spectra of BaLa2−xEuxWO7 phosphors excited at 395 nm exhibit a series of sharp peaks, which are attributed to the 5D0 → 7FJ (J = 0, 1, 2, 3, 4) transitions. Luminescence from higher excited states, such as 5D1, 5D2, and 5D3, were also observed at low Eu3+ concentration. The optimal emission intensity of 5D0 → 7F2 red emission is at x = 0.4 (BaLa1.6Eu0.4WO7). The chromaticity coordinates of BaLa2−xEuxWO7 phosphors vary with Eu3+ content from white, orange-red, to red, making it a candidate for a white-light-emitting phosphor in UV-LEDs. 相似文献
6.
Study on the color tunability and energy transfer mechanism in Tm3+/Dy3+ co-doped LiLaSiO4 phosphors
《Ceramics International》2021,47(20):28384-28399
Many color-tunable LiLaSiO4: αTm3+, βDy3+ phosphors were prepared using the traditional high-temperature solid-phase method. The phase composition, surface morphology, fluorescence spectrum, fluorescence lifetime, energy transfer mechanism, and color coordinates of the samples were analyzed using XRD, SEM, TEM and fluorescence spectrometer. The results show that LiLaSiO4: αTm3+ phosphor emits high intensity blue light at 460 nm and the concentration quenching point of Tm3+, α = 0.015 mol. In LiLaSiO4: αTm3+, βDy3+ phosphors, as the doped Dy3+ doping increases, the luminescence intensity of Tm3+ gradually decreases, the luminescence intensity of Dy3+ first increases and then decreases. The concentration quenching point of Dy3+, β = 0.015 mol. Adjustable light-emitting color can be obtained by changing the doping molar mass of Dy3+ or the wavelength of the excitation light. There is an effective energy transfer between Tm3+→Dy3+. The energy transfer mechanism is the electric dipole-electric dipole interaction, and the energy transfer efficiency reaches 90.11% when β = 0.06 mol. The quantum yield of LiLaSiO4:0.015 Tm3+,0.015Dy3+ was 39.0%. The single-matrix white light LiLaSiO4: αTm3+, βDy3+ phosphors with excellent performance is a prospective material for of white LEDs. 相似文献
7.
Fengping Ruan Degang Deng Hua Yu Ming Wu Bowen Chen Shiqing Xu Ruoshan Lei 《Ceramics International》2018,44(13):15432-15439
We synthesized and investigated the effect of Eu2+ ions doping in a novel phosphor-silicate Ca8Sc2(PO4)6(SiO4) phosphor. The structure and photoluminescence properties were determined by X-ray powder diffraction Rietveld refinement, diffuse reflection spectra, emission-excitation spectra, decay curves and temperature dependence spectra. The phosphors showed an asymmetric broad-band blue emission (Eu2+) with peak at 470?nm. Furthermore, we presented the Ca7.96Sc2(PO4)6-y(SiO4)1+y:0.04Eu2+ phosphors by co-substituting [Eu2+-Si4+] for [Ca2+-P5+], and different behaviors of luminescence evolution in response to structural variation were verified among the series of phosphors. The results were attributed to the presence of multi Ca2+ sites, resulting in the mixing of blue and green emissions for Eu2+ ions. The complex anion substitution of [PO4]3- by [SiO4]4- induced an increased crystal field splitting of the Eu2+ ions, which caused a decrease in emission energy from the 5d excited state to the 4f ground state and a resultant red-shift from 470?nm to 520?nm. All the properties indicated that the Ca8Sc2(PO4)6(SiO4):Eu2+ phosphors have potential application for color-tunable WLEDs. 相似文献
8.
Xinguo Zhang Zhenpeng Zhu Ziying Guo Zishan Sun Liya Zhou Zhan-chao Wu 《Ceramics International》2018,44(14):16514-16521
A new vanadate Ca3LiMgV3O12 and its Eu3+-doped counterparts were synthesized. Rietveld confinement result of Ca3LiMgV3O12 host indicates that it belongs to cubic space group Ia-3d with parameters of a =?12.4300?Å, V =?1920.49?Å3, Z?=?8. Under UV excitation, pure Ca3LiMgV3O12 exhibits a bluish-green broadband emission at 490?nm, while Eu3+ doped Ca3LiMgV3O12 shows one bluish-green broad band with a series of red sharp peaks, which originate from the V5+-O2- charge transfer and the Eu3+ intra-4f transitions, respectively. The occurrence of VO4→Eu3+ energy transfer is confirmed by decay lifetime analysis and time-resolved emission spectra. It is found that emitting color varies from bluish-green to orange-red with increasing Eu3+ concentration. VO4 bluish-green and Eu3+ red emission shows different thermal quenching response with increasing temperature, due to their different activation energy. 相似文献
9.
We demonstrated an efficient color-tunable electrophosphorescent device fabricated by a photo-bleaching method. Electroluminescence studies indicate that excellent device performance can be achieved through efficient Förster energy transfer from the conjugated polymer to the iridium complexes by improving their miscibility. The use of a very low concentration of red phosphorescent dye and the easy degradation characteristics of conjugated structure of the red dopant enable color-tuning from red to green emission by a simple UV-irradiation process without a sacrifice of luminescent properties.tp 相似文献
10.
Color-tunable up-conversion powder phosphors Zn(AlxGa1-x)2O4: Yb3+,Tm3+,Er3+ were synthesized via high temperature solid-state reaction. Also, the morphological and structural characterization, up-conversion luminescent properties were all investigated in this paper. In brief, under the excitation of a 980?nm laser, all powders have same emission peaks containing blue emission at 477?nm (attributed to 1G4→3H6 transition of Tm3+ ions), green emission at 526?nm and 549?nm (attributed to 2H11/2→ 4I15/2 and 4S3/2→4I15/2 transition of Er3+ ions respectively), red emission at about 659?nm and 694?nm (attributed to 4F9/2→4I15/2 transition of Er3+ ions and 3F3→3H6 transition of Tm3+ ions, respectively), which are not changed after the doping of Al3+ ions. However, the doping of Al3+ ions can enhance the up-conversion luminescent intensity and efficiency, while the emission color of as-prepared powder phosphors can be tunable by controlling the doping amount of Al3+ ions. Taking Zn(Al0.5Ga0.5)2O4:Yb,Tm,Er as the cut-off value, the emissions have clear blue-shift firstly and then show obvious red-shift with the increasing doping of Al3+ ions. Stated thus, pink emission in ZnAl2O4:Yb,Tm,Er, purplish pink emission in ZnGa2O4:Yb,Tm,Er and Zn(Al0.9Ga0.1)2O4:Yb,Tm,Er, purple emission in Zn(Al0.1Ga0.9)2O4:Yb,Tm,Er and Zn(Al0.3Ga0.7)2O4:Yb,Tm,Er, purplish blue emission in Zn(Al0.7Ga0.3)2O4:Yb,Tm,Er, blue emission in Zn(Al0.5Ga0.5)2O4:Yb,Tm,Er can be observed, which confirm the potential applications of as-prepared Zn(AlxGa1-x)2O4:Yb3+,Tm3+,Er3+ powder phosphors in luminous paint, infrared detection and so on. 相似文献