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White light emitting thermally stable bismuth phosphate phosphor Ca <sub/>3</sub> Bi( <scp>PO</scp><sub/>4</sub> ) <sub/>3</sub> :Dy <sup>3+</sup> for solid state lighting applications
摘要： White light emitting dysprosium doped Ca3Bi(PO4)3 phosphor was successfully synthesized via co-precipitation method for the first time and the structural, vibrational, morphological and luminescent properties have been investigated for solid state lighting applications. The X-ray diffraction (XRD) and structural refinement studies reveal that the synthesized phosphors consist of single phase with cubic structure. The field emission scanning electron microscopy (FE-SEM) images reveal that the as-synthesized phosphor has micron size with an irregular shape. Under near ultraviolet (n-UV) and blue excitation, the phosphor exhibits white light emission via a combination of blue (~451 nm) and yellow (~575 nm) emission bands. The optimized concentration of Dy3+ ions is 6.0 mol % after which the concertation quenching takes place. The process of energy transfer between Dy3+ ions is due to dipole-dipole interaction, which was confirmed by applying Dexter and Reisfeld’s Energy Transfer (ET) formula. The CIE chromaticity coordinates for the optimized phosphor were (0.329, 0.377), which lie in the white light region. The emission intensity remains to 83.41% at 373 K to that of at room temperature, which indicates good thermal stability. The above mentioned results demonstrate that Ca3Bi(PO4)3 is a potential phosphor for solid state lighting applications.
关键词： White LEDs,Structural and luminescent properties,White light emission,Phosphor,Thermally stable
更新于2025-11-21 11:18:25
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Photoluminescence Characteristics of Sm3+-doped LnBWO6 (Ln=La, Gd and Y) as New Orange-red Phosphors
摘要： A series of Sm3+-doped LnBWO6 (Ln=La, Gd and Y) phosphors with orange-red light emitting in pure phase were prepared by high temperature solid-state process. The crystal structure, photoluminescence properties, decay lifetimes and thermal stability properties of those as-prepared samples were investigated. Those phosphors can be efficiently excited by near-UV and blue light and emitted orange-red luminescence with color coordinates (0.622, 0.377). Among those LnBWO6 (Ln=La, Gd and Y) hosts, the emission intensities of Sm3+-doped LaBWO6 are the strongest ones. The optimum doping concentration and critical energy transfer distance of Sm3+ ions in LaBWO6 were determined. The fluorescence concentration quenching mechanism was attributed to the dipole-dipole interaction between the Sm3+ ions. The fluorescent thermal quenching studies showed Sm3+ doped LaBWO6 had high thermal-stable properties. The present work suggested that Sm3+-doped LnBWO6 (Ln=La, Gd and Y) as orange-red phosphors exhibited potential application in white LED.
关键词： red phosphors,concentration quenching,energy transfer,white LEDs,luminescent properties
更新于2025-09-23 15:22:29
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Achieving Near-Unity Photoluminescence Efficiency for Blue-violet Emitting Perovskite Nanocrystals
摘要： While the perovskite nanocrystals (NCs) have shown great promise as materials for efficient light emitting diodes (LEDs), low photoluminescence quantum yield (PLQY) of the blue-emitting perovskites is an impediment to the development of white LEDs of which blue is an essential component. Herein, we report that room temperature post-synthetic treatment of weakly blue-violet emitting (PLQY 3%) CsPbCl3 NCs with CdCl2 results in an instantaneous enhancement of the PLQY to near-unity without affecting the PL peak position (406 nm) and spectral width. The time-resolved PL and ultrafast transient absorption measurements confirm the removal of nonradiative defect states of the CsPbCl3 NCs in treated sample. The elemental composition and structural data of the treated sample reveal facile doping of Cd2+ into the crystal lattice without affecting the size and shape of the NCs. Extraordinary PLQY, high air- and photo-stability and ease of preparation of this Cd-doped CsPbCl3 make it by far the most attractive blue-emitting perovskite for development of efficient blue and white LEDs.
关键词： photoluminescence quantum yield,blue-emitting perovskites,perovskite nanocrystals,CdCl2 treatment,white LEDs
更新于2025-09-23 15:21:21
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Full-visible-spectrum lighting enabled by an excellent cyan-emitting garnet phosphor
摘要： The development of phosphor materials with outstanding photoluminescence properties is critical for next-generation high-quality solid-state white lighting. As there is a blue-green cavity existed in the emission spectra of the traditional phosphor-converted white-light-emitting diodes (w-LEDs), cyan-emitting phosphor serves an important function in compensating the spectral gap to realize the “full-visible-spectrum lighting”. Herein, we reported the discovery of an efficient cyan-emitting Ce3+-doped Ca2YHf2Al3O12 (CYHAO) garnet phosphor with good thermal stability. The as-prepared CYHAO:Ce3+ phosphor exhibited a broad excitation band in the range of 360 to 460 nm with a maximum at 408 nm, making this phosphor compatible with an efficient 400 nm NUV-emitting LED chip. Under the 408 nm excitation, the optimal sample of CYHAO:0.03Ce3+ exhibited bright broadband cyan emission (λem = 493 nm; bandwidth = 100 nm) together with extra-high internal quantum efficiency (IQE) of 89.5% and external quantum efficiency (EQE) of 69.1%. Notably, the as-prepared CYHAO:0.03Ce3+ phosphor showed good thermal stability (64.2% of emission intensity retained at 423K) and excellent color stability when working in the temperature range of 303-463 K. Importantly, the constructed w-LED device exhibited bright well-distributed warm white light with high color rendering index (CRI; Ra = 93.5 and R12 = 90.4) and low correlated color temperature (3700 K) under 60 mA driven current, indicating that the title cyan phosphor can be utilized as the compensation of the blue-green cavity to apply in full-visible-spectrum lighting. Furthermore, these findings provide new insights into exploring high-performance cyan phosphors for NUV-pumped high-CRI warm w-LEDs.
关键词： White LEDs,Color rendering index,Cyan emissions,Phosphors,Full-visible-spectrum lighting
更新于2025-09-23 15:21:01
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Tunable photoluminescence and energy transfer of novel phosphor Sr9La2W4O24:Sm3+, Eu3+ for near-UV white LEDs
摘要： Novel Sr9La2W4O24:xSm3+ and Sr9La2W4O24:0.15Sm3+, yEu3+ orange-red phosphors with double perovskite tungsten structure are synthesized by high-temperature solid-phase reaction method. X-ray diffraction patterns indicate the prepared phosphors are pure phase with a tetragonal structure and the SEM image displays the long string structure with a diameter of one micron. Under the excitation of near-UV light, the Sm3+ and Eu3+ ions activated Sr9La2W4O24 phosphors exhibit their characteristic emissions in the orange-red region, and the emitting light color of the Sr9La2W4O24:0.15Sm3+, yEu3+ phosphors can be adjusted from orange to red by increasing the concentration of Eu3+ ions implying their potential applications as orange-red emitting phosphor for LED in solid-state lighting. The optimal doping concentration of Sm3+ ions in Sr9La2W4O24:xSm3+ phosphors is around 15?mol%. The energy transfer from Sm3+ to Eu3+ is discussed and the major mechanism for concentration quenching is the dipole–dipole (d–d) interaction.
关键词： Sm3+,phosphors,energy transfer,double perovskite,Eu3+,white LEDs
更新于2025-09-23 15:21:01
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Synthesis and photoluminescence properties of Ln3+ (Ln3+= Sm3+/Eu3+) doped Na2NbAlO5 phosphors
摘要： A series of Ln3+ (Ln3+=Sm3+/Eu3+) ions doped Na2NbAlO5 phosphors have been synthesized by solid-state method. Sm3+ and Eu3+ ion doped phosphors are characterized by SEM, XRD, EDX, photoluminescence, decay and thermal stability profiles. The Ln3+-doped samples are consistent with the pure Na2NbAlO5 phase which were analyzed by the X-ray diffraction result. SEM results showed the homogeneous aggregates and particles size of Sm3+ (0.6-0.9μm) and Eu3+ (0.2-0.3μm) doped Na2NbAlO5. From EDX diagram, the samples are consisted of Na, Nb, Al, O and Sm ,or Eu elements.With the introduction of Eu3+ ions, the decay curves of Sm3+ decreases monotonically, which supports the occurrence of the energy transfer from Sm3+ to Eu3+ in Na2NbAlO5 host. The fluorescence lifetime decreases with increasing temperature . The energy transfer mechanisms of Sm3+ and Eu3+ doped Na2NbAlO5 have been investigated and can be derived to be electric dipole-dipole and diopole-quadrupole interactions, respectively. In addition, the temperature-dependent emission spectra of Sm3+/Eu3+ doped Na2NbAlO5 phosphors possess superior thermal stability. Under the ultraviolet light, the prepared Na2-xNbAlO5: xLn3+ (Ln3+= Sm3+/Eu3+) phosphors show the characteristic orange (Sm3+), red (Eu3+) emissions respectively. The obtained results suggest that the new Na2NbAlO5:xLn3+ (Ln3+= Sm3+/Eu3+) phosphors are promising candidates for white light-emitting diodes.
关键词： Photoluminescence,White LEDs,Energy transfer,Na2NbAlO5
更新于2025-09-23 15:21:01
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Highly solid-luminescent graphitic C <sub/>3</sub> N <sub/>4</sub> nanotubes for white light-emitting diodes
摘要： Graphitic C3N4 (g-C3N4) has seldom been used for white light-emitting diode (LED) phosphors due to its low solid-state fluorescence quantum yield. Here, we report a facile thermal condensation path for the synthesis of g-C3N4 nanotubes stuffed with quantum dots. The g-C3N4 nanotubes have a high fluorescence quantum yield of 30.92% in the solid state. Nitrogen-rich and graphitic carbon-free features are responsible for the enhanced quantum efficiency. The photoluminescence quantum yield can be controlled and improved by the reaction temperature. We finally demonstrate white light emission by coating the highly solid-luminescent g-C3N4 nanotubes as phosphors onto a 370 nm ultraviolet LED.
关键词： graphitic carbon nitride,nanotubes,fluorescence,phosphors,white LEDs
更新于2025-09-23 15:19:57
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Novel highly luminescent double-perovskite Ca2GdSbO6:Eu3+ red phosphors with high color purity for white LEDs: Synthesis, crystal structure, and photoluminescence properties
摘要： High-efficiency red-emitting phosphors are required to fabricate high-performance white light-emitting diodes (LEDs). Herein, the novel highly efficient Eu3+-activated Ca2GdSbO6 double-perovskite red phosphors with good thermal stability toward warm-white LEDs were reported. A series of Ca2Gd(1-x)EuxSbO6 red phosphors with different Eu3+ doping concentrations (x = 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8) were synthesized by using high-temperature solid-state reaction method. Under the excitation of 396 nm near-ultraviolet light, these Ca2Gd(1-x)EuxSbO6 phosphors showed intense red emissions peaking at 612 nm due to the 5D0→7F2 transition of Eu3+ ions. The strongest luminescence intensity reached when Eu3+ doping concentration was x = 0.5, and the critical distance between Eu3+ activators was calculated to be 7.97 ?. The concentration quenching mechanism was due to the dipole-dipole interaction of Eu3+ ions. The CIE color coordinates of the optimal Ca2Gd0.5Eu0.5SbO6 phosphors were determined to be (0.6629, 0.3367), and the corresponding color purity reached about 94.9%. Importantly, the Ca2Gd0.5Eu0.5SbO6 phosphors revealed outstanding internal quantum efficiency of 73% and good thermal stability. The emission intensity of Ca2Gd0.5Eu0.5SbO6 phosphors at 423 K still remained about 73% of its initial value at 303 K. Finally, a prototype white LED device was fabricated by coating the phosphor blend of commercial blue-emitting BaMgAl10O17:Eu2+ and our as-prepared red-emitting Ca2Gd0.5Eu0.5SbO6 on a 395 nm LED chip. Under 20 mA driven current, the device showed bright warm-white light with CIE color coordinates of (0.3888, 0.3943), correlated color temperature of 3911 K, and color rendering index of 88.4. The results demonstrated that the developed novel red-emitting Ca2Gd0.5Eu0.5SbO6 phosphors could be used as potential color converters in white LEDs.
关键词： White LEDs,Photoluminescence,Ca2GdSbO6,Double-perovskite,Eu3+ ions,Red-emitting phosphors
更新于2025-09-23 15:19:57
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Synthesis and photoluminescence properties of a new blue-light-excitable red phosphor Ca2LaTaO6:Eu3+ for white LEDs
摘要： In this paper, a series of Eu3+-activated double-perovskite Ca2LaTaO6 (abbreviated as CLT:xEu3+; x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8) red-emitting phosphors have been successfully synthesized via the conventional high-temperature solid-state reaction method. These samples were characterized by X-ray diffraction, Rietveld refinement, field-emission scanning electron microscope, elemental mapping, energy-dispersive spectrum, room-temperature photoluminescence, decay lifetimes, quantum efficiency, CIE color coordinates, and temperature-dependent emission spectra. Interestingly, under blue excitation into the 7F0→5D2 transition of Eu3+ at 466 nm, the CLT:xEu3+ phosphors could emit bright red light corresponding to the 5D0→7FJ (J = 1, 2, 3, 4) transitions. Their luminescence properties have been investigated as a function of the Eu3+ ions concentration. It was found that the CLT:0.4Eu3+ sample exhibited the strongest emission intensity, and the concentration quenching effect was caused by the dipole-dipole interaction among Eu3+ activators. Impressively, the emission intensity of the as-prepared CLT:0.4Eu3+ phosphors was about 4.3 times higher than the commercial Y2O3:Eu3+ red phosphors. Moreover, the CLT:0.4Eu3+ sample had excellent CIE color coordinates of (0.665, 0.334) and supereminent color purity of 95.3%. Notably, the study on temperature-dependent emission spectra of the CLT:0.4Eu3+ sample revealed its good thermal stability and color stability at high temperatures. These excellent photoluminescence properties of CLT:0.4Eu3+ phosphors indicated their promising application potential in white light-emitting diodes as blue-light-excitable red phosphors.
关键词： Ca2LaTaO6,White LEDs,Red-emitting phosphors,Eu3+ ions,Double-perovskite,Photoluminescence
更新于2025-09-23 15:19:57
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Green and Orange Emissive Carbon Dots with High Quantum Yields Dispersed in Matrices for Phosphor-Based White LEDs
摘要： Carbon dots (CDs) have aroused more interest in the LED phosphor. High quantum yields and suppressing solid-state luminescence quenching are the key factors for CDs to prepare high-quality phosphors. In this work, orange and green emissive CDs (O-CDs and G-CDs) with very high absolute quantum yields (abs. QYs: 85.19% at natural pH and 96.12% at pH 9.0 for G-CDs; 34.89% in aqueous solution and 77.54% in ethanol for O-CDs) were achieved. Then, sodium silicate and PVA were selected as matrices to suppress their aggregation-induced quenching effect. Phosphor powder was prepared by microwave-assisted pyrolysis of sodium silicate and films by self-assembling of PVA in the presence of the CDs. The phosphor powder simultaneously containing G-CDs and O-CDs (G-O-CDs-phosphor) presents bright yellow fluorescence but owns a relatively low abs. QY. However, O-CDs/PVA and G-CDs/PVA phosphor films possess very high abs. QYs of 51.51% and 72.81%, respectively. LEDs constructed by coating G-O-CDs-phosphor on a blue chip exhibited a cool white color and a color rendering index (CRI) of 78. Interestingly, high-quality warm white LEDs owning a superior CRI of 93 were achieved by the O-CDs/PVA and G-CDs/PVA films. By comparison, PVA is more suitable to maintain the high performance of G-CDs and O-CDs for high-quality phosphors.
关键词： White LEDs,Phosphor,Carbon dots,High quantum yield,Rhodamine B
更新于2025-09-23 15:19:57