Cyan Phosphor Research Articles

Customized Cyan Phosphors for Efficient Full-Spectrum Illumination and Fingerprint Detection.

Traditional lighting methods have environmental and efficiency drawbacks. These methods are gradually being overshadowed by light-emitting diodes (LEDs) because of their superior color rendering and energy efficiency. In this study, color-tunable NaBa2(Ba/Sr/Ca)Si2O7F:Eu2+ phosphors are successfully designed by modulating the local crystal field environment through homodominant-group cation substitution, thereby allowing for a spectral shift from blue to bright cyan. Detailed structural analysis of the samples demonstrated the synthesis of high-quality solid-solution materials. A comprehensive examination of the phosphor crystal structure, photoluminescence properties, and fluorescence lifetime reveal that the cyan phosphor possesses a remarkable internal quantum efficiency (IQE = 93%) and low thermal quenching characteristics (I423 K/I303 K = 84%). The results illustrate the critical role of Eu2+-activated cyan phosphors in reducing the spectral gap to attain a natural white-light spectrum, which is indispensable for achieving high color fidelity. The practical application of cyan phosphors in the fabrication of high-performance white LED (WLED) (Ra = 96.8) and fingerprint detection is validated, demonstrating their extensive utility in enhancing visual accuracy and identification.

Full-Visible-Spectrum White LEDs Enabled by a Blue-Light-Excitable Cyan Phosphor.

Efficient blue-light-excitable broadband cyan-emitting phosphors may yield full-visible-spectrum white light-emitting diodes (WLEDs) with ultrahigh color rendering (Ra > 95). However, this requires closing the "cyan gap" in the 480-520 nm region of the visible spectrum, which is challenging. Herein, a well-performed cyan-emitting garnet phosphor Ca2LuAlGa2Si2O12:Ce3+ (CLAGSO:Ce3+) is reported. Under 430 nm excitation, the optimal CLAGSO:5%Ce3+ compound exhibits a broadband cyan emission (peak, 496 nm; bandwidth, 102 nm) with a high internal quantum efficiency of 85.6% and an excellent thermal resistance performance (69.1% at 423 K). Importantly, this as-prepared cyan-emitting phosphor provides sufficient cyan emission and enables filling the well-known so-called "cyan gap" between the blue LED chip and the commercial Y3Al5O12:Ce3+ (YAG:Ce3+) yellow phosphor. Impressively, a WLED device fabricated with the optimal CLAGSO:5%Ce3+ sample shows a low correlated color temperature (4053 K) and an ultrahigh color rendering index (Ra = 96.6), as well as an excellent luminous efficacy (74.09 lm W-1). These results highlight the importance of blue-excited broadband cyan-emitting phosphors in closing the cyan gap and enabling human-centric full-visible-spectrum warm WLED devices for high-quality solid-state lighting.

Designing a high-efficiency broadband cyan phosphor for low-blue full-spectrum LED lighting

Efficient cyan-emitting phosphor plays an important role in the development of solid-state lighting, which is indispensable to filling the cyan gap for full-spectrum warm-white light-emitting diodes (WLEDs) with high color rendering index (CRI). Herein, a novel highly efficient broadband cyan phosphor Ce3+-doped Ca3HfAl2Si2O12 (CHASO: Ce3+) garnet compound was developed by the substitution of Lu3+-Al3+ with Ca2+-Hf4+/Si4+ in Lu3Al5O12. The crystal structure and photoluminescence (PL) properties of CHASO: Ce3+ were investigated in detail. Notably, CHASO: Ce3+ phosphor can be effectively excited by violet light (390 – 430 nm) and exhibited bright cyan emissions around 490 nm with high PL internal quantum yields of 89.2 %. Moreover, the integrated PL intensity of the phosphor at 423 K was 66.3 % of that at room temperature. Finally, by incorporating CHASO: 11 %Ce3+ with commercial blue/yellow/red phosphor onto a violet LED chip (400 nm), the prototype full-spectrum WLEDs device exhibits warm white light with high color rendering index (CRI, Ra and R9 > 90) and low correlated color temperature 3301 K. These results suggest the highly efficient phosphor CHASO: Ce3+ is promising for low-blue full-spectrum healthy lighting.

A phosphor-in-glass film prepared with a novel orange Lu2GdMg2AlSi2O12:Ce3+ phosphor and a cyan BaSi2O2N2:Eu2+ phosphor

The preparation of phosphor-in-glass (PiG) films containing orange and cyan phosphors is one of the possible ways to improve the color rendering index (CRI) and correlated color temperature (CCT) of white LEDs packaged with PiG films. Recently, by matrix ion substitution, we have synthesized a novel orange Lu2GdMg2AlSi2O12:Ce3+ phosphor. Then, we used a “coating and low-temperature sintering” method to prepare PiG films containing this novel orange phosphor and the commercial cyan BaSi2O2N2:Eu2+ phosphor on sapphire substrates. Combining these PiG films with blue LED chips, warm white LEDs with CRI above 90 and CCT below 4000 K can be obtained. This suggests that the PiG films containing cyan and orange phosphors are promising to improve the CCT and CRI of white LEDs packaged with PiG films.

Zero-dimensional hybrid Cu(I) halide with cyan light emission for use in white light emitting diode

Traditional white light-emitting diode (WLED) is mainly depending on coating broadband yellow phosphors (520–700 nm) on blue emitting LED chip (440–460). However, too strong blue light and absence of cyan light results in incongruous emission strength and low color rendering index (CRI), which cause serious damage to retina of eye. To overcome these shortcomings, cyan light emitting phosphor is highly desirable for the full-visible-spectrum LED with high CRI, but bright cyan phosphor remains rare. Herein, a new 0D hybrid copper(I) halide of [TMPDA]Cu2I6 (TMPDA = N,N,2,2-tetramethyl-1,3-propylenediamine) single crystal is reported as a cyan light emitter with mominant emission wavelength at 489 nm, photoluminescence quantum yield of 26.66 % and large Stokes shift of 198 nm exceeding most of organic-inorganic metal halides. Remarkably, the single crystals display stable emission in various polar organic solvents and high temperature with sufficient emitting stability. More significantly, this 0D cuprous halide act as down-conversion cyan phosphor to fabricate WLED with a high CRI of 95 by reducing the cyan gap. In this study, we demonstrate an optical engineering strategy to prepare efficient cyan light emitting 0D cuprous halide and assembly high-performance WLED.

Enhancing the cyan light emission of Ba9Lu2Si6O24:Ce phosphors by crystal-site engineering for full spectrum lighting

Filling the cyan gap is the key element in achieving full-spectrum illumination using violet chip to excite red, green and blue phosphors. However, designing cyan phosphors suitable for violet light excitation with excellent performance remains challenging. Herein, a novel cyan phosphor Ba9Lu2-x-nSi6O24:xCe (n-BLS:Ce) with multiple crystal sites of Ba2+ and Lu3+ for Ce3+ ions was designed and prepared via crystal-site engineering. The Ce3+ ions at Ba2+ sites emit ultraviolet light at 385 nm under 325 nm ultraviolet light excitation, and the Ce3+ ions at Lu3+ sites emit cyan light at 485 nm under 395 nm violet light excitation. The favorable occupation of Ce3+ ions at Lu3+ sites could be realized by introducing Lu vacancies. Significantly, the cyan light emission intensity of Ba9Lu1.4Si6O24:0.3Ce (n0.3-BLS:Ce) with Lu vacancies is effectively improved by 47 % compared to Ba9Lu1.7Si6O24:0.3Ce (n0-BLS:Ce) without Lu vacancies. And the emission intensity at 150 °C retains 96 % of that at room temperature. The color rendering index increases from 87.9 to 94.5 after supplementing Ba9Lu2-x-nSi6O24:xCe cyan phosphor in w-LEDs devices combining commercial red, green, and blue phosphors with a violet chip, indicating its potential practical application in full-spectrum lighting. This work also provides new ideas for the design and development of new and efficient high-quality light-emitting materials.

Luminescent properties of Y2LaCaGa3ZrO12: Bi3+, Al3+ cyan phosphors for application in white light emitting diodes

High-quality white light can be obtained from a mixture of blue, green, and red phosphors excited by ultraviolet chips. However, this approach suffers from the presence of a cyan gap in the emission spectra, which hinders further improvement in the color rendering index (CRI). The obvious solution to this problem should be the development of efficient ultraviolet-excited cyan phosphors to fill this gap. Therefore, a series of Y2LaCaGa3ZrO12: xBi3+ (x = 0–0.1) cyan phosphors were synthesized via high-temperature solid-state reaction method, and their properties were systematically characterized. The Bi3+ ion in Y2LaCaGa3ZrO12 exhibits dual-mode luminescence with emission bands peaking at 356 nm and 483 nm, originating from the 3P1→1S0 transitions of Bi3+ at different sites. The ultraviolet emission is attributed to Bi3+ occupying 8 coordination sites, while the cyan emission arises from Bi3+ in 6 coordination sites. It is noteworthy that the emission intensity and thermal stability of the phosphors can be further improved by partially substituting Ga3+ with Al3+. By incorporating Y2LaCaGa3ZrO12: 0.02Bi3+ or Y2LaCaGa2.7Al0.3ZrO12: 0.02Bi3+ with commercial phosphors and depositing them onto a 365 nm ultraviolet chip, the prototype white light emitting diodes (w-LEDs) exhibits white light with high CRI of 89.6 and 90.4, respectively. These results validate the potential of Bi3+ activated Y2LaCaGa3-yAlyZrO12 (y = 0–1) cyan phosphor as a promising candidate material for application in UV-excited w-LEDs.

Manipulating cationic ordering toward highly efficient and zero-thermal-quenching cyan photoluminescence

Developing effective design principle in crystalline materials for superior optical properties remains a critical challenge. Herein, we establish the cationic ordering strategy to build rigid framework and significantly improve phosphor performance. As a proof of concept, the NaHf2-xYx(PO4)3:Eu2+ (x = 0.05–0.2) phosphor series is constructed, which possesses absolutely cationic ordered structure and the linked outstanding photoluminescent properties. Structurally, heterovalent substitution in the lattice maintains the single-site occupancy of Na+ ions in NaHf2-xYx(PO4)3:Eu2+, as confirmed by Rietveld refinements and NMR spectroscopy. This cationic arrangement keeps the cation/vacancy ordered distribution that ensures high structural rigidity, with Debye temperature, as the indicator of rigidity, extracted from low temperature heat capacities exceeding 379 K. The resultant high structural rigidity, coupled with intrinsic defects, induces zero-thermal-quenching luminescence up to 150 °C. Moreover, the substitution of Y3+ at Hf4+ site facilitates effective Eu3+ to Eu2+ reduction, making them excellent cyan emitters with quantum efficiency exceeding 90 % and intense violet absorption. This work provides an impetus for the discovery of the currently state-of-the-art cyan phosphors for practical applications and gives insight into the structural factors influencing luminescent properties.

Less is more: An oxyfluoride garnet broadband cyan-green phosphor towards highly efficient full-spectrum WLEDs

Full-spectrum lighting has become the development direction for human-centric illumination. However, the reabsorption effect caused by cyan, green and yellow multiple-phosphor packaging leads to low luminous efficiency. In this work, a broadband cyan-green phosphor is proposed to replace the cyan and yellow phosphors for highly efficient and thermally robust full-spectrum WLEDs. A new family of oxyfluoride garnet phosphors Lu2QMg2Al3O9F3: Ce3+ (Q = Ca, Sr, Ba) has been developed by incorporating F- into the classic LuAG: Ce3+ green phosphor. The excess charge was compensated by substituting trivalent Lu3+ and Al3+ with divalent alkaline earth element. The low covalency and phonon energy of fluorine-containing system endow these serial phosphors with efficient and thermally stable blue-shifted emission. The representative Lu2SrMg2Al3O9F3: Ce3+ exhibits a broadband cyan-green emission peaked at 513 nm with a 105 nm FWHM. Furthermore, outstanding quantum efficiency (88.4%) and thermal stability (94.3% @ 423 K) were achieved. This oxyfluoride phosphor was packaged with red phosphor without cyan phosphor on a blue chip. The obtained WLEDs show an excellent color rendering index (Ra = 96.8) with luminous efficiency (LE = 106 lm/W). This research might pave a promising avenue for the development of next-generation full-spectrum lighting.

Preparation of BaSi2O2N2:Eu2+ cyan phosphor with excellent luminescence properties via heterogeneous precipitation method for high-CRI white LED applications

Preparation of BaSi2O2N2:Eu2+ cyan phosphor with excellent luminescence properties via heterogeneous precipitation method for high-CRI white LED applications

Tunable emission of Ce3+ in (K, Rb)3GdSi2O7 phosphors toward broadband cyan luminescence

AbstractIn an effort to obtain a novel cyan‐emitting phosphor, the [K1‐xRbx]3GdSi2O7: yCe3+ materials (x = 0, 0.1, 0.2, 0.3, 0.4, y = 0, 0.005, 0.01, 0.02, 0.03, 0.04) are synthesized via a solid‐state reaction pathway, and their crystal structure and luminescence behaviors are studied systematically. The chemical substitution of Rb+ in the K+ sites can enlarge the K3GdSi2O7 host lattice and help to the blue‐shifting of emission band of Ce3+ ions due to the decreased crystal field splitting effect. It is also confirmed that the Ce3+ ions tend to enter [Gd1O6] and [Gd2O6] polyhedrons simultaneously. Consequently, the [K0.7Rb0.3]3GdSi2O7: Ce3+ phosphor yields a broadband cyan emission centered at 492 nm with the full width at half maximum (FWHM) of ∼115 nm upon 365 nm excitation. The optimal concentration of Ce3+ dopant is determined to be 0.01, and the concentration quenching effect can be attributed to the dipole−dipole interactions. The white light emitting diode (WLED) device fabricated by employing the discovered [K0.7Rb0.3]3GdSi2O7: 0.01Ce3+ phosphor displays a high color rendering index (Ra = 91.7) and a low correlated color temperature (CCT = 3749 K). This work may promote the development of cyan phosphors for near ultraviolet‐converted WLEDs with high performance.

Development of a novel Eu2+ activated oxonitridosilicate cyan phosphor for enhancing the color quality of a violet-chip-based white LED.

Cyan phosphors are urgently needed to fill the cyan gap and improve the spectral continuity of white light-emitting diodes (LEDs) to cater to the high demand for high-quality lighting. Here, a series of new Eu2+-activated La3Si6.5Al1.5N9.5O5.5 (LSANO) cyan phosphors were prepared, and their luminescence properties and color centers were analyzed through fluorescence spectral measurements from 7 K to 475 K. At 300 K, the photoluminescence excitation (PLE) spectrum monitored at 483 nm presents a broadband of 200-460 nm with a peak at 398 nm, matching well with commercial violet LED chips. When excited by 398 nm violet light, the photoluminescence emission (PL) spectrum of LSANO:0.01Eu2+ exhibits a cyan emission band at about 483 nm. At 7 K, the emission spectrum clearly shows an asymmetric emission band and the emission peak wavelength changes from 483 nm (300 K) to 500 nm (7 K), indicating that there are two possible color centers in the LSANO:Eu2+ phosphor. Moreover, the maximum emission value can be adjusted from 480 to 499 nm by adjusting the doping content of Eu2+. Finally, a violet-chip-based white LED with the optimized color quality of Ra = 91.4, Rf = 90.1, and Rg = 93.6 was fabricated by adding the prepared cyan phosphor, verifying the potential application of the prepared cyan phosphor LSANO:Eu2+ in high-quality white LEDs.

Overcoming the cyan gap for full‐spectrum lighting using cation‐substitution‐induced rigid Ca2YZr2Al3O12:Ce3+

AbstractMixing multicolor phosphors for simulating the full spectrum of sunlight illumination is a popular solution to obtain high‐quality white light. However, there is still a need to overcome the cyan gap in the emission spectrum. In this work, a series of garnet Ca2Y0.94–xLuxZr2–yHfyAl3O12:6%Ce3+ (abbreviated as CY0.94–xLuxZr2–yHfyA:Ce3+) cyan phosphors are designed and prepared by substituting Y3+ and Zr4+ in Ca2YZr2Al3O12:6%Ce3+ with Lu3+ and Hf4+ with smaller ionic radius and larger mass. Under 405 nm violet light excitation, the optimized Ca2Y0.88Lu0.06Hf2Al3O12:6%Ce3+ (CY0.88Lu0.06Hf2A:Ce3+) shows a bright cyan emission band in the range of 430–750 nm with the peak at 477 nm. Importantly, the emission intensity and thermal stability properties of CY0.88Lu0.06Hf2A:Ce3+ were significantly improved by 58% and 47% compared to those of pure Ca2YZr2Al3O12:Ce3+. Small and heavy cation substitution could induce highly stable rigid structure, thus enhancing emission intensity and stability. The color rendering index increases from 84.5 to 92.0 after supplementing CY0.88Lu0.06Hf2A:Ce3+ phosphor in white light‐emitting diode devices combining commercial red, green, and blue phosphors with a violet chip, indicating its practical application in full‐spectrum lighting. The present study provides promising strategies for the design and development of efficient cyan materials for high‐quality full visible spectrum light‐emitting diode lighting.

A new cyan phosphor NaAlO2:Bi3+ with high luminescent thermal stability

Developing new phosphors is an important issue for white LED applications. Herein, a simple compound NaAlO2 with an unusual compact 5-coordinated [NaO5] polyhedral environment is selected as host material. After doping Bi3+ into NaAlO2, Bi3+ may be occupy the Na-sites and interesting luminescent properties are expected. Experimental results show that phosphor NaAlO2:Bi3+ can emit cyan light under near-UV excitation. More exciting, the luminescent intensity of NaAlO2 is rather stable under high temperatures, which is due to the good structural rigidity of NaAlO2 host lattice and the process of trap-to-activator energy transfer. At 450 K, the typical working condition of LED devices, the PL intensity constitutes 92 % of the intensity at 300 K, which can guarantee its luminous efficiency for applications in LED devices. Finally, a white LED was fabricated by using a 365 nm LED ship, and a mixture of CaAlSiN3:Eu2+ (red phosphor), BaMgAl10O17:Eu2+ (blue phosphor) and NaAlO2:0.007Bi3+. The CIE coordinates, rendering index (Ra) and Correlated Color Temperature (CCT) of this lamp are (0.3183, 0.3307), 96.8 and 4429 K. This work confirms that the NaAlO2:Bi3+ material is a promising cyan phosphor for applications in LED field.

Tunable luminescence spectra of solid solution phosphors Gd3(Sb1-yTay)O7:Bi3+ for ultrahigh color rendering index full-spectrum white light-emitting diodes

The development of efficient luminescent materials that can compensate for the cyan gap is essential for actualizing high-quality full-spectrum white light-emitting diode (wLED) illumination. In this paper, a novel blue-emitting phosphor Gd3SbO7:Bi3+ was synthesized with an emission center located at 449 nm. Based on the cation substitution strategy, the cyan-emitting Gd3TaO7:Bi3+ phosphor is developed by completely replacing Sb5+ ions with Ta5+ ions in Gd3SbO7:Bi3+. Compared with Gd3SbO7:Bi3+, Gd3TaO7:Bi3+ also has an orthorhombic phase with the space group Ccmm, except that its emission wavelength is red-shifted by 45 nm from 449 to 494 nm, and the luminescence color is changed from blue to cyan. Thermal stability measurements demonstrate the negative effect of increasing Ta5+ doping concentration on the thermal stability of Gd3SbO7:Bi3+ phosphors. And a full-spectrum wLED device was fabricated using Gd3SbO7:Bi3+, Gd3TaO7:Bi3+, commercial (Sr, Ba)2SiO4:Eu2+ and CaAlSiN3:Eu2+ phosphors, with an impressive color rendering index (Ra = 94.7, R9 = 93) and suitable correlated color temperature (5832 K). The research results demonstrate the important role of Gd3TaO7:Bi3+ phosphors in compensating the cyan gap, and also provide new insights into the application of cyan phosphors in full-spectrum white light illumination.

Improved thermal stability and quantum efficiency of novel cyan phosphors toward full-visible-spectrum lighting

Highly efficient cyan phosphors have been identified as essential components in addressing the cyan gap present in the emission spectra of traditional white light emitting diodes. Here, we report novel Ba4Ca1-yLay(PO4)3Cl:Eu2+ (y = 0–0.15) phosphors with broadband cyan emission based on an efficient and positive cationic heterovalent substitution strategy. Under the near ultraviolet excitation, the quantum yield and thermal stability are progressively enhanced by introducing La3+ to replace the Ca2+ ions, owing to the band gap and killer centers engineering. The Ba3.92Ca0.9La0.1(PO4)3Cl:0.08Eu2+ phosphor exhibits a pronounced emission band in the cyan-green spectral range with a high internal quantum efficiency of 88.0% and an impressive external quantum efficiency of 72.1%. The utilization of Ba3.92Ca0.9La0.1(PO4)3Cl:0.08Eu2+ as the cyan emitting component in the fabrication of white light-emitting diode (WLED) has demonstrated remarkable advancements in the color rendering index value, emphasizing the potential of these phosphors for future implementation in the next generation full-visible-spectrum WLED lighting. Our findings offer evidences that defect engineering techniques effectively enhance the performance of light-emitting diode (LED) phosphors.

A potential cyan phosphor for full spectrum light-emitting diodes: Bi3+ activated SrBaGdGaO5 phosphor

Bi3+ activated phosphors show potential applications in white light emitting diodes. Here, Bi3+ activated SrBaGdGaO5 phosphors with different Bi3+ concentrations were prepared. The phase and oxidation states, absorbance/excitation/emission spectra, decay characteristics, and thermostability were researched. Depending on excitation of NUV light, the Bi3+ activated SrBaGdGaO5 phosphors emit cyan light originating from the radiative 3P1 → 1S0 transitions of Bi3+. On the basis of temperature-dependence emission spectra, the activation energy was calculated as 0.305 eV. The warm white light with a correlated color temperature of 4106 K and a color rendering index of 89.2 was emitted by the WLED device consisting of near ultraviolet LED chips, SrBaGdGaO5:Bi3+ and CaAlSiN3:Eu2+ phosphors. The luminescence performance of the cyan SrBaGdGaO5:Bi3+ phosphors indicates that they can remedy the cyan absence for full spectrum white lighting emitting diodes.

A Novel Cyan Phosphor (K,Rb)3GdSi2O7:Ce3+ for Full‐Spectrum Lighting through Local Structure Tailoring

AbstractCrystal‐field engineering can obtain targeted emission more effectively, compared with the laborious experimental screening of new hosts. However, there still lack of paradigms for obtaining Ce3+‐doped cyan phosphors by crystal‐field engineering, and the correlation between the emission and the local structure of the Ce3+ ions has rarely been disclosed. Herein, through substituting the K+ in K3‐yRbyGdSi2O7:Ce3+ with Rb+, the emission color changes from yellow‐green to cyan and finally to blue. In addition, the emission intensity and thermal stability greatly improve, as the internal quantum efficiency increases from 39.4% (y = 0) to 83.6% (y = 1.2), and the thermal activation energy increases from 0.25 eV (y = 0) to 0.36 eV (y = 1.2). The optimized luminescent properties have been interpretated from the change in energy level splitting and configuration coordinate of Ce3+, both of which originate from the elongated Ce3+─O2− bonds. Finally, the cyan‐emitting phosphor K1.8R1.2GSO:Ce3+ is applied to bridge the cyan gap in a fabricated white light‐emitting diodes, and the color rendering index is improved from 90.8 to 93.4. This work not only provides an efficient cyan phosphor, but also highlights an avenue for the rational design of phosphors with optimal luminescent properties.

Regulation of Bi3+ emission in Ca3Ga4O9 phosphors through doping concentration and solid-solution component design

Cyan phosphors that emit light in the 480–520 nm range are crucial to achieving high-quality full-spectrum lighting with superior color rendering index and color temperature. In this study, we employed doping concentration and solid-solution component design strategies to control the luminescence properties of Ca3Ga4O9 (CGO): Bi3+ phosphors. CGO crystallized in the orthorhombic crystal system with a Cmm2 (35) space group and exhibited a band gap energy of 4.56 eV. Optimal excitation at 345 nm resulted in CGO: xBi3+ with asymmetric emission spectra in the 370–650 nm range, with a peak at 490 nm. These spectra can be decomposed into two distinct peaks: the long-wave peak Bi(1) at 495 nm, resulting from the occupation of Ca(Ⅰ) (CaO6) by Bi3+, and a short-wave peak Bi(2) at 445 nm, resulting from the occupation of Ca(Ⅱ) (CaO8) by Bi3+. Furthermore, the introduction of Sr2+ ions led to enhanced emission from Bi(2) ions and reduced emission from Bi(1) ions, resulting in tunable luminescence. The decrease in decay lifetime indicated the migration of Bi3+ ions from the luminescence center Ca(Ⅰ) to Ca(ⅠⅠ). The quantum yield and activation energy of the CGO: 0.01Bi3+, 0.7Sr2+ phosphor were 28.82% and 0.3469 eV, respectively. Lastly, the color rendering index values of the LED devices based on CGO: 0.01Bi3+, 0.7Sr2+ were high (R5 = 96.9 and R12 = 90.0), indicating its potential as a broadband cyan phosphor for full-spectrum LED applications.

Efficient blue-light-excited cyan-emitting CaLu2HfScAl3O12:Ce3+ phosphors for full-visible-spectrum warm-white LEDs

Bright cyan-emitting phosphor is indispensable to fill the cyan gap for the fabrication of full-visible-spectrum warm-white light-emitting diodes (LEDs) with high color rendering index (CRI). In this study, we demonstrate a novel efficient cyan-emitting Ce3+-activated CaLu2HfScAl3O12 (CLHSA) garnet phosphor for application in blue-light-excited full-spectrum warm-white LEDs. CLHSA:Ce3+ phosphors show broadband excitation spectra in the 300–470 nm spectral range with a maximum peak at 408 nm, indicating they can be efficiently pumped by the blue LED chips. The optimal doping concentration of Ce3+ ions is found to be 1 mol%. Upon 408 nm excitation, the optimal CLHSA:1%Ce3+ phosphor gives rise to a bright broadband cyan emission (peak position: 498 nm; bandwidth: 97.5 nm) with CIE chromaticity coordinates of (0.2196, 0.4265) and high photoluminescence quantum yield of 64.5%. Finally, we have fabricated a blue-light-excited high-CRI warm-white LED device by employing the CLHSA:1%Ce3+ cyan phosphor, commercial YAG:Ce3+ yellow phosphor and commercial CaAlSiN3:Eu2+ red phosphor as well as a 450 nm LED chip, which demonstrates a bright warm-white light emission with a high CRI (Ra = 92.6), a low correlated color temperature (3660 K), and good CIE chromaticity coordinates of (0.3993, 0.3939) as well as a high luminous efficacy of 45 lmW−1. Therefore, this newly discovered efficient cyan-emitting CLHSA:1%Ce3+ phosphor is promising for application in blue-chip-pumped full-visible-spectrum warm-white LEDs with high CRI values.