High Internal Quantum Efficiency Research Articles

A highly thermo-stable far-red LiMgAlF6:Cr3+ phosphor for plant-growth lighting

The far-red light around 730 nm plays an important role during the plant growth. Herein, broadband far-red LiMgAlF6:Cr3+ phosphors were successfully prepared via the hydrothermal method. Under 424 nm excitation, LiMgAlF6:0.05Cr3+ exhibits an emission band peaking at 734 nm with a full-width at half maximum (FWHM) of 131 nm, due to the emission from two kinds of Cr3+. Moreover, the broad band could match well with the absorption spectrum of the plant's PFR. The phosphor not only owns a high internal quantum efficiency (IQE) of 45.6%, but also a good resistance towards to thermal quenching. Its emission intensity at 150 °C is 93.9% of the initial intensity at room temperature. Finally, the LiMgAlF6:Cr3+ powder was combined with a 460 nm blue chip to form one LED device, which was carried out on the growth of the tomato plants. The LED based on LiMgAlF6:Cr3+ can promote the growth of tomato plants, indicating the feasibility of phosphors for the plant-growth lighting.

Investigations on the high performance of InGaN red micro-LEDs with single quantum well for visible light communication applications

In this study, we have demonstrated the potential of InGaN-based red micro-LEDs with single quantum well (SQW) structure for visible light communication applications. Our findings indicate the SQW sample has a better crystal quality, with high-purity emission, a narrower full width at half maximum, and higher internal quantum efficiency, compared to InGaN red micro-LED with a double quantum wells (DQWs) structure. The InGaN red micro-LED with SQW structure exhibits a higher maximum external quantum efficiency of 5.95% and experiences less blueshift as the current density increases when compared to the DQWs device. Furthermore, the SQW device has a superior modulation bandwidth of 424 MHz with a data transmission rate of 800 Mbit/s at an injection current density of 2000 A/cm2. These results demonstrate that InGaN-based SQW red micro-LEDs hold great promise for realizing full-color micro-display and visible light communication applications.

Mn2+ doped LiBaF3 fluoride perovskite single crystal with broadband infrared luminescence pumped by blue LED

In this study, Mn2+ ions doped lithium barium fluoride single crystals (LiBaF3: Mn2+) with perovskite structure were successfully prepared by a reformative Bridgman technique. A near-infrared (NIR) emitting broadband of the single crystal with a peak wavelength of 767 nm and a full width half maxima (FWHM) of 77 nm is owing to the 4T1g(4G)→6A1g(6S) transition of the Mn2+ ions in strong crystal field. Mn2+ ions replace the lattices of Li+ ions from the results of Rietveld structure refinements of the crystals performed by General Structure Analysis System (GSAS) program. A high internal quantum efficiency (41.4%) can be obtained in the synthesized single crystal upon excitation of 494 nm, and the emission intensity of this single crystal at 473 K remains at 42.9% of that at 298 K. Therefore, the LiBaF3: Mn2+ single crystal is a promising candidate for NIR solid-state light-emitting material due to its effective broadband NIR emission. This work offers a novel route to rational design of efficient broadband NIR luminescence and provides a new insight into Mn2+ luminescence and its applications.

Electron-Beam-Pumped UVC Emitters Based on an (Al,Ga)N Material System.

Powerful emitters of ultraviolet C (UVC) light in the wavelength range of 230-280 nm are necessary for the development of effective and safe optical disinfection technologies, highly sensitive optical spectroscopy and non-line-of-sight optical communication. This review considers UVC emitters with electron-beam pumping of heterostructures with quantum wells in an (Al,Ga)N material system. The important advantages of these emitters are the absence of the critical problem of p-type doping and the possibility of achieving record (up to several tens of watts for peak values) output optical power values in the UVC range. The review consistently considers about a decade of world experience in the implementation of various UV emitters with various types of thermionic, field-emission, and plasma-cathode electron guns (sources) used to excite various designs of active (light-emitting) regions in heterostructures with quantum wells of AlxGa1-xN/AlyGa1-yN (x = 0-0.5, y = 0.6-1), fabricated either by metal-organic chemical vapor deposition or by plasma-activated molecular beam epitaxy. Special attention is paid to the production of heterostructures with multiple quantum wells/two-dimensional (2D) quantum disks of GaN/AlN with a monolayer's (1 ML~0.25 nm) thickness, which ensures a high internal quantum efficiency of radiative recombination in the UVC range, low elastic stresses in heterostructures, and high-output UVC-optical powers.

Steady-state and dynamic characteristics of deep UV luminescence in rock salt-structured MgxZn1−xO

Temperature-dependent cathodoluminescence spectra were measured for rock salt-structured MgxZn1−xO films with x = 0.95–0.61. The Mg0.95Zn0.05O film exhibited the shortest deep UV peak wavelength of 199 nm (6.24 eV) at 6 K. Relatively high equivalent internal quantum efficiencies of 0.9%–11% were obtained. The Tauc plots, which were obtained from temperature-dependent optical transmittance measurements, exhibited large Stokes-like shifts of 0.7–0.9 eV at 6–300 K. Time-resolved photoluminescence (PL) signals at 7 K exhibited fast and slow decay components. The fast decay component had PL lifetimes of 2.59–3.08 ns, and the slow decay component far exceeded the measurement time range of 12.5 ns. The fast decay constant reflected the transfer lifetime of the photoexcited carriers to certain trapping centers. These centers were tentatively ascribed to Zn-related isoelectronic trapped-hole centers and may be a cause of the large Stokes-like shifts. The signals at 300 K exhibited very short PL lifetimes of 120–180 ps. The PL lifetimes were mainly attributed to the nonradiative recombination lifetime. Simultaneous decreases in the Zn-related isoelectronic trapped-hole centers and the nonradiative recombination centers were found to be necessary to improve the DUV emission properties of RS-MgxZn1−xO films.

Intrinsically Stretchable Phosphorescent Light-Emitting Materials for Stretchable Displays.

Intrinsically stretchable organic light-emitting diodes (is-OLEDs) have attracted significant attention for use in next-generation displays. However, most studies conducted to date have focused on how to make fluorescent materials stretchable, utilizing singlet excitons with a theoretical internal quantum efficiency (IQE) of 25%. Although phosphorescent materials have a high theoretical IQE of 100%, no previous work has attempted to develop stretchable phosphorescent light-emitting materials. In this work, we designed a solution-processable and intrinsically stretchable phosphorescent light-emitting layer (isp-EML) by blending various additives together with a mixture of a polymer host, poly(9-vinyl carbazole) (PVK), and a small-molecule emitting dopant, tris(2-phenylpyridine)iridium(III) (Ir(ppy)3). The poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG) additive significantly improved the stretchability (∼100% strain), brightness (∼5400 cd/m2), and efficiency (∼25.3 cd/A) of the isp-EML compared with a conventional phosphorescent EML (approximately 3% strain, 3750 cd/m2, and 12.1 cd/A). Furthermore, by changing the emitting dopant in the isp-EML, we could control the red, green, and blue emission colors, with increasing mechanical and electrical properties of the isp-EML. These results highlight the promising potential of the novel blend system using phosphorescent materials and additives for application in highly stretchable and efficient OLEDs.

Metamorphic front- and rear-junction 1.7 eV GaInP solar cells with high open-circuit voltage

1.7 eV absorber materials are important in high-performance III-V multi-junction solar cells. Here, we show that rapid thermal annealing significantly improves the carrier lifetimes in lightly doped metamorphic 1.7 eV Ga0.37In0.63P (MM GaInP) grown on GaAs by molecular beam epitaxy. A low threading dislocation density of ∼6 × 105 cm−2 was achieved through the use of an InxGa1-xAs graded buffer. Annealing enables minority carrier lifetimes in 1.7 eV p- and n-GaInP of 3.9 and 28 ns, respectively, both of which are higher than annealed lattice-matched 1.9 eV Ga0.51In0.49P (LM GaInP) grown in the same chamber. With the benefit of annealing, MM 1.7 eV GaInP front-junction solar cells show a high peak internal quantum efficiency of 94.3% and an open-circuit voltage (VOC) of 1.17 V. We also demonstrate the first MM 1.7 eV GaInP rear-heterojunction cells with high fill factor and VOC of 85% and 1.21 V, respectively, by taking advantage of long carrier lifetime while eliminating majority carrier blocking. The high VOC values for the 1.7 eV GaInP cells presented in this work indicate promising tolerance to threading dislocations in MM GaInP.

Highly bright broadband cyan-emitting CaLu2HfGaAl3O12:Ce3+ garnet phosphors for high-color-quality white light-emitting diodes

In this work, novel highly efficient cyan-emitting Ce3+-activated CaLu2HfGaAl3O12 (abbreviated as CLHGAO) garnet-structured phosphors were synthesized using the high-temperature solid-state reaction route. Rietveld refinement results demonstrate the as-prepared samples belong to cubic space group Ia3‾d. These CLHGAO:xCe3+ (x = 0.5–8%) phosphors possessed a broad absorption band in the 320–450 nm wavelength range with a maximum at 408 nm. Upon 408 nm excitation, the CLHGAO:0.5%Ce3+ sample showed a broad cyan emission band within 425–750 nm wavelength range (emission peak: 493 nm; bandwidth: 95 nm), along with CIE color coordinates of (0.1939, 0.3533) and a high internal quantum efficiency of 81.9%. It is observed that, with increasing Ce3+ doping concentration from 0.5% to 8%, the emission peak position of CLHGAO:xCe3+ moves from 493 nm to 527 nm, and the corresponding emission color changes from cyan to green. Besides, the thermal stability and color stability of CLHGAO:0.5%Ce3+ phosphor at high temperature are also studied. A white LED device was fabricated by utilizing a 395 nm LED chip with as-prepared CLHGAO:0.5%Ce3+ cyan-emitting phosphor and commercial (Ba,Sr)2SiO4:Eu2+ green-emitting phosphor and commercial CaAlSiN3:Eu2+ red-emitting phosphor, and it demonstrates a high-color-quality white light with high color rendering index of 91, low color correlated temperature of 3547 K and good luminous efficacy of 58.71 lmW−1.

Optimization of Doping Concentration to Obtain High Internal Quantum Efficiency and Wavelength Stability in An InGaN/GaN Blue Light-Emitting Diode

We conduct a comprehensive study to investigate the feasibility of achieving high internal quantum efficiency (IQE) and wavelength stability in an InGaN/GaN blue light-emitting diode (LED) through numerical simulations with different doping concentrations. To ensure accurate calculations, we emulated the structure of an LED, fabricated on freestanding GaN with low defect density, abrupt interfaces, and high-performing characteristics, which resemble ideal conditions. Our objective is to determine the optimal doping concentration of the claddings using the Quantum Drift-Diffusion (QDD) model. We tested three concentrations ( ), and found that produced the highest IQE of 82.5%, the most stable wavelength in the range of (0.08–63.25) mA, an optical power of mWs−1, and a forward voltage of V at 20 mA. We suggest that using this concentration leads to the parameters closest to those of the reference device.

Mode-Locking and Noise Characteristics of InAs/InP Quantum Dash/Dot Lasers

The mode-locking and noise characteristics of InP/InAs quantum dash (QDash) and quantum dot (QDot) multi-wavelength lasers, showing identical structural design, operating at the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> -band, are investigated and compared to each other. The QDash lasers exhibit improved repetition frequency stability with a lower threshold current and cavity loss. On the other hand, the QDot lasers show higher quality repetition frequency tunability with higher internal quantum efficiency, as well as lower average integrated relative intensity noise (RIN) and average optical linewidth. Furthermore, we demonstrate both the QDash and QDot lasers exhibit very clean constellation diagrams at 32 GBaud 16QAM base-band signal, while the QDot lasers' bit-error ratio (BER) performance outperforms the QDashes. This finding highlights the viability of InAs/InP QDash/QDot lasers to be used as a low-cost optical source for large-scale networks.

Cyan-to-yellow color tunable NaAlSiO4:Eu2+ with high quantum efficiency and thermal stability for white light-emitting diodes

Phosphor-converted white light-emitting diodes (white pc-LEDs) require efficient and thermal stable phosphors with broad-band emission to fulfill the requirement of high-quality illumination. In this work, Eu2+-activated nepheline, NaAlSiO4:Eu2+ with tunable emission was synthesized successfully. The emission band can be tuned from cyan to yellow region through changing flux, synthetic temperature, and/or Eu2+ doping content without changing crystal structure. The tunable emission is due to the variation of occupancy of Eu2+ on two different Na crystallographic sites. Results indicate that using H3BO3 as flux, increasing synthetic temperature and Eu2+ content are beneficial to efficient yellow emission of NaAlSiO4:Eu2+. Na0.92AlSiO4:0.04Eu2+ synthesized at 1300 °C with H3BO3 has high internal (95.14%) and external (78.14%) quantum efficiencies. It also exhibits excellent thermal stability that the emission intensity keeps nearly unchanged within 100 °C. The fabricated proto type white pc-LED by using the phosphor as a yellow component has a color rendering index of 92.0. These results indicate that the as-synthesized phosphors have great potential for application in white pc-LED devices.

Highly efficient far-red emitting Mn4+-activated Li3La3W2O12 phosphors for plant growth LED lighting

High-efficiency far-red emitting phosphors with an emission peak of around 730 nm are urgently needed for indoor plant growth light-emitting diode (LED) lighting. In this article, we report on the synthesis, crystal structure, and luminescence properties of a new highly efficient Mn4+ ion-activated Li3La3W2O12 (LLWO) far-red emitting phosphor. A group of LLWO:Mn4+ phosphors doped with different Mn4+ ion concentrations have been prepared via the conventional high-temperature solid-state reaction route. X-ray diffraction Rietveld refinement reveals that the LLWO:Mn4+ phosphor has the monoclinic structure with space group P21/n, along with lattice parameters of a = 5.5396 Å, b = 5.6026 Å, c = 7.8802 Å, α = γ = 90°, β = 90.0988°, and V = 244.57 Å3. Interestingly, LLWO:Mn4+ phosphors can generate bright narrowband far-red emission in the 650–800 nm wavelength range peaking at 719 nm due to the spin- and parity-forbidden 2Eg→4A2g transition of Mn4+ ions, matching well with the absorption spectrum of phytochrome PFR. The excitation spectrum monitored at 719 nm has a broad excitation band with the range from 250 to 550 nm centered at 339 nm and 472 nm, indicating that LLWO:Mn4+ phosphors could be efficiently pumped by both ultraviolet and blue LED chips. The highest far-red emission is achieved for the sample doped with 1.2 mol% Mn4+ ion, and this optimal LLWO:1.2%Mn4+ sample shows a high internal quantum efficiency of 88.4% and a decay lifetime of 2.289 ms. Commission Internationale de l’Eclairage (CIE) color coordinates of LLWO:1.2%Mn4+ are determined to be (0.7326, 0.2674). Besides, the crystal field analysis and temperature-dependent emission spectra of the as-prepared samples have been investigated in detail. The emission intensity of LLWO:1.2%Mn4+ sample at 423 K remains about 40% of that at 303 K. Finally, a LED device is fabricated by integrating the LLWO:1.2%Mn4+ phosphors and a 460 nm blue LED chip, which shows bright blue and far-red dual emission bands under 20–300 mA driving currents. This work demonstrates that these newly developed far-red emitting LLWO:Mn4+ phosphors have excellent application prospects in plant growth LED lighting.

Cation substitution induced highly symmetric crystal structure in cyan-green-emitting Ca2La1-xLuxHf2Al3O12:Ce3+ solid-solution phosphors with enhanced photoluminescence emission and thermal stability: Toward full-visible-spectrum white LEDs

Highly efficient cyan-green-emitting phosphors are urgently needed for high-color-quality full-visible-spectrum white light-emitting diodes (LEDs). Herein, we report on efficient near-ultraviolet-excited cyan-green-emitting Ca2La1-xLuxHf2Al3O12:Ce3+ (CLa1-xLuxHA:Ce3+) garnet phosphors, which are developed based on the solid-solution design of chemical cation substitution. All phosphor samples present a garnet crystal structure with the Ia3‾d space group; with increasing Lu3+ ions content, the lattice could be gradually contracted, along with a high symmetry as well as rigidity. Furthermore, under the 408 nm excitation, the cyan-green emissions of CLa1-xLuxHA:Ce3+ phosphors are progressively enhanced with a slight blue-shift, due to crystal field splitting and Stokes shift. Importantly, quantum efficiency and thermal stability performances are greatly improved by introducing smaller Lu3+ ions to replace the bigger La3+ ions, owing to the high rigidity structure with high symmetry. The optimized CLa0.5Lu0.5HA:Ce3+ phosphor exhibits an intense cyan-green emission band with high internal quantum efficiency of 76.4% and external quantum efficiency of 54.4%. Through employing the as-prepared CLa0.5Lu0.5HA:Ce3+ cyan-green phosphor, we have successfully fabricated a full-visible-spectrum LED device, demonstrating a bright warm-white light emission with an extremely high color rendering index (Ra = 98.0, R9 = 95.9, and R12 = 94.3) and low correlated color temperature (3497 K) under 100 mA driving current. This study not only reveals the correlation between the crystal structure evolution and luminescent properties of phosphor materials, but also provides new strategies for the design and development of novel efficient luminescent materials for high-quality full-visible-spectrum LED lighting.

Solution-processable red phosphorescent OLEDs based on Ir(dmpq)2(acac) doped in small molecules as emitting layer

Stable red phosphorescent materials are of high importance in OLED applications and a promising scenario relies on the organometallic emitters, such as phosphorescent dopants, constituting an effective emissive layer of OLEDs, which is usually embedded in an appropriate host matrix. Iridium (III) complexes are the most widely used dopants in Phosphorescent OLEDs because of their high internal quantum efficiency. In this work, Bis(2-(3,5-dimethylphenyl)quinoline-C,N)(acetylacetonato)iridium(III), (Ir(dmpq)2(acac)), was doped in four different small molecule host materials, such as 4,4′-Bis(N-carbazolyl)-1,1′-biphenyl (CBP), 1,3-Bis(N-carbazolyl)benzene (mCP), 1,1-Bis[(di-4-tolylamino) phenyl]cyclohexane (TΑPC) and tris(4-carbazoyl-9-ylphenyl)amine (TCTA), with doping concentrations of 4%, 6%, and 8%. Τhe net host materials and the Ir(dmpq)2(acac) were first characterized in respect of their optical and photophysical properties. Following, the doped thin films were implemented as the active layers in OLED devices, formed via the solution deposition method. It was found that OLED devices fabricated for all studied cases emit red light, a characteristic of Ir(dmpq)2(acac), with a maximum wavelength of approximately 620 nm. By exploring the different combinations between the host and the dopant, as well as the different doping concentrations, we aim to provide insights into the selection of the best performing host materials for PhOLEDs.

High-Power, High-Efficiency GaSb-Based Laser with Compositionally Linearly Graded AlGaAsSb Layer

We propose a novel graded AlGaAsSb layer growth method to achieve a super-linear interface by precisely controlling the cell temperature and valve position. Atomically smooth surface and lattice-matched epitaxy was confirmed by AFM and the HRXRD characterization of the graded AlGaAsSb layer sample. With the inserted graded layer between the cladding and waveguide layers, high-power, high-efficiency GaSb-based laser emitters and laser bars were confirmed. The linearly graded interface layer smooths the potential barrier peak between the cladding and waveguide layers, which resulted in a low turn-on voltage of 0.65 V and an ultra-low series resistance of 0.144 Ω. A maximum continuous-wave output power of 1.8 W was obtained with a high power conversion efficiency of 28% at 1.1 A and 12% at 8 A. A facet-coated laser bar was also fabricated with a record-high CW output power of 18 W. A high internal quantum efficiency of 83 was maintained at 40 °C, implying improved carrier injection efficiency, which benefits from the built-in electric field of the composition-graded AlGaAsSb layer.

Tuneable structural and optical properties of inorganic mixed halide perovskite nanocrystals

AbstractHighly fluorescent cesium lead‐based (CsPbX3, X═Br, Cl, I) inorganic metal halide perovskites semiconductors have gained immense popularity in the last decade due to the economic and straightforward fabrication techniques involved in these materials along with their excellent electrical and optoelectronic properties. Cesium lead halide nanocrystals are well known for their fluorescence in the visible region with extremely high internal quantum efficiencies; thus making them highly suitable for the fabrication of efficient light‐emitting diodes, transistors and photodetectors. Although perovskite nanocrystals (NCs) are more fluorescent compared to their bulk counterpart, there have been very few reports on the synthesis and characterization of CsPbX3 perovskite NCs. In this work, we have synthesized and investigated the CsPbBr3 and CsPbBr2I NCs to understand the fundamental optoelectronic properties and structural integrity in mixed halide perovskite NCs. We have estimated ~10 nm average particle size of CsPbBr3 nanocrystals from the high‐resolution transmission electron microscopy (HRTEM) while CsPbBr2I has ~16 nm average particle size with slightly higher polydispersity. Most interestingly, we do not observe any phase segregation of bromide and iodide ions in mixed halide perovskite quantum dots due to finite size effect. This is also confirmed by the energy dispersive X‐ray spectroscopy (EDS) mapping data. However, CsPbBr3 nanocrystals are relatively more stable than the mixed halide perovskite nanocrystals due to fewer defects. Anomalous behavior is observed in the photoluminescence intensity with the variation of precursor concentration indicating a complex nature nanoparticle synthesis.

Deep‐Red Ca3Al2Ge3O12:Eu3+ Garnet Phosphor with Near‐Unity Internal Quantum Efficiency and High Thermal Stability for Plant Growth Application

AbstractTrivalent europium (Eu3+) doped phosphors usually radiate orange or red light owing to distinct transitions from the 5D0 excited level to the ground states of 7F1 and 7F2. However, Eu3+ activated phosphors with a dominant deep‐red emission due to 5D0→7F4 transition are relatively rare. In this work, the synthesis and photoluminescence properties of Ca3Al2Ge3O12:Eu3+ deep‐red phosphor with an intense 5D0→7F4 transition are reported. Irradiating this new garnet phosphor with 394 nm near‐ultraviolet light generates a dominant deep‐red emission band centered at 707 nm. The phosphor has a high internal quantum efficiency of 98.4% and excellent luminescence thermal stability, maintaining 78.8% of the room temperature emission intensity at 150 °C. Based on the unique spectral feature of this new compound, a phosphor‐converted deep‐red LED prototype device is fabricated, producing an output power of 27.3 mW with a photoelectric conversion efficiency of 4.0% at 200 mA. Plant growth experiments are also conducted to demonstrate the obvious positive effects of the fabricated deep‐red LED on plant growth, further indicating that the as‐prepared Ca3Al2Ge3O12:Eu3+ deep‐red phosphor can act as a promising luminescence converter for plant growth LED bulbs.

Luminescent Amorphous Silicon Oxynitride Systems: High Quantum Efficiencies in the Visible Range.

In recent years, researchers have placed great importance on the use of silicon (Si)-related materials as efficient light sources for the purpose of realizing Si-based monolithic optoelectronic integration. Previous works were mostly focused on Si nanostructured materials, and, so far, exciting results from Si-based compounds are still lacking. In this paper, we have systematically demonstrated the high photoluminescence external quantum efficiency (PL EQE) and internal quantum efficiency (PL IQE) of amorphous silicon oxynitride (a-SiNxOy) systems. Within an integration sphere, we directly measured the PL EQE values of a-SiNxOy, which ranged from approximately 2% to 10% in the visible range at room temperature. Then, we calculated the related PL IQE through temperature-dependent PL measurements. The obtained PL IQE values (~84% at 480 nm emission peak wavelength) were very high compared with those of reported Si-based luminescent thin films. We also calculated the temperature-dependent PL EQE values of a-SiNxOy systems, and discussed the related PL mechanisms.

Simultaneously improve the Purcell factor and internal quantum efficiency of light-emitting diodes via surface plasmon by metal conic structure

Recent advances in the development of surface plasmons (SPs) enhanced LED have provided a great opportunity to enhance either the internal quantum efficiency (IQE) or the spontaneous emission rate (SE) by employing specific metal structures. However, it is still challenging to simultaneously achieve high IQE and Purcell factor (Fp), which demonstrates the SE enhancement, without sacrificing the electrical performance of LEDs. Herein, we designed and investigated a conic metal structure applied to LEDs by comprehensively considering the electrical, optical, and data transmission performance of devices. Conic structures with various heights were implemented to investigate the variation trends of IQE and Fp with the structure design, accompanied by the planar structures as references. A more than five times increase in IQE and almost five times increase in Fp were demonstrated experimentally even with a coupling distance of 100 nm, by employing this conic structure. The theoretical analysis was verified by the experimental results and revealed the mechanism of high Fp and IQE toward high SP–photon coupling efficiency and initial IQE. This study provides a universal strategy to enhance the performance of luminous efficiency and modulation speed of LEDs without sacrificing electrical properties, making them viable for the integration of lighting, display, and communication.

BaCa13Mg2(SiO4)8: Ce3+ — A blue phosphor with high brightness, high internal quantum efficiency and excellent thermal stability for w-LEDs

In this paper, a series of Ce3+ ions doped BaCa13Mg2(SiO4)8 blue phosphors were synthesized via a conventional high-temperature solid-state method. Calculations by DFT confirmed that the BaCa13Mg2(SiO4)8 host had a suitable band gap for doping rare earth ions. In terms of luminescence performance, BaCa13Mg2(SiO4)8: Ce3+ blue phosphor with an optimal excitation wavelength of 365 nm can effectively absorb light from 310 to 400 nm and produce a wide emission band centered at 440 nm with an internal quantum efficiency of 71.39%. Based on the analysis of the structure and Gaussian fitting spectra, the Ce3+ ion can occupy all of the Ba2+ and Ca2+ ion lattice positions. After charge compensation by K+ ions, the emission intensity can be increased by 36.8%, and the emission intensity at 140 °C can still maintain 88.7% compared with that at room temperature. Under 365 nm excitation, the integral intensity of the emission spectrum BaCa13Mg2(SiO4)8: 3% Ce3+, 3% K+ sample can reach 90.4% of that of the commercial blue phosphor BaMgAl10O17: Eu2+. When BaCa13Mg2(SiO4)8: Ce3+ phosphors are combined with green (Ba, Sr)2SiO4: Eu2+ phosphors and red CaAlSiN3: Eu2+ phosphors on a 365 nm UV-LED chip, bright LED devices with a correlated color temperature of 4172 K can be obtained. The results show that the blue phosphor BaCa13Mg2(SiO4)8: Ce3+ has great potential for w-LEDs applications.