White Light-emitting Diode Device Research Articles

Improving the quality of red light emitting from Eu3+ by Co-doping Tb3+ in LuBa3(BO3)3

The red light emitting from phosphors activated with Eu3+ is of great significance for optimizing the comprehensive performances of white light-emitting diodes (WLEDs) for solid-state lighting. Herein, LuBa3(BO3)3:Eu3+ and LuBa3(BO3)3:Tb3+,Eu3+ phosphors are synthesized via the high temperature solid-state reaction to investigate the effects of the doping concentration of Eu3+ and the co-doping of Tb3+ on the quality of red emission from Eu3+ in the host. Under the excitation of 392 nm light, the dominant emission peak of LuBa3(BO3)3:xEu3+ gradually shifts from 593 nm to 610 nm when the doping concentration of Eu3+ is increased from 0.02 to 0.10, and the quality of red light emitting from Eu3+ in the host is found to be further improved with increasing the co-doping concentration of Tb3+, both of which are explained with the Judd-Ofelt theory. The calculated results indicate that the enhancement of red emission is attributed to the decrease of the environment symmetry of Eu3+ by increasing the concentration of Eu3+ in LuBa3(BO3)3:Eu3+ or co-doping Tb3+ ions. The color purity of the emission from LuBa3(BO3)3:0.10 Tb3+,0.10Eu3+ is 94.11%, and the luminescent intensity of the phosphor at 425 K is 69% of that at room temperature. Moreover, a WLED device with the high color rendering index of 91.1 is obtained by fabricating LuBa3(BO3)3:0.10 Tb3+,0.10Eu3+ and other phosphors with a 365 nm LED chip. The good comprehensive performances suggest that LuBa3(BO3)3:Tb3+,Eu3+ has a great application prospect as a red phosphor in the field of high-quality solid lighting.

Organic dye fluorescent fibers for wearable devices

Organic fluorescent dyes are gradually gaining wide application in the fields of sensors, displays, and lighting. However, the use of organic fluorescent dyes for White light-emitting diodes (WLEDs) is still not sufficiently studied to be applied to the market. In this study, FR and FG with red and green fluorescence emission, respectively, were designed and synthesized, and two fluorescent dyes FB and FBP with aggregation-induced luminescence (AIE) properties were selected and dissolved in polyacrylonitrile (PAN) solution (in the ratio of 0.15 wt%, 2 wt%, 2 wt%, 1 wt%, respectively) to make flexible fiber films with fluorescence emission by electrostatic spinning. These fluorescent fiber films still have 78% of luminescence intensity after five days of immersion in water. The fluorescence quantum yields of the four fiber membranes were 12.89% (FR/PAN), 6.23% (FG/PAN), 39.85% (FB/PAN), 11.51% (FBP/PAN), respectively. Then 460 nm light-emitting diode (LED) chips and 365 nm LED chips were used to make WLEDs respectively with their color product coordinates (CIEs) of (0.3176,0.3256) and (0.3144,0.3158). Based on the good flexibility and mechanical strength of the fiber films, we used them to fabricate the wearable bracelet. The results indicate that the organic dye-based fluorescent fiber film has good potential for application in the field of WLED and wearable devices.

Effect of surface treatment upon luminous efficiency of YAG: Ce ceramics

AbstractFor high‐power white light‐emitting diode devices (WLEDs), phosphor ceramics were widely used because of their high thermal conductivity and temperature resistance. In this study, Y2.998Al5O12: 0.002Ce3+ ceramics were prepared via vacuum reaction sintering and treated by silicon carbide (SiC) abrasives with particle sizes of 8.6, 20, 25, 34, and 50 μm to obtain a single textured surface. The transmittance, reflectance, luminous efficiency (LE) and photoluminescence (PL) intensity of the ceramics were investigated with various surface roughness and different placement. Compared with the double polished (DP) samples, the PL intensity and LE of the single‐surface textured ceramics were greatly improved. It was shown that the roughest ceramics placed with the single polished (SP) side facing the direction of the excitation light (the SP‐forward YAG: Ce ceramics) showed the best performance.

Narrow-Band Deep-Blue Emission and Superior Thermal Stability of Fluoroaluminate Phosphor Based on Tungsten Bronze-Type Mineral Structure.

Screening novel narrow-band phosphors inspired by natural mineral structures is urgently demanded for improving the performance of phosphor-converted light-emitting diodes. In this work, a novel narrow-band deep-blue-emitting tungsten bronze-type KCaAl2F9:Eu2+ phosphor with superior thermal stability is successfully synthesized. Structural analysis shows that the representative KCaAl2F9:0.013Eu2+ phosphor crystallizes in an orthorhombic space group C2221 with a rigid network. The rigid [AlF6]3- octahedrons are linked together by sharing corners to build endless [AlF6]3-∞ chains, further stacking with each other in a highly cross-linked way to establish the rigid network of the KCaAl2F9 host. Benefiting from the rigid microenvironment, the developed phosphor not only shows a narrow-band deep-blue emission with a full width at half maximum of 45 nm and a high color purity of 92%, but it also exhibits the superior thermal stability with an emission loss of only 10% at 423 K, demonstrating its application potential in bridging the deep-blue spectral cavity toward sunlight-like full-spectrum lighting. In addition, the concentration/temperature quenching behaviors of KCaAl2F9:Eu2+ phosphor are systematically investigated. By revealing the specific structure-property relationship of tungsten bronze-type KCaAl2F9:Eu2+ phosphor, the present study provides a significant guide for identifying the novel narrow-band deep-blue-emitting component applicable to full-spectrum warm white light-emitting diode devices.

Synthesis and DFT calculation of germanium halide perovskites with high luminescent stability, and their applications in WLEDs and indoor photovoltaics

Addressing environmental pollution by entirely substituting lead is a significant concern in the field of perovskite optoelectronic devices. In this study, we used density functional theory to predict the structure and properties of the lead-free compound CsGeBr3, followed by its successful experimental synthesis. CsGeBr3 demonstrated the capability to emit white light and exhibited notable stability under UV radiation. Moreover, when combined with red-emitting MOF:Eu3+ phosphors, CsGeBr3 was effectively used to fabricate white light-emitting diode (WLED) devices. These devices exhibited a commendable color rendering index (CRI) of 92 and a correlated color temperature (CCT) of 3020 K. Furthermore, these light-emitting diode (LED) devices demonstrated their capacity to efficiently stimulate silicon solar cells, resulting in impressive photoelectric performance. We observed an increase in the open-circuit voltage, short-circuit current density, and cell impedance as the LED operating voltage increased, while the fill factor remained relatively unchanged. Given these beneficial properties, we strongly believe that lead-free CsGeBr3 holds promising potential for further research and development in the fields of WLEDs and indoor photovoltaics.

Realizing full-spectrum LED lighting with a bright broadband cyan-green-emitting CaY2ZrGaAl3O12:Ce3+ garnet phosphor

Full-visible-spectrum white light-emitting diodes (LEDs) with ultrahigh color rendering index (CRI), which are capable of offering a light source that mimics natural sunlight, have great application potentials in healthy lighting, high-resolution displays, and plant growth lighting. However, cyan gap in the 480–520 nm wavelength range is commonly existed in the emission spectra of traditional phosphor-converted white LEDs, and thus it is urgent to develop high-performance cyan-emitting phosphors to close this spectral gap for realizing full-visible-spectrum LED lighting. Herein, we demonstrate a new efficient cyan-green-emitting Ce3+-activated CaY2ZrGaAl3O12 garnet phosphor for near-ultraviolet (near-UV) pumped full-visible-spectrum warm-white LEDs. The CaY2ZrGaAl3O12:Ce3+ cyan-green phosphor has a cubic structure with the space group Ia3‾d and lattice parameters of a = b = c = 12.39645(8) Å and V = 1886.08(6) Å3. Ce3+ doping concentration dependent luminescence properties have been studied, and the highest emission intensity is obtained at 1 mol%. The optimal CaY2ZrGaAl3O12:1%Ce3+ sample shows a broad excitation band in the 300–490 nm wavelength range with peak at 409 nm due to the 4f→5d transition of Ce3+ ions. Upon 409 nm excitation, CaY2ZrGaAl3O12:1%Ce3+ produces a wide cyan-green emission band in the 425–750 nm spectral range with a peak at 514 nm and a full width at half-maximum of 110 nm owing to the 5d→4f transition of Ce3+ ions, and the corresponding CIE color coordinates and internal quantum efficiency are determined to be (0.2802, 0.4856) and 56%, respectively. Furthermore, the resulting CaY2ZrGaAl3O12:1%Ce3+ phosphor exhibits good thermal stability, and its emission intensity at 423 K is about 58% of that at 303 K. Finally, a white LED device is fabricated by employing a 395 nm near-UV chip with the phosphor blend of commercial BaMgAl10O17:Eu2+ blue phosphor, as-prepared CaY2ZrGaAl3O12:1%Ce3+ cyan-green phosphor, commercial (Ba,Sr)2SiO4:Eu2+ green phosphor and commercial CaAlSiN3:Eu2+ red phosphor, which exhibits a bright full-spectrum warm-white light with low color correlated temperature of 3334 K and ultrahigh CRI values (Ra = 97, R9 = 95.3, R12 = 90.1) for 20 mA driving current. This work provides a new perspective in designing luminescent materials for high-color-quality full-visible-spectrum LED lighting.

Study of Ba2Li2Si2O7:Eu2+ phosphor for enhancing the luminous flux of white LEDs

The best spectrum characteristics and photometric productivities of white light emitting diode (WLED) device possessing light emitting diodes (LEDs) in red rather than phosphor pc/R-WLEDs with the hue fidelity index (Rf) > 97 for correlated color temperatures (CCTs) between 2700 K and 6500 K were attained using the illumination effectiveness (LE) model. We demonstrate four practical pc/R-WLEDs that have indices of Rf and LE of 96–97 and 120–124 lm/W, respectively, under CCT values measured at 2969 K, 4468 K, 5682 K, as well as 6558 K. These LED packages use blue and red LEDs, also phosphors in green as well as yellow, with respective wavelengths of 448 nm, 650 nm, 507 nm, and 586 nm. In the comparison between phosphor-transformed WLED devices (with phosphor conversion) and quantum-dot WLED devices (QD-WLEDs), pc/R-WLEDs make an outstanding performance in competitiveness for high hue generation, particularly under small CCT values, and could eventually replace current pc-WLEDs.

Near-UV-excitable broadband green-emitting Ca2LaHf2GaAl2O12:Ce3+ garnet-type phosphors for high color rendering warm-white LEDs

Efficient broadband green-emitting phosphors are promising for application in high color rendering white light-emitting diodes (LEDs). In this paper, we report on the preparation, crystal structure and photoluminescence properties of a novel green-emitting Ca2LaHf2GaAl2O12:Ce3+ (CLaHGA) garnet-type phosphor. All these CLaHGA:xCe3+ (x = 4, 6, 8, 10, and 12 mol%) phosphors have been synthesized through using the conventional high-temperature solid-state reaction method. It has been found that the optical property of phosphors critically depends on Ce3+ content, and the optimal doping concentration of Ce3+ ions is 6 mol%. The optimal CLaHGA:6%Ce3+ sample has a cubic structure with the space group Ia3‾d and lattice parameters of a = b = c = 12.62662 Å and V = 2013.08 Å3. The CLaHGA:xCe3+ phosphors exhibit an intense absorption band in the 300–485 nm range with a peak at 421 nm, due to the spin-allowed and parity-allowed 4f→5d transition of Ce3+ ions. Upon 421 nm excitation, CLaHGA:xCe3+ phosphors give rise to bright broad green emission bands in the 435–750 wavelength region with peak ranging from 519 to 531 nm, owing to the spin-allowed and parity-allowed 5d→4f transition of Ce3+ ions. For the optimal CLaHGA:6%Ce3+ sample, its CIE color coordinates and internal quantum efficiency are determined to be (0.3135, 0.4851) and 40.7%, respectively. The full width at half maximum of CLaHGA:6%Ce3+ is much larger than the commercial (Ba,Sr)2SiO4:Eu2+ green phosphor (124 nm versus 71 nm), while its emission intensity is only about 39% of that of (Ba,Sr)2SiO4:Eu2+. Besides, the thermal stability of CLaHGA:6%Ce3+ has also been studied. A white LED device is fabricated using the synthesized CLaHGA:6%Ce3+ green phosphors, showing a bright warm-white light emission with high color rendering index of Ra = 89.7 and low correlated color temperature of 4058 K.

Reddish-orange-emitting CaLa4Ti4O15:Sm3+ phosphors with good thermal stability for WLED applications

Reddish-orange emitting CaLa4Ti4O15:Sm3+ phosphors were synthesized via a simple solid-state reaction. The synthesized CaLa4Ti4O15:Sm3+ phosphors revealed dominant excitation at 408 nm and emission at 601 nm with the 6H5/2 → 4F7/2 and 4G5/2 → 6H7/2 transitions, respectively. The transitions are governed by dipole-dipole interaction in the CaLa4Ti4O15:Sm3+ luminescent material. The morphology and crystal structure were investigated, and the material synthesis and chemical compositions were also confirmed. In a study of the effect of Sm3+ ion concentration on the luminescent properties of CaLa4Ti4O15:Sm3+ phosphors, the optimized concentration was found to be 5 mol%. The optimized phosphor powder exhibited Commission Internationale de l′Eclairage (CIE) chromaticity coordinate of (0.610, 0.390) under 408 nm illumination, and the thermal stability was also measured, exhibiting good thermal stability of about 81.7% at 423 K and 67.95% at 483 K. The white light-emitting diode (WLED) device was packaged using CaLa4Ti4O15:Sm3+ phosphors, together with commercial phosphors. The fabricated WLED device exhibited good correlated color temperature and color rendering index values of 5461 K and 83.97, respectively with (0.3341, 0.3997) CIE chromaticity coordinate. The CaLa4Ti4O15:Sm3+ materials as a reddish-orange emitting phosphor are expected to be a highly promising candidate for WLED applications.

Single-phase white light emission Ca9NaLu0.667(PO4)7: Eu2+, Mn2+ phosphor for the application of WLED

A single-phase full-spectrum emission Ca9NaLu0.667(PO4)7 (CNLP):Eu2+/Mn2+ phosphor was synthesized through the reaction to the solid state reaction at high temperature. CNLP:Eu2+ exhibits cyan light-emitting, and the luminous color of CNLP:Eu2+,Mn2+ has been adjusted from cyan then to white and finally to red by changing the content of Mn2+. The occupancy of Eu2+/Mn2+ was also analyzed by calculating the average bond length obtained using the Rietveld refinements. The energy transfer process (ET) of Eu2+ → Mn2+ was discussed in detail, and the ET efficiency could be as high as 77.81%. The internal quantum yield (QY) value of CNLP:2%Eu2+,3%Mn2+ is 49.51% at the excitation of 360 nm. CNLP:2%Eu2+,3%Mn2+ has a good thermostability. The white light-emitting diode (WLED) device showed warm white emission, which represented a low correlated color temperature (CCT) and high color rendering index (Ra). Moreover, the CCT and Ra remain within a certain range under different currents and temperatures, further demonstrating the potential application of WLEDs. These results prove that CNLP:2%Eu2+,1%Mn2+ phosphor has potential applications in the field of WLED.

Facile preparation of highly efficient Te4+-doped Rb2SnCl6 perovskites for white light-emitting diodes

Lead-free vacancy‐ordered halide double perovskite microcrystals are new alternatives to lead-based halide perovskite materials for lighting applications; however, they are limited by harsh synthesis conditions and low quantum efficiency. Hence, a facile solution recrystallization method was used to synthesize Te4+-doped Rb2SnCl6 phosphors. Via Te4+ doping, the phosphors show a yellow–green emission at 550 nm and a broadband emission line width of approximately 97 nm, achieving a high photoluminescence quantum yield of 74.2%, arising from the Te4+ 1S0 →3P1 self-trapping exciton transition. The Te4+-doped Rb2SnCl6 microcrystals are subsequently used to fabricate a white light-emitting diode device, which shows a high color-rendering index of 97.1 and a correlated color temperature of 4739 K. This work reports a facile method to synthesize alloy double perovskite phosphors, opening up new avenues for the development of environment-friendly lighting applications.

Rapid synthesis of BaMoO4 :Eu3+ red phosphors using microwave irradiation.

This study synthesized BaMoO4:Eu3+ red phosphors using the microwave method. In addition, the phase composition, morphology, and luminescence properties of the red phosphors were characterized using X-ray diffraction, field-scanning electron microscopy, and photoluminescence spectroscopy. The results revealed that doping red phosphors with different concentrations of Eu3+ does not change the crystal structure of the matrix material. The BaMoO4 :Eu3+ phosphors exhibited micron-scale irregular polyhedra, which could be excited by ultraviolet light with a wavelength of 395 nm to induce red-light emission. The optimal dosage of Eu3+ was 0.08, and the chromaticity coordinates of BaMoO4 :0.08Eu3+ phosphors were (0.5869, 0.3099). White light-emitting diode (w-LED) devices manufactured by using a combination of BaMoO4 :0.08Eu3+ phosphor and commercially available phosphors exhibited good white-light emission under the excitation of an ultraviolet chip. The BaMoO4 :0.08Eu3+ red phosphors that rapidly synthesized under the microwave field are expected to be used in w-LED devices.

A novel reddish-orange-emitting phosphor Ca3Gd7(PO4)(SiO4)5O2: Sm3+ for white light-emitting diodes

Phosphor is the decisive material in white light-emitting diodes (WLED), affecting light quality. Silica phosphate has good stability, low cost and environmentally friendly features, so it has great application potential. In this paper, a self-activated reddish-orange phosphor Ca3Gd7(PO4)(SiO4)5O2: xSm3+ was prepared by the high-temperature solid-phase method. The phase purity of the sample was verified by X-ray diffraction (XRD). The Rietveld refinement method was used to resolve further the sample structure and the location of the substitution of rare earth ions. The photoluminescence properties were studied in detail using fluorescence spectra, temperature-dependent emission spectra and other characterization methods. The electron transition and energy transfer processes of Gd3+ in Ca3Gd7(PO4)(SiO4)5O2 were analyzed. The fluorescence decay curve of the sample was obtained, which belongs to the double exponential curve, and the decay lifetime depending on the Sm3+ doping concentration was calculated. Furthermore, a WLED device was assembled, and warm white light was obtained, with a spectrum showing characteristic red emission, proving to complement the missing red component of commercial WLEDs. These results indicate that Ca3Gd7(PO4)(SiO4)5O2: xSm3+ phosphor has great potential for application.

Realizing multicolor tunable photoluminescence in La2MgTiO6: Tb3+, Eu3+ phosphors via energy transfer and application for white light-emitting diodes

The achievement of multiple emission color phosphors has a significant importance in screen display, lighting devices, and multicolor imaging, but it still faces formidable challenges. In this work, double perovskite La2MgTiO6: Tb3+, Eu3+ phosphors with tunable emissions are designed and successfully synthesized. The obtained phosphors can emit intense green (Tb3+), red (Eu3+), and yellow emissions (Tb3+/Eu3+) via varying the co-doping concentration of Tb3+ and Eu3+. The CIE coordinates exhibit an excellent linear behavior in La2MgTiO6: Tb3+, Eu3+, revealing the possibility of linear adjustment of multiple emission colors. Detailed material characterization demonstrates that the multicolor tunable emission originates from energy transfer between Tb3+ and Eu3+. The decay dynamics analysis suggests that the multipole interaction between Tb3+ and Eu3+ is quadrupole-quadrupole interaction. A white light-emitting diode device with color rendering index of 84.7, correlated color temperature of 4684 K, and CIE coordinate of (0.3472, 0.3083) is fabricated by combining La2MgTiO6: Tb3+, Eu3+ yellow phosphor and BaMgAl10O17: Eu2+ blue phosphor. Our results reveal that La2MgTiO6: Tb3+, Eu3+ phosphors are promising luminescent materials in white light-emitting diodes.

Strategic Tuning of Photophysical Response in the Polyhedral Framework of the Garnet Structure toward White Light-Emitting Devices with Enhanced Color Rendering.

Designing a single-phase phosphor with high quantum efficiency and full spectrum emission is inevitable for today's scientific world. Herein, an optimal strategy for realizing white emission in a single component matrix is envisaged based on the structure-property-design-device policy. Cationic substitution corresponding to polyhedral expansion and contraction in A2A'B2V3O12 confirms the existence of strong and intricate linkage in the garnet structure. The dodecahedral expansion causes compression of VO4 tetrahedra and a blue shift. The direct correlation of V-O bond distance with red shift validates the distortion of the VO4 tetrahedra. The interdependence of photophysical properties via cationic substitution and subsequent correlation of the V-O bond distance with emission bands enabled the tailoring of phosphor-CaSrNaMg2V3O12 with a high quantum efficiency of 52% and excellent thermal stability of 0.39 eV. Bright warm white light-emitting diode (WLED) devices are fabricated based on Eu3+ and Sm3+-activators. A high quantum efficiency-74% is obtained for the designed Eu3+ phosphor. CIE coordinates near the achromatic point (0.329, 0.366), low CCT-5623 K, and high color rendering index (CRI)-87 are obtained for the single-phase WLED device. This work puts forth a new direction for designing and engineering promising WLEDs with enhanced color rendering based on single-phase phosphors with full spectrum emission.

Enhancement on Tb3+ luminescence in CaScBO4-based ceramic phosphors by Ce3+-induced resonance energy transfer and the generation of white light emission collaborated with Mn2+

A series of Tb3+-doped, Ce3+,Tb3+-co-doped and Ce3+,Tb3+,Mn2+-tri-doped CaScBO4 (CSB) ceramic phosphors were prepared by solid-state reaction. X-ray diffraction (XRD) was taken to confirm the phase purity of all as-prepared phosphors powder. Steady-state and transient-state fluorescence spectra were applied to evaluate the luminescence properties of the phosphors. The results indicated that significant enhancement on Tb3+ luminescence was successfully realized by the Ce3+-induced resonance energy transfer and confirmed that the energy transfer from Ce3+ to Tb3+ was governed by an electronic dipole-dipole interaction. Compared to the CSB:Tb3+ phosphors whose optimal excitation located at 378 nm, the occurrence of Ce3+-Tb3+ energy transfer not only allowed the optimal excitation to peak at around 390 nm but also gifted the CSB:Ce3+,Tb3+ phosphors color tunability from blue, cyan to green. Then, two different designs of white light by the introduction of Mn2+ luminescence were performed. One was the combination of CSB:Ce3+,Tb3+ and CSB:Ce3+,Mn2+ phosphors, based on the co-excitation of the above two phosphors at the same wavelength. Another was the direct use of the tri-doped CSB:Ce3+,Tb3+,Mn2+ phosphors. Both designs succeeded in the generation of white light emission. The performance of these two designs in real devices were also studied. The direct use of the tri-doped CSB:Ce3+,Tb3+,Mn2+ phosphor in white light-emitting diode (WLED) device can produce white light with a color rendering index (CRI) up to 85.3 while the use of the CSB:Ce3+,Tb3+ and CSB:Ce3+,Mn2+ phosphors combination can just produce a value of 76.6 in CRI.

Anionic Regulation toward Bi3+ Selective Occupation for Full-Spectrum White Light Emission.

An activator's selective occupation of a host is of great significance for designing high-quality white light-emitting diode phosphors, while achieving a full-spectrum single-phase white light emission phosphor is challenging. In this study, a boron phosphate solid-solution Na2Y2(BO3)2-x(PO4)xO:0.005 Bi3+ (NYB2-xPxO:0.005 Bi3+) white phosphor was designed by selectively occupying Bi3+ activators in the mixed anionic groups. The substitutes of the anionic unit (BO3)3- by the (PO4)3- unit are supposed to force part of the Bi3+ ion to enter the Na lattice site, which produces an intense orange-red emission peaked at 590 nm. In parallel, spectral tuning from blue to white light and an internal quantum efficiency of 56.42% was obtained, and the thermal stabile luminescence intensity remains at 94.2% of the initial intensity after four heating-cooling cycles from 30 to 210 °C (luminescent intensity is 83.6% of room temperature (RT) at 150 °C, with excellent thermal stability and recovery performance). Finally, an excellent color rendering index (Ra = 90.8 and R9 = 85) was demonstrated for white light-emitting diode devices using only an NYB1.5P0.5O:0.005 Bi3+ phosphor and a near-ultraviolet (n-UV) 365 nm LED chip. This work delves into the different selective occupancy of Bi3+ ions and explores a new avenue for the design of phosphors for full-spectrum white light emission.

Polymer‐Encapsulated Halide Perovskite Color Converters to Overcome Blue Overshoot and Cyan Gap of White Light‐Emitting Diodes

AbstractCurrently, the most popular way to manufacture white light‐emitting diodes (WLEDs) is based on blue‐emitting InGaN LED chips (440–460 nm) and yellow‐emitting phosphor coating (520–700 nm) to produce white light lighting. However, because conventional white WLEDs lack the uniformly distributed continuous emission spectrum compared to natural sunlight: “blue overshoot” (extra 440–460 nm blue‐light can cause damage to the retina) and “cyan gap” (470–520 nm wavelength range). Here, a novel strategy to “kill two birds with one stone” is reported: using the stable and bright polymer encapsulated perovskite nanocrystals (PNCs) composite films as the cyan color converters that efficiently absorb the “blue overshoot” and effectively emit the cyan light to fill the “cyan gap”. A series of polymer‐encapsulated PNC films is achieved that can reach very high photoluminescence quantum yield (PL QY) of 90–95% under 450 nm blue‐light excitation. Importantly, both 370 nm UV‐excited WLED and 455 nm blue‐excited WLED devices are constructed that exhibit smoothly and evenly distributed white light without blue overshoot and cyan gap, which was not achieved before for blue‐excited cyan‐emissive materials. This study paves the way toward the application of PNC color converters in the next generation full‐visible‐spectrum WLED lighting that mimic the natural daylight.

Multimodal Luminescent Low-Dimension Cs2ZrCl6:xSb3+ Crystals for White Light-Emitting Diodes and Information Encryption.

Low-dimension perovskite materials have attracted wide attention due to their excellent optical properties and stability. Herein, Sb3+-doped Cs2ZrCl6 crystals are synthesized by a coprecipitation method in which Sb3+ ions partially replace Zr4+ ions. The Cs2ZrCl6:xSb3+ powder shows blue and orange-red emissions under a 254 and 365 nm light, respectively, due to the [ZrCl6]2- octahedron and [SbCl6]3- octahedron. The photoluminescence quantum yield (PLQY) of Cs2ZrCl6:xSb3+ (x = 0.1) crystals is up to 52.5%. According to experimental and computational results, the emission mechanism of the Cs2ZrCl6:xSb3+ crystals is proposed. On the one hand, a wide blue emission with a large Stokes shift is caused by the self-trapping excitons of [ZrCl6]2- octahedra under a 260 nm excitation. On the other hand, the luminescence mechanism of [SbCl6]3- octahedron is divided into two parts: 1P1 → 1S0 (490 nm) and 3P1 → 1S0 (625 nm). The broad-band emission, high PLQY, and excellent stability endow the Cs2ZrCl6:xSb3+ powders with the potential for the fabrication of white light-emitting diodes (WLEDs). A WLED device is fabricated using a commercial 310 nm NUV chip, which shows a high color rendering index of 89.7 and a correlated color temperature of 5333 K. In addition, the synthesized Cs2ZrCl6:xSb3+ crystals can be also successfully used for information encryption. Our work will provide a deep understanding of the photophysical properties of Sb3+-doped perovskites and facilitate the development of Cs2ZrCl6:xSb3+ crystals in encrypting multilevel optical codes and WLEDs.

NondemandingIn SituEncapsulation Route to Ultrastable Perovskite Nanocrystals for White Light-Emitting Diodes

Although tremendous advancement regarding the highly stable metal halide perovskite nanocrystals (PNCs) has been achieved, previous studies were primarily focused on green light-emitting PNCs (i.e., bromine-based PNCs). The stability of chlorine-based PNCs with a violet or blue emission property was still lagging behind that of their bromine-based counterparts. Herein, a nondemanding and versatile strategy for in situ encapsulating all-inorganic chlorine-based PNCs with multifold exceptionally high stabilities was presented. Well-ordered mesoporous silica enabled the confined growth of PNCs in its pores followed by the porosity sealing by tetramethyl orthosilicate hydrolysis, thereby rendering full encapsulation of chlorine-based PNCs in dense silica that originated from high-temperature calcination. This judiciously designed structure imparted enclosed violet/blue emitting PNCs impart with outstanding long-term stability (>1.5 year) with high photoluminescence quantum yield (i.e., 30.4%) in pure water as the result of complete isolation of PNCs from detrimental stimuli, eventually leading to the application in the white light-emitting diode device.