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The development of novel narrow-band emitting phosphors with high efficiency and stability is of great significance for WLED backlights. In recent years, the research on Bi3+-activated narrow-band emitting phosphors has gained significant attention for developing novel phosphors for WLED backlight applications. This Frontiers article presents recent advances in Bi3+-activated narrow-band emitting phosphors, encompassing their coordination environment and photoluminescence properties. The latest advancements in Bi3+-activated narrow-band emitting phosphors are categorized into four types based on host materials: germanate, silicate, borate, and other hosts. Additionally, detailed discussions are provided on the challenges associated with developing novel Bi3+-activated narrow-band emitting phosphors and potential research directions for future work. Overall, the Bi3+-activated narrow-band emitting phosphors have demonstrated great potential for WLED backlights; however, significant efforts are still required to enhance their comprehensive performance in order to meet practical application requirements. [ABSTRACT FROM AUTHOR]

The photoluminescence behaviors of bismuth-activated phosphors are fascinating and puzzling due to the existence of multi-type electronic transitions. Therefore, the development of novel bismuth-activated phosphors is an important objective of many researchers. In this work, a marvellous photoluminescence characteristic of Bi3+ ion was observed in a cubic phase of Y 3 TaO 7 (YTO), which performs multi-color light emissions, although there is only one cationic crystallographic site for accommodating Bi3+ dopant. Under near-ultraviolet (NUV) light excitation, Bi3+-activated YTO produces a considerably wide cyan light peaked at 477 nm with a full width at half maximum (FWHM) of 130 nm. Moreover, with the increase of excitation wavelength, the emission band was detected to have an extraordinary red shift from 477 to 547 nm and broadening, and its FWHM reaches up to 160 nm. Combined with the crystal and electronic structure of YTO, an interpretation was proposed to shed light on the photoluminescence behavior of Bi3+ ion in this system, which indicates that multi-type electronic transitions are supposed to produce the surprising luminescence properties of Bi3+ ion. The detailed discussion was processed in this work, which is expected to enhance people's comprehension for the luminescence behavior of Bi3+ ion. Multi-type electronic transitions induced multi-color light emitting of Bi3+ ion have been realized in tantalate.[ [Display omitted] ] [ABSTRACT FROM AUTHOR]

Developing a yellow phosphor with broadband emission covering more red‐light areas is an effective approach to achieve high‐quality solid‐state lighting. In this study, a novel yellow‐emitting nitride phosphor, Ca5Si2Al2N8:Ce3+, was successfully prepared at atmospheric pressure and lower temperatures (1300°C), and its structure‐property relation was revealed using crystal refinement, photoluminescence (PL) spectra, time‐resolved PL spectra, and density‐functional theory calculations. The results demonstrate that Ca atoms occupy three different crystallographic sites in the lattice, which are substituted by Ce3+ to form multiple luminescence centers. Thus, Ca5Si2Al2N8:Ce3+ emits strong yellow light with a maximum peak at 585 nm and a wide emission band. Compared with YAG:Ce3+, Ca5Si2Al2N8:Ce3+ has a wider emission band with a FWHM of 150 nm, which can effectively cover the green and red areas. Moreover, the sample can be fully excited by a blue LED chip due to its broad excitation band. Notably, the Ca5Si2Al2N8's tight crystal structure composed of edge‐sharing AlN4 and SiN4 tetrahedra pairs guarantee its thermochemical stability and quantum efficiency. Furthermore, Ca5Si2Al2N8:Ce3+ exhibits better thermal stability than YAG:Ce3+. The results indicate that Ca5Si2Al2N8:Ce3+ is a promising yellow phosphor for WLEDs. [ABSTRACT FROM AUTHOR]

To better meet the needs of modern science and technology for new inorganic functional materials, the exploration of new Eu2+-doped phosphors is of great significance. In this work, a zirconium-silicate yellow phosphor, K 2 ZrSiO 5 :Eu2+, was explored through theoretical calculations and systematic experiments for use in multifunctional applications. The crystal structure, electronic structure, photoluminescence (PL) and cathodoluminescence (CL) properties of K 2 ZrSiO 5 :Eu2+ were investigated in detail. As a result, owing to the open framework and the lattice with the covalent connection, K 2 ZrSiO 5 :Eu2+ phosphor exhibits strong yellow light emission under the near-ultraviolet and electron beam excitation. However, the K 2 ZrSiO 5 :Eu2+ phosphor suffers a poor thermal stability. Furthermore, the K 2 ZrSiO 5 :Eu2+ phosphor exhibits good anti-saturation and anti-aging characteristics under the electron beam excitation. The results indicate that the development of K 2 ZrSiO 5 :Eu2+ phosphor can provide a new insight into discovering multifunctional materials. [ABSTRACT FROM AUTHOR]

LiCaAlN2:Eu3+/Tb3+ red/green phosphors were successfully prepared by conventional solid-state reaction. The photoluminescence ( PL) properties and cathodoluminescence ( CL) properties of LiCaAlN2:Eu3+/Tb3+ were investigated in detail. The Eu3+ (Tb3+) doped LiCaAlN2 shows red (green) emission peaking at 615 nm (550 nm). Monitored at 615 nm (550 nm), it is interesting to found that LiCaAlN2:Eu3+ (LiCaAlN2:Tb3+) has a broad charge transfer transition in the range of 350-450 nm (275-375 nm) peaking at 380 nm (343 nm), which can be efficiently excited by n- UV light-emitting diodes ( LEDs). Under electron beam excitation, LiCaAlN2:Tb3+ exhibited a good resistance to the current saturation. The white LED has also been fabricated with blue, green, and LiCaAlN2:Eu3+ red phosphor. The results indicate that LiCaAlN2:Eu3+/Tb3+ could be conducive to the development of phosphor-converted LEDs and field emission displays ( FEDs). [ABSTRACT FROM AUTHOR]

A series of novel Bi3+-doped Ba3Sc4O9 phosphors were synthesized through the solid-state reaction. Their photoluminescence, decay curves, and thermal quenching properties were investigated in detail. The Ba3Sc4O9:Bi3+ phosphors could be efficiently excited in the ultraviolet and near-ultraviolet region (300-400 nm), and the photoluminescence properties possess an obvious site-selected excitations phenomenon. When excited at the ultraviolet light (320-360 nm), the phosphors present a green or a bluish green emission, and when excited at the near-ultraviolet light (370-390 nm), the phosphors always show a yellow emission. The emission spectra excited at the different wavelength can be decomposed into four components, which accord with the four cationic sites in the structure of Ba3Sc4O9. The influence of the Bi3+ concentration on the photoluminescence properties is also investigated. Upon excitation at 330 and 377 nm, the Ba3Sc4O9:Bi3+ both have good thermal quenching properties; their emission intensity of the peak at 150°C both exceed 60% of the initial value. The above results indicate that the Ba3Sc4O9:Bi3+ phosphor is a promising candidate to provide green or yellow components for UV or near- UV LEDs. [ABSTRACT FROM AUTHOR]

The undoped and Eu 2+ /Ce 3+ doped Ca 3 Li 4-y Si 2 N 6-y O y (0≤y≤1.5) (CLSN) were successfully prepared by solid-state reaction and their luminescence properties were studied. The undoped CLSN shows red defect-related luminescence with maximum emission intensity at 710 nm, Eu 2+ and Ce 3+ doped CLSN also show red emission centered at 702 nm and 673 nm, respectively. The electronic structure and the thermal stability of CLSN were investigated in this work. The results indicate that CLSN:Eu 2+ /Ce 3+ could be conducive to the development of phosphor-converted light-emitting diodes. [ABSTRACT FROM AUTHOR]

In allusion to the problems existing in the defect-related luminescent materials, a series self-activated light emitting semiconductors of Li3AlN2: R ( R=0, Na+, Mg2+, Si4+, Tb3+, Eu3+) have been successfully synthesized by sample-pressure sintering. Under the excitation at 422 nm, a yellow light peaked at 580 nm have been observed in the host lattice of Li3AlN2. The crystal structure and the electron structure of Li3AlN2 have been measured to investigate the defect-related luminescent properties of Li3AlN2 using the Rietveld refinement on the basic of X-ray diffraction data and the density functional theory (DET). The results show that Li3AlN2 crystallizes in cubic phase with full filled edge-shared (Al/Li)N4 tetrahedrons and is a wide-bandgap semiconductor. The impurity defects produced by ions substitution have also been investigated, which leads to the red-shift of the emission peak. Finally, the photoluminescence excitation (PLE) spectrum of Li3AlN2 with two excitation bands peaked at 300 nm and 422 nm has been detected, and the latter matches well with near-UV LED chips. The thermal stability shows that integral intensity of Li3AlN2 at 150°C still has 60% of the initial intensity at room temperature. The results indicate their potential applications as the LED used phosphors. [ABSTRACT FROM AUTHOR]

In this study, a series of novel single-phased white light-emitting phosphors, Sr(7.3−x/2−y/2)Ca(2.7−x/2−y/2)(PO4)6F2:xEu2+,yMn2+ (0 ≤x≤ 0.06, 0 ≤y≤ 0.9) (SCPF:xEu2+,yMn2+), have been successfully prepared through a high temperature solid-state reaction. The crystal structure and photoluminescence have been measured and analyzed. The energy transfer mechanism is demonstrated to be a quadrupole–quadrupole interaction and the critical distance between the Eu2+ and Mn2+ has been calculated. Meanwhile, the efficiency η of the energy transfer from Eu2+ to Mn2+ can reach 76%. The excitation spectra monitored at 457 nm ranges from 290 nm to 400 nm. Under excitation at 365 nm, the emission spectra include two broad bands peaked at 458 nm and 570 nm. By changing the ratio of Eu2+/Mn2+, the emission color can change from blue to white. Furthermore, our results give the Commission International de L'Eclairage (CIE) chromaticity coordinates for the white LED as (0.334, 0.307) and a correlated color temperature of 3982 K, which indicates that the SCPF:Eu2+,Mn2+ phosphor is a very promising candidate for use as a near ultraviolet (NUV) white light-emitting diode (WLED) phosphor. [ABSTRACT FROM AUTHOR]

A high bright yellow-emitting phosphor has been realized in Bi3+-activated Ba 2 YGaO 5 used for NUV-LED chip-induced healthy lighting. [Display omitted] • A novel high-bright yellow phosphor of Ba 2 YGaO 5 : Bi3+ has been synthesized. • Ba 2 YGaO 5 : Bi3+ emits a broad yellow light with good thermal stability. • Ba 2 YGaO 5 : Bi3+ shows significant cathodoluminescence properties. • A healthy lighting was realized by combining Ba 2 YGaO 5 : Bi3+ and NUV-LED chip. Based on the wide application of Bi3+-activated phosphors in Near-ultraviolet light-emitting diode (NUV-LED) chips for inducing healthy lighting, it is necessary to reveal the characteristics of high-quality Bi3+-activated phosphors. In this study, a high bright yellow light is realized with Bi3+-activated Ba 2 YGaO 5 , showing an Internal quantum efficiency (IQE) of up to 92%. Under 350 nm excitation, Ba 2 YGaO 5 : Bi3+ emits a broad yellow light peak at 587 nm with full width at half maximum (FWHM) of 135 nm, while simultaneously exhibiting good thermal stability; these results are superior to those of the commercial yellow phosphor Y 3 Al 5 O 12 : Ce3+. Moreover, significant cathodoluminescence properties are observed with Ba 2 YGaO 5 : Bi3+. These excellent luminescence properties are demonstrated to result from the D-level state described as the Metal-to-metal charge transfer (MMCT) state. Combined with the crystal and electronic structure of Ba 2 YGaO 5 , the origin of the D-level state along with its luminous mechanism is investigated in detail in this work, which may pave the way for developing more high-quality Bi3+-activated phosphors for use in NUV-LED chip-induced healthy lighting. [ABSTRACT FROM AUTHOR]

In order to obtain white light, based on near-ultraviolet (n-UV) chip needs highly efficient red, green and blue phosphor. The popular commercial blue phosphor is BaMgAl 10 O 17 :Eu2+ (BAM:Eu2+). However, BAM:Eu2+ is unstable at high temperature and the excitation band of BAM:Eu2+ couldn't match well with n-UV (380–420 nm) chips. Therefore, the development of new blue phosphor is important. In our work, a novel Eu2+ doped Na 2 HfSi 2 O 7 phosphor is successfully synthesized through the high-temperature solid-state method. Na 2 HfSi 2 O 7 :Eu2+ shows a strong wide absorption band peaking at 397 nm, covering the spectral scope from 250 to 450 nm on account of the 4f7 → 4f65 d1 transitions of Eu2+ ions. Under the optical excitation, The phosphor exhibits an asymmetric narrow-band emission centered at 460 nm with FWHM of 54 nm. Owing to the characteristics of wide-excitation and narrow-band emission, Na 2 HfSi 2 O 7 :Eu2+ is a promising candidate for n-UV WLED. • A novel narrow-band blue-emitting phosphor Na 2 HfSi 2 O 7 :Eu2+ was designed and synthesized. • The phosphor shows a wide-band absorption band peaking at 397 nm, which could match better with n-UV (380∼420 nm) chips than BaMgAl 10 O 17 :Eu2+ (λ max =350 nm). • A WLED lamp with high Ra (92.6) and low CCT (4617 K) was fabricated. [ABSTRACT FROM AUTHOR]

• A novel yellow-emitting phosphor Li 2 CaSi 2 N 4 :Ce3+ was designed and synthesized. • With the increase of Ce3+ concentration, the emission light could transfer from green to yellow region. • The phosphor does not exhibit thermal quenching up to 200 °C, the phosphor shows better thermal and color stability than YAG:Ce3+. • The phosphor possesses a wider emission band and contains more cyan and red components than YAG:Ce3+. Phosphor-converted white light-emitting diodes (pc-WLEDs) are bringing revolutionary changes to the lighting industry. To promote technological development, phosphors with tunable photoluminescence and excellent thermal stability are required. In our work, a novel tunable yellow-green emitting phosphor Li 2 CaSi 2 N 4: Ce3+ is successfully synthesized through solid-state reaction. With the increase of Ce3+ concentration, the emission light could transfer from green to yellow region and the full width at half-maximum (FWHM) increases from 123 to 165 nm. Meanwhile, the phosphor does not exhibit thermal quenching up to 200 °C. The phosphor possesses a wider emission band and contains more cyan and red components than YAG:Ce3+. Combing Li 2 CaSi 2 N 4: Ce3+ phosphor with a blue chip, pc-WLED with excellent technical indicators was obtained. Under the low voltage and current conditions, the phosphors also exhibit perfect stability with high current saturation. [ABSTRACT FROM AUTHOR]

• A novel yellow-green emitting phosphor Na 2 HfSiO 5 :Eu2+ was designed and synthesized. • The phosphor was obtained by structural derivation method which provides a strategy for finding novel phosphors. • A WLED lamp with high Ra (90.0) and low CCT (3875 K) was fabricated. • The phosphor exhibits high current saturation and perfect stability under low voltage electron bombardment. A novel yellow-green emitting phosphor Na 2 HfSiO 5 :Eu2+ is successfully synthesized through solid-state reaction for the first time. Under the 369 nm excitation, the Na 2 HfSiO 5 :Eu2+ phosphors exhibit a broad yellow emission peaking at 551 nm with FWHM about 100 nm. The Na 2 HfSiO 5 :Eu2+ phosphors exhibit the asymmetric emission peaks owing to the Eu2+ partial occupation of four different Na+ sites with different environment. The energy transfer between Eu2+ ions appears by dipole–dipole interaction. A WLED lamp with high Ra (90) and low CCT (3875 K) was obtained by combing Na 2 HfSiO 5 :Eu2+ with BaMgAl 10 O 17 :Eu2+ (BAM), CaAlSiN 3 :Eu2+ and n-UV chip (λ max = 380 nm). Under the low voltage and current conditions, the phosphor exhibits perfect stability and excellent anti degradation performance. All these results suggest that Na 2 HfSiO 5 :Eu2+ phosphor would be a potential candidate for n-UV LED and FED applications. [ABSTRACT FROM AUTHOR]

A novel yellow emitting phosphor Na 4 Hf 2 Si 3 O 12: Eu2+ (NHSO:Eu2+) has been successfully synthesized through solid-state reaction for the first time. The crystal structure, morphology, and band structure were researched at length. The average diameter of NHSO is 3.06 μm. Under 365 nm excitation, the NHSO:Eu2+ phosphors exhibit a broad yellow emission peaking at 545 nm with FWHM about 126 nm. NHSO:Eu2+ phosphors exhibit an asymmetric emission peak owing to Eu2+ occupying two types of Na+(Na 1 and Na 2) with different environment. The energy transfer between Eu2+ belongs to dipole-dipole interaction. A WLED lamp with high Ra (87.5) and low CCT (3953 K) was obtained by combing NHSO:Eu2+ with BAM, CaAlSiN 3: Eu2+ and n-UV chip (λ max = 380 nm). Under low voltage and current condition, the phosphors also exhibit perfect stability with high current saturation. All these results suggest that NHSO:Eu2+ phosphor would be a potential candidate for n-UV LED and FED applications. • A novel yellow-emitting phosphor Na 4 Hf 2 Si 3 O 12 :Eu2+ was synthesized for the first time. • A WLED lamp was fabricated with higher Ra (87.5) and lower CCT (3953 K) • The phosphor shows characteristic thermal stability, which improves new ideas for the development of temperature sensors. • The phosphor also exhibits high current saturation and perfect stability under low voltage electron bombardment. [ABSTRACT FROM AUTHOR]

• A novel green phosphor Ca 2 YZr 2−x Hf x Al 3 O 12 : Ce3+ was investigated for the first time. • Substitution of Hf4+ could improve structural symmetry and reduced vibration energy. • Substitution of Hf4+ could improve the efficiency and thermal quenching property. • Special spectral variations are related to the different dynamic energy migration degree. • A WLED lamp was fabricated with the good performance of Ra = 83 and CCT = 4117. A series of Ca 2 YZr 2−x Hf x Al 3 O 12 :Ce3+ phosphors were synthesized via the high temperature solid state reaction. Crystal structure is analyzed using the Rietveld method based on the XRD pattern and the infrared absorption spectrum. All the samples are the garnet structures with the Ia3d space group. With the increase of the Hf4+ concentration, all the polyhedral structures become more symmetrical and compact. The structural variation causes the high-Hf4+ concentration compounds with a stronger rigidity and stability. The samples own a strong absorption at the near-UV regions, resulting in a good adaptation with the near-UV chips. Increasing the Hf4+ concentration, the low Ce3+ concentration doped samples exhibit similar emission spectra, however, the high Ce3+ concentration doped samples show an obvious blue shift. Based on the mechanism analysis from theoretical model, the excitation and emission spectra, decay data and the diffuse reflectance spectra, the emission position shift variation and different concentration quenching points could mainly be related with the different degree dynamic energy migration process. The rigid structure with a high symmetry for the high Hf4+ concentration samples could inhibit the energy migration between the Ce3+ ions. As the most important property parameters, the quantum efficiency and thermal quenching property both have obvious improvement when increasing the Hf4+ concentration. For Ca 2 YHf 2 Al 3 O 12 : 0.09Ce3+ samples, the quantum efficiency is 68.5%, and the intensity remains around 76.6% of the room temperature at 150 °C. In particular, our research highlights the significance of dynamical character and energy migration process on the photoluminescence property and provides the referential value for understanding the photoluminescence properties. The excellent properties show that the Ca 2 YHf 2 Al 3 O 12 : Ce3+ have potential as the green phosphors for application in near-UV excitation LEDs. [ABSTRACT FROM AUTHOR]

The site occupation engineering of activators in the phosphor directly affects its luminescence properties; thus, revealing the relationship between the site occupation and the activator luminescence is of great significance. In this work, a high efficiency green phosphor Sr 8 CaLu(PO 4) 7 : Eu2+ (SCLP: Eu2+) was successfully constructed based on the model of whitlockite β -Ca 3 (PO 4) 2 host, and its phase structure, morphology features and optical properties were systemically investigated. The as-prepared SCLP: Eu2+ phosphor had a monoclinic symmetry and a broad green emission from 420 to 730 nm with a quantum yield as high as 77%. The SCLP host offered five types of Sr2+ ions sites for Eu2+ ions occupation; and the PL spectra were divided into three sub-peaks locating at 501 (19960.08 cm−1), 527 (18975.33 cm−1) and 566 nm (17667.84 cm−1), which were proved to the emission of Eu2+ ions at the nine-coordinated Sr(1, 3, 5)O 9 , eight-coordinated Sr(2)O 8 and special vacant Sr(4)O 6 sites, respectively. The thermal stability was improved through the package of SiO 2 , and the activation energy was enhanced from 0.1098 to 0.1457 eV. Eventually, the SCLP: x Eu2+ phosphors were applied in white light-emitting diode, showing high color rendering index (Ra = 94.4 and R9 = 81.7) and moderate correlated color temperature (CCT = 4902 K). This work could help to understand the mechanism behind the site-controlled activator emission and offer some meaningful ideas to design a new whitlockite phosphor with desirable spectral emission for application in high quality lighting source. [ABSTRACT FROM AUTHOR]

Title phosphors with different doping levels are prepared by sintering appropriate mixtures of Si, SiO2, Al(OH)3, Eu2O3, Tb4O7, and Sm2O3 under a 20% H2/N2 atmosphere (BN crucible, 1. [ABSTRACT FROM AUTHOR]

A series of Sr-replaced solid solution Ca 10-x Sr x (PO 4 ) 6 F 2 :Eu 2+ (x = 4, 6, 8) phosphors with apatite structure were engineered and synthesized successfully via the solid-state reaction. The crystal structure, bandgap and photoluminescence properties of the Ca 10-x Sr x (PO 4 ) 6 F 2 :Eu 2+ (x = 4, 6, 8) phosphors were investigated in detail. With the increase of Sr concentration, the bandgap gets narrower and the volume of crystal becomes larger. The existence of oxygen-vacancy-related defect levels in the bandgap and the bandgap reduction caused by these levels were verified by DFT calculated and experiment results. The emission spectra of samples show blue shift from 459 nm to 447 nm. Simultaneously, all of the samples have broad absorption ranging from 240 nm to 450 nm and the crests of these spectra show little blue shift from 343 nm to 337 nm. The thermal stabilities of these samples show obvious improvement (55.01%–68.24% at 150 °C) with the increase of Sr concentration, which indicates that the solid solution design can serve as an effective way to improve the thermal stability of apatite phosphors. In addition, a white LED device has been manufactured by connecting a 380 nm UV chip with a blend of Ca 4 Sr 6 (PO 4 ) 6 F 2 :Eu 2+ , (Sr,Ba)SiO 4 : Eu 2+ and CaAlSiN 3 : Eu 2+ . The LED device shows warm white light with low color temperature (3728 K) and high color rendering index (90.21). Our results provide a practical basis to engineer and develop Eu 2+ -doped novel phosphors. [ABSTRACT FROM AUTHOR]

As the widespread application of white light-emitting diodes (WLEDs) in lighting field and liquid crystal display (LCD) backlight, the development of phosphors toward multifunctional applications is considered to be an inevitable tendency. In this work, multi-color light emissions have been realized in Eu2+ and Mn2+-activated magnetoplumbite-type GdMgAl 11 O 19 (GMAO) along with adjustable photoluminescence properties. Significantly, a promising narrow-band green light emission can be achieved by Mn2+-activated GMAO with the full width at half maximum (FWHM) of 27 nm, and such narrow emission band makes the as-prepared WLED device reach 121 % of National Television Standards Committee (NTSC), which can act as an ideal LCD backlight. On the other hand, the broad cyan light can be achieved in Eu2+-activated GMAO. Moreover, multi-color light emissions have been realized in Eu2+ and Mn2+ co-doped GMAO, and the energy transfer from Eu2+ to Mn2+ ions was established. Benefitting from the broad band cyan light emission of Eu2+ ion, a promising WLED device with high color rendering index (CRI) of 90 has been fabricated by using Eu2+ and Mn2+ co-doped sample. The result indicates the multifunctional applications of the GMAO modulated by Eu2+ and Mn2+ activators. A novel multi-color light emissions phosphor of GdMgAl 11 O 19 : Eu2+, Mn2+ with multifunctional applications has been successfully synthesized. [Display omitted] • Multi-color light emissions have achieved in Eu2+ and Mn2+-activated GdMgAl 11 O 19. • GdMgAl 11 O 19 : Mn2+ emits a narrow-band green light with FWHM of 27 nm. • The color gamut of as-prepared WLED device reach 121 % of National Television Standards Committee. • GdMgAl 11 O 19 : Mn2+ performs good thermal stability. [ABSTRACT FROM AUTHOR]

Developing efficient and stable blue-emitting phosphors has always been crucial for advancing full-spectrum WLED technology. In this study, the germanates K 2 MGeO 5 (M = Zr, Hf) were chosen as the host to develop novel NUV-excited blue-emitting phosphors. The crystal structure, electronic structure, and luminescence properties of K 2 MGeO 5 :Bi3+ were comprehensively investigated using X-ray powder diffraction, Rietveld refinement, photoluminescent spectra analysis, and density functional theory calculations. By integrating experimental data with semi-empirical formula calculations, the excitation and emission sources were elucidated. Furthermore, the influence of Bi3+'s local coordination environment on its luminescence performance and the concentration quenching mechanism in K 2 MGeO 5 :Bi3+ were thoroughly examined. A full-spectrum WLED was fabricated by synergistically combining K 2 ZrGeO 5 :Bi3+, commercially available green and red phosphors with a 365 nm LED chip. It is anticipated that this study could provide insights for the advancement of blue phosphors excited by near-ultraviolet light. • K 2 MGeO 5 :Bi3+ phosphors demonstrate excitation in the near-ultraviolet range and emits blue light. • A combined experimental and theoretical approach was utilized to elucidate the origin of excitation and emission. • A full-spectrum WLED was successfully achieved by utilizing K 2 ZrGeO 5 :Bi3+ as the blue component. [ABSTRACT FROM AUTHOR]

Bismuth ions, as excellent non-rare-earth activators for luminescent materials, possess characteristic excitation in the near ultraviolet (n-UV) region rather than in the visible region and could avoid reabsorption as compared to traditional rare-earth (e.g., Eu2+, Ce3+) phosphors. In this work, a series of apatite-type NaGd 9 (SiO 4) 6 O 2 : xBi3+ (NGSO) phosphors with a hexagonal crystal system were synthesized through high-temperature solid-solid reactions. They showed intense n-UV absorption and cyan emission of Bi3+ ions. The optimal Bi3+ doping concentration was 0.02. Further, there were two types of Bi3+ ions that provided seven- and nine-coordination in NGSO: xBi3+ phosphors, resulting in two luminescence centers at 462 and 558 nm, respectively. Bi3+ (Ⅰ) ions were dominant for the emission at 558 nm excited at a wavelength of 340 nm, and Bi3+ (Ⅱ) ions governed the luminescence at 462 nm excitation at 370 nm; energy transfer occurred from Bi3+ (Ⅰ) to Bi3+ (Ⅱ) ions. Finally, good thermal stability with activation energy (E a) of 0.296 eV was demonstrated. These findings exhibit the potential application of NGSO: 0.02Bi3+ phosphors as cyan phosphors in n-UV white light-emitting diodes. [ABSTRACT FROM AUTHOR]

Rare earth activated lithium-containing alkaline earth silicates is an intensely studied topic in the fields of luminescent materials. In this study, a cerium-activated lithium-silicate blue phosphor, Li 2 Ca 2 Si 2 O 7 :Ce3+, was explored using structural computational simulations and systematic experiments. The Li 2 Ca 2 Si 2 O 7 :Ce3+ phosphor can be efficiently excited by near-ultraviolet and cathode ray light sources. According to the spectroscopic redshift theory, time-resolved photoluminescence (TRPL) and cathodoluminescence (CL) spectra, it is determined that the broad emission of Li 2 Ca 2 Si 2 O 7 :Ce3+ comes from two different luminescent centers. In addition, Li 2 Ca 2 Si 2 O 7 :Ce3+ exhibits strong blue emission at ~415 nm with high quantum yield and stable emission under high temperature and continuous electron beam bombardment. Therefore, this study provides a new insight into developing new high-efficiency and high-purity trichromatic phosphors. [ABSTRACT FROM AUTHOR]

Lithium-containing silicate compounds have attracted so much attention in recent years for applications in energy storage and illumination source due to their rigid structure and good electrical conductivity. In this study, a Eu3+ doped lithium-containing silicate red phosphor, Li 2 Ca 4 Si 4 O 13 :Eu3+, was explored by using structural computational simulations and systematic experiments for multifunctional applications. As a result, due to the quite non-central symmetry of the Ca2+ sites (C 1 symmetry), the strong 4f-4f excitations in near ultraviolet region were observed. Under near ultraviolet and cathode ray light excitation, Li 2 Ca 4 Si 4 O 13 :Eu3+ phosphor has an efficient red emission with good thermal stability and ageing resistance. Furthermore, Li 2 Ca 4 Si 4 O 13 :Eu3+ phosphor exhibits a concentration-sensitive behavior induced by the change of site symmetry. The results show that it is feasible to develop near-ultraviolet and cathode ray light excited red phosphors in lithium-containing silicate compounds. [ABSTRACT FROM AUTHOR]

The white emission phosphor Ca 3 Sc 2 Si 3 O 12 :Dy 3+ was synthesized by the solid-state reaction. Phase analysis and characteristic luminescence properties are investigated by X-ray diffraction and photoluminescence spectra measurement. Ca 3 Sc 2 Si 3 O 12 :Dy 3+ phosphor shows strong absorption in 350–410 nm region and exhibits white emission with CIE chromaticity coordinates of (0.3425, 0.3343). Its emission intensity at 250 °C remained 74% of that measured at room temperature. Moreover, the activation energy is also calculated through the Arrhenius equation. The result shows that the thermostability of Ca 3 Sc 2 Si 3 O 12 :Dy 3+ is superior than that of commercial phosphor Ca 3 Sc 2 Si 3 O 12 :Ce 3+ . The outstanding luminescent properties indicate that Ca 3 Sc 2 Si 3 O 12 :Dy 3+ could be a potential white light emission phosphor. [ABSTRACT FROM AUTHOR]

[Display omitted] • The large-scale redshift of emission spectrum was realized in R 2- y K y CPOF: Eu2+. • The color-adjustable-emission mechanism in the R 2- y K y CPOF: Eu2+ was illustrated. • Full visible spectrum lighting was realized by R 2- y K y CPOF: Eu2+. Tuning the luminescent properties of phosphors by crystal-site engineering is a good and efficient strategy for developing high-quality white light-emitting diodes (WLEDs). However, it is still challenging to modulate the cyan to red spectral emission in a single matrix and activator phosphor to obtain multicolor output and achieve full-visible-spectrum lighting. Herein, the strategy to manipulate site-selective occupation of Eu2+ activators by substituting the cation Rb+ with K+ is reported to obtain a versatile color output. The large-scale redshift regulation of emission spectrum from cyan to red was achieved in fluor-phosphate Rb 2- y K y CaPO 4 F: 0.0085Eu2+ (R 2- y K y CPOF: 0.0085Eu2+) (0 ≤ y ≤ 1.8) phosphors, which is designed by using Rb 2 CaPO 4 F: 0.0085Eu2+ (RCPOF: 0.0085Eu2+) cyan-emitting phosphor. The redistribution of Eu2+ ions in Rb1, Rb2, and Ca sites is achieved by introducing the cation K+ to substitute Rb+, and R 2- y K y CPOF: 0.0085Eu2+ (0 ≤ y ≤ 1.8) is kept in the pure phase. Furthermore, the mixed phosphors of RCPOF: 0.0085Eu2+, RKCPOF: 0.0085Eu2+, and R 0.2 K 1.8 CPOF: 0.0085Eu2+ show excellent optical performance and good thermal stability. Full-visible spectrum lighting is successfully achieved with the combination of a 395 nm NUV chip and the blend of phosphor-converted WLEDs. The K+ substitution reported in this paper can support a project for warm WLEDs by manipulating the distribution of Eu2+ activator among different cation sites. [ABSTRACT FROM AUTHOR]

[Display omitted] • The SCXP host with multiple cation sites was successfully designed. • Their structural evolution and optical properties were systemically studied. • The relation between site occupation and luminescence was revealed. • The neighboring-cation-size could control the distribution of activator. • A high color rendering WLED was fabricated via these phosphors. The photoluminescence behavior in a multiple cation lattice host for obtaining desired spectral emission is an important scientific question to develop next-generation high quality lighting sources. However, how to manipulate the distribution of rare-earth activators over various cation sites is still a technical challenge. Herein, for the first time, trivalent ions Al3+ and Ga3+ were introduced to β -Ca 3 (PO 4) 2 -kind host for preparing the new isostructural Sr 8 CaAl(PO 4) 7 (SCAP) and Sr 8 CaGa(PO 4) 7 (SCGP) hosts and controlling the incorporation of activators Eu2+ in the M(4) sites. Their structural evolution, morphology, diffuse reflection spectrum, electron structure and luminescent properties were systemically investigated. The emission of Eu2+ ions distributed over the nine-coordinated Sr(1, 3, 5)O 9 , eight-coordinated Sr(2)O 8 and special coordinated Sr(4)O 6 sites was located in the green (507 nm), yellow (555 nm) and red (610 nm) regions, respectively. Further, a smaller cation radius (Al3+) allowed higher number of activators (Eu2+) to be accessed to the neighboring M(4) lattice site for obtaining more intense red emission, which would enable these kinds of phosphors-converted white light emitting diodes to show quite high color-rendering indexes (Ra = 94.4). This neighboring-cation-size strategy mentioned here can become a novel approach to PL spectral modulation through controlling the distribution of Eu2+ activators over various lattice sites for excellent solid state lighting. [ABSTRACT FROM AUTHOR]