An efficient rare-earth free deep red-emitting GdGeSbO6:Mn4+ phosphor for white light-emitting diodes

Red phosphors play an important role in improving the light quality and color rendering index of white light-emitting diodes (WLEDs) for lighting. In this paper, we report the transition ion Mn4+-activated deep red phosphor GdGeSbO6:x%Mn4+ and analyze its crystal structure, composition and luminescence behavior in detail. Its optimal doping concentration of Mn4+ is 0.3%. Under ultraviolet (UV) excitation, GdGeSbO6:0.3%Mn4+ produces a narrow emission peak centred at 682 nm in the range of 650-800 nm with a full width at half maximum (FWHM) of 25 nm, which is attributed to the spin-prohibited 2Eg → 4A2g transition of Mn4+ ions. Notably, the optimal phosphor GdGeSbO6:0.3%Mn4+ has a high internal quantum efficiency (IQE ≈ 65%) and excellent thermal stability performance (I423 K/I303 K ≈ 62%). The synthesis of high-performance warm WLEDs and full-spectrum WLEDs was achieved by combining and coating GdGeSbO6:0.3%Mn4+ phosphors with commercial phosphors on the surface of a 365 nm UV chip.

Deep red emission from rare-earth-free calcium aluminozincate phosphor with the substitution of Cr3+ ion

Chromium-doped calcium aluminozincate phosphor with a distinct amount of chromium was prepared via the sol-gel technique. The phase analysis and morphological study along with optical properties were conducted on the prepared material. The room temperature luminescent traits of the sample were studied in detail under 540 nm excitation wavelength. The deep red emission was confirmed from the CIE coordinates calculated using emission data. The decay curves were recorded to calculate the lifetime values for the aforementioned powder samples. The temperature-dependent luminescent characteristics were also investigated to identify the activation energy and thermal stability. The quantum yield was also calculated using luminescence spectra and found to be relatively good for the present phosphor. All of the investigated studies specified above signify that the synthesized phosphor is well suited as a red emitter in lighting and display devices.

Double Perovskite Mn4+-Doped La2CaSnO6/La2MgSnO6 Phosphor for Near-Ultraviolet Light Excited W-LEDs and Plant Growth

Non-rare earth doped oxide phosphors with far-red emission have become one of the hot spots of current research due to their low price and excellent physicochemical stability as the red component in white light-emitting diodes (W-LEDs) and plant growth. Herein, we report novel Mn⁴⁺-doped La₂CaSnO₆ and La₂MgSnO₆ phosphors by high-temperature solid-phase synthesis and analyzed their crystal structures by XRD and Rietveld refinement. Their excitation spectra consist of two distinct excitation bands with the dominant excitation range from 250 to 450 nm, indicating that they possess strong absorption of near-ultraviolet light. Their emission is located around 693 and 708 nm, respectively, and can be absorbed by the photosensitive pigments Pr and Pfr, proving their great potential for plant growth. Finally, the prepared samples were coated with 365 nm UV chips to fabricate far-red LEDs and W-LEDs with low correlation color temperature (CCT = 4958 K/5275 K) and high color rendering index (R_a = 96.4/96.6). Our results indicate that La₂CaSnO₆:Mn⁴⁺ and La₂MgSnO₆:Mn⁴⁺ red phosphors could be used as candidate materials for W-LED lighting and plant growth.

Luminescence of Mn4+ in a Zero-Dimensional Organic-Inorganic Hybrid Phosphor [N(CH3)4]2ZrF6 for Dual-Mode Temperature Sensing

Searching for new low-dimensional organic-inorganic hybrid phosphors is of great significance due to their unique optical properties and wide applications in the optoelectronic field. In this work, we report a Mn⁴⁺ doped zero-dimensional organic-inorganic hybrid phosphor [N(CH₃)₄]₂ZrF₆, which was synthesized by a wet chemical method. The crystal structure, thermal stability, and optical properties were systemically investigated by means of XRD, SEM, TG-DTA, FTIR, DRS, emission spectra, excitation spectra, as well as decay curves. Narrow red emission with high color purity can be observed from [N(CH₃)₄]₂ZrF₆:Mn⁴⁺ phosphor, which maintains effective emission intensity even at room temperature, indicating its potential practical application in WLEDs. In the temperature range of 13-295 K, anti-Stokes and Stokes sidebands of Mn⁴⁺ ions exhibit different temperature responses. By applying the emission intensity ratio of anti-Stokes vs. Stokes sidebands as temperature readout, an optical thermometer with a maximum absolute sensitivity of 2.13% K^-1 and relative sensitivity of 2.47% K^-1 can be obtained. Meanwhile, the lifetime Mn⁴⁺ ions can also be used for temperature sensing with a maximum relative sensitivity of 0.41% K^-1, demonstrating its potential application in optical thermometry.

Construction of novel luminescent thermometers based on dual-emission centers of rare-earth and bismuth ions

Optical thermometry based on fluorescence intensity ratio (FIR) technology has several advantages for industrial and medical applications such as remote signaling, non-invasiveness, and excellent spatial resolution. Here, an approach to the construction of luminescent thermometers is proposed based on high-temperature solid-state reactions through doping of rare earth (RE) elements (e.g., samarium (Sm³⁺) or europium (Eu³⁺)) into Ca₂Y_0.97Bi_0.03SbO₆ (CYBS) phosphors. The tuning of the CYBS:Eu³⁺ and CYBS:Sm³⁺ ratios in the phosphors provided a wide range of color changes from purplish blue to red and from purplish blue to pink, respectively. The superiority of optical thermometer is validated by higher values of absolute sensitivity (S_a) and relative sensitivity (S_r). As such, both phosphors exhibit excellent temperature sensing performance with S_a/S_r values (at 483 K) of 4.945 × 10^-2/0.968 × 10^-2 K^-1 (CYBS:0.05Eu³⁺) and 2.964 × 10^-2/0.864 × 10^-2 K^-1 (CYBS:0.05 Sm³⁺). Thus, RE-doped CYBS materials with color tuning properties and superior temperature sensing performance are recommended for the construction of novel luminescent optical thermometers.

A study of negative-thermal-quenching (Ba/Ca)AlSi5O2N7:Eu2+ phosphors

Phosphor is an important part of the new generation of light-emitting diodes (LEDs), which requires high luminous intensity and high-temperature resistance. In this study, a series of excellent (Ba_1-x-yCa_x)AlSi₅O₂N₇:yEu²⁺ phosphors was developed, which were synthesized by a high-temperature solid-state reaction in a reducing atmosphere. In addition, the crystallinity and luminescence intensity of the samples could be enhanced by some amount of Ca²⁺ substitution. The luminescence intensity was the highest when the Eu²⁺ concentration reached 0.06. Furthermore, the thermal stability of the luminescence was studied in detail. The results were satisfactory, showing that the luminescence intensity of the (Ba_1-xCa_x)AlSi₅O₂N₇:Eu²⁺ phosphors exhibited unique negative-thermal-quenching characteristics both at high (273-473 K) and low (4-273 K) temperatures. And the phosphor combined with UV LED chip and red phosphor Sr₂Si₅N₈:Eu²⁺ can achieve a CRI of 90.4 in white LED application which indicated the (Ba_1-xCa_x)AlSi₅O₂N₇:Eu²⁺ phosphor has potential in LED applications.

Local Structure Modulation-Induced Highly Efficient Red-Emitting Ba2Gd1-xYxNbO6:Mn4+ Phosphors for Warm WLEDs

Modulating the crystal field environment around the emitting ions is an effective strategy to improve the luminescence performance of the practical effective phosphor materials. Here, smaller Y³⁺ ions are introduced into substituting the Gd³⁺ sites in Ba₂GdNbO₆:Mn⁴⁺ phosphor to modify the optical properties, including the enhanced luminescence intensity, redshift, and longer lifetime of the Mn⁴⁺ ions. The substitution of smaller Y³⁺ ions leads to lattice contraction and then strengthens pressure on the local structure, enhances lattice rigidity, and suppresses nonradiative transition. Moreover, the prototype phosphor-converted light-emitting diode (LED) demonstrates a continuous change photoelectric performance with a correlated color temperature of 4883-7876 K and a color rendering index of 64.1-83.2, suggesting that it can be one of the most prospective fluorescent materials applied as a warm red component for white LEDss. Thus, the smaller ion partial substitution can provide a concise approach to modulate the crystal field environment around the emitting ions for excellent luminescence properties of phosphors toward the modern artificial light.

High performance red/deep-red emitting phosphors for white LEDs

NaSrGd(MoO₄)₃:Eu³⁺ red phosphor exhibits higher quantum efficiency (82%) and the fabricated white LED showed 74% CRI and 6823 K CCT.

Luminescence and Energy-Transfer Properties in Bi3+/Mn4+-Codoped Ba2GdNbO6 Double-Perovskite Phosphors for White-Light-Emitting Diodes

Currently, the study of Mn⁴⁺-doped oxide red phosphor is a hot research topic to solve the lack of red component in phosphor-converted white-light-emitting diodes (pc-WLEDs). In this Article, we designed Gd³⁺/Nb⁵⁺ cation substitution by Bi³⁺/Mn⁴⁺ in Ba₂GdNbO₆ with double-perovskite structure based on the radius and coordination of the cations through high-temperature solid-state reaction. The phase purity and microstructure of double-perovskite Ba₂GdNbO₆:Bi³⁺,Mn⁴⁺ phosphors were characterized by X-ray diffraction and scanning electron microscopy examination. The crystal structures were also determined by the Rietveld refinement, and the photoluminescence (PL) properties were systematically studied. Bi³⁺ and Mn⁴⁺ ions can be effectively doped in the Ba₂GdNbO₆ matrix with an optical band gap of 3.94 eV. Upon 315 nm UV excitation, the Ba₂GdNbO₆:Bi³⁺,Mn⁴⁺ phosphor shows two emission bands at 464 nm from Bi³⁺ and 689 nm from Mn⁴⁺, respectively. By the design of Bi³⁺ → Mn⁴⁺ energy transfer, systematic luminescence tuning from blue to red could be achieved because of spectral overlap between the emission spectrum of Bi³⁺ and the excitation spectrum of Mn⁴⁺. The corresponding mechanism of the Bi³⁺ → Mn⁴⁺ energy-transfer process was investigated in detail by the fluorescence decays and PL spectra. The red emission intensity of Mn⁴⁺ has been greatly improved by Bi³⁺ → Mn⁴⁺ energy transfer. Moreover, the phonon vibration and zero phonon line of Mn⁴⁺ were studied through temperature-dependent PL. Finally, a WLED was fabricated using a 460 nm blue chip with a yellow YAG:Ce³⁺ phosphor and a red Ba₂GdNbO₆:0.01Bi³⁺,0.01Mn⁴⁺ phosphor, which has a low correlated color temperature (3550 K) and a high color rendering index (89.6). The above results imply that the improved red emission phosphors have a potential application in warm pc-WLED lighting.

Synthesis, Crystal Structure, and Photoluminescence Characteristics of High-Efficiency Deep-Red Emitting Ba2GdTaO6:Mn4+ Phosphors

In this article, a series of novel Mn4+-doped Ba2GdTaO6 (BGT) red-emitting phosphors were successfully synthesized via a high-temperature solid-state method. The crystal structure, morphology, and luminescent performance of the samples were investigated in detail with X-ray diffraction, field emission scanning electron microscopy, photoluminescence (PL) spectra, decay curves, and internal quantum efficiency (IQE). Excited at 358 nm, these samples showed an intense deep-red emission band peaking at 688 nm in the wavelength region of 620-800 nm. The excitation spectra of these samples monitored at 688 nm exhibited two broad excitation bands from 250 to 600 nm with peaks at 358 and 469 nm. The systematic investigation of the concentration-dependent PL properties of BGT:Mn4+ phosphors revealed that the deep-red emission intensity reached the maximum when the Mn4+ doping concentration was 0.6 mol %. The critical distance (R c) between Mn4+ ions for concentration quenching was 36.57 Å, and the major mechanism of energy transfer among Mn4+ activators in BGT:Mn4+ was dipole-dipole interaction. The decay lifetimes decreased from 0.285 to 0.248 ms with the increasing Mn4+ doping concentration from 0.2 to 1.2 mol %. The Commission Internationale de l'Éclairage coordinates of the optimal BGT:0.6%Mn4+ sample were (0.7294, 0.2706). The values of the IQE for all BGT:Mn4+ samples were measured, and the highest value could reach up to 62%. The above results revealed that these high-efficiency BGT:Mn4+ deep-red-emitting phosphors had promising potential for application in indoor plant growth lighting.

Mn4+-activated Li3Mg2SbO6 as an ultrabright fluoride-free red-emitting phosphor for warm white light-emitting diodes

In this paper, we report on highly efficient Mn⁴⁺-activated double perovskite Li₃Mg₂SbO₆ (LMS) red-emitting phosphors. These LMS:Mn⁴⁺ phosphors can be efficiently excited over a broad wavelength band from 235 nm to 600 nm peaking at 344 nm and 469 nm, and exhibited an intense red emission band with a range from 600 nm to 800 nm centered around 651 nm. The optimal Mn⁴⁺ doping concentration of LMS:Mn⁴⁺ was 0.6 mol% and its internal quantum efficiency can reach as high as 83%. Besides, the thermal quenching effect on the optical property was also analyzed. Finally, a warm white light-emitting diode (WLED) lamp was fabricated by using a 454 nm InGaN blue LED chip combined with a blend of YAG:Ce³⁺ yellow phosphors and the as-prepared LMS:0.6% Mn⁴⁺ red phosphors, which showed bright white light with CIE chromaticity coordinates (0.4093, 0.3725), correlated color temperature (CCT = 3254 K), color rendering index (CRI = 81) and luminous efficacy (LE = 87 lm/W).

Mn⁴⁺-activated Li₃Mg₂SbO₆ red-emitting phosphor with internal quantum efficiency as high as 83% was developed for blue-pumped warm-white light-emitting diodes.

Enhanced narrow-band green-emission and thermal stability via the introduction of Mg2+ in ZnB2O4:Mn2+ phosphor

The introduction of Mg²⁺ in ZnB₂O₄:Mn²⁺ may reduce the impurity phase, and increase the emission intensity and thermal stability by 100% and 9%, respectively. The mechanism is considered to be the ion-size compensation effect of Mg²⁺ to Mn²⁺.

Novel polygonal structure Mn4+ activated In3+-based Elpasolite-type hexafluorides red phosphor for warm white light-emitting diodes (WLEDs)

Red phosphors (NH₄)₂NaInF₆:Mn⁴⁺ with controllable morphology were synthesized via different synthetic methods, which can be fabricated for warm white LEDs.

A highly luminescent Mn4+ activated LaAlO3 far-red-emitting phosphor for plant growth LEDs: charge compensation induced Mn4+ incorporation

A highly luminescent far-red-emitting phosphor LaAlO₃:Mn⁴⁺,Mg²⁺ with a quantum yield of 78.6% synthesized with the assistance of MgF₂.

Thermally stable La2LiSbO6:Mn4+,Mg2+far-red emitting phosphors with over 90% internal quantum efficiency for plant growth LEDs

In this paper, we reported on the high-efficiency and thermally-stable La₂LiSbO₆:Mn⁴⁺,Mg²⁺ (LLS:Mn⁴⁺,Mg²⁺) far-red emitting phosphors. Under 338 nm excitation, the composition-optimized LLS:0.3%Mn⁴⁺,1.6%Mg²⁺ phosphors which were made up of [SbO₆], [LiO₆], and [LaO₈] polyhedrons, showed intense far-red emissions peaking at 712 nm (²E_g → ⁴A_2g transition) with internal quantum efficiency as high as 92%. The LLS:0.3%Mn⁴⁺,1.6%Mg²⁺ phosphors also exhibited high thermal stability, and the emission intensity at 423 K only reduced by 42% compared with its initial value at 303 K. The far-red light-emitting device has also been made by using the LLS:0.3%Mn⁴⁺,1.6%Mg²⁺ phosphors and a 365 nm emitting InGaN chip, which can emit far-red light that is visible to the naked eye. Importantly, the emission spectrum of the LLS:0.3%Mn⁴⁺,1.6%Mg²⁺ phosphors can match well with the absorption spectrum of phytochrome P_FR, indicating the potential of these phosphors to be used in plant growth light-emitting diodes.

Double perovskite La₂LiSbO₆:Mn⁴⁺,Mg²⁺ far-red emitting phosphors with internal quantum efficiency as high as 92% and good thermal stability were developed for plant growth LEDs.

Novel SrLaAlO4:Mn4+deep-red emitting phosphors with excellent responsiveness to phytochrome PFRfor plant cultivation LEDs: synthesis, photoluminescence properties, and thermal stability

Herein, novel rare-earth-free Mn⁴⁺-doped SrLaAlO₄ deep-red emitting phosphors were successfully synthesized via a traditional solid-state reaction method. The crystal structure and phase purity of the as-prepared samples were confirmed by XRD Rietveld refinement. Photoluminescence properties of SrLaAlO₄:Mn⁴⁺ phosphors were examined in detail using photoluminescence spectra, decay lifetimes, temperature-dependent emission spectra and internal quantum efficiency measurements. The excitation spectrum obtained by monitoring at 730 nm contained two excitation bands centered at 364 and 520 nm within the range of 200–550 nm due to the Mn⁴⁺–O²⁻ charge-transfer band and the ⁴A_2g → ⁴T_1g, ⁴T_2g transitions of the Mn⁴⁺ ions. Under the 364 nm excitation, the SrLaAlO₄:Mn⁴⁺ phosphors exhibited an intense deep-red emission band in 610–790 nm wavelength range peaking at 730 nm, which was assigned to the ²E_g → ⁴A_2g transition of Mn⁴⁺ ions. The deep red emission showed excellent responsiveness to phytochrome P_FR, revealing that the SrLaAlO₄:0.4% Mn⁴⁺ phosphors possessed a possible application in deep-red light-emitting diodes (LEDs) for plant cultivation. The optimal doping concentration of Mn⁴⁺ ions was found to be 0.4 mol%. The critical distance R_c for energy transfer among Mn⁴⁺ ions was determined to be 5.86 Å and the concentration quenching mechanism was confirmed to be the electric dipole–dipole interaction. In addition, the Commission International de I'Eclairage (CIE) colour coordinates of the SrLaAlO₄:0.4% Mn⁴⁺ phosphors (0.734, 0.266) were located in the deep red region and the corresponding internal quantum efficiency was measured to be about 29%. The above results confirmed that the as-prepared SrLaAlO₄:0.4% Mn⁴⁺ deep red emitting phosphors might be a potential candidate for plant cultivation LEDs.

Novel Mn⁴⁺ activated SrLaAlO₄ deep-red emitting phosphors with excellent responsiveness to phytochrome P_FR were developed for plant cultivation LEDs.

Novel far-red-emitting SrGdAlO4:Mn4+ phosphors with excellent responsiveness to phytochrome PFR for plant growth lighting

In this work, we reported on novel far-red-emitting SrGdAlO₄:Mn⁴⁺ (SGA:Mn⁴⁺) phosphors towards application in plant growth lighting. The crystal structure and luminescence properties were investigated on the basis of X-ray diffraction, excitation and emission spectra, luminescence decay curves and temperature-dependent photoluminescence spectra. When excited by 353 nm, the SGA:Mn⁴⁺ phosphors showed a far-red emission band in the 650–800 nm wavelength range with peaks at 709 and 725 nm, which was due to the ²E_g → ⁴A_2g electron transition of Mn⁴⁺ ion. The optimal Mn⁴⁺ doping concentration was about 0.1 mol%. The CIE chromaticity coordinates of the SGA:0.1%Mn⁴⁺ sample were (0.7064, 0.2934). The luminescence decay lifetimes decreased gradually from 1.263 to 0.868 ms with the increasing Mn⁴⁺ concentrations. Notably, the emission band of SGA:0.1%Mn⁴⁺ sample was well-matched with the absorption spectrum of phytochrome P_FR, which indicated the SGA:Mn⁴⁺ were potential far-red-emitting phosphors for plant growth applications.

In this paper, we reported on novel Mn⁴⁺-activated SrGdAlO₄ far-red-emitting phosphors with excellent responsiveness to phytochrome P_FR for potential application in plant growth lighting.

Synthesis and photoluminescence properties of novel far-red-emitting BaLaMgNbO6:Mn4+ phosphors for plant growth LEDs

A series of far-red-emitting BaLaMgNbO₆:Mn⁴⁺ (BLMN:Mn⁴⁺) phosphors were successfully synthesized by a high-temperature solid-state reaction method. Crystal structure and luminescence properties of the obtained samples were systematically investigated. The emission spectra exhibited a strong narrow far-red emission band peaking at 700 nm with a full width at half-maximum (FWHM) of ∼36 nm under 360 nm excitation. The optimal Mn⁴⁺ concentration was about 0.4 mol%. The internal quantum efficiency and CIE chromaticity coordinates of the BLMN:0.4% Mn⁴⁺ phosphor were 52% and (0.7222, 0.2777), respectively. In addition, the luminescence mechanism has been analyzed using a Tanabe–Sugano energy level diagram. Finally, by using a 365 nm near-ultraviolet InGaN chip combined with BLMN:0.4% Mn⁴⁺ phosphors, a far-red LED device was fabricated.

Mn⁴⁺-activated BaLaMgNbO₆ far-red emitting double-perovskite phosphors with internal quantum efficiency up to 52% were developed for potential application in plant growth LEDs.

Preparation, characterization, and luminescence properties of double perovskite SrLaMgSbO6:Mn4+ far-red emitting phosphors for indoor plant growth lighting

Mn⁴⁺-activated SrLaMgSbO₆ far-red emitting phosphors with double perovskite structure were prepared by traditional solid-state reaction. The research on the crystal structure of the SrLaMgSbO₆:0.8%Mn⁴⁺ (SLMS:0.8%Mn⁴⁺) phosphors showed that the as-prepared sample was made up of two polyhedrons, [SbO₆] and [MgO₆]. Under the excitation of 333 nm, the SLMS:0.8%Mn⁴⁺ phosphors exhibited an intense far-red emission in the 625–800 nm wavelength range with CIE chromaticity coordinates of (0.733, 0.268), which could match well with the absorption spectrum of phytochrome P_FR. The optimal concentration of Mn⁴⁺ ions in the SLMS:Mn⁴⁺ phosphors was 0.8 mol%. Importantly, the as-prepared SLMS:0.8%Mn⁴⁺ phosphors had an internal quantum efficiency of 35%. The thermal stability of SLMS:0.8%Mn⁴⁺ phosphors was also investigated, and the activation energy was found to be 0.3 eV. Thus, the Mn⁴⁺-activated SLMS phosphors have great potential to serve as far-red emitting phosphors in indoor plant growth lighting.

Novel far-red emitting double perovskite SrLaMgSbO₆:Mn⁴⁺ phosphors were prepared and their photoluminescence properties were studied for applications in indoor plant growth lighting.

Enhanced luminescence of a Ba2GdSbO6:Mn4+ red phosphor via cation doping for warm white light-emitting diodes

A novel non-rare-earth-doped perovskite Ba₂GdSbO₆:Mn⁴⁺ red-emitting phosphor and the related enhancement mechanisms of charge compensation and ionic substitution are reported.

Novel Mn4+-activated LiLaMgWO6 far-red emitting phosphors: high photoluminescence efficiency, good thermal stability, and potential applications in plant cultivation LEDs

Double perovskite-based LiLaMgWO₆:Mn⁴⁺ (LLMW:Mn⁴⁺) red phosphors were synthesized by traditional solid-state route under high temperature, and they showed bright far-red emission under excitation of 344 nm. The crystal structure, luminescence performance, internal quantum efficiency, fluorescence decay lifetimes, and thermal stability were investigated in detail. All samples exhibited far-red emissions around 713 nm due to the ²E_g → ⁴A_2g transition of Mn⁴⁺ under excitation of near-ultraviolet and blue light, and the optimal doping concentration of Mn⁴⁺ was about 0.7 mol%. The CIE chromaticity coordinates of the LLMW:0.7% Mn⁴⁺ sample were (0.7253, 0.2746), and they were located at the border of the chromaticity diagram, indicating that the phosphors had high color purity. Furthermore, the internal quantum efficiency of LLMW:0.7% Mn⁴⁺ phosphors reached up to 69.1%, which was relatively higher than those of the reported Mn⁴⁺-doped red phosphors. Moreover, the sample displayed good thermal stability; the emission intensity of LLMW:0.7% Mn⁴⁺ phosphors at 423 K was 49% of the initial value at 303 K, while the activation energy was 0.39 eV. Importantly, there was a broad spectral overlap between the emission band of LLMW:Mn⁴⁺ phosphors and the absorption band of phytochrome P_FR under near-ultraviolet light. All of these properties and phenomena illustrate that the LLMW:Mn⁴⁺ phosphors are potential far-red phosphors for applications in plant cultivation LEDs.

Novel Mn⁴⁺-activated LiLaMgWO₆ far-red emitting double-perovskite phosphors with high photoluminescence efficiency and good thermal stability were developed for applications in plant cultivation LEDs.

Far-red-emitting double-perovskite CaLaMgSbO6:Mn4+ phosphors with high photoluminescence efficiency and thermal stability for indoor plant cultivation LEDs

A series of Mn⁴⁺-activated CaLaMgSbO₆ far-red-emitting phosphors were synthesized by a solid-state reaction route and the microstructure and optical characterizations were investigated in detail. Upon excitation at 370 and 469 nm, the samples showed intense far-red emission at about 708 nm originating from the ²E_g → ⁴A_2g transition and the optimal Mn⁴⁺ concentration was 0.7 mol%. The as-prepared phosphors also exhibited excellent internal quantum efficiency (88%) and high thermal stability. The emission intensity at room temperature dropped to 54% when the temperature rose to 423 K and the activation energy was 0.34 eV. The outstanding optical properties and the fact that the emission band of the obtained phosphors had a broad overlap with the absorption band of phytochrome P_FR demonstrated that the CaLaMgSbO₆:Mn⁴⁺ phosphors may be promising potential spectral converters for applying to indoor plant cultivation light-emitting diodes.

Far-red-emitting double-perovskite CaLaMgSbO₆:Mn⁴⁺ phosphors with high quantum efficiency and thermal stability were developed for potential applications in indoor plant cultivation LEDs.