Plant Growth LEDs Research Articles

Photoluminescence investigations on Sm3+/Eu3+ co-doped Sr3NaSbO6 nanorod-shaped red phosphor for W-LEDs and indoor plant growth LEDs

Red phosphors have garnered an important role in white light-emitting diodes (W-LEDs). Herein we report the structural and luminescent properties of red-emitting Sr(3-x-y)NaSbO6: xSm3+/yEu3+ (SNSO: xSm; yEu) phosphors. Under 350 nm excitation, phosphors emit intense red emission peaking around 689 nm owing to the SNSO host emission. Optimized singly doped SNSO: 0.1Sm and SNSO: 0.2Eu phosphors have intense orange-red and red emissions under 405 and 305 nm excitations respectively. For the codoped SNSO: 0.1Sm; yEu phosphors (y = 0.1, 0.15, 0.2, 0.25, and 0.3 mol), the emission peaks of the host, Sm3+, and Eu3+ ions were present. The energy transfer from the host to Sm3+/ Eu3+ ions and from Sm3+ to Eu3+ ions was identified to be via dipole-quadrupole and quadrupole–quadrupole interactions respectively. Effective red tuning along with high color purity and warm CCT values suggest the suitability of prepared nanorod phosphors for W-LEDs and indoor plant growth LEDs.

Enhanced luminescence performance in double perovskite CaSrLaSbO6: Mn4+ red emission phosphors for indoor plant growth via cation doping

Novel CaSrLaSbO6: Mn4+ red-emitting phosphors with double perovskite structure were successfully synthesized by the high-temperature solid-phase method. CaSrLaSbO6:Mn4+ phosphor showed a broad excitation band with different excitation peaks from 250 nm to 600 nm owing to the Mn4+-O2- charge transfer and 4A2g → (4T1g, 2T2g, and 4T2g) transitions of Mn4+ ions and exhibited intense deep-red emission at 678 nm attributed to the 2Eg → 4A2g transition of Mn4+ ions. To further enhance the performance of the phosphor, a cation doping method was adopted in this paper to synthesize CaSrLa1-xLnxSbO6: Mn4+ (Ln = Gd, Y) phosphors. The luminescence intensity of the samples was enhanced after doping with different cations, and the related mechanism was discussed. In addition, the microstructure and crystal field environment were systematically investigated. The luminescence intensity of the CaSrLa0.85Y0.15SbO6: Mn4+ phosphor was about 1.82 times higher than that of CaSrLaSbO6: Mn4+phosphor. The emission spectrum of the sample matched well with the absorption band of plant pigments. Furthermore, the plant growth LEDs and light-conversion film were prepared by using the optimized CaSrLa0.85Y0.15SbO6: Mn4+. The results indicate that the designed phosphors have great potential applications in agricultural cultivation.

Promising deep-red emitting Cr3+-doped SrAl12O19 phosphors for plant growth LEDs.

Recently, deep-red-emitting phosphors that can be excited by ultraviolet (UV) and near-ultraviolet (NUV) light have been extensively investigated for plant growth LED applications. However, due to the harmful effects of these high-energy rays on plants, violet- or blue-excited deep-red-emitting phosphors are considered a more appropriate solution. In this work, SrAl12O19:Cr3+ phosphors were synthesized using a simple solid-state reaction, revealing a strikingly sharp deep-red emission band centered at 694 nm and effective excitation by violet light. The optimal SrAl12O19:1.0%Cr3+ phosphor, annealed at 1500°C, exhibits an extended lifetime of 0.549 ms, an energy activation level of 0.239 eV, a good quantum efficiency (QE) of 36.2%, and superior color purity at 100%. Further, an LED prototype with a precise absorption spectrum for far-red phytochrome (Pfr) has been demonstrated. These results indicate that the synthesized SrAl12O19:1.0%Cr3+ phosphors could be used as a promising deep-red-emitting phosphor for plant growth LED.

Site Substitution Toward Modified Spectral Behaviors in Ce3+‐Activated Sr4La6(SiO4)6Cl2 Cyan‐Emitting Phosphors for Plant Growth and Full‐Spectrum White Light‐Emitting Diode

AbstractSeries of Ce3+‐activated Sr4La6(SiO4)6Cl2 (SLSOC) cyan‐emitting phosphors are designed to satisfy the demands of plant growth and full‐spectrum white‐light diode (white‐LED). Herein, to modify the luminescence behaviors of phosphors, Ce3+ is designed to occupy the different sites in SLSOC host lattices. Excited at 353 nm, the resultant phosphors emit glaring cyan emission originating from Ce3+ with an asymmetric emission band, which is assigned to the two‐site occupation of Ce3+ at Sr2+ or La3+ crystallographic sites. Moreover, the quantum efficiency and thermal quenching performances of synthesized phosphors are also analyzed, which are all dependent on the crystallographic sites taken by Ce3+. Via using the designed phosphors, two cyan‐emitting LEDs are packaged and their emissions are highly overlapped with the absorption spectra of plant pigments, which allow their feasibilities in plant growth. Furthermore, the artificial plant growth experiments are performed to clarify the significant positive influence of the packaged cyan‐emitting LEDs on plant growth. Additionally, via using the prepared cyan‐emitting phosphors to compensate the cyan gap, the full‐spectrum white‐LEDs with high electroluminescence performances are designed. These achievements reveal that the Ce3+‐activated SLSOC phosphors with controllable luminescence properties are promising cyan‐emitting converters for artificial plant growth LED and full‐spectrum white‐LED.

Red-emitting Mn4+-doped Li2MgSn2O6 phosphors for plant growth LED lighting

In this study, a novel red-emitting Mn4+ doped Li2MgSn2O6 (Li2MgSn2O6:Mn4+) phosphors were successfully synthesized using a simple solid-state reaction method. XRD patterns indicated the replacement of Mn4+ ions with Sn4+ ions in the [SnO6] octahedrons site of the Li2MgSn2O6 lattice, and XPS spectra confirmed the Mn4+ oxidation state. Excited at 323 nm and 480 nm, the phosphors exhibited a strong red emission band peaking at 659 nm, attributed to the 2E → 4A2 transition of Mn4+ ions. Notably, the highest PL intensity was found in the Li2MgSn2O6:0.3%Mn4+ sample annealed at 1000 °C. These phosphors, with a particle size of 1.0 μm, possess a long lifetime of 0.176 ms, high activation energy of 0.335 eV, excellent color purity of 99.9%, and good internal and external quantum efficiency of 44.5% and 24.1%, respectively. Furthermore, an LED coated with Li2MgSn2O6:0.3%Mn4+ phosphor on a 365 nm NUV LED chip showed strong emission matching the absorption spectrum of the red phytochrome. Therefore, these results indicated that the synthesized Li2MgSn2O6:Mn4+ phosphors could be used as red-emitting materials for plant growth LED applications.

Designing dual-functional lighting via Eu3+-activated MF2 (M2+ = Ca2+, Sr2+ and Ba2+) red-emitting nanoparticles

Developing high efficient and stable red-emitting phosphors is very important in the areas of white lighting-emitting diode (white-LED) and plant growth. Herein, series of Eu3+-activated MF2 (M2+ ​= ​Ca2+, Sr2+, Ba2+) red-emitting nanoparticles (NPs) were synthesized at room temperature. Excited at 394 ​nm, these resulting NPs can emit dazzling red emissions and their fluorescence intensities are sensitive to both dopant content and host compound. Moreover, it is found that the studied samples have admirable thermal stability, high quantum efficiencies and color purities, which can be regulated via changing host material. To assess the possible application of final products, three different white-LEDs were packaged by using Eu3+-activated MF2 (M2+ ​= ​Ca2+, Sr2+, Ba2+) red-emitting NPs. Clearly, these manufactured white-LEDs can produce glaring warm white with satisfied electroluminescence behaviors, i.e. low correlated color temperature (<5000 ​K) and high color rendering index (>80). Furthermore, via using the designed NPs, three red-emitting LEDs were also fabricated so as to identify their applications in plant growth. Our findings imply that Eu3+-activated MF2 (M2+ ​= ​Ca2+, Sr2+, Ba2+) NPs are well-suited for dual-functional lighting as red-emitting converters in the realms of white-LED and artificial plant growth LED.

Harnessing the brilliance of Cr3+ doped LaAlO3–Al2O3 phosphors with exceptional responsiveness to far-red phytochrome for plant growth LEDs

Perovskite-based materials have recently gained significant attention due to their unique properties. Herein, the deep and far-red-emitting LaAlO3–Al2O3:Cr3+ perovskite-based phosphors with particle sizes of 2–5 μm have been reported for the first time, demonstrating excellent responsiveness to far-red phytochrome. The synthesized phosphors exhibited a sharply defined deep and far-red emission, peaking at 735 nm, and significant absorptions in the violet (∼410 nm) and green (∼565 nm) regions. The distinct lines at 735 nm can be attributed to the robust crystal field effect of surrounding Cr3+ ions, wherein the 3+ oxidation state substitutes smaller-sized Al3+ ions in the [AlO6] octahedral site of the LaAlO3–Al2O3 lattice. The optimized LaAlO3–Al2O3:0.6%Cr3+ phosphor, annealed at 1400 °C, demonstrated exceptional characteristics, including a color purity of 100 %, a prolonged lifetime of 32.26 ms, a high activation energy of 0.501 eV, and an impressive internal quantum efficiency of 68.1 %. Moreover, a prototype of a violet-pumped LaAlO3–Al2O3:0.6%Cr3+ phosphor-coated LED showcased a well-matched emission spectrum with the absorption spectrum of far-red phytochrome, underscoring its significant potential for applications in LED-based plant growth systems.

A new red phosphor with high thermal stability for plant growth LEDs

The use of artificial light in modern agriculture is essential for increasing crop yields and quality, as well as controlling the growth and development pace of plants. A new series of Mg0.388+xAl2.408-2xMnxO4 (MAO: xMn4+) phosphors was prepared by solid-phase reaction in this study. Under excitation at 339 nm, these phosphors can emit red light peaking 677 nm. By comparing the PL intensity of phosphors MAO: xMn4+ (x = 0.003–0.015), the optimal concentration of Mn4+ is x = 0.009. The concentration quenching effect was found to occur at concentrations above this level. Moreover, it has good thermal stability, and when compared to 300 K, its overall intensity is 51.7% at 450 K. Finally, a prototype LED device is successfully fabricated by coating a 420 nm blue LED chip and MAO:0.009Mn4+ red phosphor, with the electroluminescent significantly overlap with the Chlorophyll a. This leads to the implication that the phosphor MAO:0.009Mn4+ can be used to produce LED lamp for plant growth.

Photoluminescence properties of Eu3+ and Al3+-doped Ca2ZnSi2O7 red phosphors for plant growth LEDs

Photoluminescence properties of Eu3+ and Al3+-doped Ca2ZnSi2O7 red phosphors for plant growth LEDs

Ca2LaTaO6:Bi3+/Mn4+ Phosphors with High Brightness Far-Red Emitting and Luminescence Enhancement for Plant Growth LED Lights and Temperature Sensor.

Herein, Bi3+/Mn4+ doped Ca2LaTaO6 phosphors with a double-perovskite structure were successfully synthesized with solid-state reaction at high temperature. The photoluminescence (PL) performances were investigated in detail. The blue radiation (∼465 nm) from the Bi3+ ion and the red radiation (∼686 nm) originating from the Mn4+ ion were obtained under 313 nm excitation. Especially, the pathway of energy transfer (Bi3+ → Mn4+) contributes to enhance the red emission intensity (Mn4+: ∼686 nm) in Ca2LaTaO6:Bi3+/Mn4+ system. The PL mechanism of Ca2LaTaO6:Bi3+/Mn4+ was analyzed through luminescence lifetimes and PL spectra. Moreover, the emitting bands of Ca2LaTaO6:Bi3+/Mn4+ were primarily matched with the absorbing bands of carotenoids and phytochrome PFR on behalf of plant growth, so the phosphors were suitable for the design of a plant growth light under near-ultraviolet to blue excitation. At last, the optical temperature dependent performances of the Ca2LaTaO6:Bi3+/Mn4+ were analyzed with luminescence intensity ratio technology. The sample has presented excellent temperature measuring relative sensitivity (SR = 2.106% K-1). The results illustrated that the Ca2LaTaO6:Bi3+/Mn4+ phosphor also can be used to develop an optical temperature sensor.

Synthesis, structural, photoluminescence, and EPR analysis of far red emitting Ca3La2W2O12:Mn4+ inorganic phosphor for applications in plant-growth LEDs

This study explores the structural and optical properties of Mn4+ doped Ca3La2W2O12 phosphor. It also investigates the incorporation of Mn4+ ions for deep red emission and electron paramagnetic resonance (EPR) analysis. The phosphors were synthesized using the sol-gel method, and their properties were thoroughly examined using a combination of X-ray diffraction (XRD), Fourier transform infrared (FT-IR), photoluminescence (PL), and EPR technique. The XRD analysis provided insights into the phase purity, and constituents of the synthesized samples. Under 345 nm excitation, we observed far red emission at 705 nm, with the highest emission intensity occurring at a concentration of 0.0025 mol of Mn4+ metal ions in the host matrix. Concentration quenching was observed due to dipole-quadrupole interactions. The CIE chromaticity coordinates confirm far red region emission, and the estimated correlated color temperature (CCT) suggests that these phosphors can be used for bright illumination. Concurrently, the EPR examination also confirmed the presence of Mn4+ ions in the host matrix and showed the effect of variation on Mn4+ concentration in the EPR spectroscopy measurements. Furthermore, the electron paramagnetic resonance analysis demonstrated a distinctive six-line spectrum with a g-factor of approximately 1.98, indicating the presence of paramagnetic Mn4+ ions. This primary line was accompanied by a broader resonance with a linewidth of 950 Gauss, partially overlapping the six-line spectrum. The initial investigation indicates that this far red emitting phosphor can be applied to plant-growth LEDs.

Double perovskite La2LiNb(1-x)O6: xMn4+ red phosphors with excellent humidity stability and high thermal stability for plant growth LEDs

In recent times, there has been significant interest in Mn4+-activated red phosphors in double perovskite oxide materials. However, the practical use of these materials is hindered by concerns related to their thermal and humidity stability. In this research, we have synthesized deep red-emitting phosphors with the composition La2LiNb(1-x)O6: xMn4+ using a conventional high-temperature solid-phase method. The microstructures and luminescence properties of these phosphors have been thoroughly investigated. All the samples consist of irregular microcrystals with an average size ranging from 3 to 7 μm, and they exhibit excellent phase purity and crystallinity. Under excitation by 335 nm ultraviolet light, the La2LiNb(1-x)O6:xMn4+ phosphors emit a narrow and sharp red band (centered at ∼710 nm), and the emission intensity initially increases and then decreases with increasing Mn4+-doping concentration, peaking at x = 0.5%. The La2LiNb0.995O6: 0.5%Mn4+ phosphor exhibits exceptional thermal stability, with a normalized emission intensity of 66.24% maintained at 150 °C. More importantly, the La2LiNb0.995O6:0.5%Mn4+ phosphor exhibits excellent humidity stability and can maintain more than 90% of its initial emission intensity after immersion in deionized water for 24 h. The La2LiNb0.995O6: 0.5%Mn4+ phosphor demonstrates an impressive resistance to humidity-induced luminescence quenching. It maintains a significantly higher far-red emission intensity at relative humidities exceeding 65%. These newly developed La2LiNb(1-x)O6: xMn4+ phosphors hold great potential as red phosphors for high-power plant growth LEDs in extended outdoor, high-humidity conditions.

Near-infrared light driven highly efficient and thermally stable Gd2Ti2O7:Er3+/Yb3+ sub-microspheres for photocatalytic and plant growth LED applications

Photocatalysis is a technique that can help address various global challenges of energy and environment by utilizing solar energy. Photocatalysts that can capture light from different regions of the electromagnetic spectrum, such as ultraviolet, visible or near-infrared, are required to optimize the use of solar energy. Therefore, researchers have been developing various strategies to design such photocatalysts. Herein, we report the NIR-induced photocatalytic performance of pyrochlore-structured Gd2Ti2O7:1Er3+/10Yb3+ (GT:Er3+/Yb3+) sub-microspheres by using rhodamine B (RhB), a commom organic dye, as a probe molecule. A facile solvothermal process was used to prepare the sub-microspheres that emitted strong red light when irradiated by a 980 nm laser. The luminescence mechanism was attributed to cross-relaxation and back energy transfer processes. Furthermore, the GT:Er3+/Yb3+ sub-microspheres exhibited remarkable thermal stability and durability under 980 nm laser irradiation and the catalytic studies showed in the presence of laser light of only 1 W input power. The sub-microspheres completely broke down RhB dye into H2O and CO2 in 10 h. This study offers a novel approach to exploit NIR-driven lanthanide materials for LED and photocatalytic applications.

Thermally stable Cr3+-activated silicate phosphors for plant-growth LEDs and three-mode optical thermometry.

The structural, optical and temperature-dependent luminescence properties of Y2Mg2Al2Si2O12:Cr3+ phosphors were investigated for their multifunctional applications. The as-prepared phosphors exhibited an intense far-red emission band around 600-850 nm with a peak at 687 nm, which matches well with the absorption band of plant phytochromes. Importantly, the optimized sample showed excellent thermal stability and its emission intensity at 423 K maintained about 77% of that at 298 K. The potential application of the phosphors in plant-growth LED devices was also demonstrated. Furthermore, owing to the unique thermal quenching behavior of Cr3+, a three-mode luminescent thermometry system was designed based on fluorescent intensity (FL), fluorescent intensity ratio (FIR), and full width at half maximum (FWHM). The maximum temperature relative sensitivity (Sr) of each mode could reach 2.74% K-1, 1.09% K-1, and 1.47% K-1, respectively. These results indicate that the Y2Mg2Al2Si2O12:Cr3+ phosphors have potential applications for plant growth and optical thermometry.

Photo and thermoluminescence of Pr3+ ions activated SrZr4(PO4)6 nanophosphors: plant growth LED and dosimetry applications

Photo and thermoluminescence of Pr3+ ions activated SrZr4(PO4)6 nanophosphors: plant growth LED and dosimetry applications

Photoluminescence properties of Sb3+-activated Ca2YTaO6 dual color emitting phosphors for plant growth LEDs applications

Developing highly efficient phosphors-converted white LEDs with excellent emissions characteristics in the blue and deep-red spectral regions, is essential for improving artificial white light for plant growth. Due to the characteristic 3Pn−1S0 transitions (n = 0, 1, 2), Sb3+ is considering as an efficient activator emitting light in the desired deep red and far-red spectral regions. In this paper, we successfully developed Sb3+-doped Ca2YTaO6 double perovskite phosphors, showing broadband doublet emission peaks, in the visible spectral ranges. Computational and experimental investigations were used to confirm the phase purity and structural analysis. The photoluminescence excitation and emission spectra, fluorescence decay curves, thermal stability and CIE chromaticity coordinates have been measured and determined to demonstrate the application potential of the Ca2YTaO6:Sb3+ double perovskites, as suitable phosphors for plant growth acceleration. The blue (420 nm) and deep red (683 nm) emission peaks were observed under 313 nm UV excitation. Efficient energy transfer was observed from the blue emission of the host phosphor to the doped Sb3+ ions, which resulted in an enhancement of the deep-red emission. The appeared dual color emission makes this phosphor a potential candidate for the generation of artificial white light for plant growth.

Realization of plant growth lighting and temperature detecting based on novel Bi3+, Sm3+ and Mn4+ doped Ca2GdNbO6 double perovskite phosphors

The Bi3+ or Sm3+ ions are introduced into Mn4+-activated Ca2GdNbO6 (CGN) double perovskite phosphors to achieve highly efficient plant growth lighting and temperature measurement. Here, the energy band and density of states for CGN are computed using density functional theory (DFT) in detail. The emission bands of CGN: Bi3+/Mn4+ consist of both the blue-light band (3P1→1S0 transition of Bi3+ ions) and red-light band (2E→4A2 transition of Mn4+ ions), which solves the issue of the lack of blue light in Mn4+-activated phosphors used in plant-growth LEDs. The electroluminescence emission spectrum of the LEDs assembled with CGN: Sm3+/Mn4+ shows a wide emission band (550–800 nm), which coincides perfectly with the absorption (550–825 nm) of Phytochrome (PR and PFR). Moreover, non-contact thermometers are designed by luminescence intensity ratio technique (LIRMn/Bi or LIRMn/Sm) with excellent absolute (Sa = 0.074 K-1@448 K or 0.036 K-1@373 K) and relative sensitivity (Sr = 2.13 %K−1@498 K or 1.11 %K−1@448 K). The results reveal that as-prepared phosphors have great potential in promoting indoor plant cultivate and optical temperature sensing.

Luminescence properties and high energy transfer of Ca9MgNa (PO4)7: Eu2+, Mn2+ blue-red dual emission phosphor for plant growth LEDs

The Ca9MgNa(PO4)7: Eu2+, Mn2+ (CMNPO: Eu2+, Mn2+) phosphors were successfully prepared via high-temperature solid-phase method. Under near ultraviolet light (n-UV) excitation, CMNPO: Eu2+, Mn2+ phosphor exhibits blue and red double emissions centered at 419 nm and 642 nm due to Eu2+: 5d → 4f transition and Mn2+: 4T1(4G) → 6A1(6S) transition, respectively, which match well with the chlorophyll a and b absorption spectrum required for plant growth. The energy transfer (ET) efficiency between Eu2+ and Mn2+ ions was analyzed and is as high as 90.0%. Besides, the luminescence mechanism and ET process of the phosphors were explained according to the simple energy level diagram of Eu2+ and Mn2+ ions. In addition, it was also found that the phosphor has good thermal stability (the luminescence intensity maintains 77.4% at 423 K). Finally, a LED device was packaged with the obtained phosphor Ca9MgNa(PO4)7: 0.03Eu2+, 0.23Mn2+ and a commercial 365 nm n-UV chip, and the corresponding color rendering index Ra and the correlated color temperature (CCT) is 83.6 and 1842 K, respectively. The results show that the optimized phosphor has good application potential in plant cultivation LEDs.

Al3+ doping enhanced photoluminescence properties of Ca2InNbO6: Mn4+ far-red phosphor for plant cultivation

The study focuses on the synthesis of far-red phosphors Ca2InNbO6: xMn4+ (0 ≤ x ≤ 0.006) and Ca2InNbO6: 0.003Mn4+, yAl3+ (0 ≤ y ≤ 0.024). First-principles calculations confirmed that the indirect bandgap of Ca2InNbO6 used to be 3.522 eV. Photoluminescence spectroscopy was used to examine the luminescence characteristics and energy transfer mechanism of CINO: xMn4+ and CINO: 0.003Mn4+, yAl3+ phosphors. When Mn4+ ions undergo the 2Eg → 4A2g transition under 380 nm excitation, brilliant red light with a central wavelength of 688 nm is released. In addition, the emission intensity reaches 2.6 times that of CINO: 0.003Mn4+, when Al3+ has a 1.2% optimal doping concentration. At the same time, the thermal stability of the material is improved. The reasons for the enhanced fluorescence and thermal stability were analysed by lattice distortion and blocking of energy transfer. Additionally, the prepared red LED lamps, which shown a bright red light even after long periods of operation at high temperatures, were used for the cultivation of plant seeds, and the germination rate as well as the stems and leaves thriving growth were significantly better than the cultivation without the red LED, suggesting that Al3+ doping Ca2InNbO6: Mn4+ has potential applications in the field of plant cultivation and growth LEDs, and is a guide for ion-doped modified phosphors.

Bi3+ sensitizer induced efficient deep-red luminescence in Mn4+-doped 4SrO‧7Al2O3 toward the applications of plant growth lamp

In the natural environment, light is an indispensable factor affecting plant growth, and plant growth phosphor-converted light emitting diodes (pc-LED) for an artificial light source can play a role in accelerating photosynthesis and development of indoor plants. In this work, we obtained a series of red-emitting phosphors Bi3+, Mn4+ co-doped 4SrO‧7Al2O3, which were synthesized by sol–gel method, and red-light emission enhancement through doping of sensitizer Bi3+. The energy transfer process and mechanism were analyzed by photoluminescence spectra and fluorescence lifetime. And it thermal stability was 58.50% at 423 K, which show that the phosphor has good photostability. The red and blue dual emission of the packaged LED device can better match the absorption spectra required by chlorophyll a, b and phytochrome PR of plants. Therefore, the as-prepared phosphor has a certain development prospect in the application of plant growth LEDs.