Plant Growth LEDs Research Articles

A new strategy to the phosphors for plant growth LEDs: Far red emission from the Ca9MY0.667 (PO4)7 (M = Li, Na):Eu3+ phosphors due to the Eu3+: 5D0 → 7F4 transition

The novel red-emitting Ca9MY0.667(PO4)7 (M = Li, Na) (CMYPO):xEu3+ (x = 0.02, 0.04, 0.07, 0.12, 0.16, 0.26, 0.35, and 0.44) phosphors were successfully synthesized by a high-temperature solid-phase reaction. The samples were evaluated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared (FT-IR) spectra, ultraviolet–visible diffuse reflectance (UV–Vis DR) spectra, photoluminescence excitation (PLE) and emission (PL) spectra. It is found that the samples can be excited by near-ultraviolet (NUV) and blue light. The intense PL peaks were centered at 614 nm due to the 5D0 → 7F2 transition. Interestingly, 5D0 → 7F4 (700 nm) far-red emission matches with the far-red absorption wavelength required for plant photosensitive pigments red (PR) and far-red (PFR) light. Moreover, the PL intensity of Ca9NaY0·667(PO4)7 (CNYPO):Eu3+ is higher than that of Ca9LiY0·667(PO4)7 (CLYPO):Eu3+. In addition, the band gaps of CLYPO and CNYPO were determined to be 3.81 and 3.61 eV, respectively. Finally, the International Commission on Illumination (CIE) chromaticity of phosphors are located in red region. The results showed that the phosphors are considered as the potential luminescence materials in white light emitting diodes (w-LEDs). Impressively, the as-prepared samples can provide reference for the development of Eu3+-doped phosphors that can be used for plant growth LEDs.

Photoluminescence properties of near-UV pumped deep red-emitting Sr2ZnGe2O7: Eu3+ phosphors for plant growth LEDs

In this paper, Eu3+-activated Sr2ZnGe2O7 (SZGO) phosphors were prepared by a traditional solid-state synthesis method. These phosphors exhibit two intense emission band around 615 nm (red) and 704 nm (deep red) under excitation at 394 nm. The dependences of the emission intensities on Eu3+ concentration was analyzed. The optimum doping concentration of Eu3+ for the phosphor is about 5 mol%. Besides, the SZGO: Eu3+ phosphor shows fluorescence tunable properties between 615 nm and 704 nm as the concentration of Eu3+ increasing. The results show that the SZGO: Eu3+ phosphor may be applied in near ultraviolet pumped plant growth LEDs.

Two single-phase ZnWO4: RE3+, Li+ (RE = Sm, Eu) white phosphors with high luminous intensity synthesized by solid-state reaction

Two series of ZnWO4: RE3+, Li+ (RE = Sm, Eu) phosphors were prepared using the facile solid-state reaction sintering at 800 °C. Its structural properties were investigated by XRD and Rietveld refinement method. The luminescence properties of the phosphors were studied, and they can be used in the white light-emitting diodes (wLEDs). Li+ was introduced into phosphors as a charge compensation agent. The influence of Li+ on the phase and luminescent properties was studied. The Vienna Ab-initio Simulation Package (VASP) software was employed to calculate the charge density differences. It is shown that the ZnWO4: Sm3+, Li+ phosphor has potential application in the plant growth LEDs.

Red shift properties, crystal field theory and nephelauxetic effect on Mn4+-doped SrMgAl10-yGayO17 red phosphor for plant growth LED light

The discovery of novel Mn4+-doped oxide red phosphor with suitable spectrum for plant growth is a hot issue in the recent years due to the characteristic red photoluminescence of 2Eg → 4A2 transition in Mn4+ ions. Generally, the emission position of Mn4+ is hard to tune because of specific crystal field in most phosphors. In this work, tunable luminescence property with obvious red shift in the spectra is observed in the Mn4+-doped SrMgAl10-yGayO17 red phosphor via simple substitution of Ga3+ for Al3+, and crystal field theory and nephelauxetic effect are employed to explain this phenomenon. Meanwhile, the Ga3+ dopant changes the shape of the spectra because Ga3+ dopant guides the replacement site of Mn4+ and changes the luminescence center. Improved emission intensity is obtained because appropriate Ga3+ doping leads to larger band gap and reduces non-radiative transitions. Phosphor-converted LED (pc-LED) devices fabricated with blue chip (470 nm) and the as-obtained SrMgAl10-yGayO17:1.0%Mn4+ phosphors emit bright blue and red light, which fit the absorption regions of plant pigments well, thus SrMgAl10-yGayO17:Mn4+ phosphor can be a candidate for plant growth LED light.

Structure identification and strongly enhanced luminescence of Sr9Y2(WO6)4: Mn4+ phosphors by co-doping Mg2+ ions for plant growth LEDs

In this paper, we reported a novel far-red emitting phosphor Sr9Y2(WO6)4: Mn4+ and alkaline earth metal Mg2+ ion co-doped phosphor Sr9Y2(WO6)4: Mn4+, Mg2+. Systematical studies on its crystal structure and luminescence properties are carried out. X-ray powder diffraction confirmed that the pure phase Sr9Y2(WO6)4: Mn4+ and Sr9Y2(WO6)4: Mn4+, Mg2+ phosphors show a single phase. Upon 350 nm excitation, the phosphors could emit far-red emission in the range of 600–800 nm, peaking at 680 nm (14,706 cm−1) due to the 2Eg→4A2g transition, with broad spectra overlap with the absorption band of phytochrome PFR. The optimal doping concentration, concentration quenching mechanism, as well as the content and temperature dependent decay times of Sr9Y2(WO6)4: Mn4+ phosphors are studied in detail. Impressively, Mg2+ dopant is found to strongly improve the luminescence of Mn4+ and the related mechanisms are deeply studied. Ultimately, a far-red light emitting diode lamp is fabricated by exciting a far red phosphor Sr9Y2(WO6)4: 0.0025Mn4+, 0.01Mg2+ using a 365 nm n-UV illuminating LED chip. Our studies have shown that Sr9Y2(WO6)4: Mn4+, Mg2+ phosphors have potential application in controlling or adjusting plant growth in plant-lighting.

Novel Mn4+ doped red phosphors composed of MgAl2O4 and CaAl12O19 phases for light-emitting diodes.

Red emitters based on CaAl12O19:Mn4+ have been attracting extensive attention due to their advantages of being rare-earth-free and chemically stable. However, their relatively low luminescence efficiencies will seriously hinder their application in light-emitting diodes (LEDs). In this regard, the promising red phosphors of CaAl12O19:Mn4+ were synthesized with enhanced luminous efficiency by introducing the coexisting phase of MgAl2O4. Importantly, an approximately 5 times enhancement of integrated intensity in the emission spectrum was observed for the phosphor with the coexisting phase compared to that with a single phase. Their crystal structures, morphologies and photoluminescence properties and the mechanism of improved luminescence were systematically investigated. Upon exciting them by using near-ultraviolet or blue LEDs, an efficient red emission was achieved with a maximum peak at ∼658 nm. In order to evaluate their potential application, a warm white LED and a plant growth LED were fabricated by using the prepared phosphors in combination with YAG:Ce3+ and InGaN-based blue chips.

Investigation of enhanced far-red emitting phosphor GdAlO3:Mn4+ by impurity doping for indoor plant growth LEDs

Phytochrome is indispensable for plant growth, which can absorb light useful for sprout, blossom, fruits. Generally, Phytochrome PR absorbs red light and Phytochrome PFR absorbs far-red light. The emission of Mn4+ doped GdAlO3 is situated in far-red light region. Herein, GdAlO3:Mn4+, Mg2+(GAL:Mn4+, Mg2+) phosphors were successfully synthesized via sol-gel method and the crystalline structure and luminescence properties were investigated systematically. Impressively, the emission intensity of GAL: Mn4+ phosphors was raised by Mg2+ and Ge4+ doping, and the mechanism of improved luminescence was also discussed. Depending on photoluminescence excitation and photoluminescence spectroscopy, the crystal field strength of the GdAlO3 host was calculated. In addition, excellent color purity and good thermal stability were found in Mg2+ co-doped GdAlO3:Mn4+ phosphors. Furthermore, the luminescence spectrum of GAL: Mn4+, Mg2+ phosphor was agreed well with the absorption of Phytochrome PFR, which convincingly confirmed that Mg2+ co-doped GdAlO3:Mn4+ phosphors show promise in indoor plant growth LEDs.

Facile synthesis of the desired red phosphor Li2Ca2Mg2Si2N6:Eu2+ for high CRI white LEDs and plant growth LED device

AbstractThe red emission with suitable peak wavelength and narrow band is acutely required for high color rendering index (CRI) white LEDs without at the cost of the luminous efficacy. Herein, the Li2Ca2Mg2Si2N6:Eu2+ red phosphor was prepared with facile solid‐state method using Ca3N2, Mg3N2, Si3N4, Li3N, and Eu2O3 as the safety raw materials under atmospheric pressure for the first time, which shows red emission peaking at 638 nm with full width at half maximum (FWHM) of 62 nm under blue light irradiation and becomes the desired red phosphor to realize the balance between luminous efficacy and high CRI in white LEDs. The morphology, structure, luminescence properties, thermal quenching behavior, and chromaticity stability of the Li2Ca2Mg2Si2N6:Eu2+ phosphor are investigated in detail. Concentration quenching occurs when the Eu2+ content exceeds 1.0 mol%, whereas high‐temperature photoluminescent measurements show a 32% drop from the room‐temperature efficiency at 423 K. In view of the excellent luminescence performances of Li2Ca2Mg2Si2N6:Eu2+ phosphor, a white LEDs with CRI of 91 as a proof‐of‐concept experiment was fabricated by coating the title phosphor with Y3Al5O12:Ce3+ on a blue LED chip. In addition, the potential application of the title phosphor in plant growth LED device was also demonstrated. All the results indicate that Li2Ca2Mg2Si2N6:Eu2+ is a promising red‐emitting phosphor for blue LED‐based high CRI white LEDs and plant growth lighting sources.

Novel orange–red emitting phosphor Sr8ZnY(PO4)7:Sm3+ with enhanced emission based on Mg2+ and Al3+ incorporation for plant growth LED lighting

Abstract In this paper, a series of novel orange-red emission phosphors Sr8ZnY(PO4)7:Sm3+ (SZYP:Sm3+) were synthesized by high-temperature solid-state reaction. The photoluminescence and concentration-dependent properties of this phosphor were investigated carefully through diffuse reflection spectra, excitation and emission spectra, Commission Internationale de l'Eclairage (CIE) chromaticity coordinate and decay times. SZYP:Sm3+ could be efficiently excited by n-UV and blue lights which center at 318, 345, 363, 376, 401, 410, 440 and 475 nm, respectively. The characteristic orange-red emission peaking at 563, 601 and 647 nm had been detected, which should be attributed to the characteristic f–f forbidden transition of Sm3+. The internal quantum efficiency (IQE) of ideal phosphor of SZYP:0.09Sm3+ reached as high as 47%. In addition, The concentration quenching mechanism and thermal stability of SZYP:Sm3+ were further investigated. It was found SZYP:Sm3+ can maintain 93% of initial emission intensity at 150 °C and the corresponding activation energy was calculated to be 0.26 eV based on Arrhenius formula. The emission intensity of 1.0Mg2+ and 0.02Al3+ incorporated SZYP:0.09Sm3+ reached up to 134% and 117% of the initial value, respectively. Moreover, (light-emitting diodes) LED devices were fabricated by employing the optimized samples as orange-red component with 365 nm n-UV chips. The desired emission in plant absorption region and extremely high thermal stability imply that SZYP:Sm3+ is suitable for the application in plant growth LED lighting.

Synthesis and photoluminescence properties of Eu2+/Eu3+ or Ce3+/Eu3+ co-doped Sr5(BO3)3F compounds

The synthesis and photo-luminescence properties of Eu2+/Eu3+ or Ce3+/Eu3+ co-doped Sr5(BO3)3F compounds are reported. Using the Sr5(BO3)3F as the host, through the solid state reaction under the reductive atmosphere, Eu2+/Eu3+ and Ce3+/Eu3+co-doped samples were prepared. These compounds exhibit good photo-luminescence properties. Under the excitation of 376 nm, an unusual red orange emission coming from the Eu2+ ions can be obtained in Eu ions doped Sr5(BO3)3F, which exhibits a broadband emission in the range of 450–800 nm with the peak at around 600 nm. At the same time, the characteristic f-f excitation and emission of Eu3+ can improve and adjust the Eu2+ emission in Eu3+/Eu2+ codoped Sr5(BO3)3F. In addition, the adjustable luminescence properties from blue to white of Sr5(BO3)3F:Ce3+, Eu3+ are investigated. The energy transfer behavior from Ce3+ to Eu3+ was confirmed. In the spectra of the co-doped samples, we can hardly observe the characteristic peak of Eu2+, because Ce4+ can oxidize Eu2+ to Eu3+, and Ce4+ itself is reduced to Ce3+. The CIE coordinates from (0.2758, 0.2420) to (0.3857, 0.3015) show Sr5(BO3)3F:3%Ce3+, x%Eu3+ (x = 1,3,5,7,9) are in the white light emission region. All results demonstrate that the Sr5(BO3)3F:Eu3+/Eu2+ and Sr5(BO3)3F:Ce3+/Eu3+ phosphors have good application prospects for LED plant growth and white LED, respectively. The bond energy method was used to explain the reason why the Eu2+/Eu3+ ion instead of only Eu2+ and Ce3+/Eu3+ instead of Ce3+/Eu3+/Eu2+ can exist in the host Sr5(BO3)3F. The theoretical analysis agree well with the experimental result.

High-efficient and thermal-stable Ca19Zn2(PO4)14: Eu2+, Mn2+ blue-red dual-emitting phosphor for plant cultivation LEDs

A series of dual-emitting Eu2+, Mn2+ co-doped Ca19Zn2(PO4)14 (CZP) phosphors capable for plant cultivation LEDs are synthesized. As a sensitzer, Ca19Zn2(PO4)14: Eu2+ emits a dominant blue light with green shoulder by Eu2+ occupying CaO8 and CaO6 sites, respectively. Mn2+ was introduced into CZP: Eu2+ to obtain the red emission component. The as-synthesized CZP: Eu2+, Mn2+ phosphor shows a blue emission peaking at 415 nm and significantly enhanced deep-red emission peaking at 650 nm under single UV excitation, which should be attributed to the existence and energy transfer of Eu2+ and Mn2+, respectively. The emission spectra match well with the plants’ photosynthetic action spectra (PAS) for both red and blue lights simultaneously. Energy transfer from Eu2+ to Mn2+ enables a facile tune of emitting color from blue to red, and the corresponding mechanism is revealed to be the electric dipole-dipole interaction by analyzing Eu2+/Mn2+ decay lifetime variations. High quantum efficiency (93.3%) and favorable thermal stability (68% of RT intensity at 473 K) clearly verify the good properties of CZP: Eu2+, Mn2+ phosphor. Results confirmed that CZP: Eu2+, Mn2+ phosphor might have great applicational potential in plant growth LED lighting.

Synthesis and photoluminescence properties of novel red-emitting phosphor SrAl3BO7:Mn4+ with enhanced emission by Mg2+/Zn2+/Ca2+ incorporation for plant growth LED lighting

Indoor cultivation has attracted more and more concerns in the last few years. Searching for ideal red-emitting phosphors for this application has been a great challenge. In this paper, a novel red-emitting phosphor SrAl3BO7:Mn4+ (SABO:Mn4+) had been synthesized through a modified hydrothermal reaction method for the first time. Three kinds of effect parameters, including hydrothermal reacting time, sintering temperature and Mn4+ doping concentration, were comprehensively considered to optimize the phase purity and luminescent properties of the SABO:Mn4+ phosphor. Besides, the luminescent properties of SABO:Mn4+ was systematically investigated through UV–vis absorption spectra, PLE and PL spectra, CIE chromaticity coordinate and decay times. The excitation band of this phosphor locates in the wavelength range of 250–550 nm, resulting from Mn4+ → O2− charge transfer and electron transitions from 4A2–4T1, 2T2 and 4T2 energy levels. Meanwhile, a sharp emission band is detected from 600 to 700 nm with two emission peaks located at 648 and 662 nm, which is assigned to 2E → 4A2 characteristic transition of Mn4+. In addition, Mg2+/Zn2+/Ca2+ are co-doped as charge compensators to improve the luminescent properties of SABO:0.03Mn4+. The impacts of doping concentration of Mg2+/Zn2+/Ca2+ on the photoluminescent intensity, QE and thermal stability of SABO:0.03Mn4+ phosphor is investigated carefully. The corresponding mechanism is discussed via decay times, EPR spectra and configurational coordinated diagram. More importantly, the EL spectrum of as-fabricated pc-LED device matches well with the absorption of plant pigments, demonstrating this novel phosphor can regard as a promising red-emitting luminescent material to meet the light requirement in plant growth LED lighting.

Synthesis and photoluminescence properties of a novel Ca2LaNbO6:Mn4+ double perovskite phosphor for plant growth LEDs

In this paper, a series of Ca2LaNbO6 (CLN):Mn4+ far-red phosphors with different doping concentration were successfully prepared by traditional high temperature solid state method at 1250 °C. The samples were characterized and analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence excitation (PLE) spectra, photoluminescence (PL) spectra, ultraviolet–visible diffuse reflectance spectra (UV–Vis DRS), temperature-dependent emission spectra and internal quantum efficiency (IQE). The particle size of CLN is < 3 μm. The strongest excitation peak of CLN:Mn4+ phosphors lies at 352 nm, which is attributed to the 4A2g → 2T2g transition of Mn4+ ions. The sample has a strong emission peak at 684 nm, which corresponds to the 2Eg → 4A2g energy level transition of Mn4+ ions. The optimum doping concentration of the sample is 0.03 mol%, and the quenching mechanism is dipole–quadrupole interaction. In addition, the thermal activation energy of the sample was calculated to be 0.368 eV. Importantly, under the excitation of near-ultraviolet light at 365 nm and driven by 25 mA current, the LED with CLN:0.0003Mn4+ emits bright far-red light. All the results indicated that CLN:Mn4+ phosphors have potential application value in indoor plant cultivation.

Novel red-emitting CsPb1−xTixI3 perovskite QDs@glasses with ambient stability for high efficiency white LEDs and plant growth LEDs

Currently, the application of all-inorganic cesium lead halide perovskite (CsPbX3, X = Cl, Br, I) quantum dots (QDs) is limited due to toxicity of lead and poor ambient stability. In our work, a series of Ti-doped CsPbI3 QDs were successfully prepared in borosilicate glass (SiO2-B2O3-ZnO) by the melt quenching and in situ crystallization technique. The samples showed excellent water/thermal stability, and the tunable emission (650–695 nm) was controlled by different Ti contents and heat treatment temperatures. In particular, the optical properties of CsPb1−xTixI3 QDs@glasses (x ≤ 0.5) are superior to those of pristine CsPbI3 QDs@glass. As a result, the wLED was assembled using red-emitting CsPb1−xTixI3 QDs@glasses and yellow-emitting Ce3+:YAG phosphor under excitation of InGaN blue chip, which demonstrated an outstanding luminous efficiency of 102.44 lm/W, a high color rendering index of 80.6. Particularly, Ti-doped CsPbI3 QDs@glasses with red and far-red light are combined with a blue-chip to assemble an LED device, which exactly satisfies the lighting conditions of plant growth.

Deep-red-emitting Ca2LuSbO6:Mn4+ phosphors for plant growth LEDs: Synthesis, crystal structure, and photoluminescence properties

High-efficiency light source based on inorganic luminescence material is of great benefit to the development of plant cultivation. Herein, a series of novel Mn4+ activated Ca2LuSbO6 compounds with various doping concentrations were synthesized via a high-temperature solid-state reaction. The phase formation and crystal structure were analyzed by X-ray diffraction and the luminescence characteristics were also discussed systematically. The as-prepared samples exhibited two broad excitation bands ascribed to d-d transitions of Mn4+ ions, and upon 345 nm excitation the phosphors showed an intense deep-red emission centered at 683 nm due to the 2Eg→4A2g transition, which matched well with the absorption region of light source required for plant growth (∼660 nm). And the Ca2LuSbO6:Mn4+ phosphors exhibited the highest emission intensity when the Mn4+ doping concentration was 0.5 mol%. Additionally, Ca2LuSbO6:0.5%Mn4+ phosphor sample possessed high internal quantum efficiency of 39.1% and its CIE coordinates were (0.725, 0.275). The thermal stability was also commendable that the 683 nm deep-red emission intensity at 423 K (150 °C) maintained 48% of that at room temperature (303 K).

Enhancing quantum efficiency and tuning photoluminescence properties in far-red-emitting phosphor Ca14Ga10Zn6O35:Mn4+ based on chemical unit engineering

Mn4+ activated Ca14Ga10Zn6O35 (CGZO) have attracted much attention for the usages of white light-emitting-diodes (WLEDs), solar cells and plant growth LEDs. In this paper, we conducted chemical unit engineering in CGZO:Mn4+ by substituting Ge4+-M+ (M = Li, Na, K) for Ga3+-Ca2+. The impacts of Ge4+-M+ (M = Li, Na, K) substitution on the crystal structure, photoluminescence properties, quantum efficiency (QE) and thermal stability were investigated systematically. With the increase of Ge4+-Li+/Na+ and Ge4+-K+, the diffraction peaks moved towards higher and lower angle, respectively. The greatest improvement of emission intensity in Ge4+-Li+/Na+/K+ co-doped CGZO:Mn4+ reached up to 169.4%, 195.0% and 198.9%. Moreover, an obvious red shift (∼3.6 nm) was detected in Ge4+-Li+ case and this change was interpreted by Tanabe–Sugano diagram. The IQE and EQE of Ge4+-Li+/Na+/K+ co-doped CGZO:Mn4+ showed remarkable improvements. The highest values of IQE and EQE were found to be 50.9% and 38.9% in Ge4+-K+ incorporated sample. Furthermore, conducting chemical unit engineering in CGZO:Mn4+ could slightly enhance its thermal stability. The configurational coordinated diagram was employed to understand this enhancement comprehensively. Finally, LED devices were fabricated by using Ge4+-Li+ co-doped CGZO:Mn4+ phosphor as light convertor. The excellent electronic luminescence (EL) properties and matchable emission with the absorption of plant pigments demonstrating that these phosphors have promising application in plant growth LED lighting.

A novel deep red emission phosphor BaAl2Ge2O8:Mn4+ for plant growth LEDs

The luminescence properties of BaAl2Ge2O8:Mn4+ are investigated in this paper. The excitation spectrum of BaAl2Ge2O8:Mn4+ shows two broad bands. The absorption band centred at 288 nm is attributed to the overlap of the Mn4+-O2− charge transfer transition and the 4A2 → 4T1 transition of the Mn4+ ions. The weak absorption band centred at 435 nm is attributed to the 4A2 → 4T2 transition of the Mn4+ ions. The luminescence spectrum shows two emission peaks at 652 nm and 668 nm due to the 2E → 4A2 transition of the Mn4+ ions. As the concentration of the Mn4+ ions increases, the lifetime of the phosphor decreases from 1.766 ms to 1.595 ms. The chromaticity coordinates are (0.720, 0.279), which is a deep red emission. The luminescence of BaAl2Ge2O8:Mn4+ contributes to plant growth and can be applied to plant illumination sources.

CaYAlO4:Mn4+,Mg2+: An efficient far-red-emitting phosphor for indoor plant growth LEDs

Recently, the LEDs technology has been widely used as the light source for indoor plant growth in agricultural area. Previous studies demonstrated that blue light around 450 nm (400–500 nm), red light around 660 nm (620–690 nm), and far-red light around 730 nm (700–740 nm) play important roles in reactions of photosynthesis, phototropism and photomorphogenesis. Thus, in this work, in order to find suitable far-red-emitting phosphors for plant growth LEDs, a series of CaYAlO4:Mn4+,Mg2+ (CYA:Mn4+,Mg2+) phosphors were synthesized and their crystal structure, morphology and photoluminescence properties were investigated. These CYA:Mn4+,Mg2+ phosphors had two broad excitation band in the 250–600 nm wavelength range with peaks at 348 and 469 nm. When excited by 348 nm, the CYA:Mn4+,Mg2+ phosphors emitted efficient far-red light around 710 nm, which could match well with the absorption spectrum of phytochrome PFR. The luminescence mechanism was studied in detail. The optimal doping concentrations of Mn4+ and Mg2+ ions were determined to be about 0.4 and 1 mol%, respectively. The CIE chromaticity coordinates of optimized CYA:0.4%Mn4+,1%Mg2+ sample were (0.7174, 0.2825), and its internal quantum efficiency reached as high as 48%. Thus, the CYA:Mn4+,Mg2+ phosphors would have great potential for applying in future plant growth LEDs.

Photoluminescence properties of Ba2LaSbO6:Mn4+ deep-red-emitting phosphor for plant growth LEDs

In this work, Ba2LaSbO6:Mn4+ phosphors are prepared successfully in air by solid-state reaction method, which is confirmed by the X-ray powder diffractions patterns, decay curves, the time-resolved emission spectra and luminescence properties. Monitored at 678 nm, the excitation spectrum of Ba2LaSbO6:Mn4+ phosphor is observed in the range of 250–575 nm. Under the excitation of 380 nm, Ba2LaSbO6:Mn4+ phosphor exhibits strong deep-red emission in the range of 625–740 nm with emission peak at 678 nm due to the 2E → 4A2 transition of Mn4+ ion. The emission spectrum well matchs with the absorption spectrum of plants in the range of 625–740 nm. The temperature-dependent emission spectra illustrate the thermal stability of Ba2LaSbO6:Mn4+ phosphor and the thermal quenching mechanism is explained by the configuration coordinate of Mn4+ ion. The luminous mechanism of Ba2LaSbO6:Mn4+ phosphor is explained by the Tanabe-Sugano energy level diagram of Mn4+ ion. The experimental results show that the Ba2LaSbO6:Mn4+ deep-red-emitting phosphor would have potential application in plant growth LEDs.

Highly efficient and dual broad emitting light convertor: an option for next-generation plant growth LEDs

At present, blue-red composite LED light sources used for plant lighting are mainly composed of blue light and red light; the blue light is provided by gallium nitride LED chips, but the full-width at half-maximum (FWHW) is only approximately 25 nm, while the blue light required by plants for photosynthesis is wider.