Phosphor For Plant Growth LEDs Research Articles

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.

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

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.

Synthesis and photoluminescence properties of a novel double perovskite NaGdMgTeO6:Sm3+ red-emitting phosphor for plant growth LEDs and w-LEDs

This research used solid-state reaction methods to synthesize a series of double perovskite structure NaGdMgTeO6:xSm3+ (x = 0.5−30 mol%) phosphors. A systematic study was conducted on the crystal structure, phase purity, photoluminescence (PL) properties, concentration quenching mechanism, color purity, thermal stability, and inner quantum efficiency (IQE) of the samples. Under 405 nm excitation, NaGdMgTeO6:Sm3+ phosphors showed strong red emission at 648 nm, attributed to the 4G5/2 → 6H9/2 transition of Sm3+ ions. The optimal luminescence intensity was achieved at the dopant concentration of 1 mol%, and the dipole-dipole interaction mechanism contributed to the concentration quenching process. High color purity of more than 99.8% and appropriate Commission International de L'Eclairage (CIE) chromaticity coordinates were obtained for the NaGdMgTeO6:Sm3+ phosphors. High thermal stability and activation energy (Ea = 0.293 eV) were found to be excellent characteristics of the phosphors. Ultimately, the fabricated red LED in this study revealed superior spectral matching with the phytochrome Pr. The white light-emitting diode (w-LED) prepared had a high color rendering index (Ra) of 90 and a suitable correlated color temperature (CCT) of 5337 K. As a result, these phosphors are potentially suitable for use in plant growth LEDs and w-LEDs.

Sol-Gel Synthesis and Photoluminescence Properties of a Far-Red Emitting Phosphor BaLaMgTaO6:Mn4+ for Plant Growth LEDs.

Far-red (FR) emitting LEDs are known as a promising supplement light source for photo-morphogenesis of plants, in which FR emitting phosphors are indispensable components. However, mostly reported FR emitting phosphors are suffering from problems of wavelength mismatch with LED chips or low quantum efficiency, which are still far from practical applications. Here, a new efficient FR emitting double-perovskite phosphor BaLaMgTaO6:Mn4+ (BLMT:Mn4+) has been prepared by sol-gel method. The crystal structure, morphology and photoluminescence properties have been investigated in detail. BLMT:Mn4+ phosphor has two strong and wide excitation bands in the range of 250-600 nm, which matches well with a near-UV or blue chip. Under 365 nm or 460 nm excitation, BLMT:Mn4+ emits an intense FR light ranging from 650 to 780 nm with maximum emission at 704 nm due to 2Eg → 4A2g forbidden transition of Mn4+ ion. The critical quenching concentration of Mn4+ in BLMT is 0.6 mol%, and its corresponding internal quantum efficiency is as high as 61%. Moreover, BLMT:Mn4+ phosphor has good thermal stability, with emission intensity at 423 K keeping 40% of the room temperature value. The LED devices fabricated with BLMT:Mn4+ sample exhibit bright FR emission, which greatly overlaps with the absorption curve of FR absorbing phytochrome, indicating that BLMT:Mn4+ is a promising FR emitting phosphor for plant growth LEDs.

Structure and luminescence of a high-efficient blue-red-emitting Na2BaMg(PO4)2: Eu2+, Mn2+ phosphor for plant growth LEDs

New dual-emitting phosphor Na2BaMg(PO4)2: Eu2+, Mn2+ is prepared via conventional sintering method. The structural and luminescent properties of as-synthesized phosphor were systematically studied by experimental characterization and theoretical calculation. Utilizing the Eu2+→Mn2+ energy transfer, this phosphor exhibits efficient double-band emissions at 415 and 620 nm, which has a good match with the absorption spectra of chlorophyll A/B and phytochrome in plants. The energy transfer mechanism had been investigated through emission intensity and decay lifetime variation using Reisfeld's approximation method. Na2BaMg(PO4)2: Eu2+, Mn2+ shows promising properties like good thermal stability (75% emission intensity maintenance at 200 °C) and high quantum efficiency (QE > 80%). A prototype LED was fabricated using optimized phosphor and NUV chip, which exhibits two distinct emission peaks modulating an optimum action spectrum for plant absorption. All results indicate that Na2BaMg(PO4)2: Eu2+, Mn2+ is of great potential as converted component for plant growth LEDs.

Enhanced Thermal Stability and Far-Red Emission of Al3+ Ions Co-Doped Ba2ysbo6: Mn4+ Phosphors for Plant Growth Leds

Enhanced Thermal Stability and Far-Red Emission of Al3+ Ions Co-Doped Ba2ysbo6: Mn4+ Phosphors for Plant Growth Leds

Luminescent properties of Mn4+-doped LaTiSbO6 deep-red-emitting phosphor for plant growth LEDs

Mn4+-doped double-perovskite LaTiSbO6 (LTS) phosphors were fabricated via traditional high-temperature sintering reaction. The crystal structure, composition, and luminescent properties of the LTS:Mn4+ phosphors were studied. The PLE spectrum presents two broad bands that are centered at 356 and 475 nm, and they match the UV and blue chips. A broad emission band that is centered at 685 nm is presented in the PL spectrum. The quantum efficiency is 21.3%. A red light LED device was also fabricated with LTS:0.007Mn4+ phosphor and an InGaN chip (465 nm). The CCT, CRI, and luminous efficiency of the LED are 4215 K, 73.4, and 62.1 Im/W, respectively. The LED spectrum meets the needs of plant growth in blue and red light. Therefore, the LED fabricated by LTS:Mn4+ phosphor is a potential light source for plant growth.

Photoluminescent properties of red-emitting phosphor BaMgAl10O17:Cr3+ for plant growth LEDs

Abstract Narrow-band red-emitting phosphor Cr3+-doped BaMgAl10O17 (BAM) was successfully synthesized via a sol – gel method. The obtained Cr3+-doped BaMgAl10O17 phosphor with average particle size of about 1 μm emits an intense red light at around 695 nm with two broad excitation bands at 405 and 560 nm. The highest PL intensity is achieved at the Cr3+ doping concentration of 1 mol% and the annealing temperature of 1400 °C. The Tanabe-Sugano diagram reveals that Cr3+ ions are affected by the strong crystal field with the Dq/B ratio value of ~2.7, and the peak at 695 nm is attributed to the 2E→4A2 transitions of Cr3+ ions. A purple LED with colour coordinates of (0.263, 0.148) has been fabricated by coating the Cr3+-doped BaMgAl10O17 phosphor on a violet LED (410 nm) chip. The results indicate that BaMgAl10O17:Cr3+ phosphor could be promising red phosphor for plant growth LEDs.

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.

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.

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).

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.

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

As a potential far-red-emitting candidate for plant growth LEDs, Mn4+ activated oxide phosphors have brand-new application prospects. However, it remains a significant challenge to develop highly efficient far-red-emitting phosphors due to their intrinsic energy loss in a large Stokes shift. Herein, we present a rational charge compensation strategy with a fusible charge compensator MgF2 at the molecular level to synthesize a LaAlO3:Mn4+,Mg2+ far-red-emitting phosphor. Notably, MgF2 can play an essential role in the incorporation of Mn4+ into the crystal matrix during the high-temperature solid-state reaction process, and thus induce a highly luminescent phosphor with a quantum yield of 78.6% and appropriate thermal stability. The fabrication of a high-performance far-red-emitting phosphor-converted LED further identifies the application potential of the modified Mn4+ activated LaAlO3 phosphor. This finding sheds light on the further exploration of high-grade far-red phosphors.

Synthesis and photoluminescence properties of deep red-emitting CaGdAlO4:Mn4+ phosphors for plant growth LEDs

In this work, we reported on novel Mn4+-activated CaGdAlO4 (CGA) deep red-emitting phosphors. Under 349 nm excitation, the CGA:Mn4+ phosphors showed a deep-red emission band within the wavelength range of 650–800 nm centered at 715 nm due to the 2Eg→4A2 g transition of Mn4+ ions. CGA:Mn4+ phosphors had two broad excitation bands in the 250–550 nm region. The optimal doping concentration of Mn4+ was about 0.2 mol%. The CIE chromaticity coordinates of CGA:0.2%Mn4+ sample were (0.7132, 0.2866), and the lifetimes of CGA:xMn4+ phosphors monitored at 715 nm showed a decrease with increasing Mn4+ doping concentration in the range of 0.05–1.0 mol%. Importantly, the CGA:0.2%Mn4+ sample had internal quantum efficiency as high as 45%. Finally, a deep-red LED device was prepared by integrating a 365 nm near-UV InGaN chip and CGA:0.2%Mn4+ phosphors.

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.