Preparation and characterization of a novel far-red phosphor powder SrBaGdNbO6: Mn4+ for indoor plant cultivation lighting

High-efficiency and thermally stable far-red emission of Mn4+ in double cubic perovskite Sr9Y2W4O24 for plant cultivation

Far-red phosphors featuring high quantum efficiency and emission bands that strongly overlap with the absorption spectra of plant pigments are crucial for advancing plant cultivation lighting technology. Restricted by the large Stokes shift, far-red phosphors typically exhibit low energy efficiency. Moreover, many far-red phosphors suffer from low quantum efficiency, which has emerged as a critical issue in the research of these materials. To address the issue, conventional strategies-including crystal field engineering, defect engineering, and sensitizer doping-have been widely adopted to enhance their emission intensity. In this work, we propose a novel and effective strategy to improve the emission performance of far-red phosphors: low-melting-point magnesium chloride has been introduced as a flux to regulate the reaction pathway of the composite oxide phosphor Ca14Mg5.94Li0.03In0.03Ga9.95O35:0.05Mn4+ (CMLIGO:0.05Mn4+). The cubic intermediate product with a structure analogous to the target product has been designed to form a compact lattice structure and reduce crystal defects, thereby enhancing the luminescence intensity and quantum efficiency of the phosphor. The Ca14Mg5.94Li0.03In0.03Ga9.95O35:0.05Mn4+@3 wt% MgCl2 (CMLIGO:0.05Mn4+@3 wt% MgCl2) shows a broad excitation band (250-600 nm) and far-red emission centered at 720 nm (650-800 nm). Under 365 nm excitation, the CMLIGO:0.05Mn4+@3 wt% MgCl2 exhibits an internal quantum efficiency of 91.4%. Benefiting from its high internal quantum efficiency and the emission band that matches well with the absorption spectrum of phytochrome in the far-red absorbing form (phytochrome Pfr), CMLIGO:0.05Mn4+@3 wt% MgCl2 demonstrates promising potential for applications in plant cultivation lighting. This work offers a new direction for synthesizing and modification of composite oxide phosphors.

A novel far-red phosphors Li2ZnTi3O8:Cr3+ for indoor plant cultivation:Synthesis and luminescence properties

Synthesis and photoluminescence properties of novel Ca2LaSbO6:Mn4+ double perovskite phosphor for plant growth LEDs

A novel Mn4+ activated CaYMgSbO6 (CYMS) far-red phosphor was synthesized by high temperature solid state reaction. The sample was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), luminescence spectra, ultraviolet–visible spectra, emission-temperature relationship and internal quantum efficiency (IQE). It is found that CYMS:Mn4+ phosphor has a strong broad excitation band in the range of 200–550 nm. The sample can be excited by ultraviolet and blue light. There is a wide emission band centered at 688 nm between 600 and 760 nm. The optimum doping concentration of Mn4+ is approximately 0.2 mol%. In addition, all the Commission Internationale de L’Eclairage (CIE) chromaticity coordinates of CYMS:0.002Mn4+ located in the far-red region. The concentration quenching mechanism is the dipole-quadrupole interaction of Mn4+ activator. The sample has excellent thermal stability (I423K/I298K = 53.2%). Importantly, the CYMS:0.002 Mn4+ phosphor has an IQE up to 51.5%. Finally, a 365 nm ultraviolet light emitting diode chip combined with CYMS:0.002 Mn4+ phosphor was used to fabricate the LED device. All the results indicated that CYMS:Mn4+ phosphors have potential applications in indoor plant cultivation.

Effects of Ti4+- and W6+-substitution on photoluminescence properties of Sr2GdSbO6:Mn4+ phosphor for plant cultivation

A novel double-perovskite LiLaMgTeO6: Mn4+ far-red phosphor for indoor plant cultivation white LEDs: Crystal and electronic structure, and photoluminescence properties

Mn4+ doped tetratungstate Sr9Gd2W4O24 far-red phosphor: Synthesis, luminescence properties, and potential applications in indoor plant cultivation

Synthesis and characterization of a far-red-emitting Sr2ScNbO6: Mn4+ phosphor for short-day plant cultivation

Novel Mn4+-activated far-red emitting SrMg2La2W2O12 (SMLW) phosphors were prepared by a conventional high-temperature solid-state reaction method. The SMLW:Mn4+ phosphors showed a broad excitation band peaking at around 344 nm and 469 nm in the range of 300–550 nm. Under 344 nm near-ultraviolet light or 469 nm blue light, the phosphors exhibited a far-red emission band in the 650–780 nm range centered at about 708 nm. The optimal Mn4+ doping concentration in the SMLW host was 0.2 mol% and the CIE chromaticity coordinates of SMLW:0.2% Mn4+ phosphors were calculated to be (0.7322, 0.2678). In addition, the influences of crystal field strength and nephelauxetic effect on the emission energy of Mn4+ ions were also investigated. Moreover, the internal quantum efficiency of SMLW:0.2% Mn4+ phosphors reached as high as 88% and they also possessed good thermal stability. Specifically, the emission intensity at 423 K still maintained about 57.5% of the initial value at 303 K. Finally, a far-red light-emitting diode (LED) lamp was fabricated by using a 365 nm near-ultraviolet emitting LED chip combined with the as-obtained SMLW:0.2% Mn4+ far-red phosphors.

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

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.

Highly efficient and thermally stable CaMgLaSbO6:Mn4+ red phosphor for indoor plant growth

A novel Mn4+-activated garnet-type Li5La3Nb2O12 far red-emitting phosphor with high thermal stability for plant cultivation

Novel double-perovskite SrLaLiTeO6:Mn4+ far-red phosphor with superior thermal stability for indoor plant growth LED