A Highly Efficient Eu²⁺ Excited Phosphor with Luminescence Tunable in Visible Range and Its Applications for Plant Growth

Abstract

Among these aforementioned types of light, blue and red light are particularly crucial for plant growth and fruit maturity. [2] Several traditional light sources for indoor plant cultivation, including incandescent lamps, high-pressure halogen lamps, and xenon lamps, have been employed; however, they have disadvantages such as high energy consumption, short work life, and spectral mismatch. [3] Therefore, light-emitting diodes (LEDs) with benefits such as reduced energy consumption, long lifespan, spectral matching, and environmental friendliness have been developed to specifically facilitate indoor plant cultivation. In addition, novel films capable of transforming light for plant growth are being currently developed; these light-conversion films directly utilize sunlight and can be employed for large-scale outdoor cultivation. Epoxy resin films containing dispersed CaAlSiN 3 :Eu 2+ particles and polyethylene films containing dispersed Sr 2 Si 5 N 8 :Eu 2+ particles are typical examples of light-conversion films for sunlightdriven plant growth. [4] Phosphors appropriate for generating light for plant growth are primarily excited by Mn 4+ , Mn 2+ , and Eu 2+ . The emission spectrum of Mn 4+ is attributed to the transitions of 2 E(t 2 3 ) → 4 A 2 (t 2 3 ) (620-750 nm), [5] and the excitation spectrum is primarily attributable to the 4 A 2 → 4 T 1 (≈350 nm) and 4 A 2 → 4 T 2 (≈455 nm) transitions. [6] However, the parity-and spin-forbidden transitions during emission and the parityforbidden transition during excitation diminish the excitation and emission, which does not favor plant growth. [7] Typical red phosphors such as YAG:Mn 4+ , [8] Sr 4 Al 14 O 25 :Mn 4+ , [9] Ca 3 Al 4 ZnO 10 :Mn 4+ , [10] and SrMgAl 10 O 17 :Mn 4+[1d] have been developed to date. Mn 2+ exhibits an emission spectrum originating from the weak crystal field located at Dq/B ≈ 1, which corresponds to the 4 T 1 ( 4 G) → 6 A 1 ( 6 S) transition in the 490-750-nm range. [11b,12] However, the extremely weak absorption of Mn 2+ in the ultraviolet and visible range results in a particularly low luminescence intensity, thereby making it unsuitable for plantgrowth-related applications. Representative phosphors include Ca 2 Sr(PO 4

Achieving highly thermostable red emission in singly Mn2+-doped BaXP2O7 (X = Mg/Zn) via self-reduction

“…Nowadays, red phosphors are attracting widespread attention for enhancing luminous efficacy in white light-emitting-diodes (WLEDs) for lighting and for artificial red light to promote plant growth. [1][2][3][4][5] The former calls for phosphors with emission maxima within 620-650 nm to compensate for the red region of the commercial WLED. 6,7 The latter needs red-to-deep-red (650-750 nm) emitting materials to meet the absorptions of chlorophylls and phytochromes.…”

Light-Induced Charge Transfer to Achieve Deep-Red Emission in SrSc2O4:Bi toward Multiple Optical Applications

“…Generally, chlorophyll can absorb energy from light and transform it into electronic energy, and chlorophyll is the core of light absorption during the photosynthesis process. 53 Phytochrome is an albumen in plants that mainly absorbs red and deep-red light. Phytochrome can promote plant growth, especially for the seed germination and the growth of stems and leaves.…”

A non-rare earth ion doped broadband emission phosphor located in NIR-II for ethanol concentration detection

“…[8][9][10] Eu 2+ and Mn 2+ ions can have a certain FWHM but their emission positions tend to be located from the deep red region to NIR-I, with emission wavelengths relatively close to the short-wave direction. [11][12][13] Generally, Cr 3+ ions are widely used as near infrared emitting ions due to their tunable emission position; however, the emission spectra of Cr 3+ -doped phosphors have been reported to be mainly located in NIR-I or only a part of the spectra in NIR-II. For example, Shao developed an ultrabroadband Ga 4 GeO 8 :Cr 3+ phosphor with a near-infrared emission range of 700-1300 nm and a tunable emission band with peaks from 835 to 980 nm by varying the Cr 3+ concentration; 14 Li reported a new series of ABO 4 :Cr 3+ (A 3+ = Ga, Sc, In; B 5+ = Ta, Nb) NIR-emitting phosphors.…”