Broadband UV-Excitation and Red/Far-Red Emission Materials for Plant Growth: Tunable Spectrum Conversion in Eu³⁺,Mn⁴⁺ Co-doped LaAl_0.7Ga_0.3O₃ Phosphors

Abstract

Broadband ultraviolet (UV) excitation and red/farred emission phosphors can effectively convert solar spectrum to enhance photosynthesis and promote morphogenesis in plants. Based on the above application requirements, Eu 3+ single-doped LaAl 1−y Ga y O 3 solid solutions and Eu 3+ ,Mn 4+ codoped LaAl 0.7 Ga 0.3 O 3 phosphors were designed and synthesized in this work. The LaAl 0.7 Ga 0.3 O 3 :0.05Eu 3+ (LAG:Eu 3+ ) phosphor exhibits a strong charge transfer band (CTB) excitation and characteristic 5 D 0 → 7 F 2 transition red emission (619 nm), which is very similar to the luminescence properties of Eu 3+ -organic ligand compound (EuL 3 ). Rietveld refinement studies further revealed that the cation substitution disturbs the site symmetry. The optimal Eu 3+ , Mn 4+ codoped LaAl 0.7 Ga 0.3 O 3 (LAG:Eu,Mn) phosphor possesses a dualband excitation spectrum in broadband ultraviolet (UVA, UVB) area and a dual-band emission spectrum within red/far-red area. Under the sunlight radiation, the real-time spectrum of luminous laminated glasses fabricated by coating the LAG:Eu,Mn phosphor shows the percentage of radiant intensity in the red/far-red region significantly increases, suggesting that the phosphor can be a promising candidate for solar spectral conversion in plant cultivation. We believe this work provides a new idea for developing novel broadband ultraviolet excitation and red/far-red emission phosphors.

Tunable emission and thermal sensitivity via energy transfer from Bi3+ to Eu3+ in BaY2Al2Ga2GeO12

“…When Eu 3+ is in the center of deviation from the inversion symmetry, the electric dipole transition 5 D 0 → 7 F 2 is predominant. 8 Energy transfer is a method to tune the emissions through the transfer of the excited-state energy from an activator to a sensitizer. Bi 3+ is a typical non-rare earth activator ion with 6s and 6p electrons externally sensitive to the local crystal environment emitting multiple colors from ultraviolet (UV) to red.…”

Sunlight-activated Eu3+-doped CaNaSb2O6F yellow-orange long-persistence luminescence material

“…Even the most famous red PersL phosphor, Y 2 O 2 S:Eu 3+ ,Ti 4+ ,Mg 2+ , still cannot fully meet the needs of practical application due to its high cost and low sensitivity to room light. [13][14][15][16][17][18][19] Thus, it is an ongoing challenge to develop efficient sunlight-activated warm-color persistent luminescence phosphors to fulfill the high demands for a variety of practical applications.…”

A highly efficient UV-to-red-light conversion by LuNbO4:Eu3+ phosphors through exciton-assisted host-activator energy transfer

“…Broadband ultraviolet (UV) excitation and narrow red-emitting phosphors as wavelength-converting materials (WCMs) have attracted significant attention, due to their application in photovoltaic (PV) devices and plant lighting for enhancing the utilization of solar energy. [1][2][3][4] Since most solar cells can work efficiently in the spectral region of 550 nm to 700 nm while exhibiting a poor photoelectric response to the short wavelength light (200-300 nm), the UV-to-red conversion realized by a WCM assembled on solar cells can improve the PV efficiency. 1,4 Similarly, WCMs are also used to filter solar UV light and provide the light for efficient photosynthesis in plant cultivation.…”

“…1,4 Similarly, WCMs are also used to filter solar UV light and provide the light for efficient photosynthesis in plant cultivation. 2,3 Because red light (600-700 nm) can be absorbed by the chlorophyll of land plants to stimulate photosynthesis and UV light (200-400 nm) always exerts negative effects on plant growth, utilizing WCMs under sunlight can strengthen photosynthesis and accelerate biomass production. 2,5 Phosphors doped with trivalent europium (Eu 3+ ) ions are promising candidates for UV-to-red WCMs, since the Eu 3+ ions can emit intense red luminescence based on the 4f-4f transitions as incorporated in a proper ligand field.…”

“…1,4 Similarly, WCMs are also used to filter solar UV light and provide the light for efficient photosynthesis in plant cultivation. 2,3 Because red light (600–700 nm) can be absorbed by the chlorophyll of land plants to stimulate photosynthesis and UV light (200–400 nm) always exerts negative effects on plant growth, utilizing WCMs under sunlight can strengthen photosynthesis and accelerate biomass production. 2,5…”