Novel Cr³⁺‐Doped Garnet Phosphor with Broadband Efficient Far‐Red Emission for Photochrome Matching Plant‐Lighting

Abstract

Cr3+‐doped phosphors are highly recognized in various fields for their remarkable luminous efficiency and spectral flexibility, including modern agriculture and horticulture. However, the shortage of suitable Cr3+‐doped phosphors for far‐red LED devices has inhibited their popularization in plant lighting. Herein, an innovative Cr3+‐doped phosphor Ca2YAl3Ge2O12:Cr3+ (CYAG:Cr3+), achieving a broad far‐red emission at 770 nm upon 450 nm blue light excitation is designed. The optimal CYAG:Cr3+ phosphor exhibits a high internal quantum yield of 78.2% and low thermal‐quenching behavior of 85%@373 K. Thus, the fabricated phosphor‐converted LEDs (pc‐LEDs) for plant far‐red lighting have a high output power of 33.3 mW and photovoltaic conversion efficiency of 11.5% at 100 mA. The potential of CYAG:Cr3+ in plant lighting is assessed by supplementing the far‐red lighting of Italian lettuce with fabricated pc‐LEDs, and the biomass of Italian lettuce is significantly increased by 33%. The successful development of CYAG:Cr3+ phosphors provides a high‐quality option for plant far‐red light devices and further stimulates the development of new Cr3+‐doped plant‐lighting phosphors.

Highly‐Efficiency Far‐Red Emission in Cr3+ Activated Ca1.8Mg1.2Al2Ge3O12 toward Plant Precise Lighting

“…[11] Consequently, Cr 3+ -activated phosphors are well-suited for commercial blue LED chips and they match the absorption spectrum of P fr in plants. They were an ideal far-red phosphor for plantgrowth LED lamps, and Cr 3+ far-red phosphors for plant growth have been widely studied, such as Gd 2.4 Lu 0.6 Ga 4 AlO 12 :Cr 3+ (𝜆 em = 728 nm), [12] Sr 3 Al 10 SiO 20 :Cr 3+ (emission peak position adjustable from 695-780 nm), [13] Gd 3 Y x In x Ga 5-2x O 12 :Cr 3+ (𝜆 em = 760 nm), [14] NaSbF 4 :Cr 3+ (𝜆 em = 760 nm), [15] ZnGa 2 O 4 : Cr 3+ (𝜆 em = 710 nm), [16] Ca 2 YAl 3 Ge 2 O 12 : Cr 3+ (𝜆 em = 770 nm) [17] etc.…”

Crystal Field-Engineered Cr3+-Doped Gd3(MgxGa5–2xGex)O12 Phosphors for Near-Infrared LEDs and X-ray Imaging Applications

“…The A 3 B 2 C 3 O 12 garnet-structured compound has garnered significant attention for its unique luminescence tunability. , The manipulation of crystal field engineering, achieved through mono- or disubstituting the cations within the garnet-structured host, has the capacity to diminish its symmetry and consequently adjust the crystal field intensity. Ultimately, this affects the Cr 3+ luminescence, making it emerge as the most potent approach for boosting the NIR performance. , Furthermore, the strategy of crystal field engineering has the potential to mitigate the electron–phonon coupling (EPC) process, thereby enhancing its structural rigidity and improving the thermal stability . For example, for substituting Ga 3+ with Al 3+ in Gd 3 Ga 5– x Al x O 12 :Cr 3+ , it has to facilitate the advancement of NIR phosphor-converted LED (pc-LED) devices, culminating in an impressive efficiency of 26% (at 100 mA) .…”

“…19,20 Furthermore, the strategy of crystal field engineering has the potential to mitigate the electron− phonon coupling (EPC) process, thereby enhancing its structural rigidity and improving the thermal stability. 21 For e x a m p l e , f o r s u b s t i t u t i n g G a 3 + w i t h A l 3 + i n Gd 3 Ga 5−x Al x O 12 :Cr 3+ , it has to facilitate the advancement of NIR phosphor-converted LED (pc-LED) devices, culminating in an impressive efficiency of 26% (at 100 mA). 22 The T h i s c o n t e n t i s Cr 3+ results in a broadening of the fwhm from 105 to 211 nm, realizing a wider range and a higher precision of food detection.…”