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Mn4+-activated red-emitting materials have garnered significant attention as a research focus due to their potential in enhancing plant growth. Nonetheless, the creation of thermally stable and high-efficiency red phosphors poses a major challenge, particularly for commercial use. In this research, we utilized a cationic substitution strategy to refine the Mn4+ doped germanate phosphor. By replacing Mg2+ ions with Sc3+ ions in the Mg14−xScxGe5O24:Mn4+ (MSGO:Mn4+) phosphor, the emission intensity at room temperature was nearly doubled compared to the non-substituted sample. This enhancement is ascribed to the resonance-enhanced emission effect resulting from lattice distortion. The incorporation of Sc3+ ions also led to a marked rise in the internal quantum efficiency, from 65.14% to 91.14%, and an enhancement in the external quantum efficiency from 47.27% to 70.11%. Moreover, Sc3+ doping induced negative thermal quenching, as indicated by the sustained increase in the photoluminescence intensity of the Mg14−xScxGe5O24:Mn4+ phosphor from 25.1 °C to 225.1 °C, which can be attributed to the introduction of defect energy levels. Ultimately, the optimized Mg13.75Sc0.25Ge5O24:0.01Mn4+ phosphor was integrated with a blue LED chip to create an LED device, showcasing its application potential in the field of plant lighting. [ABSTRACT FROM AUTHOR]

Far‐red phosphor‐converted light‐emitting diodes are receiving increasing attention as an essential component of the next‐generation plant‐growth lights. However, developing far‐red phosphors with high quantum efficiency, low thermal quenching, and suitable emitting wavelength is crucial and urgent. Herein, a new far‐red phosphor BaY2Ga3.9GeO12:0.1Cr3+ with high internal quantum efficiency (98%) and thermal stability (90.2%@423K) is obtained via the substitution of CaO8 with bigger BaO8 dodecahedrons, which is attributed to variations in the lattice environment of Cr3+. Meanwhile, controllable emission tuning from 780 to 708 nm and enhanced luminescence performance are achieved due to the cation substitution can reduce the production of Cr4+ and modulate the lattice occupancy of the Cr3+ ions, and the enhancement of metal‐ligand interactions resulting in the enhancement of the crystal field and the breaking of the forbidden d‐d transition of Cr3+. The proof‐of‐concept demonstration of the pakchoi lighting experiment reveals the great potential of BaY2Ga3.9GeO12:Cr3+ phosphor in stimulating plant growth and pushing the yield. These results demonstrate the feasibility of cationic substitution to optimize the optical performance of Cr3+‐doped phosphors, providing an alternative strategy for designing efficient far‐red light sources for plant lighting. [ABSTRACT FROM AUTHOR]

Far‐red (FR) region (beyond 700 nm) lighting sources possess special potential for plant lighting. However, it remains a challenge to obtain high‐performance Cr3+‐doped FR phosphors. This study developed a FR phosphor, Ca1.8Mg1.2Al2Ge3O12:Cr3+ (CMAGG: Cr3+), using the cation substitution strategy. Under 438 nm blue light excitation, the phosphors display FR emission centered at 720 nm with a full width at half maximum (FWHM) of 91 nm. Benefit from the favorable match with the FR phytochrome (Pfr), the phosphor is combined with InGaN blue light chips to create a FR phosphor‐converted light‐emitting diode (pc‐LED), which is used in Italian lettuce growth experiments and it results shown in a 15% increase in fresh weight and a 6.5% increase in dry weight. Notably, supplemental FR light modulated its growth morphology. The results of this study will be useful for further research on novel Cr3+‐doped FR phosphors to meet the precise spectral requirements for plant growth. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]