Deep‐Red Ca3Al2Ge3O12:Eu3+ Garnet Phosphor with Near‐Unity Internal Quantum Efficiency and High Thermal Stability for Plant Growth Application

Abstract Trivalent europium (Eu 3+ ) doped phosphors usually radiate orange or red light owing to distinct transitions from the 5 D 0 excited level to the ground states of 7 F 1 and 7 F 2 . However, Eu 3+ activated phosphors with a dominant deep‐red emission due to 5 D 0 → 7 F 4 transition are relatively rare. In this work, the synthesis and photoluminescence properties of Ca 3 Al 2 Ge 3 O 12 :Eu 3+ deep‐red phosphor with an intense 5 D 0 → 7 F 4 transition are reported. Irradiating this new garnet phosphor with 394 nm near‐ultraviolet light generates a dominant deep‐red emission band centered at 707 nm. The phosphor has a high internal quantum efficiency of 98.4% and excellent luminescence thermal stability, maintaining 78.8% of the room temperature emission intensity at 150 °C. Based on the unique spectral feature of this new compound, a phosphor‐converted deep‐red LED prototype device is fabricated, producing an output power of 27.3 mW with a photoelectric conversion efficiency of 4.0% at 200 mA. Plant growth experiments are also conducted to demonstrate the obvious positive effects of the fabricated deep‐red LED on plant growth, further indicating that the as‐prepared Ca 3 Al 2 Ge 3 O 12 :Eu 3+ deep‐red phosphor can act as a promising luminescence converter for plant growth LED bulbs.