Near‐Unity Internal Quantum Efficiency and High Thermal Stability of Sr 3 MgGe 5 O 14 : Cr 3+ Phosphor for Plant Growth

Abstract Near‐infrared phosphor‐converted light‐emitting diodes (NIR pc‐LEDs) are regarded one of the most promising light sources for food analysis, plant growth, bioimaging, night vision, and so on. Cr 3+ ‐activated NIR phosphors have garnered increasing attention due to their exceptional photoluminescence properties for NIR pc‐LED. However, most of them suffer from poor thermal stability or low efficiency which limits their large‐scale application. Herein, a novel Sr 3 MgGe 5 O 14 : Cr 3+ (SMGO: Cr 3+ ) NIR phosphor is presented, which exhibits a broadband NIR emission ranging the range of 650–1000 nm with a peak at 735 nm. SMGO: 0.005Cr 3+ phosphor demonstrates an almost near‐unity internal quantum efficiency (99.4%) and excellent thermal quenching performance ( I 423 K /I 298 K  = 86%). First‐principles theory calculation indicates that Cr 3+ ions preferentially occupy the [Ge2/MgO 4 ] and [Ge3O 4 ] sites at high doping concentration within the SMGO host, illustrating the concentration quenching mechanism. Furthermore, a NIR pc‐LED is manufactured by utilizing SMGO: 0.005Cr 3+ with a 445 nm blue LED chip, and the NIR output power is 140.5 mW with a photoelectric conversion efficiency of 15.5% at 300 mA. Potential applications of plant growth and the detection of several mental ions are also demonstrated, which demostrates its promising application in plant growth.