Near-Unity Internal Quantum Efficiency and High Thermal Stability of Sr3MgGe5O14: Cr3+ Phosphor for Plant Growth

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. Cr³⁺-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 Sr₃MgGe₅O₁₄: Cr³⁺ (SMGO: Cr³⁺) NIR phosphor is presented, which exhibits a broadband NIR emission ranging the range of 650–1000 nm with a peak at 735 nm. SMGO: 0.005Cr³⁺ 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 Cr³⁺ ions preferentially occupy the [Ge2/MgO₄] and [Ge3O₄] sites at high doping concentration within the SMGO host, illustrating the concentration quenching mechanism. Furthermore, a NIR pc-LED is manufactured by utilizing SMGO: 0.005Cr³⁺ 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.