Highly Quantum Efficient and Thermally Stable Near‐Infrared‐Emitting K‐β‐Al2O3:Cr3+ Phosphor

Abstract Near‐infrared (NIR) phosphors are enablers for NIR phosphor‐converted light‐emitting diodes (pc‐LEDs). However, fewer NIR‐emitting phosphors with both high internal/external quantum efficiency (IQE/EQE) and thermal stability are discovered, which obstructs the promotion of NIR pc‐LEDs. Herein, by partially replacing Al 3+ in K‐β‐Al 2 O 3 :2Cr 3+ with Ga 3+ , the photoluminescence (PL) intensity of the solid solution K 1+δ (Al 0.4 Ga 0.6 ) 11 O 17 :2Cr 3+ , (KA 0.4 G 0.6 O:Cr) phosphor is increased 2.75 and 1.25 times that of end‐members K 1+δ Al 11 O 17 :2Cr 3+ (KAO:Cr) and K 1+δ Ga 11 O 17 :2Cr 3+ (KGO:Cr). The IQE/EQE of optimal KA 0.4 G 0.6 O:Cr reaches 88.9%/50.8% with high thermal stability (77.4%@150 °C). The PL intensity enhancement is due to the Al/Ga‐6O octahedral volume and distortion variation caused by the substitution of Ga 3+ for Al 3+ in K 1+δ (Al 1‐y ,Ga y ) 11 O 17 :2Cr 3+ (KA 1‐y G y O:Cr), which leads to the forbidden d–d transition being broken and crystal field strength varied. Finally, a NIR pc‐LED device fabricated based on KA 0.4 G 0.6 O:Cr NIR‐emitting phosphor and blue chip reaches an electro‐optical efficiency of 16.3% under a drive current of 100 mA. Meanwhile, non‐destructive detection and plant germination applications of the NIR pc‐LED are demonstrated. These results prove that KA 0.4 G 0.6 O:Cr is a promising NIR phosphor for diverse applications.