High‐Performance and High‐Power NlR Light Sources Based on Y ₃ Ga ₅ O ₁₂ : Cr ³⁺ , Yb ³⁺ Ceramics: Luminescence From Macro Statistics to Micro Diagnostics

ABSTRACT High‐power near‐infrared (NIR) phosphor‐converted light‐emitting diodes (pc‐LEDs) are widely utilized in biomedical imaging and night vision. However, their performance is significantly constrained by the conventional phosphor‐in‐organics encapsulants with low thermal conductivity. Herein, an order of magnitude improvement in thermal conductivity is achieved in Y 3 Ga 5 O 12 : Cr 3+ , Yb 3+ (YGG: Cr 3+ , Yb 3+ ) via an inorganic ceramic phosphor (CP) structure. The YGG: Cr 3+ CP exhibits a high external quantum efficiency of 47.5% and excellent thermal stability of 103.3% at 423 K. Furthermore, the Yb 3+ extends the emission into the NIR‐II region and enhances the thermal stability. The energy transfer mechanism from Cr 3+ to Yb 3+ is elucidated in view of a physical perspective, and the Yb 3+ ‐luminescence disparity in macroscale and microscale is identified for the first time. YGG: Cr 3+ and YGG: Cr 3+ , Yb 3+ CPs enable high performances in high‐power NIR LEDs. For the YGG: Cr 3+ , Yb 3+ CP, the power conversion efficiency and output power are 2.8 and 6.9 times higher than those of YGG: Cr 3+ , Yb 3+ phosphors, respectively. The output power driven at 1 A maintains 1.3 W, representing an advanced level of performance. This work presents an efficient encapsulation strategy, paving the way for the development of high‐power NIR LEDs and laser‐diode devices.