Zero-Disturbance Sensitization Strategy for Ultra-High-Efficiency Cr³⁺ Near-Infrared Phosphors

High-efficiency near-infrared (NIR) phosphors are essential for NIR phosphor-converted light-emitting diodes (pc-LEDs). Cr³⁺-activated garnet-type materials have emerged as promising candidates in this regard. In this work, we propose a minimal-disturbance sensitization strategy to enhance the luminescence performance of Cr³⁺-doped Ca₂Gd₂Ga₂Ge₂O₁₂ (CGGGO) NIR phosphors by introducing Tb³⁺ as an energy-transfer mediator. The co-doping of Tb³⁺ has been demonstrated to enhance the emission intensity by 28% under 260 nm excitation and 14% under 450 nm excitation. Concurrently, the internal quantum efficiency (IQE) has been shown to improve from 86.5% to 97%. It is important to note that the emission peak position, spectral shape and fluorescence lifetime remain almost unchanged (peak shift < 1 nm, lifetime variation < 3%), thus confirming the weakly perturbing nature of the sensitization. The present study proposes a dual-pathway energy transfer mechanism, and crystal-field analysis confirms the presence of a moderate crystal field around Cr³⁺ that is favorable for broadband NIR emission. In conclusion, the fabrication of an NIR pc-LED device employing the optimal co-doped phosphor has been demonstrated to yield stable electroluminescence and excellent night-vision imaging performance. This work develops a high-performance Cr³⁺-activated NIR phosphor and provides a general strategy for designing efficient luminescent materials via minimally invasive co-doping.