High‐Efficiency Near‐Infrared Forsterite Mg 2 SiO 4 : Cr 3+ , Yb 3+ Phosphor for Optical Bioimaging and Night Vision Applications

ABSTRACT The advancement of near‐infrared phosphor‐converted light‐emitting diodes (NIR pc‐LEDs) for next‐generation optoelectronic applications is critically dependent on the availability of high‐performance phosphors. In this study, a series of NIR‐emitting phosphors with high luminescence efficiency and excellent stability was developed by co‐doping Cr 3+ , Yb 3+ into the Mg 2 SiO 4 (MSO) host. Efficient energy transfer from Cr 3+ to Yb 3+ was achieved in the MSO: Cr 3+ , 2.5%Yb 3+ phosphor, reaching an energy transfer efficiency of 91.82%, as determined from the luminescence intensity measurement. The optimal MSO: Cr 3+ , 1.5%Yb 3+ phosphor exhibits a remarkable internal quantum efficiency (IQE) of 71.8% and an external quantum efficiency (EQE) of 48.8%. It also demonstrates remarkable thermal stability, retaining 71.5% of its initial intensity at 423 K. Additionally, the material shows exceptional humidity resistance, retaining approximately 98.05% of its initial intensity after 7 days of exposure to harsh conditions (85°C and 85% relative humidity, RH). Notably, no significant chromaticity shift is observed at elevated temperatures, indicating excellent color stability. Finally, an NIR pc‐LED was fabricated by combining the optimized phosphor with a 450 nm commercial blue LED chip. The device delivers a high output power of 718.67 mW with an electro‐optical conversion efficiency of 12.53% at a driving current of 600 mA. Collectively, these results underscore the promising potential of this phosphor for applications in optical bioimaging and night vision.