Simultaneous Luminescence Color Tuning and Spectral Broadening of Cr³⁺ Near-Infrared Emission for Night Vision Application

Near-infrared (NIR) light serves a key role in many potential applications such as food analysis, biomedical devices, night vision, and so on. As an important component of NIR phosphor-converted light-emitting diodes (pc-LEDs), the adjustment of emission peak position and spectral width of Cr3+-doped phosphors is still considered to be a crucial challenge. Herein, the two emissions at 740 nm from [Cr1O6] and 830 nm from [Cr2O4] were realized to broaden the emission band in the Al2.26Ge0.74O4.87:Cr3+ (AGO:Cr3+) phosphor. Moreover, with increasing Cr3+-doped concentration, the crystal field strength decreases and energy transfer from [Cr1O6] to [Cr2O4] is enhanced. The emission peak originating from [Cr2O4] gradually becomes dominant, resulting in a spectral red shift and broadening. The optimized AGO:0.7% Cr3+ phosphor shows remarkable thermal stability, of which the integrated intensity at 373 K keeps 86% of the initial intensity at 298 K. Under 405 nm excitation, the internal quantum efficiency could reach 70% and the external quantum efficiency was measured to be 23%. The application of night vision can be implemented based on the AGO:Cr3+-fabricated NIR pc-LED. This work achieves simultaneous modulation of luminescence color and spectral width by controlling the Cr3+-doped concentration, which provides a feasible strategy for NIR emission adjustment.