Achieving High Quantum Efficiency Broadband NIR Mg4Ta2O9:Cr3+ Phosphor Through Lithium‐Ion Compensation

Abstract Ultra‐efficient broadband near‐infrared (NIR) phosphor‐converted light‐emitting diodes (pc‐LEDs) are urgently needed to improve the detection sensitivity and spatial resolution of current smart NIR spectroscopy‐based techniques. Nonetheless, the performance of NIR pc‐LED has severely limited owing to the external quantum efficiency (EQE) bottleneck of NIR light‐emitting materials. Herein, a blue LED excitable Cr 3+ ‐doped tetramagnesium ditantalate (Mg 4 Ta 2 O 9 , MT) phosphor is advantageously modified through lithium ion as a key efficient broadband NIR emitter to achieve high optical output power of the NIR light source. The emission spectrum encompasses the 700–1300 nm electromagnetic spectrum of first biological window (λ max = 842 nm) with a full‐width at half‐maximum (FWHM) of ≈2280 cm −1 (≈167 nm), and achieves a record EQE of 61.25% detected at 450 nm excitation through Li‐ion compensation. A prototype NIR pc‐LED is fabricated with MT:Cr 3+ , Li + to evaluate its potential practical application, which reveals an NIR output power of 53.22 mW at a driving current of 100 mA, and a photoelectric conversion efficiency of 25.09% at 10 mA. This work provides an ultra‐efficient broadband NIR luminescent material, which shows great promise in practical applications and presents a novel option for the next‐generation high‐power compact NIR light sources.