Highly Efficient and Stable Broadband NIR Phosphor Gd ₃ MgGeGa ₃ O ₁₂ :Cr ³⁺ for Advanced pc‐LEDs Applications

Abstract The development of broadband near‐infrared (NIR) phosphors is essential for the advancement of intelligent NIR phosphor‐converted light‐emitting diodes (pc‐LEDs) as light sources in the next generation. In this work, a series of Cr ³⁺ ‐activated high‐efficiency broadband NIR phosphors are synthesized through [Mg ²⁺ –Ge ⁴⁺ ] co‐substitution in Gd ₃ Mg _x Al _2‐2x Ge _x Ga ₃ O ₁₂ :Cr ³⁺ . The substitution of [Mg ²⁺ –Ge ⁴⁺ ] leads to a decrease in crystal field intensity and a redshift of the emission peak from 716 to 792 nm, along with an uneven distribution of the crystal field and an increase in full width at half‐maximum (FWHM) from 88 to 156 nm. Moreover, the luminescence intensity remains essentially unchanged with the redshift of the emission spectrum. Through concentration optimization, the substituted endpoint Gd ₃ MgGeGa ₃ O ₁₂ :0.07Cr ³⁺ exhibits a longer emission wavelength (805 nm) with excellent internal (IQE = 90%) and external quantum efficiencies (EQE = 33%), while maintaining 76% of its luminescence intensity at 400 K compared to 300 K. The prepared NIR pc‐LED (Gd ₃ MgGeGa ₃ O ₁₂ :0.07Cr ³⁺ ) has a photoelectric conversion efficiency of up to 21% at 25 mA, effectively demonstrating the practical application of the prepared phosphors in night vision, non‐destructive testing, rapid recognition, and other related fields.