High-Performance NIR Emission in Chromium-Doped Garnet Phosphors Enabled by Structure and Excitation Regulation

The burgeoning phosphor-converted near-infrared light-emitting diodes (pc-NIR LEDs) have important applications in special illumination and spectroscopy analysis. However, the development of efficient NIR-emitting phosphors with high performance is still a challenge. In this work, a chemical unit co-substitution strategy is proposed to realize the excitation transition regulation and successfully achieve high-performance NIR luminescence in Ca3-yNayMg1-ySb2-xAl2+yO12: xCr(3+) (0 <= x <= 0.05, 0 <= y <= 1) garnet-type solid solution phosphors. Through the excitation transition modulation from the (4)A(2) ground state to the T-4(1)(P-4) and T-4(1)(F-4) excitation state, the excitation intensity at the blue light region is largely enhanced by 25.6 times. Moreover, the NIR-emitting efficiency and thermal stability are improved, with the optimal luminescence internal quantum efficiency of 90.6% and thermal stability of 97%@423 K, without any flux-assisted sintering or reduction atmosphere protection. The structure regulation induced small Stokes shift, weak electron-phonon coupling effect, and decreased non-radiative transition are responsible for the excellent NIR-emitting performance. Finally, the NIR pc-LED is fabricated with photoelectric efficiencies of 18.7%@100 mA and NIR output powers of 63 mW@100 mA, presenting potential applications in nondestructive internal defect detection, veins imaging, and night vision surveillance.