Efficient Ultra-Broadband Ga4GeO8:Cr3+ Phosphors with Tunable Peak Wavelengths from 835 to 980 nm for NIR pc-LED Application

Near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) hold great potential for applications ranging from night vision to non-destructive detection. However, it remains a long-standing challenge to develop NIR phosphors simultaneously with longer-wavelength broadband emissions and higher efficiency. Herein, ultra-broadband Ga 4 GeO 8 :Cr 3+ (GGO:Cr 3+ ) phosphors are developed, with the NIR emission covering 700–1300 nm. Furthermore, tunable emission bands peaking from 835 to 980 nm are achieved simply by varying the Cr 3+ concentration. Particularly, emission maxima (λ max ) of GGO: x Cr 3+ shift from 850 to 900 nm without intensity loss when increasing x values between 0.02 and 0.10. An internal quantum yield of 60% is achieved for GGO:0.02Cr 3+ (λ max ≈ 850 nm, full width at half maximum (FWHM) ≈215 nm). The origin of tunable ultra-broadband emissions of GGO:Cr 3+ is revealed on the basis of structural and time-resolved spectroscopic analysis. The pc-LED fabricated by GGO:0.02Cr 3+ exhibits a maximum NIR output power of ≈56 mW at 400 mA drive current, and its application in high-penetration quality analysis of fruits is also demonstrated. The results indicate that GGO:Cr 3+ phosphors have high promise for practical applications in NIR pc-LED devices.