Broadband MgGa₂O₄:Cr³⁺ Spinel with High Luminescence Thermal Stability for Near-Infrared Phosphor-Converted Light-Emitting Diodes

Near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) are emerging as promising light sources for applications in nondestructive testing, plant growth enhancement, and night vision. However, designing an NIR phosphor with high emission efficiency, excellent luminescence thermal stability, and a broad emission range remains a significant challenge. In this study, we synthesized MgGa2O4:Cr3+ (MGO-Cr) phosphors using a solid-state reaction. These phosphors emit a broad NIR light ranging from 650 to 1300 nm, with an outstanding full width at half-maximum (FWHM) of 269 nm, indicating their ability to cover a wide emission range. The internal quantum efficiency of the phosphor is 73%, which is indicative of efficient radiative recombination. Furthermore, the phosphors exhibit excellent luminescence thermal stability, with an intensity ratio of I423 K/I298 K = 81%, demonstrating their ability to maintain stable emission at elevated temperatures─an important characteristic for practical device applications. The investigation focuses on the site occupancy of Cr3+ ions within the crystal lattice and explores the relationship between the luminescent centers and emission spectra of Cr3+. This includes an analysis of crystal field strength, photoluminescence excitation and emission spectra, and decay lifetimes, which supports the theoretical calculations. This comprehensive study provides valuable insight into the structural and electronic factors that govern the performance of MgGa2O4:Cr3+ as an NIR phosphor. Additionally, an NIR pc-LED device was fabricated using the synthesized NIR phosphor to demonstrate its potential for practical and spectroscopic applications. These findings highlight the potential of MgGa2O4:Cr3+ phosphors as efficient NIR emitters for pc-LED applications. The excellent emission properties, thermal stability, and successful fabrication of NIR pc-LED devices demonstrate their promising applicability in various fields. This work provides valuable insights into the design of advanced NIR phosphors for next-generation lighting technologies.