High-Output-Power Broadband Near-Infrared Phosphor Suitable for Various LED Applications.

Abstract

The preparation of broadband near-infrared phosphors has emerged as a frontier research area, presenting significant scientific importance alongside considerable technical challenges. Cr³⁺-doped garnet-type near-infrared phosphors have garnered widespread attention due to their ability to be excited by inexpensive blue chips. However, existing phosphors suffer from drawbacks such as narrow full width at half-maximum and short emission wavelengths. This study employs a high-temperature solid-state method to synthesize a garnet-type phosphor, La₃In₂Ga₃O₁₂:Cr³⁺. XRD patterns confirm that the sample exhibits a garnet structure with the space group Ia<math xmlns="http://www.w3.org/1998/Math/MathML"><mover><mn>3</mn><mo>¯</mo></mover></math>d. Excited at 490 nm, this phosphor exhibits strong emission within the 700-1000 nm range, with an emission peak at 826 nm and full width at half-maximum of 149 nm. This study employed a fluxing agent strategy to enhance crystallinity, thereby improving the phosphor in luminescence and ultimately identifying H₃BO₃ as the optimal fluxing agent. Monitoring the luminescence intensity at various temperatures revealed that at 423 K, the intensity remained at 50% of the initial value, yielding an activation energy of 0.340 eV. Finally, by fabricating the phosphor with a blue 485 nm LED chip into a near-infrared LED device, a luminous efficiency of 9.72%@20 mA was achieved, with an output power reaching 978 mW@320 mA. This device demonstrates promising applications in night vision security screening, information recognition, and biological imaging.