Ultra-broad Near-Infrared Emitting Phosphor LiInF4: Cr3+ with Extremely Weak Crystal Field.

Recent decades have witnessed a major development in broadband near-infrared (NIR)-emitting phosphors because of their potential applications in real-time nondestructive examination. These applications require the emission spectra of phosphors to be as broad as possible for efficient performance. Therefore, a blue-light excited LiInF4: Cr3+ phosphor with a NIR emission covering 700-1400 nm is successfully synthesized. Under 470 nm excitation, it shows broadband emission peaked at 980 nm with the full-width at half maximum of 210 nm. The structure and crystal field environment are investigated in detail, and the LiInF4: Cr3+ possesses a weak crystal field strength and strong electron-phonon coupling. An efficient NIR phosphor-converted light-emitting diode (pc-LED) is fabricated by the prepared LiInF4: Cr3+ phosphor and commercial blue diode chip, generating a NIR radiant flux of 5.54 mW at 150 mA drive current. Finally, the NIR pc-LED is successfully applied to identify the blood vessel distribution of the hand. This work suggests the potential of LiInF4: Cr3+ phosphor in applications.

A new broadband near-infrared emitting Mg2Al4Si5O18:Cr3+ phosphor for night-vision imaging.

Phosphor-converted light-emitting diodes (pc-LEDs) have important applications in security surveillance and food testing. However, developing new broadband near-infrared phosphors remains an important issue. Herein, the high-temperature solid-state reaction method was applied to synthesize a new type of Cr3+ doped Mg2Al4Si5O18 broadband NIR phosphor which matches a blue LED chip. It exhibits a broadband near-infrared (NIR) phosphor emission with a focus of 856 nm and a full width at half maximum >200 nm after excitation at 453 nm. The optimum concentration of Cr3+ was established to contain 2 mol%. At 398 K, the luminescence intensity is 45.2% of that at 298 K. The power output of NIR pc-LEDs fabricated by incorporating a 450 nm chip and the Mg2Al4Si5O18:0.02 Cr3+ phosphor is 19.69 mW at 300 mA current. Finally, the developed NIR pc-LED shows significant potential for use in night-vision imaging.

A novel Cr3+-doped Lu2CaMg2Si3O12 garnet phosphor with broadband emission for near-infrared applications.

Near-infrared (NIR) phosphor-converted light emitting diode (pc-LED) light sources have broad application prospects in environmental science, biomedical and plant growth fields. However, NIR phosphors still suffer from narrowband emission and low thermal stability. Here, we prepared a novel Lu2CaMg2-xSi3O12:xCr3+ (LCMS:xCr3+, x = 0.005-0.06) phosphor with broadband emission by a high-temperature solid state reaction. Under excitation at 450 nm, the emission spectrum of the LCMS:0.05Cr3+ phosphor shows a broadband emission in the range of 650-1000 nm with a large full width at half maximum (FWHM) of 125 nm and an R-line emission of 692 nm. In addition, the LCMS:0.05Cr3+ phosphor has good thermal stability and can maintain 70% emission intensity at 150 °C relative to that at room temperature. The LCMS:0.05Cr3+ phosphor exhibits a high internal quantum efficiency (IQE) of ∼76%. Using this phosphor, a NIR pc-LED with photoelectric efficiencies of 14.8% at 100 mA and 6.0% at 320 mA and NIR output powers of 59.5 mW at 100 mA and 181.0 mW at 320 mA was obtained. The broadband LCMS:0.05Cr3+ phosphor with a NIR emission peaked at 750 nm can serve as a light source for plant cultivation and has superior application prospects in the agriculture field.