Wearable biosensing and food safety inspection devices with high thermal stability, high brightness, and broad near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) could accelerate the next-generation NIR light applications. In this work, NIR La 3−x Gd x Ga 5 GeO 14 :Cr 3+ (x = 0 to 1.5) phosphors were successfully fabricated by a high-temperature solid-state method. Here, by doping Gd 3+ ions into the La 3+ sites in the La 3 Ga 5 GeO 14 matrix, a 7.9-fold increase in the photoluminescence (PL) intensity of the Cr 3+ ions, as well as a remarkably broadened full width at half-maximum (FWHM) of the corresponding PL spectra, is achieved. The enhancements in the PL, PLE intensity, and FWHM are attributed to the suppression of the nonradiative transition process of Cr 3+ when Gd 3+ ions are doped into the host, which can be demonstrated by the decay curves. Moreover, the La 1.5 Gd 1.5 Ga 5 GeO 14 :Cr 3+ phosphor displays an abnormally negative thermal phenomenon that the integral PL intensity reaches 131% of the initial intensity when the ambient temperature increases to 160 °C. Finally, the broadband NIR pc-LED was fabricated based on the as-explored La 1.5 Gd 1.5 Ga 5 GeO 14 :Cr 3+ phosphors combined with a 460 nm chip, and the potential applications for the broadband NIR pc-LEDs were discussed in detail.

Sm 3+ , Mn 4+ co-activated LaGaO 3 phosphors, giving the characteristic emissions of orange and red emission simultaneously, were prepared by a solid-state reaction. Their luminescence properties, energy transfer behavior, thermal stability, and ratiometric temperature sensing performance were investigated. Thanks to the inhibition of energy transfer between Sm 3+ and Mn 4+ ions at high temperature and the reconstruction of the traps, the distinct optical behavior of the involved activators dependent on the ambient temperature was evaluated. Antithermal quenching performance of Sm 3+ ions along with the emission declination of Mn 4+ ions was observed. Hence, the optical thermometry characteristics of the resultant phosphor based on the fluorescent intensity ratio (orange/red) realize a recorded temperature sensitivity of 4.19% K −1 and 2.09% K −1 . Moreover, the as-explored film combined with the LaGaO 3 : Sm 3+ , Mn 4+ phosphor is demonstrated to be a promising multi-color optical thermometer.

In this work, a tunable luminescence color from yellow to orange of photoluminescence (PL), long persistent luminescence (LPL), and photostimulated luminescence (PSL) is successfully achieved in BaGa2O4:Bi3+ phosphors with the introduction of Sr2+ ions as secondary cations. It is confirmed that broad-band emissions located at 500 and 600 nm originate from the occupation of Bi3+ ions at different lattice sites in the BaGa2O4 host matrix. The replacement of Sr2+ for Ba2+ ions makes the emission red-shift from 600 to 650 nm; moreover, two additional emissions appeare at 743 and 810 nm due to the occupational preference of Bi3+ ions at Ga3+ sites. Furthermore, the doped Sr2+ ions promote the reconstruction of the trapping centers, which conduces to the fundamental improvement of the optical storage capacity behavior of Bi3+-doped phosphors. Our results clarify the dependence of the luminescence performance on the crystal sites of Bi3+ ions with fascinating broad-band emissions in the BaGa2O4:0.01Bi3+ host matrix and will benefit the design and exploration of Bi3+-doped solid solutions for optical storage applications.

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