The near-infrared (NIR) light source is desirable for realtime nondestructive examination applications, which include the analysis of foodstuffs, health monitoring, iris recognition, and infrared cameras. The emission spectra of such an infrared light source should also be as broad as possible for effective performance, in view of the fact that the broad absorption and reflection of light by the organic elements present in foodstuffs and human health fall in the blue and NIR regions of the electromagnetic spectrum, respectively. In this letter, a blue light-emitting diode (LED) excitable super broadband NIR phosphor light source is developed with a high fwhm of 330 nm and radiant flux of 18.2 mW for the first time. The observation of superbroad-band luminescence from two distinct luminescence centers is studied and evidenced by electron paramagnetic resonance, X-ray absorption near-edge structure, steady-state luminescence, and timeresolved luminescence at ambient and high-pressure environments. Finally, the luminescence mechanism is discussed with the relevant configurational coordinate diagrams.

Red phosphors AMF6:Mn(4+) (A = Na, K, Cs, Ba, Rb; M = Si, Ti, Ge) have been widely studied due to the narrow red emission bands around 630 nm. The different emission of the zero-phonon line (ZPL) may affect the color rendering index of white light-emitting diodes (WLED). The primary reason behind the emergence and intensity of ZPL, taking KNaSiF6:Mn(4+) as an example, was investigated here. The effects of pressure on crystal structure and luminescence were determined experimentally and theoretically. The increase of band gap, red shift of emission spectrum and blue shift of excitation spectrum were observed with higher applied pressure. The angles of ∠FMnF and ∠FMF(M = Si, Ti, Ge) were found clearly distorted from 180° in MF6(2-) octahedron with strong ZPL intensity. The larger distorted SiF6(2-) octahedron, the stronger ZPL intensity. This research provides a new perspective to address the ZPL intensity problem of the hexafluorosilicate phosphors caused by crystal distortion and pressure-dependence of the luminescence. The efficacy of the device featuring from Y3Al5O12:Ce(3+) (YAG) and KNaSiF6:Mn(4+) phosphor was 118 lm/W with the color temperature of 3455 K. These results reveal that KNaSiF6:Mn(4+) presents good luminescent properties and could be a potential candidate material for application in back-lighting systems.

Recently, infrared (IR) light-emitting diodes (LEDs) have attracted considerable interest in the research field worldwide. IR phosphors, the basic materials utilized in LEDs, have become a research hotspot as well. Here, we introduce the high-quantum-efficiency IR ScBO 3 :Cr 3+ phosphor, which provides a spectral range of emission from 700 to 1000 nm with a peak maximum at 800 nm. Electron paramagnetic resonance spectroscopy, with high element selectivity, was used to elucidate the unusual small peak in the photoluminescence spectrum. Phonon structure and electron−lattice interaction were well observed and discussed via temperature-dependent measurements. Moreover, the high quantum efficiency of 72.8% was achieved. To evaluate their potential practical application, phosphor-converted LED packages were designed, which revealed high stability and high output power of 39.11 mW. Furthermore, the fabricated IR LED demonstrated a remarkable ability to penetrate biological tissues. This study provides insights into the luminescent properties and the practical applications of IR LEDs.

We aim to conduct a complete study on the unexpected structure evolution behavior in Cr 3+ -doped phosphors. A series of Ga 2−x Sc x O 3 :Cr 3+ phosphors are successfully synthesized and confirmed through structural studies, while the lattice parameters change unexpectedly. The unique partial substitution (∼87%) of Sc 3+ in the octahedral site is demonstrated via Rietveld refinement. Therefore, the bond valence sum calculation explains the reason for this particular Sc 3+ concentration. The photoluminescent bandwidth and electron−lattice coupling energy initially increase and then decrease, implying an inhomogeneous broadening effect. Time-resolved spectra and electron paramagnetic resonance are utilized to further examine the subtle change in the microstructures and the second coordination sphere effect of Cr 3+ . Ga 1.594 Sc 0.4 O 3 :0.006Cr 3+ exhibits high internal quantum efficiency (99%) and high phosphor-converted light-emitting diode output power (66.09 mW), demonstrating its capability as an outstanding infrared phosphor. This work will motivate further research on unexpected partial substitution during the solid solution process.

The increasing interest in the development of ratiometric optical thermal sensors has led to a wide variety of new systems with promising properties. Among them, singly-doped ratiometric thermometers were recently demonstrated to be particularly reliable. With the aim to discuss the development of an ideal optical thermal sensor, a combined experimental and theoretical insight into the spectroscopy of the Bi2Ga4O9:Cr3+ system is reported showing the importance of an insightful analysis in a wide temperature range. Low-temperature photoluminescence analysis (from 10 K) and the temperature dependence of the lifetime investigation, together with the crystal field analysis and the modeling of the thermal quenching process, allow the estimation of key parameters such as the Debye temperature (cutoff frequency), the Huang–Rhys parameter, and the energy barrier between 2Eg and 4T2g. Additionally, by considering the reliable class of singly-doped ratiometric thermometers based on a couple of excited states obeying the Boltzmann law, the important role played by the absolute sensitivity was discussed and the great potential of Cr3+ singly-activated systems was demonstrated. The results may provide new guidelines for the design of reliable optical thermometers with outstanding and robust performances.