Cr3+-doped infrared phosphors are promising candidates for next-generation phosphor-converted infrared light-emitting diodes (LEDs) because they can, in principle, tune and convert the luminescence spectra from an LED chip. However, most studies focus on broad-band Cr3+-doped phosphors, and the control mechanism of Cr3+-doped phosphors with sharp line emissions remains ambiguous. Here, we report LiGa5(1–x)Al5x O8:Cr3+ phosphors with sharp line emissions. The luminescence analysis reveals the subtle change of the local structure around Cr3+, which cannot be well resolved by X-ray diffraction. The deviation between the temperature-dependent photoluminescence and decay profile is introduced as well. Furthermore, the morphologies of LiGa5(1–x)Al5x O8:Cr3+ phosphors with high aluminum concentration demonstrate their great potential for mini-LED applications. Finally, an LED package is constructed, and it reveals the potential for angiographic applications. This study opens up a new understanding and perspective for Cr3+-doped sharp emission phosphors and reveals their potential for LED applications.

Infrared luminescent materials have evoked much attention from chemists and material scientists. Although substantial progress is made in materials design, the luminescent mechanism remains ambiguous in the complex structures, presenting major barriers to developing novel infrared luminescent materials. Herein, this study aims to deliberate a complete discussion on infrared phosphors with concentration-induced hetero-valent partial-inverse occupation. High-resolution synchrotron X-ray diffraction and Raman spectroscopy reveal the subtle structural change in LiGa 5(1−x) O 8 :5xCr 3+ . Besides, Cr K-edge wavelet analysis and extended X-ray absorption fine structure illustrate the impact of Cr in the second shell of another Cr ion and the practical coordination of Ga and Cr ions. Furthermore, unexpected two-center Cr 3+ emissions and the Cr-Cr pair emission are observed at high Cr concentrations. Variation between the zero-phonon line and N-line at different temperatures is demonstrated. Finally, the structural and luminescent properties are comprehensively discussed, providing the origin of the unexpected Cr2 emission. This study not only provides insight into the hetero-valent partial-inverse occupation process in inorganic materials but also sheds light on developing novel infrared luminescent materials.

According to the latest literature, it is difficult to measure the multiple important physical parameters inside a proton battery stack accurately and simultaneously. The present bottleneck is external or single measurements, and the multiple important physical parameters (oxygen, clamping pressure, hydrogen, voltage, current, temperature, flow, and humidity) are interrelated, and have a significant impact on the performance, life, and safety of the proton battery stack. Therefore, this study used micro-electro-mechanical systems (MEMS) technology to develop a micro oxygen sensor and a micro clamping pressure sensor, which were integrated into the 6-in-1 microsensor developed by this research team. In order to improve the output and operability of microsensors, an incremental mask was redesigned to integrate the back end of the microsensor in combination with a flexible printed circuit. Consequently, a flexible 8-in-1 (oxygen, clamping pressure, hydrogen, voltage, current, temperature, flow, and humidity) microsensor was developed and embedded in a proton battery stack for real-time microscopic measurement. Multiple micro-electro-mechanical systems technologies were used many times in the process of developing the flexible 8-in-1 microsensor in this study, including physical vapor deposition (PVD), lithography, lift-off, and wet etching. The substrate was a 50 μm-thick polyimide (PI) film, characterized by good tensile strength, high temperature resistance, and chemical resistance. The microsensor electrode used Au as the main electrode and Ti as the adhesion layer.