Broadband near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) are essential to integrate near-infrared spectrometers into mobile devices for the rapid and noninvasive detection of biological components. However, efficient broadband NIR phosphors with a peak emission wavelength longer than 800 nm are deficient. In this study, CaMgGe2O6:Cr3+ phosphor was prepared by a high-temperature solid-state reaction. The phosphor doped with 0.02Cr3+ showed an emission band at 845 nm with a broad bandwidth of 160 nm and a high quantum yield of 84% under 450 nm excitation. The broadband NIR pc-LED was fabricated using CaMgGe2O6:0.02Cr3+ phosphor based on a blue light-emitting diode (LED) chip. A photoelectric efficiency of 27.2% @ 10 mA and an NIR output power of 57.98 mW @ 100 mA were achieved, which are the highest values reported yet for broadband NIR pc-LEDs with a peak wavelength longer than 800 nm. Using the fabricated NIR pc-LED as the light source, the characteristic absorption spectra of some substances were obtained. All of the results indicated that the CaMgGe2O6:Cr3+ phosphor has considerable potential in near-infrared spectroscopic applications.
Ultraviolet‐C illumination may provide a promising solution for the disinfection technology, and thus the development of novel type of ultraviolet‐C light sources is continuously expected. Herein, a conceptual design of ultraviolet‐C light source based on up‐conversion luminescence of phosphor material is introduced. Accordingly, a composite film is prepared using YBO3:Pr3+ phosphor and a transmissive remote phosphor‐converted light source is built by combing the phosphor film with a 447 nm laser. Spectral measurements show that the phosphor‐converted design emits ultraviolet‐C light peaking at 263 and 274 nm with tunable emission intensities. Moreover, ultraviolet imaging demonstration implies that the present design has a potential to serve as an ultraviolet‐C germicidal light source for surface decontamination.
In conventional electron trapping optical storage phosphor, both short‐ and long‐wavelength light are needed for information write‐in and read‐out, respectively, complicating the optical storage system. Here, a Y3Al2Ga3O12:Pr3+,Eu3+ optical storage phosphor with Pr3+ as an electron donor and Eu3+ as an electron trap is designed, and a single wavelength write‐read scheme is demonstrated, which employs the same blue laser diode (LD) light source for both optical write‐in through two‐photon up‐conversion charging and for read‐out based on photostimulated luminescence (PSL), originated from 4f15d1→4f2 transition of Pr3+ peaked at 315 nm in UV region. A deep electron trap with the mean depth of 1.42 eV and a narrow distribution of 0.3 eV is observed in the presence of Eu3+ in Y3Al2Ga3O12:Pr3+, implying its long‐term storage potential. The write‐in and read‐out experiments are conducted using 450 nm blue LD light with the power density of 1 W cm−2 for write‐in and that with a low power density of 0.02 W cm−2 for read‐out in order to avoid the effect of up‐conversion luminescence on PSL signal. These results will advance the electron trapping optical storage scheme.
As an emerging approach to charge storage phosphors, upconversion charging (UCC) is attracting increased attention owing to its fundamental and practical perspectives. Despite the potential, further development of the UCC technology is restricted by the limited types of excitation light sources. Here, we use a white flashlight as excitation to investigate the UCC performance of storage phosphors. We demonstrate, as an example, that a Y3Al2Ga3O12:Pr3+ phosphor exhibits long-lasting emissions in the ultraviolet and visible regions after intense illumination from the flashlight. Thermoluminescence investigations reveal that both excited-state absorption and energy-transfer upconversion are involved in the UCC process. Based on the luminescence performance of the white-light charged phosphor, a conceptual thermometry approach is introduced, which can remotely sense the local temperature by monitoring the afterglow intensity ratio. Considering the wide use of flashlight, such a white-light excitability and the associated glow emission may potentially revolutionize the way to utilize storage phosphors.
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