All-inorganic CsPbX3 (X=I, Br, Cl) perovskite quantum dots (PQDs) have been investigated because of their optical properties, such as tunable wavelength, narrow band, and high quantum efficiency. These features have been used in light emitting diode (LED) devices. LED on-chip fabrication uses mixed green and red quantum dots with silicone gel. However, the ion-exchange effect widens the narrow emission spectrum. Quantum dots cannot be mixed because of anion exchange. We address this issue with a mesoporous PQD nanocomposite that can prevent ion exchange and increase stability. We mixed green quantum-dot-containing mesoporous silica nanocomposites with red PQDs, which can prevent the anion-exchange effect and increase thermal and photo stability. We applied the new PQD-based LEDs for backlight displays. We also used PQDs in an on-chip LED device. Our white LED device for backlight display passed through a color filter with an NTSC value of 113 % and Rec. 2020 of 85 %.
All‐inorganic CsPbX3 (X=I, Br, Cl) perovskite quantum dots (PQDs) have been investigated because of their optical properties, such as tunable wavelength, narrow band, and high quantum efficiency. These features have been used in light emitting diode (LED) devices. LED on‐chip fabrication uses mixed green and red quantum dots with silicone gel. However, the ion‐exchange effect widens the narrow emission spectrum. Quantum dots cannot be mixed because of anion exchange. We address this issue with a mesoporous PQD nanocomposite that can prevent ion exchange and increase stability. We mixed green quantum‐dot‐containing mesoporous silica nanocomposites with red PQDs, which can prevent the anion‐exchange effect and increase thermal and photo stability. We applied the new PQD‐based LEDs for backlight displays. We also used PQDs in an on‐chip LED device. Our white LED device for backlight display passed through a color filter with an NTSC value of 113 % and Rec. 2020 of 85 %.
Two types of infrared fluoride phosphors, Cr3+-doped K3AlF6 and K3GaF6, were developed in this research. The K3Al1–x
F6:xCr3+ and
K3Ga1–y
F6:yCr3+ fluoride phosphors were proven
to be pure phase via X-ray diffraction refinement, which demonstrated
that the procedure can be applied to large-scale production. Electron
paramagnetic resonance measurements indicated that Cr3+ ions in cubic with respect to noncubic are coupled better with K3GaF6 than with K3AlF6. The
main differences between these two phosphors, the site symmetry and
pressure behavior of the spectra, were obtained in temperature- and
pressure-dependent spectra. According to the calculation results,
Cr3+ in fluorine coordination at ambient pressure indicates
an intermediate crystal field. For the phosphor-converted light-emitting
diodes (LEDs) fabricated from these two phosphors, the spectral range
is from 650 to 1000 nm, which resulted in a radiant flux of 7–8
mW with an input power of 1.05 W. The research reveals detailed luminous
properties, which will lead to a new way of studying Cr3+-doped fluoride phosphors and their application in LEDs.
CsPbX3 (X = Cl, Br, I), as a potential luminescent material with excellent optical characteristics, has attracted researchers for several years but remains difficult to be commercially used due to...
A GaN/AlGaN-based ultraviolet light-emitting diode (LED) structure with an embedded porous-AlGaN reflector was fabricated by a doping-selective electrochemical (EC) wet-etching process. The n+-AlGaN/undoped-AlGaN (u-AlGaN) stack structures with different Al contents were transformed into porous-AlGaN/u-AlGaN stack structures that acted as the embedded distributed Bragg reflectors (DBRs). The porosity of the EC-treated AlGaN layer was increased by decreasing the Al content in the n+-AlGaN layer. The reflectivity of the porous-AlGaN DBR structure was measured to be 90% at 379.3 nm with a 37.2 nm stopband width. The photoluminescence emission intensity of the DBR-LED was enhanced by forming the embedded porous-AlGaN DBR structure.
The analysis of human body composition
and food composition requires
high-efficiency broadband near-infrared (NIR) lighting sources to
achieve a portable, appropriately sized equipment. Herein, we develop
a whitlockite-type NIR phosphor Sr9Sc(PO4)7:Cr3+ with an emission centered at 860 nm and full
width at half-maximum of 147 nm. Due to the structural characteristics
of the matrix, the 60 mol % Cr3+ substitution at the Sc3+ sites gives an internal quantum efficiency up to 56.5%.
By replacing Sr with Ba and Ca, we observe a nontypical spectral shift
phenomenon and discuss the influence of the second-sphere effect on
octahedral Cr3+ ions. To evaluate the diagnostic application,
we design a NIR ceramic device with a high optical power of 27.38
mW and high heat dissipation, which can decrease surface working temperature
by nearly 50 °C for digital intraoral application. This study
provides the research of the second-sphere coordination effect for
selective octahedral sites such as Ca, Sr, and Ba coordinated by O
atoms on a whitlockite-type crystal. Furthermore, the device promotes
a nonionizing solution for detecting dental caries, tooth calcification,
and diagnostic application.
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