다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

비만아 부모의 돌봄 경험: q 방법론

Perovskites form an important and enormous class of inorganic compounds. Recently, perovskite materials have attracted extensive research interest owing to their excellent optoelectronic properties. Deep insights into the relationships between the crystal structure, electronic structure and properties play an important role in the development of new functional materials and high-performance devices. In this review, after a brief introduction, we first discuss the crystal structure and crystal chemistry of perovskites according to their three classes: standard perovskites, low-dimensional perovskites and perovskite-like halides. Next, the electronic structure and luminescence from different physical origins are presented. Then, we present a survey on the design, synthesis and luminescence properties of different perovskites, including halide perovskites, oxide perovskites, and lanthanide- or transition metal-doped perovskites, also including dimension-different perovskites (3D, 2D, 1D and quantum dots). We also summarize the strategies for improving the photoluminescence quantum yield (PLQY) and chemical stability, including by surface passivation, encapsulation and doping. Finally, we review their applications and give a brief outlook.

Luminescent perovskites: recent advances in theory and experiments

The development of phosphor materials with outstanding photoluminescence properties is critical for next-generation high-quality solid-state white lighting. As there is a blue-green cavity existing in the emission spectra of the traditional phosphor-converted white-light-emitting diodes (w-LEDs), the cyan-emitting phosphor serves as an important function in compensating the spectral gap to realize “full-visible-spectrum lighting”. Herein, we reported the discovery of an efficient cyan-emitting Ce3+-doped Ca2YHf2Al3O12 (CYHAO) garnet phosphor with good thermal stability. The as-prepared CYHAO:xCe3+ phosphor exhibited a broad excitation band in the range of 360 to 460 nm with a maximum at 408 nm, making this phosphor compatible with an efficient 400 nm near-ultraviolet (NUV)-emitting LED chip. Under 408 nm excitation, the optimal sample of CYHAO:0.03Ce3+ exhibited bright broadband cyan emission (λem = 493 nm; bandwidth = 100 nm) together with an extra-high internal quantum efficiency (IQE) of 89.5% and external quantum efficiency (EQE) of 69.1%. Notably, the as-prepared CYHAO:0.03Ce3+ phosphor showed good thermal stability (64.2% of emission intensity retained at 423 K) and excellent color stability when working in the temperature range of 303–463 K. Importantly, the constructed w-LED device exhibited bright well-distributed warm white light with a high color rendering index (CRI; Ra = 93.5 and R12 = 90.4) and low correlated color temperature (3700 K) under 60 mA driven current, indicating that the title cyan phosphor can be utilized for the compensation of the blue-green cavity to be applied in full-visible-spectrum lighting. Furthermore, these findings provide new insights into exploring high-performance cyan phosphors for NUV-pumped high-CRI warm w-LEDs.

Full-visible-spectrum lighting enabled by an excellent cyan-emitting garnet phosphor

Finding efficient cyan phosphors with broadband absorption in the near-ultraviolet range (380–420 nm) and bright emission around 490 nm are highly important to make up for the so-called cyan gap (480–520 nm) in traditional tricolor (blue, green and red) phosphor-converted white light-emitting diodes (LEDs). Herein, we reported a new garnet phosphor, namely Ca2LuZr2(AlO4)3:Ce3+ (CLZA:Ce3+), with a cyan-emitting band, which enabled to fill the cyan gap and realize high color rendering white LEDs. The composition-optimized CLZA:1% Ce3+ phosphors showed an intense broad excitation band in the 370–475 nm wavelength range peaked at 408 nm and a broad asymmetric emission band at around 483 nm in the wavelength range of 414–650 nm. Importantly, the cyan-emitting CLZA:1% Ce3+ phosphors possessed a luminescence efficiency of 58%. Notably, the CLZA:1% Ce3+ cyan phosphors allowed to fill the cyan gap between the blue and green emission bands in white LEDs, and the value of color rendering index could be enhanced from 82.3 to 89.2. This study provides new insights into designing and developing suitable efficient phosphors for high-color-quality solid-state white lighting.

https://pubs.rsc.org/en/content/articlepdf/2020/tc/c9tc04952e

A broadband cyan-emitting Ca 2 LuZr 2 (AlO 4 ) 3 :Ce 3+ garnet phosphor for near-ultraviolet-pumped warm-white light-emitting diodes with an improved color rendering index

In this Letter, we report a novel NaLaMgWO6:Mn4+ double-perovskite phosphor. Under the excitation at 342 nm, this phosphor showed a high-efficiency far-red emission at approximately 700 nm with internal quantum efficiency of up to 60%. Moreover, it exhibited a high thermal stability; the emission intensity at 423 k was approximately 57% of that at room temperature. Finally, a prototype light-emitting diode (LED) device was fabricated using the combination of a NaLaMgWO6:Mn4+ far-red-emitting phosphor and 365-nm LED chip.

High-efficiency and thermally stable far-red-emitting NaLaMgWO6:Mn4+ phosphorsfor indoor plant growth light-emitting diodes.

Inorganic phosphors with broadband near-ultraviolet (near-UV) excitation and efficient visible emission are highly important for fabricating high-performance near-UV-pumped white light-emitting diodes (LEDs). Herein, we report on novel efficient near-UV-excitable Ce3+/Tb3+ ion co-activated Ca2YHf2Al3O12 (CYHA) green-emitting garnet phosphors, which were successfully prepared through a high-temperature solid-state reaction process. X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, elemental mapping, photoluminescence, CIE color coordinates, the internal and external quantum efficiency, and temperature-dependent emission spectra were used to characterize the samples. Interestingly, due to the efficient energy transfer from Ce3+ to Tb3+ ions in CYHA, the CYHA:Ce3+,Tb3+ samples presented a wide excitation band in the 370–470 nm region peaking around 408 nm owing to the 4f–5d transition of Ce3+ ions, and under 408 nm excitation they showed intense characteristic sharp green emission around 543 nm corresponding to the 5D4 → 7F0–6 transitions of Tb3+ ions. The energy transfer mechanism from Ce3+ to Tb3+ ions was ascribed to the quadruple–quadruple interaction, and the energy transfer efficiency reached as high as 93.2%. Notably, the composition-optimized CYHA:0.03Ce3+,0.6Tb3+ sample exhibited a high internal quantum efficiency (IQE) of 78.5% and external quantum efficiency (EQE) of 56%, which were much higher than those of the Tb3+ singly-activated CYHA:0.6Tb3+ sample (IQE = 8%, EQE = 2.2%). Finally, a prototype white LED device was made by combining a 400 nm near-UV-emitting LED chip with a phosphor blend of the as-prepared CYHA:0.03Ce3+,0.6Tb3+ green phosphors, commercial BaMgAl10O17:Eu2+ blue phosphors and commercial CaAlSiN3:Eu2+ red phosphors, which emitted bright warm-white light with good CIE chromaticity coordinates of (0.391, 0.356), a low correlated color temperature of 3528 K and a high color rendering index of 92.3 under 120 mA driving current. This work opens up new opportunities for the development of efficient color converters toward near-UV-pumped warm-white LEDs with high color rendering index.

Highly efficient near-UV-excitable Ca2YHf2Al3O12:Ce3+,Tb3+ green-emitting garnet phosphors with potential application in high color rendering warm-white LEDs

Inorganic phosphors play an important role in realizing high-performance white light-emitting diodes (LEDs), and thus highly luminescent phosphors with excellent optical properties are urgently needed. In this paper, novel Ce3+/Tb3+ co-doped Ca2YZr2(AlO4)3 (abbreviated as: CYZA) green-emitting phosphors with broadband excitation and high quantum efficiency were synthesized for potential application in white LEDs, and their phase purity, crystal structure, morphology, photoluminescence properties, energy transfer mechanism, and thermal stability were systematically investigated. It was found that the CYZA:Ce3+,Tb3+ phosphors exhibited two broad excitation bands in the 300–470 nm wavelength range, due to the highly efficient energy transfer from Ce3+ to Tb3+ ions. Under the excitation wavelength of 408 nm, the CYZA:Ce3+,Tb3+ phosphors showed bright green emissions around 492, 543, 591, and 628 nm originating from the 5D4 → 7FJ (J = 6, 5, 4, and 3) transitions of Tb3+ ions. The optimal doping concentrations of Ce3+ and Tb3+ ions in CYZA:xCe3+,yTb3+ phosphors were determined to be x = 0.04 and y = 0.9, respectively. The CIE coordinates and the internal quantum efficiency of the composition-optimized CYZA:0.04Ce3+,0.9Tb3+ phosphors were measured to be (0.342, 0.545) and 56%, respectively. The full width at half-maximum (FWHM) of the dominant green emission band around 543 nm was only about 13.5 nm. Finally, a white LED lamp was fabricated using a 400 nm LED chip together with a phosphor blend of blue-emitting BaMgAl10O17:Eu2+, green-emitting CYZA:0.04Ce3+,0.9Tb3+ and red-emitting CaAlSiN3:Eu2+, which produced warm white light with color coordinates of (0.419, 0.392), excellent color rendering index of 91, correlated color temperature of 3233 K, and luminous efficacy of 30 lm W−1 when driven by a 40 mA current. The above results demonstrated that CYZA:0.04Ce3+,0.9Tb3+ can be a potential green-emitting color converter for white LEDs.

Highly efficient Ce3+ → Tb3+ energy transfer induced bright narrowband green emissions from garnet-type Ca2YZr2(AlO4)3:Ce3+,Tb3+ phosphors for white LEDs with high color rendering index

Liangling Sun

Papers

Full-visible-spectrum lighting enabled by an excellent cyan-emitting garnet phosphor

A broadband cyan-emitting Ca 2 LuZr 2 (AlO 4 ) 3 :Ce 3+ garnet phosphor for near-ultraviolet-pumped warm-white light-emitting diodes with an improved color rendering index

High-efficiency and thermally stable far-red-emitting NaLaMgWO6:Mn4+ phosphorsfor indoor plant growth light-emitting diodes.

Highly efficient near-UV-excitable Ca2YHf2Al3O12:Ce3+,Tb3+ green-emitting garnet phosphors with potential application in high color rendering warm-white LEDs

Highly efficient Ce3+ → Tb3+ energy transfer induced bright narrowband green emissions from garnet-type Ca2YZr2(AlO4)3:Ce3+,Tb3+ phosphors for white LEDs with high color rendering index