Prevailing Strategies to Tune Emission Color of Lanthanide‐Activated Phosphors for WLED Applications

Thermal quenching of phosphor is an important challenge for its practical application in phosphor‐converted white light‐emitting diodes (pc‐WLEDs) and it usually becomes aggravated with the increase of activator concentration. Conversely, this work finds the thermal quenching of Eu2+ emission at 490 nm in Sr4Al14O25:Eu2+ does not follow this in the temperature range of 300 to 480 K, and the rate of it is even slowed down as the concentration of Eu2+ increases. However, at the same time, the experiment on three heating‐cooling cycles of Sr4Al14O25:Eu2+ reveals that the thermal degradation of Eu2+ emission becomes improved. Once Eu2+ ions are doped into Sr4Al14O25, they will prefer substituting for the 10‐ and 7‐coordinated strontium sites Sr1 and Sr2, respectively. The emission centers Eu1 and Eu2, therefore, appear. The abnormal phenomenon is perhaps partly due to the enhanced energy transfer from the emission center Eu1 at 407 nm to the one Eu2 at 490 nm. It is also found interesting that the introduction of AlN can enhance the emission of Sr4Al14O25:Eu2+ without leading to the deterioration of thermal degradation. In the end, a prototype of pc‐WLED was fabricated with Sr4Al14O25:Eu2+ to demonstrate the application of white lighting. This work is not only beneficial to the understanding of the relationship between concentration and thermal quenching, but also conducive to the design of the heavily doped phosphor for WLEDs with better resistance to thermal quenching.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Unusual concentration induced antithermal quenching of the Eu²⁺ emission at 490 nm in Sr₄Al₁₄O₂₅:Eu²⁺ for near ultraviolet excited white LEDs

Liu

Wang

et al. 2020

“…Phosphor‐converted white light‐emitting diode (white‐LED), which shows the unique features of energy saving, small volume, high brightness, high‐luminous efficiency, etc, is considered as the fourth generation solid‐state lighting source to take place the traditional lamps, such as fluorescent bulb, halogen, and incandescent lamp . The commercial white‐LED device, which is constructed by applying the Y 3 Al 5 O 12 :Ce 3+ yellow phosphors and blue chip, emits cold white light with unsatisfied color rendering index (CRI < 75) and superior high‐color correlated temperature (CCT > 7000 K) because the Y 3 Al 5 O 12 :Ce 3+ yellow phosphors do not have enough red‐emitting component in its luminescent profile . In comparison, the other route utilizing the commercial near‐ultraviolet (NUV) chip to pump three hybrid (red‐green‐blue) emitting phosphors was put forward to generate high‐quality white‐LED lamp with high CRI and low CCT values .…”

Section: Introductionmentioning

confidence: 99%

Neoteric Mn²⁺‐activated Cs₃Cu₂I₅ dazzling yellow‐emitting phosphors for white‐LED

Luo

Cheng

2019

Neoteric Mn2+‐activated Cs3Cu2I5 yellow‐emitting halides were achieved by the simple solid‐state reaction route. The near‐ultraviolet light was the suitable excitation lighting source for the resultant halides. The resultant halides exhibited bright yellow emission under the excitation of 378 nm and the optimum dopant content was 11 mol%. The multipole‐multipole interaction contributed to the concentration quenching mechanism and the critical distance was 28.65 Å. The thermal resistance of the prepared compounds was identified by the temperature‐dependent emission spectra. Ultimately, the designed light‐emitting diode showed bright white light with satisfied color rendering index, proper color coordinate, and suitable correlated color temperature. These results indicated that the prepared yellow‐emitting halides were suitable for indoor illumination.

“…White light‐emitting diodes (W‐LEDs), as solid‐state lighting devices, have been widely involved into our daily lives in recent years on account of their advantages containing environment friendliness, high brightness, long lifetime, and low power consumption . Generally, commercial W‐LEDs are generated via integrating yellow emitting YAG:Ce 3+ phosphors with blue InGaN LED chip.…”

Section: Introductionmentioning

confidence: 99%

“…White light-emitting diodes (W-LEDs), as solid-state lighting devices, have been widely involved into our daily lives in recent years on account of their advantages containing environment friendliness, high brightness, long lifetime, and low power consumption. [1][2][3][4][5][6][7][8] Generally, commercial W-LEDs are generated via integrating yellow emitting YAG:Ce 3+ phosphors with blue InGaN LED chip. However, because of the deficient of red component, this kind of W-LEDs suffers from high correlated color temperature and low color rendering index.…”

Section: Introductionmentioning

confidence: 99%

Tunable dual‐mode emission with excellent thermal stability in Ca₄ZrGe₃O₁₂:Eu phosphors prepared in air for NUV‐LEDs

Wei

Feng

et al. 2019

Novel dual valence Eu‐doped Ca4ZrGe3O12 (CZGO) phosphors were successfully fabricated in air atmosphere through a solid‐state route. Their crystal structure, photoluminescence properties as well as thermal quenching performance were investigated systematically. The spectra show that part of Eu3+ were reduced to Eu2+ and the mechanism is interpreted by the charge compensation. By altering Eu concentration, multi‐color luminescence covering from blue to red is realized when irradiated by 370 nm light, which perfectly matches with the near ultraviolet (NUV) light‐emitting diode (LED) chips. More importantly, under NUV excitation, luminescent intensities are almost unchanged even up to 423 K. And chromaticity exhibits only a tiny shift with growing temperature. Such suitable luminescent spectra and superior thermal stability indicate that CZGO:Eu phosphors are promising candidates for blue‐red components in NUV pumped W‐LEDs. Finally, the fabricated W‐LED based on the combination of CZGO:Eu phosphors, Ba2SiO4:Eu2+ and a 365 nm NUV‐LED chip gives a high color rendering index, a low correlated color temperature and suitable CIE chromaticity coordinates.