A Mn4+-doped oxyfluoride phosphor with remarkable negative thermal quenching and high color stability for warm WLEDs

Wang

et al. 2021

J Am Ceram Soc.

The exploration of the high thermal stability near‐infrared (NIR) phosphors is significantly crucial for the development of plant lighting. However, NIR phosphors suffer from the poor chemical and thermal stability, which severely limits their long‐term operation. Here, the successful improvement of luminous intensity (149.5%) and thermal stability at 423 K of Zn3Ga2GeO8 (ZGGO): Cr3+ phosphors is achieved for the introduction of Al3+ ions into the host. The release of carriers in deep traps inhibits the emission loss for the thermal disturbance. Furthermore, an NIR light emitting diodes (LEDs) lamp is explored by combining the optimized Zn3Ga1.1675Al0.8GeO8: 0.0325Cr3+ phosphors with a commercial 460 nm blue chip, and the emission band can match well with the absorption bands of photosynthetic pigments and the phytochrome (PR and PFR) of plants. The explored LEDs lamp further determines the growth and the pheromone content of the involved plants for the participation of the NIR emission originated from Cr3+ ions. Our work provides a promising NIR lamp as plant light with improved thermal stability for long‐term operation.

Section: Resultsmentioning

confidence: 99%

Improved thermal stability of the near‐infrared Al‐modulated Zn₃Ga₂GeO₈: Cr³⁺ phosphors for plant growth applications

Wang

et al. 2021

J Am Ceram Soc.

“…In recent years, Mn 4 + doped fluoride phosphors have attracted widespread attention in the fields of liquid crystal display (LCD) [1] and solid-state lighting (SSL). [2] So far, a series of Mn 4 + -doped fluoride red-emitting phosphors, such as A 2 XF 6 : Mn 4 + (A = NH 4 , Li, Na, K, Rb and Cs; X = Si, Ti, Ge, Sn, Zr and Hf), [3][4][5][6] BXF 6 (6H 2 O) : Mn 4 + (B = Ba and Zn), [7][8][9][10] A 3 MF 6 : Mn 4 + (M = Al, Ga and Sc), [1,[11][12][13] A 2 NF 7 : Mn 4 + (N = Ta and Nb), [14,15] A 2 NO x F 6-x : Mn 4 + (x = 1, N = Ta and Nb; x = 2, N = W and Mo) [16][17][18][19] and A 3 XF 7 : Mn 4 + [20] has been reported. Unfortunately, although fluoride phosphors with a narrow emission at around 630 nm exhibit unique luminescence performance under blue light excitation, the deterioration of luminescent properties as a result of obvious hydrolysis has limited their large-scale application.…”

Section: Introductionmentioning

confidence: 99%

A Reverse Strategy to Restore the Moisture‐deteriorated Luminescence Properties and Improve the Humidity Resistance of Mn⁴⁺‐doped Fluoride Phosphors

Chemistry An Asian Journal

et al. 2020

Self Cite

Fluoride phosphors as red components for warm white LEDs have attracted a tremendous amount of research attention. But these phosphors are extremely sensitive to moisture, which seriously limits their practical industrial applications. To tackle this problem, unlike all the straightforward preventive strategies, a reverse strategy "Good comes from bad" was successfully developed to treat the degraded K 2 SiF 6 : Mn 4 + (D-KSFM) phosphor in the present study, which not only completely restores the luminescence properties, but also significantly enhances the moisture resistance at the same time. After treatment with an oxalic acid solution as restoration modifier, the emission intensity of the D-KSFM phosphor can be restored to 103.7% of the original K 2 SiF 6 : Mn 4 + red phosphor (O-KSFM), and the moisture resistance is remarkably improved. The restored K 2 SiF 6 : Mn 4 + (R-KSFM) maintains approximately 62.3% of its initial relative emission intensity after immersing in deionized water for 300 min, while the reference commercial K 2 SiF 6 : Mn 4 + with a protective coating (C-KSFM) is only 33.2%. As a proof of general applicability, this strategy was also conducted to K 2 TiF 6 : Mn 4 + phosphor, which is less moisture-stable than K 2 SiF 6 : Mn 4 +. The luminescence intensity of the degraded K 2 TiF 6 : Mn 4 + (D-KTFM) phosphor can be restored to 162.6% of original level of the K 2 TiF 6 : Mn 4 + synthesized through a cation exchange approach without any treatment (O-KTFM). The emission intensity of the restored K 2 TiF 6 : Mn 4 + (R-KTFM) phosphor retains 62.8% of its initial emission intensity after soaking in deionized water for 300 min. Finally, the R-KSFM phosphors were packaged into white light-emitting diodes with blue InGaN chips and Y 3 Al 5 O 12 : Ce 3 + yellow phosphors. The WLEDs display excellent color rendition with higher color rendering index, lower color temperature (WLED-II: R a = 83.6, R 9 = 57.3, 3743 K, η l = 199.68 lm/W; WLED-III: R a = 90.4, R 9 = 94.2, 2892 K, η l = 183.3 1 m/W). The above results show that the reverse strategy can be applied in those phosphor materials with poor moisture resistance to restore luminescence properties and improve moisture resistance without excessively care about the deterioration during the production, storage and transportation.

“…The highly-distorted octahedral coordination environment of Mn 4+ ions may induce the local symmetry to lose the inversion centre, which is expected to heighten the emission intensity of ZPL, while the crystal defects would has serious effect for the thermal stability. 26 TEM analysis in Fig. 2(b) demonstrates that the whole particle of the K 3 TaOF 6 :0.04Mn 4+ sample exhibits the crystalline nature.…”

Section: Resultsmentioning

confidence: 92%

Mn⁴⁺-activated oxyfluoride K₃TaOF₆ red phosphor with intense zero phonon line for warm white light-emitting diodes

Wang

et al. 2021

RSC Adv.