Preparation, structure, and luminescent properties of Dy3+-doped borate Ca3La3(BO3)5: Dy3+ for potential application in UV-LEDs

Abstract

A single-phase white light-emitting phosphor Ca3La3(BO3)5: Dy3+ (CLBD) was prepared via a solid-state reaction. The introduction of Dy3+ in Ca3La3(BO3)5 with a preferred location on La3+ was confirmed by x-ray diffraction and Rietveld structural refinement studies. The micrograph observed by scanning electron microscopy reveals an inhomogeneous and uneven dense morphology in the micrometer range. The optical spectra analysis shows that the CLBD can be efficiently excited by ultraviolet (UV) light and emitted intense white light due to the combination of blue 4F9/2 → 6H15/2 (∼485 nm) and yellow 4F9/2 → 6H13/2 (∼575 nm) emissions originated from 4f–4f transitions of Dy3+. The critical concentration is determined to be ∼12 mol. %, and the dipole–dipole (d–d) interaction is responsible for the quenching mechanism. In additional, the CLBD has high thermal stability. By incorporating the CLBD with a phosphor-capping method on AlInGaN LED, we obtain the white light that meets the spectral and efficiency requirements for high-efficacy solid-state white lighting lamps. The Commission Internationale de I'Eclairage chromaticity coordinates and color correlated temperature with optimal electroluminescence intensity are calculated to be ∼(0.338, 0.342) and 5950 K, respectively. All results indicate the CLBD could serve as a promising candidate for white UV-LEDs.

Crystal Structure, Photoluminescence, and “Abnormal” High Stability of Ca3Y(GaO)3(BO3)4: Dy3+/Sm3+/La3+ for n-UV wLEDs

“…The relatively higher intensity of the blue (B) PL originated from the MDT 4 F 9/2 → 6 H 15/2 than the PL intensity of the yellow (Y) component stemmed from the EDT 4 F 9/2 → 6 H 13/2 manifests that the dopants (and Y 3+ ) in the trigonal tunnel of the CYGB were all located at an environment with a high site symmetry. 17 This result is also quite consistent with the structural analysis (Figure 2). There is a reason to believe that by further adjustment of the lattice symmetry around the dopants, the PL spectra could be further adjusted (vide infra).…”

“…Of note, relatively speaking, the investigation on codoping of ion pairs of Dy 3+ /Sm 3+ with tunable full-color-PL phosphors was rarely investigated. Dy 3+ ions could be both played as the “cool” white-light luminescent center and sensitizer, due to the 4f-4f transitions from 4 F 9/2 to 6 H 15/2, 13/2, 11/2 located at red (very weak), yellow, and blue regions, respectively. − Naturally, to change the “cool” into “warm” white PL with high CRI and low CCT, the red-emitting activator Sm 3+ , originated from the transitions of 4 G 5/2 to 6 H 11/2, 9/2, 7/2, 5/2 , , could be codoped with Dy 3+ ions. Interestingly, due to both Dy/Sm ions including the hypersensitive electric dipole transitions (EDT) as compared with the relatively stable magnetic dipole transitions (MDT), the intensity ratios of PL peaks could be further easily tuned and helped to obtain the desired color-tunable PL via modification of the local site environments of the dopants.…”

Stable color-tunable Ca3Y(GaO)3(BO3)4:Bi3+/Tb3+/Eu3+ phosphors for application in n-UV-pumped wLEDs

“…Typically, the traditional package (Scheme S1a-S1c †) efficiency in pc-wLEDs is ∼30% to 50%, where the losses are associated with the reflection/refraction of the incident/PL light. To alleviate this inherent drawback, the remote 'capping' packaging strategy was used to fabricate the pc-wLED device, where it has a small air gap between the epoxy and phosphor cap that can reduce the amount of light reflected back to the LED chip 18,23 due to the differences in refractive indices of the various layers. This packaging method could optimize light extraction and allow for better reproducibility.…”

“…[18][19][20][21] Till date, commercially available pc-wLED on the market is composed of a Y 3 Al 5 O 12 :Ce 3+ yellow phosphor and a blue LED chip. 22,23 However, this approach typically generates 'cool' white light with high correlated color temperature (CCT) and low color rendering index (CRI) owing to the red light-emitting PL deficiency (Scheme S1a, ESI †). Meanwhile, the high-intensity blue light-emitting diode with a narrow full width at half maxima (FWHM) from the blue LED chip is highly likely to cause light pollution that induces great damage to human eye.…”

Structure and luminescence properties of single-component melilite Sr2MgSi2O7:Ce/Tb/Sm for n-UV wLEDs

“…Specifically, for mode (iii), there are three main ways to achieve white PL via the single-phase phosphor, (1) singly doping, i.e., Dy 3+ , 11 (2) host defect-induced, 12 and (3) codoping multiple RE and/or TM ions via ET (Scheme S2 †). 13,14 Generally, although the first mode is the simpler and much more straightforward way, spectral adjustment is difficult, and the luminous efficiency/intensity is usually low.…”