Two-Site Occupancy Induced a Broad-Band Emission in Phosphor K₂YZr(PO₄)₃:Eu²⁺ for White-Light-Emitting Diode Applications

Abstract

Developing broad-band-emitting phosphors is very important to light-emitting diode (LED) lighting and displays. We introduced Eu 2+ to solid solutions K 2 YZr 1−y Hf y (PO 4 ) 3 with a langbeinite-type structure to prepare a series of new phosphors. In this structure, two K + sites could be occupied by Eu 2+ cations to provide two different kinds of coordination environments, leading to broad emitting bands in the range of 390−700 nm. The coordination circumstance of Eu 2+ was analyzed by Gaussian fitting and time-resolved emission spectra. Furthermore, the emitting intensity and thermal stability can be improved by modulating the crystalline field via substituting Zr 4+ by Hf 4+ . When the Zr 4+ was fully substituted by Hf 4+ , the external quantum efficiency increased by 53.75%, giving a bright cyan emission. Finally, an archetype white-LED lamp was made using cyan phosphor K 2 YHf(PO 4 ) 3 :0.04Eu, red phosphor CaAlSiN 3 :Eu 2+ , and a 365 nm LED chip, which realized an applicable color rendering index (R a = 81) and a correlated color temperature (CCT = 3792 K).

Ca[B8O11(OH)4] : Eu2+ – A Highly Efficient Deep Blue‐Emitting Phosphor Prepared by Low‐Temperature Self‐reduction

“…The slope of the linear equation is Ea , whose value is 0.33 eV, as shown in Figure 7c. Compared with other Eu 2+ doped blue phosphors, the Ea of CBH : Eu 2+ is higher than those of Ba 3 Si 6 O 12 N 2 : Eu 2+ ( Ea =0.24 eV), [72] RbNa(Li 3 SiO 4 ) 2 : Eu 2+ ( Ea= 0.25 eV), [73] K 2 YZr(PO 4 ) 3 : Eu 2+ ( Ea= 0.25 eV), [68] Ba 3 CaK(PO 4 ) 3 : Eu 2+ ( Ea= 0.26 eV ), [70] K 2 Al 2 B 2 O 7 : Eu 2+ ( Ea =0.30 eV) [74] . But the Ea of CBH : Eu 2+ is lower than that of Sr 5 SiO 4 Cl 6 : Eu 2+ ( Ea =0.35 eV), [75] K 2 BaCa(PO 4 ) 2 : Eu 2+ ( Ea =0.51 eV), [76] and KBa 2 (PO 3 ) 5 : Eu 2+ ( Ea= 0.66 eV) [77] .…”

“…The PLQY of CBH : 2 %Eu 2+ is higher than those of the perovskite type of CsPbBr x Cl 3−x (PLQY=89 %), [61] the UCr 4 C 4 type of RbNa 3 (Li 3 SiO 4 ) 4 : Eu 2+ (PLQY=53 %), [15] commercial phosphor of BaMgAl 10 O 17 : Eu 2+ (PLQY=92.4 %) [14] and other aluminate of BaAl 12 O 19 : Eu 2+ (PLQY=90 %), [59] borates of Ba 3 Y 2 B 6 O 15 :Ce 3+ (PLQY=84 %), [62] BaAlBO 3 F 2 : Eu 2+ (PLQY=76 %), [63] Ba 2 (Y 1−x Lu x ) 5 B 5 O 17 :Ce 3+ (x=0∼1) (PLQY=90 %), [64] and phosphate of Sr 4.99 (PO 4 ) 3 Cl:0.01Eu 2+ (PLQY=80.5 %) [16] . The external quantum efficiency (EQE) of CBH : Eu 2+ is measured to be 31.1 %, which is higher than those of the recently reported blue phosphor of (Na 2−2x Eu x )MgPO 4 F (EQE=18.1 %), [65] Na 0.58(4) K 0.42(4) Li 3 SiO 4 : Eu 2+ (EQE=30.0 %), [66] and KMg 4 (PO 4 ) 3 : Eu 2+ (EQE=18.6 %), [67] but lower than those of K 2 YZr(PO 4 ) 3 : Eu 2+ (EQE=40 %), [68] and Sr 3.61(1−x) Eu 3.61 xLiSi 14.27 Al 5.61 O 6.19 N 23.25 (EQE=37 %), [69] and commercial BAM : Eu 2+ phosphor (EQE=37 %) [67] …”

Two-site occupancy induced the broad-band emission in the Ba4−x−ySryLa6O(SiO4)6:xEu2+ phosphor for white LEDs and anti-counterfeiting

“…The luminescence performance of Eu 2+ is sensitive to the crystal field, and, thus, changing the chemical composition of the BLOS host lattice will affect the coordination environment of Eu 2+ and modulate the PL properties. 5 In order to optimize the performance of the BLOS:Eu 2+ phosphor, a series of novel phosphors by replacing Ba 2+ with Sr 2+ ions in BLOS:Eu 2+ are designed. The XRD patterns and the peak shift at 30.2–31.1° of Ba 3.92− y Sr y La 6 O(SiO 4 ) 6 :0.08Eu 2+ ( y = 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5) are shown in Fig.…”

“…White light-emitting diodes (w-LEDs) have been widely used due to their environmental protection, low energy consumption, high luminous efficiency, long life, small size, and high luminous efficiency. 5 At present, most mainstream commercial w-LEDs are fabricated by integrating blue LED chips and Y 3 Al 5 O 12 :Ce 3+ (YAG:Ce 3+ ) yellow phosphors. 41–43 This type of white light source is characterized by a low color rendering index (CRI) and correlated color temperature (CCT).…”

A new type of phosphate-based phosphor Na3CsMg7(PO4)6:Eu2+/Mn2+with high quantum efficiency and high thermostability

“…Looking more closely, both photoluminescence excitation (PLE) and emission (PL) peaks do not feature a single Gaussian distribution form but a composite form, which indicates multiple Eu 2+ luminescence centers in NCMP:0.18Eu 2+ because the Eu 2+ luminescence is easy to be affected by the crystal field environment. 35,36 A typical feature of the PLE spectrum is that it is composed of one weak peak at about 333 nm and a strong peak at about 395 nm. A combined contour map in Fig.…”