Ultrahigh-Energy-Transfer Efficiency and Efficient Mn²⁺ Red Emission Realized by Structural Confinement in Ca₉LiMn(PO₄)₇:Eu²⁺,Tb³⁺ Phosphor

Abstract

Structural confinement on Eu 2+ −Mn 2+ optical centers is an effective strategy to boost Mn 2+ red emission. On the basis of the Ca 9 LiMn(PO 4 ) 7 (CLMP) host with a compact Eu 2+ −Mn 2+ distance of ∼3.5 Å, a pure and intense Mn 2+ red emission without seeing Eu 2+ emission is realized, indicating that an ultrahigh energy transfer (ET) could be induced by a structural confinement effect. It is found that the Mn 2+ emission intensity and quantum efficiency could be further improved by a Tb 3+ bridging effect, which offers extra energy levels to reduce the energetic mismatch between the excited states of Eu 2+ and Mn 2+ . The optimal sample CLMP:0.02Eu 2+ ,0.90Tb 3+ shows a promising performance in terms of high color purity (93.9%), high quantum efficiency (QE = 51.2%), and good thermal stability (70% of the room-temperature value at 373 K). All of the results demonstrate that CLMP:Eu 2+ ,Tb 3+ phosphor is a promising red-light-emitting-diode phosphor, and the structural confinement effect should be developed as a general strategy to enhance the ET efficiency for a pure and efficient emission.

Thermally Stable Tb3+/Eu3+-Codoped K0.3Bi0.7F2.4 Nanoparticles with Multicolor Luminescence for White-Light-Emitting Diodes

“…Moreover, the total integrated fluorescence intensity of the studied samples at 423 K also retains 71.4% of its original value at the temperature of 303 K. These achievements indicate that the Tb 3+ /Eu 3+ -codoped K 0.3 Bi 0.7 F 2.4 nanoparticles have excellent thermal stability, which allows them to be suitable for high-power white-LED applications. For the aim of getting deeper insights into the aforementioned thermal quenching performance, we further discuss the activation energy (Δ E ) by employing the following function , where I 0 and I are regarded as fluorescence intensities at the original temperature and testing temperature T , respectively, k stands for the Boltzmann coefficient, whose value is 8.629 × 10 5 eV K –1 , and A represents a constant. The plot of ln­( I 0 / I – 1) versus 1/ kT is illustrated in Figure d.…”

Structural Confinement for Cr3+ Activators toward Efficient Near-Infrared Phosphors with Suppressed Concentration Quenching

“…The side effect could be solved with the use of the structural confinement effect, which was discovered in Sr 9 MnLi­(PO 4 ) 7 according to the highly efficient Eu–Mn energy transfer, as reported by our group in 2018 . Then, the structural confinement on Ca 9 MnLi­(PO 4 ) 7 :Eu 2+ , Tb 3+ and β-Ca 3 (PO 4 ) 2 –Ca 9 La­(PO 4 ) 7 :Eu 2+ , Mn 2+ solid solution phosphors has been investigated to realize the efficient and tunable emission. , In the crystal structure of Sr 9 M­(PO 4 ) 7 , the M 3+ ion coordinates with the surrounding six oxygen atoms . The framework structure is rigid enough to keep the volumes of [MO 6 ] octahedra almost unchanged regardless of the type of M ion.…”

“…28 Then, the structural confinement on Ca 9 MnLi(PO 4 ) 7 :Eu 2+ , Tb 3+ and β-Ca 3 (PO 4 ) 2 −Ca 9 La(PO 4 ) 7 :Eu 2+ , Mn 2+ solid solution phosphors has been investigated to realize the efficient and tunable emission. 29,30 In the crystal structure of Sr 9 M(PO 4 ) 7 , the M 3+ ion coordinates with the surrounding six oxygen atoms. 31 The framework structure is rigid enough to keep the volumes of [MO 6 ] octahedra almost unchanged regardless of the type of M ion.…”

Structural Confinement toward Controlling Energy Transfer Path for Enhancing Near-Infrared Luminescence

“…Besides, ET between different luminescence centers such as Cr 3+ and Yb 3+ ions has been widely employed in LiScP 2 O 7 , Gd 3 Sc 1.5 Al 0.5 Ga 3 O 12 , Ca 2 LuZr 2 Al 3 O 12 , and Ca 2 YHf 2 Al 3 O 12 hosts to enhance luminescence efficiency and thermal stability. ,− It is worth noting that ET is closely related to the distance between optically active ions. According to the Dexter theory, a close sensitizer–activator distance is preferred for highly efficient ET, as exhibited in different rare-earth/transition-metal-doped materials. , In the structure of Sr 9 Cr­(PO 4 ) 7 (SCP), the structural confinement effect can control the distance between luminescence centers, thereby inhibiting the ET between specific luminescence quenching centers and inducing the ET from luminescence quenching center to the other more thermally stable efficient center.…”