Highly efficient green phosphor Ca₄La(PO₄)₃O:Eu²⁺,Tb³⁺ for white LEDs

Area of Science:

• Materials Science
• Solid-State Chemistry
• Luminescence

Background:

• Improving green light emission in phosphors is crucial for efficient lighting.
• Energy transfer from Eu²⁺ to Tb³⁺ enhances green emission but often suffers from low quantum efficiency.
• Novel host materials are needed to achieve high-performance phosphors.

Purpose of the Study:

• To synthesize and characterize a novel apatite-type phosphor, Ca₄La(PO₄)₃O (CLPO), doped with Eu²⁺ and Tb³⁺.
• To investigate the energy transfer mechanisms between Eu²⁺ and Tb³⁺ in the CLPO host.
• To evaluate the performance of the developed phosphor for white light-emitting diode (WLED) applications.

Main Methods:

• Synthesis of CLPO:Eu²⁺,Tb³⁺ phosphors using a solid-state reaction method.
• Characterization of crystal structure and photoluminescence properties.
• Measurement of quantum efficiency and construction of WLED devices.

Main Results:

• A novel apatite-type structure CLPO:Eu²⁺,Tb³⁺ was successfully synthesized.
• CLPO:Eu²⁺ exhibits blue emission (~460 nm) upon near-UV excitation.
• Efficient energy transfer from Eu²⁺ to Tb³⁺ was achieved, resulting in high internal (96.6%) and external (64.7%) quantum efficiencies for the optimized CLPO:0.02Eu²⁺,0.7Tb³⁺.
• WLEDs fabricated with CLPO:0.02Eu²⁺,0.7Tb³⁺ showed a Ra value of 89.9 and a correlated color temperature of 3808 K.

Conclusions:

• The novel CLPO host material enables efficient energy transfer from Eu²⁺ to Tb³⁺ for high-performance green phosphors.
• The developed CLPO:Eu²⁺,Tb³⁺ phosphor is a promising candidate for efficient WLED applications.
• This work offers a new strategy for designing efficient green phosphors by selecting appropriate hosts and optimizing energy transfer.