A novel narrow-line red emitting Na2Y2B2O7:Ce3+,Tb3+,Eu3+ phosphor with high efficiency activated by terbium chain for near-UV white LEDs

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 42; no. 47; pp. 16621 - 16629
• Main Authors: Wen, Dawei, Shi, Jianxin
• Format: Journal Article
• Language: English
• Published: 01.01.2013
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c3dt52214h

The application of white LEDs is hindered by the low efficiency of commercial red phosphors. Here, a novel narrow-line red phosphor is produced by a terbium chain in the form of Ce 3+ -(Tb 3+ ) n -Eu 3+ in the Na 2 Y 2 B 2 O 7 host and is characterized with X-ray diffraction, photoluminescence (PL), PL excitation (PLE), and fluorescence lifetime, and the energy transfer (ET) processes between rare-earth ions in the host are discussed. The formation of terbium chain with a quite low content of Tb 3+ in Na 2 Y 2 B 2 O 7 is realized by the ET processes of Ce 3+ -Tb 3+ and Tb 3+ -Eu 3+ , and a new concept of saturation distance is put forward as an explanation for the first time. An energy level diagram is proposed to explain the ET processes in the phosphor of Na 2 Y 2 B 2 O 7 :Ce 3+ ,Tb 3+ ,Eu 3+ . The emitting colour of the phosphor can be tuned from blue to green or yellow and finally to the orange-red region with increasing the content of Tb 3+ . The quantum efficiency of the phosphor with an optimized ratio of rare-earth ions, Na 2 Y 2 B 2 O 7 :0.5% Ce 3+ ,60% Tb 3+ ,0.5% Eu 3+ , is up to 77% under the excitation of 365 nm, which indicates that the as-synthesized phosphor is applicable to near-UV white LEDs. Energy transfer of Ce 3+ → Tb 3+ → Eu 3+ producing high efficiency red emitting phosphor with relatively low terbium concentration.