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A Quantum‐Splitting Phosphor Exploiting the Energy Transfer from Anion Excitons to Tb 3+ in CaSO 4 :Tb,Na
Author(s) -
Lakshmanan A. R.,
Kim S.B.,
Jang H. M.,
Kum B. G.,
Kang B. K.,
Heo S.,
Seo D.
Publication year - 2007
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200600010
Subject(s) - phosphor , ion , materials science , exciton , excitation , quantum efficiency , doping , activator (genetics) , atomic physics , band gap , photon , ultraviolet , optoelectronics , physics , condensed matter physics , chemistry , optics , quantum mechanics , gene , biochemistry
Wide‐bandgap materials doped with rare‐earth ions are currently of great interest as new vacuum ultraviolet (VUV) phosphors for lighting and displays. This paper reports the development of a highly sensitive green phosphor, CaSO 4 :Tb,Na, which exhibits a quantum efficiency higher than 100 % by exploiting the energy‐transfer mechanism from anion excitons to the activator ions, Tb 3+ . The VUV excitation spectra of CaSO 4 :Tb 3+ with Na + as a charge compensator show two prominent excitation bands at 147 and 216 nm. The former band is attributed to the charge‐transfer excitations within SO 4 2– complexes while the latter was assigned to the 4f 8 → 4f 7 5d transitions on Tb 3+ . The energy‐transfer mechanism from anion excitons to Tb 3+ strongly raises the possibility of two‐photon emission via a second‐order down‐conversion under the VUV excitation, which is basically a new approach in the goal of achieving a quantum‐splitting phosphor.