Open AccessDisputed Mechanism for NIR-to-Red Upconversion Luminescence in NaYF4:Yb3+,Er3+
Author(s) -
Mary T. Berry,
P. Stanley May
Publication year - 2015
Publication title -
the journal of physical chemistry. a/the journal of physical chemistry. a.
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.756
H-Index - 235
eISSN - 1520-5215
pISSN - 1089-5639
DOI - 10.1021/acs.jpca.5b08324
Subject(s) - photon upconversion , excited state , excitation , blue light , relaxation (psychology) , energy transfer , luminescence , materials science , chemistry , optoelectronics , physics , atomic physics , psychology , social psychology , quantum mechanics
The most commonly proposed mechanisms for NIR-to-red upconversion in the well-studied material β-NaYF4:Er(3+),Yb(3+) are evaluated in order to resolve inconsistencies that persist in the literature. Each of four possible mechanisms is evaluated in terms of the direct analysis of spectroscopic data. It is shown that there are no important mechanisms that involve the first excited state of Er(3+), (4)I13/2, as an intermediate state. A large body of evidence overwhelmingly supports the proposed mechanism of Anderson et al., which suggests an intimate connection between NIR-to-red and NIR-to-blue upconversion. Namely, both red and blue upconversion are produced primarily by a three-photon excitation process that proceeds through the green emitting state to a dense manifold of states, (4)G/(2)K, above the blue emitting state, (2)H9/2. Competing relaxation mechanisms out of (4)G/(2)K determine the relative amounts of blue and red upconversion produced. Multiphonon relaxation from (4)G/(2)K results in blue upconversion, whereas back energy transfer from Er(3+)((4)G/(2)K) to Yb(3+)((2)F7/2) results in red emission.