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Upconversion Between 4f–5d Excited States in Tm 2+ ‐Doped CsCaCl 3 , CsCaBr 3 , and CsCaI 3
Author(s) -
Grimm J.,
Beurer E.,
Gerner P.,
Güdel H. U.
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200600418
Subject(s) - photon upconversion , excited state , doping , atomic physics , infrared , materials science , energy transfer , chemistry , optoelectronics , physics , optics
Near‐infrared to visible upconversion luminescence in CsCaCl 3 :Tm 2+ , CsCaBr 3 :Tm 2+ and CsCaI 3 :Tm 2+ is presented and analysed. The upconversion process involves exclusively the 4f–5d excited states of Tm 2+ , which is a novelty among upconversion materials. The presence of more than one long‐lived 4f–5d excited state is the prerequisite for this. Multiple emissions from Tm 2+ are observed in the title compounds. This is made possible by the favourable energy structure within the 4f–5d states and the low phonon energies of the materials. The energy positions of the relevant 4f–5d states, and thus the photophysical and light emission properties, are affected by the chemical variation along the series. The upconversion efficiency increases from chloride to iodide and the mechanism is found to be a combination of absorption and energy‐transfer steps.