Review—Photoluminescence Spectroscopy of Eu²⁺-Activated Phosphors: From Near-UV to Deep Red Luminescence

Abstract

In this review article, the characteristic luminescence behaviors of the Eu2+-activated phosphors are discussed from a spectroscopic point of view. This spectroscopic point of view makes possible to classify the Eu2+-activated phosphors into two groups: types Eu2-A and Eu2-B, where an energy inequality relation of the lowest excited state of type Eu2-A to be given by 4f 7 (6 P 7/2)→4f 65d, whereas that of type Eu2-B is given by 4f 7 (6 P 7/2)→4f 65d. Simply saying, the 6 P 7/2 excited manifold of the 4f 7 configuration is located just below and well above the lowest-energy 5d level of the Eu2+ ion in types Eu2-A and Eu2-B phosphors, respectively. While generally uncommon, in some host materials the 4f 7 (6 P 7/2)→ 4f 7 (8 S 7/2) intra-configurational transitions of Eu2+ occur with exhibiting the characteristic narrow-line emissions. An analysis method based on the Franck–Condon principle within the configurational-coordinate motel is proposed to exactly determine the lowest excited-state 4f 65d energy in both types of phosphors Eu2-A and Eu2-B. Thermal stability of the phosphor properties is of crucial importance and scientific interest. Therefore, key understandings of the temperature dependences of luminescence intensity and decay time in the Eu2+-activated phosphors are also presented as the additional and important concern in the present review article.

Review—Photoluminescence Spectroscopy of Mn2+-Activated Phosphors: Part I. Fundamentals

“…The same, but for the rare-earth Eu 2+ (4f 7 ↔ 4f 6 5d) inter-configurational transition cases have also been demonstrated in Ref. 58.…”

“…Such a self-absorption effect has been observed in some Eu 2+ -activated phosphors and used for high-performance scintillators. 54,58 An increase in τ with increasing T has also been observed in a 3d 3 (Cr 3+ ) ion-activated phosphor (BeAl 2 O 4 :Cr 3+ ). 54,79 The decay mechanism of this negative TQ in the Cr 3+ ion can be understood by considering the following three-level recombination process:…”

Energy transfer and tunable emission in BaSrGd4O8:Bi3+,Eu3+ phosphors for warm WLED

“…The configurational coordinate model based on the Franck–Condon principle, where the spectral width increases with temperature due to the enhanced thermal vibrations of the crystal, and then the corresponding PL (or PLE) spectral widths can be given by the Huang–Rhys factors S . 32 In addition, the emission curves under different excitations show a redshift (Fig. S5†).…”

“…The emission curve broadens when the temperature increases from 7 to 300 K. The broadening of the spectrum depends on the thermal vibrations of the crystal and the local environment of Bi 3+ , such as symmetry and structural disorder. The configurational coordinate model based on the Franck-Condon principle, where the spectral width increases with temperature due to the enhanced thermal vibrations of the crystal, and then the corresponding PL (or PLE) spectral widths can be given by the Huang-Rhys factors S. 32 In addition, the emission curves under different excitations show a redshift (Fig. S5 †).…”

Europium(ii) bis[tetrafluoro-2-(pentafluoroethoxy)ethanesulfonate] – structure and spectroscopic properties of a new near-UV emitter

“…On the other hand, such systems offer interesting fields of investigation, e.g. phosphors 1 , redox sensitive magnetic resonance imaging contrast agents 2 , luminescence thermometry 3 , search for stable complexes of potential applications in OLEDs 4 , photoredox catalysis 5 and many others. As far as the luminescent properties are concerned, the luminescence of divalent europium complements the red emission of Eu( iii ) compounds with blue or green luminescence.…”