Europium complexes, phosphorescent emission

The first dye used in an electrophosphorescent LED was the terbium-complex Tb(acetyhlacetonate)3 (Tb(acac)3, see Fig. 11.2) [21], LEDs based on complexes with rare-earth central metals such as terbium or europium are very interesting for display applications, because they emit light with a very small spectral line width. These sharp emission lines are due to f-f transitions located on the central metal ion. Disadvantages of these complexes are, however, that color tuning via the chemical modification of the ligand is not possible and that the radiative lifetime of phosphorescence is rather long. 

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