Trivalent europium (Eu(III)) complexes are expected to be used as light-emitting materials such as organic light emitting diodes (OLEDs) because of their high color purity. The complexes are sensitized by the antenna effect, utilizing energy transfer from antenna ligands to a metal center. In the emitting layer of OLEDs, guest emitters are doped in host molecules, and intermolecular energy transfer also occurs. [more]