Organic light emitting devices are described wherein the emissive layer comprises a host material containing an emissive molecule, which molecule is adapted to luminesce when a voltage is applied across the heterostructure, and the emissive molecule is selected from the group of phosphorescent organometallic...http://www.google.de/patents/US20070296332?utm_source=gb-gplus-sharePatent US20070296332 - Organometallic complexes as phosphorescent emitters in organic LEDs
