Organic electroluminescent materials and devices

A method for fabricating an organic light emitting device, the method comprising:

• providing a container that contains a first mixture that is an evaporation source for a vacuum deposition process, the first mixture comprising:
• a first compound;
• a second compound;
• and
• a third compound,
• wherein the first compound, the second compound, and the third compound are organic compounds or transition metal complexes and have different chemical structures from each other,
• wherein the first compound, the second compound, and the third compound each has an evaporation temperature T1, T2, and T3, respectively, and is in the range of 150 to 350° C.,
• wherein the T1, T2, and T3 differ from each other by less than 20° C.;
• wherein evaporative properties of the first compound, the second compound, and the third compound are such that:
• when the first compound and the second compound are made into a second mixture in which the first compound has a concentration C1′ and a film is formed by evaporating the second mixture in a container in a high vacuum deposition tool under a first deposition condition which is defined as depositing at a 2 Å/sec deposition rate with a chamber base pressure between 1×10−6 Torr to 1×10−9 Torr onto a surface positioned at a predefined distance from the second mixture, the first compound has a concentration C2′ in the film thus formed;
• and
• when the first compound and the third compound are made into a third mixture in which the first compound has a concentration C1″ and a film is formed by evaporating the third mixture in a container in a high vacuum depostion tool under the first deposition condition onto a surface positioned at a predetermined distance from the third mixture, the first compound has a concentration C2″ in the film thus formed;
• and
• wherein at least one of |(C1′-C2′)/C1′| and |(C1″-C2″)/C1″| is greater than 5%;
• providing a substrate having a first electrode disposed thereon;
• depositing an organic layer over the first electrode by evaporating the first mixture in the container in a high vacuum deposition tool under the first deposition condition,
• wherein the first compound has a concentration C1 in the first mixture and a concentration C2 in the organic layer, wherein |(C1-C2)/C1| is less than 5%;
• and
• depositing a second electrode over the organic layer.