CATHODE COATING

• Main Authors: KATHIRGAMANATHAN POOPATHY, SURENDRAKUMAR SIVAGNANASUNDRAM, RAVICHANDRAN SEENIVASAGAM, GANESHAMURUGAN SUBRAMANIAM, CHAN YUN FU
• Format: Patent
• Language: English
• Published: 18.11.2010
• Subjects: APPLYING LIQUIDS OR OTHER FLUENT MATERIALS TO SURFACES, IN GENERAL; ELECTRICITY; PERFORMING OPERATIONS; PROCESSES FOR APPLYING LIQUIDS OR OTHER FLUENT MATERIALS TOSURFACES, IN GENERAL; SPRAYING OR ATOMISING IN GENERAL; TRANSPORTING

Embodiments of electroluminescent devices of the invention are preferably formed of a transparent anode; a layer of a hole transporting material; a layer of an electroluminescent material; a layer of an electron transporting material; a layer of lithium quinolate or of a substituted lithium quinolate e.g. of thickness less than 7 nm; and a metal cathode. The layer of the metal quinolate is preferably about 0.3-0.5 nm in thickness. In an embodiment there is provided an organic light-emitting diode having a cathode, an electron injection layer in contact with the cathode and an electron transport layer in contact with the electron injection layer and comprising aluminium, zirconium or hafnium quinolate or a mixture thereof or a mixture of any of them with a quinolate of a metal of group 1, 2, 3, 13 or 14 of the periodic table, wherein the electron injection layer comprises lithium quinolate or a substituted lithium quinolate having one or more substituents selected from C1-C4 alkyl, monocyclic aryl or aralk-(C1-C4)-yl, aryloxy or fluoro subject to the proviso that not more than one substituent is C2-C4 alkyl, aralkyl or aryloxy or an oligomer thereof, and wherein the electrode is of aluminium. Such devices may be made by a method including the steps of forming lithium quinolate or a substituted lithium quinolate having one or more substituents selected from C1-C4 alkyl, monocyclic aryl or aralk-(C1-C4)-yl, aryloxy or fluoro subject to the proviso that not more than one substituent is C2-C4 alkyl, aralkyl or aryloxy by reacting a lithium alkyl or alkoxide with 8-hydroxyquinoline or a derivative thereof in a solvent comprising acetonitrile, and depositing lithium quinolate or a substituted lithium quinolate formed as described above on a cathode of the device to provide an electron injection layer.