Patent ID: 7531377

Claim:
A method of forming an optical device comprising the steps of: providing a substrate comprising a first electrode capable of injecting or accepting charge carriers of a first type; forming over the first electrode a first layer that is at least partially insoluble in a solvent by depositing a first semiconducting material that is free of cross-linkable vinyl or ethynyl groups and is, at the time of deposition, soluble in the solvent; forming a second layer in contact with the first layer by depositing a second semiconducting material from a solution in the solvent; forming over the second layer a second electrode capable of injecting or accepting charge carriers of a second type; and subjecting the first layer to one or more of heat treatment, vacuum treatment and ambient drying treatment in order to render the first layer at least partially insoluble wherein at least one of the first and second semiconducting materials is a polyfluorene comprising optionally substituted repeat units of formula (I): wherein R and R′ are selected from hydrogen or optionally substituted alkyl, alkoxy, aryl, arylalkyl, heteroaryl and heteroarylalkyl, and at least one of R and R′ comprises an optionally substituted C 4 -C 20 alkyl group.