Organic electroluminescent devices having improved power conversion efficiencies

Claim 2

An electroluminescent device comprising, in sequence, an anode electrode, a hole-injecting zone, an organic luminescent zone, said zones have a combined thickness that is no greater than about 1 micron, and a cathode electrode, at least one of said electrodes being capable of transmitting at least 80% of radiation having wavelengths longer than 400 nm, characterised in that said device has a power conversion efficiency of at least 9 X 10 - 5 w/w.

Claim 3

A device as claimed in claim 1, wherein said luminescent zone comprises an electron-transporting compound that provides a maximum electroluminescent quantum efficiency of at least 5 X 10- 4 . photons/electron, when used in a test device driven at no more than the lesser of i) 25 volts and ii) the voltage which produces the maximum power conversion efficiency of said device, said test device comprising 1) a hole-injecting zone consisting essentially of 1,1-bis(4-di-p-tolylaminophenyl)cyclohexane, said hole-injecting zone and said luminescent zone having a combined thickness of no more than 1 micron, 2) an anode electrode that transmits at least 80% of radiation having wavelengths longer than 400 nm, and 3) an indium cathode.

Claim 4

A device as claimed in claim 1 or 2, wherein said electron-transporting compound is an optical brightener.

Claim 5

A device as claimed in claim 3, wherein said optical brightener has the structural formula or wherein R 1 , R 2 , R 3 and R" are individually hydrogen, saturated aliphatic of from 1 to 10 carbon atoms, aryl of from 6 to 10 carbon atoms, or halo, or R 1 and R 2 or R 3 and R 4 taken together comprise the atoms necessary to complete a fused aromatic ring, which may be substituted; R 5 is saturated aliphatic of from 1 to 20 carbon atoms, aryl of from 6 to 10 carbon atoms, carboxyl, hydrogen, cyano or halo; provided that in formula c) at least two of R 3 , R 4 and R 5 are saturated aliphatic of from 3 to 10 carbon atoms; Z is -0-, -NH-, or -S-; Y is n m is an integer of from 0 to 4; n is 0, 1, 2 or 3; R 6 is arylene of from 6 to 10 carbon atoms; R 7 is hydrogen or aryl of from 6 to 10 carbon atoms; and Z' and Z" are individually N or CH, said aliphatic groups being optionally substituted.

Claim 6

A device as claimed in claim 3 or 4 wherein said optical brightener is 4,4'-bis(5,7-di-t-pentyl-2-benzoxazolyl)stilbene; 2,5-bis(5,7-di-t-pentyl-2-benzoxazolyl)-1,3,4-thiadiazole; 2,5-bis(5,7-di-t-pentyl-2-benzoxazolyl)thiophene; 2,2'-p-(phenylenedi- vinylene)bisbenzothiazole; 4,4'-bis(2-benzoxazolyl)-biphenyl; 2,5-bis[5-(a,a-dimethylbenzyl)-2-benzoxazolyl]-thiophene; 4,4'-bis(5,7-di-t-pentyl-2-benzoxazolyl]-stilbene; or 2,5-bis[5,7-di-t-pentyl- 2- benzoxazolyl]-3,4-diphenylthiophene.

Claim 7

A device as claimed in claim 2, wherein said electron-transporting compound is a metal complex of 8-hydroxyquinoline.

Claim 8

A device as claimed in claim 6, wherein the metal of said metal complex is Zn, Al, Mg or Li.

Claim 10

A device as claimed in claim 8, wherein said hole-transporting compound is an amine of which at least one nitrogen atom is trisubstituted with substituents at least one of which is an aryl or substituted aryl group, said amine being solid at room temperature.

Claim 11

A device as claimed in claim 8 or 9, wherein said hole-transporting compound has the structural formula wherein Q 1 and Q 2 are individually moieties containing nitrogen and at least 3 carbocyclic rings at least one of which is aromatic, and G is a linking group or a carbon-to-carbon bond, whereby said hole-transporting compound is thin-film-forming.

Claim 12

A device as claimed in claim 9, wherein said hole-transporting compound is selected from the group consisting of bis(4-dimethylamino-2-methylphenyl)phenylmethane; N,N,N-tri(p-tolyl)amine; 1,1-bis(4-di-p-tolylaminophenyl)cyclohexane; and 1,1-bis(4-di-p-tolylaminophenyl)-4-phenylcyclohexane.

Claim 13

A device as claimed in claim 1 in which the hole-injecting zone comprises 1,1-bis(4-di-p-tolylaminophenyl)cyclohexane; and the luminescent zone comprises 2,5-bis(5,,7-di-t-pentyl-2-benzoxazolyl)-1,3,4-thiadiazole.