Organic electroluminescent devices having improved power conversion efficiencies

• US 4,539,507 A
• Filed: 03/25/1983
• Issued: 09/03/1985
• Est. Priority Date: 03/25/1983
• Status: Expired due to Term

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Tang, Ching W., VanSlyke, Steven A.
• Primary Examiner(s): Moore, David K.
• Assistant Examiner(s): Wieder, K.
• Application Number:
  US06/478,938
• Time in Patent Office: 893 Days
• Field of Search: 313/498, 313/499, 313/503, 313/504, 313/506, 313/509, 252/511, 252/301.16, 252/301.21, 252/301.27, 252/301.28, 357/8, 357/61, 428/515
• US Class Current: 313/504
• CPC Class Codes: C09K 11/06 containing organic luminescent materials
• CPC Class Codes: H05B 33/14 characterised by the chemical or physical composition or the arrangement of the electroluminescent material , or by the simultaneous addition of the electroluminescent material in or onto the light source
• CPC Class Codes: H05B 33/22 characterised by the chemical or physical composition or the arrangement of auxiliary dielectric or reflective layers
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 85/30 Coordination compounds
• CPC Class Codes: H10K 85/324 comprising aluminium, e.g. Alq3
• CPC Class Codes: H10K 85/631 Amine compounds having at least two aryl rest on at least one amine-nitrogen atom, e.g. triphenylamine
• CPC Class Codes: H10K 85/652 Cyanine dyes
• CPC Class Codes: H10K 85/655 comprising only sulfur as heteroatom
• CPC Class Codes: H10K 85/656 comprising two or more different heteroatoms per ring H10K85/652 takes precedence
• CPC Class Codes: H10K 85/657 Polycyclic condensed heteroaromatic hydrocarbons

Abstract

Electroluminescent devices are disclosed comprising a hole-injecting zone and an adjacent organic luminescent zone, the device having a power conversion efficiency of at least 9×10^-5 w/w and said zones having a combined thickness no greater than about 1 micron.

Claims

1. In an electroluminescent device comprising, in sequence, an anode electrode, a hole-injecting zone, an organic luminescent zone, 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,

the improvement wherein said luminescent zone comprises an electron-transporting compound that provides a maximum electroluminescent quantum efficiency of at least about 5×

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,

and wherein said device has a power conversion efficiency of at least 9×

10^-5 w/w and said zones have a combined thickness that is no greater than about 1 micron.

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

3. A device as defined in claim 2, wherein said optical brightener has a structural formula selected from the class consisting of ##STR26## wherein (1) R¹, R², R³ and R⁴ are individually hydrogen, saturated aliphatic of from 1 to 10 carbon atoms, aryl of from 6 to 10 carbon atoms, or halo, or (2) R¹ and R² or R³ and R⁴ taken together comprise the atoms necessary to complete a fused aromatic ring;

R⁵ 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 (b) at least two of R³, R⁴ and R⁵ are saturated aliphatic of from 3 to 10 carbon atoms;

Z is --O--, --NH--, or --S--;

Y is ##STR27## m is an integer of from 0 to 4;

n is 0, 1, 2 or 3;

R⁶ is arylene of from 6 to 10 carbon atoms; and

Z'"'"' and Z" are individually N or CH.

4. A device as defined in claim 2, wherein said optical brightener is selected from the group consisting of 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-phenyl-2-benzoxazolyl)thiophene;

2,2'"'"'-p-(phenylenedivinylene)bisbenzothiazole;

4,4'"'"'-bis(2-benzoxazolyl)biphenyl;

2,5-bis[5-(α

,α

-dimethylbenzyl)-2-benzoxazolyl]-thiophene;

4,4'"'"'-bis[5,7-di-(2-methyl-2-butyl)-2-benzoxazolyl]-stilbene; and

2,5-bis[5,7-di-(2-methyl-2-butyl)-2-benzoxazolyl]-3,4-diphenylthiophene.

5. A device as defined in claim 1, wherein said electron-transporting compound is a metal complex of 8-hydroxyquinoline.

6. A device as defined in claim 5, wherein the metal of said metal complex is selected from the group consisting of Zn, Al, Mg and Li.

7. In an electroluminescent device comprising, in sequence, an anode electrode, a hole-injecting zone, an organic luminescent zone, 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, the improvement wherein said hole-injecting zone comprises an amine that transmits at least about 90% of radiation having wavelengths greater than 400 nm, at least one nitrogen atom of the amine being trisubstituted with substituents at least one of which is aryl, said amine being solid at room temperature and having the structural formula ##STR28## wherein Q¹ and Q² 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 amine is thin-film-forming.

8. In an electroluminescent device comprising, in sequence, an anode electrode, a hole-injecting zone, an organic luminescent zone, 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, the improvement wherein said hole-injecting zone comprises an amine 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.

9. In an electroluminescent device comprising, in sequence, an anode electrode, a hole-injecting zone, an organic luminescent zone, 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,

the improvement wherein said hole-injecting zone comprises 1,1-bis(4-di-p-tolylaminophenyl)cyclohexane;

and said luminescent zone comprises 2,5-bis(5,7-di-t-pentyl-2-benzoxazolyl)-1,3,4-thiadiazole;

said two zones having a combined thickness no greater than about 1 micron.