Charge injection auxiliary material and organic electroluminescence device containing the same

• US 5,536,949 A
• Filed: 03/15/1994
• Issued: 07/16/1996
• Est. Priority Date: 08/28/1992
• Status: Expired due to Term

• Current Assignee: Idemitsu Kosan Company Limited
• Original Assignee: Idemitsu Kosan Company Limited
• Inventors: Ikeda, Kiyoshi, Hosokawa, Chishio, Kusumoto, Tadashi, Higashi, Hisahiro
• Primary Examiner(s): Crane, Sara W.
• Application Number:
  US08/204,410
• Time in Patent Office: 854 Days
• Field of Search: 257/40, 257/103, 313/504, 313/507, 428/690, 428/917
• US Class Current: 257/40
• 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: H10K 2102/103 comprising indium oxides, e.g. ITO
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/17 Carrier injection layers
• CPC Class Codes: H10K 85/324 comprising aluminium, e.g. Alq3
• CPC Class Codes: H10K 85/60 Organic compounds having low molecular weight H10K85/10 - H10K85/50 take precedence
• CPC Class Codes: H10K 85/615 Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
• CPC Class Codes: H10K 85/622 containing four rings, e.g. pyrene
• CPC Class Codes: H10K 85/623 containing five rings, e.g. pentacene
• CPC Class Codes: H10K 85/626 containing more than one polycyclic condensed aromatic rings, e.g. bis-anthracene
• 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 85/633 comprising polycyclic condensed aromatic hydrocarbons as substituents on the nitrogen atom
• CPC Class Codes: H10K 85/654 comprising only nitrogen as heteroatom H10K85/652 takes precedence
• 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 85/6565 Oxadiazole compounds
• CPC Class Codes: H10K 85/657 Polycyclic condensed heteroaromatic hydrocarbons
• CPC Class Codes: H10K 85/6572 comprising only nitrogen in the heteroaromatic polycondensed ring system, e.g. phenanthroline or carbazole

Abstract

A functional layer, such as a light emitting layer, of an organic electron device, such as an organic electroluminescence device, is provided. The function layer includes a small amount of a charge injection auxiliary material capable of enhancing charge injection properties. The charge injection auxiliary material comprises a stilbene, distyrylarylene or tris(styrylarylene) compound and is employed in an organic electron device wherein a positive-hole transporting organic functional layer is subjected to positive-hole injection from an external layer by incorporating the charge injection auxiliary material in the functional layer. The organic electroluminescence device provided by the present invention has a lowered applied voltage, an enhanced luminous efficiency and a prolonged service life.

Claims

1. A functional layer of an organic electron device, said functional layer comprising a positive-hole transporting organic substance which is subjected to a positive-hole injection from an external layer and has enhanced positive-hole injection properties by incorporation of a charge injection auxiliary material in said functional layer, said charge injection auxiliary material comprising a stilbene, distyrylarylene or tris(styrylarylene) compound, said charge injection auxiliary material being in an amount of 0.05 to 9% by weight based on the weight of the positive-hole transporting organic substance.

2. The functional layer according to claim 1, wherein the functional layer is a light emitting layer, a positive-hole injecting layer, a positive-hole transporting layer or an electron barrier layer.

3. The functional layer according to claim 2, wherein the derivative of stilbene, distyrylarylene or tris(styrylarylene) has at least one electron donating group.

4. The functional layer according to claim 3, wherein the electron donating group is selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, an aryloxy group having 6 to 20 carbon atoms and an amino group with a hydrocarbon radical having 1 to 30 carbon atoms.

5. The functional layer according to claim 1, wherein the charge injection auxiliary material comprises a stilbene derivative of the formula (I) or (II) ##STR39## wherein Ar¹ is an aryl group having 6 to 20 carbon atoms, a thienyl group or a bithienyl group,

R¹ to R⁴ are each a hydrogen atom, an aryl group having 6 to 20 carbon atoms, a thienyl group or a bithienyl group,

R¹ and R² are each the same or different,

R³ and R⁴ are each the same or different,

D¹ to D³ are each an aryl group having 6 to 20 carbon atoms which is substituted with an electron donating group, a thienyl group or a bithienyl group or a condensed polycyclic group having 10 to 30 carbon atoms,

D² and D³ are the same or different, and

Ar¹ and R¹ to R⁴ are each unsubstituted or substituted with an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an arylalkyl group having 7 to 10 carbon atoms or an amino group with a hydrocarbon radical having 1 to 20 carbon atoms.

6. The functional layer according to claim 1 wherein the charge injection auxiliary material comprises a distryrylarylene derivative of the formula (III) or (IV) ##STR40## wherein A² and Ar³ are each an arylene group having 6 to 20 carbon atoms, a thienylene group or a bithienylene group,

Ar⁴ is an aryl group having 6 to 20 carbon atoms, a thienyl group or a bithienyl group,

R⁵ to R¹² are each a hydrogen atom, an aryl group having 6 to 20 carbon atoms, a thienyl group or a bithienyl group,

R⁵ to R⁸ are the same or different;

R⁹ to R¹² are each the same or different,

D⁴ to D⁶ are each a thienyl group, a bithienyl group, a condensed polycyclic group having 10 to 30 carbon atoms or an aryl group having 6 to 20 carbon atoms which is substituted with an electron donating group,

D⁴ and D⁵ are the same or different, and

Ar² to Ar⁴ and R⁵ to R¹² are each unsubstituted or substituted with an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an arylalkyl group having 7 to 10 carbon atoms or an amino group with a hydrocarbon radical having 1 to 20 carbon atoms.

7. The functional layer according to claim 1 wherein the charge injection auxiliary material comprises a tris(styrylarylene) derivative of the formula (V), (VI) or (VII) ##STR41## wherein Ar⁵ to Ar⁷ are each a trivalent aromatic ring radical having 6 to 24 carbon atoms,

Ar⁸ to Ar¹⁰ are each an aryl group having 6 to 20 carbon atoms, a thienyl group or a bithienyl group,

Ar⁹ and Ar¹⁰ are each the same or different,

R¹³ to R³⁰ are each a hydrogen atom, an aryl group having 6 to 20 carbon atoms, a thienyl group or a bithienyl group,

R¹³ to R¹⁸ are each the same or different;

R¹⁹ to R²⁴ are each the same or different;

R²⁵ to R³⁰ are each the same or different;

D⁷ to D¹² are each an aryl group having 6 to 20 carbon atoms which is substituted with an electron donating group, a thienyl group or a bithienyl group or a condensed polycyclic group having 10 to 30 carbon atoms,

D⁷ to D⁹, D¹⁰ and D¹¹ are each the same or different, and

Ar⁵ to Ar¹⁰ and R¹³ to R³⁰ are each unsubstituted or substituted with an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an arylalkyl group having 7 to 10 carbon atoms or an amino group with a hydrocarbon radical having 1 to 20 carbon atoms.

12. The functional layer according to claim 3, wherein the electron donating group is selected from the group consisting of phenoxy group, biphenyloxy group, naphthloxy group, anthranyloxy group, terphenylyloxy group, methoxy group, ethoxy group, isopropoxy group, tert-butyloxy group, pentyloxy group, dimethylamino group, diethylamino group, diphenylamino group, phenylmethylamino group, phenylethylamino group, phenylmethylethylamino group, ditolylamino group, ethylphenylamino group, phenylnaphthylamino group and phenylbiphenylylamino group.

13. The functional layer according to claim 1, wherein the charge injection auxiliary material comprises a compound selected from the group consisting of ##STR42##

14. The functional layer according to claim 1, wherein the charge injection auxiliary material comprises a compound selected from the group consisting of ##STR43##

8. An organic electroluminescence device which comprises an anode, a cathode and disposed therebetween a light emitting layer containing a charge injection auxiliary material, said charge injection auxiliary material having an ionization energy which is smaller than the ionization energy of said light emitting layer, said charge injection auxiliary material comprising a stilbene, distyrylarylene or tris(styrylarylene) derivative, said charge injection auxiliary material being in an amount of 0.05 to 9% by weight based on the weight of the light emitting layer.

9. The organic electroluminescence device according to claim 8, said charge injection auxiliary material has an energy gap which is smaller than the energy gap of the light emitting layer.

10. The organic electroluminescence device according to claim 9, wherein the charge injection auxiliary material is excited by the recombination of positive holes and electrons in the light emitting layer whereby light is emitted.

11. The organic electroluminescence device according to claim 9, wherein the charge injection auxiliary material has an energy gap which is smaller than the energy gap of the light emitting layer by at least 0.1 eV.

15. The organic electroluminescence device according to claim 8, wherein the charge injection auxiliary material is contained in an amount of 0.5 to 5% by weight of the light emitting material.

16. The organic electroluminescence device according to claim 15, wherein the charge injection auxiliary material comprises a compound ##STR44##

17. The organic electroluminescence device according to claim 15, wherein the charge injection auxiliary material comprises a compound ##STR45##

18. A functional layer of an organic electron device, said functional layer comprising a positive-hole transporting organic substance which is subjected to a positive-hole injection from an external layer and has enhanced positive-hole injection properties by incorporation of a charge injection auxiliary material in said functional layer, said charge injection auxiliary material comprising a distyrylarylene or tris(styrylarylene) compound, said charge injection auxiliary material being in an amount of 0.05 to 9% by weight based on the weight of the positive-hole transporting organic substance.