Organic electroluminescent device

• US 5,093,698 A
• Filed: 02/12/1991
• Issued: 03/03/1992
• Est. Priority Date: 02/12/1991
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Egusa, Syun
• Primary Examiner(s): MINTEL, WILLIAM A
• Application Number:
  US07/654,052
• Time in Patent Office: 385 Days
• Field of Search: 357/17, 357/8, 357/16
• US Class Current: 257/40
• 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 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/155 comprising dopants
• CPC Class Codes: H10K 50/165 comprising dopants
• CPC Class Codes: H10K 71/30 Doping active layers, e.g. electron transporting layers

Abstract

An organic electroluminescent device is constituted by first and second electrodes opposing each other and a multilayered body having a plurality of organic films sandwiched between the electrodes and including an electroluminescent layer. A donor impurity is doped in a first organic film in contact with the first electrode, and an acceptor impurity is doped in a second organic film in contact with the second electrode. A third organic film sandwiched between the first and second organic films serves as an electroluminescent layer. A material having a band gap narrower than those of the first and second organic films is selected as a material of the third organic film so as to confine carriers. No impurity is doped in the third organic film.

Claims

1. An organic electroluminescent device comprising first and second electrodes opposing each other:

a first organic film formed in contact with said first electrode and doped with a donor impurity;

a second organic film formed in contact with said second electrode and doped with an acceptor impurity; and

a third organic film sandwiched between said first and second organic films, serving as an electroluminescent layer, having a band gap narrower than those of said first and second organic films and not doped with an impurity.

2. An organic electroluminescent device according to claim 1, wherein assuming that

a work function of said first electrode is E_M1,

a work function of said second electrode is E_M2,

energy differences of a lower end of a conduction band, a Fermi level, and an upper end of a valence band of said first organic film from a vacuum level are E_C1, E₁, E_V1, respectively,

energy differences of a lower end of a conduction band, a Fermi level, and an upper end of a valence band of said second organic film from a vacuum level are E_C2, E₂, and E_V2, respectively, and

energy differences of a lower end of a conduction band, a Fermi level, and an upper end of a valence band of said third organic film from a vacuum level are E_C3, E₃, E_V3, respectively,

3. An organic electroluminescent device according to claim 2, wherein said first, second, and third organic films satisfy relations of:

space="preserve" listing-type="equation">E.sub.C3 >

E.sub.C1 >

E.sub.C2

space="preserve" listing-type="equation">E.sub.V1 >

E.sub.V2 >

E.sub.V3

4. A organic electroluminescent device according to claim 2, wherein said first, second, and third organic films satisfy relations of:

space="preserve" listing-type="equation">E.sub.V2 ≃

E.sub.V3

space="preserve" listing-type="equation">E.sub.Cl >

E.sub.C3

space="preserve" listing-type="equation">E.sub.C1 -E.sub.C3 <

E.sub.V1 -E.sub.V3

5. An organic electroluminescent device according to claim 2, wherein said first, second, and third organic films satisfy relations of:

space="preserve" listing-type="equation">E.sub.C1 ≃

E.sub.C3

space="preserve" listing-type="equation">E.sub.V2 <

E.sub.V3

space="preserve" listing-type="equation">E.sub.C3 -E.sub.C2 >

E.sub.V3 -E.sub.V2

6. An organic electroluminescent device according to claim 2, wherein an impurity to be doped in said first organic film is a material which satisfies a relation of:

space="preserve" listing-type="equation">Ip-E.sub.C1 <

eV

assuming that an ionization energy of said impurity is Ip.

7. An organic electroluminescent device according to claim 2, wherein an impurity to be doped in said second organic film is an inorganic or organic material which satisfies a relation of:

space="preserve" listing-type="equation">E.sub.V2 -E.sub.A <

1eV

assuming that an electron affinity of said impurity is E_A.

8. An organic electroluminescent device comprising:

a multilayered body constituted by a first organic film not doped with an impurity and serving as an electroluminescent layer, and a second organic film forming a blocking contact with respect to said first organic film and doped with an acceptor impurity;

a first electrode, formed on the first organic film side of said multilayered body, for injecting electrons; and

a second electrode, formed on the second organic film side of said multilayered body, for injecting holes.

9. An organic electroluminescent device according to claim 8, wherein an impurity to be doped in said second organic film is a which satisfies a relation of:

space="preserve" listing-type="equation">E.sub.V2 -E.sub.A <

1 eV

assuming that an electron affinity of said impurity is E_A and an energy difference of an upper end of a valence band of said second organic film from a vacuum level is E_V2.

10. An organic electroluminescent device comprising:

a multilayered body constituted by a first organic film doped with a donor impurity, and a second organic film forming a blocking contact with respect to said first organic film, not doped with an impurity, and serving as an electroluminescent layer;

a first electrode, formed on the first organic film side of said multilayered body, for injecting electrons; and

a second electrode, formed on the second organic film side of said multilayered structure, for injecting holes.

11. An organic electroluminescent device according to claim 10, wherein an impurity to be doped in said first organic film is a material which satisfies a relation of:

space="preserve" listing-type="equation">Ip-E.sub.C1 <

1eV

assuming that an ionization energy of said impurity is Ip and an energy difference of a lower end of a conduction band of said first organic film from a vacuum level is E_C1.