Organic electroluminescent device including charge transport buffer layer

• US 6,614,176 B2
• Filed: 03/27/2001
• Issued: 09/02/2003
• Est. Priority Date: 03/27/2000
• Status: Expired due to Term

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung SDI Company Limited
• Inventors: Cho, Sung-woo, Kim, Dong-hyun
• Primary Examiner(s): Patel, Ashok
• Application Number:
  US09/812,936
• Publication Number:
  US 20020027416A1
• Time in Patent Office: 889 Days
• Field of Search: 313/506, 313/503, 313/504, 315/169.3, 428/690, 428/917
• US Class Current: 313/506
• CPC Class Codes: H10K 50/125 specially adapted for multicolour light emission, e.g. for emitting white light
• CPC Class Codes: H10K 85/311 Phthalocyanine
• 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 85/631 Amine compounds having at least two aryl rest on at least one amine-nitrogen atom, e.g. triphenylamine
• CPC Class Codes: Y10S 428/917 Electroluminescent

Abstract

An organic electroluminescent device includes a substrate, and an anode, a hole transport layer, a plurality of light emitting layers, an electron transport layer and a cathode in sequence laminated on the substrate, and a charge transport buffer layer. The charge transport buffer layer adjusts the proportion of excitons generated by two light emitting layers by adjusting a film thickness, and is formed between the light emitting layers. In the organic electroluminescent device, excitons are formed directly on a separate emission region, rather than at the interface between the hole transport layer and the light emitting layers, by forming the charge transport buffer layer between light emitting layers. As a result, lowering of the luminous efficiency is prevented at the interface due to formation of an exciplex. Further, the luminescence ratio of a dichromatic luminous region is adjusted by adjusting the thickness of the charge transport buffer layer, thus easily attaining color tuning.

Claims

1. An organic electroluminescent device comprising:

a substrate, and an anode, a hole transport layer, a plurality of light emitting layers, an electron transport layer and a cathode laminated sequentially on the substrate, wherein a charge transport buffer layer adjusting the proportion of excitons generated by two of the plurality of light emitting layers by adjusting a film thickness, is formed between the light emitting layers.

2. The organic electroluminescent device according to claim 1, wherein the thickness of the charge transport buffer layer is in the range of 10 to 300 Å

.

3. The organic electroluminescent device according to claim 1, wherein the charge transport buffer layer comprises host forming materials of the light emitting layers adjacent thereto.

4. The organic electroluminescent device according to claim 3, wherein the host forming materials of the light emitting layers include N,N′

-Di(naphthalene-1-yl)-N,N′

-diphenyl-benzidine (NPB).

5. The organic electroluminescent device according to claim 1, wherein the charge transport buffer layer comprises host forming materials of the hole transport layer or the electron transport layer.

6. The organic electroluminescent device according to claim 5, wherein the host forming materials of the hole transport layer include N,N′

-Di(naphthalene-1-yl)-N,N′

-diphenyl-benzidine (NPB).

7. The organic electroluminescent device according to claim 1, wherein the host forming materials of the charge transport layer, the light emitting layers and the hole transport layer include N,N′

-Di(naphthalene-1-yl)-N,N′

-diphenyl-benzidine (NPB).

8. The organic electroluminescent device according to claim 1, wherein one or more layers selected from the hole transport layer, the light emitting layers and the electron transport layer comprise 0.1 to 5 wt % of dopant capable of emitting light for hole-electron bonds.

9. The organic electroluminescent device according to claim 8, wherein the dopant is selected from the group consisting of 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-ryran (DCJTB), Coumarin 6, Rubrene, DCM, DCM2, perylene and Quinacridone.

10. The organic electroluminescent device according to claim 8, wherein the content of the dopant is 0.1 to 5 wt % based on the total weight of the hole transport layer, the light emitting layers and the electron transport layer.

11. The organic electroluminescent device according to claim 10, wherein the dopant is selected from the group consisting of 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-ryran (DCJTB), Coumarin 6, Rubrene, DCM, DCM2, perylene and Quinacridone.

12. The organic electroluminescent device according to claim 1, wherein a hole injection layer is further formed between the anode and the hole transport layer.

13. The organic electroluminescent device according to claim 1, wherein an electron injection layer is further formed between the cathode and the electron transport layer.

14. An apparatus comprising:

a substrate;

an anode formed on the substrate;

a hole transport layer formed on the anode;

a first light emitting layer formed on the hole transport layer and comprising an organic compound;

a charge transport buffer layer formed on the first light emitting layer;

a second light emitting layer formed on the charge transport layer and comprising an organic compound;

an electron transport layer formed on the second light emitting layer; and

a cathode formed on the electron transport layer.

15. The apparatus as in claim 14, further comprising:

an electron injection layer formed between the cathode and the electron transport layer; and

a hole injection layer formed between the anode and the hole transport layer.