Light emitting device

• US 8,008,652 B2
• Filed: 09/09/2005
• Issued: 08/30/2011
• Est. Priority Date: 09/24/2004
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Seo, Satoshi, Kumaki, Daisuke
• Primary Examiner(s): Cao; Phat X
• Application Number:
  US10/582,718
• Publication Number:
  US 20070114544A1
• Time in Patent Office: 2,181 Days
• Field of Search: 257/40, 257/79, 257/E33.016
• US Class Current: 257/40
• CPC Class Codes: H10K 2102/3026 Top emission
• CPC Class Codes: H10K 2102/3031 Two-side emission, e.g. transparent OLEDs [TOLED]
• CPC Class Codes: H10K 2102/351 Thickness
• CPC Class Codes: H10K 50/155 comprising dopants
• CPC Class Codes: H10K 50/157 between the light-emitting layer and the cathode
• CPC Class Codes: H10K 50/165 comprising dopants
• CPC Class Codes: H10K 50/167 between the light-emitting layer and the anode
• CPC Class Codes: H10K 50/852 comprising a resonant cavity structure, e.g. Bragg reflector pair
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 85/324 comprising aluminium, e.g. Alq3
• CPC Class Codes: H10K 85/649 Aromatic compounds comprising a hetero atom

Abstract

An object of the present invention is to provide a light emitting element or a light emitting device that can be formed without any regard for a work function of an electrode. Another object of the invention is to provide a light emitting element or a light emitting device in that the range of choice for a material of an electrode can be widened. In an aspect of the invention, a light emitting device includes first, second and third layers between mutually-facing first and second electrodes. The first layer has a donor level. The second layer is a single layer or a laminated body containing a light emitting substance. The third layer has an acceptor level. When a potential of the second electrode is set higher than that of the first electrode, holes generated in the second layer are injected in the third layer.

Claims

1. A light emitting device comprising:

a first electrode,

a laminated body including a layer containing a light emitting substance over and in direct contact with the first electrode,

a layer having an acceptor level over and in direct contact with the laminated body,

a layer having a donor level over and in direct contact with the layer having the acceptor level, and

a second electrode over and in direct contact with the layer having the donor level,

wherein the layer having the acceptor level comprises both a material with a hole transporting property and a material with an electron accepting property, and

the layer having a donor level comprises both a material with an electron transporting property and a material with an electron donating property.

2. The light emitting device according to claim 1,

wherein the layer having the donor level includes one of tris(8-quinolinolato)aluminum (abbreviation:

Alq₃), bathophenanthroline (abbreviation;

BPhen) and bathocuproin (abbreviation;

BCP).

4. The light emitting device according to claim 1,

wherein when a potential of the second electrode is set higher than a potential of the first electrode, a hole generated in the layer having the acceptor level is injected in the laminated body.

5. The light emitting device according to any one of claims 1 and 3,

wherein the laminated body has a single layer structure.

3. A light emitting device comprising:

a first electrode,

a laminated body including a layer containing a light emitting substance over and in direct contact with the first electrode,

a first layer containing a first substance of which a hole mobility is higher than an electron mobility and a second substance that can accept an electron from the first substance over and in direct contact with the laminated body,

a second layer containing a third substance of which an electron mobility is higher than a hole mobility and a forth substance that can donate an electron to the third substance over and in direct contact with the first layer, and

a second electrode in direct contact with the second layer.

6. The light emitting device according to claim 3,

wherein the third substance is one of tris(8-quinolinolato)aluminum (abbreviation:

Alq₃), bathophenanthroline (abbreviation;

BPhen) and bathocuproin (abbreviation;

BCP).

7. The light emitting device according to claim 3,

wherein when a potential of the second electrode is set higher than a potential of the first electrode, a hole generated in the first layer is injected in the laminated body.