Light-emitting element and light emitting device using the same

• US 7,564,052 B2
• Filed: 11/04/2005
• Issued: 07/21/2009
• Est. Priority Date: 11/05/2004
• 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): Pert; Evan
• Assistant Examiner(s): Wilson; Scott R
• Application Number:
  US10/584,333
• Publication Number:
  US 20070170847A1
• Time in Patent Office: 1,355 Days
• Field of Search: 257/13, 257 79-103, 257/918, 257/E51.022, 257/E51.026, 257/40
• US Class Current: 257/40
• CPC Class Codes: H10K 2102/351 Thickness
• CPC Class Codes: H10K 50/00 Organic light-emitting devices integrated devices or assemblies of multiple devices H10K59/00, H10K65/00; organic semiconductor lasers H01S5/36
• CPC Class Codes: H10K 50/17 Carrier injection layers
• CPC Class Codes: H10K 50/171 Electron injection layers
• CPC Class Codes: H10K 50/85 Arrangements for extracting light from the devices
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/131 Interconnections, e.g. wiring lines or terminals
• CPC Class Codes: H10K 59/17 Passive-matrix OLED displays
• CPC Class Codes: H10K 59/875 Arrangements for extracting light from the devices
• CPC Class Codes: H10K 85/30 Coordination compounds
• CPC Class Codes: H10K 85/611 Charge transfer complexes
• CPC Class Codes: H10K 85/636 comprising heteroaromatic hydrocarbons as substituents on the nitrogen atom
• CPC Class Codes: H10K 85/657 Polycyclic condensed heteroaromatic hydrocarbons
• CPC Class Codes: Y10S 257/918 Light emitting regenerative switching device, e.g. light emitting scr arrays, circuitry

Abstract

The present invention provides a light-emitting element having less increase in driving voltage with the accumulation of light-emission time, and provides a light-emitting element having less increase in resistance value with the increase in film thickness. A light-emitting element includes a first layer, a second layer and a third layer between a first electrode and a second electrode. The first layer is provided to be closer to the first electrode than the second layer, and the third layer is provided to be closer to the second electrode than the second layer. The first layer is a layer including an aromatic amine compound and a substance showing an electron accepting property to the aromatic amine compound. The second layer includes a substance of which an electron transporting property is stronger than a hole transporting property, and a substance showing an electron donating property to the aforementioned substance.

Claims

1. A light-emitting element comprising:

a first layer;

a second layer; and

a third layer,

wherein the first, second and third layers are interposed between first and second electrodes which faces to each other;

wherein the first layer includes TPAQn and a first substance showing an electron accepting property to the TPAQn;

wherein the second layer includes a second substance having an electron transporting property higher than a hole transporting property, and a third substance showing an electron donating property to the second substance;

wherein the third layer contains a light-emitting substance;

wherein the first, second and third layers are sequentially stacked;

wherein the first layer is in contact with the first electrode;

wherein the third layer is in contact with the second electrode; and

wherein light is emitted when a voltage is applied such that a potential of the second electrode is higher than that of the first electrode.

2. The light-emitting element according to claim 1,

wherein the first layer includes the first substance such that a molar ratio of the first substance to the TPAQn is 0.5 or more and 2 or less.

3. The light-emitting element according to claim 2,

wherein the third substance is one substance selected from the group consisting of alkali metal oxides and alkali earth metal oxides.

4. A light-emitting device including, in a pixel portion, the light-emitting element according to claim 1.

5. An electronic device using the light-emitting device according to claim 4 for a display portion.

6. An electronic device according to claim 5, wherein the electronic device is one selected from the group consisting of a computer, a telephone and a television.

7. A light-emitting element comprising:

a first layer;

a second layer; and

a third layer,

wherein the first, second and third layers are interposed between first and second electrodes which faces to each other;

wherein the first layer includes a TPAQn and a first substance showing an electron accepting property to the TPAQn;

wherein the second layer includes a second substance having an electron transporting property higher than a hole transporting property, and a third substance showing an electron donating property to the second substance;

wherein the third layer contains a light-emitting substance;

wherein the first layer is provided to be closer to the first electrode than the second layer;

wherein the third layer is provided to be closer to the second electrode than the second layer; and

wherein light is emitted when a voltage is applied such that a potential of the second electrode is higher than that of the first electrode.

8. The light-emitting element according to claim 7,

wherein the first layer includes the first substance such that a molar ratio of the first substance to the TPAQn is 0.5 or more and 2 or less.

9. The light-emitting element according to claim 8,

wherein the third substance is one substance selected from the group consisting of alkali metal oxides and alkali earth metal oxides.

10. A light-emitting device including, in a pixel portion, the light-emitting element according to claim 7.

11. An electronic device using the light-emitting device according to claim 10 for a display portion.

12. An electronic device according to claim 11, wherein the electronic device is one selected from the group consisting of a computer, a telephone and a television.

13. A light-emitting element comprising:

a first layer;

a second layer; and

a third layer,

wherein the first, second and third layers are interposed between first and second electrodes which faces to each other;

wherein the first electrode is formed using a conductive material having a reflectance of 50% or more and 100% or less;

wherein the second electrode is formed using a conductive material which transmits visible light;

wherein the first layer contains a TPAQn and a first substance showing an electron accepting property to the TPAQn;

wherein the second layer contains a second substance having an electron transporting property higher than a hole transporting property, and a third substance showing an electron donating property to the second substance;

wherein the third layer includes x layers (x is a given positive integer) containing a light-emitting layer;

wherein the first, second and third layers are sequentially stacked;

wherein the first layer is in contact with the first electrode;

wherein one layer of the third layer is in contact with the second layer;

wherein an x-th layer in the third layer is in contact with the second electrode;

wherein y-th layer (y≦

x, y is a positive integer) is interposed between the light-emitting layer and the second layer;

wherein light is emitted when a voltage is applied such that a potential of the second electrode is higher than that of the first electrode; and

wherein thicknesses of the first layer and the second layer are adjusted to satisfy expressions 1, 2 and 3;

$\begin{array}{cc}{n}_i<br><br>d_i+n_{\mathrm{ii}}<br><br>d_{\mathrm{ii}}+\underset{k=1}{\overset{y}{\sum <br><br>}}<br><br>n_k<br><br>d_k+n_j<br><br>d_j=\frac{\left(2<br><br>m-1\right)<br><br>\mathrm{\lambda <br><br>}}{4}& 1\\ 0\leqq <br><br>d_j\leqq <br><br>d_{\mathrm{emi}}& 2\\ d_i\geqq <br><br>d_{\mathrm{ii}}& 3\end{array}$

wherein, in the expressions 1, 2 and 3, n_i indicates a refractive index of the first layer;

d_i, a thickness of the first layer;

n_ii, a refractive index of the second layer;

d_ii a thickness of the second layer;

n_k, a refractive index of a k-th layer (k is a natural number) of layers interposed between the light-emitting layer and the second layer;

d_k, a thickness of the k-th layer of the layers interposed between the light-emitting layer and the second layer;

n_j, a refractive index of the light-emitting layer;

d_j, a distance between a surface of the light-emitting layer in the first electrode side and a light-emitting region;

λ

, a wavelength of light emitted from the light-emitting element;

m, a given positive integer; and

d_emi, a thickness of the light-emitting layer.

14. A light-emitting device including, in a pixel portion, the light-emitting element according to claim 13.

15. An electronic device using the light-emitting device according to claim 14 for a display portion.

16. An electronic device according to claim 15, wherein the electronic device is one selected from the group consisting of a computer, a telephone and a television.

17. A light-emitting element comprising:

a first layer;

a second layer; and

a third layer,

wherein the first, second and third layers are interposed between first and second electrodes which faces to each other;

wherein the first layer includes an aromatic amine compound and a first substance showing an electron accepting property to the aromatic amine compound;

wherein the second layer includes a second substance having an electron transporting property higher than a hole transporting property, and a third substance showing an electron donating property to the second substance;

wherein the third layer contains a light-emitting substance;

wherein the first, second and third layers are sequentially stacked;

wherein the first layer is in contact with the first electrode;

wherein the third layer is in contact with the second electrode; and

wherein light is emitted when a voltage is applied such that a potential of the second electrode is higher than that of the first electrode.

18. The light-emitting element according to claim 17,

wherein the first layer includes the first substance such that a molar ratio of the first substance to the aromatic amine compound is 0.5 or more and 2 or less.

19. The light-emitting element according to claim 18,

wherein the third substance is one substance selected from the group consisting of alkali metal oxides and alkali earth metal oxides.

20. A light-emitting device including, in a pixel portion, the light-emitting element according to claim 17.

21. An electronic device using the light-emitting device according to claim 20 for a display portion.

22. An electronic device according to claim 21, wherein the electronic device is one selected from the group consisting of a computer, a telephone and a television.

23. A light-emitting element comprising:

a first layer;

a second layer; and

a third layer,

wherein the first, second and third layers are interposed between first and second electrodes which faces to each other;

wherein the first layer includes an aromatic amine compound and a first substance showing an electron accepting property to the aromatic amine compound;

wherein the second layer includes a second substance having an electron transporting property higher than a hole transporting property, and a third substance showing an electron donating property to the second substance;

wherein the third layer contains a light-emitting substance;

wherein the first layer is provided to be closer to the first electrode than the second layer;

wherein the third layer is provided to be closer to the second electrode than the second layer; and

wherein light is emitted when a voltage is applied such that a potential of the second electrode is higher than that of the first electrode.

24. The light-emitting element according to claim 23,

wherein the first layer includes the first substance such that a molar ratio of the first substance to the aromatic amine compound is 0.5 or more and 2 or less.

25. The light-emitting element according to claim 24,

wherein the third substance is one substance selected from the group consisting of alkali metal oxides and alkali earth metal oxides.

26. A light-emitting device including, in a pixel portion, the light-emitting element according to claim 23.

27. An electronic device using the light-emitting device according to claim 26 for a display portion.

28. An electronic device according to claim 27, wherein the electronic device is one selected from the group consisting of a computer, a telephone and a television.

29. A light-emitting element comprising:

a first layer;

a second layer; and

a third layer,

wherein the first, second and third layers are interposed between first and second electrodes which faces to each other;

wherein the first electrode is formed using a conductive material having a reflectance of 50% or more and 100% or less;

wherein the second electrode is formed using a conductive material which transmits visible light;

wherein the first layer contains an aromatic amine compound and a first substance showing an electron accepting property to the aromatic amine compound;

wherein the second layer contains a second substance having an electron transporting property higher than a hole transporting property, and a third substance showing an electron donating property to the second substance;

wherein the third layer includes x layers (x is a given positive integer) containing a light-emitting layer;

wherein the first, second and third layers are sequentially stacked;

wherein the first layer is in contact with the first electrode;

wherein one layer of the third layer is in contact with the second layer;

wherein an x-th layer in the third layer is in contact with the second electrode;

wherein y-th layer (y≦

x, y is a positive integer) is interposed between the light-emitting layer and the second layer;

wherein light is emitted when a voltage is applied such that a potential of the second electrode is higher than that of the first electrode; and

wherein thicknesses of the first layer and the second layer are adjusted to satisfy expressions 1, 2 and 3;

$\begin{array}{cc}{n}_i<br><br>d_i+n_{\mathrm{ii}}<br><br>d_{\mathrm{ii}}+\underset{k=1}{\overset{y}{\sum <br><br>}}<br><br>n_k<br><br>d_k+n_j<br><br>d_j=\frac{\left(2<br><br>m-1\right)<br><br>\mathrm{\lambda <br><br>}}{4}& 1\\ 0\leqq <br><br>d_j\leqq <br><br>d_{\mathrm{emi}}& 2\\ d_i\geqq <br><br>d_{\mathrm{ii}}& 3\end{array}$

wherein, in the expressions 1, 2 and 3, n_i indicates a refractive index of the first layer;

d_i, a thickness of the first layer;

n_ii, a refractive index of the second layer;

d_ii, a thickness of the second layer;

n_k, a refractive index of a k-th layer (k is a natural number) of layers interposed between the light-emitting layer and the second layer;

d_k, a thickness of the k-th layer of the layers interposed between the light-emitting layer and the second layer;

n_j, a refractive index of the light-emitting layer;

d_j, a distance between a surface of the light-emitting layer in the first electrode side and a light-emitting region;

λ

, a wavelength of light emitted from the light-emitting element;

m, a given positive integer; and

d_emi, a thickness of the light-emitting layer.

30. A light-emitting device including, in a pixel portion, the light-emitting element according to claim 29.

31. An electronic device using the light-emitting device according to claim 30 for a display portion.

32. An electronic device according to claim 31, wherein the electronic device is one selected from the group consisting of a computer, a telephone and a television.