White light-emitting organic electroluminescence (EL) device and method of adjusting chromaticity of the device

• US 7,812,521 B2
• Filed: 08/05/2008
• Issued: 10/12/2010
• Est. Priority Date: 08/10/2007
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toyota Jidoshokki (Toyota Motor Corporation)
• Original Assignee: Kabushiki Kaisha Toyota Jidoshokki (Toyota Motor Corporation)
• Inventors: Mori, Kenji, Yamamoto, Ichiro, Murasaki, Takanori
• Primary Examiner(s): Patel; Nimeshkumar D
• Assistant Examiner(s): Bowman; Mary Ellen
• Application Number:
  US12/221,763
• Publication Number:
  US 20090079338A1
• Time in Patent Office: 798 Days
• Field of Search: 313/504, 445 24- 25
• US Class Current: 313/504
• CPC Class Codes: H10K 2101/10 Triplet emission
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/125 specially adapted for multicolour light emission, e.g. for emitting white light

Abstract

The white light-emitting organic EL device of the present invention comprises: an anode, a cathode, at least a red light-emitting layer, a blue light-emitting layer and a green light-emitting layer provided between the anode and the cathode, and an intermediate layer between any two adjacent layers of the respective light-emitting layers, wherein, when CIE chromaticity coordinates of a dopant incorporated into the red light-emitting layer are represented by (x_R, y_R), CIE chromaticity coordinates of a dopant incorporated into the blue light-emitting layer are represented by (x_B, y_B), CIE chromaticity coordinates of a dopant incorporated into the green light-emitting layer are represented by (x_G, y_G), and target CIE chromaticity coordinates of white light emitted from the device are represented by (x_t, y_t), Δy represented as a difference between y_R and y_B, and Δx represented as a difference between x_G and x_t satisfy the following relationships:
Δy≦0.18
Δx≦0.10.

Claims

1. A white light-emitting organic EL device, comprising:

an anode;

a cathode;

at least a red light-emitting layer, a blue light-emitting layer, and a green light-emitting layer provided between the anode and the cathode; and

an intermediate layer formed of one of a hole-transporting material, an electron-transporting material, a hole-blocking material, and an electron-blocking material and provided between any two adjacent layers of the respective light-emitting layers,

wherein, when CIE chromaticity coordinates of a material incorporated into the red light-emitting layer responsible for emission of red light are represented by (x_R, y_R), CIE chromaticity coordinates of a material incorporated into the blue light-emitting layer responsible for emission of blue light are represented by (x_B, y_B), CIE chromaticity coordinates of a material incorporated into the green light-emitting layer responsible for emission of green light are represented by (x_G, y_G), and target CIE chromaticity coordinates of white light emitted from the device are represented by (x_t, y_t), Δ

y represented as a difference between y_R and y_B, and Δ

x represented as a difference between x_G and x_t satisfy the following relationships;

Δ

y≦

0.18

Δ

x≦

0.10.

2. A white light-emitting organic EL device according to claim 1, wherein the intermediate layer has a larger energy gap than an energy gap of each of its adjacent light-emitting layers.

3. A white light-emitting organic EL device according to claim 1, wherein at least the red light-emitting layer, the intermediate layer formed of one of the hole-transporting material and the electron-blocking material, the blue light-emitting layer, the green light-emitting layer, and the cathode are provided in this order on the anode.

4. A white light-emitting organic EL device according to claim 1, wherein at least the green light-emitting layer, the intermediate layer formed of one of the hole-transporting material and the electron-blocking material, the blue light-emitting layer, the red light-emitting layer, and the cathode are provided in this order on the anode.

5. A white light-emitting organic EL device according to claim 1, wherein at least the red light-emitting layer, the blue light-emitting layer, the intermediate layer formed of one of the electron-transporting material and the hole-blocking material, the green light-emitting layer, and the cathode are provided in this order on the anode.

6. A white light-emitting organic EL device according to claim 1, wherein at least the green light-emitting layer, the blue light-emitting layer, the intermediate layer formed of one of the electron-transporting material and the hole-blocking material, the red light-emitting layer, and the cathode are provided in this order on the anode.

7. A method of adjusting a chromaticity of a white light-emitting organic EL device which comprises an anode;

a cathode;

at least a red light-emitting layer, a blue light-emitting layer, and a green light-emitting layer provided between the anode and the cathode; and

an intermediate layer formed of one of a hole-transporting material, an electron-transporting material, a hole-blocking material, and an electron-blocking material and provided between any two adjacent layers of the respective light-emitting layers, and in which, when CIE chromaticity coordinates of a material incorporated into the red light-emitting layer responsible for emission of red light are represented by (x_R, y_R), CIE chromaticity coordinates of a material incorporated into the blue light-emitting layer responsible for emission of blue light are represented by (x_B, y_B), CIE chromaticity coordinates of a material incorporated into the green light-emitting layer responsible for emission of green light are represented by (x_G, y_G), and target CIE chromaticity coordinates of white light emitted from the device are represented by (x_t, y_t), Δ

y represented as a difference between y_R and y_B, and Δ

x represented as a difference between x_G and x_t satisfy relationships of Δ

y≦

0.18 and Δ

x≦

0.10,

the method comprising changing, when CIE chromaticity coordinates of the white light emitted from the white light-emitting organic EL device deviate from the target CIE chromaticity coordinates (x_t, y_t), thicknesses of part of the layers selected from the respective light-emitting layers and the intermediate layer so that the white light approaches the target chromaticity value x_t, and thicknesses of part of the layers selected from the remainder of the respective light-emitting layers and the intermediate layer so that the white light approaches the target chromaticity value y_t.

8. A method of adjusting a chromaticity of a white light-emitting organic EL device according to claim 7, wherein:

the white light-emitting organic EL device comprises at least the red light-emitting layer, the intermediate layer formed of one of the hole-transporting material and the electron-blocking material, the blue light-emitting layer, the green light-emitting layer, and the cathode provided in this order on the anode; and

the method comprises changing one of the thickness of the blue light-emitting layer and the thickness ratio between the blue light-emitting layer and the green light-emitting layer so that the white light approaches the target chromaticity value y_t, while changing the thickness of the intermediate layer so that the white light approaches the target chromaticity value x_t.

9. A method of adjusting a chromaticity of a white light-emitting organic EL device according to claim 7, wherein:

the white light-emitting organic EL device comprises at least the green light-emitting layer, the intermediate layer formed of one of the hole-transporting material and the electron-blocking material, the blue light-emitting layer, the red light-emitting layer, and the cathode provided in this order on the anode; and

the method comprises changing the thickness of the intermediate layer so that the white light approaches the target chromaticity value y_t, while changing one of the thickness of the blue light-emitting layer and the thickness ratio between the blue light-emitting layer and the red light-emitting layer so that the white light approaches the target chromaticity value x_t.

10. A method of adjusting a chromaticity of a white light-emitting organic EL device according to claim 7, wherein:

the white light-emitting organic EL device comprises at least the red light-emitting layer, the blue light-emitting layer, the intermediate layer formed of one of the electron-transporting material and the hole-blocking material, the green light-emitting layer, and the cathode provided in this order on the anode; and

the method comprises changing the thickness of the intermediate layer so that the white light approaches the target chromaticity value y_t, while changing one of the thickness of the blue light-emitting layer and the thickness ratio between the blue light-emitting layer and the red light-emitting layer so that the white light approaches the target chromaticity value x_t.

11. A method of adjusting a Chromaticity of a white light-emitting organic EL device according to claim 7, wherein:

the white light-emitting organic EL device comprises at least the green light-emitting layer, the blue light-emitting layer, the intermediate layer formed of one of the electron-transporting material and the hole-blocking material, the red light-emitting layer, and the cathode provided in this order on the anode; and

the method comprises changing one of the thickness of the blue light-emitting layer and the thickness ratio between the blue light-emitting layer and the green light-emitting layer so that the white light approaches the target chromaticity value y_t, while changing the thickness of the intermediate layer so that the white light approaches the target chromaticity value x_t.