Organic light emitting device

Patent metadata

Field	Value
Publication number	US-9978970-B2
Application number	US-201615195024-A
Country	US
Kind code	B2
Filing date	Jun 28, 2016
Priority date	Sep 30, 2015
Publication date	May 22, 2018
Grant date	May 22, 2018

Abstract

An organic light emitting device including an organic light emitting element having a low driving voltage and a high luminous efficiency is provided. The organic light emitting device includes two or more stack emission units, and a charge generating layer including an N-type charge generating layer and a P-type charge generating layer is disposed between the stack emission units. Herein, the P-type charge generating layer is formed of a material having an LUMO energy level similar to an HOMO energy level of a hole transporting layer injected with holes from the P-type charge generating layer. Accordingly, even if the P-type charge generating layer is not additionally doped with a P-type dopant, it is possible to readily inject holes into a stack emission unit adjacent to the P-type charge generating layer.

First claim

What is claimed is:

1. An organic light emitting device comprising:
a first stack emission unit including a first hole transporting layer, a first emitting layer, and a first electron transporting layer;
a second stack emission unit including a second hole transporting layer, a second emitting layer, and a second electron transporting layer; and
a first charge generating layer between the first stack emission unit and the second stack emission unit,
wherein the first charge generating layer includes an N-type charge generating layer configured to inject electrons into the first stack emission unit and a P-type charge generating layer configured to inject holes into the second stack emission unit,
the P-type charge generating layer and the second hole transporting layer are in direct contact with each other, and
a difference between a lowest unoccupied molecular orbital (LUMO) energy level of the P-type charge generating layer and a highest occupied molecular orbital (HOMO) energy level of the second hole transporting layer is smaller than a difference between a HOMO energy level of the P-type charge generating layer and the HOMO energy level of the second hole transporting layer,
wherein the second hole transporting layer is formed of a material having a lower hole mobility than the first hole transporting layer.

2. The organic light emitting device according to claim 1 , wherein the difference between the LUMO energy level of the P-type charge generating layer and the HOMO energy level of the second hole transporting layer is smaller than ±0.15 eV.

3. The organic light emitting device according to claim 1 , wherein the second hole transporting layer is configured to supply the holes injected from the P-type charge generating layer to the second emitting layer, and
the second emitting layer is configured to emit a yellow-green light.

4. The organic light emitting device according to claim 1 , wherein according to the LUMO energy level of the P-type charge generating layer, electrons are moved from the second hole transporting layer to the P-type charge generating layer.

5. The organic light emitting device according to claim 4 , wherein the P-type charge generating layer is anionized and thus injects holes to the second stack emission unit.

6. The organic light emitting device according to claim 1 , wherein the P-type charge generating layer is not configured as a host-dopant system.

7. The organic light emitting device according to claim 1 , wherein the second stack emission unit is configured to emit a yellow-green light.

8. The organic light emitting device according to claim 7 , wherein the first stack emission unit is configured to emit a blue light.

9. The organic light emitting device according to claim 7 , further comprising:
a third stack emission unit including a third hole transporting layer, a third emitting layer, and a third electron transporting layer; and
a second charge generating layer between the second stack emission unit and the third stack emission unit,
wherein the third stack emission unit is configured to emit a blue light.

10. An organic light emitting device comprising: an organic light emitting element including at least two stack emission units each including a hole transporting layer, an emitting layer, and an electron transporting layer,
wherein at least one charge generating layer disposed between the at least two stack emission units includes an N-type charge generating layer and a P-type charge generating layer which is not doped with a dopant material, and
the P-type charge generating layer is configured to be anionized and thus injects holes into a stack emission unit adjacent to the P-type charge generating layer among the at least two stack emission units,
wherein a hole transporting layer of one stack emission unit adjacent to the P-type charge generating layer is formed of a material having a lower hole mobility than a hole transporting layer of another stack emission unit adjacent to the N-type charge generating layer.

11. The organic light emitting device according to claim 10 , wherein an energy band gap of the P-type charge generating layer is overlapped with an energy band gap of the hole transporting layer included in the stack emission unit adjacent to the P-type charge generating layer.

12. The organic light emitting device according to claim 11 , wherein a highest occupied molecular orbital (HOMO) energy level of the hole transporting layer is lower than a lowest unoccupied molecular orbital (LUMO) energy level of the P-type charge generating layer, and
the LUMO energy level of the P-type charge generating layer is overlapped with the HOMO energy level of the hole transporting layer in the range of less than 0.15 eV.

13. The organic light emitting device according to claim 10 , wherein a difference between an absolute value of a lowest unoccupied molecular orbital (LUMO) energy level of the P-type charge generating layer and an absolute value of a highest occupied molecular orbital (HOMO) energy level of a layer included in the stack emission unit and directly injected with the holes from the P-type charge generating layer is less than 0.15 eV.

14. The organic light emitting device according to claim 1 , wherein an energy band gap of the P-type charge generating layer is overlapped with an energy band gap of the second hole transporting layer.

15. The organic light emitting device according to claim 1 , wherein the material of the first hole transporting layer has a hole mobility between 5.0·10 −5 cm 2 /Vs and 9.0·10 −4 cm 2 /Vs.

16. The organic light emitting device according to claim 1 , wherein the material of the second hole transporting layer has a hole mobility between 5.0·10 −6 cm 2 /Vs and 9.0·10 −5 cm 2 /Vs.

Assignees

• Lg Display Co Ltd

Inventors

• Lee Jaeman
• Yoo Taesun
• Han Mi-Young
• Ahn Soyeon
• Choi Heedong
• Park Jungsoo
• Han Yoondeok

Classifications

• H01L2251/552

  Electricity · mapped topic

• H01L51/5088

  Electricity · mapped topic

• H01L27/3211

  Electricity · mapped topic

• H01L51/5278

  Electricity · mapped topic

• H01L51/5072

  Electricity · mapped topic