White organic light emitting device

• US 8,963,127 B2
• Filed: 10/22/2010
• Issued: 02/24/2015
• Est. Priority Date: 11/24/2009
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Pieh, Sung-Hoon, Kim, Chang-Oh
• Primary Examiner(s): Nguyen, Ha Tran T
• Assistant Examiner(s): DEHNE, AARON A
• Application Number:
  US12/910,218
• Publication Number:
  US 20110121320A1
• Time in Patent Office: 1,586 Days
• Field of Search: 257/40, 313/504
• US Class Current: 257/40
• 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
• CPC Class Codes: H10K 50/14 Carrier transporting layers

Abstract

A white organic light emitting device having a dual stack structure is disclosed, in which an electron transport layer adjacent to a blue light emitting layer includes an electron transport catalyst layer including metal to improve blue light emitting efficiency, and a greenish yellow dopant is used to improve white display efficiency, increase lifespan, and reduce power consumption.

Claims

1. A white organic light emitting device comprising:

an anode and a cathode facing each other on a substrate;

a charge generation layer formed between the anode and the cathode;

a first stack formed between the anode and the charge generation layer in a stack structure of a first hole transport layer, a first light emitting layer emitting blue, and a first electron transport layer;

a second stack formed between the charge generation layer and the cathode in a stack structure of a second hole transport layer, a second light emitting layer, and a second electron transport layer, the second light emitting layer doped with a phosphor greenish yellow dopant having a single maximum peak wavelength in about 550 nm and a phosphor red dopant having a single maximum peak wavelength in about 610 nm in one host, and the second hole transport layer having an energy level higher than a triplet exciton energy level of the second light emitting layer; and

an electron transport catalyst layer doped with metal oxide between the first electron transport layer and the charge generation layer,

wherein the first electron transport layer is selected from a material that minimizes metal diffusion to the first light emitting layer, and the electron transport catalyst layer is selected from an organic material that enables electron injection through metal doping or metal oxide doping.

2. The white organic light emitting device of claim 1, wherein the second hole transport layer is set to energy level higher than the triplet exciton energy level of the second light emitting layer as much as 0.01˜

0.4 eV.

3. The white organic light emitting device of claim 2, wherein the first hole transport layer is set to energy level higher than a triplet exciton energy level of the first light emitting layer as much as 0.01˜

0.4 eV.

4. The white organic light emitting device of claim 3, wherein the first electron transport layer is set to energy level higher than the triplet exciton energy level of the first light emitting layer as much as 0.01˜

0.4 eV, and the second electron transport layer is set to energy level higher than the triplet exciton energy level of the second light emitting layer as much as 0.01˜

0.4 eV.

5. The white organic light emitting device of claim 1, wherein the electron transport catalyst layer is a bphen based organic material.

6. The white organic light emitting device of claim 1, wherein the metal oxide doped in the electron transport catalyst layer includes at least any one of alkali metal, MoOx, WOx, and V₂O₅.

7. The white organic light emitting device of claim 1, wherein a lowest unoccupied molecular orbital (LUMO) energy level gap between the phosphor greenish yellow dopant and the phosphor red dopant of the second light emitting layer is less than 0.54 eV.

8. The white organic light emitting device of claim 1, wherein the first light emitting layer includes a blue host having a blue dopant that enables fluorescence.

9. A white organic light emitting device comprising:

an anode and a cathode facing each other on a substrate;

a charge generation layer formed between the anode and the cathode;

a first stack formed between the anode and the charge generation layer in a stack structure of a first hole transport layer, a first light emitting layer emitting blue, and a first electron transport layer;

a second stack formed between the charge generation layer and the cathode in a stack structure of a second hole transport layer, a second light emitting layer, and a second electron transport layer, the second light emitting layer doped with first and second phosphor dopants in one host, the first and second phosphor dopants providing an emission spectrum with only two single peaks at, respectively, a wavelength of about 550 nm and a wavelength of about 610, and the second hole transport layer having an energy level higher than a triplet exciton energy level of the second light emitting layer; and

an electron transport catalyst layer doped with metal oxide between the first electron transport layer and the charge generation layer,

wherein the first electron transport layer is selected from a material that minimizes metal diffusion to the first light emitting layer, and the electron transport catalyst layer is selected from an organic material that enables electron injection through metal doping or metal oxide doping.