Stacked white OLED having separate red, green and blue sub-elements

• US 8,766,291 B2
• Filed: 10/28/2009
• Issued: 07/01/2014
• Est. Priority Date: 10/28/2008
• Status: Active Grant

• Current Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Original Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Inventors: Forrest, Stephen, Qi, Xiangfei, Slootsky, Michael
• Primary Examiner(s): Soward, Ida M
• Application Number:
  US13/124,698
• Publication Number:
  US 20110248249A1
• Time in Patent Office: 1,707 Days
• Field of Search: 257/40, 257/89, 257/90, 257/E51.022, 257/440, 257/E27.142, 257/E31.121, 257/E31.122, 257/E31.123
• US Class Current: 257/89
• CPC Class Codes: H10K 2101/10 Triplet emission
• CPC Class Codes: H10K 2101/30 Highest occupied molecular orbital [HOMO], lowest unoccupied molecular orbital [LUMO] or Fermi energy values
• CPC Class Codes: H10K 2101/40 Interrelation of parameters between multiple constituent active layers or sublayers, e.g. HOMO values in adjacent layers
• CPC Class Codes: H10K 2102/00 Constructional details relating to the organic devices covered by this subclass
• CPC Class Codes: H10K 2102/103 comprising indium oxides, e.g. ITO
• 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 50/13 comprising stacked EL layers within one EL unit
• CPC Class Codes: H10K 50/19 Tandem OLEDs
• CPC Class Codes: H10K 59/30 Devices specially adapted for multicolour light emission
• CPC Class Codes: H10K 59/32 Stacked devices having two or more layers, each emitting at different wavelengths
• CPC Class Codes: H10K 59/35 comprising red-green-blue [RGB] subpixels

Abstract

The present invention relates to efficient organic light emitting devices (OLEDs). The devices employ three emissive sub-elements, typically emitting red, green and blue, to sufficiently cover the visible spectrum. Thus, the devices may be white-emitting OLEDs, or WOLEDs. Each sub-element comprises at least one organic layer which is an emissive layer—i.e., the layer is capable of emitting light when a voltage is applied across the stacked device. The sub-elements are vertically stacked and are separated by charge generating layers. The charge-generating layers are layers that inject charge carriers into the adjacent layer(s) but do not have a direct external connection.

Claims

1. An organic light emitting device comprising:

a cathode;

a blue-emitting sub-element comprising an emissive layer comprising a phosphorescent blue emissive material;

a charge-generating layer;

a green-emitting sub-element comprising an emissive layer comprising a phosphorescent green emissive material;

a charge-generating layer;

a red-emitting sub-element comprising an emissive layer comprising a phosphorescent red emissive material; and

an anode;

wherein each of the sub-elements has a charge balance factor of about 0.9 to 1,

wherein the emissive layers of each sub-element are within about 20% of the distance to an antinode for that emitter,

wherein each of the sub-elements is separated by a charge-generating layer, and

wherein a combined emission of the emissive materials gives a white emission from the device.

2. The organic light emitting device of claim 1, wherein each of the sub-elements has a charge balance factor of about 0.95 to 1.

3. The organic light emitting device of claim 1, wherein each sub-element comprises a hole transporting layer, an electron transporting layer and the emissive layer, wherein the emissive layer is the hole transporting layer, the electron transporting layer or a separate layer.

4. The organic light emitting device of claim 1, wherein the device emits light having CIE coordinates of X=0.37±

0.08, and Y=0.37±

0.08.

5. The organic light emitting device of claim 1, wherein the device is capable of a maximum external quantum efficiency of at least about 30%.

6. The organic light emitting device of claim 1, wherein the charge-generating layers comprises an n-type layer adjacent to a p-type layer.

7. The organic light emitting device of claim 6, wherein the p-type layers comprise a material selected from MoO₃, V₂O₅, ITO, TiO₂, WO₃ and SnO₂.

8. The organic light emitting device of claim 7, wherein the p-type layers comprise MoO₃.

9. The organic light emitting device of claim 1, wherein at least two of the emissive layers are close enough to an antinode so as to provide at least 90% of its maximum emission.

10. The organic light emitting device of claim 9, wherein each of the emissive layers are close enough to an antinode so as to provide at least 90% of its maximum emission.