Devices to increase OLED output coupling efficiency with a high refractive index substrate

• US 9,640,781 B2
• Filed: 02/26/2015
• Issued: 05/02/2017
• Est. Priority Date: 05/22/2014
• Status: Active Grant

• Current Assignee: Universal Display Corporation
• Original Assignee: Universal Display Corporation
• Inventors: Xiang, Chaoyu, Ma, Ruiqing
• Primary Examiner(s): Ingham, John C
• Application Number:
  US14/631,930
• Publication Number:
  US 20160204381A1
• Time in Patent Office: 796 Days
• CPC Class Codes: H10K 50/805 Electrodes
• CPC Class Codes: H10K 50/85 Arrangements for extracting light from the devices
• CPC Class Codes: H10K 50/852 comprising a resonant cavity structure, e.g. Bragg reflector pair
• CPC Class Codes: H10K 50/86 Arrangements for improving contrast, e.g. preventing reflection of ambient light
• CPC Class Codes: H10K 77/10 Substrates, e.g. flexible substrates
• CPC Class Codes: Y02E 10/549 Organic PV cells

Abstract

Embodiments disclosed herein provide an organic light emitting diode (OLED) device is provided, including a high index substrate having an index of refraction of 1.5 or greater, a reflective electrode, an organic emissive layer configured to emit light having a wavelength of λ; and where an optical distance between the organic emissive layer and the reflective electrode of the OLED is between λ/4 and 3λ/4.

Claims

1. An organic light emitting diode (OLED) device comprising:

a high index substrate having an index of refraction of 1.5 or greater;

a reflective electrode; and

an organic emissive layer configured to emit light having a wavelength of λ

,

wherein an optical distance between the organic emissive layer and the reflective electrode of the OLED is greater than λ

/4 and less than 3λ

/4, and wherein a range of the optical distance between the organic emissive layer and the reflective electrode is selected from the group consisting of;

5% to 50% larger than λ

/4 and 5% to 10% shorter than 3λ

/4.

2. The device of claim 1, wherein λ

is a peak wavelength of an emission spectrum of the emitted light.

3. The device of claim 1, wherein λ

is a shortest wavelength in an emission spectrum of the emitted light.

4. The device of claim 1, wherein the high index substrate comprises a flexible substrate.

5. The device of claim 4, wherein the flexible substrate is plastic.

6. The device of claim 1, wherein the device includes at least one layer from the group consisting of:

a cathode, an electron injection layer (EIL), an electron transport layer (ETL), a hole blocking layer (HBL), a hole transport layer (HTL), a hole injection layer (HIL), an anode, a moisture barrier layer, a gas barrier layer, a planarization layer, and a scattering layer.

7. The device of claim 6, wherein the at least one layer has a high index of refraction that is 1.5 or greater.

8. The device of claim 1, further comprising an outcoupling component to extract the emitted light from the high index substrate.

9. The device of claim 1, wherein the optical distance between the organic emissive layer and the reflective electrode is linearly dependent upon a refractive index of a substrate of the OLED.

10. The device of claim 1, wherein the optical distance between the organic emissive layer and the reflective electrode is linearly dependent upon a shifting factor.

11. The device of claim 1, wherein the optical distance between the organic emissive layer and the reflective electrode is increased by less than 80 nm.

12. The device of claim 1, wherein the optical distance between the organic emissive layer and the reflective electrode is determined by:

D=S*Δ

n+D₀

wherein D is the optical distance, S is a shifting factor, Δ

n is a difference of the substrate index (n) and 1.35, and D₀ is an optical distance at a first antinode condition.

13. The device of claim 1, wherein the optical distance between the organic emissive layer and the reflective electrode of the OLED is according to the respective indices of refraction.

14. The device of claim 1, wherein the high index substrate of the OLED comprises a material selected from the group consisting of:

sapphire, high index glass, plastic, high index polymer, and a polymer and nanoparticle blend.

15. A device comprising:

a high index substrate having an index of refraction of 1.5 or greater;

a transparent first electrode; and

a plurality of layers disposed between the transparent first electrode and a reflective second electrode, the plurality of layers including an organic emissive layer to emit light having a wavelength of λ

, each layer of the plurality of layers having a refractive index n_i and a thickness of d_i,

wherein the optical distance D_opt between the organic emissive layer and the reflective second electrode is defined by D_opt=Σ

(i)n_i*d_i, and

wherein the optical distance between the organic emissive layer and a reflective layer is greater than λ

/4 and less than 3λ

/4, and wherein a range of the optical distance between the organic emissive layer and the reflective electrode is selected from the group consisting of;

5% to 50% larger than λ

/4 and 5% to 10% shorter than 3λ

/4.

16. The device of claim 15, further comprising an outcoupling component to extract the emitted light from the high index substrate.

17. An organic light emitting diode (OLED) device comprising:

an organic emissive layer (EML); and

a reflective electrode,

wherein the overall optical distance D between the EML and the reflective electrode is defined by D=S*Δ

n+D₀,

wherein S is a shifting factor is a positive value between 160nm-180nm, Δ

n is a difference of a substrate index (n) and 1.35, and D₀ is an optical distance at a first antinode condition.

18. The OLED device of claim 17, wherein Δ

n is a positive number greater than 0.15.