Saturated full color stacked organic light emitting devices

• US 6,232,714 B1
• Filed: 04/14/1999
• Issued: 05/15/2001
• Est. Priority Date: 05/20/1997
• Status: Expired due to Term

• Current Assignee: The Trustees of Princeton University (Princeton University)
• Original Assignee: The Trustees of Princeton University (Princeton University)
• Inventors: Forrest, Stephen R., Shen, Zilan, Burrows, Paul
• Primary Examiner(s): Patel, Nimeshkumar D.
• Assistant Examiner(s): Smith, Michael J.
• Application Number:
  US09/291,188
• Time in Patent Office: 762 Days
• Field of Search: 313/506, 313/501, 313/503, 313/509, 257/89, 257/98, 257/103, 427/162, 445/24
• US Class Current: 313/506
• CPC Class Codes: H10K 50/125 specially adapted for multicolour light emission, e.g. for emitting white light
• CPC Class Codes: H10K 50/85 Arrangements for extracting light from the devices
• CPC Class Codes: H10K 59/32 Stacked devices having two or more layers, each emitting at different wavelengths
• CPC Class Codes: H10K 59/876 comprising a resonant cavity structure, e.g. Bragg reflector pair

Abstract

Optical cavities in a stacked organic light emitting device (SOLEDs) can shift or attenuate the light emitted by the individual organic light emitting devices (OLEDs) in the stack. Interference caused by reflections within the stack, absorption, positioning of the light source, and the polarization of the emitted light can all determine how the spectra of the emitted light are affected by the SOLED structure. A detailed model that provides a good fit to measured SOLED emissions can be used to predict how a SOLED will affect light emitted by OLEDs. As a result, SOLED geometries that will optimize color saturation and external quantum efficiency can be predicted.

Claims

1. A method of creating a stacked light emitting device that emits desired spectra of light, comprising the steps of:

selecting a first light emitting device that emits a first emission spectrum;

selecting a second light emitting device that emits a second emission spectrum;

for an optical cavity having an optical path length, the optical cavity being delimited by a first reflective layer having a first reflectance and a second reflective layer having a second reflectance, selecting the optical path length, the first reflectance, and the second reflectance such that the optical cavity filters the second emission spectrum of the second light emitting device, disposed between the first reflective layer and the second reflective layer, into a first transmitted spectrum; and

fabricating a stacked light emitting device comprising the first light emitting device and the second light emitting device and having the optical cavity, wherein the second light emitting device is disposed between the first reflective layer and the second reflective layer of the optical cavity.

2. The method of claim 1, further comprising the step of selecting a third light admitting device that emits a third emission spectrum;

wherein the optical path length, the first reflectance, and the second reflectance are further selected such that the optical cavity filters the third emission spectrum of the third light emitting device, disposed between the first reflective layer and the second reflective layer, into a second transmitted spectrum; and

wherein the stacked light emitting device further comprises the third light emitting device, disposed between the first reflective layer and the second reflective layer of the optical cavity having the determined optical path length.

3. The method of claim 2, wherein the stacked light emitting device further comprises one or more additional light emitting devices.

4. The method of claim 1 wherein the optical path length and first and second reflectances are selected to produce an optical cavity having a transmission peak centered on the first or second emission spectrum.

5. The method of claim 1 wherein the optical path length and first and second reflectances are selected to produce an optical cavity having a transmission peak centered at about 475, 500, 530 or 670 nm.

6. The method of claim 1 wherein the optical path length and first and second reflectances are selected to produce an optical cavity having a transmission peak having no overlap with the first emission spectrum.

7. The method of claim 1 wherein the optical path length and first and second reflectances are selected to produce an optical cavity having a transmission peak having no overlap with the second emission spectrum.

8. The method of claim 1 wherein the optical path length and first and second reflectances are selected such that the first transmitted spectrum is more saturated than the second emission spectrum.

9. The method of claim 2 wherein the optical path length and first and second reflectances are selected such the second transmitted spectrum is more saturated than the third emission spectrum.

10. The method of claim 1 wherein the optical path length and first and second reflectances are selected to produce an optical cavity that maximizes the external quantum efficiency of the first or second light emitting device.

11. The method of claim 1 wherein the optical path length and first and second reflectances are selected to produce an optical cavity that minimizes the shift in wavelength of the transmitted light with viewing angle of the light obtained from the first or second light emitting device.

12. The method of claim 2 wherein the optical path length and first and second reflectances are selected to produce an optical cavity having a transmission peak centered on the emission spectrum of the first, second or third light emitting device.

13. The method of claim 2 wherein the optical path length and first and second reflectances are selected to produce an optical cavity having a transmission peak centered at about 475, 500, 530 or 670 nm.

14. The method of claim 2 wherein the optical path length and first and second reflectances are selected to produce an optical cavity having a transmission peak having no overlap with the emission spectrum of the first light emitting device.

15. The method of claim 2 wherein the optical path length and first and second reflectances are selected to produce an optical cavity having a transmission peak having no overlap with the emission spectrum of the second light emitting device.

16. The method of claim 2 wherein the optical path length and first and second reflectances are selected to produce an optical cavity having a transmission peak having no overlap with the emission spectrum of the third light emitting device.

17. The method of claim 2 wherein the optical path length and first and second reflectances are selected to produce an optical cavity that maximizes the external quantum efficiency of the first, second or third light emitting device.

18. The method of claim 2 wherein the optical path length and first and second reflectances are selected to produce an optical cavity that minimizes the shift in wavelength of the transmitted light with viewing angle of the light obtained from the first, second or third light emitting device.

19. The method of claim 2 wherein the first light emitting device emits blue light, the second light emitting device emits green light and the third light emitting device emits red light, wherein the optical cavity has an optical path length of about 530 nm.

20. The method of claim 2 wherein the first light emitting device emits green light, the second light emitting device emits blue light and the third light emitting device emits red light.

21. The method of claim 20 wherein the optical cavity has an optical path length of about 475 nm.

22. The method of claim 2 wherein the first light emitting device emits green light, the second light emitting device emits red light and the third light emitting device emits blue light.

23. The method of claim 22 wherein the optical cavity has an optical path length of about 712 nm.

24. The method of claim 2 wherein the first light emitting device emits blue light, the second light emitting device emits red light and the third light emitting device emits green light.

25. The method of claim 24 wherein the optical cavity has an optical path length of about 880 nm.

26. An apparatus selected from the group consisting of:

a display, a vehicle, a television, a computer, a printer, a screen, a sign, a telecommunications device, and a telephone, wherein the apparatus incorporates a device fabricated in accordance with claim 1.