Saturated full color stacked organic light emitting devices

• US 5,932,895 A
• Filed: 05/20/1997
• Issued: 08/03/1999
• Est. Priority Date: 05/20/1997
• Status: Expired due to Term

• Current Assignee: Princeton University
• Original Assignee: The Trustees of Princeton University (Princeton University)
• Inventors: Forrest, Stephen R., Shen, Zilan, Burrows, Paul
• Primary Examiner(s): Tran, Minh Loan
• Application Number:
  US08/858,994
• Time in Patent Office: 805 Days
• Field of Search: 257/40, 257/88, 257/89, 257/98, 257/99, 257/103, 313/503, 313/506
• US Class Current: 257/89
• 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 stacked light emitting device comprising:

a first light emitting device;

a first reflective layer arranged on the first light emitting device, the first reflective layer having a first reflectance;

a second light emitting device arranged over the first reflective layer; and

a second reflective layer arranged over the second light emitting device, the second reflective layer having a second reflectance,

wherein the first and second reflective layers delimit an optical cavity, the optical cavity having a transmittance which dependant on the first and second reflectances and on an optical path length of the optical cavity, and

wherein the optical path length and the first and second reflectances are selected so that the transmittance of the optical cavity has a predetermined characteristic.

2. The device of claim 1, wherein the transmittance of the optical cavity has a filtering characteristic.

3. The device of claim 1, further including a third light emitting device arranged between second light emitting device and the second reflective layer.

4. The stacked light emitting device of claim 3 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.

5. The stacked light emitting device of claim 3 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 stacked light emitting device of claim 3 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.

7. The stacked light emitting device of claim 3 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.

8. The stacked light emitting device of claim 3 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.

9. The stacked light emitting device of claim 3 wherein the optical path length and first and second reflectances are selected to produce an optical cavity that shifts the emission spectrum of the first, second or third light emitting device so as to increase the color saturation of the light produced from the stacked device by the first, second or third light emitting device, respectively.

10. The stacked light emitting device of claim 3 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.

11. The stacked light emitting device of claim 3 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.

12. The stacked light emitting device of claim 3 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.

13. The stacked light emitting device of claim 3 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.

14. The stacked light emitting device of claim 13 wherein the optical cavity has an optical path length of about 475 nm.

15. The stacked light emitting device of claim 3 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.

16. The stacked light emitting device of claim 15 wherein the optical cavity has an optical path length of about 712 nm.

17. The stacked light emitting device of claim 3 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.

18. The stacked light emitting device of claim 17 wherein the optical cavity has an optical path length of about 880 nm.

19. The stacked light emitting device 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 emission spectrum of the first or second light emitting device.

20. The stacked light emitting device 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.

21. The stacked light emitting device 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 emission spectrum of the first light emitting device.

22. The stacked light emitting device 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 emission spectrum of the second light emitting device.

23. The stacked light emitting device of claim 1 wherein the optical path length and first and second reflectances are selected to produce an optical cavity that shifts the emission spectrum of the first light emitting device so as to increase the color saturation of the light produced from the stacked device by the first light emitting device.

24. The stacked light emitting device of claim 1 wherein the optical path length and first and second reflectances are selected to produce an optical cavity that shifts the emission spectrum of the second light emitting device so as to increase the color saturation of the light produced from the stacked device by the second light emitting device.

25. The stacked light emitting device 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.

26. The stacked light emitting device 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.

27. 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 the device of claim 1.