Cascaded light emitting devices based on mixed conductor electroluminescence

• US 8,063,556 B2
• Filed: 01/22/2010
• Issued: 11/22/2011
• Est. Priority Date: 03/28/2005
• Status: Active Grant

• Current Assignee: Cornell Research Foundation Incorporated (Cornell University), Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Cornell Research Foundation Incorporated (Cornell University), Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Abruna, Hector D., Mori, Kiyotaka, Bernards, Daniel A., Slinker, Jason D., Malliaras, George G.
• Primary Examiner(s): Ton; Toan
• Assistant Examiner(s): FAROKHROOZ, FATIMA N
• Application Number:
  US12/691,905
• Publication Number:
  US 20100117518A1
• Time in Patent Office: 669 Days
• Field of Search: 313498-512, 428690-691, 428/917, 438 26- 29, 438/34, 438/82, 427 66532-535, 427/539, 315/169.1, 315/169.3
• US Class Current: 313/505
• CPC Class Codes: H10K 50/135 comprising mobile ions
• CPC Class Codes: H10K 50/19 Tandem OLEDs
• CPC Class Codes: H10K 50/805 Electrodes
• CPC Class Codes: H10K 50/856 comprising reflective means
• CPC Class Codes: H10K 59/32 Stacked devices having two or more layers, each emitting at different wavelengths
• CPC Class Codes: H10K 59/805 Electrodes
• CPC Class Codes: H10K 59/878 comprising reflective means
• CPC Class Codes: H10K 71/841 Applying alternating current [AC] during manufacturing or treatment

Abstract

A cascaded light emitting device. The cascaded light emitting device includes: a base electrode formed of a base electrode material and electrically coupled to a base voltage lead; a top electrode layer formed of a top electrode material and electrically coupled to a top voltage lead; a number of electroluminescent layers arranged between and electrically coupled to the base electrode and top electrode layer; and at least one middle electrode layer formed of a middle electrode material. Each of the middle electrodes is coupled between two juxtaposed electroluminescent layers. The electroluminescent layers include a mixed conductor that luminesces with a peak wavelength.

Claims

1. A cascaded light emitting device, comprising:

a split electrode structure formed of a first electrode material, the split electrode structure including a plurality of separate electrode portions, the plurality of electrode portions including a first electrode portion electrically coupled to a first voltage lead and a second electrode portion electrically coupled to a second voltage lead;

an opposing electrode formed of a second electrode material; and

at least one electroluminescent layer coupled between the split electrode structure and the opposing electrode, the at least one electroluminescent layer including a mixed conductor that luminesces with a peak wavelength, a total thickness of the at least one electroluminescent layer being such that a resistance across the at least one electroluminescent layer between an electrode portion of the split electrode structure and the opposing electrode is less than half of resistance between adjacent electrode portions of the split electrode structure,

wherein the cascaded light emitting device forms a current path from the first electrode portion of the split electrode structure to the opposing electrode and from the opposing electrode to the second electrode portion of the split electrode structure.

2. The cascaded light emitting device according to claim 1, wherein at least one of the first electrode material or the second electrode material is substantially transmissive to light having the peak wavelength.

3. The cascaded light emitting device according to claim 1, wherein one of the split electrode structure or the opposing electrode is formed on a substrate formed of a substrate material that is substantially electrically insulating.

4. The cascaded light emitting device according to claim 1, wherein the opposing electrode forms a substrate of the cascaded light emitting device.

5. The cascaded light emitting device according to claim 1, wherein:

one of the first electrode material or the second electrode material is substantially transmissive to light having the peak wavelength; and

another one of the first electrode material or the second electrode material is substantially reflective to light having the peak wavelength.

6. The cascaded light emitting device according to claim 1, wherein:

the first electrode material includes at least one of a metal conductor, a metal alloy conductor, an oxide conductor, a ceramic conductor, a carbon-based conductor, a polymer conductor, an electrolyte, an ionic conductor, or a composite material formed of a conductor in a non-conducting matrix; and

the second electrode material includes at least one of a metal conductor, a metal alloy conductor, an oxide conductor, a ceramic conductor, a carbon-based conductor, a polymer conductor, an electrolyte, an ionic conductor, or a composite material formed of a conductor in a non-conducting matrix.

7. The cascaded light emitting device according to claim 1, wherein the opposing electrode is electrically coupled to at least one opposing voltage lead.

8. The cascaded light emitting device according to claim 1, wherein the mixed conductor is at least one of a transition metal complex or an ionic liquid.

9. The cascaded light emitting device according to claim 1, further comprising:

at least one middle electrode layer formed of a middle electrode material;

wherein;

the at least one electroluminescent layer is a plurality of electroluminescent layers; and

each middle electrode layer is coupled between two juxtaposed electroluminescent layers of the plurality of electroluminescent layers.

10. The cascaded light emitting device according to claim 2, wherein the one of the split electrode structure or the opposing electrode formed on the substrate and the substrate material are substantially transmissive to light having the peak wavelength.

11. The cascaded light emitting device according to claim 2, wherein the substrate material is substantially reflective to light having the peak wavelength.

12. The cascaded light emitting device according to claim 2, wherein a cover layer formed of a cover material that is substantially electrically insulating is coupled to one of the split electrode structure or the opposing electrode not formed on the substrate.

14. The cascaded light emitting device according to claim 9, wherein the middle electrode material includes at least one of a metal conductor, a metal alloy conductor, an oxide conductor, a ceramic conductor, a carbon-based conductor, a polymer conductor, an electrolyte, an ionic conductor, or a composite material formed of a conductor in a non -conducting matrix.

15. The cascaded light emitting device according to claim 9, wherein the at least one middle electrode layer includes a plurality of middle electrode portions.

16. The cascaded light emitting device according to claim 9, wherein each middle electrode layer includes at least one middle electrode portion that is sized and arranged to:

extend across a separation between two of the plurality of electrode portions of the split electrode structure;

or

substantially overlay one of the plurality of electrode portions of the split electrode structure.

17. The cascaded light emitting device according to claim 15, wherein the at least one middle electrode layer includes a middle electrode portion electrically coupled to a middle voltage lead.

13. A cascaded light emitting device comprising:

a split electrode structure formed of a first electrode material, the split electrode structure including a plurality of separate electrode portions, the plurality of electrode portions including a first electrode portion electrically coupled to a first voltage lead and a second electrode portion electrically coupled to a second voltage lead;

an opposing electrode formed of a second electrode material, the opposing electrode including a plurality of separate opposing electrode portions; and

at least one electroluminescent layer coupled between the split electrode structure and the opposing electrode, the at least one electroluminescent layer including a mixed conductor that luminesces with a peak wavelength, a total thickness of the at least one electroluminescent layer being such that a resistance across the at least one electroluminescent layer between an electrode portion of the split electrode structure and the opposing electrode is less than half of a resistance between adjacent electrode portions of the split electrode structure,

wherein the opposing electrode is sized and arranged such that each of the opposing electrode portions extends across a separation between two of the plurality of electrode portions of the split electrode structure.