Method of fabricating transparent contacts for organic devices

• US 6,264,805 B1
• Filed: 06/10/1997
• Issued: 07/24/2001
• Est. Priority Date: 12/13/1994
• Status: Expired due to Term

• Current Assignee: The Trustees of Princeton University (Princeton University)
• Original Assignee: The Trustees of Princeton University (Princeton University)
• Inventors: Burrows, Paul E., Forrest, Stephen R., Bulovic, Vladimir, Thompson, Mark E., Gu, Gong
• Primary Examiner(s): Nguyen, Nam
• Assistant Examiner(s): ANTHONY, JULIAN
• Application Number:
  US08/872,560
• Time in Patent Office: 1,505 Days
• Field of Search: 204/192.26, 204/192.27, 204/192.28, 204/192.29, 427/585, 427/68, 427/69, 427/70, 427/75, 427/78, 427/525, 427/529, 427/531, 427/255.6
• US Class Current: 204/192.26
• CPC Class Codes: C09K 11/06 containing organic luminescent materials
• CPC Class Codes: G09F 9/335 being organic light emitting diodes [OLED]
• CPC Class Codes: H01L 2224/24145 the bodies being stacked
• CPC Class Codes: H01L 27/156 two-dimensional arrays
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/01021 Scandium [Sc]
• CPC Class Codes: H01L 2924/01068 Erbium [Er]
• CPC Class Codes: H01L 2924/12041 LED
• CPC Class Codes: H01L 2924/12044 OLED
• CPC Class Codes: H10K 2102/3031 Two-side emission, e.g. transparent OLEDs [TOLED]
• 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 50/14 Carrier transporting layers
• CPC Class Codes: H10K 50/828 Transparent cathodes, e.g. comprising thin metal layers
• CPC Class Codes: H10K 50/8423 Metallic sealing arrangements
• CPC Class Codes: H10K 50/8426 Peripheral sealing arrangements, e.g. adhesives, sealants
• CPC Class Codes: H10K 50/844 Encapsulations
• CPC Class Codes: H10K 59/32 Stacked devices having two or more layers, each emitting at different wavelengths
• CPC Class Codes: H10K 59/80524 Transparent cathodes, e.g. comprising thin metal layers
• CPC Class Codes: H10K 59/8721 Metallic sealing arrangements
• CPC Class Codes: H10K 59/8722 : Peripheral sealing arrangements, e.g. adhesives, sealants
• CPC Class Codes: H10K 59/873 : Encapsulations
• CPC Class Codes: H10K 85/10 : Organic polymers or oligomers
• CPC Class Codes: H10K 85/111 : comprising aromatic, heteroaromatic, or aryl chains, e.g. polyaniline, polyphenylene or polyphenylene vinylene
• CPC Class Codes: H10K 85/113 : Heteroaromatic compounds comprising sulfur or selene, e.g. polythiophene
• CPC Class Codes: H10K 85/114 : Poly-phenylenevinylene; Derivatives thereof
• CPC Class Codes: H10K 85/146 : poly N-vinylcarbazol; Derivatives thereof
• CPC Class Codes: H10K 85/30 : Coordination compounds
• CPC Class Codes: H10K 85/322 : comprising boron
• CPC Class Codes: H10K 85/324 : comprising aluminium, e.g. Alq3
• CPC Class Codes: H10K 85/341 : Transition metal complexes, e.g. Ru(II)polypyridine complexes H10K85/331 takes precedence
• CPC Class Codes: H10K 85/60 : Organic compounds having low molecular weight H10K85/10 - H10K85/50 take precedence
• CPC Class Codes: H10K 85/611 : Charge transfer complexes
• CPC Class Codes: H10K 85/631 : Amine compounds having at least two aryl rest on at least one amine-nitrogen atom, e.g. triphenylamine

Abstract

A multicolor organic light emitting device employs vertically stacked layers of double heterostructure devices which are fabricated from organic compounds. The vertical stacked structure is formed on a glass base having a transparent coating of ITO or similar metal to provide a substrate. Deposited on the substrate is the vertical stacked arrangement of three double heterostructure devices, each fabricated from a suitable organic material. Stacking is implemented such that the double heterostructure with the longest wavelength is on the top of the stack. This constitutes the device emitting red light on the top with the device having the shortest wavelength, namely, the device emitting blue light, on the bottom of the stack. Located between the red and blue device structures is the green device structure. The devices are configured as stacked to provide a staircase profile whereby each device is separated from the other by a thin transparent conductive contact layer to enable light emanating from each of the devices to pass through the semitransparent contacts and through the lower device structures while further enabling each of the devices to receive a selective bias. The devices are substantially transparent when de-energized, making them useful for heads-up display applications.

Claims

1. A method of fabricating a multicolor light emitting device (LED) structure that is substantially transparent when de-energized, comprising the steps of:

forming a first transparent conductive layer upon a transparent substrate;

depositing a substantially transparent first hole transporting layer upon said first transparent conductive layer;

depositing a substantially transparent first organic emission layer upon said first hole transporting layer to provide a first emission color;

depositing via vapor deposition a substantially transparent first electron transporting layer upon said first organic emission layer;

depositing via sputtering a second transparent conductive layer upon said first electron transporting layer, said second transparent conductive layer adapted to receive a first bias potential;

depositing a substantially transparent second hole transporting layer upon said second transparent conductive layer;

depositing a substantially transparent second organic emission layer upon said second hole transporting layer to provide a second emission color;

depositing via vapor deposition a substantially transparent second electron transporting layer upon said second organic emission layer; and

depositing via sputtering a third transparent conductive layer upon said second electron transporting layer, said third transparent conductive layer adapted to receive a second bias potential.

2. The method of claim 1, further including the step of shadow masking a region of said first transparent conductive layer prior to depositing said first hole transporting layer to expose said region of said first transparent conductive layer thereby enabling said first bias potential to be applied between said second transparent conductive layer and said region of said first transparent conductive layer.

3. The method of claim 1, further including the step of etching away a region of said first hole transporting layer to expose a portion of said first transparent conductive layer thereby enabling said first bias potential to be applied between said second transparent conductive layer and said exposed portion of said first transparent conductive layer.

4. The method of claim 1, wherein said steps of vapor deposition for depositing the substantially transparent first electron transporting layer upon said first organic emission layer, and the substantially transparent second electron transporting layer upon said second organic emission layer, each include:

placing said substrate into a vacuum chamber with one of the first and second organic emission layers to be coated exposed on said substrate;

selecting a metal or metal alloy for placement in said chamber to be deposited on one of said first and second organic emission layers as an electron transporting layer;

reducing the pressure in said vacuum chamber to about 1×

10<sup>−

6</sup> Torr;

melting the metal or metal alloy to produce a desired deposition rate for vapor depositing the metal or metal alloy on the exposed one of said first and second organic layers;

monitoring the thickness of said metal or metal alloy being deposited; and

blocking the deposition of the vaporized metal or metal alloy to the one of said first and second organic emission layers when a desired thickness is reached.

5. The method of claim 4, wherein said steps of depositing via sputtering a second transparent conductive layer upon said first electron transporting layer, and a third transparent conductive layer upon said second electron transporting layer, each include the steps of:

placing said substrate into a load lock chamber with respectively one of the first and second electron transporting layers to respectively receive a second or third conductive layer, exposed;

reducing the pressure in said load lock chamber to 1×

10<sup>−

7</sup> Torr;

transferring the substrate under vacuum from said load lock chamber into a sputtering chamber;

positioning said substrate over a sputtering target;

establishing a flowrate of argon gas into said sputtering chamber;

establishing a flowrate of oxygen into said sputtering chamber;

maintaining the pressure in said sputtering chamber at 20 mTorr;

establishing a level of RF power and impedance matching for igniting a plasma to begin the sputtering of material from said target to an exposed one of said first and second electron transporting layer, by placing a target shutter in an open position;

slowly reducing the level of RF power to a minimum level for sustaining ignition of said plasma; and

closing said target shutter after sputter depositing a required thickness of the second or third transparent conductive layer.

6. The method of claim 5, wherein the flowrate of argon gas is established at about 200 sccm.

7. The method of claim 4, wherein said first and second electron transporting layers are each formed from a metal alloy of Mg:

Ag.

8. The method of claim 7, wherein said melting step includes the steps of:

establishing a deposition rate for the Ag at 0.1 Å

/s; and

establishing a deposition rate for the Mg at 5 Å

/s.

9. The method of claim 5, wherein the flowrate of oxygen is established at 0.1 sccm.