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WO1999060599A1 - An improved electrode structure for organic light emitting diode devices - Google Patents

An improved electrode structure for organic light emitting diode devices Download PDF

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Publication number
WO1999060599A1
WO1999060599A1 PCT/US1999/003900 US9903900W WO9960599A1 WO 1999060599 A1 WO1999060599 A1 WO 1999060599A1 US 9903900 W US9903900 W US 9903900W WO 9960599 A1 WO9960599 A1 WO 9960599A1
Authority
WO
WIPO (PCT)
Prior art keywords
electrode
light emitting
work function
emitting diode
organic light
Prior art date
Application number
PCT/US1999/003900
Other languages
French (fr)
Inventor
Gary W. Jones
Webster E. Howard
Original Assignee
Fed Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fed Corporation filed Critical Fed Corporation
Priority to KR1020007012865A priority Critical patent/KR20010071276A/en
Priority to EP99909560A priority patent/EP1088320A1/en
Priority to JP2000550128A priority patent/JP2002516459A/en
Publication of WO1999060599A1 publication Critical patent/WO1999060599A1/en

Links

Classifications

    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B33/00Electroluminescent light sources
    • H05B33/12Light sources with substantially two-dimensional radiating surfaces
    • H05B33/26Light sources with substantially two-dimensional radiating surfaces characterised by the composition or arrangement of the conductive material used as an electrode
    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10KORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00Organic light-emitting devices
    • H10K50/10OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/17Carrier injection layers

Definitions

  • the present invention relates to electrode structures for an organic light emitting diode (OLED) device.
  • the present invention relates to an improved anode structure for an OLED device.
  • Fig. 1 discloses a known OLED device 10.
  • the OLED device 10 includes a glass substrate 11.
  • a transparent hole-injecting anode or electrode 12 formed of indium-tin oxide (ITO) is located on the glass substrate 11.
  • An organic stack 13 is located on the anode 12.
  • the anode 12 forms the first or bottom layer of the stack 13.
  • a metal cathode 14 is located on top of the organic stack 13. In the device 10, light is emitted in a downward direction through the electrode 12 and the glass substrate 11.
  • ITO indium-tin oxide
  • OLED require two electrodes, an anode 12 and a cathode 14, at least one of which must be transparent to allow light to escape.
  • the anode 12, which must supply holes to the emitting region, is usually formed from a material with high work function, since this will lead to a low energy for hole injection.
  • the cathode 14, which must supply electrons to the emitting region, is usually formed from a material with low work function, which will facilitate electron injection.
  • ITO Indium tin oxide
  • ITO injection efficiency of ITO, and consequently the luminescent efficiency of the OLED, is enhanced by pretreating the ITO with an oxygen plasma, which ensures that there is an excess of oxygen at the interface with the organic stack 13.
  • the excess of oxygen appears to contribute to the instability of such OLEDs because the oxygen can migrate and react with the organic materials.
  • ITO has also been used in conjunction with thin metal interlayers to form cathode contacts, where the thin metal is of a low work function material to provide electron injection.
  • the present invention is directed to an improved organic light emitting diode device.
  • the organic light emitting diode device includes a first electrode, a second electrode, and an
  • stack may include hole transport materials located on one side of the stack and electron
  • the improvement includes a thin
  • the organic light emitting diode device according to the present invention has
  • the thin layer of high work function material may be formed from a material selected
  • the thin layer of high work function is selected from the group consisting of Mo and alloys of Mo.
  • the thin layer of high work function is selected from the group consisting of Mo and alloys of Mo.
  • material may be formed from a material selected from the group consisting of W and alloys
  • the thin layer of high work function material may be formed from a
  • thin layer of the high work function material may have a thickness of less than 100 A.
  • the first electrode may be a transparent electrode and the second electrode may be
  • the second electrode may be formed from a low work function material.
  • the present invention is also directed to an improved electrode structure for an
  • the electrode may comprise an electrode layer, and a thin
  • the thin layer of a high work function material located adjacent the electrode layer.
  • high work function material may be formed from a material selected from the group
  • the thin layer of high work function material may be any material consisting of Mo and alloys of Mo.
  • the thin layer of high work function material may be any material consisting of Mo and alloys of Mo.
  • layer of high work function material may be formed from a material selected from the group
  • the electrode structure may be an
  • the anode may be a transparent anode.
  • the thin layer of the high work function material has a thickness of less than 100 A.
  • the electrode structure may be a
  • the present invention is also directed to an organic light emitting diode device having
  • the device includes an anode layer formed from a high work function
  • the anode layer may be formed from a material selected from the group consisting of:
  • the anode layer may be formed from a material selected
  • the anode layer may be formed from a
  • Fig. 1 is a schematic view of a known organic light emitting diode device
  • Fig. 2 is a schematic view of an organic light emitting diode device in accordance
  • Fig.2 discloses an organic light emitting diode device 20 according to an embodiment
  • the OLED device 20 includes a substrate 21.
  • a first electrode 22 is provided on the substrate 21.
  • An intermediate layer 24 is located on the organic stack 23.
  • second electrode 25 is located on top of the intermediate layer 24.
  • the second electrode 25 is an anode and is formed from ITO. It, however, is
  • IZO IZO
  • the intermediate layer 24 is provided
  • the layer 24 reduces oxygen migration from the second electrode 25 and
  • the intermediate layer 24 is preferably a thin layer of high work function material.
  • the layer 24 is preferably formed from Mo or alloys of Mo.
  • the present invention however,
  • These materials include, but are not limited to W, Nb, Zr, Co, Zn, Tc, Hf, Ta, Cr,
  • Oxides and nitrides of these materials may also be used to improve
  • the second electrode 25 formed from ITO is used only for its
  • the intermediate layer 24 must be sufficiently thin (e.g. a thickness of than 100 A) to permit light to escape through the second electrode and for
  • Oxides and nitrides are often insulating so the thickness must be controlled so
  • the first electrode 22 may then be opaque.
  • the second electrode 25 is not transparent. Accordingly, the
  • first electrode 21 which functions as a cathode, must be transparent or semitransparent to

Landscapes

  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Electroluminescent Light Sources (AREA)

Abstract

An improved organic light emitting diode device (20) is disclosed. The organic light emitting diode device (20) includes a first electrode (25), a second electrode (22), and an organic stack (23) interposed between the first electrode (25) and the second electrode (22). The organic stack (23) may include hole transport materials located on one side of the stack and electron transport materials located on another side of the stack. The improvement includes a thin layer (24) of high work function material interposed between the first electrode (25) and the organic stack (23). The organic light emitting diode device (20) according to the present invention has improved stability.

Description

AN IMPROVED ELECTRODE STRUCTURE FOR ORGANIC LIGHT EMITTING DIODE DEVICES
Field of the Invention
The present invention relates to electrode structures for an organic light emitting diode (OLED) device. In particular, the present invention relates to an improved anode structure for an OLED device.
Background of the Invention
Fig. 1 discloses a known OLED device 10. The OLED device 10 includes a glass substrate 11. A transparent hole-injecting anode or electrode 12 formed of indium-tin oxide (ITO) is located on the glass substrate 11. An organic stack 13 is located on the anode 12. The anode 12 forms the first or bottom layer of the stack 13. A metal cathode 14 is located on top of the organic stack 13. In the device 10, light is emitted in a downward direction through the electrode 12 and the glass substrate 11.
OLED require two electrodes, an anode 12 and a cathode 14, at least one of which must be transparent to allow light to escape. The anode 12, which must supply holes to the emitting region, is usually formed from a material with high work function, since this will lead to a low energy for hole injection. The cathode 14, which must supply electrons to the emitting region, is usually formed from a material with low work function, which will facilitate electron injection. Indium tin oxide (ITO), which is a good transparent conductor has long been used as an anode material, because it has a high work function, about 5.0 eV. The injection efficiency of ITO, and consequently the luminescent efficiency of the OLED, is enhanced by pretreating the ITO with an oxygen plasma, which ensures that there is an excess of oxygen at the interface with the organic stack 13. The excess of oxygen appears to contribute to the instability of such OLEDs because the oxygen can migrate and react with the organic materials. ITO has also been used in conjunction with thin metal interlayers to form cathode contacts, where the thin metal is of a low work function material to provide electron injection.
Objects of the Invention
It is an object of the present invention to provide an improved electrode structure for an OLED device. It is another object of the present invention to provide an improved anode structure for an OLED device.
It is another object of the present invention to provide an OLED device having improved stability.
It is another object of the present invention to provide an anode with a thin interface layer to improve OLED device stability.
It is another object of the present invention to improve stability of an OLED device by reducing oxygen migration.
It is another object of the present invention to isolate the ITO layer from the organic stack by interposing a thin metal layer of a high work function material.
Summary of the Invention
The present invention is directed to an improved organic light emitting diode device.
The organic light emitting diode device includes a first electrode, a second electrode, and an
organic stack interposed between the first electrode and the second electrode. The organic
stack may include hole transport materials located on one side of the stack and electron
transport materials located on another side of the stack. The improvement includes a thin
layer of high work function material interposed between the first electrode and the organic stack. The organic light emitting diode device according to the present invention has
improved stability.
The thin layer of high work function material may be formed from a material selected
from the group consisting of Mo and alloys of Mo. The thin layer of high work function
material may be formed from a material selected from the group consisting of W and alloys
of W. Alternatively, the thin layer of high work function material may be formed from a
material selected from the group consisting of Nb, Zr, Co, Zn, Tc, Hf, Ta, Cr, Au, Pt, Pd, Se,
Ni and alloys of at least one of Nb, Zr, Co, Zn, Tc, Hf, Ta, Cr, Au, Pt, Pd, Se, and Ni. The
thin layer of the high work function material may have a thickness of less than 100 A.
The first electrode may be a transparent electrode and the second electrode may be
a cathode. The second electrode may be formed from a low work function material.
The present invention is also directed to an improved electrode structure for an
organic light emitting device. The electrode may comprise an electrode layer, and a thin
layer of a high work function material located adjacent the electrode layer. The thin layer of
high work function material may be formed from a material selected from the group
consisting of Mo and alloys of Mo. The thin layer of high work function material may be
formed from a material selected from the group consisting of W and alloys of W. The thin
layer of high work function material may be formed from a material selected from the group
consisting of Nb, Zr, Co, Zn, Tc, Hf, Ta, Cr, Au, Pt, Pd, Se, Ni and alloys of at least one of
Nb, Zr, Co, Zn, Tc, Hf, Ta, Cr, Au, Pt, Pd, Se, and Ni. The electrode structure may be an
anode. The anode may be a transparent anode. The thin layer of the high work function material has a thickness of less than 100 A. Alternatively, the electrode structure may be a
cathode.
The present invention is also directed to an organic light emitting diode device having
improved stability. The device includes an anode layer formed from a high work function
material, an organic stack having hole transport materials located on one side of the stack and
electron transport materials located on another side of the organic stack, a transport electrode
layer, and a thin layer of a low work function material located between the organic stack and
the transport layer. The anode layer may be formed from a material selected from the group
consisting of Mo and alloys of Mo. The anode layer may be formed from a material selected
from the group consisting of W and alloys of W. The anode layer may be formed from a
material selected from the group consisting of Nb, Zr, Co, Zn, Tc, Hf, Ta, Cr, Au, Pt, Pd, Se,
Ni and alloys of at least one of Nb, Zr, Co, Zn, Tc, Hf, Ta, Cr, Au, Pt, Pd, Se, and Ni.
Brief Description of the Drawings
The invention will be described in conjunction with the following drawings in which
like reference numerals designate like elements and wherein:
Fig. 1 is a schematic view of a known organic light emitting diode device; and
Fig. 2 is a schematic view of an organic light emitting diode device in accordance
with an embodiment of the present invention. Detailed Description of the Preferred Embodiment
Fig.2 discloses an organic light emitting diode device 20 according to an embodiment
of the present invention. The OLED device 20 includes a substrate 21. A first electrode 22,
which functions as a cathode, is located on the substrate 21. An organic stack 23 is located
on the first electrode 22. An intermediate layer 24 is located on the organic stack 23. A
second electrode 25 is located on top of the intermediate layer 24.
The second electrode 25 is an anode and is formed from ITO. It, however, is
contemplated that other suitable materials including but not limited to indium zinc oxide
(IZO) may be used to form the second electrode 25. The intermediate layer 24 is provided
to isolate the second electrode 25 from the organic stack 23 to improve the stability of the
OLED device 20. The layer 24 reduces oxygen migration from the second electrode 25 and
reaction with the organic materials.
The intermediate layer 24 is preferably a thin layer of high work function material.
The layer 24 is preferably formed from Mo or alloys of Mo. The present invention, however,
is not limited to thin layers formed from Mo; rather, it is contemplated that other materials
having high work function properties may be used to increase the stability of the OLED
device 20. These materials include, but are not limited to W, Nb, Zr, Co, Zn, Tc, Hf, Ta, Cr,
Au, Pt, Pd, Se, and Ni. Oxides and nitrides of these materials may also be used to improve
stability so long as che material has a high work function.
With this arrangement, the second electrode 25 formed from ITO is used only for its
transparency and not for its work function and injection properties. When the second
electrode 25 is a transparent anode, the intermediate layer 24 must be sufficiently thin (e.g. a thickness of than 100 A) to permit light to escape through the second electrode and for
conductivity. Oxides and nitrides are often insulating so the thickness must be controlled so
that the device 20 may operate effectively. The first electrode 22 may then be opaque.
Alternatively, the high work function materials, discussed above, may be substituted
for the second electrode 25. The second electrode 25 is not transparent. Accordingly, the
first electrode 21, which functions as a cathode, must be transparent or semitransparent to
permit light to escape.
While this invention has been described in conjunction with specific embodiments
thereof, it is evident that many alternatives, modifications and variations will be apparent to
those skilled in the art. Accordingly, the preferred embodiments of the invention as set forth
herein are intended to be illustrative, not limiting. Various changes may be made without
departing from the spirit and scope of the invention as defined in the following claims.

Claims

WHAT IS CLAIMED IS:
1. In an organic light emitting diode device having a first electrode, a second
electrode, and an organic stack interposed between said first electrode and said second
electrode, said organic stack including hole transport materials located on one side and
electron transport materials located on another side, the improvement comprising:
a thin layer of high work function material interposed between said first electrode and
said organic stack.
2. The organic light emitting diode device according to Claim 1 , wherein said
thin layer of high work function material is formed from a material selected from the group
consisting of Mo and alloys of Mo.
3. The organic light emitting diode device according to Claim 1 , wherein said
thin layer of high work function material is formed from a material selected from the group
consisting of W and alloys of W.
4. The organic light emitting diode device according to Claim 1 , wherein said
thin layer of high work function material is formed from a material selected from the group
consisting of Nb, Zr, Co, Zn, Tc, Hf, Ta, Cr, Au, Pt, Pd, Se, Ni and alloys of at least one of
Nb, Zr, Co, Zn, Tc, Hf, Ta, Cr, Au, Pt, Pd, Se, and Ni.
5. The organic light emitting diode device according to Claim 1 , wherein said
thin layer of said high work function material has a thickness of less than 100 A.
6. The organic light emitting diode device according to Claim 1 , wherein said
first electrode is a transparent electrode and said second electrode is a cathode.
7. The organic light emitting diode device according to Claim 6, wherein said
second electrode is formed from a low work function material.
8. The organic light emitting diode device according to Claim 1 , wherein said
device has improved stability.
9. An improved electrode structure for an organic light emitting device, said
electrode comprising:
an electrode layer; and
a thin layer of a high work function material located adjacent said electrode layer.
10. The electrode structure according to Claim 9, wherein said thin layer of
high work function material is formed from a material selected from the group consisting of
Mo and alloys of Mo.
1 1. The electrode structure according to Claim 9, wherein said thin layer of
high work function material is formed from a material selected from the group consisting of
W and alloys of W.
12. The electrode structure according to Claim 9, wherein said thin layer of
high work function material is formed from a material selected from the group consisting of
Nb, Zr, Co, Zn, Tc, Hf, Ta, Cr, Au, Pt, Pd, Se, Ni and alloys of at least one of Nb, Zr, Co, Zn,
Tc, Hf, Ta, Cr, Au, Pt, Pd, Se and Ni.
13. The electrode structure according to Claim 9, wherein said electrode
structure is an anode.
14. The electrode structure according to Claim 13, wherein said anode is a
transparent anode.
15. The electrode structure according to Claim 14, wherein said thin layer of
said high work function material has a thickness of less than 100 A.
16. The electrode structure according to Claim 9, wherein said electrode
structure is a cathode.
17. The electrode structure according to Claim 9, wherein said electrode layer
is transparent.
18. The electrode structure according to Claim 9, wherein said thin layer of
said high work function material has a thickness of less than 100 A.
19. An organic light emitting diode device having improved stability
comprising:
an anode layer formed from a high work function material;
an organic stack having hole transport materials located on one side of said stack and
electron transport materials located on another side of said organic stack;
a transport electrode layer; and
a thin layer of a low work function material located between said organic stack and
said transport layer.
20. The organic light emitting diode device according to Claim 19, wherein
said anode layer is formed from a material selected from the group consisting of Mo and
alloys of Mo.
21. The organic light emitting diode device according to Claim 19, wherein
said anode layer is formed from a material selected from the group consisting of W and alloys
of W.
22. The organic light emitting diode device according to Claim 19, wherein
said anode layer is formed from a material selected from the group consisting of Nb, Zr, Co,
Zn, Tc, Hf, Ta, Cr, Au, Pt, Pd, Se, Ni and alloys of at least one of Nb, Zr, Co, Zn, Tc, Hf, Ta,
Cr, Au, Pt, Pd, Se and Ni.
PCT/US1999/003900 1998-05-18 1999-02-24 An improved electrode structure for organic light emitting diode devices WO1999060599A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
KR1020007012865A KR20010071276A (en) 1998-05-18 1999-02-24 An improved electrode structure for organic light emitting diode devices
EP99909560A EP1088320A1 (en) 1998-05-18 1999-02-24 An improved electrode structure for organic light emitting diode devices
JP2000550128A JP2002516459A (en) 1998-05-18 1999-02-24 Improved electrode structure for organic light emitting diode devices

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US8591098P 1998-05-18 1998-05-18
US60/085,910 1998-05-18

Publications (1)

Publication Number Publication Date
WO1999060599A1 true WO1999060599A1 (en) 1999-11-25

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PCT/US1999/003900 WO1999060599A1 (en) 1998-05-18 1999-02-24 An improved electrode structure for organic light emitting diode devices

Country Status (5)

Country Link
EP (1) EP1088320A1 (en)
JP (1) JP2002516459A (en)
KR (1) KR20010071276A (en)
CN (1) CN1321325A (en)
WO (1) WO1999060599A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1134817A2 (en) 2000-03-15 2001-09-19 Sony Corporation Light-emitting device and its use

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108598868B (en) * 2018-05-22 2019-12-06 西北核技术研究所 An electrode structure and design method for a gas spark switch
KR102718279B1 (en) * 2019-09-23 2024-10-15 삼성전자주식회사 Light emitting device and method of manufacturing the same and display device

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5714838A (en) * 1996-09-20 1998-02-03 International Business Machines Corporation Optically transparent diffusion barrier and top electrode in organic light emitting diode structures
US5820996A (en) * 1996-01-31 1998-10-13 Sharp Kabushiki Kaisha Electroluminescence device and method of manufacturing same

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5820996A (en) * 1996-01-31 1998-10-13 Sharp Kabushiki Kaisha Electroluminescence device and method of manufacturing same
US5714838A (en) * 1996-09-20 1998-02-03 International Business Machines Corporation Optically transparent diffusion barrier and top electrode in organic light emitting diode structures

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1134817A2 (en) 2000-03-15 2001-09-19 Sony Corporation Light-emitting device and its use

Also Published As

Publication number Publication date
EP1088320A1 (en) 2001-04-04
CN1321325A (en) 2001-11-07
JP2002516459A (en) 2002-06-04
KR20010071276A (en) 2001-07-28

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