US20020011782A1 - Organic electroluminescent device with improved hole injecting structure - Google Patents

Organic electroluminescent device with improved hole injecting structure Download PDF

Info

Publication number
US20020011782A1
US20020011782A1 US09/234,457 US23445799A US2002011782A1 US 20020011782 A1 US20020011782 A1 US 20020011782A1 US 23445799 A US23445799 A US 23445799A US 2002011782 A1 US2002011782 A1 US 2002011782A1
Authority
US
United States
Prior art keywords
buffer layer
anode
layer
cathode
organic electroluminescent
Prior art date
Legal status (The legal status 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 status listed.)
Granted
Application number
US09/234,457
Other versions
US6351067B2 (en
Inventor
Shuit-Tong Lee
Zhen-Bo Deng
William Alexander Gambling
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
CityU Research Ltd
Original Assignee
City University of Hong Kong CityU
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 City University of Hong Kong CityU filed Critical City University of Hong Kong CityU
Priority to US09/234,457 priority Critical patent/US6351067B2/en
Assigned to CITY UNIVERSITY OF HONG KONG reassignment CITY UNIVERSITY OF HONG KONG ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: DENG, Zhen-bo, GAMBLING, WILLIAM ALEXANDER, LEE, SHUIT-TONG
Publication of US20020011782A1 publication Critical patent/US20020011782A1/en
Application granted granted Critical
Publication of US6351067B2 publication Critical patent/US6351067B2/en
Assigned to CITY RESEARCH LIMITED reassignment CITY RESEARCH LIMITED ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: CITY UNIVERSITY OF HONG KONG
Assigned to CITYU RESEARCH LIMITED reassignment CITYU RESEARCH LIMITED CORRECTIVE ASSIGNMENT TO CORRECT THE ASSIGNEE'S NAME. DOCUMENT PREVIOUSLY RECORDED ON REEL 014108 FRAME 0717. ASSIGNOR HEREBY CONFIRMS THE ASSIGNMENT OF THE ENTIRE INTEREST. Assignors: CITY UNIVERSITY OF HONG KONG
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/17—Carrier injection layers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/17—Carrier injection layers
    • H10K50/171—Electron injection layers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S428/00—Stock material or miscellaneous articles
    • Y10S428/917—Electroluminescent

Definitions

  • the present invention pertains to organic thin-film electroluminescent devices and a method of manufacture of such devices.
  • OELDs organic electroluminescent devices
  • Representatives of early OELDs are Gurnee et al U.S. Pat. No. 3,172,862, issued Mar. 9, 1965; Gurnee U.S. Pat. No. 3,173,050, issued Mar. 9, 1965; and Dresner U.S. Pat. No. 3,710,167, issued Jan. 9, 1973.
  • These devices comprised a single organic emitting layer having thicknesses above 1 mm and two electrodes (cathode and anode). Alkali metals were used as the cathode materials as they had the lowest work function values.
  • Tang et al U.S. Pat. No. 4,356,429 disclosed an OELD with two organic layers, in which the organic luminescent medium consisted of two extremely thin layers separating the anode and the cathode. These comprised one layer injecting and transporting holes and the other layer injecting and transporting electrons and also acting as the organic luminescent zone of the device.
  • 5,668,438 disclosed an OELD in which the materials making up the electron transporting layer (ETL) and the hole transporting layer (HTL) were selected so that the energy barrier for hole injection from the HTL to the ETL was substantially higher than the energy barrier for electron injection from the ETL to the HTL. In that case, light was emitted from the HTL rather than the ETL.
  • ETL electron transporting layer
  • HTL hole transporting layer
  • Hung et al U.S. Pat. No. 5,776,623 disclosed an OELD containing a transparent electron-injecting electrode.
  • the electrode included a thin non-conductive layer contacting the electroluminescent layer and a conductive transparent overcoat layer. The thickness of the nonconductive layer was selected so that the bilayer acted as an electron injecting contact and provided stability against atmospheric corrosion.
  • Vanslyke et al U.S. Pat. No. 5,061,569 disclosed an internal junction OELD in which the hole injecting and transporting zone included a tertiary amine containing at least two tertiary amine moieties and including, attached to a tertiary amine nitrogen atom, an aromatic moiety containing at least two fused aromatic rings.
  • Tokito et al U.S. Pat. No. 5,783,292 disclosed an OELD in which organic-inorganic composite thin film was used.
  • This invention comprises an OELD and method of manufacture in which an inorganic buffer layer is included in the hole injecting region.
  • the device comprises in order: an ITO-covered glass substrate which behaves as the hole injector and is transparent and transmissive to optical radiation, a layer of inorganic material as a buffer to the hole injection, an organic single layer or multilayer structure for electroluminescence and carrier confinement, and a layer of low-work-function material as an electron injector which is stable relative to atmospheric corrosion.
  • the buffer layer may also be included in the electron injecting region.
  • FIGS. 1 and 2 which are schematic diagrams of an embodiment of the OELD of the invention.
  • FIG. 3 is a graphical representation of the results of different thickness of buffer layer in terms of brightness.
  • FIG. 4 is a graphical representation of the results of FIG. 3 in terms of electroluminescent efficiency.
  • An electroluminescent (EL) device 100 of the invention is schematically illustrated in FIG. 1.
  • Anode 102 is separated from cathode 104 by an inorganic buffer layer 106 and an organic luminescent medium 108 , which, as shown in this embodiment, consists of two superimposed layers.
  • Layer 110 which is located above the buffer layer 106 , forms a hole injecting zone of the organic luminescent medium.
  • layer 112 which forms an electron transporting zone of the organic luminescent medium.
  • the anode and the cathode are connected to an external AC or DC power source 114 by conductors 116 and 118 , respectively.
  • the power source can be pulsed or continuous wave.
  • the EL device 100 When the EL device 100 is forward biased, i.e., the potential of the anode is higher than that of the cathode, there occurs injection of holes (positive charge carriers) into the lower organic layer, as schematically shown at 120 , while electrons are injected into the upper organic layer, as schematically shown at 122 , in the luminescent medium.
  • the injected holes and electrons each migrate toward the oppositely charged electrode, as shown by the arrows 124 and 126 , respectively. This results in hole-electron recombination.
  • a migrating electron drops from its conduction potential to a valence band in filing a hole, energy is released as light.
  • the organic luminescent medium forms between the electrodes a luminescent zone receiving mobile charge carriers from each electrode.
  • the released light can be emitted from the organic luminescent material through one or more edges 128 of the organic luminescent medium separating the electrodes, through the anode, through the cathode, or through any combination of the foregoing.
  • Organic EL device 200 shown in FIG. 2 is illustrative of one preferred embodiment of the invention. Same as in previous OELDs'fabrication, a transparent anode electrode is used in the present invention.
  • Layer 202 is a transparent and insulating support onto which is deposited a conductive and light transmissive 204 . Typically, this layer is made from metal or metal oxide such as ITO.
  • This layer as an anode electrode, possesses a relatively high work function.
  • Adjacent to 204 is the anode-combined buffer layer 206 , which, in this embodiment, is selected from the group consisting of SiO x , Y 2 O 3 , and Ta 2 O 5 , where x is from 1 to 2.
  • the organic luminescent medium 208 consisting of hole injecting zone 210 and electron transporting zone 212 in which luminescence occurs.
  • the top electrode 214 acts as the electron injector with a relatively low work function. It is usually either a single metal or a multi-metal mixture formed by codeposition in vacuum.
  • the preferred embodiments above describe an OELD which positions the buffer layer between the anode and the luminescent medium.
  • the buffer layer may also increase efficiency when positioned between the cathode and the luminescent medium, for example, between the cathode and electron transporting layer.
  • multiple buffer layers such as a buffer layer adjacent the anode and a further buffer layer adjacent the cathode are possible. There is no requirement for identical buffer layers in such a multi-layer structure with the buffer layers on opposed sides of the luminescent medium able to be of different materials or mixtures as required.
  • the buffer layers described have been selected from a particularly group of oxides.
  • the buffer layer is chosen from insulating metal oxides, semiconductor oxides, diamond-like carbon and nitrogen doped carbon.
  • insulating metal oxides semiconductor oxides
  • diamond-like carbon diamond-like carbon
  • nitrogen doped carbon a number of different materials may be used in the buffer layer to perform the same function. The list provided is not considered exhaustive.
  • the electroluminescent element contained within the device can comprise variety of materials found suitable for such purposes. These include the inclusion of molecules selected from Alq, TPD, NPB and TPBI as well as a variety of polymers.
  • the polymers may include such polymers as poly (paraphenylene vinylene) (PPV), PPV copolymers and derivatives. Again, this is not an exhaustive list of possible materials for this element.
  • the anode can be made from many suitable materials for the purpose. Typically such anodes are made from transparent conducting oxides. These include indium-tin-oxide, aluminum- or indium-doped zinc oxide, tin oxide, magnesium-indium-oxide and cadmium-tin-oxide.
  • the device structure has an inorganic buffer layer and a two organic-layer stack, namely hole transporting layer and fluorescent emitting and electron transporting layer.
  • An indium-tin-oxide coated glass substrate was sequentially ultrasonicated in a commercial detergent, rinsed in deionized water, degreased in organic solvent, such as ethanol and acetone, and exposed to ultraviolet light and ozone for a few minutes.
  • a fluorescent emitting and electron transporting layer of Alq (600 Angstroms) was then deposited onto the hole transporting layer.
  • the OELDs were fabricated according to the procedure of Example 1.
  • the buffer layers with different thicknesses of SiO 2 were used.
  • Table 1 lists the EL luminance quantum efficiency measured in unit of candela per ampere, and luminance output under a constant current bias of 20 mA/cm 2 .
  • the luminance efficiency it can be observed that there may be a reduction in efficiency with a particularly thin layer.
  • the efficiency increases towards the thickness of 1 nm. There may then be a tailing off of efficiency as the thickness increases.
  • This particular buffer layer is an insulating layer and will inhibit current as the layer thickness increases.
  • the thickness as provided in this table shows the performance of SiO 2 . Different thicknesses may provide different results with alternative materials used as the buffer layer.
  • FIG. 3 shows the B-I-V curves of four devices with different thicknesses of buffer layer (SiO 2 )
  • FIG. 4 shows the electroluminescent efficiency of the four devices with different thicknesses of buffer layer (SiO 2 ).
  • the OELDs were fabricated according to the procedure of Example 1. Buffer layers made of different inorganic materials, such as SiO 2 , Y 2 O 3 and Ta 2 O 5 , were used. Table 2 lists the EL luminance quantum efficiency measured in unit of candela per ampere and luminance output under a constant current bias of 20 mA/cm 2 (the thickness of the inorganic materials is about 1.0 nm). TABLE 2 Materials SiO 2 Y 2 O 3 Ta 2 O 5 CIEx 0.339 0.334 0.335 CIEy 0.562 0.562 0.562 Luminance 1,820 1,280 1,360 Luminance Eff. (cd/A) 9.1 6.4 6.8
  • the OELDs were fabricated according to the procedure of Example 1.
  • the substrate with buffer layer was further treated by radiation, which effectively protects the surface of the buffer layer against harmful contamination. Even higher EL efficiency can be obtained thereby.
  • the fabrication procedure provided in the examples again discloses a method of manufacturing an OELD which incorporates a buffer layer between the cathode and anode.
  • the examples given deposit the buffer layer onto the intended anode of the device.
  • the layer may be deposited prior to deposition of the cathode or onto the cathode be the device is deposited in reverse.
  • the order of the layers in the examples are for these preferred embodiments only.

Abstract

An organic electroluminescent device (OELD) with improved luminescent efficiency has been fabricated upon inclusion of an inorganic buffer layer in the hole injecting or electron injecting regions. The structure of the device can be as follows (from bottom to top): ITO\buffer layer\NPB\Alq\Mg:Ag. In comparison with devices without the buffer layer, the present OELD may be more efficient in a proper bias condition.

Description

    FIELD OF THE INVENTION
  • The present invention pertains to organic thin-film electroluminescent devices and a method of manufacture of such devices. [0001]
    • BACKGROUND TO THE INVENTION
  • Fabrication of organic electroluminescent devices (OELDs) can be traced back to 1960's. Representatives of early OELDs are Gurnee et al U.S. Pat. No. 3,172,862, issued Mar. 9, 1965; Gurnee U.S. Pat. No. 3,173,050, issued Mar. 9, 1965; and Dresner U.S. Pat. No. 3,710,167, issued Jan. 9, 1973. These devices comprised a single organic emitting layer having thicknesses above 1 mm and two electrodes (cathode and anode). Alkali metals were used as the cathode materials as they had the lowest work function values. [0002]
  • Tang et al U.S. Pat. No. 4,356,429 disclosed an OELD with two organic layers, in which the organic luminescent medium consisted of two extremely thin layers separating the anode and the cathode. These comprised one layer injecting and transporting holes and the other layer injecting and transporting electrons and also acting as the organic luminescent zone of the device. [0003]
  • Improvements were then achieved by using different cathode materials. Tang et al U.S. Pat. No. 4,885,211 disclosed an OELD with its cathode comprising a layer of a plurality of metals other than single alkali metals, at least one of the metals having a work function of less than 4 eV. Hung et al U.S. Pat. No. 5,608,287 disclosed OELDs having a conductive electron injector. Shi et al U.S. Pat. No. 5,668,438 disclosed an OELD in which the materials making up the electron transporting layer (ETL) and the hole transporting layer (HTL) were selected so that the energy barrier for hole injection from the HTL to the ETL was substantially higher than the energy barrier for electron injection from the ETL to the HTL. In that case, light was emitted from the HTL rather than the ETL. [0004]
  • More recently, Hung et al U.S. Pat. No. 5,776,623 disclosed an OELD containing a transparent electron-injecting electrode. The electrode included a thin non-conductive layer contacting the electroluminescent layer and a conductive transparent overcoat layer. The thickness of the nonconductive layer was selected so that the bilayer acted as an electron injecting contact and provided stability against atmospheric corrosion. [0005]
  • However, only very few patents have dealt with the hole injecting structure. Vanslyke et al U.S. Pat. No. 5,061,569 disclosed an internal junction OELD in which the hole injecting and transporting zone included a tertiary amine containing at least two tertiary amine moieties and including, attached to a tertiary amine nitrogen atom, an aromatic moiety containing at least two fused aromatic rings. Tokito et al U.S. Pat. No. 5,783,292 disclosed an OELD in which organic-inorganic composite thin film was used. [0006]
    • OBJECT OF THE INVENTION
  • It is an object of the present invention to provide an OELD with an increased electroluminescent efficiency and/or improved stability or which will at least provide the public with a useful choice. [0007]
    • SUMMARY OF THE INVENTION
  • This invention comprises an OELD and method of manufacture in which an inorganic buffer layer is included in the hole injecting region. [0008]
  • Preferably, the device comprises in order: an ITO-covered glass substrate which behaves as the hole injector and is transparent and transmissive to optical radiation, a layer of inorganic material as a buffer to the hole injection, an organic single layer or multilayer structure for electroluminescence and carrier confinement, and a layer of low-work-function material as an electron injector which is stable relative to atmospheric corrosion. The buffer layer may also be included in the electron injecting region.[0009]
    • BRIEF DESCRIPTION OF THE DRAWINGS
  • Preferred embodiments of this invention can be better appreciated by reference to the following description considered in conjunction with the drawings in which: [0010]
  • FIGS. 1 and 2 which are schematic diagrams of an embodiment of the OELD of the invention; [0011]
  • FIG. 3 is a graphical representation of the results of different thickness of buffer layer in terms of brightness; and [0012]
  • FIG. 4 is a graphical representation of the results of FIG. 3 in terms of electroluminescent efficiency.[0013]
    • DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • An electroluminescent (EL) [0014] device 100 of the invention is schematically illustrated in FIG. 1. Anode 102 is separated from cathode 104 by an inorganic buffer layer 106 and an organic luminescent medium 108, which, as shown in this embodiment, consists of two superimposed layers. Layer 110, which is located above the buffer layer 106, forms a hole injecting zone of the organic luminescent medium. Above layer 110 is layer 112, which forms an electron transporting zone of the organic luminescent medium. The anode and the cathode are connected to an external AC or DC power source 114 by conductors 116 and 118, respectively. The power source can be pulsed or continuous wave.
  • When the [0015] EL device 100 is forward biased, i.e., the potential of the anode is higher than that of the cathode, there occurs injection of holes (positive charge carriers) into the lower organic layer, as schematically shown at 120, while electrons are injected into the upper organic layer, as schematically shown at 122, in the luminescent medium. The injected holes and electrons each migrate toward the oppositely charged electrode, as shown by the arrows 124 and 126, respectively. This results in hole-electron recombination. When a migrating electron drops from its conduction potential to a valence band in filing a hole, energy is released as light. Hence the organic luminescent medium forms between the electrodes a luminescent zone receiving mobile charge carriers from each electrode. Depending upon the choice of alternative constructions, the released light can be emitted from the organic luminescent material through one or more edges 128 of the organic luminescent medium separating the electrodes, through the anode, through the cathode, or through any combination of the foregoing.
  • [0016] Organic EL device 200 shown in FIG. 2 is illustrative of one preferred embodiment of the invention. Same as in previous OELDs'fabrication, a transparent anode electrode is used in the present invention. Layer 202 is a transparent and insulating support onto which is deposited a conductive and light transmissive 204. Typically, this layer is made from metal or metal oxide such as ITO. This layer, as an anode electrode, possesses a relatively high work function. Adjacent to 204 is the anode-combined buffer layer 206, which, in this embodiment, is selected from the group consisting of SiOx, Y2O3, and Ta2O5, where x is from 1 to 2. Above 206 is the organic luminescent medium 208, consisting of hole injecting zone 210 and electron transporting zone 212 in which luminescence occurs. The top electrode 214 acts as the electron injector with a relatively low work function. It is usually either a single metal or a multi-metal mixture formed by codeposition in vacuum.
  • The preferred embodiments above describe an OELD which positions the buffer layer between the anode and the luminescent medium. The buffer layer may also increase efficiency when positioned between the cathode and the luminescent medium, for example, between the cathode and electron transporting layer. Furthermore, multiple buffer layers such as a buffer layer adjacent the anode and a further buffer layer adjacent the cathode are possible. There is no requirement for identical buffer layers in such a multi-layer structure with the buffer layers on opposed sides of the luminescent medium able to be of different materials or mixtures as required. [0017]
  • The buffer layers described have been selected from a particularly group of oxides. In preferred embodiments, the buffer layer is chosen from insulating metal oxides, semiconductor oxides, diamond-like carbon and nitrogen doped carbon. Of course, a number of different materials may be used in the buffer layer to perform the same function. The list provided is not considered exhaustive. [0018]
  • The electroluminescent element contained within the device can comprise variety of materials found suitable for such purposes. These include the inclusion of molecules selected from Alq, TPD, NPB and TPBI as well as a variety of polymers. The polymers may include such polymers as poly (paraphenylene vinylene) (PPV), PPV copolymers and derivatives. Again, this is not an exhaustive list of possible materials for this element. [0019]
  • Similarly, the anode can be made from many suitable materials for the purpose. Typically such anodes are made from transparent conducting oxides. These include indium-tin-oxide, aluminum- or indium-doped zinc oxide, tin oxide, magnesium-indium-oxide and cadmium-tin-oxide. [0020]
    • EXAMPLES
  • The invention and its advantages are further illustrated by the specific examples which follow: [0021]
    • Example 1
  • Fabrication Procedure [0022]
  • An OELD satisfying the requirements of the invention was constructed in the following manner. The device structure has an inorganic buffer layer and a two organic-layer stack, namely hole transporting layer and fluorescent emitting and electron transporting layer. [0023]
  • An indium-tin-oxide coated glass substrate was sequentially ultrasonicated in a commercial detergent, rinsed in deionized water, degreased in organic solvent, such as ethanol and acetone, and exposed to ultraviolet light and ozone for a few minutes. [0024]
  • An inorganic buffer layer (0-200 Angstroms) was then deposited on top of the ITO coated substrate by evaporation. [0025]
  • Onto the buffer layer was deposited a hole transporting layer of TPD or NPB (500-1,500 Angstroms), evaporated from a tantalum boat. [0026]
  • A fluorescent emitting and electron transporting layer of Alq (600 Angstroms) was then deposited onto the hole transporting layer. [0027]
  • On top of the Alq layer was deposited a 1,500-Angstrom thick cathode formed of a 10:1 atomic ratio of Mg and Ag. [0028]
  • The above sequence completed the deposition of the OELD. The device was then packaged in a dry glove box for protection against ambient environment. [0029]
    • Example 2
  • OELDs with SiO[0030] 2 Buffer Layer
  • The OELDs were fabricated according to the procedure of Example 1. The buffer layers with different thicknesses of SiO[0031] 2 were used. Table 1 lists the EL luminance quantum efficiency measured in unit of candela per ampere, and luminance output under a constant current bias of 20 mA/cm2.
    TABLE 1
    SiO2 Thickness (nm) 0 0.5 1.0 1.5
    CIEx 0.334 0.338 0.339 0.339
    CIEy 0.562 0.563 0.562 0.562
    Luminance 1,140 960 1,820 1,680
    Luminance Eff. (cd/A) 5.7 4.8 9.1 8.4
  • Referring to the luminance efficiency, it can be observed that there may be a reduction in efficiency with a particularly thin layer. However, as shown in this example using SiO[0032] 2, the efficiency increases towards the thickness of 1 nm. There may then be a tailing off of efficiency as the thickness increases. This particular buffer layer is an insulating layer and will inhibit current as the layer thickness increases. The thickness as provided in this table shows the performance of SiO2. Different thicknesses may provide different results with alternative materials used as the buffer layer.
    • Example 3
  • Brightness-Current-Voltage (B-I-V) Characteristics [0033]
  • The OELDs were fabricated according to the procedure of Example 1. FIG. 3 shows the B-I-V curves of four devices with different thicknesses of buffer layer (SiO[0034] 2)
    • Example 4
  • Quantum Efficiency of the Devices with Different Thicknesses of SiO[0035] 2
  • The OELDs were fabricated according to the procedure of Example 1. FIG. 4 shows the electroluminescent efficiency of the four devices with different thicknesses of buffer layer (SiO[0036] 2).
    • Example 5
  • OELDs with Different Buffer Layers [0037]
  • The OELDs were fabricated according to the procedure of Example 1. Buffer layers made of different inorganic materials, such as SiO[0038] 2, Y2O3 and Ta2O5, were used. Table 2 lists the EL luminance quantum efficiency measured in unit of candela per ampere and luminance output under a constant current bias of 20 mA/cm2 (the thickness of the inorganic materials is about 1.0 nm).
    TABLE 2
    Materials SiO2 Y2O3 Ta2O5
    CIEx 0.339 0.334 0.335
    CIEy 0.562 0.562 0.562
    Luminance 1,820 1,280 1,360
    Luminance Eff. (cd/A) 9.1 6.4 6.8
    • Example 6
  • Further Treatment of the Buffer Layer [0039]
  • The OELDs were fabricated according to the procedure of Example 1. The substrate with buffer layer was further treated by radiation, which effectively protects the surface of the buffer layer against harmful contamination. Even higher EL efficiency can be obtained thereby. [0040]
  • The fabrication procedure provided in the examples again discloses a method of manufacturing an OELD which incorporates a buffer layer between the cathode and anode. The examples given deposit the buffer layer onto the intended anode of the device. Again, it should be noted that the layer may be deposited prior to deposition of the cathode or onto the cathode be the device is deposited in reverse. The order of the layers in the examples are for these preferred embodiments only. [0041]
  • Further aspects of this invention may become apparent to those skill in the art to which the invention relates. It should be noted that integers referred to throughout the specification are deemed to incorporate known equivalents and the disclosure of the preferred embodiments did not be considered limiting to the scope of the invention as defined by the appended claims. [0042]

Claims (18)

1. An organic electroluminescent device including an anode, a cathode and an organic electroluminescent element disposed between the anode and cathode and wherein at least one buffer layer is provided between said anode and cathode.
2. A device as claimed in claim 1 wherein said organic electroluminescent element includes one hole transporting layer and one fluorescent emitting layer.
3. A device as claimed in claim 1 wherein said organic electroluminescent element includes one fluorescent emitting layer and one electron transporting layer.
4. A device as claimed in claim 1 wherein said organic electroluminescent element includes one hole transporting layer, one fluorescent emitting layer and one electron transporting layer.
5. A device as claimed in claim 1 wherein said buffer layer is disposed between the anode and the hole transporting layer.
6. A device as claimed in claim 1 wherein the buffer layer is disposed between the cathode and the electron transporting layer.
7. A device as claimed in claim 1 wherein said buffer layer comprising a material selected from the group consisting of insulating metal oxides, semiconductor oxides, diamond-like carbon and nitrogen-doped carbon.
8. A device as claimed in any one of claims 1 to 7 wherein said metal oxides and semiconductor oxides including Ta2O5, Y2O3 and SiOx, with x from 1 to 2.
9. A device as claimed in any one of claims 1 to 7 wherein said buffer layer has a thickness ranging from 0 to 20 nm.
10. A device as claimed in any one of claims 1 to 7 wherein said buffer layer has been further treated by radiation.
11. A device as claimed in any one of claims 1 to 7 wherein said organic electroluminescent element comprises materials including molecules selected from Alq, TPD, NPB and TPBI and polymers.
12. A device as claimed in claim 11 wherein said polymers include poly (paraphenylene vinylene) (PPV), PPV copolymers and derivatives.
13. A device as claimed in any one of claims 1 to 7 wherein said anode is selected from transparent conducting oxides including indium-tin-oxide, aluminum- or indium-doped zinc oxide, tin oxide, magnesium-indium-oxide, and cadmium-tin-oxide.
14. A method of manufacturing an organic electroluminescent device comprising the steps of providing an anode, a cathode and an organic electroluminescent element between said anode and cathode and wherein a buffer layer is positioned between said anode and cathode.
15. A method as claimed in claim 14 wherein said step of positioning said buffer layer comprises depositing a buffer layer onto said anode and/or cathode.
16. A method as claimed in claim 15 wherein said buffer layer is deposited onto said anode.
17. A method as claimed in claim 15 wherein said deposition is performed by evaporation.
18. A method as claimed in claim 14 wherein said buffer layer is provided having a thickness in a range of 0 to 200 Angstorms.
US09/234,457 1999-01-21 1999-01-21 Organic electroluminescent device with improved hole injecting structure Expired - Lifetime US6351067B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US09/234,457 US6351067B2 (en) 1999-01-21 1999-01-21 Organic electroluminescent device with improved hole injecting structure

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US09/234,457 US6351067B2 (en) 1999-01-21 1999-01-21 Organic electroluminescent device with improved hole injecting structure

Publications (2)

Publication Number Publication Date
US20020011782A1 true US20020011782A1 (en) 2002-01-31
US6351067B2 US6351067B2 (en) 2002-02-26

Family

ID=22881476

Family Applications (1)

Application Number Title Priority Date Filing Date
US09/234,457 Expired - Lifetime US6351067B2 (en) 1999-01-21 1999-01-21 Organic electroluminescent device with improved hole injecting structure

Country Status (1)

Country Link
US (1) US6351067B2 (en)

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1244154A2 (en) * 2001-03-22 2002-09-25 Sanyo Electric Co., Ltd. Organic electroluminescence device and manufacturing method thereof
US20040113547A1 (en) * 1999-12-31 2004-06-17 Se-Hwan Son Electroluminescent devices with low work function anode
US20040169175A1 (en) * 1999-12-31 2004-09-02 Lg Chemical Co., Ltd. Electronic device comprising organic compound having p-type semiconducting characteristics
US20060038484A1 (en) * 1999-12-31 2006-02-23 Noh Jeoung K Organic light-emitting device comprising buffer layer and method for fabricating the same
US20060132026A1 (en) * 2004-12-17 2006-06-22 Honeywell International, Inc. Organic light emitting diode (OLED) having improved stability, luminance, and efficiency
US20070102698A1 (en) * 1999-12-31 2007-05-10 Kang Min S Organic electronic device
EP1982562A1 (en) * 2006-02-06 2008-10-22 LG Chem, Ltd. Organic light emitting device using inorganic insulating layer as an electron injecting layer and method for preparing the same
US20080284325A1 (en) * 2005-11-07 2008-11-20 Lg Chem, Ltd. Organic electroluminescent device and method for preparing the same
US20090009101A1 (en) * 2006-01-18 2009-01-08 Kang Min-Soo Oled Having Stacked Organic Light-Emitting Units
US20090091242A1 (en) * 2007-10-05 2009-04-09 Liang-Sheng Liao Hole-injecting layer in oleds
KR100897762B1 (en) * 2007-04-07 2009-05-15 김용성 ORGANIC LIGHT EMITTING DEVICE USING THE TRANSPARENT CONDUCTING ELECTRODE OF ZnO THIN FILM
US20110309349A1 (en) * 2009-08-07 2011-12-22 Mitsui Mining & Smelting Co., Ltd. Anode structure for use in organic el device, production method thereof and organic el device
US20150008394A1 (en) * 2013-07-02 2015-01-08 Samsung Display Co., Ltd. Organic light emitting diode display
US9391124B2 (en) 2013-07-02 2016-07-12 Samsung Display Co., Ltd. Organic light emitting diode display

Families Citing this family (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100722084B1 (en) * 1999-04-30 2007-05-25 이데미쓰 고산 가부시키가이샤 Organic electroluminescent device and method of manufacture thereof
US7488986B2 (en) * 2001-10-26 2009-02-10 Semiconductor Energy Laboratory Co., Ltd. Light emitting device
JP4290953B2 (en) * 2002-09-26 2009-07-08 奇美電子股▲ふん▼有限公司 Image display device, organic EL element, and method of manufacturing image display device
TW589923B (en) * 2003-04-10 2004-06-01 Toppoly Optoelectronics Corp Organic light emitted display having anti-reflective and inert cathode
WO2004095507A2 (en) * 2003-04-23 2004-11-04 Zheng-Hong Lu Light-emitting devices with an embedded charge injection electrode
DE10330795B4 (en) * 2003-07-08 2008-01-24 Qimonda Ag Carbon hard mask with a nitrogen-doped carbon layer as an adhesive layer for adhesion to metal or metal-containing inorganic materials and method for their preparation
US20060251918A1 (en) * 2003-12-11 2006-11-09 Toshihiro Iwakuma Organic electroluminescent device material and organic electroluminescent device using same
US20060087230A1 (en) * 2004-10-22 2006-04-27 Eastman Kodak Company Desiccant film in top-emitting OLED
US20060240280A1 (en) * 2005-04-21 2006-10-26 Eastman Kodak Company OLED anode modification layer
US7726335B2 (en) * 2005-04-29 2010-06-01 Ti Group Automotive Systems, L.L.C. Check valve apparatus for fuel delivery systems
JP5326289B2 (en) * 2007-03-23 2013-10-30 凸版印刷株式会社 ORGANIC EL ELEMENT AND DISPLAY DEVICE INCLUDING THE SAME
KR101453082B1 (en) * 2007-06-15 2014-10-28 삼성전자주식회사 Alternating current driving type quantum dot electroluminescence device
DE102016101710A1 (en) * 2016-02-01 2017-08-03 Osram Oled Gmbh OLED and method for producing an OLED
US10923689B2 (en) 2018-01-25 2021-02-16 OLEDWorks LLC Method for mask-free OLED deposition and manufacture

Family Cites Families (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3172862A (en) 1960-09-29 1965-03-09 Dow Chemical Co Organic electroluminescent phosphors
US3173050A (en) 1962-09-19 1965-03-09 Dow Chemical Co Electroluminescent cell
US3710167A (en) 1970-07-02 1973-01-09 Rca Corp Organic electroluminescent cells having a tunnel injection cathode
US4356429A (en) 1980-07-17 1982-10-26 Eastman Kodak Company Organic electroluminescent cell
US4757235A (en) * 1985-04-30 1988-07-12 Nec Corporation Electroluminescent device with monolithic substrate
US4885211A (en) 1987-02-11 1989-12-05 Eastman Kodak Company Electroluminescent device with improved cathode
DE69110922T2 (en) * 1990-02-23 1995-12-07 Sumitomo Chemical Co Organic electroluminescent device.
US5061569A (en) 1990-07-26 1991-10-29 Eastman Kodak Company Electroluminescent device with organic electroluminescent medium
US5482896A (en) * 1993-11-18 1996-01-09 Eastman Kodak Company Light emitting device comprising an organic LED array on an ultra thin substrate and process for forming same
JPH08102360A (en) 1994-09-29 1996-04-16 Toyota Central Res & Dev Lab Inc Orfanic/inorganic complex thin-film electroluminescent element
US5608287A (en) 1995-02-23 1997-03-04 Eastman Kodak Company Conductive electron injector for light-emitting diodes
US5741626A (en) * 1996-04-15 1998-04-21 Motorola, Inc. Method for forming a dielectric tantalum nitride layer as an anti-reflective coating (ARC)
KR980005265A (en) 1996-06-06 1998-03-30 빈센트 비. 인그라시아 Organic electroluminescent devices emitted from the hole transport layer
US5734225A (en) * 1996-07-10 1998-03-31 International Business Machines Corporation Encapsulation of organic light emitting devices using siloxane or siloxane derivatives
US5776623A (en) 1996-07-29 1998-07-07 Eastman Kodak Company Transparent electron-injecting electrode for use in an electroluminescent device
US5932964A (en) * 1996-09-24 1999-08-03 Mccann & Associates, Inc. Europium-containing group IIA fluoride epitaxial layer on silicon
JPH10125469A (en) * 1996-10-24 1998-05-15 Tdk Corp Organic electroluminescent element
US6140763A (en) * 1998-07-28 2000-10-31 Eastman Kodak Company Interfacial electron-injecting layer formed from a doped cathode for organic light-emitting structure
US6067222A (en) * 1998-11-25 2000-05-23 Applied Materials, Inc. Substrate support apparatus and method for fabricating same

Cited By (37)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080001532A1 (en) * 1999-12-31 2008-01-03 Se-Hwan Son Electroluminescent devices with low work function anode
US20040113547A1 (en) * 1999-12-31 2004-06-17 Se-Hwan Son Electroluminescent devices with low work function anode
US20070102698A1 (en) * 1999-12-31 2007-05-10 Kang Min S Organic electronic device
US20100117063A9 (en) * 1999-12-31 2010-05-13 Kang Min Soo Organic electronic device
US7560175B2 (en) 1999-12-31 2009-07-14 Lg Chem, Ltd. Electroluminescent devices with low work function anode
US20060038484A1 (en) * 1999-12-31 2006-02-23 Noh Jeoung K Organic light-emitting device comprising buffer layer and method for fabricating the same
US8253126B2 (en) 1999-12-31 2012-08-28 Lg Chem. Ltd. Organic electronic device
US7763882B2 (en) 1999-12-31 2010-07-27 Lg Chem, Ltd. Organic light-emitting device comprising buffer layer and method for fabricating the same
US20090058260A9 (en) * 1999-12-31 2009-03-05 Noh Jeoung K Organic light-emitting device comprising buffer layer and method for fabricating the same
US20090230842A9 (en) * 1999-12-31 2009-09-17 Se-Hwan Son Electroluminescent devices with low work function anode
US20040169175A1 (en) * 1999-12-31 2004-09-02 Lg Chemical Co., Ltd. Electronic device comprising organic compound having p-type semiconducting characteristics
US20070257605A1 (en) * 1999-12-31 2007-11-08 Se-Hwan Son Electroluminescent devices with low work function anode
US7538341B2 (en) 1999-12-31 2009-05-26 Lg Chem, Ltd. Electronic device comprising organic compound having p-type semiconducting characteristics
US7648779B2 (en) 1999-12-31 2010-01-19 Lg Chem, Ltd. Electroluminescent devices with low work function anode
US7648780B2 (en) 1999-12-31 2010-01-19 Lg Chem, Ltd. Electroluminescent devices with low work function anode
US20020187366A1 (en) * 2001-03-22 2002-12-12 Yuji Hamada Organic electroluminescence device and manufacturing method thereof
EP1244154A3 (en) * 2001-03-22 2005-02-09 Sanyo Electric Co., Ltd. Organic electroluminescence device and manufacturing method thereof
EP1244154A2 (en) * 2001-03-22 2002-09-25 Sanyo Electric Co., Ltd. Organic electroluminescence device and manufacturing method thereof
EP1842891A1 (en) * 2002-12-11 2007-10-10 LG Chem, Ltd. Electroluminescent devices with low work function anode
EP1842890A1 (en) * 2002-12-11 2007-10-10 LG Chem, Ltd. Electroluminescent devices with low work function anode
US20060132026A1 (en) * 2004-12-17 2006-06-22 Honeywell International, Inc. Organic light emitting diode (OLED) having improved stability, luminance, and efficiency
US7759856B2 (en) 2004-12-17 2010-07-20 Honeywell International Inc. Organic light emitting diode (OLED) having improved stability, luminance, and efficiency
WO2006065965A1 (en) * 2004-12-17 2006-06-22 Honeywell International, Inc. Organic light emitting diode (oled) having improved stability, luminance and efficiency
US20080284325A1 (en) * 2005-11-07 2008-11-20 Lg Chem, Ltd. Organic electroluminescent device and method for preparing the same
US8680693B2 (en) 2006-01-18 2014-03-25 Lg Chem. Ltd. OLED having stacked organic light-emitting units
US20090009101A1 (en) * 2006-01-18 2009-01-08 Kang Min-Soo Oled Having Stacked Organic Light-Emitting Units
EP1982562A1 (en) * 2006-02-06 2008-10-22 LG Chem, Ltd. Organic light emitting device using inorganic insulating layer as an electron injecting layer and method for preparing the same
US20090021159A1 (en) * 2006-02-06 2009-01-22 Jung-Hyoung Lee Organic Light Emitting Device Using Inorganic Insulating Layer as an Electron Injecting Layer and Method for Preparing the Same
EP1982562A4 (en) * 2006-02-06 2011-10-26 Lg Chemical Ltd Organic light emitting device using inorganic insulating layer as an electron injecting layer and method for preparing the same
US7982393B2 (en) * 2006-02-06 2011-07-19 Lg Chem, Ltd. Organic light emitting device using inorganic insulating layer as an electron injecting layer and method for preparing the same
KR100897762B1 (en) * 2007-04-07 2009-05-15 김용성 ORGANIC LIGHT EMITTING DEVICE USING THE TRANSPARENT CONDUCTING ELECTRODE OF ZnO THIN FILM
US20090091242A1 (en) * 2007-10-05 2009-04-09 Liang-Sheng Liao Hole-injecting layer in oleds
US20110309349A1 (en) * 2009-08-07 2011-12-22 Mitsui Mining & Smelting Co., Ltd. Anode structure for use in organic el device, production method thereof and organic el device
US8258508B2 (en) * 2009-08-07 2012-09-04 Mitsui Mining & Smelting Co., Ltd. Anode structure for use in organic EL device, production method thereof and organic EL device
US20150008394A1 (en) * 2013-07-02 2015-01-08 Samsung Display Co., Ltd. Organic light emitting diode display
US9391124B2 (en) 2013-07-02 2016-07-12 Samsung Display Co., Ltd. Organic light emitting diode display
US9711579B2 (en) 2013-07-02 2017-07-18 Samsung Display Co., Ltd. Organic light emitting diode display

Also Published As

Publication number Publication date
US6351067B2 (en) 2002-02-26

Similar Documents

Publication Publication Date Title
US6351067B2 (en) Organic electroluminescent device with improved hole injecting structure
US6208077B1 (en) Organic electroluminescent device with a non-conductive fluorocarbon polymer layer
US6278236B1 (en) Organic electroluminescent devices with electron-injecting layer having aluminum and alkali halide
US6392250B1 (en) Organic light emitting devices having improved performance
KR100329571B1 (en) Organic electroluminescent device
US6392339B1 (en) Organic light emitting devices including mixed region
US6069442A (en) Organic electroluminescent device with inorganic electron transporting layer
Zhou et al. Enhanced hole injection into amorphous hole‐transport layers of organic light‐emitting diodes using controlled p‐type doping
JP3327558B2 (en) Organic / inorganic alloys used to improve organic electroluminescent devices
US7830089B2 (en) Electronic device with a layer structure of organic layers
KR100641900B1 (en) Light emitting component comprising organic layers
US7733008B2 (en) Organic light emitting diodes (OLEDs) including a barrier layer and method of manufacture
US5811833A (en) Electron transporting and light emitting layers based on organic free radicals
US6806491B2 (en) Organic light-emitting devices
US20090009072A1 (en) Organic Light Emitting Device With a Plurality of Organic Electroluminescent Units Stacked Upon Each Other
KR20040018503A (en) Light emitting component with organic layers
KR19980070765A (en) Organic electroluminescent element
KR20030027819A (en) Organic light-emitting diode having an interface layer between the hole-transporting layer and the light-emitting layer
KR20020092977A (en) High efficiency transparent organic light emitting devices
WO2007071450A1 (en) Electronic device with a layer structure of organic layers
US7368181B2 (en) Organic electroluminescent elements including triazine derivative compounds
EP0914025B1 (en) A multistructured electrode for use with electroluminescent devices
KR100367956B1 (en) Organic electro luminescence device
EP1560469A1 (en) Organic electroluminescent device
US8491820B2 (en) Process for growing an electron injection layer to improve the efficiency of organic light emitting diodes

Legal Events

Date Code Title Description
AS Assignment

Owner name: CITY UNIVERSITY OF HONG KONG, HONG KONG

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:LEE, SHUIT-TONG;DENG, ZHEN-BO;GAMBLING, WILLIAM ALEXANDER;REEL/FRAME:009894/0276;SIGNING DATES FROM 19981229 TO 19990112

STCF Information on status: patent grant

Free format text: PATENTED CASE

AS Assignment

Owner name: CITY RESEARCH LIMITED, HONG KONG

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:CITY UNIVERSITY OF HONG KONG;REEL/FRAME:014108/0717

Effective date: 20030514

AS Assignment

Owner name: CITYU RESEARCH LIMITED, HONG KONG

Free format text: CORRECTIVE ASSIGNMENT TO CORRECT THE ASSIGNEE'S NAME. DOCUMENT PREVIOUSLY RECORDED ON REEL 014108 FRAME 0717;ASSIGNOR:CITY OF UNIVERSITY OF HONG KONG;REEL/FRAME:014830/0316

Effective date: 20030514

Owner name: CITYU RESEARCH LIMITED, HONG KONG

Free format text: CORRECTIVE ASSIGNMENT TO CORRECT THE ASSIGNEE'S NAME. DOCUMENT PREVIOUSLY RECORDED ON REEL 014108 FRAME 0717. ASSIGNOR HEREBY CONFIRMS THE ASSIGNMENT OF THE ENTIRE INTEREST;ASSIGNOR:CITY UNIVERSITY OF HONG KONG;REEL/FRAME:014830/0316

Effective date: 20030514

FEPP Fee payment procedure

Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

FPAY Fee payment

Year of fee payment: 4

FPAY Fee payment

Year of fee payment: 8

FEPP Fee payment procedure

Free format text: PAT HOLDER NO LONGER CLAIMS SMALL ENTITY STATUS, ENTITY STATUS SET TO UNDISCOUNTED (ORIGINAL EVENT CODE: STOL); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

REFU Refund

Free format text: REFUND - PAYMENT OF MAINTENANCE FEE, 12TH YR, SMALL ENTITY (ORIGINAL EVENT CODE: R2553); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

FPAY Fee payment

Year of fee payment: 12