WO2003094255A2 - Diodes electroluminescentes organiques a contraste ameliore - Google Patents

Diodes electroluminescentes organiques a contraste ameliore Download PDF

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Publication number
WO2003094255A2
WO2003094255A2 PCT/CA2003/000653 CA0300653W WO03094255A2 WO 2003094255 A2 WO2003094255 A2 WO 2003094255A2 CA 0300653 W CA0300653 W CA 0300653W WO 03094255 A2 WO03094255 A2 WO 03094255A2
Authority
WO
WIPO (PCT)
Prior art keywords
layer
thickness
disposed behind
electroluminescent
absorptive
Prior art date
Application number
PCT/CA2003/000653
Other languages
English (en)
Other versions
WO2003094255A3 (fr
Inventor
David J. Johnson
Richard P. Wood
Peter G. Hofstra
Original Assignee
Luxell Technologies Inc.
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
Priority claimed from US10/383,560 external-priority patent/US20030214230A1/en
Application filed by Luxell Technologies Inc. filed Critical Luxell Technologies Inc.
Priority to AU2003229422A priority Critical patent/AU2003229422A1/en
Publication of WO2003094255A2 publication Critical patent/WO2003094255A2/fr
Publication of WO2003094255A3 publication Critical patent/WO2003094255A3/fr

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Classifications

    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/80—Constructional details
    • H10K59/8791—Arrangements for improving contrast, e.g. preventing reflection of ambient light

Definitions

  • the present invention relates generally to organic light emitting diodes
  • OLED organic light-emitting diode
  • a first aspect of the invention provides an electroluminescent device for displaying an image to a viewer in front of the device, comprising a front anode layer being the front and being substantially transparent to electroluminescent light.
  • the device also comprises an organic electroluminescent layer disposed behind the anode layer and a buffer layer disposed behind the electroluminescent layer.
  • the buffer layer made of a material selected from the group consisting of LiF, LiO, or Li, Ca, or Ba, or compounds of Li, Ca, or Ba.
  • the device also includes a dark layer for reducing reflected ambient light using optical interference.
  • the dark layer is disposed behind the buffer layer.
  • a reflective rear cathode layer is disposed behind the dark layer.
  • a second aspect of the invention provides an electroluminescent device for displaying an image to a viewer in front of the device, comprising a front anode layer made from indium tin oxide (ITO) and having a thickness of about 1200 A.
  • ITO indium tin oxide
  • the ITO is the front of the device and is substantially transparent to electroluminescent light.
  • the device also includes a first buffer layer, disposed behind the anode layer, made from CuPc having a thickness of about 250 A.
  • the device also includes a hole transport layer disposed behind the first buffer layer and made from NPB having a thickness of about 450 A.
  • An organic electroluminescent layer is disposed behind the hole transport layer and is made from tris(8- quinolinolato aluminum) (Alq3) having a thickness of about 600 A.
  • An electron transport layer is disposed behind the electroluminescent layer, and there is a second buffer layer disposed behind the electron transport layer.
  • a third buffer layer is disposed behind the electroluminescent layer and is made from a material selected from the group consisting of LiF, LiO, or Li, Ca, or Ba, or from a compounds of Li, Ca, or Ba.
  • the third buffer layer has a thickness of about 10 A.
  • a dark layer comprising a partially reflective layer, an absorptive-fransmissive layer and a reflecting layer is disposed behind the second buffer layer.
  • a rear cathode layer is disposed behind the dark layer, made from aluminum (Al) having a thickness of about 1500 A.
  • the partially reflective layer can be made from chromium, and have a thickness of between about zero to about 100 A, or from about zero to about 40 A, or have a thickness of about 12 A.
  • the absorptive-transmissive layer can be made from chromium silicon monoxide.
  • the absorptive-transmissive chromium silicon monoxide layer can have a thickness of between about 200 A to about 800 A, or can have a thickness of between about 400 A to about 600 A, or can have a thickness of about 500 A.
  • a third aspect of the invention provides an electroluminescent device for displaying an image to a viewer in front of the device, comprising a front anode layer being the front and being substantially transparent to electroluminescent light.
  • An organic electroluminescent layer is disposed behind the anode layer.
  • a dark layer comprising a partially reflective layer, an absorptive-transmissive layer and a reflecting layer is disposed behind the organic electroluminescent layer.
  • the partially-reflective layer is co-deposited with a material selected from the group consisting of LiF, LiO, Ca, or Ba, or a compound of Li, Ca or Ba.
  • a reflective rear cathode layer is disposed behind the dark layer.
  • the co-deposited material is LiF
  • it can comprise about
  • partially-reflective layer 5% to about 60% of the partially-reflective layer, or it can comprise about 30% to about 50% of the partially-reflective layer.
  • Figure 1 is a schematic diagram of a cross-section of a bottom emitting electroluminescent device in accordance with the first embodiment of the invention.
  • a bottom emitting electroluminescent device in accordance with the first embodiment of the invention is indicated generally at 10 in Figure 1.
  • Device 10 comprises a substrate 20 facing a viewer 15, an electroluminescent transmitting anode 22, a first buffer layer 24, a hole transport layer 26, an electroluminescent layer 28, an electron transport layer 30, a second buffer layer 32, a third buffer layer 34, a dark layer 36 composed of three layers 36a, 36b and 36c, and a reflecting cathode layer 38 disposed as shown in Figure 1.
  • Device 10 is connected to a current source (not shown) via anode 22 and cathode 38 in order to drive a constant current through device 10.
  • Substrate 20 is glass, plastic or other transparent material of suitable thickness for depositing the layers 22 - 38 using vacuum deposition, spin-coating or other means.
  • Electroluminescent transmitting anode 22 is any conducting material which is transparent to at least a portion of emitted electroluminescent light, such as indium tin oxide (ITO) or zinc oxide (ZnO).
  • ITO indium tin oxide
  • ZnO zinc oxide
  • anode 22 is a layer of ITO having a thickness of about twelve-hundred angstroms (1200 A). Other suitable materials and appropriate thicknesses can be determined by those skilled in the art.
  • First buffer layer 24 is made of Cupric Phthalocynine (CuPc) having a thickness of about two hundred and fifty angstroms (250 A). Other suitable materials and appropriate thicknesses can be determined by those skilled in the art. The function of this layer is to regulate the hole transportation through the device.
  • CuPc Cupric Phthalocynine
  • Hole transport layer 26 is made of N,N'-Di(naphthalen-l-yl)-N,N'diphenyl- benzidine (NPB; also known as naphthalene diphenyl benzidine), having a thickness of about four hundred and fifty angstroms (450 A). Other suitable materials and appropriate thicknesses can be determined by those skilled in the art. The function of this layer is to facilitate hole transportation through the device.
  • Electroluminescent layer 28 and electron transport layer 30 is typically deposited as a single layer of an organic electroluminescent material such as Tris-(8- hydroxyquinoline) aluminum (Alq3) having an appropriate thickness.
  • layer 28 and layer 30 are Alq3 having a combined thickness of about six hundred angstroms (600 A) although those of skilled in the art will be able to determine other appropriate thicknesses.
  • the function of layer 28 is to emit light, while the function of layer 30 is to facilitate hole transport through device 10.
  • Second buffer layer 32 is made from CuPc with an appropriate thickness as known in the art. In the present embodiment, layer 32 is included to protect the electroluminescent layer during sputter deposition of additional layers of device 10. However, where sputter deposition is not used it can be desired to omit layer 32.
  • Third buffer layer 34 is for matching the work function of electroluminescent layer 28 and dark layer 36.
  • Third buffer layer 34 is made of lithium fluoride (LiF) having a thickness of about five to about twenty angstroms (5-20 A), but in a presently preferred embodiment layer 34 has a thickness of about five angstroms (5 A).
  • the thickness of lithium fluoride for third buffer layer 34 can be from about three to about twenty-five angstroms (3 - 25 A), or it can be from out ten to about fifteen angstroms (10 - 15 A).
  • third buffer layer 34 can be made from lithium oxide (LiO) and have a thickness of the ranges previously mentioned. It is to be understood that low-work-function based materials can be used, such as Ca or Ba, or compounds thereof from low- work-function based materials.
  • LiF dissociates into its component species. Since Li alone has a very low work function and readily gives up electrons, an effective electrical match between electroluminescent layer 28 and partially reflective layer 36a (discussed further below) of dark layer 36 can be provided. Each Li atom (or ion) can thereby act as a source to inject electrons into the organic device freeing partially-reflective layer 36a from having to perform this function, in conjunction with performing its partially-reflective function.
  • dark layer 36 is composed of three layers: a partially-reflective layer 36a, an absorptive-transmissive layer 36b and a reflective layer 36c.
  • Layer 36a is made from chromium and is disposed behind buffer layer 34.
  • Layer 36a can have a thickness of between about zero to about one hundred angstroms (0-100 A).
  • Layer 36a can also have a thickness of between about zero to about forty angstroms (0-40 A).
  • chromium layer 36a has a thickness of about twelve angstroms (12 A).
  • Layer 36b, disposed behind layer 36a is made from chromium silicon monoxide preferably having a thickness of between about two hundred to about eight hundred angstroms (200-800 A). More preferably, layer 36b can have of thickness of between about four hundred to six hundred angstroms (400-600 A). In a presently preferred embodiment, layer 36b has thickness of about five hundred angstroms (500 A).
  • Layer 36c disposed behind layer 36b, is also made from chromium preferably having a thickness of between about zero to about fifteen-hundred angstroms (0 A-1500 A).
  • layer 36c has a thickness of about two hundred fifty angstroms (250 A).
  • Cathode layer 38 is aluminum (Al) and has a thickness of about fifteen- hundred angstroms (1500 A), and in the present embodiment it is reflective. Other suitable materials and appropriate thicknesses can be determined by those skilled in the art.
  • partially-reflective layer 36a is made from aluminum
  • absorptive-transmissive layer 36b is made from aluminum silicon monoxide
  • reflective layer 36c is made from aluminum.
  • Layer 36a can have a thickness of between about zero to about fifty angstroms (0-50 A).
  • Layer 36a can have a thickness of between about ten to about thirty-five angstroms (10-35 A).
  • aluminum layer 36a has a thickness of about twenty-five angstroms (25 A).
  • Layer 36b behind layer 36a is made from aluminum silicon monoxide, preferably, having a thickness of between about two-hundred-and-fifty to about five-hundred angstroms (250-500 A).
  • layer 36b is of thickness of between about two-hundred-and-seventy- five to about four-hundred-and-fifty angstroms (275-450 A). More preferably, layer 36b is of thickness of between about three-hundred-and-twenty-five to about four-hundred angstroms (325-400 A). In a presently preferred embodiment, layer 36b has thickness of about three- hundred-and-seventy angstroms (370 A).
  • Layer 36c, disposed behind layer 36b is another layer of aluminum, preferably having a thickness between about 1000 A to about 1500 A. (When layer 36c is made of aluminum it is contemplated that cathode layer 38 can be eliminated in favour of using layer 36c as the cathode.)
  • the appropriate thicknesses and materials are chosen to minimize the reflection of the device at this wavelength. However, it will occur to those skilled in the art that other wavelengths can be selected, as desired, and the appropriate material thickness can be calculated.
  • incident light L on layer 36a is partially reflected as per reflection Rl, and partially transmitted through layers 36a and 36b.
  • the light traveling through layers 36a and 36b is shifted in phase through layer 36b, and reflected off of layer 36c as reflection R2, so that it is out of phase with reflection Rl.
  • the phase mismatch of reflection Rl and reflection R2 at the surface of layer 36a cause a destructive interaction of these two reflections Rl and R2, causing at least some reduction in incident light. Where the phase shift is about one-hundred-and-eighty degrees between reflection Rl and reflection R2, there can be a substantial reduction of incident light.
  • a compound containing the very low work function material e.g. LiF
  • a compound containing the very low work function material can be incorporated directly into partially-reflective layer 36a through co- deposition technique, and thereby eliminate buffer layer 34.
  • the relative amounts of LiF and partially-reflective material can be in the range of from about 5% to about 60% LiF, or can be from about 30% to about 50% LiF.
  • desired display performance can be achieved without having to deposit an additional layer; additionally, the presence of the LiF can reduce and/or obviate the need to work function match dark layer 36 with electroluminescent layer 28.
  • the work function of partially-reflective layer 36a is modified to match electroluminescent layer 28.
  • the LiF dissociates during deposition, allowing the Li to act as a source of electrons within the partially reflective layer 36a. With the presence of an excess of LiF, enough non-dissociated insulator is present to impart insulating properties to the layer. If too little LiF is applied, there is not enough Li near the organic surface to make a strong impact on electron injection. The foregoing considerations can be used to choose an appropriate or desired amount of LiF to use.
  • dark layer 36 While only specific combinations of the various features and components of the present invention have been discussed herein, it will be apparent to those of skill in the art that desired subsets of the disclosed features and components and/or alternative combinations of these features and components can be utilized, as desired.
  • dark layer 36 can include a number of sub-layers, it is to be understood that other arrangements of dark layer 36 can be effected.
  • dark layer 36 can include a single layer.
  • dark layer 36 can be configured or structured in any manner to provide at least some destructive optical interference of incident light L, as previously discussed per reflections Rl and R2 shown in Figure 1.
  • reflective layer 36c can be omitted where cathode 38 is reflective.
  • the present invention provides a novel contrast enhanced OLED having a buffer layer made from LiO, LiF or the like that allows a flexible range of choices for the dark layer that is placed behind the buffer layer. Since the thickness of the low work function material buffer layer, such as LiF, is very thin, and, as this and related materials are substantially transparent, there is no additional optical effect that need be compensated for in partially reflective layer placed in front of the absorptive-transmissive layer.

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  • Electroluminescent Light Sources (AREA)

Abstract

La présente invention a trait à un dispositif à diodes électroluminescentes à contraste amélioré présentant une couche de fluorure de lithium ou d'oxyde de lithium déposée au sein d'un empilement du dispositif. Le fluorure de lithium ou l'oxyde de lithium est déposé ultérieurement en ajout, ou conjointement, à une ou plusieurs couches d'amélioration de contraste qui se trouvent également dans l'empilement du dispositif.
PCT/CA2003/000653 2002-05-03 2003-05-02 Diodes electroluminescentes organiques a contraste ameliore WO2003094255A2 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2003229422A AU2003229422A1 (en) 2002-05-03 2003-05-02 Contrast enhanced oleds

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
US37720802P 2002-05-03 2002-05-03
US60/377,208 2002-05-03
US37763702P 2002-05-06 2002-05-06
US60/377,637 2002-05-06
US10/383,560 US20030214230A1 (en) 2002-05-03 2003-03-10 Dark layer for an electroluminescent device
US10/383,560 2003-03-10

Publications (2)

Publication Number Publication Date
WO2003094255A2 true WO2003094255A2 (fr) 2003-11-13
WO2003094255A3 WO2003094255A3 (fr) 2004-02-05

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1752954A1 (fr) * 2005-08-11 2007-02-14 Borg Instruments AG Dispositif d'affichage
US8044571B2 (en) 2005-12-14 2011-10-25 General Electric Company Electrode stacks for electroactive devices and methods of fabricating the same

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5049780A (en) * 1988-12-02 1991-09-17 National Research Council Of Canada Optical interference, electroluminescent device having low reflectance
JP2000315582A (ja) * 1999-05-06 2000-11-14 Denso Corp 有機ｅｌ素子
WO2000079616A1 (fr) * 1999-06-18 2000-12-28 Isis Innovation Limited Ecran plat a contraste ameliore
WO2001008240A1 (fr) * 1999-07-27 2001-02-01 Luxell Technologies Inc. Dispositif organique electroluminescent
EP1160890A2 (fr) * 2000-05-24 2001-12-05 Eastman Kodak Company Réduction de la réflexion de lumière ambiante dans des diodes organiques émettrices de lumiére
WO2003005776A1 (fr) * 2001-07-04 2003-01-16 Luxell Technologies Inc. Dispositif electroluminescent (el) a contraste ameliore

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5049780A (en) * 1988-12-02 1991-09-17 National Research Council Of Canada Optical interference, electroluminescent device having low reflectance
JP2000315582A (ja) * 1999-05-06 2000-11-14 Denso Corp 有機ｅｌ素子
WO2000079616A1 (fr) * 1999-06-18 2000-12-28 Isis Innovation Limited Ecran plat a contraste ameliore
WO2001008240A1 (fr) * 1999-07-27 2001-02-01 Luxell Technologies Inc. Dispositif organique electroluminescent
EP1160890A2 (fr) * 2000-05-24 2001-12-05 Eastman Kodak Company Réduction de la réflexion de lumière ambiante dans des diodes organiques émettrices de lumiére
WO2003005776A1 (fr) * 2001-07-04 2003-01-16 Luxell Technologies Inc. Dispositif electroluminescent (el) a contraste ameliore

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 2000, no. 14, 5 March 2001 (2001-03-05) -& JP 2000 315582 A (DENSO CORP; KIDO JUNJI), 14 November 2000 (2000-11-14) *
WOOD ET AL: 'Optical an electrical properties of Cr-SiO thin films for flat panel displays' LUMINESCENCE AND LUMINESCENT MATERIALS. SYMPOSIUM (MATERIALS RESEARCH SOCIETY PROCEEDINGS VOL.667), LUMINESCENCE AND LUMINESCENT MATERIALS. SYMPOSIUM, SAN FRANCISCO, CA, USA, 17-19 APRIL 2001 2001, WARRENDALE, PA, USA, MATER. RES. SOC, USA, pages G7.5.1 - 6, XP008023947 ISBN: 1-55899-603-6 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1752954A1 (fr) * 2005-08-11 2007-02-14 Borg Instruments AG Dispositif d'affichage
WO2007017292A1 (fr) * 2005-08-11 2007-02-15 Johnson Controls Automotive Electronics Gmbh Ecran
US8044571B2 (en) 2005-12-14 2011-10-25 General Electric Company Electrode stacks for electroactive devices and methods of fabricating the same

Also Published As

Publication number Publication date
AU2003229422A1 (en) 2003-11-17
WO2003094255A3 (fr) 2004-02-05

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