WO2007071451A1 - Dispositif photoemetteur organique a empilement d'unites electroluminescentes organiques - Google Patents

Dispositif photoemetteur organique a empilement d'unites electroluminescentes organiques Download PDF

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Publication number
WO2007071451A1
WO2007071451A1 PCT/EP2006/012517 EP2006012517W WO2007071451A1 WO 2007071451 A1 WO2007071451 A1 WO 2007071451A1 EP 2006012517 W EP2006012517 W EP 2006012517W WO 2007071451 A1 WO2007071451 A1 WO 2007071451A1
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WIPO (PCT)
Prior art keywords
type doped
layer
organic
organic electroluminescent
transporting layer
Prior art date
Application number
PCT/EP2006/012517
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English (en)
Inventor
Philipp Wellmann
Sven Murano
Ansgar Werner
Gufeng He
Original Assignee
Novaled Ag
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 EP06001230A external-priority patent/EP1804308B1/fr
Application filed by Novaled Ag filed Critical Novaled Ag
Priority to US12/158,582 priority Critical patent/US20090009072A1/en
Publication of WO2007071451A1 publication Critical patent/WO2007071451A1/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
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/19—Tandem OLEDs
    • 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]
    • H10K50/14—Carrier transporting layers
    • H10K50/15—Hole transporting layers
    • H10K50/155—Hole transporting layers comprising dopants
    • 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]
    • H10K50/14—Carrier transporting layers
    • H10K50/16—Electron transporting layers
    • H10K50/165—Electron transporting layers comprising dopants

Definitions

  • An organic light emitting device with a plurality of organic electroluminescent units stacked upon each other
  • the invention relates to an organic light emitting device with a plurality of organic electrolu- minescent units stacked upon each other.
  • Organic electroluminescent (EL) devices are becoming of increasing interest for applications in the field of displays or lighting sources.
  • Such organic light emitting devices or organic light emitting diodes (OLEDs) are electronic devices, which emit light if an electric potential is applied.
  • the structure of such OLEDs comprises, in sequence, an anode, an organic electrolumines- cent medium and a cathode.
  • the electroluminescent medium which is positioned between the anode and the cathode, is commonly comprised of an organic hole-transporting layer (HTL) and an electron- transporting layer (ETL). The light is then emitted near the interface between TTL and ETL.
  • EML organic light emitting layer
  • the EML may consist of a host material doped with a guest material, however neat light emitting layers may also be formed from a single material. Fur- thermore, the EML may contain two or more sublayers.
  • the layer structure is then denoted as HTL / EML / ETL.
  • Further developments show multilayer OLEDs which additionally contain a hole-injection layer (HIL), and / or an electron-injection layer (EIL), and / or a hole- blocking layer (HBL), and / or an electron-blocking layer (EBL), and or other types of inter- layers between the EML and the HTL and / or ETL, respectively.
  • HIL hole-injection layer
  • EIL electron-injection layer
  • HBL hole- blocking layer
  • EBL electron-blocking layer
  • a further improvement of the OLED performance can be achieved by the use of doped charge carrier transport layers as disclosed in EP 0 498 979 Al .
  • the ETL is doped with an electron donor such as an alkali metal
  • the HTL is doped with an electron acceptor, such as F4-TCNQ.
  • OLEDs using doped transport layers are commonly known as PIN-OLEDs. They feature extremely low operating voltages, often being close to the thermodynamical limit set by the wavelength of the emitted light.
  • stacked or cascaded OLED structures have been proposed, in which several individual OLEDs are vertically stacked.
  • the improvement of the OLED performance in such stacked organic electroluminescent devices is generally attributed to an overall reduction of the operating current density combined with an increased operating voltage, as the individual OLEDs are connected in a row.
  • Such a design leads to lower stress of the organic layers, since current injected and transported within the organic layers is reduced.
  • the stacking of several OLED units in one device allows a mixing of different colors in one device, for example in order to generate white light emitting devices.
  • Such stacked or cascaded organic electroluminescent devices can for example be done by vertically stacking several OLEDs, which are each independently connected to a power source and which therefore are able to independently emit light of the same or of dif- ferent color.
  • This design was proposed to be used in full color displays or other emission devices with an increased integrated density (cf. US-A-5,703,436, US-A-6,274,980).
  • alternative designs were proposed, in which several OLEDs are vertically stacked without individually addressing each OLED in the unit stack.
  • each of the single OLED units stacked by means of the connecting units is made of a two layer structure comprising a hole-transporting layer, and an electron-transporting layer.
  • the document EP 1 339 112 A2 discloses an organic electroluminescent device having stacked electroluminescent units.
  • the stacked organic electroluminescent device comprises an anode, a cathode, a plurality of organic electroluminescent units disposed between the anode and the cathode, and a doped organic connectors disposed between each adjacent organic electroluminescent unit.
  • an organic light emitting device comprising: an an- ode; a cathode; and a plurality of organic electroluminescent units provided upon each other in a stack or an inverted stack between said anode and said cathode each of said organic electroluminescent units comprising an electroluminescent zone; wherein for m > 2: at least organic electroluminescent units not adjacent to the anode or the cathode comprise a single p-type doped hole transporting-layer (HTL), and a single n-type doped electron- transporting layer (ETL), where the electroluminescent zone (EML) is formed between the single p-type doped hole transporting layer (HTL) and the single n-type doped electron transporting layer (ETL); in the stack or the inverted stack the single n-type doped electron-transporting layer (ETL) of the k ⁇ (2 ⁇ k ⁇ m-2) organic electroluminescent unit is directly followed by the single p-
  • a second electroluminescent unit comprises as a single p-type doped hole transporting- layer (HTL);
  • the single n-type doped electron-transporting layer (ETL) of the first electroluminescent unit is in contact with the single p-type doped hole-transporting layer (HTL) of the second organic electroluminescent unit.
  • the invention enables fabrication of stacked organic light emitting devices where the introduction of any kind of intermediate layer in between the individual OLEDs can be omitted. This will allow for a cheaper production of stacked OLED devices as no additional material deposition steps need to be introduced into the production process, reducing the overall numbers of layers within the device as well as possibly also the number of materials used within the device.
  • the fixation in the p-type doped HTL is ensured by a high molecular weight of the p-dopant (> 300 g / mol) preventing it from a migration into the n-type doped ETL.
  • the fixation of the n-dopant is ensured by the formation of a complex between the matrix material, e.g. BPhen or a similar material and the dopant, e.g. Cs or any other alkali metal or alternatively by using an n-dopant with a high molecular weight (> 300 g / mol).
  • the matrix material e.g. BPhen or a similar material
  • the dopant e.g. Cs or any other alkali metal
  • an n-dopant with a high molecular weight > 300 g / mol
  • the contact region of the base electrode and the electrolumi- nescent unit adjacent to the base electrode and the contact region between the electroluminescent unit adjacent to the top electrode and the top electrode maybe formed in a different way to optimize to interface of the organic layers to the conductive electrodes.
  • a carbon fluoride interlayer (CF x ) on top of an ITO electrode improves the stability of the interface to the adjacent hole transport layer.
  • LiF or low work function materials may improve the injection from a top electrode to the adjacent electron transport layer.
  • beneficial interlayers may be used in conjunction of the present invention.
  • the stacked organic electroluminescent units com- prise at least one of the following layers: an hole-injection layer (HIL), an electron-injection layer (EIL), an interlayer in between said p-type doped hole-transporting layer and said electroluminescent zone, and a further interlayer between said n-type doped electron-transporting layer and said electroluminescent zone.
  • HIL hole-injection layer
  • EIL electron-injection layer
  • the electroluminescent unit would be denoted p-HTL / EML / n-ETL.
  • the electroluminescent units may also consist of multilayer structures that are well known in the art, such as p-HTL / EBL or HIL / EML / n-ETL, or p-HTL / EML / HBL or EIL / n-ETL or any other multilayer architecture which allows to have, as described above, the n-ETL and the p-HTL of adjacent electroluminescent units in direct contact in the stack.
  • the layer structure within the light emitting zone might consist of one or more consecutive layers containing one or more organic host materials and one or more fluorescent or phosphorescent electroluminescent emitter materials. Nevertheless, one or more of the layers of the EML may not contain fluorescent or phosphorescent electroluminescent emitter materials.
  • the EML may be formed from small organic molecules, i.e. molecules that are small enough to be vacuum deposited, e.g. by sublimation or evaporation, or from organic polymers. Different EMLs within the organic electroluminescent units of the organic light emitting device may be made of different materials.
  • the p-type doped hole transporting-layer (HTL) and the n-type doped electron-transporting layer (ETL) are made of a matrix material which is the same material for the p-type doped hole transporting-layer (HTL) and the n-type doped electron- transporting layer (ETL), where for p-type doped hole transporting-layer (HTL) the matrix material is p- doped, and for the n-type doped electron-transporting layer (ETL) the matrix material is n- doped.
  • Matrix materials which can be used are known as such, for example from Harada et al. (Phys. Rev. Lett. 94, 036601 (2005)).
  • Fig. 1 is a schematic cross sectional view of a light emitting device with a plurality of stacked organic electroluminescent units
  • Fig. 2 is a schematic cross sectional view of an individual organic electroluminescent unit
  • Fig. 3 is a diagram showing the power efficiency versus luminance of a light emitting device in accordance with the invention and a reference device.
  • an organic light emitting device 10 with a plurality of stacked organic electroluminescent units comprises an anode 2 which is provided on a substrate 1, a cathode 4, and a number of m (m > 2) organic electroluminescent units (EL units) 3.1, ..., 3.m which are also referred to as OLED units.
  • the organic electroluminescent units 3.1, ..., 3.m are directly stacked upon each other, forming a cascade / stack of organic electroluminescent units.
  • the cathode is provided on a substrate, and the an- ode is provided as a top electrode.
  • Fig. 2 is a schematic cross sectional view of an individual organic electroluminescent unit.
  • Each individual electroluminescent unit / OLED unit comprises at least a p-type doped hole- transporting layer (HTL) 20, an electroluminescent layer or zone (EML) 21, and an n-type doped electron-transporting layer (ETL) 22.
  • the n-type doped electron-transporting layer 22 consists of an organic main material doped with a donor-type substance
  • the p-type doped hole-transporting layer 20 consists of an organic main material doped with an acceptor-type substance.
  • the dopant substance is a high molecular weight material (> 300 g / mol), and / or in the case of n-type doping an alkali metal.
  • the doping ratio shall be as low that all Cs or alkali metal molecules form a complex with the matrix molecules, preferentially below 1 :3 (Cs to matrix) in molecular ratio.
  • the gas phase ionization potential of the dopant shall be ⁇ 4,0 eV, more preferentially ⁇ 3,8 eV.
  • the OLED units might furthermore comprise additional hole-injection layer(s) (HIL) and / or electron injection layer(s) (EIL) and / or hole-blocking layer(s) (HBL) and / or electron- blocking layer(s) (EBL) and / or other type(s) of interlayers between the EML and the HTL and / or the ETL.
  • HIL hole-injection layer
  • EIL electron injection layer
  • HBL hole-blocking layer
  • EBL electron- blocking layer
  • interlayers may act as a suppression of exciplex formation at the interface of transport layers and emission zone or as confinement for the excitons generated. Preferentially they exhibit a higher hole or, respectively, electron mobility and electron or, respectively, hole blocking behaviour.
  • the thickness of these interlayers is typically in the range of about 1 to 20 nm.
  • the layer structure within the electroluminescent units might consist of one or more consecutive layers containing one or more organic host materials and one or more fluorescent or phosphorescent electroluminescent emitter materials.
  • the EML may be formed from small organic molecules or from organic polymers. Different EMLs within the EL units of the organic light emitting device 10 may be made of different materials.
  • the organic light emitting device 10 with m (m > 2) EL units consists of:
  • bottom electrode e.g. hole injecting anode
  • top electrode 4 e.g. electron injecting cathode
  • each electroluminescent unit comprises at least the following layers: a p-type doped hole-transporting layer (HTL) close to the bottom electrode (anode 2 in Fig. 1), an n-type doped electron-transporting layer (ETL) close to the top electrode (cathode 4 in Fig. 1) and an electroluminescent layer (EML) in between (cf. Fig. 2).
  • HTL hole-transporting layer
  • ETL n-type doped electron-transporting layer
  • EML electroluminescent layer
  • the p-type doped hole-transporting layer is close to the anode, and the n-type doped electron-transporting layer is close to the cathode.
  • the n-type doped electron-transporting layer of the k th electroluminescent unit (1 ⁇ k ⁇ m) is directly connected with the p-type doped hole- transporting layer of the (k+l)* electroluminescent unit without any intermediate layer.
  • EBL electron or a hole blocking layer
  • HTL p-type doped hole-transporting layer
  • ETL electron-transporting layer
  • the organic layers and metal are deposited by thermal evaporation onto patterned and pre- cleaned indium tin oxide (ITO) coated glass substrates in an ultrahigh vacuum system at 10 "7 mbar base pressure without breaking vacuum.
  • ITO indium tin oxide
  • the deposition rate and the thickness of the deposited layer are controlled by using a thickness monitor.
  • the EML is made of layers 2), and 3).
  • This brightness is reached at an operating voltage of 4,15 V, much lower than those without p-type doped hole-transporting layers and n-type doped electron-transporting layers.
  • the current efficiency of the device is 51,3 cd/A.
  • the power efficiency at this brightness is 38,8 lm/W.
  • Example 2 (stacked electroluminescent units ' )
  • the EML is provided by the layers 2), 3) and 6), 7), respectively.
  • This is a stacked green phosphorescent PIN OLED consisting of two PIN OLED units and having color coordinates of 0,32/0,63 at a brightness of 1000 cd/m 2 . This brightness is reached at an operating voltage of 9,2 V.
  • the current efficiency of the device at a brightness of 1000 cd/m 2 is 116,6 cd/A, the power efficiency at this brightness is 39,7 lm/W.
  • the operating voltage of the stacked green PIN OLED is more than twice as high as for the non stacked reference device, however the current efficiency is also increased by more than a factor of two.
  • the power efficiency versus luminance plot in figure 3 shows, that both the non stacked green PIN reference OLED device and the stacked green PIN OLED reach similar power efficiencies at the same luminance levels.

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

Abstract

La présente invention concerne un dispositif photoémetteur organique comprenant une anode (2), une cathode (4) et une pluralité d'unités électroluminescentes organiques (3.1,..., 3.m; m = 2). Ces unités sont empilées en ordre direct ou inverse entre l'anode (2) et la cathode (4). Chaque unité (3.1,..., 3.m) comprend une zone électroluminescente. Certaines des unités électroluminescentes organiques (3.2,..., 3.m) comprennent une couche de transport de trous dopée p et/ou une couche de transport d'électrons dopée n.
PCT/EP2006/012517 2005-12-23 2006-12-22 Dispositif photoemetteur organique a empilement d'unites electroluminescentes organiques WO2007071451A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US12/158,582 US20090009072A1 (en) 2005-12-23 2006-12-22 Organic Light Emitting Device With a Plurality of Organic Electroluminescent Units Stacked Upon Each Other

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
EP05028297 2005-12-23
EP05028297.9 2005-12-23
EP06001230.9 2006-01-20
EP06001230A EP1804308B1 (fr) 2005-12-23 2006-01-20 Dispositif organique émetteur de lumière ayant plusieurs unités électroluminescentes organiques empilées les unes sur les autres

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8564195B2 (en) * 2007-02-09 2013-10-22 Samsung Display Co., Ltd. Display device
US9172042B2 (en) 2008-10-30 2015-10-27 Osram Opto Semiconductors Gmbh Organic, radiation-emitting component and method for producing such a component

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1339112A2 (fr) * 2002-02-15 2003-08-27 Eastman Kodak Company Dispositif électroluminescent organique comportant des éléments électroluminescents empilés
EP1478025A2 (fr) * 2003-05-13 2004-11-17 EASTMAN KODAK COMPANY (a New Jersey corporation) Dispositifs organiques électroluminescents en cascade ayant des unités de connexion à couches organiques de type n et de type p

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1339112A2 (fr) * 2002-02-15 2003-08-27 Eastman Kodak Company Dispositif électroluminescent organique comportant des éléments électroluminescents empilés
EP1478025A2 (fr) * 2003-05-13 2004-11-17 EASTMAN KODAK COMPANY (a New Jersey corporation) Dispositifs organiques électroluminescents en cascade ayant des unités de connexion à couches organiques de type n et de type p

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8564195B2 (en) * 2007-02-09 2013-10-22 Samsung Display Co., Ltd. Display device
US9172042B2 (en) 2008-10-30 2015-10-27 Osram Opto Semiconductors Gmbh Organic, radiation-emitting component and method for producing such a component

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