Large area organic electronic devices having conducting...

Details Large area organic electronic devices having conducting... Large area organic electronic devices having conducting...

1999-09-03

2003-07-15

Patel, Ashok (Department: 2879)

Electric lamp and discharge devices

With luminescent solid or liquid material

Solid-state type

C313S512000, C428S917000

Reexamination Certificate

active

06593690

ABSTRACT:

TECHNICAL FIELD
This invention relates to conducting buffer layers for organic electronic devices and in particular for organic light emitting diodes (OLED)s including flexible, large area OLEDs. The invention also relates to methods for applying the buffer layer.
BACKGROUND
Organic electronic devices are articles that include layers of organic materials, at least one of which can conduct an electric current. An example of an organic electronic device is an organic light emitting diode (OLED). OLEDs, sometimes referred to as lamps, are desirable for use in electronic media because of their thin profile, low weight, and low driving voltage, i.e., less than about 20 volts. OLEDs have potential use in applications such as backlighting of graphics, pixelated displays, and large emissive graphics.
OLEDs typically consist of an organic light emitter layer and additional organic charge transport layers on both sides of the emitter, all of which are sandwiched between two electrodes: a cathode and an anode. The charge transport layers comprise an electron transporting layer and a hole transporting layer. Charge carriers, i.e., electrons and holes, are injected into the electron and hole transporting layers from the cathode and anode, respectively. Electrons are negatively charged atomic particles and holes are vacant electron energy states that behave as though they are positively charged particles. The charge carriers migrate to the emitter layer, where they combine to emit light.
FIG. 1
illustrates a type of organic light emitting diode. The diode comprises a substrate
12
, a first electrode (anode)
14
, a hole transporting layer
16
, a light emitting layer
18
, an electron transporting layer
20
, and a second electrode (cathode)
22
.
Substrate
12
may be transparent or semi-transparent and may comprise, e.g., glass, or transparent plastics such as polyolefins, polyethersulfones, polycarbonates, polyesters, and polyarylates.
Anode
14
is electrically conductive and may be optically transparent or semi-transparent. Suitable materials for this layer include indium oxide, indium-tin oxide (ITO), zinc oxide, vanadium oxide, zinc-tin oxide, gold, copper, silver, and combinations thereof.
An optional hole injecting layer (not shown) may accept holes from anode layer
14
and transmit them to hole transporting layer
16
. Suitable materials for this layer include porphyrinic compounds e.g., copper phthalocyanine (CuPc) and zinc phthalocyanine.
Hole transporting layer
16
facilitates the movement of holes from anode
14
to emitter layer
18
. Suitable materials for this layer include, e.g., aromatic tertiary amine materials described in U.S. Pat. Nos. 5,374,489 and 5, 756,224, such as 4,4′,4″-tri(N-phenothiazinyl) triphenylamine (TPTTA), 4,4′,4″-tri(N-phenoxazinyl) triphenylamine (TPOTA), N,N′-diphenyl-N,N′-bis(3-methylphenyl)[1,1′-biphenyl]-4,4′-dia (TPD), and polyvinyl carbazole.
Emitter layer
18
comprises an organic material capable of accomodating both holes and electrons. In emitter layer
18
, the holes and electrons combine to produce light. Suitable materials for this layer include metal chelate compounds, such as, e.g., tris(8-hydroxyquinolinato) aluminum (AlQ). The emission of light of different colors may be achieved by the use of different emitters and dopants in the emitter layer as described in the art (see C. H. Chen, J. Shi, and C. W. Tang “Recent Developments in Molecular Organic Electroluminescent Materials”,
Macromolecular Symposia
1997 125, 1-48).
Electron transporting layer
20
facilitates the movement of electrons from cathode
22
to emitter layer
20
. Suitable materials for this layer include, e.g., AlQ, bis( 10-hydroxybenzo(h)quinolinato) beryllium, bis(2-(2-hydroxy-phenyl)-benzolthiazolato) zinc and combinations thereof.
An optional electron injecting layer (not shown) may accept electrons from the cathode
22
and transmit them to the emitter layer
20
. Suitable materials for this layer include metal fluorides such as LiF, CsF, as well as SiO
2
, Al
2
O
3
, copper phthalocyanine (CuPc), and alkaline metal compounds comprising at least one of Li, Rb, Cs, Na, and K such as alkaline metal oxides, alkaline metal salts, e.g., Li
2
O, Cs
2
O, and LiAlO
2
.
Cathode
22
provides electrons. It may be transparent. Suitable materials for this layer include, e.g., Mg, Ca, Ag, Al, alloys of Ca and Mg, and ITO.
Polymer OLEDS may be made wherein a single layer of poly(phenylenevinylene) (PPV) or poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV) functions as layers
16
,
18
, and
20
.
Illustrative examples of known OEL device constructions include molecularly doped polymer devices where charge carrying and/or emitting species are dispersed in a polymer matrix (see J. Kido, “Organic Electroluminescent devices Based on Polymeric Materials,”
Trends in Polymer Science
, 1994, 2, 350-355), conjugated polymer devices where layers of polymers such as poly(phenylenevinylene) act as the charge carrying and emitting species (see J. J. M. Halls, D. R. Baigent, F. Cacialli, N. C. Greenham, R. H. Friend, S. C. Moratti, and A. B. Holmes, “Light-emitting and Photoconductive Diodes Fabricated with Conjugated Polymers,”
Thin Solid Films
, 1996, 276, 13-20), vapor deposited small molecule heterostructure devices (see U. S. Pat. No. 5,061,569, incorporated by reference, and C. H. Chen, J. Shi, and C. W. Tang, “Recent Developments in Molecular Organic Electroluminescent Materials,”
Macromolecular Symposia
, 1997, 125, 1-48), light emitting electrochemical cells (see Q. Pei, Y.Yang, G. Yu, C. Zang, and A. J. Heeger, “Polymer Light-Emitting Electrochemical Cells: In Situ Formation of Light-Emitting p-n Junction,”
Journal of the American Chemical Society
, 1996, 118, 3922-3929), vertically stacked organic light-emitting diodes capable of emitting light of multiple wavelengths (see U. S. Pat. No. 5,707,745, incorporated by reference, and Z. Shen, P. E. Burrows, V. Bulovic, S. R. Forrest, and M. E. Thompson, “Three-Color, Tunable, Organic Light-Emitting Devices,”
Science
, 1997, 276, 2009-2011).
SUMMARY OF INVENTION
The present invention relates to a method for adding a buffer layer comprising an intrinsically conducting polymer adjacent to an electrode layer in an organic electronic device such as an OLED to increase performance reliability. For example, the buffer layer may be between the anode layer and hole transporting layer. In particular it can improve the performance of OLEDs that rely upon vapor-coated indium tin oxide as an anode. Adding such a buffer layer to an organic electronic device can reduce or eliminate performance failures such as electrical shorts and non-radiative regions (dark spots).
Unexpectedly, the inventors found they were able to obtain a thin, uniform, smooth polymeric buffer layer by using web coating methods such as microgravure or meniscus coating. Because these coating methods can be used in a continuous process, they enable; adding a beneficial buffer layer to large area OLED substrates and continuous substrate sheets.
For applications requiring large area displays, it becomes more and more difficult to control the number of defects on a substrate or electrode layer. Because the buffer layer of the present invention can minimize the effects that these imperfections have on OLED performance, it enables the production of reliable large area OLEDs, (e g., those having an, area of 250 cm
2
or more, or at least one dimension greater than 25 cm).
One aspect of the present invention features an organic electronic device having a buffer layer, comprised of a doped conducting polymer, adjacent to an electrode layer. The conducting polymer may be externally doped or self doped. The electrode may be an anode comprised of indium tin oxide. The organic electronic device may have a flexible substrate, which may be comprised of materials such as, e.g. poly(ethylene terephthalate), polycarbonate, polyolefin, poly(methyl methacrylate), poly(styrene), polyester, polyolefin, pol

Affiliated with

Also associated with

Rating

Large area organic electronic devices having conducting... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Large area organic electronic devices having conducting..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Large area organic electronic devices having conducting... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3084201