|Title of Invention||
"AN ORGANIC LIGHT EMITTING DEVICE AND METHOD OF FABRICATING THEREOF"
|Abstract||An organic light emitting device that may have mixed organic layers is provided. A method of fabricating such an organic light emitting device is provided. A first organic material is solution deposited to form a patterned organic layer over a first electrode. A second organic materials is deposited, by means other than solution processing, On and in physical contact with the first organic layer to form a second organic layer. The second organic layer forms a blanket layer over the first organic layer. A second electrode is then deposited over the second organic layer.|
|Full Text||STRUCTURE AND METHOD OF FABRICATING ORGANIC DEVICES
 This application is related to concurrently filed Patent Application No.
10/295,802, attorney docket no. 10052 / 3301, and Patent Application No. 10/295,808, attorney docket no. 10052 / 3501, each of which is incorporated by reference in its entirety.
Field of the Invention
"[tJ002] •The'present Invention relates to organic liglit "emitting devices (OLEDs), and more
specifically to organic devices having mixed organic layers, and methods of fabricating such
 Opto-electronic devices that make use of organic materials are becoming
increasingly desirable for a number of reasons. Many of the materials used to make such devices are relatively inexpensive, so organic opto-electronic devices have the potential for cost advantages over inorganic devices. In addition, the inherent properties of organic materials, such as their flexibility, may make them well suited for particular applications such as fabrication on a flexible substrate. Examples of organic opto-electronic devices include organic light emitting devices (OLEDs), organic phototransistors, organic photovoltaic cells, and organic photodetectors. For OLEDs, the organic materials may have performance advantages over
conventional materials. For example, the wavelength at which an organic emissive layer emits light may generally be readily tuned with appropriate dopants.
 As used herein, the term "organic" includes polymeric materials as well as small
molecule organic materials that may be used to fabricate organic opto-electronic devices. "Small molecule" refers to any organic material that is not a polymer, and "small molecules" may actually be quite large. Small molecules may include repeat units in some circumstances. For example, using a long chain alkyl group as a substituent does not remove a molecule from the "small molecule" class. Small molecules may also be incorporated into polymers, for example as a pendent group on a polymer backbone or as a part of the backbone. Small molecules may also serve as the core moiety of a dendrimeT, which consists of a series of chemical shells built on the core moiety. The core moiety of a dendruner may be an fluorescent or phosphorescent small molecule emitter. A dendrimer may be a "small molecule," and it is believed that all dendrimers currently used in the field of OLBDs are small molecules.
 OLEDs make use of thin organic films that emit light when voltage is applied
across the device. OLEDs are becoming an increasingly interesting technology for use in applications such as flat panel displays, illumination, and backlighting. Several OLED materials and configurations are described in U.S. Patent Nos. 5,844,363, 6,303,238, and 5,707,745, which
. -OLED devices "are generally (but not always) intended to emit light through at
least one of the electrodes, and one or more transparent electrodes may be useful in an organic opto-electronic devices. For example, a transparent electrode material, such as indium tin oxide (TTO), maybe used as the bottom electrode. A transparent top electrode, such as disclosed in U.S. Patent Nos. 5,703,436 and 5,707,745, which are incorporated by reference in their entireties, may also be used. For a device intended to emit light only through the bottom electrode, the top electrode does not need to be transparent, and may be comprised of a thick and reflective metal layer having a high electrical conductivity. Similarly, for a device intended to emit light only through the top electrode, the bottom electrode may be opaque and / or reflective. Where an electrode does not need to be transparent, using a thicker layer may provide better conductivity, and using a reflective electrode may increase the amount of light emitted through the other electrode, by reflecting light back towards the transparent electrode. Fully transparent devices
may juso oe raoncaiea, wnere oota electrodes axe transparent. Side emitting OLEDs may also be
fabricated, and one or both electrodes may be opaque or reflective in such devices.
[0007J As used herein, "top" means furthest away from the substrate, while "bottom"
means closest to the substrate. For example, for a device having two electrodes, the bottom electrode is the electrode closest to the substrate, and is generally the first electrode fabricated. The bottom electrode has two surfaces, a bottom surface closest to the substrate, and a top surface further away from the substrate. Where a first layer is described as "disposed over" a second layer, the first layer is disposed further away from substrate. There may be other layers between the first and second layer,-unless it is specified that the first layer is "in physical contact with" the second layer. For example, a cathode may be described as "disposed over" an anode, even though there are various organic layers in between.
 One of the main goals of OLEDs is realization of patterned full color flat panel
displays in which the red, green and blue pixels are patterned deposited. Due to the difficulty of using masks for large area substrates using vapor phase deposition systems, for example substrates larger than about 0.5 meters in diameter, it is believed that patterning of the displays using ink jet printing of solution-processible materials may offer significant advantages. Ink jet printing techniques are believed to be particularly suitable for patterning the solution-processible polymers, that ate.xisedjn QLEDS.haAong-apolymahbascd oaissi.veJa.yer. However, the. selection of materials that maybe used'in such polymer-'Based systems is typically limited by the fact that the solution that is used as the carrier medium has to be selected so as avoid dissolution of the underlying layer. A common choice is to use a PEDOTJPSS layer to provide hole injection and hole transport functions. PJ3DOT:PSS is soluble in water, but insoluble in certain organic solvents used to process polymer based emissive layers. As a result, solution processing may be used to deposit polymer based layers on PEDOTrPSS without dissolving the PEDOT:PSS.
 High performance OLEDs, especially high performance electrophosphorescent
OLEDs, typically require the presence of several layers that each perform separate functions. This means that it is highly desirable to be free to select from a wide variety of materials for each layer. For example, for high performance electrophosphorescent OLEDs, it is typically desirable to have two hole transport layers between the anode layer and the emissive layer. The first hole
transport layer, which is in direct contact with the anode layer, is used primarily for its
plnanzing characteristics as well as for its more favorable hole injecting characteristics. This
layer may be referred to as a hole injecting layer (HEL). The second hole transport layer (HTL), which may be in direct contact witii the emissive layer is typically selected to have a high hole conductivity. This layer may also have the added function, at least in part, of blocking electrons and/or excitons.
 It would be desirable to have a device wherein a patterned emissive layer
deposited by patterning solution-processible materials is used in combination with an emissive layer deposited by other methods, so that the materials in the patterned emissive layer may be selected from a wide range of materials, independent of their solubility characteristics, while the emissive layer deposited by other methods may include materials not suitable for deposition via solution processing. Thus, a device capable of emitting a broad spectrum of light may be achieved.
Summary of the Invention
 An organic light emitting device that may have mixed organic layers is provided.
A method of fabricating such an organic light emitting device is provided. A first organic material is solution deposited to fonn-apattemed organic Jayecxxver a£rstjelediode.. A second organic material is deposited, by means other than solution processing, on and in physical contact with the first organic layer to form a second organic layer. The second organic layer forms a blanket layer over the first organic layer. A second electrode is then deposited over the second organic layer.
[00012J In particular, embodiments of the present invention are directed toward depositing a first organic layer comprising solution-processible emissive materials followed by depositing a second organic layer over the first organic layer by means other that solution processing in a full color organic light emitting display.
 More specifically, embodiments of the present invention are directed toward using
solution processing in conjunction with other deposition techniques in a roll color organic light
 An objective of embodiments of the present invention is to provide a method for
fabricating organic light emitting devices that have improved lifetimes. Such improved lifetimes may be uniquely achievable for electrophosphorescent devices, since the improved efficiencies of eleotrophosphorescent devices may permit a practically beneficial trade-off between efficiency and lifetime to be realized, a benefit mat is uniquely attributable to the very high efficiencies of phosphorescent materials.
BriefDescription of jhe Drawings
 Fig. 1 shows an organic light emitting device having separate electron transport,
hole transport, and emissive layers, as well as other layers.
 Fig. 2 shows an inverted organic light emitting device that does not have a
separate electron transport layer.
[00017) Fig. 3 shows an organic light emitting device having a first solution-deposited
organic layer in physical contact with a second organic layer.
 Generally, an OLED comprises at least one organic layer disposed between and
electrically -connected to an anode-and a-cathode,. When a-cunent.is-applied^ the anode injects
holes and the cathode injects electrons into the organic laycr(s). The injected holes and electrons
each migrate toward the oppositely charged electrode. When an electron and hole localize on the
same molecule, an "exciton," which is a localized electron-hole pair having an excited energy
state, is formed. Light is emitted when the exciton relaxes via a photoemissive mechanism. In
some cases, the exciton may be localized on an excimer or an exciplex. Non-radiative
mechanisms, such as thermal relaxation, may also occur, but are generally considered
 The initial OLEDs used emissive molecules that emitted light from their singlet
states ("fluorescence") as disclosed, for example, in U..S. Patent No. 4,769,292, which is
incorporated by reference in its entirety. Fluorescent emission generally occurs in a time frame
of less than 10 nanoseconds.
 More recently, OLEDs having emissive materials that emit light from triplet
states (""phosphorescence") have been demonstrated Baldo et al, "Highly Efficient Phosphorescent Emission from Organic Electroluminescent Devices," Nature, vol. 395,151-154, 1998; ("Baldo-O and Baldo et al., "Very high-efficiency green organic light-emitting devices based on electrophosphorescence," Appl. Phys. Lett., vol. 75, No. 3,4-6 (1999) ("Baldo-H"), which are incorporated by reference in their entireties. Phosphorescence may be referred to as a "forbidden" transition because the transition requires a change in spin states, and quantum mechanics indicates that such a transition is not favored. As a result, phosphorescence generally occurs in a time frame exceeding at least 10 nanoseconds, and typically greater than ] 00 nanoseconds. If the natural, radiative lifetime of phosphorescence is too long, triplets may decay by a non-radiative mechanism, such that no light is emitted. Organic phosphorescence is also often observed in molecules containing heteroatoms with unshared pairs of electrons at very low temperatures. 2,2'-bipyridine is such a molecule. Non-radiative decay mechanisms are typically temperature dependent, such that a material that exhibits phosphorescence at liquid nitrogen temperatures may not exhibit phosphorescence at room temperature. But, as demonstrated by Baldo, this problem may be addressed by selecting phosphorescent compounds that do phosphoresce at room temperature.
 Generally, the excitons in an OLED are believed to be created in a ratio of about
3^1, i«., appK>ximate^,75%.tciplets.and25.%J5Maglets. Sae, Adachi etat, lcMearly.lJ30.% Jatemal
Phosphorescent Efficiency Ki An Organic Light Emitting Device," J. Appl. Pnys., 90, 5048
(2001), which is incorporated by reference in its entirely. In many cases, singlet excitons may
readily transfer their energy to triplet excited states via "intersystem crossing," whereas triplet
excitons may not readily transfer their energy to singlet excited states. As a result, 100% internal
quantum efficiency is theoretically possible with phosphorescent OLEDs. In a fluorescent
device, the energy of triplet excitons is generally lost to radiationless decay processes that
heat-up the device, resulting in much lower internal quantum efficiencies. OLEDs utilizing
phosphorescent materials that emit from triplet excited states are disclosed, for example, in U.S.
Patent No. 6,303,238, which is incorporated by reference in its entirety.
 Phosphorescence may be preceded by a transition from a triplet excited state to an
intermediate non-triplet state from which the emissive decay occurs. For example, organic molecules coordinated to lanthanide elements often phosphoresce from excited states localized
on the lanthanide metal. However, such materials do not phosphoresce directly from a triplet
Incited state but instead emit from an atomic excited state centered on the lanthanide metal ion.
The europium diketonate complexes illustrate one group of these types of species.
(00023) Phosphorescence from triplets can be enhanced over fluorescence by confining,
preferably through bonding, the organic molecule in close proximity to an atom of high atomic number. This phenomenon, called the heavy atom effect, is created by a mechanism known as spin-orbit coupling. Such a phosphorescent transition may be observed from an excited metal-to-ligand charge transfer (MLCT) state of an organometallic molecule such as tris(2-phenylpyridine)iridium(m).
 Fig. 1 shows an organic light emitting device 100. The figures are not necessarily
drawn to scaje. .Device 1QQ may inclu.de a gub.stra.te 1JQ, an, anode 115V a hole injection Uver 120, a hole transport layer 125, an electron blocking layer 130, an emissive layer 135, a hole blocking layer 140, an electron transport layer 145, an electron injection layer 150, a protective layer 155, and a cathode 160. Cathode 160 is a compound cathode having a first conductive layer 162 and a second conductive layer 164. Device 100 may be fabricated by depositing the layers described, in order.
(00025] Substrate 110 may be any suitable substrate that provides desired structural
properties, Substpate-llO-may be flexible OF rigid, Sub^^tell-0-may-b
metal foils are examples of preferred flexible substrate materials. Substrate 110 may be a
semiconductor material in order to facilitate the fabrication of circuitry. For example, substrate
110 maybe a silicon wafer upon which circuits are fabricated, capable of controlling OLEDs
subsequently deposited on the substrate. Other substrates may be used. The material and
thickness of substrate 110 maybe chosen to obtain desired structural and optical properties.
(00026] Anode 115 may be any suitable anode that is sufficiently conductive to transport
holes to the organic layers. The material of anode 115 preferably has a work function higher than about 4 eV (a "high work function material"). Preferred anode materials include conductive metal oxides, such as indium tin oxide (ITO) and indium zinc oxide (IZO), aluminum zinc oxide (AlZnO), and metals. Anode 115 (and substrate 110) may be sufficiently transparent to create a bottom-emitting device. A preferred transparent substrate and anode combination is
commercially available ITO (anode) deposited on glass or plastic (substrate). A flexible and transparent substrate-anode combination is disclosed in United States Patent No. 5,844,363, which is incorporated by reference in its entirety. Anode 115 may be opaque and / or reflective. A reflective anode 115 may be preferred for some top-emitting devices, to increase the amount of light emitted from the top of the device. The material and thickness of anode 115 may be chosen to obtain desired conductive and optical properties. Where anode 115 is transparent, there may be a range of thickness for a particular material that is thick enough to provide the desired conductivity, yet thin enough to provide the desired degree of transparency. Other anode materials and structures may be used.
 Hole transport layer 125 may include a material capable of transporting holes.
Hole..transport layer 130 may be intrinsic (undoped), pr dPp.ed- poping may b? used to enhance
conductivity. o-NPD and TPD are examples of intrinsic hole transport layers. An example of a
p-dopedhole transport layer is m-MTDATA doped with F-f-TCNQ at a molar ratio of 50:1, as
disclosed in United States Patent Application No. 10/173,682 to Forrest et al, which is
incorporated by reference in its entirety. Other hole transport layers may be used.
 Emissive layer 135 may include an organic material capable of emitting light
when a current is passed between anode 115 and cathode 160. Preferably, emissive layer 135 eofitaks-a-phosphorescent eiBissw&.material, although-fluorescent eBussiv-e-materiais-iway also be used. Phosphorescent materials are preferred because of the higher luminescent efficiencies associated with such materials. Emissive layer 135 may also comprise a host material capable of transporting electrons and / or holes, doped with an emissive material that may trap electrons, holes, and / or excitons, such that excitons relax from the emissive material via a photoemissive mechanism. Emissive layer 135 may comprise a single material that combines transport and emissive properties. Whether the emissive material is a dopant or a major constituent, emissive layer 135 may comprise other materials, such as dopants that tune the emission of the emissive material. Emissive layer 135 may include a plurality of emissive materials capable of, in combination, emitting a desired spectrum of light. Examples of phosphorescent emissive materials include Ir(ppy)3. Examples of fluorescent emissive materials include DCM and DMQA. Examples of host materials include Alqj, CBP and mCP. Examples of emissive and host materials are disclosed in U.S. Patent No. 6,303,238 to Thompson et al., which is
incorporated by reference in its entirety. Emissive material may be included in emissive layer
135 in a number of ways. For example, an emissive small molecule may be incorporated into a
solymer. Other emissive layer materials and structures may be used.
 Electron transport layer 140 may include a material capable of transporting
electrons. Electron transport layer 140 may be intrinsic (undoped), or doped. Doping may be
used to enhance conductivity. Alqj is an example of an intrinsic electron transport layer. An
example of an n-doped electron transport layer is BPhen doped with Li at a molar ratio of 1:1, as
disclosed in United States Patent Application No. 10/173,682 to Forrest et al, which is
incorporated by reference in its entirety. Other electron transport layers may be used.
 The charge carrying component of the electron transport layer may be selected
such that electrons can be efficiently «a$Qts4 ftora the ca.tho.4e into the LUMO (Lowes i Unoccupied Molecular Orbital) level of the electron transport layer. The "charge carrying component" is the material responsible for the LUMO that actually transports electrons. This component may be the base material, or it may be a dopant, The LUMO level of an organic material may be generally characterized by the electron affinity of that material and the rektive electron injection efficiently of a cathode may be generally characterized in terms of the work function of the cathode material. This means that the preferred properties of an electron transport layer and-tiie-adjaeent-catijode-may-be^paeified m-tennas of'the electron -af&Bity-of-the char-go carrying component of the ETL and the work function of the cathode material. In particular, so as to achieve high electron injection efficiency, the work function of the cathode material is preferably not greater than the electron affinity of the charge carrying component of the electron transport layer by more than about 0.75 eV, more preferably, by not more than about 0.5 eV. Most preferably, the electron affinity of the charge carrying component of the electron transport layer is greater than the work function of the cathode material. Similar considerations apply to any layer into which electrons are being injected.
[00031 ] Cathode 160 may be any suitable material or combination of materials known to
the art, such that cathode 160 is capable of conducting electrons and injecting them into the organic layers of device 100. Cathode 160 may be transparent or opaque, and may be reflective. Metals and metal oxides are examples of suitable cathode materials. Cathode 160 maybe a single layer, or may have a compound structure. Figure 1 shows a compound cathode 160 having
a thin metal layer 162 and a thicker conductive metal oxide layer 164. In a compound cathode,
preferred materials for the thicker layer 164 include HO, IZO, and other materials known to the
art. U.S. Patent Nos. 5,703,436 and 5,707,745, which are incorporated by reference in their
entireties, disclose examples of cathodes including compound cathodes having a thin layer of
metal such as Mg:Ag with an overlying transparent, electrically-conductive, sputter-deposited
ITO layer. The part of cathode 160 that is in contact with the underlying organic layer, whether it
is a single layer cathode 160, the thin metal layer 162 of a compound cathode, or some other part,
is preferably made of a material having a work function lower than about 4 eV (a "low work
function material"). Other cathode materials and structures may be used.
(00032J Blocking layers may be used to reduce the number of charge carriers (electrons or
hojes) and / or excjtQns thai' leave the emjspive layer. As electsn blocking layer 130 may be disposed between emissive layer 135 and the hole transport layer 125, to block electrons from leaving emissive layer 135 in the direction of hole transport layer 125. Similarly, a hole blocking layer 140 may be disposed between emissive Iayerl35 and electron transport layer 145, to block holes from leaving emissive layer 135 in the direction of electron transport layer 140. Blocking layers may also be used to block excitons from diffusing out of the emissive layer. The theory and use of blocking layers is described in more detail in United States Patent No. 6,097,147 and United States-Patent Application Nc% lO/4-73^$S2.to ^onest^t-al-r^vhiGh.- ate-mcojporated-by reference in their entireties.
 Generally, injection layers are comprised of a material that may improve the
injection of charge carriers from one layer, such as an electrode or an organic layer, into an adjacent organic layer. Injection layers may also perform a charge transport function. In device 100, hole injection layer 120 may be any layer that improves the injection of holes from anode 115 into hole transport layer 125. CuPc is an example of a material that may be used as a hole injection layer from an ITO anode 115, and other anodes. In device 100, electron injection layer 150 maybe any layer that improves the injection of electrons into electron transport layer 145. LiF / Al is an example of a material that may be used as an electron injection layer into an electron transport layer from an adjacent layer. Other materials or combinations of materials may be used for injection layers. Depending upon the configuration of a particular device, injection layers maybe disposed at locations different than those shown in device 100. More examples of
injection layers are provided in U.S. Patent Application Serial No. 09/931,948 to Lu et al., which is incorporated by reference in its entirety. A hole injection layer may comprise a solution deposited matelial, such as a spin-coated polymer, e.g., PEDOTrPSS, or it may be a vapor deposited small molecule material, e.g.> CuPc or MTDATA.
 A hole injection layer (HIL) may planarize or wet the anode surface so as to
provide efficient hole injection from the anode into the hole injecting material. A hole injection layer may also have a charge carrying component having HOMO (Highest Occupied Molecular Orbital) energy levels that favorably match up, as defined by their herein-described relative ionization potential (IP) energies, with the adjacent anode layer on one side of the HIL and the hole transporting layer on the opposite side of the HEL The "charge carrying component" is the majcjtiaj responsible for the JJQMO that actuary tr&n§pprts hple$. This- component may be the base material of the HIL, or it may be a dopant. Using a doped HIL allows the dopant to be selected for its electrical properties, and the host to be selected for morpological properties such as wetting, flexibility, toughness, etc. Preferred properties for the HIL material are such that holes can be efficiently injected from the anode into the HJL material. In particular, the charge carrying component of the HIL preferably has an P not more than about 0.7 eV greater that the IP of the anode material. More preferably, the charge carrying component has an IP not more thaaAbout 0.5-cV .gceater-than ^he-anode-materiaL Similar-considerations apply-to-any-Jayer-Hito which holes are being injected, HIL materials are further distinguished from conventional hole transporting materials that are typically used in the hole transporting layer of an OLED in that such HEL materials may have a hole conductivity that is substantially less than the hole conductivity of conventional hole transporting materials. The thickness of the HIL of the present invention may be thick enough to help planarize or wet the surface of the anode layer. For example, an HEL thickness of as little as 10 nm may be acceptable for a very smooth anode surface. However, since anode surfaces tend to be very rough, a thickness for the HIL of up to 50 nm may be desired in some cases.
 A protective layer may be used to protect underlying layers during subsequent
fabrication processes. For example, the processes used to fabricate metal or metal oxide top electrodes may damage organic layers, and a protective layer maybe used to reduce or eliminate such damage. In device 100, protective layer 155 may reduce damage to underlying organic
layers during the fabrication of cathode 160. Preferably, a protective layer has a high carrier
mobility for the type of carrier that it transports (electrons in device 100), such that it does not
significantly increase the operating voltage of device 100. CuPc, BCP, and various metal
phthalocyanines are examples of materials that may be used in protective layers. Other materials
or combinations of materials maybe used. The thickness of protective layer 155 is preferably
thick enough that there is little or no damage to underlying layers due to fabrication processes
that occur after organic protective layer 160 is deposited, yet not so thick as to significantly
increase the operating voltage of device 100. Protective layer 155 may be doped to increase its
conductivity. For example, a CuPc or BCP protective layer 160 may be doped with Li. A more
detailed description of protective layers maybe found in U.S. Patent Application Serial No.
09/93.1,948 to Lu et al., which is mcfflqpor#tcd by reference in its entirety.
 Figure 2 shows an inverted OLED 200. The device includes a substrate 210, an
cathode 215, an emissive layer 220, a hole transport layer 225, and an anode 230. Device 200 may be fabricated by depositing the layers described, in order. Because the most common OLED configuration has a cathode disposed over the anode, and device 200 has cathode 215 disposed under anode 230, device 200 maybe referred to as an "inverted" OLED. Materials similar to those described with respect to device 100 maybe used in the corresponding layers of device 200, -figu£&-2-provides one ^ample^f.hawsomeJayere-mayJje-omtted^ device 100.
 The simple layered structure illustrated in Figures 1 and 2 is provided by way of
non-limiting example, and it is understood that embodiments of the invention may be used in connection with a wide variety of other structures. The specific materials and structures described are exemplary in nature, and other materials and structures may be used. Functional OLEDs may be achieved by combining the various layers described in different ways, or layers may be omitted entirely, based on design, performance, and cost factors. Other layers not specifically described may also be included. Materials other than those specifically described may be used. Although many of the examples provided herein describe various layers as comprising a single material, it is understood that combinations of materials, such as a mixture of host and dopant, or more generally a mixture, may be used. Also, the layers may have various sublayers. The names given to the various layers herein are not intended to be strictly limiting.
For example, in device 200, hole transport layer 225 transports holes and injects holes into ^missive layer 220, and may be described as a hole transport layer .or a hole injection layer. In one embodiment, an OLED may be described as having an "organic layer" disposed between a cathode and an anode. This organic layer may comprise a single layer, or may farther comprise multiple layers of different organic materials as described, for example, with respect to Figures 1 and 2.
 Structures and materials not specifically described may also be used, such as
OLEDs comprised of polymeric materials (PLEDs) such as disclosed in U.S. Pat. No. 5,247,190, Friend et al., which is incorporated by reference in its mtircty. By way of further example, OLEDs having a single organic layer may be used. OLEDs may be stacked, for example as described in U,S. Pajent NO. 5,707,745 to Forrest et aj, which is incorporated b.y reference in its entirety. The OLED structure may deviate from the simple layered structure illustrated in Figures 1 and 2. For example, the substrate may include an angled reflective surface to improve out-coupling, such as amesa structure as described in U.S. Patent No. 6,091,195 to Forrest et al., and / or a pit structure as described in U.S. Patent No. 5,834,893 to Bulovic et al., which are incorporated by reference in their entireties.
 Unless otherwise specified, any of the layers of the various embodiments may be
-deposit«d-by anysuitable-method. Jfor the-€>rganic4ayerSrpr-efeEr«dmetiaeds include.thermal-evaporation, ink-jet, such as described in U.S. Patent Nos. 6,013,982 and 6,087,196, which are incorporated by reference in their entireties, organic vapor phase deposition (OVPD), such as described in U.S. Patent No. 6,337,102 to Forrest et al., which is incorporated by reference in its entirety, and deposition by organic vapor jet printing (OVJP), such as described in U.S. Patent Application No. 10/233,470, which is incorporated by reference in its entirety. Other suitable deposition methods include spin coating and other solution based processes. Solution based processes are preferably carried out rn nitrogen or an inert atmosphere. For the other layers, preferred methods include thermal evaporation. Preferred patterning methods include deposition through a mask, cold welding such as described in US, Patent Nos. 6,294,398 and 6,468,819, which are incorporated by reference in their entireties, and patterning associated with some of the deposition methods such as ink-jet and OVID. Other methods may also be used. The materials to be deposited maybe modified to make them compatible with a particular deposition method.
For example, substiruents such as alkyi and aryl groups, branched or unbranched, and preferably 'containing at least 3 carbons, may be used in small molecules to enhance their ability to undergo solution processing. Substituents having 20 carbons or more may be used, and 3-20 carbons is a preferred range. Materials with asymmetric structures may have better solution processibiliry than those having symmetric structures, because asymmetric materials may have a lower tendency to recrystallize. Dendrimer substituents may be used to enhance the ability of small molecules to undergo solution processing.
 Devices fabricated in accordance with embodiments of the invention may be
incorporated into a wide variety of consumer products, including flat panel displays, computer
monitors, televisions, billboards, lights for interior or exterior illumination and / or signaling,
hea^up.di^Lays^fu]^ .flexible displays, laser printers, telephones., cell
phones, personal digital assistants (PDAs), laptop computers, digital cameras, camcorders, viewfinders, micro-displays, vehicles, a large area wall, theater or stadium screen, or a sign. Various control mechanisms maybe used to control devices fabricated in accordance with the present invention, including passive matrix and active matrix. Many of the devices are intended for use in a temperature range comfortable to humans, such as 18 degrees C to 30 degrees C, and more preferably at room temperature (20 - 25 degrees Q.
.- — J3jo-matecial&-aad stouctures-xiescribed herein-maybave applications in devices
other than OLEDs. For example, other optoelectronic devices such as organic solar cells and
organic photodetectors may employ the materials and structures. More generally, organic
devices, such as organic transistors, may employ the materials and structures.
 Figure 3 shows an embodiment of the invention where a patterned emissive layer
is solution deposited over and in physical contact with a hole transport layer. Device 300 is
fabricated over a substrate 310. Substrate 310 is coated with an anode 320. The substrate and
the anode layer may be selected from any suitable materials. A hole transport layer 330 and a
layer 340 of an undoped emissive host material, are then deposited, in that order, over anode 320.
 A patterned emissive layer that further comprises emissive regions 351 and 352 is
then deposited by solution processing over and in physical contact with layer 340. A farther emissive layer 360 is then deposited, by means other than solution processing, so as to form a blanket layer over and in contact with the patterned emissive layer which comprises emissive
and 352. Emissive layer 360 includes an active region 353 disposed under cathode 383 that, when the device is operated, will be the region of layer 360 that emits light. Any suitable material may be used for emissive layer 360. For example, emissive layer 360 may be deposited by means such as thermal vapor phase deposition. A full color display may be fabricated by depositing regions 351,352 and 360 that include red, green, and blue emissive materials, respectively.
(00044] By solution depositing some emissive regions, such as regions 351 and 352,
followed by the blanket deposition by another technique of another emissive layer, such as layer 360, many of the advantages of solution processing and the second technique are obtained. For example, ink-jet printing maybe used to deposit regions 351 and 352, thereby achieving a good patterning resolution at with a relatively inexpensive technique. Layer 360 may then be blanket deposited by a non-solution based technique, such as thermal vapor deposition or organic vapor phase deposition. Any disadvantages associated with solution based techniques are thereby avoided for layer 360. But, the inexpensive patterning associated with some solution based processes may be retained. Layer 360 is effectively patterned even though it was blanket deposited, by selecting materials such that layer 360 emits only where regions 351 and 352 are not present. Thus, layer 360 may be deposited without the use of a shadow mask or other patterning technique associated with non-solution based processes.
 In many devices, it may be advantageous to vapor process at least one emissive
material. In particular, it is believed that phosphorescent emissive materials, blue emitting materials, and especially blue emitting phosphorescent materials, may be particularly susceptible to any impurities introduced as a result of solution processing, because of the wide band gap of blue emitting materials and / or the long lifetime of excitons in phosphorescent materials. In one embodiment, red and green emitting phosphorescent materials may be deposited into patterned regions via solution processing, followed by the blanket deposition of a blue phosphorescent material via a non-solution based process. In another embodiment, red and green emitting fluorescent materials may be deposited into patterned regions via solution processing, followed by the blanket deposition of a blue fluorescent material via a non-solution based process. In another embodiment, fluorescent emissive materials may be deposited via solution based processing, followed by the blanket deposition of a phosphorescent material via a non-solution
process. By using a technique other than solution processing to deposit emissive layer 360, the disadvantages of solution processing may be avoided for layer 360. Other embodiments not specifically described may also be implemented.
 An electron transport layer 370 is then deposited over emissive layer 360, and cathodes 381,382 and 383 deposited over electron transport layer 370. Any suitable material and deposition technique maybe used for substrate 310, anode 320, hole transport layer 330, electron transport layer 370, and cathode 380. In one embodiment, all organic layers except regions 351 and 352 are deposited by a non-solution based process, such as vapor deposition. In another, embodiment, multiple layers may be solution deposited.
 In the embodiment of Figure 3, it may be desirable to select a host material for
layers 340 and 351,352 and 360 that has a hole mobility that is significantly higher than the
electron mobility. In such a material, most recombination and exciton formation would occur
near the top of layers 340 and regions 351,352 and 360, where the emissive dopant is most likely
to be concentrated. In addition, it may be desirable to use emissive dopants that trap charge
carriers and / or excitons, such that carriers and excitons may not escape into other layers, or
parts of layer 340 and regions 351,352 and 360 that do not contain adequate emissive dopant.
 The method described in the embodiment of Figure 3 is not limited to the specific
layers discussed with respect to Figure 3. For example, layers not specifically described may be
included, layers described maybe omitted, and the order of layers may be modified.
(00049} The solution processing methods described herein may be used multiple times in
a single device, and they may be combined. For example, a hole injection layer and hole transport layer may be fabricated, followed by the solution deposition of a patterned emissive layer and subsequent thermal vapor phase deposition of a further emissive layer, as described with respect to Figure 3.
[00050J As used herein, "solution processible" means capable of being dissolved,
dispersed, or transported in and/or deposited from a liquid medium, either in solution or suspension form.
(00051] It is understood that the various embodiments described herein are by way of
example only, and are not intended to limit the scope of the invention. For example, many of the materials and structures described herein may be substituted with other materials and structures
without deviating trom the spirit of toe invention. It is understood mat vanous theories as to why tine invention works are not intended to be limiting. For example, theories relating to charge transfer are not intended to be limiting.
(00052) As used herein, abbreviations refer to materials as follows:
Alq3: 8-tris-hydroxyquinoline aluminum
n-BPhen; n-doped BPhen (doped with lithium)
p-MTDATA: p-doped m-MTDATA (doped with F4-TCNQ)
ldppz)3'. tris( 1 -phcoylpyraitoloto}N,C(2')iridium(ni)
TAZ: 3-phenyl-4-(r-naphthyl)-5-phenyl-l ,2,4-triazole
CuPc: copper phttialocyanine.
ITO: indium tin oxide
PEDOT:PSS : an aqueous dispersion of poly(3,4-ethylenedioxythiophene) with
 While the present invention is described with respect to particular examples and
preferred embodiments, it is understood that the present invention is not limited to these examples and embodiments. The present invention as claimed therefore includes variations from the particular example, and preferred embodiments described herein, as will be apparent to one of skill in the art.
WHAT IS CLAIMED IS:
1. An organic light emitting device, comprising:
a bottom electrode;
a patterned first organic layer disposed over the bottom electrode, comprising a first region capable of emitting a first spectrum of light;
a second organic layer disposed over and in physical contact with the first organic layer, the second organic layer being disposed over the bottom electrode, the second organic layer being capable of emitting a second spectrum of light; and
a top electrode disposed over the second organic layer,
2. The device of claim 1, wherein the patterned first organic layer further comprises a
second regions, wherein the second region is capable of emitting a third spectrum of light.
3. The device of claim 2, wherein each of said first, second and third spectra of light are
4. The device of claim 2, wherein the first spectrum of light is red
5. The device of claim 2, wherein the second spectrum of light is blue.
6. The device of claim 2, wherein the third spectrum of light is green.
7. The device of claim 1, wherein the first organic layer is deposited by solution processing.
8. The device of claim 7, wherein the solution processing is by ink jet,
9. The device of claim 1 > wherein the second organic layer is deposited by thermal vapor
10. The device of claim 1 > wherein the top electrode includes indium tin oxide.
11. The device of claim 1, wherein the top and bottom electrodes are electrically connected to
the organic layers.
12. The device of claim 1, wherein the first organic layer is a hole transport layer and the
second organic layer is an emissive layer.
13. The device of claim 1, wherein the second organic layer is an emissive layer comprising a
neat layer of emissive material.
14. The device of claim 1, further comprising a third organic layer disposed between the
bottom electrode and the first organic layer.
15. The device of claim 14, wherein the third organic layer is a hole transport layer, and the
first organic layer is an emissive layer.
16. The device o'f claim 14, wherein the third organic layer is a hole injection layer, and the
first organic layer is an emissive layer.
17. The device of claim 14, wherein the third organic layer is an electron blocking layer, and
the first organic layer is an emissive layer.
18. The device of claim 14, further comprising a fourth organic layer disposed between the
bottom electrode and the third organic layer.
19. The device of claim 18, wherein the fourth organic layer is a hole transport layer, and the
third organic layer is an electron blocking layer.
20. A method of fabricating an organic light emitting device, comprising:
depositing a bottom electrode over a substrate;
depositing a patterned first organic layer over the bottom electrode, the first region being capable of emitting a first spectrum of light;
depositing a second organic layer over and in physical contact with the first organic layer, the second organic layer being disposed over the bottom electrode, the second organic layer being capable of emitting a second spectrum of light; and
depositing a top electrode over the second organic layer.
21. A method of fabricating an organic light emitting device, comprising:
depositing a bottom electrode over a substrate;
depositing a patterned first organic layer over the bottom blectrode, wherein the first region comprises two regions, a first region capable of emitting a first spectrum of light, and a second region capable of emitting a third spectrum of light;
depositing a second organic layer over the first organic layer and the bottom electrode, the second organic Jay.er being.capable of emittingjs. sec.ond.spictami.of light; and
depositing a top electrode over the second organic layer.
|Indian Patent Application Number||1594/DELNP/2005|
|PG Journal Number||12/2008|
|Date of Filing||19-Apr-2005|
|Name of Patentee||UNIVERSAL DISPLAY CORPORATION|
|Applicant Address||375 PHILLIPS BOULEVARD, EWING, NEW JERSEY 08618, U.S.A.|
|PCT International Classification Number||H01L 51/20|
|PCT International Application Number||PCT/US2003/036170|
|PCT International Filing date||2003-11-12|