BRPI0809502A2 - ORGANIC LED (OLED) WITH IMPROVED EXTERNAL COUPLING - Google Patents

Description

ORGANIC LED (OLED) WITH IMPROVED DETACHMENT

This application is related to US Application No. 11 / 729,877, filed March 30, 2007, entitled Enhanced Light Decoupling OLED and US Application No. 12 / 059,783, filed March 31, 2008, Low Index Grids (LIGs) to increase Top or Transparent OLED Decoupled Light.

Government Rights This invention was developed with support from the United States Government under contract No. DE-FG02-04ER84113 granted by the Department of Energy. The government has certain rights in the invention.

Common Research Contracts The claimed invention was developed by, on behalf of and / or related to one or more of the following parties to a joint university research agreement: Princeton University, University of Southern California, University of Michigan and Universal Display Corporation. The contract entered into force before and on the date of development of the claimed invention, and the invention was developed as a result of activities undertaken within the scope of the contract.

Field of the Invention The present invention relates to light-emitting organic devices (OLEDs) and more specifically light-emitting organic devices with low refractive index material optimizing light decoupling.

Background of the Invention Optoelectronic devices that make use of organic materials are becoming increasingly desired for various reasons. Many of the materials used to create such devices are relatively inexpensive, so optoelectronic devices have considerable cost advantages over inorganic devices. In addition, the inherent properties of organic materials, such as their flexibility, can make them well suited for specific applications such as manufacturing on a flexible substrate. Examples of organic optoelectronic devices include organic light-emitting devices (OLEDs), organic phototransistors, organic photovoltaic cells, and organic photodetectors. For OLEDs, organic materials may have performance advantages over conventional materials. For example, the wavelength at which an organic emissive layer emits light can usually be easily adjusted with appropriate dopants.

As used herein, the term "organic" includes

polymeric materials as well as small molecule organic materials that can be used to make optoelectronic devices. "Small molecule" refers to any organic material other than a polymer and "small molecules" may actually be relatively large. Small molecules may include repeated units in some circumstances. For example, the use of a long chain alkyl group as a substituent does not exclude a molecule of the "small molecule" class. Small molecules may also be incorporated into polymers, for example, as a pendant group on a polymer backbone or as part of the backbone. Small molecules can also serve as half the core of a dendrimer, which consists of a series of 30 chemical capsules embedded in the half of the nucleus. Half of the nucleus of a dendrimer can be a small fluorescent or phosphorescent emitter. A dendrimer may be a "small molecule" and it is believed that all dendrimers currently used in the field of OLEDs are small molecules. In general, a small molecule has a well-defined chemical formula with a single molecular weight, while a polymer has a chemical formula and a molecular weight that may vary from 5 molecule to molecule. As used herein, the term "organic" includes hydrocarbyl metal complexes and heteroatom-substituted hydrocarbyl linkers.

OLEDs make use of thin organic films that emit light when voltage is applied to the device. The 10 OLEDs are increasingly becoming an interesting technology for use in applications such as flat panel displays, backlighting and backlighting. Various OLED materials and configurations are described in US Pat. No. 5,844,363, 6,303,238 and 5,707,745, all incorporated herein by reference.

OLED devices generally (but not always) emit light through at least one electrode and one or more electrodes, and one or more transparent electrodes may be useful in optoelectronic devices. For example, a transparent electrode material such as indium tin oxide (ITO) may be used as the base electrode. A transparent upper electrode as disclosed in U.S. Patent Nos. 5,703,436 and 5,707,745, incorporated herein by reference in their entirety, may also be used. For a device that should emit light only through the lower electrode, the upper electrode need not be transparent and may consist of a reflective metal layer with high electrical conductivity. Similarly, for a device to only emit light through the upper electrode, the lower electrode may be opaque and reflective. Where an electrode does not need to be transparent, the use of a thicker layer may provide better conductivity and the use of a reflective electrode may increase the amount of light emitted through other electrodes, reflecting light back to the transparent electrode. Fully transparent devices can also be fabricated, where the two electrodes are transparent. Side-emitting OLEDs may also be fabricated, and one or both electrodes may be opaque or reflective on such devices.

As used herein, "upper" means farther from the substrate, while "lower" means closer to the substrate. For example, for a device 10 to have two electrodes, the lower electrode is the electrode closest to the substrate and is usually the first electrode manufactured. The lower electrode has two surfaces, a lower surface closer to the substrate and an upper surface further away from the substrate. Where a first layer is described as "disposed on" a second layer, the first layer is arranged distal to the substrate. There may be other layers between the first and second layers, unless it is specified that the first layer is "in physical contact with" the second layer. For example, a cathode may be described as "arranged on" an anode, although there are several organic layers in the middle.

As used herein, "processable solution" means capable of being dissolved, dispersed or transported in and / or deposited in a liquid medium, in solution or suspension form.

As used herein, and as generally understood by one of ordinary skill in the art, a first H0M0 ("Highest Occupied Molecular Orbital") or LUMO 30 ("Lowest Unoccupied Orbital Molecular") energy level will be "greater than" or "higher than "a second HOMO or LUMO power level if the first power level is closer to the vacuum power level. Since ionization potentials (IP) are measured as relative negative energy for a vacuum level, a higher HOMO energy level corresponds to an IP with a lower absolute value (an IP that is less negative). Similarly, a higher LUMO energy level corresponds to an electron 5 (AE) affinity with a lower absolute value (a less negative AE). In a conventional energy level diagram with a vacuum level at the top, the LUMO energy level of a material is higher than the HOMO energy level of the same material. A "higher" HOMO or LUMO 10 power level appears closer to the top of this diagram than the "lower" H0M0 or LUMO power level.

SUMMARY OF THE INVENTION An OLED may include regions of a material with a lower refractive index than the substrate or organic emissive material, allowing light emitted in a waveguide mode to be extracted into the air. These regions can be placed adjacent to the emissive regions of an OLED in a direction parallel to the electrodes. ' The substrate may also be given a non-standard shape to improve the conversion of waveguide mode and / or light from glass mode to air mode. The decoupling efficiency of this device can be up to three times the efficiency of a standard OLED.

An OLED can be manufactured by depositing a first

electrode on a substrate; depositing a grid of a low index material having a refractive index of 1.0 to 1.5 on the first electrode; depositing an organic emissive material on the grid so that the organic emissive material is in direct contact with the grid or the first electrode; and depositing a second electrode on the organic emissive material.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows an organic light emitting device with separate electron transport, hole transport and emission layers, as well as other layers.

Figure 2 shows the inverted light emitting organic device that does not have a separate electron transport layer.

Figure 3 shows a light-emitting organic device with regions of a transparent material with a low refractive index.

Figure 3B shows a part of a device where

The boundary between adjacent regions is almost perpendicular.

Figure 3C shows a part of a device where the boundary between adjacent regions is approximate.

Figure 3 shows a light emitting organic device with regions of a transparent material with a low refractive index.

Figures 4A and 4B show top views of example configurations of a low index region.

Figure 5A shows simulated values for the amount of light converted to air mode and glass mode for a device with a low index region.

Figure 5B shows simulated emission for a device with a hexagonal grid of a low index material with a refractive index of 1.03.

Figure 6A shows a device ''. · With a blade of

microlens.

Figure 6B shows a device with a thin low index layer disposed between the substrate and an electrode.

Figure 7 shows the proportion of light emitted by a microlens device having a hexagonal grid of low index material for a range of refractive indices.

Figure 8 shows the proportion of light emitted by a conventional OLED, an ideal microlens OLED and an ideal microlens OLED, and a hexagonal grid of low index material with a refractive index of 1.29.

Figure 9 shows the light emitted by a conventional OLED and an OLED with a hexagonal grid of a low index material having a refractive index of 1.2 and an inserted Teflon AF layer having a refractive index of 1.29.

Figure 10 shows the emission of a device having the same structure as figure 9, but with the low index material having a refractive index of 1.29.

Figure 11 shows the angular distribution of light on a glass substrate without a lower index layer.

Figure 12 shows the angular distribution of light on a glass substrate with a lower index layer.

Figure 13 shows the proportion of light emitted as a function of the emission angle for various device structures.

Figure 14 shows the proportion of light in air mode and glass mode in devices "with various electrode thicknesses.

Figure 15 shows the proportion of light in various modes for device having low variable width index regions.

Figure 16 shows the proportion of light in various modes.

for a device with organic regions from 4 μιη to 10 μπ \.

Figure 17 shows the proportion of light in various modes for device having low index regions with varying indexes and refractive geometries.

Figure 18 shows an organic device emitting

transparent or superior multi-region emission light of a transparent material with a low refractive index. Figures 19A-19C show a transparent or higher emission OLED with an LIG embedded in the organic layer.

Figures 20A-20C show simulated values for improved decoupling efficiency of a transparent or higher emission OLED with a rectangular LIG.

Figure 21 shows a transparent or higher emission OLED having a microlens slide.

Detailed Description In general, an OLED consists of at least one layer.

organically disposed between and electrically connected to an anode and a cathode. When a current is applied, the anode injects holes, and the cathode injects electrons into the organic layer (s). The injected holes and electrons 15 migrate in the opposite direction to the charged electrode. When an electron and a hole are located in the same molecule, an "exciton" is formed, which is a localized electron-hole pair that contains an excited energy state. Light is emitted when the exiton relaxes by means of a photo-emitting mechanism. In some cases, the exiton may be located in an excimer or an exciplex. Non-radiative mechanisms such as relaxation. may also occur, but are generally considered undesirable.

Figure 1 shows an organic light emitting device 100. The figures are not necessarily drawn to scale. Device 100 may include a substrate 110, anode 115, a hole injection layer 120, a hole carrier layer 125, an electron blocking layer 130, an emitter layer 135, a hole blocking layer 140, an electron carrier layer 145, an electron injection layer 150, a protective layer 155, and a cathode 160. Cathode 160 is a composite cathode having a first conductive layer 162 and a second conductive layer 164. Device 100 may be manufactured by depositing the described layers in order.

Substrate 110 may be any suitable substrate that provides desired structural properties. The substrate 110 may be flexible or rigid. The substrate 110 may be transparent, translucent or opaque. Plastic and glass are examples of preferred rigid substrate materials. Plastic and metal blades are examples of flexible rigid substrate materials, substrate 110 may be a semiconductor material to facilitate circuit fabrication. For example, substrate 110 may be a silicon wafer on which circuits are fabricated, capable of controlling OLEDs subsequently deposited on the substrate. Other substrates may be used. The material and substrate thickness 110 may be chosen to obtain desired structural and optical properties.

Anode 115 may be any suitable anode sufficiently conductive to carry holes to the organic layers. Anode material 115 preferably has a working function of greater than about 4 eV (a "high working function material"). Preferred anode materials include 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 lower emitter device. One preferred substrate and transparent anode combination is the commercially available ITO (anode) deposited on the glass or plastic (substrate). A flexible and transparent substrate-anode combination is disclosed in U.S. Pat. 5,844,363 and 6,602,540 B2, incorporated herein by reference in their entirety.

Anode 115 may be opaque and / or reflective. A reflective anode 115 may be preferred for some higher emitting devices to increase the amount of light emitted from the top of the device.

Anode material and thickness 115 may be chosen to obtain desired conductive and optical properties. In the event that anode 115 is transparent, there may be a thickness range for a particular material that is thick enough to provide the desired conductivity and thin enough to provide the desired degree of transparency. Other anode materials and structures may be used.

The transparent layer of the hole 125 may include a material capable of carrying holes. The hole transport layer 130 may be intrinsic (not doped) or doped. Doping can be used to improve conductivity. α-NPD and TPD are examples of intrinsic hole transport layers. An example of a layer

1-doped hole transport 1 is the F4-TCNQ-doped m-MTDATA at a 50: 1 molar ratio, as disclosed in Forrest et al., US Patent Application Publication No. 2003-0230980, included herein entirely for reference. Other hole transport layers can be used. '

Emitting layer 135 may include an organic material capable of emitting light when a current passes 25 between anode 115 and cathode 160. Preferably, emitting layer 135 contains a phosphorescent emitting material, although fluorescent emitting materials may also be used. Phosphorescent materials are preferred because of the higher luminescent efficiencies with such materials. Emission layer 135 may also consist of a host material capable of transporting electrons and / or holes doped with an emitting material that may trap electrons, holes and / or exocytes, so that the exocytes relax from the emitting material by of a photo-emitting mechanism. Emitter layer 135 may consist of a single material that combines transport and emission properties. If the emitting material is a dopant or a major constituent, the emitting layer 135 may consist of other materials, such as dopants that adjust the emission of the emitting material. Emitter layer 135 may include various emitter materials capable of in combination emitting a desired light spectrum. Examples of phosphorescent emissive materials include Ir (ppy) 3. Examples of fluorescent emissive materials include DCM and DMQA. Examples of host materials include Alq3, CBP and mCP. Examples of emissive materials and hosts are disclosed in Thompson, U.S. Patent No. 6,303,238, and others, incorporated herein by reference. Emissive materials may be included in emissive layer 135 in a number of ways. For example, a small emissive molecule may be incorporated into a polymer. This can be accomplished in several ways: by doping the small molecule into polymer 20 as a separate and distinct species; or incorporating the small molecule into the polymer backbone to form a copolymer; or by linking the small molecule as a pendant group on the polymer. Other emissive layer materials and structures may be used. For example, a molecule-emitting material may be present as the nucleus of a dendrimer.

The transparent layer of the hole 145 may include a material capable of carrying electrons. The electron transport layer 145 may be intrinsic (undoped) 30 or doped. Doping can be used to improve conductivity. Alq3 is an example of an intrinsic electron transport layer. An example of an n-doped electron transport layer is Li-doped BPhen at a 1: 1 molar ratio, as disclosed in Forrest, et al., US Patent Application Publication No. 2003-02309890, included herein entirely for reference. Other electron transport layers may be used.

Cathode 160 can be any material or combination

suitable for materials known in 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 10 are examples of suitable cathode materials. Cathode 160 may be a single layer or have a composite structure. Figure 1 shows a composite cathode 160 with a thin metal layer 162 and a thicker conductive metal oxide layer 164. In a composite cathode, the 15 preferred materials for the thicker layer 164 include ITO, IZO and other known materials. in art. U.S. Patent Nos. 5,703,436, 5,707,745, 6,548,956 B2 and 6,576,134 B2, all of which are incorporated herein by reference, disclose examples of cathodes including 20 cathodes composed of a thin metal layer such as Mg: Ag with a electrically deposited, electrically conductive overlapped transparent ITO layer. The portion of cathode 160 which is in contact with the underlying organic layer, if it is a single layer of cathode 160, the thin metal layer 162 of a composite cathode, or some other part, is preferably comprised of a material having a job function less than about 4 eV (a "low job function material"). Other cathode materials and structures may be used.

Locking layers can be used to reduce the amount of

number of charge carriers (electrons or holes) and / or exons leaving the emitting layer. An electron blocking layer 130 may be disposed between the emissive layer 135 and the hole transport layer 125 to block electrons and prevent them from exiting the emissive layer 135 towards the hole transport layer 125. Similarly, a hole blocking layer 140 may be disposed between the emissive layer 135 and the electron transport layer 145 to block the holes and prevent them from exiting the emissive layer 135 towards the electron transport layer 145. The locking layers They can also be used to block exocytes against diffusion of the emissive layer. The theory and use of 10 lock layers is described in more detail in U.S. Patent No. 6,097,147 and Forrest, U.S. Patent Application Publication No. 2003-02309890, and others, incorporated herein by reference in their entirety. .

As used herein and as may be understood by

As one skilled in the art, the term "blocking layer" means that the layer provides a barrier that significantly inhibits the transport of charge carriers and / or ecitons by the device, without necessarily suggesting that the layer completely blocks charge carriers and / or eccitons. The presence of such a lock layer on a device can result in efficiencies. considerably higher compared to a similar device without a lock layer. In addition, a lock layer may be used to confine emission in a desired region of an OLED.

In general, injection layers consist of a material that can enhance the injection of one-layer charge carriers, such as an electrode or an organic layer, into an adjacent organic layer. Injection layers can also perform a cargo transport function. In device 100, the hole injection layer 120 can be any layer that enhances the injection of anode 115 holes into the hole transport layer 125. CuPc is an example of a material that can be used as a hole injection layer. ITO 115 anode hole and other anodes. In device 100, the electron injection layer 150 can be any layer that enhances electron injection in the electron transport layer 14 5. LiF / Al is an example of a material that can be used as an electron injection layer. in the electron transport layer of an adjacent layer. Other materials or material combinations may be used for the injection layers. Depending on the configuration of a particular device, the injection layers may be arranged at locations other than those shown on device 100. Further examples of injection layers are provided in U.S. Patent Application Serial No. 09 / 931,948, and others, incorporated herein entirely by reference. A hole injection layer may consist of a material deposited from the solution, such as a spin-coated polymer, e.g. , PED0T: PSS, or may be a deposited small molecule material, e.g. , CuPc or MTDATA.

A hole injection layer (HIL) can flatten or wet the anode surface to provide efficient hole injection from the anode and into the hole injection material. A hole injection layer may also have a charge-bearing component containing HOMO (Highest Occupied Molecular Orbital) energy levels that match favorably as defined by their relative ionization potential (IP) energies described herein, with the adjacent anode on one side of the HIL and the transport layer on the opposite side of the HIL. The "load bearing component" is the material responsible for the HOMO energy level that actually carries the holes. This component may be the base material of HIL or may be a dopant. The use of doped HIL allows the dopant to be selected for its electrical properties, and the host to be selected for morphological properties such as wetness, flexibility, hardness, etc. Preferred properties for HIL material are those where the holes can be efficiently injected from the anode to HIL material. In particular, the HIL charge carrier component preferably has an IP not greater than 0.7 v and greater than the IP of the anode material. More preferably, the charge carrier component has an IP not greater than about 0.5 eV greater than the anode material. Similar considerations apply to any layer into which the holes are injected. HIL materials are further distinguished from conventional hole conveying materials in that they are generally used in the hole conveying layer of an OLED where such HIL materials may have a hole conductivity that is considerably less than the hole conductivity of the materials. hole conveyor systems. The thickness of the HIL of the present invention may be thick enough to help planar or wet the surface of the anode layer. For example, an HIL thickness of approximately 10 nm may be acceptable for a very smooth anode surface. However, since anode surfaces tend to be very rough, a thickness for HIL of up to 50 nm may be desired in some cases.

A protective layer can be used to protect the underlying layers during subsequent manufacturing processes. For example, processes used to fabricate upper metal or metal oxide electrodes can damage organic layers, and a protective layer can be used to reduce or eliminate this type of damage. In device 100, the protective layer 155 may reduce damage to the underlying organic layers during cathode 160 fabrication. Preferably, a protective layer has high carrier mobility for the type of carrier it carries (electrons in device 100) such as which does not significantly increase the operating voltage of the 100 device. CuPc, BCP and various metal phthalocyanines are examples of materials that can be used in the protective layers. Other materials or material combinations may be used. The thickness of the protective layer 155 is preferably thick enough that there is little or no damage to the underlying layers due to the manufacturing processes that run after the organic protective layer 160 is deposited, although not so thick as to significantly increase the operating stress of the layer. 100. The protective layer 155 may be doped to increase this conductivity. For example, a CuPc or BCP 160 protective layer may be Li-doped. A more detailed description of the protective layers can be found in U.S. Patent Application Serial No. 09 / 931,948 and others, included herein. i in full for reference.

Figure 2 shows an inverted OLED 200. The device includes a substrate 210, a cathode 215, an emitting layer 220, a hole transport layer 225, and an anode 230. The device 200 may be fabricated by depositing the 25 layers described in order. Since the most common OLED configuration has a cathode disposed on the anode, and device 200 has cathode 215 disposed on the anode 230, device 200 may be referred to as an "inverted" OLED. Materials similar to those described with respect to device 100 may be used in the corresponding layers of device 200. Figure 2 provides an example of how some layers may be omitted from device structure 100. The single layer structure shown in figures 1 and 2 It is provided by way of example without limitation and it is understood that the embodiments of the invention may be used in connection with a wide variety of other structures. The specific materials and structures described herein are examples only, and other materials and structures may be used. Functional OLEDs may be obtained by combining several layers described in different ways, or the layers may be omitted altogether based on design, performance, and cost factors. Other layers not specifically described may also be included. Other materials than those specifically described may be used. While many of the examples provided herein describe several layers that make up a single material, it is understood that combinations of materials, such as a host and dopant mixture or, in general, a mixture, may be used. In addition, layers can have multiple sublayers. The multi-layer names given here should not be strictly limiting. For example, in device 200, the hole transport layer 225 carries holes and injects them into the emissive layer 220 and can 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 anode. This organic layer may consist of a single layer, or it may consist of several layers of different organic materials, as described, for example, with reference to Figures 1 and 2.

Undisclosed structures and materials

specifically, they may also be used as OLEDs consisting of polymeric materials (PLEDs) as disclosed in U.S. No. 5,247,190, Friend, and others, incorporated herein by reference in their entirety. 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. Pat. 5,707,745 to Forrest, et al., Incorporated herein in their entirety for reference. The OLED structure may deviate from the single layer structure shown in Figures 1 and 2. For example, the substrate may include an angled reflective surface to enhance decoupling, such as a table-shaped structure, as described in US Pat. No. 6,091,195 to Forrest, et al., and / or a well-shaped structure as described in U.S. Patent No. 4,091,195. No. 5,834,893 to Bulovic, and others, incorporated herein in their entirety for reference.

Unless otherwise specified, any of the layers of the various representations may be deposited by any method. For organic layers, preferred methods include thermal evaporation, inkjet as described in U.S. Pat. 6,013,982 and 6,087,196, which are included in their entirety .For reference, Organic Vapor Deposition (OVPD), as described in Forrest U.S. Patent No. 6,337,102, and others, included for full reference and deposition by Organic Steam Jet Printing (OVJP) as described in U.S. Patent Application No. 10 / 233,470, incorporated herein by reference in its entirety. Other suitable deposition methods include spin coating and other solution based processes. Solution-based processes are preferably performed in nitrogen or in an inert atmosphere. For the other layers, preferred methods include thermal evaporation. Preferred exemplary methods include mask deposition, cold welding as described in U.S. Patent Nos. 6,294,398 and 6,468,819, which are incorporated herein by reference and model associated with some of the inkjet and OVJP deposition methods. . Other methods may also be used. The materials to be deposited can be modified to make them compatible with a specific deposition method. For example, substituents such as branched or unbranched alkyl and aryl groups and preferably containing at least three carbons may be used in small molecules to enhance their ability to undergo the solution process. Substitutes containing 20 carbons or more may be used and 3-20 carbons is a preferred range. Materials with asymmetric structures may have a better solution process than those with symmetrical structures, as asymmetric materials may have a lower tendency to recrystallize. Dendrimer substituents may be used to improve the ability of small molecules to undergo solution processing.

Devices manufactured in accordance with

Embodiments of the invention may be incorporated into a wide variety of consumer products, including flat panel monitors, computer monitors, televisions, billboards, indoor and outdoor lighting and / or signaling lights, visor, monitors.

Transparent displays, flexible monitors, laser printers, telephones, mobile phones, PDAs (Personal Digital Assistants), laptop computers, digital cameras, camcorders, displays, micromonitors, vehicles, large 30 walls, a movie or stadium screen or a sign. Various control mechanisms may be used to control devices manufactured in accordance with the present invention, including passive matrix and active matrix. Many of the devices are intended for use. at a temperature comfortable for humans, such as 18 ° C to 30 ° C and more preferably at room temperature (20 ° C to 25 ° C).

The materials and structures described herein may have applications in devices other than OLEDs. For example, other optoelectronic devices such as organic solar cells and organic photodetectors may employ materials and structures. In general, organic devices, such as organic transistors, may employ materials and structures.

In many cases, a large portion of light that shines

in an emissive layer in an OLED does not escape from the device due to internal reflection at the air interface, edge emission, heat dissipation. emissive layers or other layers, waveguide effects on emissive layer 15 or other device layers (i.e. transport layers, injection layers, etc.) and other effects. Light generated and / or emitted by an OLED can be described as in various modes, such as "air mode" (light will be emitted from a display surface of the device, 20 as through the substrate) or "guide mode". "(light is trapped in the device due to the effects of the waveguide). Specific modes can be described in relation to the layer or layers in which light is trapped, such as "organic mode" (light is trapped in one or more organic layers), "electrode mode" (trapped in an electrode), and "substrate mode" or "glass mode" (trapped in the substrate). In a common OLED, up to 50-60% of the light generated by the emissive layer can be trapped in a waveguide mode and therefore failure to exit the device may occur. In addition, up to 20-30% of the light emitted by the emissive material in an ordinary OLED can remain in a glass mode. Therefore, the decoupling efficiency of a common OLED can be low about 20%. To improve the decoupling efficiency of an OLED, regions of a transparent material with a low refractive index can be placed adjacent to regions containing an emissive material, in a direction parallel to one of the OLED electrodes. These regions can cause light emitted by the emissive material to enter a glass mode or air mode, increasing the proportion of light emitted from the device.

It is believed that the external amount efficiencies 10 of the higher emission and transparent OLEDs can be improved 2-3 times by incorporating periods of low index material into these devices without distorting the viewing spectra. It is understood that a transparent emission OLED refers to an OLED with considerably transparent upper and lower electrodes. It is also understood that a higher emission OLED refers to an OLED indicated for light emission only through the upper (transparent) electrode.

Figure 3A shows a schematic side view of a sample device 300 with low index regions 310. The device includes a substrate 304, electrodes 301 and 303 and a layer 302 having regions of one or more emissive materials 305 and regions of a low transparent index material 310. The device shown in Figure 3A 25 may also include various other layers and structures described herein.

The low index material preferably consists of a material having a refractive index less than the refractive index of the substrate and more preferably 0.15 to 0.4 less than the refractive index of the substrate, as this may increase the amount of the refractive index. of waveguide mode light converted to air mode and / or glass mode. It may be preferable in the low index material to have a refractive index of 1.0 to 1.3 and more preferably 1.0 to 1.05. Often, the low index material will have a lower refractive index than the organic materials used in the device, as the organic materials used in OLEDs generally have a refractive index of about 1.5-1.7. Various low index materials can be used for the low index region, such as Teflon, airgel, SiO2 and TiO2 graded films, and SiO2 nanorod layers. Various airgel are known in the art, such as silica, carbon, alumina and 10 other airgel. For example, a silica airgel may be manufactured by mixing a liquid alcohol with a silicon alkoxide precursor to form a sol-gel silicon dioxide. Alcohol is removed from the gel and replaced with a gas using various techniques known in the art. A prepared airgel using a sol-gel method may be preferred in some embodiments, as the refractive index can be controlled by changing proportions of the starting solutions. It is also preferred that the low index material be transparent. As used herein, a material will be "transparent" if, at the scale and size described for the low index layers and regions, the total optical loss of light passing through the low index layer or region in a direction approximately parallel to the electrodes is less than about 50%. The low index material may also be a non-emissive material.

For illustrative purposes, Figure 3A shows example rays 320, 330, 340 to indicate various possible results when light is emitted by emissive material in the 30 OLED. Although some light 330 produced by the emissive material may exit directly from the device, light 320 produced in a waveguide mode generally does not leave the emissive layer. In the example of ray-based optics shown in Figure A, this light 320 can be displayed on a path within the emissive layer at a sufficiently wide angle to the normal electrode that will never be incident on the emissive layer interface. Similarly, light from waveguide mode 340 may be modeled as a beam that is incident on the emissive layer interface, but an angle ângulo high enough to pass through the internal total reflection. This light is usually not emitted from the top or bottom of device 300, but can be emitted from a side surface. However, the low index regions near the emission regions may allow wur light that would normally not be emitted by the device, or that would only be emitted from one side of the device, to exit through a viewing surface of the device. As shown in Figure 3A, light entering the low index regions is refracted, allowing it to exit the device directly (320) or after reflection of an electrode (340). That is, light passing through the low index regions can be converted from waveguide mode to air mode, which allows it to be emitted from the device.

Although Figure 3A shows the boundaries between lower index regions 310 and adjacent organic regions 305 as flat interfaces perpendicular to electrodes and substrates, this may not always be the case. For example, various depositing methods may be used for low index ■ regions and / or organic regions that result in approximate boundaries, or boundaries that are not perpendicular to the substrate. Figure 3B shows an example of part of a device where the boundary between a low index region 30 and an adjacent organic region 305 is not precisely perpendicular to electrodes 301, 303. Although a specific configuration is illustrated, it will be understood that the Regions may have several different cross sections than those shown. In general, it is preferable that the boundary between adjacent regions 305, 310 be approximately perpendicular to a device electrode. As used herein, the boundary between two adjacent regions will be "approximately perpendicular" to a surface if the angle between the boundary and a normal surface plane is 20 ° or less. Therefore, in Figure 3B, the boundary between regions 305 and 310 is approximately perpendicular to electrode 303 when the illustrated angle 350 is 20 ° or less. The boundary between adjacent regions may also be approximated as shown in Figure 3C. In this configuration, regions will be "approximately perpendicular" to a surface if the angle between a best-fit plane 355 and a normal device surface plane is 20 ° or less. Therefore, the boundary 15 between regions 305, 310 shown in Figure 3C is approximately perpendicular to electrode 303 when the angle between the best fit plane 355 and a normal plane of electrode 303 is 20 ° or less. Although the drawings described herein are not drawn to scale, the features 20 illustrated in figures 3B-3C may be enlarged for illustration.

The low index region (s) may partially extend between the electrodes and / or other layers as shown in the 3D figure. For example, a low index material 310 may be deposited on an electrode 303. The low index material may be deposited in various patterns, grids and other structures as described above. One or more organic materials may be deposited on the electrode 303 and the low index 30 regions, resulting in an organic layer with an uneven surface. An electrode 301 or other layer may be deposited on the organic layer 305 so that the resulting surface is also uneven, or the electrode 301 or other layers may be deposited to create a smooth surface. A smooth layer 360 or other layer may also be deposited to create a uniform surface.

The low index region can be organized into various settings on the device. It is recommended that low index material be arranged in a grid. As used herein, a "grid" refers to a material repeating pattern. Figures 4A-4B show exemplary material arrangements and low index regions for use in a device. Figure 4A shows a top view of the low index material 410 arranged in a hexagonal grid. Figure 4B shows a top view of the low index material 410 arranged in a rectangular grid. The structures shown in figures 4A-4B may be placed in an OLED in a plane parallel to one or both electrodes. This device may have a cross section equivalent to the device illustrated in figure 3A. Emissive regions 420 may include emissive material, altering transport and / or blocking materials, and other structures and layers described herein. While it may be preferable for each repeated grid part to have approximately the same dimensions, the grid parts may have varying dimensions. For a regular pattern, that is, one where regions of emissive material are surrounded by low index regions, each having the same dimension, the grid may be characterized by a width of 421. For example, a common rectangular grid has regions. emissive ones that are square when viewed from above. Other grid types, such as triangular or octagonal, can also be used, as well as various other patterns and structures.

In some cases, the specific grid shape may be selected based on the desired qualities of the resulting device. For example, Figure 5A shows simulated values of the amount of light converted to air mode and glass mode for a device with low index material arranged in the grids shown in figures 4A and 4B for a range of refractive indices. Data is simulated for a device that has organic emissive regions of about 5 pm wide, low index regions of about 0.8 μπ \ wide, and an upper 100 nm thick ITO electrode. An amount of light converted at the end in air mode to a device with a square grid (vertical scatter) and a hexagonal grid (solid) is shown and in glass mode to a device with a square grid (horizontal scatter) and a hexagonal grid (diagonal spread). Levels approach these for a conventional OLED, ie one without low index regions, when the low index region is modeled 15 with a refractive index around 1.7-1.8 (510). This is expected since the organic materials commonly used in OLEDS may have refractive indices of about 1.7-1.8.

Figure 5B shows simulated emission for a device with a hexagonal grid of a low index material with a refractive index of 1.03. The width of the emissive regions is 5 pm, the width of the low index regions is 0.8 µm, and the electrode is a 100 nm ITO layer. When low index regions are used (horizontal scatter), the decoupling efficiency of the device may increase to 0.44 as shown. An ideal microlens OLED arranged on the viewing surface (cross-scatter) generally has a decoupling efficiency of about 0.32, while the measured value for this device is usually about 0.26. For a conventional (non-scattered) OLED, the decoupling efficiency of the modeled device is about 0.17. As shown in Figure 5A, as the refractive index of the low index region increases, more light is converted to glass mode, and less light is converted to air mode. In some cases, it may be useful to change the substrate-air interface so that it is not parallel to the plane of the organic layer, causing more light to be converted from glass to air mode. Therefore, the low index region can have a synergistic effect with settings that enhance the conversion from glass to air mode. Specifically, the low index region can convert light from an organic mode to a glass mode, and light from the glass mode can be converted to air mode due to the substrate configuration or composition. For example, a micro-lens slide 610, as shown in Figure 6A, may be arranged adjacent to the substrate, or the substrate may include a micro-lens or micro-lens slide. Other configurations may be used, such as centimeter-scale hemispherical glass lenses or a substrate that has a rough surface at the substrate-air interface. The substrate may also include different materials, such as materials having different refractive indexes; This can also increase the amount of light from glass mode converted to air mode. As shown in Figure 6B, a thin layer 620 of low index material such as airgel or Teflon may also be disposed between substrate 304 and the. electrode 303. This layer can also direct more light from glass mode to an electrode or organic mode, where it will enter a low index region and become the light from glass mode. Figures 7 and 8 show the calculated proportion of light

emitted by a device with the same basic structure as the device of figure 5B as a function of the viewing angle. Figure 7 shows the proportion of light emitted by a microlens device with a hexagonal grid of low index material with a refractive index of 1.03 (cross-scatter), 1.2 (without scatter) and 1.29 (solid ). As shown, the decoupling efficiency of the device may be 0.60. Figure 8 shows the proportion of light emitted by a conventional OLED, an OLED (non-scattered), an ideal micro-lens OLED (cross-scatter) and a micro-lens OLED and a hexagonal grid of a low index material with a refractive index of 1.29 (solid).

Figures 9 and 10 show the calculated proportion of light emitted as a function of the emission angle. The device has the same structure as described above, as well as a thin layer of a low index material inserted between the ITO electrode and the emissive material and low index regions separating adjacent regions of the emissive material. Figure 9 shows the light emitted by a conventional (non-scattered) OLED and a hexagonal grid OLED of a low index material having a refractive index of 1.2 and an inserted layer of Teflon AF having a refractive index of 1, 29 (cross scattering). Figure 10 shows the emission of a device having the same structure as Figure 9, but with the low index material having a refractive index of

1.29. The decoupling efficiency of the devices shown in figures 9 and 10 can be from 0.32 (for a refractive index of 1.29 of low index material) to

0.34 (refractive index 1.2).

The thin layer of low index material can serve to alter the angular distribution of light on the substrate by reducing the amount of light that passes through the total internal reflection at the substrate-air interface. Figures 11 and 12 show the angular distribution of light on the glass substrate without the low index layer and the low index layer of a material having a refractive index of 1.29, respectively. Distributions are shown for a conventional OLED (1110, 1120) and low index layer OLEDs with refractive indices of 1.03 (1120, 1220), 1.02 (1130, 1230) and 1.3 (1130, 1230 ).

Using the microlens slide shown

6A and the low index layer shown in FIG. 6B on the same device. The decoupling efficiency for this device can be up to 0.59. Figure 13 shows the proportion of light emitted as a function of the emission angle 10 for various device structures. Shown are the values of a conventional (non-scattered) OLED, an ideal micro-lens OLED (cross-scatter), a low index OLED with a refractive index of 1.29, a low index layer, and a microlens slide 15. (cross diagonal spread) and an OLED with a microlens slide and low index regions with a low index material region having a refractive index of 1.29 (solid).

Figure 18 shows an example device 20 having low index regions 1810. The device includes a substrate 1804, electrodes 1801 and 1803 and a layer 1802 having regions of one or more emissive materials 1805 and regions of a low index material. 1810. The device shown in Figure 18 may also include various other 25 layers and structures described herein.

The low index material preferably contains a material which has a refractive index lower than the refractive index of the emissive material, as this may increase the amount of light of the waveguide mode converted to air mode and / or glass mode. It may be preferable in the low index material to have a refractive index of 1.0 to 3.0 and more preferably 1.0 to 1.50. Various low index materials can be used for the low index region as described above. Figures 19A-19C show an example device with a low index grid (LIG) incorporated into the organic layer. The grid period (the spacing between the low index regions) can be micrometers and greater than 5 wavelengths of emitted light. This periodicity is believed to allow a large proportion of light in a waveguide mode to enter the low index region, which redirects the light toward the normal substrate from which it escapes from the device. It is also believed that since the periodicity of the LIG (about 5-20 µm) is of magnitude greater than the wavelength of the emitted light, the enhancement effect is independent of the wavelength. This can be useful for white emission TOLEDs, which can be characterized by a broad spectrum as there is no considerable distortion of the emission spectrum of the extracted light. The periodicity of the LIG is also greater than a magnitude smaller than a TOLED pixel (which is about 195 to 380 μπι) and therefore may not affect the alignment between the LIG pattern and TOLED pixels.

In addition, it is believed that the incorporation of a LIG

in a TOLED also eliminates roughness effects found on some devices, such as those reported in Cui and others, "Optimization of Light Extraction from OLEDs", Optics Express Vol. 15, No. 8 (April 16, 2007). For illustrative purposes. · Figure 18 shows radii of

example 1820, 1825, 1830, and 1835 to indicate several possible outcomes when light is emitted by emissive material in TOLED. Light 1830 produced in a waveguide mode generally cannot exit the emissive layer. In the example of ray-based optics shown in Figure 18, this light 1830 can be displayed on a path within the emissive layer at a sufficiently wide angle to the normal electrode that will never be incident on the emissive layer interface. Similarly, light from waveguide mode 1835 can be modeled as a beam that is incident on the emissive layer interface, but an angle Θ high enough to pass through the total internal reflection. Such light is normally not emitted from the top or bottom of the device 1800, but may be emitted from a side surface. However, the low index regions near the emission regions may allow wur light that would normally not be emitted by the device, or that would only be emitted from one side of the device, exit through a viewing surface of the device. As shown in Figure 18, light entering the low index regions is refracted toward the normal substrate, allowing it to exit the device either directly (1830) or after reflection from an electrode 15 (1835). That is, light passing through the low index regions can be converted from waveguide mode to air mode, which allows it to be emitted from the device. In addition, the ON does not affect light exiting directly from the top of the device (1820) 20 or the bottom (1825) for transparent devices.

Low-index material 1810 may be deposited on an electrode 1801. Low-index material may be deposited in various patterns, grids and other structures, as described above, "One or more organic materials 1805 may be deposited on electrode 1803. and low index regions 1810, resulting in an organic layer with an uneven surface. An electrode 1803 or other layer may be deposited on the organic layer 30 1805, so that the resulting surface will also be unrequited, or the electrode 1803 or others. layers can be deposited to create a smooth surface.

Although figure 18 shows the boundaries between lower index regions 1810 and adjacent organic regions 1805 as flat interfaces perpendicular to the electrodes and substrates, this may not always be the case, as illustrated, for example, in figures 3B and 3C.

Figures 19A-19C show an example TOLED device 1900 with an LIG 1910 embedded in the organic layer. The device includes a glass substrate 1901, ITO 1902 electrode, cathode 1904, and a layer 1903 having regions of one or more organic layers 1905 and LIG 1910. Figure 19B shows device 1900 with an LIG 1910 arranged in a rectangular grid oriented. in a plane parallel to the electrodes 1902 and 1904. Figure 19A shows the top view of the device 1900. Figure 19C shows an angled view and a cross section (side view) of this device. Organic layer 1905 may include emissive material, altering carrier and / or blocking materials and other structures and layers described herein. While it may be preferable for each repeated part of the LIG 1910 to have approximately the same dimensions, the grid parts may have variable dimensions. For example, a common rectangular grid has emissive regions that are square when viewed from above. Other grid types, such as triangular or octagonal, can also be used, as well as various other patterns and structures.

Figures 20A-20C show simulated emissions for a device with a rectangular grid of low index material having a refractive index of 1.03. The thickness of the low index regions is 100 nm, the organic layers are 100 nm and a lower ITO electrode is 120 nm. Figure 20C shows that enhancement is optimized when the thickness of the alloy is equal to the thickness of the organic layers. The ratio of enhancement may decrease as the thickness of the ON decreases.

Figure 20A shows that the enhancement ratio increases as the width of the organic region (IVorg) decreases as more light in waveguide mode is decoupled upon entering the LIG prior to absorption into the organic and ITO layers. Figure 20A also shows that the enhancement ratio increases as the width of the LIG increases (Wlig), as more light can be extracted from the waveguide mode without re-entering the organic layers.

For practical reasons, the organic layer width at these simulated emissions cannot be too small to ensure that the effective emission area is sufficient for the device to achieve the desired brightness. In Figures 20A-20C, the width of the LIG is 1 μm and the organic layers 6 μm, providing an effective illumination area of over 70%. Figure 20B shows that the decoupling efficiency of a higher emission OLED increases with decreasing LIG index. As the refractive index of the ON increases, more light is converted to glass mode and less is converted to air mode.

Figure 21 shows an exemplary device having an e-disposed microlens slide 610 adjacent the substrate, or the substrate may include a microlens or microlens slide. Figure 20B shows simulated light enhancement as a function of the refractive index for a higher emission OLED with one LIG (white bars) and one LIG and one microlens (shaded bars). The decoupling efficiency of these devices can be improved. by a factor of about 2-3.

The amount of light finally converted to air mode and emitted from the device can be further affected by changing other structural features of the device, such as electrode thickness, width of low index regions, and / or width of eressive regions. . Figures 14-17 show simulated results for variations in various device parameters. Unless otherwise indicated, each device was modeled with low index 0.8 ym wide regions on a periodic grid ID, 4 ym wide organic emissive regions, a 100 nm thick ITO electrode and a refractive index of 5 low index material of 1.03. Figure 14 shows the proportion of light in air mode (squares) and glass mode (circles) as a function of ITO thickness for thicknesses in the range of 70 to 150 nm. Figure 15 shows the proportion of light in each mode for regions of low variable width index, from 500 to 1200 nm. Figure 16 shows the proportion of light in various modes for a device with 4 ym to 10 ym organic regions. Figure 17 shows the proportion of light in each mode for refractive indices of low index material from 1 to 1.75 for 15 square and hexagonal grids. The values are shown for the air mode of an ideal ID 1710 periodic grid, a 1710 squared grid and a 1730 hex grid and for the glass mode of an ideal ID 1740 periodic grid, a 1750 square grid and a 1760 hex grid. The values indicated by the dotted oval marking are the same as those for conventional OLED. For the structures shown in figures 14-17, a conventional OLED ■ generally demonstrates light ratios of about 0.17 in air mode and 0.26 in glass mode.

It is understood that various representations described

herein are for example only and do not limit the scope of the invention. For example, many of the materials and structures described may be substituted for other materials and structures without departing from the principle of the invention. It is understood that various theories explaining how the invention works should not be restrictive. For example, charge transfer theories should not be restrictive.

Material definitions: As used herein, abbreviations refer to materials as follows: CBP: 4,4'-N, N-dicarbazole-biphenyl m-MTDATA 4,4 ', 4' -tris (3-methylphenylamino) triphenylamine Alk3: 8-trishydroxyquinoline aluminum Bphen: 4,7-diphenyl-1,10-phenanthroline F4-TCNQ: tetrafluoro-tetracyano-quinodimethane Ir (pp y) 3: tris (2-phenylpyridine) -iridium BCP: 2.9 -dimethyl-4,7-diphenyl-1,10-phenanthroline CuPc: copper phthalocyanine ITO: indium tin oxide NPD: N, N'-diphenyl-N-N'-di (1-naphthyl) benzidine TPD : N, N'-diphenyl-N-N'-di (3-tholi) -benzidine mCP: 1,3-N, N-dicarbazole-benzene DCM: 4- (dicyanoethylene) -6- (4-dimethylaminostyryl-2-methyl ) -4H -pyran DMQA: N, N'-dimethylquinacridone PEDOT: PSS: An aqueous dispersion of poly (3,4-ethylenedioxythiophene) with polystyrenesulfonate (PSS) Although the present invention is described herein with particular regard to particular examples. Preferred embodiments and embodiments, it is understood that the present invention is not restricted to such examples and embodiments. The present invention as claimed includes variations of the particular examples and preferred embodiments described herein as will be apparent to one skilled in the art.

Claims (16)

1. A device characterized by: a substrate; a first electrode disposed on the substrate; an organic layer disposed on first electrode; the organic layer characterized by: a first region characterized by an organic emissive material; and a second region characterized by periods of a low transparent index material incorporated into the organic layer, wherein the low index material has a refractive index lower than the refractive index of the organic emissive material; and a second electrode disposed on an organic layer; wherein the periods of low transparent index material incorporated into the organic layer offer decoupling efficiency over a broad spectrum without any distortion of the extracted light emission spectrum; and wherein at least one between the first and second electrodes is a transparent electrode. The device of claim 1, characterized in that the device is an upper transmission OLED. The device of claim 1, characterized in that the low index material has a refractive index of 1.0 a. 1.5. The device of claim 1, characterized in that the low index material forms a grid oriented in a plane parallel to the first electrode and the second electrode. The device of claim 4, characterized in that the grid is prepared with a periodicity and magnitude greater than the wavelength of the extracted light. The device of claim 1, characterized in that micro-lens blades are disposed between the substrate so that a convex side of the micro-lens blade is facing the opposite direction of the substrate. The device of claim 1, characterized in that the low index material is selected from the group consisting of airgel, Teflon, a SiO2 graduated film, a TiO2 graduated film and layers of SiO2 nanorods. 8. A device characterized by: a substrate; a first electrode disposed on the substrate; a first layer disposed on the first electrode, the layer consists of: a first region characterized by an organic emissive material; and a second region consisting of a low index material with a refractive index less than the refractive index of the organic emissive material; wherein the second region is disposed adjacent to the first; and a second electrode e. arranged on the first layer; wherein at least one between 〇 first and second electrodes is a transparent electrode; and ... wherein the light emitted by the organic emissive material is a waveguide mode redirected by the second region to a direction that can escape the device through the transparent electrode. The device of claim 8, characterized in that the device is an upper transmission OLED. The device of claim 9, characterized in that the low index material has a refractive index of 1.0 to 3.0. The device of claim 10, characterized in that the low index material has a refractive index of 1.0 to 1.5. The device of claim 8, characterized in that the low index material forms a grid oriented in a plane parallel to the first electrode and the second electrode. The device of claim 12, characterized in that the grid is prepared more frequently than the wavelength of light. The device of claim 8, characterized in that microlens slides are disposed between the substrate, so that a convex side of the microlens slide is facing the opposite direction of the substrate. The device of claim 8, characterized in that the low index material is selected from the group consisting of airgel, Teflon, a SiO2 graded film, a TiO2 graded film and layers of SiO2- (nanoscale objects) nanorods. A method of manufacturing a light-emitting device consisting of: depositing a first electrode on a substrate; depositing a grid of low index material having a refractive index of 1.0 to 1.5 on the first electrode; depositing an organic emissive material on the grid so that the organic emissive material comes into direct contact with the grid or the first electrode; and depositing a second electrode on the organic emissive material; wherein at least one between the first and second electrodes is a transparent electrode; and wherein the grid of low index material redirects the light emitted by the organic emissive material from a waveguide mode to a direction that can escape from the device through the transparent electrode.