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Definitions

• the claimed invention was made by, on behalf of, and/or in connection with one or more of the following parties to a joint university corporation research agreement: Regents of the University of Michigan, Princeton University, The University of Southern California, and the Universal Display Corporation. The agreement was in effect on and before the date the claimed invention was made, and the claimed invention was made as a result of activities undertaken within the scope of the agreement.
• the present invention is directed to organic light emitting devices (OLEDs). More specifically, the present invention relates to phosphorescent light emitting materials and devices that may have improved device lifetime.
• 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.
• OLEDs organic light emitting devices
• the wavelength at which an organic emissive layer emits light may generally be readily tuned with appropriate dopants.
• 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.
• phosphorescent emissive molecules are full color display.
• Industry standards for such a display call for pixels adapted to emit particular colors, referred to as "saturated" colors.
• these standards call for saturated red, green, and blue pixels. Color may be measured using CIE coordinates, which are well known to the art.
• One example of a green emissive molecule is tris(2-phenylpyridine) iridium, denoted Ir(ppy) 3 , which has the structure of Formula I:
• 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 dendrimer, which consists of a series of chemical shells built on the core moiety.
• the core moiety of a dendrimer may be a 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 OLEDs are small molecules.
• top means furthest away from the substrate, while “bottom” means closest to the substrate.
• bottom means closest to the substrate.
• 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 contact with” the second Patent Application
• a cathode may be described as "disposed over" an anode, even though there are various organic layers in between.
• solution processible means capable of being dissolved, dispersed, or transported in and/or deposited from a liquid medium, either in solution or suspension form.
• a ligand may be referred to as "photoactive” when it is believed that the ligand directly contributes to the photoactive properties of an emissive material.
• a ligand may be referred to as "ancillary” when it is believed that the ligand does not contribute to the photoactive properties of an emissive material, although an ancillary ligand may alter the properties of a photoactive ligand.
• a first "Highest Occupied Molecular Orbital” (HOMO) or “Lowest Unoccupied Molecular Orbital” (LUMO) energy level is “greater than” or "higher than” a second HOMO or LUMO energy level if the first energy level is closer to the vacuum energy level.
• IP ionization potentials
• a higher HOMO energy level corresponds to an IP having a smaller absolute value (an IP that is less negative).
• a higher LUMO energy level corresponds to an electron affinity (EA) having a smaller absolute value (an EA that is less negative).
• the LUMO energy level of a material is higher than the HOMO energy level of the same material.
• a "higher” HOMO or LUMO energy level appears closer to the top of such a diagram than a "lower” HOMO or LUMO energy level.
• a first work function is "greater than” or “higher than” a second work function if the first work function has a higher absolute value. Because work functions are generally measured as negative numbers relative to vacuum level, this means that a "higher” work function is more negative. On a conventional energy level diagram, with the vacuum level at the top, a “higher” work function is illustrated as further away from the vacuum level in the downward direction. Thus, the definitions of HOMO and LUMO energy levels follow a different convention than work functions.
• a new type of materials is provided.
• the new class of materials has a dibenzothiophene-containing compound selected from the group consisting of:
• each of Ri through R 6 are independently selected from the group consisting of any aryl and alkyl substituents and H, and where each of Ri through R 6 may represent multiple substitutions. In one aspect, all of Ri through R 6 are H.
• An organic light emitting device has an anode, a cathode, an and an organic layer disposed between the anode and the cathode.
• the organic layer further comprises a material containing a compound from the group consisting of Compound IG through 12G, as described above, with or without substituents.
• the organic layer is an emissive layer having a host and an emissive dopant, and the compound is the host.
• the compound may also preferably be used as a material in an enhancement layer.
• New materials are provided.
• the materials have a dibenzothiophene-containing and/or dibenzofuran-containing compound selected from the group consisting of: Patent Application
• An organic light emitting device has an anode, a cathode, and an organic layer disposed between the anode and the cathode.
• the organic layer further comprises a material containing a compound from the group consisting of Compound 2G through 35G, as described above, with or without substituents.
• the organic layer is an emissive layer having a host and an emissive dopant, and the compound is the host.
• the compound may also preferably be used as a material in an enhancement layer.
• a consumer product is also provided.
• the product contains a device that has an anode, a cathode, and an organic layer disposed between the anode and the cathode, where the organic layer further comprises a material containing a compound from the group consisting of Compounds 2G through 35G, as described above, with or without substituents.
• FIG. 1 shows an organic light emitting device.
• FIG. 2 shows an inverted organic light emitting device that does not have a separate electron transport layer.
• FIG. 3 shows an organic light emitting device including compounds disclosed herein.
• FIG. 4 shows a plot of normalized luminescence versus time for the device of FIG. 3.
• FIG. 5 shows a plot of external quantum efficiency versus luminance for the device of FIG. 3.
• FIG. 6 shows a plot of power efficacy versus luminance for the device of FIG. 3.
• FIG. 7 shows a plot of luminance versus voltage for the device of FIG. 3.
• FIG. 8 shows a plot of EL intensity versus wavelength for the device of FIG. 3.
• FIG. 9 shows an organic light emitting device including compounds disclosed herein.
• FIG. 10 shows a plot of external quantum efficiency versus luminance for the device of FIG. 9.
• FIG. 11 shows a plot of power efficacy versus luminance for the device of FIG. 9.
• FIG. 12 shows a plot of luminance versus voltage for the device of FIG. 9.
• FIG. 13 shows a plot of EL intensity versus wavelength for the device of FIG. 9.
• FIG. 14 shows a dibenzothiophene-containing compound.
• an OLED comprises at least one organic layer disposed between and electrically connected to an anode and a cathode.
• the anode injects holes and the cathode injects electrons into the organic layer(s).
• the injected holes and electrons each migrate toward the oppositely charged electrode.
• 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.
• 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 undesirable.
• the initial OLEDs used emissive molecules that emitted light from their singlet states ("fluorescence") as disclosed, for example, in U.S. Pat. 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.
• FIG. 1 shows an organic light emitting device 100.
• Device 100 may include a substrate 110, an anode 115, a hole injection layer 120 (HIL), a hole transport layer 125 (HTL), 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. The properties and functions of these various layers, as well as example materials, are described in more detail in US 7,279,704 at cols. 6-10, which are incorporated by reference.
• each of these layers are available.
• a flexible and transparent substrate-anode combination is disclosed in U.S. Pat. No. 5,844,363, which is incorporated by reference in its entirety.
• An example of a p-doped hole transport layer is m- MTDATA doped with F.sub.4-TCNQ at a molar ratio of 50:1, as disclosed in U.S. Patent Application Publication No. 2003/0230980, which is incorporated by reference in its entirety.
• Examples of emissive and host materials are disclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which is incorporated by reference in its entirety.
• n- doped electron transport layer is BPhen doped with Li at a molar ratio of 1 : 1 , as disclosed in U.S. Patent Application Publication No. 2003/0230980, which is incorporated by reference in its entirety.
• Mg metal
• ITO overlying transparent, electrically-conductive, sputter- deposited ITO layer.
• FIG. 2 shows an inverted OLED 200.
• the device includes a substrate 210, a 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 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.
• FIG. 2 provides one example of how some layers may be omitted from the structure of device 100.
• FIGS. 1 and 2 The simple layered structure illustrated in FIGS. 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.
• 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 emissive layer 220, and may be described as a hole transport layer or a hole injection layer.
• 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 further comprise multiple layers of different organic materials as described, for example, with respect to FIGS. 1 and 2.
• OLEDs comprised of polymeric materials (PLEDs) such as disclosed in U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated by reference in its entirety.
• PLEDs polymeric materials
• OLEDs having a single organic layer may be used.
• OLEDs may be stacked, for example as described in U.S. Pat. No. 5,707,745 to Forrest et al, which is incorporated by reference in its entirety.
• the OLED structure may deviate from the simple layered structure illustrated in FIGS. 1 and 2.
• the substrate may include an angled reflective surface to improve out-coupling, such as a mesa structure as described in U.S. Pat. No. 6,091,195 to Forrest et al., and/or a pit structure as described in U.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated by reference in their entireties.
• any of the layers of the various embodiments may be deposited by any suitable method.
• preferred methods include thermal evaporation, ink-jet, such as described in U.S. Pat. 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. Pat. 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 Ser. No. 10/233,470, which is incorporated by reference in its entirety.
• OVPD organic vapor phase deposition
• OJP organic vapor jet printing
• Other suitable deposition methods include spin coating and other solution based processes.
• Solution based processes are preferably carried out in nitrogen or an inert atmosphere.
• preferred methods include thermal evaporation.
• Patent Application include deposition through a mask, cold welding such as described in U.S. Pat. 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 OVJD. Other methods may also be used.
• the materials to be deposited may be modified to make them compatible with a particular deposition method. For example, substituents such as alkyl 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 processibility 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, heads up displays, fully transparent displays, flexible displays, laser printers, telephones, cell phones, personal digital assistants (PDAs), laptop computers, digital cameras, camcorders, viewfmders, micro-displays, vehicles, a large area wall, theater or stadium screen, or a sign.
• PDAs personal digital assistants
• Various control mechanisms may be 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 C).
• the materials and structures described herein may have applications in devices other than OLEDs.
• other optoelectronic devices such as organic solar cells and organic photodetectors may employ the materials and structures.
• organic devices such as organic transistors, may employ the materials and structures.
• halo halogen, alkyl, cycloalkyl, alkenyl, alkynyl, arylkyl, heterocyclic group, aryl, aromatic group, and heteroaryl are known to the art, and are defined in US 7,279,704 at cols. 31-32, which are incorporated herein by reference.
• Dibenzo[ ⁇ , ⁇ i]thiophene also referred to herein as "dibenzothiophene"
• dibenzothiophene dibenzo[ ⁇ , ⁇ i]thiophene-containing materials are provided, which can be used in the PHOLED devices fabricated by both vapor deposition or solution processing, giving long lifetime stable devices with low voltage.
• PHOLED devices may be used as a stable host in PHOLED devices, or in other layers, such as an enhancement layer.
• Dibenzothiophenes and dibenzofurans may be used as hole and/or electron transporting organic conductors, they usually exhibit more reversible electrochemical reduction in solution than some common organic groups, such as biphenyl.
• the triplet energies of dibenzothiophenes and dibenzofurans are relatively high. Therefore, a compound containing dibenzothiophene and/or dibenzofuran may be advantageously used as a host or a material for an enhancement layer in PHOLED devices. For example, the triplet energy of dibenzothiophene is high enough for use in a blue or green PHOLED device.
• Dibenzothiophene and/or dibenzofuran-containing compounds may provide improved device stability while maintaining good device efficiency.
• Dibenzothiophene-containing materials may have the following general structure:
• Each of Ri and R 2 may be independently selected from the group consisting of any alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, heteroaryl, and hydrogen, and where Ri and R 2 may represent multiple substitutions.
• dibenzothiophene compounds are provided, which may be advantageously used in OLEDs, having the following structures:
• Each of Ri through R 6 are independently selected from the group consisting of any alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, heteroaryl, and hydrogen, and where each of Ri through R 6 may represent multiple substitutions.
• Dibenzothiophene-containing and/or dibenzofuran-containing compounds are provided, which may be advantageously used in OLEDs, having the following structures:
• Each of Ri through Rg are independently selected from the group consisting of any alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, heteroaryl, and hydrogen, and where each of Ri through R 8 may represent multiple substitutions.
• dibenzothiophene-containing and/or dibenzofuran-containing compounds are provided, which may be advantageously used in OLEDs, are provided:
• Particular host-dopant combinations for the emissive layer of an OLED are also provided which may lead to devices having particularly good properties.
• devices having an emissive layer using Hl as the host and Pl, P2, or P7 as an emissive dopant are demonstrated to have particularly good properties.
• Such devices may be particularly favorable when the emissive layer includes two organic layers, a first organic layer including Hl doped with Pl, and a second organic layer including Hl doped with P2, as illustrated in FIG. 3.
• devices having an emissive layer using Compound 1 as the host and P3, P4 and / or P5 as dopants may lead to devices having particularly good properties.
• Such devices may be particularly favorable when the emissive layer includes two organic layers, a first organic layer including Compound 1 doped with P3, and a second organic layer including Compound 1 doped with P4 and P5, as illustrated in FIG. 9.
• Devices having an emissive layer using Compound 23 as the host and Pl as the dopant may also lead to devices having particularly good properties.
• a consumer product comprising a device having an anode, a cathode, and an organic layer, disposed between the anode and the cathode.
• the organic layer further Patent Application
• Ri through R 8 are independently selected from the group consisting of any alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, heteroaryl and hydrogen, and where each of Ri through Rg may represent multiple substitutions.
• the materials described herein as useful for a particular layer in an organic light emitting device may be used in combination with a wide variety of other materials present in the device.
• emissive dopants disclosed herein may be used in conjunction with a wide variety of hosts, transport layers, blocking layers, injection layers, electrodes and other layers that may be present.
• the materials described or referred to below are non-limiting examples of materials that may be useful in combination with the compounds disclosed herein, and one of skill in the art can readily consult the literature to identify other materials that may be useful in combination.
• hole injection materials In addition to and / or in combination with the materials disclosed herein, many hole injection materials, hole transporting materials, host materials, dopant materials, exiton/hole blocking layer materials, electron transporting and electron injecting materials may be used in an OLED.
• Non- limiting examples of the materials that may be used in an OLED in combination with materials disclosed herein are listed in Table 1 below. Table 1 lists non- limiting classes of materials, non- limiting examples of compounds for each class, and references that disclose the materials.
• Step 1 3,3'-dihydroxybiphenyl (9.3 g, 50 mmol) was dissolved in 100 mL of CH 2 Cl 2 , followed by the addition of pyridine (15.8 g, 200 mmol). To this solution at -15°C, Tf 2 O (42.3 g, 150 mmol) was added dropwise. The mixture was continued to stir at room temperature for 5 h. The organic phase was separated and washed with brine once. The crude product was further purified by a silica column. 3,3'-ditriflatebiphenyl was obtained as pale white solid (21.3 g).
• Step 2 To a 500 mL round flask was added 3,3'-ditrifiatebiphenyl (2.7 g, 6 mmol), 4-dibenzothiopheneboronic acid (4.1 g, 18 mmol), Pd 2 (dba) 3 (0.2 g, 0.2 mmol), 2- dicyclohexylphosphino-2',6'-dimethoxybiphenyl (0.3 g, 0.8 mmol), potassium phosphate tribasic (5.1 g, 24 mmol), and 150 mL of toluene. The reaction was heated to reflux and stirred under a nitrogen atmosphere for 24 hours. After cooling, the mixture was purified by a silica gel column. Yield was 2.6 g.
• Step 1 2,6-Dibromo-l,3,5-trimethylbenzene (8.34 g, 30 mmol) was dissolved in 50 ml of CHCI 3 and suspended with 1.0 g of iron powder in 200 ml round-bottom flask. Bromine (2.00 ml, 31 mmol) was added dropwise at room temperature and reaction mixture was heated to reflux for 3 hours, cooled down to room temperature and stirred overnight. Solution was decanted, washed with NaOH 10% aq., filtered and evaporated. The solid residue was crystallized from chloroform, providing 7.00 g of yellow solid (2,4,6-tribromo- 1 ,3,5-trimethylbenzene).
• Step 2 The 1 L round-bottom flask equipped with magnetic stirrer and reflux condenser was charged with 2,4,6-tribromo-l,3,5-trimethylbenzene (3.4 g, 9.5 mmol), A- dibenzothiopheneboronic acid (8.7 g, 38 mmol), Pd 2 (OAc) 2 (0.16 g, 0.7 mmol), 2- dicyclohexylphosphino-2',6'-dimethoxybiphenyl (0.46 g, 1.1 mmol), potassium phosphate tribasic (53 g, 250 mmol), 1.2 ml of water and 700 mL of toluene. The reaction was heated to reflux and stirred under a nitrogen atmosphere for 24 hours. After cooling, the mixture was purified by a silica gel column. Yield was 5.2 g.
• lithium amide (0.2 g, 10 mmol), 4-iododibenzothiophene (9.9 g, 32 mmol), Pd 2 (dba) 3 (0.2 g, 0.2 mmol), 2-dicyclohexylphosphino-2',4',6'- triisopropylbiphenyl (0.4 g, 0.8 mmol), sodium t-butoxide (2.9 g, 30 mmol), and 200 mL of toluene were added. The reaction was heated to reflux and stirred under a nitrogen atmosphere for 24 hours. After cooling, the mixture was purified by a silica gel column. Yield was 4.O g.
• Step 1 Dibenzothiophene (9.21 g, 50 mmol) was dissolved in 100 ml of dry THF and solution was cooled to -50 0 C. n-BuLi (1.6 molar solution in hexanes, 40 ml, 64 mmol) was added dropwise. The reaction mixture was warmed to room temperature, stirred for 4 hours and cooled to -30 0 C. Dibenzofluorenone (9.0 g, 50 mmol) in 70 ml THF was added dropwise, reaction mixture was allowed to warm to room temperature and stirred overnight.
• n-BuLi 1.6 molar solution in hexanes, 40 ml, 64 mmol
• reaction mixture was diluted with ethyl acetate (75 ml), washed with brine 3 times, dried over MgSO 4 , filtered and evaporated.
• the solid residue was purified by column chromatography on silica (hexane/ethyl acetate 7/3) providing 12.0 g of 9- (dibenzo[ ⁇ ,d]thiophen-4-yl)-9H-fluoren-9-ol as white solid.
• Step 2 9-(Dibenzo[ ⁇ J]thiophen-4-yl)-9H-fiuoren-9-ol (product from the Step 1, 3.64 g, 10 mmol) were dissolved in 100 ml of dry toluene. Twenty drops of 10% solution of P2O5 in CH3SO3H were added at room temperature, and reaction mixture was stirred for 5 hours. The solution was decanted from solid residue, filtered through silica plug and evaporated. The solid residue was subjected to column chromatography (silica, hexane/ethyl acetate 4/1) providing 4.O g of white solid.
• Step 1 The 200 ml round-bottom flask equipped with reflux condenser and magnetic stirrer was charged with carbazole (14.75 g, 88 mmol), 3-iodobromobenzene (25.0 g, 88 mmol), Pd 2 (dba) 3 (0.8 g, 0.85 mmol) and dppf (l,l '-bis(diphenylphosphino)ferrocene, 0.98 g, 1.8 mmol), sodium t-buthoxide (25 g, 265 mmol) and 100 ml of dry xylene.
• Step 2 9-(3-Bromophenyl)-9H-carbazole (11.7 g, 36 mmol), Bis(pinacolato)diboron (13.85 g, 54 mmol), potassium acetate (7.00 g, 71 mmol), 1,1'- bis(diphenylphosphino)ferrocene]dichloropalladium (II) (0.6 g) were dissolved in 100 ml of dry dioxane and refluxed under N 2 atmosphere overnight. Then reaction mixture was cooled down to room temperature, diluted with ethyl acetate, washed with brine, dried over magnesium sulfate, and evaporated.
• Step 3 2-Bromoanisole (5.61 g, 30 mmol) and 4-dibenzothiopheneboronic acid (6.84 g, 30 mmol), Pd 2 (PPh 3 ) 4 (1.00 g, 0.8 mmol) were dissolved in 100 ml of toluene. Saturated solution of sodium carbonate (12.5 g in water) was added, and reaction mixture was heated to reflux under N 2 atmosphere overnight. Then reaction mixture was cooled down to room temperature, separated organic phase and evaporated toluene.
• Step 4 4-(2-Methoxyphenyl)dibenzo[ ⁇ i]thiophene (6.6 g, 23 mmol) and pyridinium hydrochloride (27 g, 230 mmol) were mixed together, placed in the 100 ml round bottom flask and heated to reflux for 45 min. Reaction mixture was cooled to 60 0 C, diluted with 100 ml water and extracted with ethyl acetate. The organic phase was separated, dried over magnesium sulfate, filtered and evaporated.
• Step 6 The 200 ml round bottom flask with reflux condenser and magnetic stirrer was charged with triflate from Step 5 (4.1 g, 10 mmol) and boronic ester from Step 2 (3.7 g, 10 mmol) followed by tribasic potassium phosphate (6.36 g, 30 mmol), palladium acetate (0.67 g, 0.3 mmol), ), 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (0.8 g, 0.6 mmol), 200 ml of toluene and 6 ml of water. The reaction was heated to reflux and stirred under a nitrogen atmosphere for 24 hours. After cooling, the mixture was purified by a silica gel column with eluent hexane/ethyl acetate 4/1, providing 2.8 g of target compound as white solid.
• Step 1 Dibenzothiophene (27 g, 147 mmol) in 400 mL of THF was treated slowly with n-BuLi (1.6 M in hexane, 100 mL, 160 mmol) at -50 0 C. The resulting mixture was slowly warmed up to room temperature and continued to stir for 5 h. The solution was cooled back to -78 0 C, DMF (61 mL) inlOO mL of THF was added slowly. The mixture continued to stir for another 2 h at this temperature and then warmed up to room temperature. The product was extracted with EtOAc and further purified by a silica gel column. Yield of 4-dibenzothiophenealdhyde was 21 g.
• Step 2 To a 300 mL of THF solution of 2,8-dibromodibenzothiophene (3.4 g, 10 mmol) at -78 0 C was added slowly by n-BuLi (1.6 M in hexane, 13.8 mL, 22 mmol). After stirred for 1 h at this temperature, the mixture was treated slowly with a 100 mL of THF solution of 4-dibenzothiophenealdhyde (4.2 g, 20 mmol). The solution was then allowed to Patent Application
• Step 3 To a 50 mL Of CH 2 Cl 2 solution of above dicarbinol intermediate (4.5 g, 7.4 mmol) and CF3COOH (60 mL) was added portionwise of solid powder of sodium borohydride (2.8 g, 74 mmol. The mixture was stirred under nitrogen overnight. The solvents was removed by rotovap, and the solid was washed with water then with NaHCO 3 solution. The crude product was further purified by a silica gel column. Yield of final product was 2.4 g.
• reaction mixture was heated to reflux and stirred under nitrogen atmosphere for 24 hours. Then reaction was cooled down to room temperature, filtered through silica plug and evaporated. The residue was washed with hexane, ethanol, water, ethanol and hexane, then was crystallized from toluene. Sublimation (255 0 C at 10 "5 mm Hg) provided pure material (white solid, 2.O g, structure confirmed by NMR.
• Triflate (5.56 g, 10 mmol), 4-dibenzothiopheneboronic acid (5.35 g, 25 mmol), palladium (II) acetate (44 mg), 2-dicylohexylphosphino-2',6'-dimethoxybiphenyl (161 mg) and potassium phosphate tribasic trihydrate (7.00 g) were suspended in 100 ml of toluene and refluxed under nitrogen atmosphere for 24 hours. Hot reaction mixture was filtered and evaporated, the residue was crystallized from toluene twice. Sublimation (245 0 C, 10 "5 mm Hg) provided 5.O g of target compound.
• All example devices were fabricated by high vacuum ( ⁇ 10 ⁇ 7 Torr) thermal evaporation.
• the anode electrode is ⁇ 8O ⁇ A, 1200A or 2OO ⁇ of indium tin oxide (ITO), or 800A Sapphire/IZO.
• the cathode consists of IOA of LiF followed by IOOOA of Al.
• AU devices are encapsulated with a glass lid sealed with an epoxy resin in a nitrogen glove box ( ⁇ 1 ppm ofH 2 O and O 2 ) immediately after fabrication, and a moisture getter was incorporated inside the package.
• the organic stack of Device Examples 1-8 consisted of sequentially, from the ITO surface (1200 A), 100 A of Pl as the hole injection layer (HIL), 300 A of 4,4'-bis[N-(l- naphthyl)-N-phenylamino]biphenyl ( ⁇ -NPD) as the hole transporting layer (HTL), 300 A of the invention compound doped with 10 or 15 wt% of an Ir phosphorescent compound as the emissive layer (EML), 5 ⁇ A or 100 A of HPT or the invention compound as the ETL2 and 400 or 450 A of tris-8-hydroxyquinoline aluminum (AIq 3 ) as the ETLl.
• HIL hole injection layer
• ⁇ -NPD 4,4'-bis[N-(l- naphthyl)-N-phenylamino]biphenyl
• HTL hole transporting layer
• EML emissive layer
• AIq 3 tris-8-hydroxyquinoline aluminum
• Comparative Example 1 was fabricated similarly to the Device Examples except that CBP was used as the host.
• T 8 o% (defined as the time required for the initial luminance, L 0 , to decay to 80% of its value, at a constant current density of 40 mA/cm 2 at room temperature) are 300 hours and 105 hours respectively, with Device Example 3 having a slightly higher Lo. This translates to almost a 3 fold improvement in the device stability.
• the invention compounds may function well as the enhancement layer (ETL2).
• Device Example 1 and Device Example 3 both have Compound 1 as the host, but Compound 1 and 2,3,6,7,10,11-hexaphenyltriphenylene (HPT) as the enhancement layer respectively. They have To.8 of 325 and 300 hours respectively with similar Lo (-13600 cd/m 2 ), indicating the good performance of the invention compound as the enhancement layer.
• arylbenzothiophenes particularly biphenyl substituted dibenzothiophenes, are excellent hosts and enhancement layer for phosphorescent OLEDs, providing as least the same efficiency and multiple times of improvement in stability compared to the commonly used CBP as the host.
• the devices had an ITO anode, a hole injection layer of LG101TM (purchased from LG Chemical, Korea), and an emissive layer having a first organic layer and a second organic layer with an interface in between.
• Some of the devices had an enhancement layer (ETL2).
• All of the devices had an electron transport layer (ETLl) of LG201, available from the same source as LGlOl.
• Devices 9-16 have first and second organic layers with the same non-emissive materials, and different phosphorescent materials, where the first organic layer additionally includes a lower energy emissive material. All of devices 9-16 include emissive layers having a first and second organic layer with an interface in between.
• the concentration of phosphorescent material is higher in the first (closer to anode) organic layer.
• the materials and thicknesses for Device Examples 9-16 are provided in Table 4. The devices were tested, and the results measured are provided in Table 5. Compound is abbreviated using the term Cmpd. All percentages are wt% unless otherwise noted.
• Device Examples 9, 10 and 11 From Device Examples 9, 10 and 11, it can be seen that the efficiency of the device decreased with increasing concentration of P3, and the device CIE red- shifted with decreasing P3 concentration.
• Device Examples 9-11 differ only in the concentration of the emissive compound P3 (i.e., devices contain varying concentrations of P3) as all of Device Examples 9-11 contained Inventive Compound 1 as the host, and were without a blocking layer between the EML and the LG201.
• Devices 12-14 differ only in the concentration of the emissive compounds P3, as all of devices 12-14 contained the inventive Compound 1 as the host and the blocking layer situated between the EML and ETL.
• Compound 1 is an efficient electron transport and blocking layer material, because the efficiency of each of Devices 12, 13, and 14 was shown to exceed that of Devices 9, 10, and 11.
• the electron stability of Compound 1 was found to be significant, because Devices 12-14 demonstrated an LT 6 o% stability that exceeded 100,000 hrs from 1,000 cd/m 2 initial luminance.
• the organic stack of Device Examples 17-20 consisted of sequentially, from the ITO surface, IOOA of Pl as the hole injection layer (HIL), 3O ⁇ A of NPD as the hole transport layer (HTL), 3O ⁇ A of the invention compound doped with 10 wt% or 15 wt% of Pl, an Ir phosphorescent compound, as the emissive layer (EML), 5 ⁇ A or IOOA of HPT or the invention compound as enhancement layer (ETL2), an electron transport layer (ETLl) of AIq 3 having a thickness identified in Table 5, and a LiF/ Al cathode.
• the BL and ETL have a sum total of 5O ⁇ A.
• the data in Table 6 describes the performance of Devices Examples 17-20.
• the voltage, luminous efficiency, external quantum efficiency and power efficiency data were measured at 1000 cd/m 2 (display level brightness). The lifetime was measured at accelerated conditions: 40 ma/cm 2 DC.
• the initial device luminance (L 0 ) at life-test conditions (40 mA/cm 2 ) is also shown in Table 5.
• Compound 23 was used as a host for the green phosphorescent emitter Pl.
• Two different dopant concentrations (10% or 15%) and two different ETLl layers (AIq 3 of 400 A or 450 A) were varied in the devices and tested experimentally. The data show no significant difference in the device performance due to dopant concentration variation.
• the organic stack of Device Examples 21-24 consisted of sequentially, from the anode surface, IOOA of Pl or LGlOl as the hole injection layer (HIL), 3O ⁇ A of NPD as the hole transport layer (HTL) or no HTL, 300 A of the invention compound doped with 9 wt%, 15 wt% or 20 wt% of P2 or P7 Ir phosphorescent compounds as the emissive layer (EML), 5 ⁇ A, 15 ⁇ A or 25 ⁇ A of Hl as the enhancement layer (ETL2), and 2O ⁇ A, 3O ⁇ A or 4O ⁇ A of AIq 3 as the electron transport layer (ETLl).
• IOOA of Pl or LGlOl as the hole injection layer
• HTL hole transport layer
• Examples 21-24 are provided in Table 7. The devices were tested, and the corresponding results measured are provided in Table 8.
• Devices 21, 22, 23, and 24 demonstrate differences between device structures having an emissive layer containing Hl and an emissive compound P2 or P7.
• Device Example 21 did not have an HTL, and used a thick EML to enhance device operational stability.
• the measured CIE coordinates of Device Example 21 were not blue saturated, so the structures of Device Examples 22, 23, and 24 used a 30nm EML.
• Device Example 22 also incorporated a 200nm ITO layer to saturate the device blue CIE.
• Device Example 23 was a standard blue PHOLED that was not optimized for operational stability.
• Device Example 24 was a blue PHOLED using the same emissive compound P7 as used in Device Example 23.
• Device Example 24 had several features that enabled longevity such as no NPD, sapphire heat sink substrate, a thick blocking layer, and high emitter concentration. Hence, the LTgo% of Device Example 24 exceeded the LT 8 o % of Device Example 23, and Device Example 24 had improved blue CIE compared to Device Example 23.
• FIG. 3 shows an organic light emitting device having only a layer with a high hole conductivity between an emissive layer and the anode, an enhancement layer of the same material used as a non-emissive host in the emissive layer, and an emissive layer having first Patent Application and second organic layers with different concentrations of phosphorescent material and non- emissive materials, where the concentration of phosphorescent material in the second organic layer is variable.
• FIG. 4 shows a plot of normalized luminescence versus time for the device of FIG.
• FIG. 5 shows a plot of external quantum efficiency versus luminance for the device of FIG. 3.
• FIG. 6 shows a plot of power efficacy versus luminance for the device of FIG. 3.
• FIG. 7 shows a plot of luminance versus voltage for the device of FIG. 3.
• FIG. 8 shows a plot of EL intensity versus wavelength for the device of FIG. 3.
• FIG. 9 shows an organic light emitting device having only a layer with a high hole conductivity between an emissive layer and the anode, an enhancement layer of the same material used as a non-emissive host in the emissive layer, and an emissive layer having first and second organic layers with different phosphorescent materials in the first and second organic layers, where the concentration of phosphorescent material in the second organic emissive layer is variable.
• the device of FIG. 9 is very similar to that of FIG. 3, with the difference being that the device of FIG.
• FIG. 10 shows a plot of external quantum efficiency versus luminance for the device of FIG. 9.
• FIG. 11 shows a plot of power efficacy versus luminance for the device of FIG. 9.
• FIG. 12 shows a plot of luminance versus voltage for the device of FIG. 9.
• FIG. 13 shows a plot of EL intensity versus wavelength for the device of FIG. 9.
• the device of FIG. 9 may be compared to the device of FIG. 3.
• the devices are similar except in the emissive layer, where the device of FIG. 9 has an emissive layer doped with phosphorescent emitter Pl and another emissive layer doped phosphorescent emitter P2, whereas the device of FIG. 3 has only phosphorescent emitter P2.
• Both devices have a step in dopant concentration, and similar concentrations even in the layers where the actual dopant is different.
• the device of FIG. 9 exhibits a broad emission spectra that is a combination of emission from both Pl and P2. As a result, it can be inferred that the device of FIG.
• FIG. 9 is emitting from both the layer doped with 30% P2 and the layer doped with a lesser concentration of P2. Comparing FIG. 5 to FIG. 10, it can be seen that the device of FIG. 9 has better charge balance than the device of FIG. 3, as evidenced by a relatively flat external quantum efficiency over three orders of magnitude for the device of FIG. 9 as compared to two orders of magnitude for the device of FIG. 3.

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