Organic electroluminescent materials and devices

Abstract

The present invention relates in part to compounds containing indolocarbazole and terphenyl building blocks. These compounds are useful for application in organic electroluminescent devices wherein the combination of indolocarbazoles with terphenyl groups leads to novel compounds that demonstrate superior device performance.

Claims

1. An organic light emitting device (OLED) comprising: an anode; a cathode; and an organic layer, disposed between the anode and the cathode, comprising a compound having a formula selected from the group consisting of Formula I and Formula II: ##STR00336## wherein R is selected from the group consisting of: ##STR00337## wherein R.sup.4 is selected from the group consisting of ##STR00338## wherein X is Se; wherein R.sup.1, R.sup.2 and R.sup.3 each independently represents mono to maximum allowable substitutions, or no substitution; wherein R.sup.1, R.sup.2 and R.sup.3 are each independently selected from the group consisting of hydrogen, deuterium, alkyl, alkenyl, alkyne, alkoxy, halogen, silyl, nitrile, nitro, aryl, heteroaryl and combinations thereof; wherein any two adjacent substituents are optionally joined or fused into a ring; wherein R.sup.4, R.sup.1, R.sup.2, and R.sup.3 are each independently, optionally, further substituted with one or more substituents selected from the group consisting of hydrogen, deuterium, alkyl, alkenyl, alkyne, alkoxy, halogen, silyl, nitrile, nitro, aryl, heteroaryl, and combinations thereof; and wherein any hydrogen in the compound is optionally replaced with deuterium.

2. The OLED of claim 1, wherein the organic layer is an emissive layer and the compound of Formula I, or II is a host.

3. The OLED of claim 1, wherein the organic layer further comprises a phosphorescent emissive dopant; wherein the emissive dopant is a transition metal complex having at least one ligand or part of the ligand if the ligand is more than bidentate selected from the group consisting of: ##STR00339## ##STR00340## wherein each Y.sup.1 to Y.sup.13 are independently selected from the group consisting of carbon and nitrogen; wherein Y′ is selected from the group consisting of BR.sub.e, NR.sub.e, PR.sub.e, O, S, Se, C═O, S═O, SO.sub.2, CR.sub.eR.sub.fRR, SiR.sub.eR.sub.f, and GeR.sub.eR.sub.f; wherein R.sub.e and R.sub.f are optionally fused or joined to form a ring; wherein each R.sub.a, R.sub.b, R.sub.c, and R.sub.d may independently represent from mono substitution to the maximum possible number of substitution, or no substitution; wherein each R.sub.a, R.sub.b, R.sub.c, R.sub.d, R.sub.e, and R.sub.f is independently selected from the group consisting of hydrogen, deuterium, fluorine, alkyl, cycloalkyl, heteroalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, aryl, heteroaryl, nitrile, isonitrile, and combinations thereof; and wherein any two adjacent substituents of R.sub.a, R.sub.b, R.sub.c, and R.sub.d are optionally fused or joined to form a ring or form a multidentate ligand.

4. The OLED of claim 1, wherein the organic layer is a blocking layer and the compound of Formula I, or II is a blocking material in the organic layer.

5. The OLED of claim 1, wherein the organic layer is a transporting layer and the compound of Formula I, or II is a transporting material in the organic layer.

6. A consumer product comprising the OLED of claim 1.

7. The consumer product of claim 6, wherein the consumer product is selected from the group consisting of a flat panel display, a curved display, a computer monitor, a medical monitor, a television, a billboard, a light for interior or exterior illumination and/or signaling, a heads-up display, a fully or partially transparent display, a flexible display, a rollable display, a foldable display, a stretchable display, a laser printer, a telephone, a cell phone, tablet, a phablet, a personal digital assistant (PDA), a wearable device, a laptop computer, a digital camera, a camcorder, a viewfinder, a micro-display that is less than 2 inches diagonal, a 3-D display, a virtual reality or augmented reality display, a vehicle, a video walls comprising multiple displays tiled together, a theater or stadium screen, and a sign.

8. A compound having a formula selected from the group consisting of Formula I and Formula II: ##STR00341## wherein R is selected from the group consisting of: ##STR00342## wherein R.sup.4 is selected from the group consisting of ##STR00343## wherein X is Se; wherein R.sup.1, R.sup.2 and R.sup.3 each independently represents mono to maximum allowable substitutions, or no substitution; wherein R.sup.1, R.sup.2 and R.sup.3 are each independently selected from the group consisting of hydrogen, deuterium, alkyl, alkenyl, alkyne, alkoxy, halogen, silyl, nitrile, nitro, aryl, heteroaryl and combinations thereof; wherein any two adjacent substituents are optionally joined or fused into a ring; wherein R.sup.4, R.sup.1, R.sup.2, and R.sup.3 are each independently, optionally, further substituted with one or more substituents selected from the group consisting of hydrogen, deuterium, alkyl, alkenyl, alkyne, alkoxy, halogen, silyl, nitrile, nitro, aryl, heteroaryl, and combinations thereof; and wherein any hydrogen in the compound is optionally replaced with deuterium.

9. The compound of claim 8, wherein the first compound is Formula I.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an organic light emitting device.

(2) FIG. 2 shows an inverted organic light emitting device that does not have a separate electron transport layer.

DETAILED DESCRIPTION

(3) Generally, an OLED comprises at least one organic layer 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 each migrate toward the oppositely charged electrode. When an electron and hole localize on the same molecule, an “exciton,” which is a localized electron-hole pair having an excited energy state, is formed. Light is emitted when the exciton relaxes via a photoemissive mechanism. In some cases, the exciton may be localized on an excimer or an exciplex. Non-radiative mechanisms, such as thermal relaxation, may also occur, but are generally considered undesirable.

(4) 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.

(5) More recently, OLEDs having emissive materials that emit light from triplet states (“phosphorescence”) have been demonstrated. Baldo et al., “Highly Efficient Phosphorescent Emission from Organic Electroluminescent Devices.” Nature, vol. 395, 151-154, 1998; (“Baldo-I”) and Baldo et al., “Very high-efficiency green organic light-emitting devices based on electrophosphorescence,” Appl. Phys. Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), are incorporated by reference in their entireties. Phosphorescence is described in more detail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporated by reference.

(6) FIG. 1 shows an organic light emitting device 100. The figures are not necessarily drawn to scale. Device 100 may include a substrate 110, an anode 115, a hole injection layer 120, a hole transport layer 125, an electron blocking layer 130, an emissive layer 135, a hole blocking layer 140, an electron transport layer 145, an electron injection layer 150, a protective layer 155, a cathode 160, and a barrier layer 170. 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 U.S. Pat. No. 7,279,704 at cols. 6-10, which are incorporated by reference.

(7) More examples for each of these layers are available. For example, 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. An example of an 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. U.S. Pat. Nos. 5,703,436 and 5,707,745, which are incorporated by reference in their entireties, disclose examples of cathodes including compound cathodes having a thin layer of metal such as Mg:Ag with an overlying transparent, electrically-conductive, sputter-deposited ITO layer. The theory and use of blocking layers is described in more detail in U.S. Pat. No. 6,097,147 and U.S. Patent Application Publication No. 2003/0230980, which are incorporated by reference in their entireties. Examples of injection layers are provided in U.S. Patent Application Publication No. 2004/0174116, which is incorporated by reference in its entirety. A description of protective layers may be found in U.S. Patent Application Publication No. 2004/0174116, which is incorporated by reference in its entirety.

(8) 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.

(9) 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. Functional OLEDs may be achieved by combining the various layers described in different ways, or layers may be omitted entirely, based on design, performance, and cost factors. Other layers not specifically described may also be included. Materials other than those specifically described may be used. Although many of the examples provided herein describe various layers as comprising a single material, it is understood that combinations of materials, such as a mixture of host and dopant, or more generally a mixture, may be used. Also, the layers may have various sublayers. The names given to the various layers herein are not intended to be strictly limiting. For example, in device 200, hole transport layer 225 transports holes and injects holes into emissive layer 220, and may be described as a hole transport layer or a hole injection layer. In one embodiment, an OLED may be described as having an “organic layer” disposed between a cathode and an anode. This organic layer may comprise a single layer, or may further comprise multiple layers of different organic materials as described, for example, with respect to FIGS. 1 and 2.

(10) Structures and materials not specifically described may also be used, such as OLEDs comprised of polymeric materials (PLEDs) such as disclosed in U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated by reference in its 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. 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. For example, 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.

(11) Unless otherwise specified, any of the layers of the various embodiments may be deposited by any suitable method. For the organic layers, 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. Pat. No. 7,431,968, which is incorporated by reference in its entirety. Other suitable deposition methods include spin coating and other solution based processes. Solution based processes are preferably carried out in nitrogen or an inert atmosphere. For the other layers, preferred methods include thermal evaporation. Preferred patterning methods include deposition through a mask, cold welding such as described in 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 processability 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.

(12) Devices fabricated in accordance with embodiments of the present invention may further optionally comprise a barrier layer. One purpose of the barrier layer is to protect the electrodes and organic layers from damaging exposure to harmful species in the environment including moisture, vapor and/or gases, etc. The barrier layer may be deposited over, under or next to a substrate, an electrode, or over any other parts of a device including an edge. The barrier layer may comprise a single layer, or multiple layers. The barrier layer may be formed by various known chemical vapor deposition techniques and may include compositions having a single phase as well as compositions having multiple phases. Any suitable material or combination of materials may be used for the barrier layer. The barrier layer may incorporate an inorganic or an organic compound or both. The preferred barrier layer comprises a mixture of a polymeric material and a non-polymeric material as described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos. PCT/US2007/023098 and PCT/US2009/042829, which are herein incorporated by reference in their entireties. To be considered a “mixture”, the aforesaid polymeric and non-polymeric materials comprising the barrier layer should be deposited under the same reaction conditions and/or at the same time. The weight ratio of polymeric to non-polymeric material may be in the range of 95:5 to 5:95. The polymeric material and the non-polymeric material may be created from the same precursor material. In one example, the mixture of a polymeric material and a non-polymeric material consists essentially of polymeric silicon and inorganic silicon.

(13) Devices fabricated in accordance with embodiments of the invention can be incorporated into a wide variety of electronic component modules (or units) that can be incorporated into a variety of electronic products or intermediate components. Examples of such electronic products or intermediate components include display screens, lighting devices such as discrete light source devices or lighting panels, etc. that can be utilized by the end-user product manufacturers. Such electronic component modules can optionally include the driving electronics and/or power source(s). Devices fabricated in accordance with embodiments of the invention can be incorporated into a wide variety of consumer products that have one or more of the electronic component modules (or units) incorporated therein. A consumer product comprising an OLED that includes the compound of the present disclosure in the organic layer in the OLED is disclosed. Such consumer products would include any kind of products that include one or more light source(s) and/or one or more of some type of visual displays. Some examples of such consumer products include flat panel displays, curved displays, computer monitors, medical monitors, televisions, billboards, lights for interior or exterior illumination and/or signaling, heads-up displays, fully or partially transparent displays, flexible displays, rollable displays, foldable displays, stretchable displays, laser printers, telephones, mobile phones, tablets, phablets, personal digital assistants (PDAs), wearable devices, laptop computers, digital cameras, camcorders, viewfinders, micro-displays (displays that are less than 2 inches diagonal), 3-D displays, virtual reality or augmented reality displays, vehicles, video walls comprising multiple displays tiled together, theater or stadium screen, and a sign. 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.), but could be used outside this temperature range, for example, from −40 degree C. to +80 degree C.

(14) 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 the materials and structures. More generally, organic devices, such as organic transistors, may employ the materials and structures.

(15) The term “halo,” “halogen,” or “halide” as used herein includes fluorine, chlorine, bromine, and iodine.

(16) The term “alkyl” as used herein contemplates both straight and branched chain alkyl radicals. Preferred alkyl groups are those containing from one to fifteen carbon atoms and includes methyl, ethyl, propyl, I-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl, pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, and the like. Additionally, the alkyl group may be optionally substituted.

(17) The term “cycloalkyl” as used herein contemplates cyclic alkyl radicals. Preferred cycloalkyl groups are those containing 3 to 10 ring carbon atoms and includes cyclopropyl, cyclopentyl, cyclohexyl, adamantyl, and the like. Additionally, the cycloalkyl group may be optionally substituted.

(18) The term “alkenyl” as used herein contemplates both straight and branched chain alkene radicals. Preferred alkenyl groups are those containing two to fifteen carbon atoms. Additionally, the alkenyl group may be optionally substituted.

(19) The term “alkynyl” as used herein contemplates both straight and branched chain alkyne radicals. Preferred alkynyl groups are those containing two to fifteen carbon atoms. Additionally, the alkynyl group may be optionally substituted.

(20) The terms “aralkyl” or “arylalkyl” as used herein are used interchangeably and contemplate an alkyl group that has as a substituent an aromatic group. Additionally, the aralkyl group may be optionally substituted.

(21) The term “heterocyclic group” as used herein contemplates aromatic and non-aromatic cyclic radicals. Hetero-aromatic cyclic radicals also means heteroaryl. Preferred hetero-non-aromatic cyclic groups are those containing 3 to 7 ring atoms which includes at least one hetero atom, and includes cyclic amines such as morpholino, piperidino, pyrrolidino, and the like, and cyclic ethers, such as tetrahydrofuran, tetrahydropyran, and the like. Additionally, the heterocyclic group may be optionally substituted.

(22) The term “aryl” or “aromatic group” as used herein contemplates single-ring groups and polycyclic ring systems. The polycyclic rings may have two or more rings in which two carbons are common to two adjoining rings (the rings are “fused”) wherein at least one of the rings is aromatic, e.g., the other rings can be cycloalkyls, cycloalkenyls, aryl, heterocycles, and/or heteroaryls. Preferred aryl groups are those containing six to thirty carbon atoms, preferably six to twenty carbon atoms, more preferably six to twelve carbon atoms. Especially preferred is an aryl group having six carbons, ten carbons or twelve carbons. Suitable aryl groups include phenyl, biphenyl, triphenyl, triphenylene, tetraphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, and azulene, preferably phenyl, biphenyl, triphenyl, triphenylene, fluorene, and naphthalene. Additionally, the aryl group may be optionally substituted.

(23) The term “heteroaryl” as used herein contemplates single-ring hetero-aromatic groups that may include from one to five heteroatoms. The term heteroaryl also includes polycyclic hetero-aromatic systems having two or more rings in which two atoms are common to two adjoining rings (the rings are “fused”) wherein at least one of the rings is a heteroaryl, e.g., the other rings can be cycloalkyls, cycloalkenyls, aryl, heterocycles, and/or heteroaryls. Preferred heteroaryl groups are those containing three to thirty carbon atoms, preferably three to twenty carbon atoms, more preferably three to twelve carbon atoms. Suitable heteroaryl groups include dibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole, indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine, preferably dibenzothiophene, dibenzofuran, dibenzoselenophene, carbazole, indolocarbazole, imidazole, pyridine, triazine, benzimidazole, 1,2-azaborine, 1,3-azaborine, 1,4-azaborine, borazine, and aza-analogs thereof and aza-analogs thereof. Additionally, the heteroaryl group may be optionally substituted.

(24) The alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, heterocyclic group, aryl, and heteroaryl may be unsubstituted or may be substituted with one or more substituents selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, cyclic amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.

(25) As used herein, “substituted” indicates that a substituent other than H is bonded to the relevant position, such as carbon. Thus, for example, where R.sup.1 is mono-substituted, then one R.sup.1 must be other than H. Similarly, where R.sup.1 is di-substituted, then two of R.sup.1 must be other than H. Similarly, where R.sup.1 is unsubstituted, R.sup.1 is hydrogen for all available positions.

(26) The “aza” designation in the fragments described herein, i.e. aza-dibenzofuran, aza-dibenzothiophene, etc. means that one or more of the C—H groups in the respective fragment can be replaced by a nitrogen atom, for example, and without any limitation, azatriphenylene encompasses both dibenzo[f,h]quinoxaline and dibenzo[f,h]quinoline. One of ordinary skill in the art can readily envision other nitrogen analogs of the aza-derivatives described above, and all such analogs are intended to be encompassed by the terms as set forth herein.

(27) It is to be understood that when a molecular fragment is described as being a substituent or otherwise attached to another moiety, its name may be written as if it were a fragment (e.g. phenyl, phenylene, naphthyl, dibenzofuryl) or as if it were the whole molecule (e.g. benzene, naphthalene, dibenzofuran). As used herein, these different ways of designating a substituent or attached fragment are considered to be equivalent.

(28) Both indolocarbazole and oligophenylenes have excellent charge-transport properties, useful for organic electronic devices. According to this invention, selected indolocarbazoles with favorable HOMO/LUMO energy levels and high triplet energy are combined with terphenyl to create novel compounds demonstrating superior performance in OLEDs. Further derivatization on these compounds provides additional advantages for this class of compounds.

(29) Often, the emissive layer (EML) of OLED devices exhibiting good lifetime and efficiency requires more than two components (e.g. 3 or 4 components). Fabricating such EMLs using vacuum thermal evaporation (VTE) process then requires evaporating 3 or 4 evaporation source materials in separate VTE sublimation crucibles, which is very complicated and costly compared to a standard two-component EML with a single host and an emitter, which requires only two evaporation sources.

(30) Premixing two or more materials and evaporating them from one VTE sublimation crucible can reduce the complexity of the fabrication process. However, the co-evaporation must be stable and produce an evaporated film having a composition that remains constant through the evaporation process. Variations in the film's composition may adversely affect the device performance. In order to obtain a stable co-evaporation from a mixture of compounds under vacuum, it may be assumed that the materials must have the same evaporation temperature under the same condition. However, this may not be the only parameter one has to consider. When two compounds are mixed together, they may interact with each other and the evaporation property of the mixture may differ from their individual properties. On the other hand, materials with slightly different evaporation temperatures may form a stable co-evaporation mixture. Therefore, it is extremely difficult to achieve a stable co-evaporation mixture. So far, there have been very few stable co-evaporation mixture examples. “Evaporation temperature” of a material is measured in a vacuum deposition tool at a constant pressure, normally between 1×10.sup.−7 Torr to 1×10.sup.−8 Torr, at a 2 Å/sec deposition rate on a surface positioned at a set distance away from the evaporation source of the material being evaporated, e.g. sublimation crucible in a VTE tool. The various measured values such as temperature, pressure, deposition rate, etc. disclosed herein are expected to have nominal variations because of the expected tolerances in the measurements that produced these quantitative values as understood by one of ordinary skill in the art.

(31) Many factors other than temperature can contribute to the ability to achieve stable co-evaporation, such as the miscibility of the different materials and the phase transition temperatures of the different materials. In one aspect of the invention, it was found that when two materials have similar evaporation temperatures, and similar mass loss rate or similar vapor pressures, the two materials can co-evaporate consistently. “Mass loss rate” of a material is defined as the percentage of mass lost over time (“percentage/minute” or “%/min”) and is determined by measuring the time it takes to lose the first 10% of the mass of a sample of the material as measured by thermal gravity analysis (TGA) under a given experimental condition at a given constant temperature for a given material after a steady evaporation state is reached. The given constant temperature is one temperature point that is chosen so that the value of mass loss rate is between about 0.05 to 0.50% d/min. A skilled person in this field should appreciate that in order to compare two parameters, the experimental condition should be consistent. The method of measuring mass loss rate and vapor pressure is well known in the art and can be found, for example, in Bull. et al. Mater. Sci. 2011, 34, 7, which is incorporated herein by reference in its entirety.

(32) In the state of the art OLED devices, the EML may consist of three or more components. In one example, the EML can consist of two host-type compounds and an emitter combination (e.g. a hole transporting cohost (h-host), an electron transporting cohost (e-host), and a compound capable of functioning as an emitter in an OLED at room temperature). In another example, the EML can consist of one host-type compound and two emitter-type compounds (e.g., a host compound and two compounds each capable of functioning as an emitter in an OLED at room temperature). Conventionally, in order to fabricate such EMLs having three or more components using VTE process, three or more evaporation sources are required, one for each of the components. Because the concentration of the components is important for the device performance, typically, the rate of deposition of each component is measured individually during the deposition process. This makes the VTE process complicated and costly. Thus, it is desired to premix at least two of the components of such EMLs to reduce the number of VTE evaporation sources.

(33) If any two of the three or more components of the EMLs can be premixed and form a stable mixture of co-evaporation source, then the number of evaporation sources required for EML layer fabrication would be reduced. In order for materials to be premixable into an evaporation source, they should co-evaporate and deposit uniformly without changing the ratio. The ratio of the components in the mixture should be the same as the ratio of the components in the evaporation deposited films from these premixed materials. Therefore, the concentration of the two components in the deposited film is controlled by their concentration in the premixed evaporation source.

(34) Compounds of the Invention

(35) The compounds of the present invention may be synthesized using techniques well-known in the art of organic synthesis. The starting materials and intermediates required for the synthesis may be obtained from commercial sources or synthesized according to methods known to those skilled in the art.

(36) In one aspect, the invention relates to a compound having a formula selected from the group consisting of:

(37) ##STR00004## wherein R is selected from the group consisting of:

(38) ##STR00005## wherein R.sup.4 is selected from the group consisting of alkyl, alkoxy, silyl, aryl, heteroaryl, and combinations thereof; wherein R.sup.1, R.sup.2 and R.sup.3 each independently represents mono to maximum allowable substitutions, or no substitution; wherein R.sup.1, R.sup.2 and R.sup.3 are each independently selected from the group consisting of hydrogen, deuterium, alkyl, alkenyl, alkyne, alkoxy, halogen, silyl, nitrile, nitro, aryl, heteroaryl and combinations thereof; wherein any two adjacent substituents are optionally joined or fused into a ring; wherein R.sup.4, R.sup.1, R.sup.2, and R.sup.3 are each independently, optionally, further substituted with one or more substituents selected from the group consisting of hydrogen, deuterium, alkyl, alkenyl, alkyne, alkoxy, halogen, silyl, nitrile, nitro, aryl, heteroaryl, and combinations thereof; and wherein any hydrogen in the compound is optionally replaced with deuterium.

(39) In one embodiment, the formula is Formula I. In another embodiment, the formula is Formula II. In another embodiment, R.sup.1, R.sup.2 and R.sup.3 are each a hydrogen.

(40) In one embodiment, R.sup.4 is selected from the group consisting of

(41) ##STR00006## ##STR00007##
and combinations thereof. wherein X is selected from a group consisting of O, S and Se.

(42) In another aspect, the invention relates to a compound selected from the group consisting of:

(43) ##STR00008## ##STR00009## ##STR00010## ##STR00011## ##STR00012## ##STR00013## ##STR00014## ##STR00015## ##STR00016## ##STR00017## ##STR00018## ##STR00019## ##STR00020## ##STR00021## ##STR00022## ##STR00023## ##STR00024## ##STR00025## ##STR00026## ##STR00027## ##STR00028## ##STR00029## ##STR00030## ##STR00031##

(44) In another aspect, the present invention includes a composition of materials comprising a first compound, wherein the first compound has a formula selected from the group consisting of Formula I and Formula II.

(45) In one embodiment, the composition comprises a second compound, wherein the second compound is selected from the group consisting of:

(46) ##STR00032## wherein G.sup.1 is selected from the group consisting of dibenzofuran, dibenzothiophene, dibenzoselenophene, triphenylene, and fluorene; wherein L.sup.1, L.sup.2, and L.sup.3 are each independently selected from the group consisting of a direct bond, phenyl, biphenyl, terphenyl, pyridine, pyrimidine, and combinations thereof; wherein G.sup.4 is selected from the group consisting of phenyl, biphenyl, terphenyl, naphthalene, phenanthrene, triphenylene, pyridine, pyrimidine, pyrazine, quinoline, isoquinoline, phenanthroline, and combinations thereof; wherein G.sup.2, G.sup.3, and G.sup.5 are each independently selected from the group consisting of phenyl, biphenyl, terphenyl, fluorene, naphthalene, phenanthrene, pyridine, pyrimidine, pyrazine, quinoline, isoquinoline, phenanthroline, aza-fluorene, carbazole, and combinations thereof; wherein G.sup.1, G.sup.2, G.sup.3, G.sup.4, and G.sup.5 are each optionally further substituted with one or more unfused substituents selected from the group consisting of deuterium, alkyl, alkoxyl, cycloalkyl, cycloalkoxyl, halogen, nitro, nitrile, silyl, phenyl, biphenyl, terphenyl, pyridine, and combinations thereof; wherein m is an integer from 0 to 7, wherein n is an integer from 0 to 4; wherein, when m or n is larger than 1, each G.sup.4 or G.sup.5 can be the same or different; wherein when n is 0, then m is equal to or greater than 1, and each G.sup.4 is selected from the group consisting of phenyl and biphenyl; wherein when n is equal to or greater than 1, L.sup.1 is not a direct bond; and wherein when m and n are both 0, L.sup.1 is biphenyl; and

(47) ##STR00033## wherein L.sup.4 and L.sup.5 are each independently selected from the group consisting of a direct bond, phenyl, biphenyl, terphenyl, pyridine, pyrimidine, and combinations thereof; wherein R.sup.5, R.sup.6, and R.sup.7 each represent mono to the maximum allowable substitution, or no substitution; wherein R.sup.8 and R.sup.9 are each independently a substituted or unsubstituted aryl or heteroaryl group; wherein at least one of R.sup.8 and R.sup.9 is selected from the group consisting of:

(48) ##STR00034## wherein R.sup.10 represents mono to the maximum allowable substitution, or no substitution; wherein R.sup.3, R.sup.6, R.sup.7, R.sup.10, and R.sup.11 are each independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; and wherein any two substituents may be joined or fused together to form a ring.

(49) In one embodiment, each R.sup.5, R.sup.6, R.sup.7, R.sup.10, and R.sup.11 is independently selected from the group consisting of hydrogen, deuterium, fluorine, alkyl, cycloalkyl, heteroalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, aryl, heteroaryl, nitrile, isonitrile, and combinations thereof.

(50) In one embodiment, G.sup.2, G.sup.3 and G.sup.5 are independently selected from the group consisting of:

(51) ##STR00035## ##STR00036## wherein R.sup.B1 and R.sup.B2 are independently selected from a group consisting of hydrogen, deuterium, alkyl, alkenyl, cycloalkyl, alkoxyl, aryl, heteraryl, halogen, and combinations thereof; and wherein R.sup.B1 and R.sup.B2 are optionally joined to form a ring.

(52) In one embodiment, R.sup.8 and R.sup.9 are independently selected from the group consisting of:

(53) ##STR00037## ##STR00038##

(54) In one embodiment, L.sup.4 is a direct bond, and L.sup.5 is a phenyl ring.

(55) In one embodiment, at least one of R.sup.8 or R.sup.9 is

(56) ##STR00039## wherein A.sup.2 and A.sup.3 are each independently selected from the group consisting of hydrogen, phenyl, biphenyl, terphenyl, naphthalene, and combinations thereof.

(57) In one embodiment, L.sup.4 and R.sup.8 are fused together to form a ring. In one embodiment, L.sup.5 and R.sup.9 are fused together to form a ring.

(58) In one embodiment, the second compound has the formula:

(59) ##STR00040## ##STR00041## wherein X is selected from the group consisting of O, S and Se; wherein A.sup.1 represents mono to the maximum allowable substitution, or no substitution; and wherein each A.sup.1, A.sup.2, and A.sup.3 is independently selected from the group consisting of hydrogen, phenyl, biphenyl, terphenyl, naphthalene, and combinations thereof.

(60) In one embodiment, the second compound is selected from the group consisting of:

(61) TABLE-US-00001 0 0 0 0 Compound G1 Compound G2 Compound G3 Compound G4 Compound G5 Compound G6 Compound G7 Compound G8 Compound G9 0 Compound G10 Compound G11 Compound G12 Compound G13 Compound G14 Compound G15 Compound G16 Compound G17 Compound G18 Compound G19 00 Compound G20 01 Compound G21 02 Compound G22 03 Compound G23 04 Compound G24 05 Compound G25 06 Compound G26 07 Compound G27 08 Compound G28 09 Compound G29 0 Compound G30 Compound G31 Compound G32 Compound G33 Compound G34 Compound G35 Compound G36 0 0 0 0 0 0 0 0 00 01 02 03 04 05 06 07 08 09 0 0 0 0 0

(62) In one embodiment, the first compound is Formula I.

(63) In one embodiment, the first compound has an evaporation temperature T1 of 150 to 350° C.; wherein the second compound has an evaporation temperature T2 of 150 to 350° C.; wherein the absolute value of T1−T2 is less than 20° C.; wherein the first compound has a concentration C1 in said mixture and a concentration C2 in a film formed by evaporating the mixture in a vacuum deposition tool at a constant pressure between 1×10 Torr to 1×10.sup.−9 Torr, at a 2 Å/sec deposition rate on a surface positioned at a predefined distance away from the mixture being evaporated; and wherein the absolute value of (C1−C2)/C1 is less than 5%.

(64) In one embodiment, the first compound has evaporation temperature T1 of 200 to 350° C. and the second compound has evaporation temperature T2 of 200 to 350° C.

(65) In one embodiment, the absolute value of (C1−C2)/C1 is less than 3%.

(66) In one embodiment, the first compound has a vapor pressure of P1 at T1 at 1 atm, the second compound has a vapor pressure of P2 at T2 at 1 atm; and wherein the ratio of P1/P2 is within the range of 0.90 to 1.10.

(67) In one embodiment, the first compound has a first mass loss rate and the second compound has a second mass loss rate, wherein the ratio between the first mass loss rate and the second mass loss rate is within the range of 0.90 to 1.10. In another embodiment, the first compound has a first mass loss rate and the second compound has a second mass loss rate, wherein the ratio between the first mass loss rate and the second mass loss rate is within the range of 0.95 to 1.05. In another embodiment, the first compound has a first mass loss rate and the second compound has a second mass loss rate, wherein the ratio between the first mass loss rate and the second mass loss rate is within the range of 0.97 to 1.03.

(68) In one embodiment, the first compound and the second compound each has a purity in excess of 99% as determined by high pressure liquid chromatography.

(69) In one embodiment, the composition further comprises a third compound, wherein the third compound has a different chemical structure than the first and second compounds, wherein the third compound has an evaporation temperature T3 of 150 to 350° C., and wherein absolute value of T1−T3 is less than 20° C.

(70) In one embodiment, the composition further comprises a third compound, wherein the third compound has a different chemical structure than the first and second compounds, wherein the third compound has a third mass loss rate and the ratio between the first mass loss rate and third mass loss rate is within the range of 0.90 to 1.10

(71) In one embodiment, the composition is in liquid form at a temperature less than T1 and T2.

(72) In some embodiments, the compound can be an emissive dopant. In some embodiments, the compound can produce emissions via phosphorescence, fluorescence, thermally activated delayed fluorescence, i.e., TADF (also referred to as E-type delayed fluorescence), triplet-triplet annihilation, or combinations of these processes.

(73) Devices of the Invention

(74) According to another aspect of the present disclosure, an OLED is also provided. The OLED includes an anode, a cathode, and an organic layer disposed between the anode and the cathode. The organic layer may include a host and a phosphorescent dopant. The organic layer can include a compound having a formula selected from the group consisting of Formula I and Formula II, and their variations as described herein. The organic layer can also include a composition of materials comprising a first compound, wherein the first compound has a formula selected from the group consisting of Formula I and Formula II.

(75) In some embodiments, the OLED has one or more characteristics selected from the group consisting of being flexible, being rollable, being foldable, being stretchable, and being curved. In some embodiments, the OLED is transparent or semi-transparent. In some embodiments, the OLED further comprises a layer comprising carbon nanotubes.

(76) In some embodiments, the OLED further comprises a layer comprising a delayed fluorescent emitter. In some embodiments, the OLED comprises a RGB pixel arrangement or white plus color filter pixel arrangement. In some embodiments, the OLED is a mobile device, a hand held device, or a wearable device. In some embodiments, the OLED is a display panel having less than 10 inch diagonal or 50 square inch area. In some embodiments, the OLED is a display panel having at least 10 inch diagonal or 50 square inch area. In some embodiments, the OLED is a lighting panel.

(77) In some embodiments, the present invention relates to an emissive region or an emissive layer. The emissive region or emissive layer can include a compound of the present invention. In one embodiment, the compound of the present invention is a host.

(78) The organic layer can also include an emissive dopant. In some embodiments, two or more emissive dopants are preferred. In some embodiments of the emissive region, the emissive region further comprises a phosphorescent emissive dopant. In one embodiment, the emissive dopant is a transition metal complex having at least one ligand or part of the ligand if the ligand is more than bidentate selected from the group consisting of:

(79) ##STR00253## ##STR00254## ##STR00255## wherein each Y.sup.1 to Y.sup.13 are independently selected from the group consisting of carbon and nitrogen; wherein Y′ is selected from the group consisting of BR.sub.e, NR.sub.e, PR.sub.e, O, S, Se, C═O, S═O, SO.sub.2, CR.sub.eR.sub.fRR, SiR.sub.eR.sub.f, and GeR.sub.eR.sub.f; wherein R.sub.e and R.sub.f are optionally fused or joined to form a ring; wherein each R.sub.a, R.sub.b, R.sub.c, and R.sub.d may independently represent from mono substitution to the maximum possible number of substitution, or no substitution; wherein each R.sub.a, R.sub.b, R.sub.c, R.sub.d, R.sub.e, and R.sub.f is independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; and wherein any two adjacent substituents of R.sub.a, R.sub.b, R.sub.c, and R.sub.d are optionally fused or joined to form a ring or form a multidentate ligand.
Additional information on possible emissive dopants is provided below.

(80) The OLED disclosed herein can be incorporated into one or more of a consumer product, an electronic component module, and a lighting panel.

(81) In one embodiment, the consumer product is selected from the group consisting of a flat panel display, a curved display, a computer monitor, a medical monitor, a television, a billboard, a light for interior or exterior illumination and/or signaling, a heads-up display, a fully or partially transparent display, a flexible display, a rollable display, a foldable display, a stretchable display, a laser printer, a telephone, a cell phone, tablet, a phablet, a personal digital assistant (PDA), a wearable device, a laptop computer, a digital camera, a camcorder, a viewfinder, a micro-display that is less than 2 inches diagonal, a 3-D display, a virtual reality or augmented reality display, a vehicle, a video walls comprising multiple displays tiled together, a theater or stadium screen, and a sign.

(82) In one embodiment, the organic layer is an emissive layer and the compound of Formula I or Formula II is a host. In some embodiments the organic layer is a blocking layer and the compound of Formula I or Formula II is a blocking material in the organic layer. In other embodiments the organic layer is a transporting layer and the compound of Formula I or Formula II is a transporting material in the organic layer

(83) In some embodiments, the organic layer further comprises a phosphorescent emissive dopant. In one embodiment, the emissive dopant is a transition metal complex having at least one ligand or part of the ligand if the ligand is more than bidentate selected from the group consisting of:

(84) ##STR00256## ##STR00257## ##STR00258## wherein each Y.sup.1 to Y.sup.13 are independently selected from the group consisting of carbon and nitrogen; wherein Y′ is selected from the group consisting of BR.sub.e, NR.sub.e, PR.sub.e, O, S, Se, C═O, S═O, SO.sub.2, CR.sub.eR.sub.fRR, SiR.sub.eR.sub.f, and GeR.sub.eR.sub.f; wherein R.sub.e and R.sub.f are optionally fused or joined to form a ring; wherein each R.sub.a, R.sub.b, R.sub.c, and R.sub.d may independently represent from mono substitution to the maximum possible number of substitution, or no substitution; wherein each R.sub.a, R.sub.b, R.sub.c, R.sub.d, R.sub.e, and R.sub.f is independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; and wherein any two adjacent substituents of R.sub.a, R.sub.b, R.sub.c, and R.sub.d are optionally fused or joined to form a ring or form a multidentate ligand.

(85) In one embodiment, each R.sub.a, R.sub.b, R.sub.c, R.sub.d, R.sub.e, and R.sub.f is independently selected from the group consisting of hydrogen, deuterium, fluorine, alkyl, cycloalkyl, heteroalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, aryl, heteroaryl, nitrile, isonitrile, and combinations thereof.

(86) According to another aspect, a formulation comprising a composition of materials comprising a first compound described herein is also disclosed.

(87) The emitter dopants can be phosphorescent dopants and/or fluorescent dopants. The organic layer can include a composition of materials comprising a first compound, wherein the first compound has a formula selected from the group consisting of Formula I and Formula II and its variations as described herein as a host.

(88) In yet another aspect of the present disclosure, a formulation that comprises the novel compound disclosed herein is described. The formulation can include one or more components selected from the group consisting of a solvent, a host, a hole injection material, hole transport material, and an electron transport layer material, disclosed herein.

(89) In yet another aspect of the present disclosure, a method for fabricating an organic light emitting device comprising a first electrode, a second electrode, and a first organic layer disposed between the first electrode and the second electrode is also described, wherein the first organic layer comprises a first composition comprising a mixture of a first compound and a second compound, wherein the first compound has a formula selected from the group consisting of Formula I and Formula II, and wherein the second compound has the Formula III. The method may include the steps of providing a substrate having the first electrode disposed thereon, depositing the first composition over the first electrode, and depositing the second electrode over the first organic layer.

(90) In yet another aspect of the present disclosure, a formulation that comprises a compound according to Formula I or Formula II is described. The formulation can include one or more components selected from the group consisting of a solvent, a host, a hole injection material, hole transport material, and an electron transport layer material, disclosed herein.

(91) Combination with Other Materials

(92) 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. For example, 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.

(93) Conductivity Dopants:

(94) A charge transport layer can be doped with conductivity dopants to substantially alter its density of charge carriers, which will in turn alter its conductivity. The conductivity is increased by generating charge carriers in the matrix material, and depending on the type of dopant, a change in the Fermi level of the semiconductor may also be achieved. Hole-transporting layer can be doped by p-type conductivity dopants and n-type conductivity dopants are used in the electron-transporting layer. Non-limiting examples of the conductivity dopants that may be used in an OLED in combination with materials disclosed herein are exemplified below together with references that disclose those materials: EP01617493, EP01968131, EP2020694, EP2684932, US20050139810, US20070160905, US20090167167, US2010288362, WO06081780, WO2009003455, WO2009008277, WO2009011327, WO2014009310, US2007252140. US2015060804 and US2012146012.

(95) ##STR00259## ##STR00260## ##STR00261##

(96) HIL/HTL:

(97) A hole injecting/transporting material to be used in the present invention is not particularly limited, and any compound may be used as long as the compound is typically used as a hole injecting/transporting material. Examples of the material include, but are not limited to: a phthalocyanine or porphyrin derivative; an aromatic amine derivative; an indolocarbazole derivative; a polymer containing fluorohydrocarbon; a polymer with conductivity dopants; a conducting polymer, such as PEDOT/PSS; a self-assembly monomer derived from compounds such as phosphonic acid and silyl derivatives; a metal oxide derivative, such as MoO.sub.x; a p-type semiconducting organic compound, such as 1,4,5,8,9,12-Hexaazatriphenylenehexacarbcmitrile; a metal complex, and a cross-linkable compounds.

(98) Examples of aromatic amine derivatives used in HIL or HTL include, but are not limited to the following general structures:

(99) ##STR00262##

(100) Each of Ar.sup.1 to Ar.sup.9 is selected from the group consisting of aromatic hydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, and azulene; the group consisting of aromatic heterocyclic compounds such as dibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole, indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine; and the group consisting of 2 to 10 cyclic structural units which are groups of the same type or different types selected from the aromatic hydrocarbon cyclic group and the aromatic heterocyclic group and are bonded to each other directly or via at least one of oxygen atom, nitrogen atom, sulfur atom, silicon atom, phosphorus atom, boron atom, chain structural unit and the aliphatic cyclic group. Each Ar may be unsubstituted or may be substituted by a substituent selected from the group consisting of deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.

(101) In one aspect. Ar.sup.1 to Ar.sup.9 is independently selected from the group consisting of:

(102) ##STR00263##
wherein k is an integer from 1 to 20; X.sup.108 to X.sup.108 is C (including CH) or N; Z.sup.101 is NAr.sup.1, O, or S; Ar.sup.1 has the same group defined above.

(103) Examples of metal complexes used in HIL or HTL include, but are not limited to the following general formula:

(104) ##STR00264##
wherein Met is a metal, which can have an atomic weight greater than 40; (Y.sup.101—Y.sup.102) is a bidentate ligand, Y.sup.101 and Y.sup.102 are independently selected from C, N, O, P, and S; L.sup.101 is an ancillary ligand; k′ is an integer value from 1 to the maximum number of ligands that may be attached to the metal; and k′+k″ is the maximum number of ligands that may be attached to the metal.

(105) In one aspect, (Y.sup.101—Y.sup.102) is a 2-phenylpyridine derivative. In another aspect, (Y.sup.101—Y.sup.102) is a carbene ligand. In another aspect, Met is selected from Ir, Pt, Os, and Zn. In a further aspect, the metal complex has a smallest oxidation potential in solution vs. Fc.sup.+/Fc couple less than about 0.6 V.

(106) Non-limiting examples of the HIL and HTL materials that may be used in an OLED in combination with materials disclosed herein are exemplified below together with references that disclose those materials: CN102702075, DE 102012005215, EP01624500, EP01698613, EP01806334, EP01930964, EP01972613, EP01997799, EP02011790, EP02055700, EP02055701, EP1725079, EP2085382, EP2660300, EP650955, JP07-073529, JP2005112765, JP2007091719, JP2008021687, JP2014-009196, KR20110088898, KR20130077473, TW201139402, U.S. Ser. No. 06/517,957, US20020158242, US20030162053, US20050123751, US20060182993, US20060240279, US20070145888, US20070181874, US20070278938, US20080014464, US20080091025, US20080106190, US20080124572, US20080145707, US20080220265, US20080233434, US20080303417, US2008107919, US20090115320, US20090167161, US2009066235, US2011007385, US20110163302, US2011240968, US2011278551, US2012205642, US2013241401, US20140117329, US2014183517, U.S. Pat. Nos. 5,061,569, 5,639,914, WO05075451, WO07125714, WO08023550, WO08023759, WO2009145016, WO2010061824, WO2011075644, WO2012177006, WO2013018530, WO2013039073, WO2013087142, WO2013118812, WO2013120577, WO2013157367, WO2013175747, WO2014002873, WO2014015935, WO2014015937, WO2014030872, WO2014030921, WO2014034791, WO2014104514, WO2014157018.

(107) ##STR00265## ##STR00266## ##STR00267## ##STR00268## ##STR00269## ##STR00270## ##STR00271## ##STR00272## ##STR00273## ##STR00274## ##STR00275## ##STR00276## ##STR00277## ##STR00278## ##STR00279## ##STR00280##

(108) EBL:

(109) An electron blocking layer (EBL) may be used to reduce the number of electrons and/or excitons that leave the emissive layer. The presence of such a blocking layer in a device may result in substantially higher efficiencies, and or longer lifetime, as compared to a similar device lacking a blocking layer. Also, a blocking layer may be used to confine emission to a desired region of an OLED. In some embodiments, the EBL material has a higher LUMO (closer to the vacuum level) and/or higher triplet energy than the emitter closest to the EBL interface. In some embodiments, the EBL material has a higher LUMO (closer to the vacuum level) and or higher triplet energy than one or more of the hosts closest to the EBL interface. In one aspect, the compound used in EBL contains the same molecule or the same functional groups used as one of the hosts described below.

(110) Additional Hosts:

(111) The light emitting layer of the organic EL device of the present invention preferably contains at least a metal complex as light emitting material, and may contain a host material using the metal complex as a dopant material. Examples of the host material are not particularly limited, and any metal complexes or organic compounds may be used as long as the triplet energy of the host is larger than that of the dopant. Any host material may be used with any dopant so long as the triplet criteria is satisfied.

(112) Examples of metal complexes used as host are preferred to have the following general formula:

(113) ##STR00281##
wherein Met is a metal; (Y.sup.103—Y.sup.104) is a bidentate ligand, Y.sup.101 and Y.sup.104 are independently selected from C, N, O, P, and S; L.sup.101 is an another ligand; k′ is an integer value from 1 to the maximum number of ligands that may be attached to the metal; and k′+k″ is the maximum number of ligands that may be attached to the metal.

(114) In one aspect, the metal complexes are:

(115) ##STR00282##
wherein (O—N) is a bidentate ligand, having metal coordinated to atoms O and N.

(116) In another aspect. Met is selected from Ir and Pt. In a further aspect, (Y.sup.103—Y.sup.104) is a carbene ligand.

(117) Examples of other organic compounds used as additional host are selected from the group consisting of aromatic hydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl, triphenylene, tetraphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, and azulene; the group consisting of aromatic heterocyclic compounds such as dibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole, indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine; and the group consisting of 2 to 10 cyclic structural units which are groups of the same type or different types selected from the aromatic hydrocarbon cyclic group and the aromatic heterocyclic group and are bonded to each other directly or via at least one of oxygen atom, nitrogen atom, sulfur atom, silicon atom, phosphorus atom, boron atom, chain structural unit and the aliphatic cyclic group. Each option within each may be unsubstituted or may be substituted by a substituent selected from the group consisting of deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.

(118) In one aspect, the host compound contains at least one of the following groups in the molecule:

(119) ##STR00283## ##STR00284##
wherein each of R.sup.101 to R.sup.107 is independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof, and when it is aryl or heteroaryl, it has the similar definition as Ar's mentioned above. k is an integer from 0 to 20 or 1 to 20; k′″ is an integer from 0 to 20. X.sup.101 to X.sup.108 is selected from C (including CH) or N.

(120) Z.sup.101 and Z.sup.102 is selected from NR.sup.101, O, or S.

(121) Non-limiting examples of additional host materials that may be used in an OLED in combination with the materials disclosed herein are exemplified below together with references that disclose those materials: EP2034538, EP2034538A, EP2757608, JP2007254297, KR20100079458, KR20120088644, KR20120129733, KR20130115564, TW201329200, US20030175553, US20050238919, US20060280965, US20090017330, US20090030202, US20090167162, US20090302743, US20090309488, US20100012931, US20100084966, US20100187984, US2010187984, US2012075273, US2012126221, US2013009543, US2013105787, US2013175519, US2014001446, US20140183503, US20140225088, US2014034914, U.S. Pat. No. 7,154,114, WO2001039234, WO2004093207, WO2005014551, WO2005089025, WO2006072002, WO2006114966, WO2007063754, WO2008056746, WO2009003898, WO2009021126, WO2009063833, WO2009066778, WO2009066779, WO2009086028, WO2010056066, WO2010107244, WO2011081423, WO2011081431, WO2011086863, WO2012128298, WO2012133644, WO2012133649, WO2013024872, WO2013035275, WO2013081315, WO2013191404, WO2014142472.

(122) ##STR00285## ##STR00286## ##STR00287## ##STR00288## ##STR00289## ##STR00290## ##STR00291## ##STR00292## ##STR00293## ##STR00294## ##STR00295## ##STR00296##

(123) Emitter:

(124) An emitter dopant is not particularly limited, and any compounds may be used as long as the compounds are typically used as emitter materials. Examples of suitable emitter materials include, but are not limited to, compounds which can produce emissions via phosphorescence, fluorescence, thermally activated delayed fluorescence, i.e., TADF (also referred to as E-type delayed fluorescence), triplet-triplet annihilation, or combinations of these processes.

(125) Non-limiting examples of the emitter materials that may be used in an OLED in combination with materials disclosed herein are exemplified below together with references that disclose those materials: CN103694277, CN1696137, EB01238981, EP01239526, EP01961743, EP1239526, EP1244155, EP1642951, EP1647554, EP1841834, EP1841834B, EP2062907, EP2730583, JP2012074444, JP2013110263, JP4478555, KR1020090133652, KR20120032054, KR20130043460, TW201332980, U.S. Ser. No. 06/699,599, U.S. Ser. No. 06/916,554, US20010019782, US20020034656, US20030068526, US20030072964. US20030138657, US20050123788, US20050244673, US2005123791, US2005260449, US20060008670, US20060065890, US20060127696, US20060134459, US20060134462, US20060202194, US20060251923, US20070034863, US20070087321, US20070103060, US20070111026. US20070190359, US20070231600, US2007034863, US2007104979, US2007104980, US2007138437, US2007224450, US2007278936. US20080020237, US20080233410, US20080261076, US20080297033. US200805851, US2008161567. US2008210930, US20090039776, US20090108737, US20090115322, US20090179555, US2009085476, US2009104472, US20100090591, US20100148663, US20100244004, US20100295032, US2010102716, US2010105902, US2010244004, US2010270916, US20110057559, US20110108822, US20110204333, US2011215710, US2011227049, US2011285275, US2012292601, US20130146848, US2013033172, US2013165653, US2013181190, US2013334521, US20140246656, US2014103305, U.S. Pat. Nos. 6,303,238, 6,413,656, 6,653,654, 6,670,645, 6,687,266, 6,835,469, 6,921,915, 7,279,704, 7,332,232, 7,378,162, 7,534,505, 7,675,228, 7,728,137, 7,740,957, 7,759,489, 7,951,947, 8,067,099, 8,592,586, 8,871,361, WO06081973, WO06121811, WO07018067, WO07108362, WO07115970. WO07115981, WO08035571, WO2002015645, WO2003040257, WO2005019373 WO2006056418. WO2008054584, WO2008078800, WO2008096609, WO2008101842, WO2009000673, WO2009050281, WO2009100991, WO2010028151, WO2010054731, WO2010086089, WO2010118029, WO2011044988, WO2011051404, WO2011107491, WO2012020327, WO2012163471, WO2013094620, WO2013107487, WO2013174471, WO2014007565, WO2014008982, WO2014023377, WO2014024131, WO2014031977, WO2014038456, WO2014112450.

(126) ##STR00297## ##STR00298## ##STR00299## ##STR00300## ##STR00301## ##STR00302## ##STR00303## ##STR00304## ##STR00305## ##STR00306## ##STR00307## ##STR00308## ##STR00309## ##STR00310## ##STR00311## ##STR00312## ##STR00313## ##STR00314## ##STR00315## ##STR00316## ##STR00317## ##STR00318##

(127) A hole blocking layer (HBL) may be used to reduce the number of holes and/or excitons that leave the emissive layer. The presence of such a blocking layer in a device may result in substantially higher efficiencies and/or longer lifetime as compared to a similar device lacking a blocking layer. Also, a blocking layer may be used to confine emission to a desired region of an OLED. In some embodiments, the HBL material has a lower HOMO (further from the vacuum level) and or higher triplet energy than the emitter closest to the HBL interface. In some embodiments, the HBL material has a lower HOMO (further from the vacuum level) and or higher triplet energy than one or more of the hosts closest to the HBL interface.

(128) In one aspect, compound used in HBL contains the same molecule or the same functional groups used as host described above.

(129) In another aspect, compound used in HBL contains at least one of the following groups in the molecule:

(130) ##STR00319##
wherein k is an integer from 1 to 20; L.sup.101 is an another ligand. k′ is an integer from 1 to 3.

(131) ETL:

(132) Electron transport layer (ETL) may include a material capable of transporting electrons. Electron transport layer may be intrinsic (undoped), or doped. Doping may be used to enhance conductivity. Examples of the ETL material are not particularly limited, and any metal complexes or organic compounds may be used as long as they are typically used to transport electrons.

(133) In one aspect, compound used in ETL contains at least one of the following groups in the molecule:

(134) ##STR00320##
wherein R.sup.101 is selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof, when it is aryl or heteroaryl, it has the similar definition as Ar's mentioned above. Ar.sup.1 to Ar.sup.3 has the similar definition as Ar's mentioned above. k is an integer from 1 to 20. X.sup.101 to X.sup.108 is selected from C (including CH) or N.

(135) In another aspect, the metal complexes used in ETL contain, but are not limited to the following general formula:

(136) ##STR00321##
wherein (O—N) or (N—N) is a bidentate ligand, having metal coordinated to atoms O, N or N, N; L.sup.101 is another ligand; k′ is an integer value from 1 to the maximum number of ligands that may be attached to the metal.

(137) Non-limiting examples of the ETL materials that may be used in an OLED in combination with materials disclosed herein are exemplified below together with references that disclose those materials: CN103508940, EP01602648. EP01734038, EP01956007, JP2004-022334, JP2005149918, JP2005-268199, KR0117693, KR20130108183, US20040036077, US20070104977, US2007018155, US20090101870. US20090115316, US20090140637, US20090179554, US2009218940, US2010108990, US2011156017, US2011210320, US2012193612, US2012214993, US2014014925, US2014014927, US20140284580, U.S. Pat. Nos. 6,656,612, 8,415,031, WO2003060956, WO2007111263, WO2009148269, WO2010067894, WO2010072300, WO2011074770, WO2011105373, WO2013079217, WO2013145667, WO2013180376, WO2014104499, WO2014104535.

(138) ##STR00322## ##STR00323## ##STR00324## ##STR00325## ##STR00326## ##STR00327## ##STR00328## ##STR00329## ##STR00330##

(139) Charge Generation Layer (CGL):

(140) In tandem or stacked OLEDs, the CGL plays an essential role in the performance, which is composed of an n-doped layer and a p-doped layer for injection of electrons and holes, respectively. Electrons and holes are supplied from the CGL and electrodes. The consumed electrons and holes in the CGL are refilled by the electrons and holes injected from the cathode and anode, respectively; then, the bipolar currents reach a steady state gradually. Typical CGL materials include n and p conductivity dopants used in the transport layers.

(141) In any above-mentioned compounds used in each layer of the OLED device, the hydrogen atoms can be partially or fully deuterated. Thus, any specifically listed substituent, such as, without limitation, methyl, phenyl, pyridyl, etc. may be undeuterated, partially deuterated, and fully deuterated versions thereof. Similarly, classes of substituents such as, without limitation, alkyl, aryl, cycloalkyl, heteroaryl, etc. also may be undeuterated, partially deuterated, and fully deuterated versions thereof.

(142) Experimental

(143) Materials Synthesis

(144) Chemical abbreviations used throughout this document are as follows: Pd.sub.2(dba).sub.3 is tri(dibenzylideneacetone) dipalladium(0), and SPhos is dicyclohexyl(2′,6′-dimethoxy-[1,1′-biphenyl]-2-yl)phosphine.

(145) Synthesis of Compound A2

(146) ##STR00331##

(147) A mixture solution of 5-([1,1′-biphenyl]-4-yl)-5,8-dihydroindolo[2,3-c]carbazole (2 g, 4.90 mmol), 4-bromo-1,1′:4′,1″-terphenyl (1.817 g, 5.88 mmol), Pd.sub.2(dba) (0.224 g, 0.245 mmol), SPhos (0.201 g, 0.490 mmol) and tert-BuONa (1.18 g, 12.24 mmol) in xylene (80 ml) was refluxed under nitrogen for 16 h. The hot reaction mixture was filtered through a short plug of silica gel. Upon evaporation of the solvent, the residue was recrystallized from toluene and triturated with ethyl acetate to yield Compound A2 (1.84 g, 59%) as a white solid.

(148) Synthesis of Compound B2

(149) ##STR00332##

(150) The procedure for the synthesis of Compound A2 was followed to synthesize Compound B2 from 5-([1,1′-biphenyl]-4-yl)-5,8-dihydroindolo[2,3-c]carbazole and 3-bromo-1,1′:4′,1″-terphenyl. Compound B2 was synthesized as a white solid in a yield of 85%.

(151) Synthesis of Compound D7

(152) ##STR00333##

(153) The procedure for the synthesis of Compound A2 was followed to synthesize Compound D7 from 5-([1,1′:4′,1″-terphenyl]-3-yl)-5,12-dihydroindolo[3,2-a]carbazole and 2-bromo-9,9-dimethyl-9H-fluorene. Compound D7 was synthesized as a white solid in a yield of 50%.

(154) Application in OLED.

(155) All devices were fabricated by high vacuum (˜10.sup.−7 Torr) thermal evaporation. The anode electrode was 80 nm of indium tin oxide (ITO). The cathode electrode consisted of 1 nm of LiQ followed by 100 nm of A1. All devices were encapsulated with a glass lid sealed with an epoxy resin in a nitrogen glove box (<1 ppm of H.sub.2O and O.sub.2) immediately after fabrication, and a moisture getter was incorporated inside the package.

(156) Device Examples

(157) A set of device examples have organic stacks consisting of, sequentially from the ITO surface, 10 nm of LG101 (from LG Chem) as the hole injection layer (HIL), 45 nm of PPh-TPD as the hole-transport layer (HTL), 40 nm of emissive layer (EML), 35 nm of compound EH-1 as the hole-blocking layer (HBL), followed by 35 nm of aDBT-ADN with 35 wt % LiQ as the electron-transport layer (ETL). The EML has two components: 90 wt % of the EML being the invented compounds (Compound A2 or Compound D7) or comparative compound (CC-1 or CC-2) as the host and 10 wt % of the EML being compound GD as the emitter. The chemical structures of the compounds used are shown below:

(158) ##STR00334## ##STR00335##

(159) Provided in Table D1 below is a summary of the device data, emission color, power efficiency (PE) and relative lifetime LT97, recorded at 1000 nits for device examples. The relative lifetime LT80 (in arbitrary unit. A. U.), defined as the time it takes for a device to decay to 80% of its original luminescence under a constant operation current density that provides an initial luminescence of 1000 nits, is calculated from the measured value recorded at 40 mA/cm.sup.2, assuming an acceleration factor of 1.8, and is normalized to that of Device C-1.

(160) TABLE-US-00002 TABLE D1 EML Emission PE LT80 Device ID Host Emitter Color [lm/W] [A.U.] Device 1 Compound A2 GD Green 41.2 177 Device C-1 CC-1 GD Green 40.6 100 Device 2 Compound D7 GD Green 17.7 246 Device C-2 CC-2 GD Green 12.0 93

(161) The device data in Table D1 shows that the inventive Compounds A2 and D7 produce longer lifetime, while maintaining equivalent or higher efficiency, than their corresponding comparative compounds CC-1 and CC-2, respectively. The enhanced performance of inventive compounds might be attributable to the extended conjugation of the terphenyl moiety than the biphenyl moiety, which could improve charge transport properties of the inventive compounds.

(162) Provided in Table PM below is a summary of the compatibility of selected h- and e-hosts was evaluated by compositional analysis of films fabricated by single-source co-evaporation of the premixture of these two components. A first set of potential premixtures of selected h- and e-hosts are presented in Table PM.

(163) TABLE-US-00003 TABLE PM Potential premixtures comprising selected h- and e-hosts Premixtures e-hosts h-hosts PM-1 Compound F5 Compound B2 PM-2 Compound F5 Compound A3 PM-3 Compound F11 Compound C2 PM-4 Compound F11 Compound B15 PM-5 Compound F14 Compound A9 PM-6 Compound F14 Compound A38 PM-7 Compound F14 Compound B22 PM-8 Compound F17 Compound A3 PM-9 Compound F17 Compound B2 PM-10 Compound F17 Compound C5 PM-11 Compound H74 Compound A35 PM-12 Compound H74 Compound D1 PM-13 Compound H83 Compound B2 PM-14 Compound H83 Compound A3 PM-15 Compound H248 Compound E14 PM-16 Compound M2 Compound C1 PM-17 Compound M5 Compound D6 PM-18 Compound G9 Compound B2 PM-19 Compound M101 Compound B5 PM-20 Compound G0 Compound B2

(164) Premixture PM-1:

(165) Compound F5 and Compound B2 were provided at a weight ratio of 1:1, physically mixed, grinded and loaded into an evaporation source. The premixed compositions were thermally co-evaporated at a rate of 2 Å/s in a vacuum chamber under a pressure less than 10.sup.−7 Torr. and deposited onto glass substrates. The substrates were replaced continuously after deposition of 500 Å of film without stopping the deposition and cooling the source. The compositions of films were analyzed by high-performance liquid chromatography (HPLC) and the results are shown in Table 1.

(166) TABLE-US-00004 TABLE 1 HPLC composition (%) of sequentially deposited films form a premixture (PM-1) comprising Compound F5 and Compound B2 with weight ratio 1:1. HPLC Conditions: C18 reverse column, 100% acetonitrile as mobile phase, detection wavelength wavelength 254 nm. Due to different absorption coefficients, the HPLC composition may or may not agree with the weight ratio. F5 B2 Plate1 55.7 44.3 Plate2 56.1 43.9 Plate3 52.2 47.8 Plate4 46.5 53.5

(167) Premixture PM-9:

(168) Premixture PM-9 comprising Compound F17 and Compound B2 were evaluated in the same way as premixture PM-1, except that a weight ratio of 1:1 for Compound F17 and Compound B2 was used, and the results are presented in Table 2.

(169) TABLE-US-00005 TABLE 2 HPLC composition (%) of sequentially deposited films from Premixture PM-9 comprising Compound E17 and Compound B2 with weight ratio 1:1. HPLC Conditions: C18 reverse column, 100% acetonitrile as mobile phase, detection wavelength wavelength 254 nm. Due to different absorption coefficients, the HPLC composition may or may not agree with the weight ratio. F17 B2 Plate1 58.7 41.3 Plate2 60.7 39.3 Plate3 62.1 37.9 Plate4 63.4 36.6 Plate5 64.8 35.2

(170) Premixture PM-13:

(171) Premixture PM-13 comprising Compound H83 and Compound B2 were evaluated in the same way as premixture PM-9, and the results are presented in Table 3.

(172) TABLE-US-00006 TABLE 3 HPLC composition (%) of sequentially deposited films from Premixture PM-13 comprising Compound H83 and Compound B2 with weight ratio 1:1. HPLC Conditions: C18 reverse column, 100% acetonitrile as mobile phase, detection wavelength wavelength 254 nm. Due to different absorption coefficients, the HPLC composition may or may not agree with the weight ratio. H83 B2 Plate1 53.4 46.6 Plate2 55.0 45.0 Plate3 55.6 44.4

(173) Premixtures PM-18, PM-19, and PM-20:

(174) Each pair of premixable h-host and e-host at a weight ratio of 1:1 or 1:3 was physically mixed, grinded, and loaded into an evaporation source. The total weight of the mixture was 0.4 g. The premixed components were thermally co-evaporated at a rate of 2 Å/s in a vacuum chamber under a pressure less than 10.sup.−7 Torr until depletion, and deposited onto glass substrates. The substrates were replaced continuously after deposition of 400 Å of film without stopping the deposition and cooling the source. The compositions of the films were analyzed by high-performance liquid chromatography (HPLC) and the results are shown in Table 4.

(175) TABLE-US-00007 TABLE 4 Experimental HPLC data on Premixability for Premixtures PM-18, PM-19, and PM-20 Ratio in H-Host/E-host ratio in deposited films [%] Premixture mixture 1 2 3 4 5 6 7 8 9 PM-18 H-Host B2 1 39.2 38.0 36.8 35.8 35.5 35.7 35.7 35.9 35.7 E-host G9 1 60.8 62.0 63.2 64.2 64.5 64.3 64.3 64.1 64.3 PM-19 H-Host B5 1 51.9 50.7 50.1 50.3 50.2 49.9 50.3 50.4 E-host M101 1 48.1 49.3 49.9 49.7 49.8 50.1 49.7 49.6 PM-20 H-Host B2 3 73.9 72.7 70.7 69.2 68.8 69.9 70.9 E-host G10 1 26.1 27.3 29.3 30.8 31.2 30.1 29.1

(176) The data in Tables 1, 2, 3, and 4 show that the ratio of the two components in premixtures PM-1, PM-9, PM-13, PM-18, PM-19, and PM-20 does not change significantly over a continuous single-source coevaporation. The minor fluctuations in the concentrations do not reveal any trend and can be explained by the accuracy of HPLC analysis. Normally, the change of the concentration before and after depositions within 5% throughout the process is considered to be good and useful for commercial OLED application. These experiments conclude that PM-1, PM-9 and PM-13 are stable premixtures for coevaporation. The coevaporation stability of these premixtures is believed to tracable to the unique chemical structures associated with these two classes of materials.

(177) It is understood that the various embodiments described herein are by way of example only, and are not intended to limit the scope of the invention. For example, many of the materials and structures described herein may be substituted with other materials and structures without deviating from the spirit of the invention. The present invention as claimed may therefore include variations from the particular examples and preferred embodiments described herein, as will be apparent to one of skill in the art. It is understood that various theories as to why the invention works are not intended to be limiting.