Phosphorescence-sensitized delayed fluorescence light emitting system

Abstract

Disclosed is a device that includes an emissive material or region including a host that is doped with a first material as an emitter that is an acceptor and a phosphorescent-capable second material as a sensitizer. The first material and the second material each has a first singlet state and a first triplet state. The first triplet state of the second material is not lower than the first triplet state of the first material. The second material transfers excitons to the first material and the excitons that transition to the first triplet state of the first material can be activated to the first singlet state of the first material through a thermal activation process.

Claims

1. A device comprising: an emissive layer, said emissive layer comprising: a host material doped with a first material as an emitter that is an acceptor and a phosphorescent-capable second material as a sensitizer; wherein the first material and the second material each has a first singlet state and a first triplet state; wherein the first triplet state of the second material is not lower than the first triplet state of the first material; wherein, in operational state at room temperature, the second material transfers excitons to the first singlet state and the triplet state of the first material; and wherein the excitons that are transferred to the first triplet state of the first material are activated to the first singlet state of the first material through a thermal activation process.

2. The device of claim 1, wherein the first material has an energy gap of not more than 100 meV between the first singlet state and the first triplet state in the first material.

3. The device of claim 1, wherein the first material comprises a material that exhibits E-type delayed fluorescence.

4. The device of claim 1, wherein the second material comprises a material having an emission spectrum that at least partially overlaps with an absorption spectrum of the first material.

5. The device of claim 1, wherein the first material comprises a donor-acceptor type material.

6. The device of claim 1, wherein each of the first material and the second material is a dopant in a region of the emissive layer.

7. The device of claim 1, wherein the second material 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: ##STR00187## ##STR00188## wherein R.sub.a, R.sub.b, R.sub.c, and R.sub.d may represent mono, di, tri, or tetra substitution, or no substitution; wherein R.sub.a, R.sub.b, R.sub.c, and R.sub.d are 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 two adjacent substituents of R.sub.a, R.sub.b, R.sub.c, and R.sub.d are optionally joined to form a fused ring or form a multidentate ligand.

8. An emissive layer in a device, said emissive layer comprising: a host material doped with a first material as an emitter that is an acceptor and a phosphorescent-capable second material as a sensitizer; wherein the first material and the second material each has a first singlet state and a first triplet state; wherein the first triplet state of the second material is not lower than the first triplet state of the first material; wherein, in operational state at room temperature, the second material transfers excitons to the first singlet state and the first triplet state of the first material; and wherein the excitons that are transferred to the first triplet state of the first material are activated to the first singlet state of the first material through a thermal activation process.

9. The emissive layer of claim 8, wherein the first material has an energy gap of not more than 100 meV between the first singlet state and the first triplet state.

10. The emissive layer of claim 8, wherein the first material has an energy gap of not more than 80 meV between the first singlet state and the first triplet state.

11. The emissive layer of claim 8, wherein the first material comprises a material that exhibits E-type delayed fluorescence.

12. The emissive layer of claim 8, wherein the second material comprises a material having an emission spectrum that at least partially overlaps with an absorption spectrum of the first material.

13. The emissive layer of claim 8, wherein the first material comprises a donor-acceptor type material.

14. The emissive layer of claim 8, wherein each of the first material and the second material is a dopant in a region of the emissive layer.

15. The emissive layer of claim 8, wherein the second material 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: ##STR00189## ##STR00190## ##STR00191## wherein R.sub.a, R.sub.b, R.sub.c, and R.sub.d may represent mono, di, tri, or tetra substitution, or no substitution; wherein R.sub.a, R.sub.b, R.sub.c, and R.sub.d are 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 two adjacent substituents of R.sub.a, R.sub.b, R.sub.c, and R.sub.d are optionally joined to form a fused ring or form a multidentate ligand.

16. A consumer product comprising a device that comprises an emissive layer, said emissive layer comprising: a host material doped with a first material as an emitter that is an acceptor and a phosphorescent-capable second material as a sensitizer; wherein the first material and the second material each has a first singlet state and a first triplet state; wherein the first triplet state of the second material is not lower than the first triplet state of the first material; wherein, in operational state at room temperature, the second material transfers excitons to the first singlet state and the first triplet state of the first material; and wherein the excitons that are transferred to the first triplet state of the first material are activated to the first singlet state of the first material through a thermal activation process.

17. The consumer product of claim 16, wherein the first material comprises a material that exhibits E-type delayed fluorescence.

18. The consumer product of claim 16, wherein the second material comprises a material having an emission spectrum that at least partially overlaps with an absorption spectrum of the first material.

19. The consumer product of claim 16, wherein the first material comprises a donor-acceptor type material.

20. The consumer product of claim 16, wherein the consumer product is one of flat panel displays, computer monitors, medical 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, viewfinders, micro-displays, vehicles, wall screens, theater screens, stadium screens, and signs.

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.

(3) FIG. 3 shows an example energy diagram for a sensitizer-acceptor system.

(4) FIG. 4 shows an example energy diagram for a sensitizer-acceptor system having a material with a relatively small energy gap according to an embodiment.

DETAILED DESCRIPTION

(5) 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.

(6) 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.

(7) 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”), which 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.

(8) 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.

(9) 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.

(10) 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.

(11) 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.

(12) 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.

(13) 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. patent application Ser. No. 10/233,470, which is incorporated by reference in its entirety. Other suitable deposition methods include spin coating and other solution based processes. Solution based processes are preferably carried out 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 OVID. 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.

(14) 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.

(15) 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, medical 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, viewfinders, micro-displays, vehicles, a large area wall, theater or stadium screen, or 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.).

(16) 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.

(17) The terms halo, halogen, alkyl, cycloalkyl, alkenyl, alkynyl, arylkyl, heterocyclic group, aryl, aromatic group, and heteroaryl are known to the art, and are defined in U.S. Pat. No. 7,279,704 at cols. 31-32, which are incorporated herein by reference.

(18) It has been found that some emissive layers, materials, and devices may have relatively short operational lifetimes, especially where relatively high energies and relatively long transient times are involved. For example, blue phosphorescent OLEDs (PHOLEDs) may have relatively short operational lifetimes.

(19) Embodiments of the invention as disclosed herein may address these issues to improve the operational lifetime of a layer or device by providing physical arrangements that allow for transfer of triplet excitons in the layer to single excitons, thus reducing the chance of degradation without negatively affecting exciton utilization. For example, in an embodiment triplet excitons in a PHOLED may be transferred to singlet excitons in a fluorescent material within the device. Such arrangements may be accomplished, for example, by using a phosphorescent-sensitized system. In an embodiment, it may be desirable to have a relatively small energy gap, such as 100 meV (milli-electron volts) or less, between the first singlet state and the first triplet state within a sensitized fluorescent material.

(20) FIG. 3 shows an example energy level diagram for a sensitizer-acceptor system, in which a phosphorescent sensitizer is used to sensitize a fluorescent acceptor. In this system, the quantum efficiency of a device that includes the doped region may be reduced because non-radiation triplet sites in the fluorescent material may act as quenching sites in the acceptor material. The related, non-preferred T.sub.1 to S.sub.0 transition in the acceptor is shown by the dotted transition in FIG. 3.

(21) More specifically, in the system excitons may transition from the S.sub.1 to T.sub.1 state in the sensitizer material through intersystem crossing, as will be readily understood by one of skill in the art. Excitons may then transfer to the S.sub.1 state in the acceptor via Forster transfer, or the T.sub.1 state via Dexter transfer. T.sub.1 excitons in the acceptor typically will undergo a non-radiative transition to the S.sub.0 state. While this may decrease the phosphorescent transient lifetime, it necessarily also results in photon loss within the region.

(22) In an embodiment of the invention as disclosed herein, arrangements with a relatively small energy gap between the S.sub.1 and T.sub.1 states in the acceptor, such as 100 meV or less, may be used. In some embodiments, an energy gap of 0100 meV, 80 meV, 60 meV, 50 meV, 40 meV, 35 meV, or less may be preferred. In such an arrangement, excitons that transition to the T.sub.1 state of the acceptor can be activated to the S.sub.1 state due to the relatively small energy gap. This thermal activation process is fast enough that non-radiative decay from the T.sub.1 state to the S.sub.0 state is minimal or negligible, thus allowing for sensitization up to and including 100%. The relatively high level of sensitization may allow for direct emission from the PHOLED to be reduced or eliminated relative to conventional sensitized devices. In addition, PHOLEDs according to embodiments disclosed herein may make use of conventional structures and materials regardless of energy level, other than the specific energy levels and structural differences disclosed herein.

(23) FIG. 4 shows an example energy level diagram in a sensitizer-acceptor system according to an embodiment of the invention disclosed herein. As shown, the same transitions between a sensitizer and an acceptor material may occur as discussed with respect to FIG. 3. However, the acceptor material includes a relatively small energy gap AE between the S.sub.1 and T.sub.1 states, preferably not more than about 100 meV, more preferably not more than 80 meV, more preferably not more than 60 meV, more preferably not more than 35-40 meV. Non-radiative transition from the T.sub.1 state to the S.sub.0 state is reduced; instead, excitons are more likely to transition to the S.sub.1 state in the acceptor, allowing for increased sensitization and improved operation relative to the system illustrated in FIG. 3, without significant PHOLED degradation.

(24) In an embodiment, Cu(I) complexes may be used as an acceptor in a sensitizer-acceptor system. Such complexes may exhibit relatively pronounced thermally-activated delay fluorescence of the lowest excited singlet state at temperatures within or comparable to ambient. That is, such materials typically may have a relatively small energy gap between S.sub.1 and T.sub.1 states, preferably 100 meV or less as previously disclosed.

(25) Specific materials suitable for use as acceptors in embodiments disclosed herein include the following non-limiting examples:

(26) ##STR00002## ##STR00003## ##STR00004##

(27) Specific materials suitable for use as sensitizer materials in embodiments disclosed herein include the following non-limiting examples:

(28) ##STR00005## ##STR00006##

(29) An organic light emitting device is also provided. The device may include an anode, a cathode, and an organic emissive layer disposed between the anode and the cathode. The organic emissive layer may include a host and a phosphorescent dopant. The device may also include a layer or region that includes a sensitizer-acceptor system as disclosed herein. More specifically, the device may include a region having a sensitizer material and an acceptor material, where the acceptor material has an energy gap of not more than about 100 meV between the S.sub.1 and T.sub.1 states as previously described. The device may include one or more such regions or layers. The particular emissive materials included in the region otherwise may be selected such that the device emits light at a desired wavelength, as will be understood by one of skill in the art. Devices that incorporate the layers and regions disclosed herein may include full-color displays, portable devices, and other emissive devices. The sensitizer material and the acceptor material may be provided as dopants in one or more host materials. Each of the sensitizer and acceptor material may be provided as a dopant in a separate host material, or each may be provided as a dopant of the same host material and/or within the same region. Alternatively, the sensitizer material may be doped with the acceptor material.

(30) As used herein, a material may be described as a “phosphorescent” or “phosphorescent capable” material to indicate that the material generally is capable of emitting from the triplet state. In a given device, a phosphorescent capable material may emit from the triplet state, or may transfer energy from the triplet state to another material, state, layer, energy level, or the like, depending upon the particular materials and physical configurations used, as will be understood by one of skill in the art.

(31) In an embodiment, an emissive layer may include two materials, such as where the emissive layer is doped with both materials. The first material, typically a fluorescent acceptor material, may have a relatively small energy gap between the first singlet state and the first triplet state. The energy gap may be not more than about 100 meV, more preferably not more than about 80 meV, more preferably not more than about 60 meV, more preferably not more than about 35-40 meV. The second material, typically a sensitizer, may be a phosphorescent-capable material that transfers energy to the first material. Energy may be transferred, for example, via exciton energy transfer from an excited state in the second material to an excited state in the first material. Specific examples of energy transfer include Forster and Dexter transfers. In some cases, the emission spectrum of the second material may overlap or partially overlap an absorption spectrum of the first material.

(32) In an embodiment, the first material may be a fluorescent material, such as a material that exhibits E-type delayed fluorescence. Specific examples of suitable fluorescent materials include metal complexes, specifically Cu complexes, and organic compounds such as donor-acceptor type materials. In an embodiment, the second material may include a transition metal complex having at least one ligand or part of the ligand if the ligand is more than bidentate, and may include one or more of the following:

(33) ##STR00007## ##STR00008## ##STR00009##
where R.sub.a, R.sub.b, R.sub.c, and R.sub.d may represent mono, di, tri, or tetra substitution, or no substitution, and R.sub.a, R.sub.b, R.sub.c, and R.sub.d are independently selected from the following: 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 where two adjacent substituents of R.sub.a, R.sub.b, R.sub.c, and R.sub.d may be joined to form a fused ring or form a multidentate ligand.

(34) In general, the layers and regions disclosed herein may be fabricated by depositing one layer on another over a substrate, as previously described, such as in reference to FIGS. 1 and 2. For example, a cathode, an emissive layer including a sensitizer-acceptor system as described, and an anode may be deposited in a stack over a substrate. The layers may be deposited using any suitable technique, as previously described.

(35) Combination with Other Materials

(36) 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.

(37) HIL/HTL:

(38) 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 not limit to: a phthalocyanine or porphryin 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 silane derivatives; a metal oxide derivative, such as MoO.sub.x; a p-type semiconducting organic compound, such as 1,4,5,8,9,12-Hexaazatriphenylenehexacarbonitrile; a metal complex, and a cross-linkable compounds.

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

(40) ##STR00010##

(41) Each of Ar.sup.1 to Ar.sup.9 is selected from the group consisting aromatic hydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, azulene; group consisting 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 group consisting 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. Wherein each Ar is further substituted by a substituent 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.

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

(43) ##STR00011##

(44) k is an integer from 1 to 20; X.sup.1 to X.sup.8 is C (including CH) or N; Ar.sup.1 has the same group defined above.

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

(46) ##STR00012##

(47) M is a metal, having an atomic weight greater than 40; (Y.sup.1-Y.sup.2) is a bidentate ligand, Y.sup.1 and Y.sup.2 are independently selected from C, N, O, P, and S; L is an ancillary ligand; m is an integer value from 1 to the maximum number of ligands that may be attached to the metal; and m+n is the maximum number of ligands that may be attached to the metal.

(48) In one aspect, (Y.sup.1-Y.sup.2) is a 2-phenylpyridine derivative.

(49) In another aspect, (Y.sup.1-Y.sup.2) is a carbene ligand.

(50) In another aspect, M is selected from Ir, Pt, Os, and Zn.

(51) 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.

(52) Host:

(53) 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. While the Table below categorizes host materials as preferred for devices that emit various colors, any host material may be used with any dopant so long as the triplet criteria is satisfied.

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

(55) ##STR00013##

(56) M is a metal; (Y.sup.3-Y.sup.4) is a bidentate ligand, Y.sup.3 and Y.sup.4 are independently selected from C, N, O, P, and S; L is an ancillary ligand; m is an integer value from 1 to the maximum number of ligands that may be attached to the metal; and m+n is the maximum number of ligands that may be attached to the metal.

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

(58) ##STR00014##

(59) (O—N) is a bidentate ligand, having metal coordinated to atoms O and N.

(60) In another aspect, M is selected from Ir and Pt.

(61) In a further aspect, (Y.sup.3-Y.sup.4) is a carbene ligand.

(62) Examples of organic compounds used as host are selected from the group consisting aromatic hydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, azulene; group consisting 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 group consisting 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. Wherein each group is further substituted by a substituent 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.

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

(64) ##STR00015## ##STR00016##

(65) R.sup.1 to R.sup.7 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, when it is aryl or heteroaryl, it has the similar definition as Ar's mentioned above.

(66) k is an integer from 0 to 20.

(67) X.sup.1 to X.sup.8 is selected from C (including CH) or N.

(68) Z.sup.1 and Z.sup.2 is selected from NR.sup.1, O, or S.

(69) HBL:

(70) 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 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.

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

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

(73) ##STR00017##

(74) k is an integer from 0 to 20; L is an ancillary ligand, m is an integer from 1 to 3.

(75) ETL:

(76) 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.

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

(78) ##STR00018##

(79) R.sup.1 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.

(80) Ar.sup.1 to Ar.sup.3 has the similar definition as Ar's mentioned above.

(81) k is an integer from 0 to 20.

(82) X.sup.1 to X.sup.8 is selected from C (including CH) or N.

(83) In another aspect, the metal complexes used in ETL contains, but not limit to the following general formula:

(84) ##STR00019##

(85) (O—N) or (N—N) is a bidentate ligand, having metal coordinated to atoms O, N or N, N; L is an ancillary ligand; m is an integer value from 1 to the maximum number of ligands that may be attached to the metal.

(86) 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. encompasses undeuterated, partially deuterated, and fully deuterated versions thereof. Similarly, classes of substituents such as, without limitation, alkyl, aryl, cycloalkyl, heteroaryl, etc. also encompass undeuterated, partially deuterated, and fully deuterated versions thereof.

(87) 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 XXX below. Table XXX lists non-limiting classes of materials, non-limiting examples of compounds for each class, and references that disclose the materials.

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(89) 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.