ORGANIC ELECTROLUMINESCENT MATERIALS AND DEVICES

Provided is an OLED having an emissive region having a first compound and a second compound. The first compound is capable of energy transfer to the second compound. The first compound is capable of functioning as a TADF emitter in an OLED at room temperature, wherein the first compound includes a boron atom possessing a trigonal planar coordination geometry. The first compound has a first singlet state S1, a first triplet state T1, and a second triplet state T2 energies; and the second compound is a fluorescent compound functioning as an emitter in the OLED at room temperature.

FIELD

The present disclosure generally relates to organometallic compounds and formulations and their various uses including as emitters in devices such as organic light emitting diodes and related electronic devices.

BACKGROUND

Opto-electronic devices that make use of organic materials are becoming increasingly desirable for various reasons. Many of the materials used to make such devices are relatively inexpensive, so organic opto-electronic devices have the potential for cost advantages over inorganic devices. In addition, the inherent properties of organic materials, such as their flexibility, may make them well suited for particular applications such as fabrication on a flexible substrate. Examples of organic opto-electronic devices include organic light emitting diodes/devices (OLEDs), organic phototransistors, organic photovoltaic cells, and organic photodetectors. For OLEDs, the organic materials may have performance advantages over conventional materials.

OLEDs make use of thin organic films that emit light when voltage is applied across the device. OLEDs are becoming an increasingly interesting technology for use in applications such as flat panel displays, illumination, and backlighting.

SUMMARY

In one aspect, the present disclosure provides an OLED comprising an anode, a cathode, and an emissive region disposed between the anode and the cathode, wherein the emissive region comprises a first compound and a second compound. The first compound is capable of energy transfer to the second compound. The first compound is capable of functioning as a TADF emitter in an OLED at room temperature, wherein the first compound comprises a boron atom possessing a trigonal planar coordination geometry.

In some embodiments, the first compound has a first singlet state S1, a first triplet state T1, and a second triplet state T2energies; and the second compound is a fluorescent compound functioning as an emitter in the OLED at room temperature.

In another aspect, the present disclosure provides a formulation comprising: a first compound and a second compound. The first compound is capable of energy transfer to the second compound. The first compound is capable of functioning as a TADF emitter in an OLED at room temperature, wherein the first compound comprises a boron atom possessing a trigonal planar coordination geometry. The first compound has a first singlet state S1, a first triplet state T1, and a second triplet state T2energies; and the second compound is a fluorescent compound functioning as an emitter in the OLED at room temperature

In another aspect, the present disclosure provides a chemical structure selected from the group consisting of a monomer, a polymer, a macromolecule, and a supramolecule, wherein the chemical structure comprises: a first group, a monovalent or polyvalent variant thereof, a second group, a monovalent or polyvalent variant thereof, wherein the first group is capable of energy transfer to the second group, and the first group is capable of functioning as a TADF emitter in an OLED at room temperature when the group stands alone as a compound, wherein the first group comprises a boron atom possessing a trigonal planar coordination geometry. The first group has a first singlet state S1, a first triplet state T1, and a second triplet state T2energies when the group stands alone as a compound. The second group is a fluorescent compound functioning as an emitter in the OLED at room temperature when the group stands alone as a compound.

Also disclosed is a premixed co-evaporation source that is a mixture of a first compound and a second compound; where the co-evaporation source is a co-evaporation source for vacuum deposition process or an OVJP process. In the premixed co-evaporation source, the first compound is capable of energy transfer to the second compound, the first compound is capable of functioning as a TADF emitter in an OLED at room temperature, wherein the first compound comprises a boron atom possessing a trigonal planar coordination geometry; the first compound has a first singlet state S1, a first triplet state T1, and a second triplet state T2energies; and the second compound is a fluorescent compound functioning as an emitter in the OLED at room temperature.

Also disclosed is a method for fabricating an OLED, the method comprising: providing a substrate having a first electrode disposed thereon; depositing a first organic layer over the first electrode by evaporating a pre-mixed co-evaporation source that is a mixture of a first compound and a second compound in a high vacuum deposition tool with a chamber base pressure between 1×10−6Torr to 1×10−9Torr; and depositing a second electrode over the first organic layer, wherein the first compound and the second compound are those described herein.

In yet another aspect, the present disclosure provides a consumer product comprising an OLED disclosed herein.

DETAILED DESCRIPTION

The term “ester” refers to a substituted oxycarbonyl (—O—C(O)—R, or —C(O)—O—Rs) radical.

The term “ether” refers to an —ORsradical.

The term “selenyl” refers to a —SeRsradical.

The term “sulfinyl” refers to a —S(O)—Rsradical.

The term “sulfonyl” refers to a —SO2—Rsradical.

The term “phosphino” refers to a —P(Rs)3radical, wherein each R, can be same or different.

The term “silyl” refers to a —Si(Rs)3radical, wherein each R, can be same or different.

The term “germyl” refers to a —Ge(Rs)3radical, wherein each R, can be same or different.

The term “boryl” refers to a —B(Rs)2radical or its Lewis adduct —B(Rs)3radical, wherein Rscan be same or different.

The term “alkenyl” refers to and includes both straight and branched chain alkene radicals. Alkenyl groups are essentially alkyl groups that include at least one carbon-carbon double bond in the alkyl chain. Cycloalkenyl groups are essentially cycloalkyl groups that include at least one carbon-carbon double bond in the cycloalkyl ring. The term “heteroalkenyl” as used herein refers to an alkenyl radical having at least one carbon atom replaced by a heteroatom. Optionally the at least one heteroatom is selected from O, S, N, P, B, Si, and Se, preferably, O, S, or N. Preferred alkenyl, cycloalkenyl, or heteroalkenyl groups are those containing two to fifteen carbon atoms. Additionally, the alkenyl, cycloalkenyl, or heteroalkenyl group may be optionally substituted.

The term “alkynyl” refers to and includes both straight and branched chain alkyne radicals. Alkynyl groups are essentially alkyl groups that include at least one carbon-carbon triple bond in the alkyl chain. Preferred alkynyl groups are those containing two to fifteen carbon atoms. Additionally, the alkynyl group may be optionally substituted.

The terms “aralkyl” or “arylalkyl” are used interchangeably and refer to an alkyl group that is substituted with an aryl group. Additionally, the aralkyl group may be optionally substituted.

The term “heterocyclic group” refers to and includes aromatic and non-aromatic cyclic radicals containing at least one heteroatom. Optionally the at least one heteroatom is selected from O, S, N, P, B, Si, and Se, preferably, O, S, or N. Hetero-aromatic cyclic radicals may be used interchangeably with 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/thio-ethers, such as tetrahydrofuran, tetrahydropyran, tetrahydrothiophene, and the like. Additionally, the heterocyclic group may be optionally substituted.

In some instances, the more preferred general substituents are selected from the group consisting of deuterium, fluorine, alkyl, cycloalkyl, alkoxy, aryloxy, amino, silyl, boryl, aryl, heteroaryl, sulfanyl, and combinations thereof.

In yet other instances, the most preferred general substituents are selected from the group consisting of deuterium, fluorine, alkyl, cycloalkyl, aryl, heteroaryl, and combinations thereof.

The terms “substituted” and “substitution” refer to a substituent other than H that is bonded to the relevant position, e.g., a carbon or nitrogen. For example, when R1represents mono-substitution, then one R1must be other than H (i.e., a substitution). Similarly, when R1represents di-substitution, then two of R1must be other than H. Similarly, when R1represents zero or no substitution, R1, for example, can be a hydrogen for available valencies of ring atoms, as in carbon atoms for benzene and the nitrogen atom in pyrrole, or simply represents nothing for ring atoms with fully filled valencies, e.g., the nitrogen atom in pyridine. The maximum number of substitutions possible in a ring structure will depend on the total number of available valencies in the ring atoms.

In some instance, a pair of adjacent substituents can be optionally joined or fused into a ring. The preferred ring is a five, six, or seven-membered carbocyclic or heterocyclic ring, includes both instances where the portion of the ring formed by the pair of substituents is saturated and where the portion of the ring formed by the pair of substituents is unsaturated. As used herein, “adjacent” means that the two substituents involved can be on the same ring next to each other, or on two neighboring rings having the two closest available substitutable positions, such as 2, 2′ positions in a biphenyl, or 1, 8 position in a naphthalene, as long as they can form a stable fused ring system.

B. The Compounds of the Present Disclosure

Also disclosed is a chemical structure selected from the group consisting of a monomer, a polymer, a macromolecule, and a supramolecule, wherein the chemical structure comprises: a first group, a monovalent or polyvalent variant thereof, a second group, a monovalent or polyvalent variant thereof, wherein the first group is capable of energy transfer to the second group, and the first group is capable of functioning as a thermally activated delayed fluorescent (TADF) emitter in an OLED at room temperature when the group stands alone as a compound, wherein the first group comprises a boron atom possessing a trigonal planar coordination geometry. The first group has a first singlet state S1, a first triplet state T1, and a second triplet state T2energies when the group stands alone as a compound. The second group is a fluorescent compound functioning as an emitter in the OLED at room temperature when the group stands alone as a compound. In the context of the present disclosure, room temperature is understood to be about 65-75 deg. F.

C. The OLED of the Present Disclosure

Disclosed herein is an OLED architecture that incorporates a specific combination of a first compound and a second compound in which the singlet and triplet excitons, which are electrogenerated within the device, can be harvested by the first compound and can subsequently energy transfer to the second compound that can function as a fluorescent emitter at room temperature. This system which ultimately emits predominantly from the fluorescent emitter can have a short transient time similar to fluorescent emitting systems while also efficiently harvesting all or the majority of the electrogenerated singlets and triplets.

The OLED of the present disclosure contains a sensitizer and a fluorescent acceptor. The sensitizer is a TADF compound comprising a fused three coordinate boron containing moiety which is capable of efficiently harvesting both singlet and triplet excitons and subsequently transfer the energy to the fluorescent acceptor which emits via a fluorescence emission process.

TADF sensitized fluorescence typically pairs a donor-acceptor (D-A) type TADF material with a fluorescent acceptors including the class of 5,9-dihydro-5,9-diaza-13b-boranaphtho[3,2,1-de]anthracenes (DABNAs/NBNs). In this case, the D-A serves to harvest the electrogenerated excitons which are then energy transferred to the fluorescent acceptor, which in the case of NBN can be very narrow. To achieve the desired blue emission and achieve sufficient spectral overlap for efficient energy transfer, the emission from the D-A TADF molecule needs to be very blue which can lead to low device lifetimes.

Disclosed are TADF compounds, including NBN compounds, to be used as the sensitizer and fluorescent compounds to be used as the acceptor. It is believed doing so can take advantage of the narrow absorption and emission lineshapes of the NBNs and other related or similar compounds to achieve a deep blue color without requiring ultra-high triplet energies.

It is also believed that a sensitizer may be selected to maximize the reverse intersystem crossing rate by minimizing the singlet-triplet gap (S1-T1gap=ΔEST) or by mixing in additional triplet states very close to the S1. Minimizing ΔESTcan be achieved by tuning the charge transfer (CT) state to separate the HOMO and LUMO more significantly. These additional triplet states can be provided by attaching additional chromophores to the sensitizer core, or by attaching electron donor or acceptor moieties to induce a CT state at appropriate energy. A fluorescent acceptor may be selected to have a large ΔESTto ensure primarily prompt fluorescence from the compound and minimize the ISC to the triplet state. This emitter can then be optimized to emit with short transients, narrow line shape, and high PLQY. It is further believed that a low T1moiety on the acceptor can dissipate any non-desirable triplets coming from Dexter transfer while maintaining the desirable fluorescent emission properties of the acceptor.

Most of the prior art using NBN have focused on using these compounds solely as the fluorescent emitter, not as a sensitizer. Furthermore, the specification of an NBN with small ΔESTand a second compound with a large ΔESTis counter to many claims of trying to use TADF materials as acceptors for triplet recycling.

In one aspect, the present disclosure provides an OLED comprising an anode, a cathode, and an emissive region disposed between the anode and the cathode, wherein the emissive region comprises a first compound and a second compound. The first compound is capable of energy transfer to the second compound. The first compound is capable of functioning as a TADF emitter in an OLED at room temperature, wherein the first compound comprises a boron atom possessing a trigonal planar coordination geometry. The first compound has a first singlet state S1, a first triplet state T1, and a second triplet state T2energies; and the second compound is a fluorescent compound functioning as an emitter in the OLED at room temperature.

In some embodiments of the OLED, the first and second compounds are in separate layers within the emissive region.

In some embodiments of the OLED, the first and second compounds are present as a mixture in the emissive region.

In some embodiments of the OLED, the first compound has a ΔEST<200 meV. As used herein, ΔESTof a compound is the absolute value of S1-T1energy gap of that compound.

In some embodiments of the OLED, the first compound has a ΔEST<150 meV. In some embodiments, the first compound has a ΔEST<100 meV. In some embodiments of the OLED, the first compound has a ΔEST<50 meV.

In some embodiments of the OLED, the second compound has a ΔEST>150 meV. In some embodiments of the OLED, the second compound has a ΔEST>200 meV. In some embodiments of the OLED, the second compound has a ΔEST>250 meV. In some embodiments of the OLED, the second compound has a ΔEST>300 meV. In some embodiments of the OLED, the second compound has a ΔEST>400 meV.

In some embodiments of the OLED, the second compound comprises a boron atom possessing a trigonal planar coordination geometry.

In some embodiments of the OLED, the first compound is a multi-resonant TADF compound. In some embodiments of the OLED, the first compound is a donor-acceptor TADF compound.

In some embodiments of the OLED, the first compound has the structure of

each of ring A, ring B, ring C, and ring D is independently a 5-membered or 6-membered carbocyclic or heterocyclic ring;

each of RA, RB, RC, and RDindependently represents zero, mono, or up to the maximum allowed number of substitutions to its associated ring;

In some embodiments of the OLED, the first compound has a structure selected from the group consisting of:

wherein X5-X19are each independently C or N; RErepresents zero, mono, or up to the maximum allowed number of substitutions to its associated ring; and Y2, Y3, and Y4are each independently selected from the group consisting of a single bond, O, S, Se, NR, CRR′, SiRR′, GeRR′, BR, and BRR′.

In some embodiments of the OLED, the second compound has a structure of

each of ring A, ring B, ring C, and ring D is independently a 5-membered or 6-membered carbocyclic or heterocyclic ring;

each of RA, RB, RC, and RDindependently represents zero, mono, or up to the maximum allowed number of substitutions to its associated ring;

In some embodiments of the OLED, the second compound has a structure selected from the group consisting of:

wherein X5-X19are each independently C or N; RErepresents zero, mono, or up to the maximum allowed number of substitutions to its associated ring; and Y2, Y3, and Y4are each independently selected from the group consisting of a single bond, O, S, Se, NR, CRR′, SiRR′, GeRR′, BR, and BRR′.

In some embodiments of the OLED, the first compound has S1, T1, and T2energy states, and wherein the absolute value of S1-T2is <200 meV.

In some embodiments of the OLED, the T2energy state of the first compound is a charge transfer state.

In some embodiments of the OLED, the first compound has a photoluminescent FWHM (full width half maximum) of <30 nm.

In some embodiments of the OLED, the second compound has a photoluminescent FWHM of <30 nm.

In some embodiments of the OLED, the emission of the first compound has a spectral overlap with the absorption of the second compound.

In some embodiments of the OLED, the first compound is selected from the group consisting of:

In some embodiments of the OLED, the second compound comprises at least one organic group selected from the group consisting of:

and aza analogues thereof;
wherein A is selected from the group consisting of O, S, Se, NR′ and CR′R″;
wherein each R′ can be the same or different and each R′ is independently selected from the group consisting of alkyl, cycloalkyl, aryl, heteroaryl, and combinations thereof.

In some embodiments of the OLED, the second compound is selected from the group consisting of:

wherein R1to R5each independently represents from mono to maximum possible number of substitutions, or no substitution; and

In some embodiments of the OLED, the second compound is selected from the group consisting of:

In some embodiments of the OLED, the emissive region further comprises a first host; wherein the first host has higher S1and T1energies than those of the first and second compounds; and wherein the first and second compounds are dopants. In some embodiments, the first host has the highest S1and T1energies among all materials in the emissive region. In some embodiments of the OLED, the emissive region further comprises a second host; wherein the second host has higher S1and T1energies than those of the first and second compounds.

In some embodiments of the OLED, the first host comprises at least one chemical group selected from the group consisting of triphenylene, carbazole, dibenzothiphene, dibenzofuran, dibenzoselenophene, azatriphenylene, azacarbazole, aza-dibenzothiophene, aza-dibenzofuran, and aza-dibenzoselenophene.

In some embodiments of the OLED, the emissive region further comprises a third host; wherein the third host has higher S1and T1energies than the first and second compounds.

In some embodiments of the OLED, the emissive region further comprises a fourth host; wherein the fourth host has higher S1and T1energies than those of the first and second compounds.

In some embodiments of the OLED, the first compound can be in a layer separate from the second compound in the emissive region or the first compound can be in a layer mixed with the second compound, where the concentration of the first compound in the layer containing the first compound is in the range of 1 to 50% by weight. In some embodiments of the OLED, the concentration of the first compound is in the range of 5 to 40% by weight. In some embodiments of the OLED, the concentration of the first compound is in the range of 10 to 20% by weight. In some embodiments of the OLED, the concentration of the first compound is in the range of 12 to 15% by weight.

In some embodiments of the OLED, the second compound is in a layer separate from the first compound in the emissive region or the second compound can be in a layer mixed with the first compound, wherein the concentration of the second compound in the layer containing the second compound is in the range of 1 to 99% by weight. In some embodiments of the OLED, the concentration of the second compound is in the range of 10 to 80% by weight. In some embodiments of the OLED, the concentration of the second compound is in the range of 20 to 70% by weight. In some embodiments of the OLED, the concentration of the second compound is in the range of 25 to 60% by weight. In some embodiments of the OLED, the concentration of the second compound is in the range of 30 to 50% by weight.

In some embodiments, the emissive region may further comprise a host, wherein the host comprises a triphenylene containing benzo-fused thiophene or benzo-fused furan, wherein any substituent in the host is an unfused substituent independently selected from the group consisting of CnH2n+1, OCnH2n+1, OAr1, N(CnH2n+1)2, N(Ar1)(Ar2), CH═CH—CnH2n+1, C≡CCnH2n+1, Ar1, Ar1—Ar2, CnH2n—Ar1, or no substitution, wherein n is from 1 to 10; and wherein Ar1and Ar2are independently selected from the group consisting of benzene, biphenyl, naphthalene, triphenylene, carbazole, and heteroaromatic analogs thereof.

In some embodiments, the emissive region may further comprise a host, wherein host comprises at least one chemical group selected from the group consisting of triphenylene, carbazole, indolocarbazole, dibenzothiophene, dibenzofuran, dibenzoselenophene, 5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene, aza-triphenylene, aza-carbazole, aza-indolocarbazole, aza-dibenzothiophene, aza-dibenzofuran, aza-dibenzoselenophene, and aza-(5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene).

In some embodiments, the host may be selected from the HOST Group consisting of:

and combinations thereof.

Also disclosed is a formulation comprising the first compound and the second compound that are disclosed herein.

Often, the emissive layer (EML) of OLED devices exhibiting good lifetime and efficiency requires more than two components (e.g. 3 or 4 components). For this purpose, 3 or 4 source materials are required to fabricate such an EML, which is very complicated and costly compared to a standard two-component EML with a single host and an emitter, which requires only two sources. Typically, in order to fabricate such an EML requiring more than two components, a separate evaporation source for each component is used. Because the relative concentrations of the components of the EML is important for the device performance, the rate of deposition of each component is measured individually during the deposition in order to monitor the relative concentrations. This makes the fabrication process complicated and costly. Thus, when there are more than two components for a layer to be deposited, it is desirable to premix the materials for the two or more components and evaporate them from a single crucible in order to reduce the complexity of the vacuum deposition process.

However, the co-evaporation must be stable, i.e. the composition of the evaporated film should remain constant during the vacuum deposition process. Any composition change may affect the device performance adversely. In order to obtain a stable co-evaporation from a mixture of compounds under vacuum, one would assume that the materials should have the same evaporation temperature under the same condition. However, this may not be the only parameter one has to consider. When the two compounds are mixed together, they may interact with each other and their evaporation properties 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. “Evaporation temperature” of a material is measured in a high vacuum deposition tool with a chamber base pressure between 1×10−6Torr to 1×10−9Torr, 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.

This disclosure describes a novel composition comprising a mixture of two or more organic compounds that can be used as a stable co-evaporation source in vacuum deposition processes (e.g. VTE) is disclosed. Many factors other than temperatures can contribute to the evaporation, such as miscibility of different materials, different phase transition. The inventors found that when two or more materials have similar evaporation temperature, and similar mass loss rate or similar vapor pressure, the two or more materials can co-evaporate consistently. Mass loss rate is defined as percentage of mass lost over time (minute) and is determined by measuring the time it takes to lose the first 10% of the mass as measured by thermal gravity analysis (TGA) under same experimental condition at a same constant given temperature for each compound after the composition reach a steady evaporation state. The constant given temperature is one temperature point that is chosen so that the value of mass loss rate is between about 0.05 to 0.50 percentage/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.

Searching for a high-performance mixture for stable single-source co-evaporation could be a tedious process. A process of searching for a stable mixture would include identifying compounds with similar evaporation temperatures and monitoring the composition of the evaporated mixture. It is often the case that the two materials show slight separation as evaporation proceeds. Adjusting the evaporation temperature by changing the chemical structure often, unfortunately, leads to much degraded device performance due to the change in chemical, electrical and/or optical properties. Chemical structure modifications also impact the evaporation temperature much more significantly than needed, resulting in unstable mixtures. Thus, identification of workable premixed co-evaporation sources is useful.

Disclosed herein is a premixed co-evaporation source that is a mixture of a first compound and a second compound; where the co-evaporation source is a co-evaporation source for vacuum deposition process or an OVJP process. In the premixed co-evaporation source, the first compound is capable of energy transfer to the second compound, the first compound is capable of functioning as a TADF emitter in an OLED at room temperature, wherein the first compound comprises a boron atom possessing a trigonal planar coordination geometry; the first compound has a first singlet state S1, a first triplet state T1, and a second triplet state T2energies; and the second compound is a fluorescent compound functioning as an emitter in the OLED at room temperature.

F. Method for Fabricating an OLED

Also disclosed herein is a method for fabricating an OLED, the method comprising: providing a substrate having a first electrode disposed thereon; depositing a first organic layer over the first electrode by evaporating a pre-mixed co-evaporation source that is a mixture of a first compound and a second compound in a high vacuum deposition tool with a chamber base pressure between 1×10−6Torr to 1×10−9Torr; and depositing a second electrode over the first organic layer, where the first compound is capable of energy transfer to the second compound, where he first compound is capable of functioning as a TADF emitter in an OLED at room temperature, where the first compound comprises a boron atom possessing a trigonal planar coordination geometry, where the first compound has a first singlet state S1, a first triplet state T1, and a second triplet state T2energies; and the second compound is a fluorescent compound functioning as an emitter in the OLED at room temperature.

In some embodiments, at least one of the anode, the cathode, or a new layer disposed over the organic emissive layer functions as an enhancement layer. The enhancement layer comprises a plasmonic material exhibiting surface plasmon resonance that non-radiatively couples to the emitter material and transfers excited state energy from the emitter material to non-radiative mode of surface plasmon polariton. The enhancement layer is provided no more than a threshold distance away from the organic emissive layer, wherein the emitter material has a total non-radiative decay rate constant and a total radiative decay rate constant due to the presence of the enhancement layer and the threshold distance is where the total non-radiative decay rate constant is equal to the total radiative decay rate constant. In some embodiments, the OLED further comprises an outcoupling layer. In some embodiments, the outcoupling layer is disposed over the enhancement layer on the opposite side of the organic emissive layer. In some embodiments, the outcoupling layer is disposed on opposite side of the emissive layer from the enhancement layer but still outcouples energy from the surface plasmon mode of the enhancement layer. The outcoupling layer scatters the energy from the surface plasmon polaritons. In some embodiments this energy is scattered as photons to free space. In other embodiments, the energy is scattered from the surface plasmon mode into other modes of the device such as but not limited to the organic waveguide mode, the substrate mode, or another waveguiding mode. If energy is scattered to the non-free space mode of the OLED other outcoupling schemes could be incorporated to extract that energy to free space. In some embodiments, one or more intervening layer can be disposed between the enhancement layer and the outcoupling layer. The examples for interventing layer(s) can be dielectric materials, including organic, inorganic, perovskites, oxides, and may include stacks and/or mixtures of these materials.

The enhancement layer modifies the effective properties of the medium in which the emitter material resides resulting in any or all of the following: a decreased rate of emission, a modification of emission line-shape, a change in emission intensity with angle, a change in the stability of the emitter material, a change in the efficiency of the OLED, and reduced efficiency roll-off of the OLED device. Placement of the enhancement layer on the cathode side, anode side, or on both sides results in OLED devices which take advantage of any of the above-mentioned effects. In addition to the specific functional layers mentioned herein and illustrated in the various OLED examples shown in the figures, the OLEDs according to the present disclosure may include any of the other functional layers often found in OLEDs.

The enhancement layer can be comprised of plasmonic materials, optically active metamaterials, or hyperbolic metamaterials. As used herein, a plasmonic material is a material in which the real part of the dielectric constant crosses zero in the visible or ultraviolet region of the electromagnetic spectrum. In some embodiments, the plasmonic material includes at least one metal. In such embodiments the metal may include at least one of Ag, Al, Au, Ir, Pt, Ni, Cu, W, Ta, Fe, Cr, Mg, Ga, Rh, Ti, Ru, Pd, In, Bi, Ca alloys or mixtures of these materials, and stacks of these materials. In general, a metamaterial is a medium composed of different materials where the medium as a whole acts differently than the sum of its material parts. In particular, we define optically active metamaterials as materials which have both negative permittivity and negative permeability. Hyperbolic metamaterials, on the other hand, are anisotropic media in which the permittivity or permeability are of different sign for different spatial directions. Optically active metamaterials and hyperbolic metamaterials are strictly distinguished from many other photonic structures such as Distributed Bragg Reflectors (“DBRs”) in that the medium should appear uniform in the direction of propagation on the length scale of the wavelength of light. Using terminology that one skilled in the art can understand: the dielectric constant of the metamaterials in the direction of propagation can be described with the effective medium approximation. Plasmonic materials and metamaterials provide methods for controlling the propagation of light that can enhance OLED performance in a number of ways.

In some embodiments, the enhancement layer is provided as a planar layer. In other embodiments, the enhancement layer has wavelength-sized features that are arranged periodically, quasi-periodically, or randomly, or sub-wavelength-sized features that are arranged periodically, quasi-periodically, or randomly. In some embodiments, the wavelength-sized features and the sub-wavelength-sized features have sharp edges.

In some embodiments, the outcoupling layer has wavelength-sized features that are arranged periodically, quasi-periodically, or randomly, or sub-wavelength-sized features that are arranged periodically, quasi-periodically, or randomly. In some embodiments, the outcoupling layer may be composed of a plurality of nanoparticles and in other embodiments the outcoupling layer is composed of a pluraility of nanoparticles disposed over a material. In these embodiments the outcoupling may be tunable by at least one of varying a size of the plurality of nanoparticles, varying a shape of the plurality of nanoparticles, changing a material of the plurality of nanoparticles, adjusting a thickness of the material, changing the refractive index of the material or an additional layer disposed on the plurality of nanoparticles, varying a thickness of the enhancement layer, and/or varying the material of the enhancement layer. The plurality of nanoparticles of the device may be formed from at least one of metal, dielectric material, semiconductor materials, an alloy of metal, a mixture of dielectric materials, a stack or layering of one or more materials, and/or a core of one type of material and that is coated with a shell of a different type of material. In some embodiments, the outcoupling layer is composed of at least metal nanoparticles wherein the metal is selected from the group consisting of Ag, Al, Au, Ir, Pt, Ni, Cu, W, Ta, Fe, Cr, Mg, Ga, Rh, Ti, Ru, Pd, In, Bi, Ca, alloys or mixtures of these materials, and stacks of these materials. The plurality of nanoparticles may have additional layer disposed over them. In some embodiments, the polarization of the emission can be tuned using the outcoupling layer. Varying the dimensionality and periodicity of the outcoupling layer can select a type of polarization that is preferentially outcoupled to air. In some embodiments the outcoupling layer also acts as an electrode of the device.

G. Consumer Products

In yet another aspect, the present disclosure also provides a consumer product comprising an OLED disclosed herein.

In some embodiments, the consumer product can be one of a flat panel 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 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 wall comprising multiple displays tiled together, a theater or stadium screen, a light therapy device, and a sign.

Several OLED materials and configurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and 5,707,745, which are incorporated herein by reference in their entirety.

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; see, e.g., U.S. application Ser. No. 15/700,352, which is hereby incorporated by reference in its entirety), triplet-triplet annihilation, or combinations of these processes. In some embodiments, the emissive dopant can be a racemic mixture, or can be enriched in one enantiomer. In some embodiments, the compound can be homoleptic (each ligand is the same). In some embodiments, the compound can be heteroleptic (at least one ligand is different from others). When there are more than one ligand coordinated to a metal, the ligands can all be the same in some embodiments. In some other embodiments, at least one ligand is different from the other ligands. In some embodiments, every ligand can be different from each other. This is also true in embodiments where a ligand being coordinated to a metal can be linked with other ligands being coordinated to that metal to form a tridentate, tetradentate, pentadentate, or hexadentate ligands. Thus, where the coordinating ligands are being linked together, all of the ligands can be the same in some embodiments, and at least one of the ligands being linked can be different from the other ligand(s) in some other embodiments.

In some embodiments, the compound can be used as a phosphorescent sensitizer in an OLED where one or multiple layers in the OLED contains an acceptor in the form of one or more fluorescent and/or delayed fluorescence emitters. In some embodiments, the compound can be used as one component of an exciplex to be used as a sensitizer. As a phosphorescent sensitizer, the compound must be capable of energy transfer to the acceptor and the acceptor will emit the energy or further transfer energy to a final emitter. The acceptor concentrations can range from 0.0010% to 100%. The acceptor could be in either the same layer as the phosphorescent sensitizer or in one or more different layers. In some embodiments, the acceptor is a TADF emitter. In some embodiments, the acceptor is a fluorescent emitter. In some embodiments, the emission can arise from any or all of the sensitizer, acceptor, and final emitter.

According to another aspect, a formulation comprising the compound described herein is also disclosed.

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, electron blocking material, hole blocking material, and an electron transport material, disclosed herein.

The present disclosure encompasses any chemical structure comprising the novel compound of the present disclosure, or a monovalent or polyvalent variant thereof. In other words, the inventive compound, or a monovalent or polyvalent variant thereof, can be a part of a larger chemical structure. Such chemical structure can be selected from the group consisting of a monomer, a polymer, a macromolecule, and a supramolecule (also known as supermolecule). As used herein, a “monovalent variant of a compound” refers to a moiety that is identical to the compound except that one hydrogen has been removed and replaced with a bond to the rest of the chemical structure. As used herein, a “polyvalent variant of a compound” refers to a moiety that is identical to the compound except that more than one hydrogen has been removed and replaced with a bond or bonds to the rest of the chemical structure. In the instance of a supramolecule, the inventive compound can also be incorporated into the supramolecule complex without covalent bonds.

H. Combination of the Compounds of the Present Disclosure with Other Materials

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.

In one aspect, the metal complexes are:

wherein k is an integer from 1 to 20; L101is another ligand, k′ is an integer from 1 to 3.

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.

EXPERIMENTAL

OLED devices were fabricated using TADF 1 as a TADF emitter or as a sensitizer for Acceptor 1. The device results are shown in Table 1 where the EQE and voltage are taken at 10 mA/cm2and the lifetime (LT90) is the time to reduction of brightness to 90% of the initial luminance at a constant current density of 20 mA/cm2.

The OLEDs were grown on a glass substrate pre-coated with an indium-tin-oxide (ITO) layer having a sheet resistance of 15-Ω/sq. Prior to any organic layer deposition or coating, the substrate was degreased with solvents and then treated with an oxygen plasma for 1.5 minutes with 50 W at 100 mTorr and with UV ozone for 5 minutes. The devices in Table 2 were fabricated in high vacuum (<10−6Torr) by thermal evaporation. The anode electrode was 750 Å of indium tin oxide (ITO). All devices were encapsulated with a glass lid sealed with an epoxy resin in a nitrogen glove box (<1 ppm of H2O and O2) immediately after fabrication with a moisture getter incorporated inside the package. Doping percentages are in volume percent. The devices were grown in two different device structures.

The devices shown in Table 1 had organic layers consisting of, sequentially, from the ITO surface, 100 Å of Compound 1 (HIL), 250 Å of Compound 2 (HTL), 50 Å of Compound 3 (EBL), 300 Å of Compound 3 doped with 40% of Compound 4, 5% of TADF 1, and 0 or 0.5% of Acceptor 1 (EML), 50 Å of Compound 4 (BL), 300 Å of Compound 5 doped with 35% of Compound 6 (ETL), 10 Å of Compound 5 (EIL) followed by 1,000 Å of Al (Cathode). The device performance for the devices with doped with 0.5% of Acceptor 1 (Example 1) and with no Acceptor 1 (Comparison 1) are shown in Table 1. The voltage, EQE and LT90for the device Example 1 are reported relative to the values for Comparative 1.