WO2017151537A1 - Spirobifluorene derivatives and their use in electron transport layers of organic electronic devices - Google Patents

Abstract

The present invention relates to spirobifluorene derivatives and their use in the electron transport layers of organic electronic devices, such as, for example, organic light-emitting devices.

Description

SPIROBIFLUORENE DERIVATIVES AND THEIR USE IN ELECTRON TRANSPORT LAYERS OF ORGANIC ELECTRONIC DEVICES

Cross Reference to Related Applications

This application claims the priority of U.S. Provisional Application No. 62/303,645 filed March 4, 2016, which is hereby incorporated by reference in its entirety.

Field of the Invention

The present invention relates to spirobifluorene derivatives, typically having nitrogen- containing heteroaryl rings, and their use in the electron transport layers of organic electronic devices, such as, for example, organic light-emitting devices. Background

Various organic electronic devices are currently under active study and development, in particular optoelectronic devices based on electroluminescence (EL) from organic materials. In contrast to photoluminescence, i.e. the light emission from an active material as a consequence of optical absorption and relaxation by radiative decay of an excited state, electroluminescence is a non-thermal generation of light resulting from the application of an electric field to a substrate. In this latter case, excitation is

accomplished by recombination of charge carriers of contrary signs (electrons and holes) injected into an organic semiconductor in the presence of an external circuit. A simple prototype of an organic light-emitting device (OLED), i.e. a single layer OLED, is typically composed of a thin film of an active organic material which is sandwiched between two electrodes, one of which needs to have a degree of transparency sufficient in order to observe light emission from the organic layer. If an external voltage is applied to the two electrodes, charge carriers, i.e. holes at the anode and electrons at the cathode, are injected to the organic layer beyond a specific threshold voltage depending on the organic material applied. In the presence of an electric field, charge carriers move through the active layer and are non-radiatively discharged when they reach the oppositely charged electrode. However, if a hole and an electron encounter one another while drifting through the organic layer, excited singlet (anti-symmetric) and triplet (symmetric) states, so-called excitons, are formed. For every three triplet excitons that are formed by electrical excitation in an OLED, one anti-symmetric state (singlet) exciton is created. Light is thus generated in the organic material from the decay of molecular excited states (or excitons) according to a radiative recombination process known as either fluorescence for which spin symmetry is preserved, or phosphorescence when luminescence from both singlet and triplet excitons can be harvested.

High efficiency OLEDs based on small molecules usually comprise a multiplicity of different layers, each layer being optimized towards achieving the optimum efficiency of the overall device. Typically, such OLEDs comprise a multilayer structure comprising multiple layers serving different purposes. The typical OLED device stack comprises an anode, a hole transport layer (HTL), an emissive layer (EML), an electron transport layer (ETL), and a cathode. Optionally, a hole injection layer (HIL) may be disposed between the anode and HTL, or an electron injection layer (EIL) may be disposed between cathode and the ETL).

In order to achieve an optimum efficiency, the physical properties of each material for each individual layer of the stack, such properties being, for example, carrier transport properties, HOMO and LUMO levels, triplet levels, have to be selected properly depending on the functionality of the layer.

There is an ongoing, unresolved need for improved electron transport materials for organic electronic devices, such as OLEDs, to result in high efficiency, long lifetime and low operating voltages. Summary of the Invention

An object of the present invention is to provide organic electronic devices that have high efficiency, long lifetime and/or low operating voltages having improved electron transport layers.

Therefore, the present disclosure relates to an organic light-emitting device comprising: a substrate,

an anode,

a hole injection layer,

a hole transport layer,

an emissive layer,

an electron transport layer,

an electron injection layer, and

a cathode layer;

wherein the emissive layer and the electron transport layer each comprise a substituted or unsubstituted spirobifluorene compound, with the proviso that the spirobifluorene compound of the electron transport layer is a compound represented by general formula 1

(1 ) or general formula 2

(2) wherein

Ar is a substituted or unsubstituted nitrogen-containing heteroaryl ring comprising at least two nitrogen atoms in the ring,

An is a substituted or unsubstituted aryl or heteroaryl ring,

m is 0 or 1 ,

n is O or l ,

Xi to X₈ are each, independently, other than Ar or An and is a C1-C30 hydrocarbyl or C1-C30 heterohydrocarbyl, and

o, p, q, r, s, u, v and w, are each, independently, an integer from 0 to 3. Brief Description of the Figures

FIG. 1 shows the device structure of inventive green OLEDs described herein. Detailed Description

As used herein, the terms "a", "an", or "the" means "one or more" or "at least one" unless otherwise stated. As used herein, the term "comprises" includes "consists essentially of" and "consists of." The term "comprising" includes "consisting essentially of" and "consisting of." The phrase "free of" means that there is no external addition of the material modified by the phrase and that there is no detectable amount of the material that may be observed by analytical techniques known to the ordinarily-skilled artisan, such as, for example, gas or liquid chromatography, spectrophotometry, optical microscopy, and the like. Throughout the present disclosure, various publications may be incorporated by reference. Should the meaning of any language in such publications incorporated by reference conflict with the meaning of the language of the present disclosure, the meaning of the language of the present disclosure shall take precedence, unless otherwise indicated.

As used herein, the terminology "(Cx-Cy)" in reference to an organic group, wherein x and y are each integers, means that the group may contain from x carbon atoms to y carbon atoms per group. As used herein, the term "hydrocarbyl" means a monovalent radical formed by removing one hydrogen atom from a hydrocarbon, typically a (Ci-C₄o) hydrocarbon, more typically a (C1-C30) hydrocarbon. Hydrocarbyl groups may be straight, branched or cyclic, and may be saturated or unsaturated. Examples of hydrocarbyl groups include, but are not limited to, alkyl, alkenyl, alkynyl, cycloalkyl, and aryl.

The term "heterohydrocarbyl" means a hydrocarbyl group, typically a (Ci-C₄o)

hydrocarbyl, more typically a (C1 -C30) hydrocarbyl, wherein one or more of the carbon atoms within the hydrocarbyl group has been replaced by a hetero atom, such as, for example, nitrogen (N), oxygen (0), or sulfur (S). As used herein, the term "alkyl" means a monovalent straight or branched saturated hydrocarbon radical, more typically, a monovalent straight or branched saturated (Ci- C₄₀)hydrocarbon radical, such as, for example, methyl, ethyl, n-propyl, isopropyl, n- butyl, isobutyl, tert-butyl, hexyl, 2-ethylhexyl, octyl, hexadecyl, octadecyl, eicosyl, behenyl, tricontyl, and tetracontyl. As used herein, the term "cycloalkyl" means a monovalent saturated cyclic hydrocarbon radical, more typically a saturated cyclic (C5- C22) hydrocarbon radical, such as, for example, cyclopentyl, cycloheptyl, cyclooctyl.

As used herein, the term "fluoroalkyl" means an alkyl radical as defined herein, more typically a (Ci-C₄o) alkyl radical that is substituted with one or more fluorine atoms. Examples of fluoroalkyl groups include, for example, difluoromethyl, trifluoromethyl, perfluoroalkyl, 1 H,1 H,2H,2H-perfluorooctyl, perfluoroethyl, and -CH₂CF₃.

As used herein, the term "alkenyl" means an unsaturated straight or branched hydrocarbon radical, more typically an unsaturated straight, branched, (C2-C22) hydrocarbon radical, that contains one or more carbon-carbon double bonds, including, for example, ethenyl (vinyl), n-propenyl, and iso-propenyl, and allyl.

As used herein, the term "alkynyl" means an unsaturated straight or branched hydrocarbon radical, more typically an unsaturated straight, branched, (C2-C22) hydrocarbon radical, that contains one or more carbon-carbon triple bonds, including, for example, ethynyl, propynyl, and butynyl.

As used herein, the term "aryl" means a monovalent group having at least one aromatic ring. As understood by the ordinarily-skilled artisan, an aromatic ring has a plurality of carbon atoms, arranged in a ring and has a delocalized conjugated π electron system, typically represented by alternating single and double bonds. Aryl radicals include monocyclic aryl and polycyclic aryl. Polycyclic aryl means a monovalent group having two or more aromatic rings wherein adjacent rings may be linked to each other by one or more bonds or divalent bridging groups or may be fused together. Examples of aryl radicals include, but are not limited to, phenyl, anthracenyl, naphthyl, phenanthrenyl, fluorenyl, and pyrenyl.

As used herein, the term "aryloxy" means a monovalent radical denoted as -O-aryl, wherein the aryl group is as defined herein. Examples of aryloxy groups, include, but are not limited to, phenoxy, anthracenoxy, naphthoxy, phenanthrenoxy, and fluorenoxy.

As used herein, the term "alkoxy" means a monovalent radical denoted as -O-alkyl, wherein the alkyl group is as defined herein. Examples of alkoxy groups, include, but are not limited to, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, and tert-butoxy.

As used herein, the term "heteroaryl" means a monovalent group having at least one aromatic ring that includes at least one hetero atom in the ring, which may be

substituted at one or more atoms of the ring. Examples of heteroaryl groups include, but are not limited to, 5-membered groups such as thienyl, pyrrolyl, triazolyl, tetrazolyl, pyrazolyl, and imidazolyl groups; as well as 6-membered groups such as pyridinyl, pyrimidinyl, pyrazinyl, tetrazinyl, pyridazinyl, and triazinyl. The term "polycyclic heteroaryl" refers to a monovalent group having more than one aromatic ring, at least one of which includes at least one hetero atom in the ring, wherein adjacent rings may be linked to each other by one or more bonds or divalent bridging groups or may be fused together. Examples of polycyclic heteroaryl groups include, but are not limited to, indolyl and quinolinyl groups. As used herein, the term "hydrocarbylene" means a divalent radical formed by removing two hydrogen atoms from a hydrocarbon, typically a (Ci-C₄o) hydrocarbon.

Hydrocarbylene groups may be straight, branched or cyclic, and may be saturated or unsaturated. Examples of hydrocarbylene groups include, but are not limited to, alkylene groups, such as methylene, ethylene, 1 -methylethylene, 1 -phenylethylene, propylene, and butylene; and arylene groups, such as 1 ,2-benzene; 1 ,3-benzene; 1 ,4- benzene; and 2,6-naphthalene.

Any substituent or radical described herein may optionally be substituted at one or more carbon atoms with one or more, same or different, substituents described herein. For instance, a hydrocarbyl group may be further substituted with an aryl group or an alkyl group. Any substituent or radical described herein may also optionally be substituted at one or more carbon atoms with one or more substituents selected from the group consisting of halogen, such as, for example, F, CI, Br, and I; nitro (NO2), cyano (CN), and hydroxy (OH).

The electron transport layer plays a role in efficiently transporting the electrons that have been injected from the cathode or the electrons that have been injected from the cathode through the electron injection layer to the emissive layer. The electron injection layer plays a role in efficiently injecting the electrons that have been transferred from the cathode into the emissive layer or the electron transport layer. The electron transport layer and the electron injection layer are each generally formed by methods known to those of ordinary skill in the art. The electron transport layer and the emissive layer of the device of the present disclosure each comprise a substituted or unsubstituted spirobifluorene compound. As used herein, a spirobifluorene compound is a compound having a core represented by any one of the following structures:

When the spirobifluorene compound is substituted, any hydrogen atom on a hydrogen atom-bearing carbon of the spirobifluorene compound may be substituted.

In an embodiment, the spirobifluorene compound comprises one or more substituents other than H. Typically, the spirobifluorene compound comprises 1 to 12, more typically 1 to 4, even more typically 1 to 2, substituents.

In an embodiment, the spirobifluorene compound comprises substituents selected from the group consisting of Ci-C₄₀ hydrocarbyl and Ci-C₄₀ heterohydrocarbyl groups.

In embodiment, the spirobifluorene compound is substituted in the 3-position.

In an embodiment, the spirobifluorene compound of the electron transport layer is a compound represented by general formula 1

(1 ) or general formula 2

(2) wherein

Ar is a substituted or unsubstituted nitrogen-containing heteroaryl ring comprising at least two nitrogen atoms in the ring,

An is a substituted or unsubstituted aryl or heteroaryl ring,

m is 0 or 1 ,

n is 0 or 1 ,

Xi to X₈ are each, independently, other than Ar or Αη and is a Ci-C₃₀ hydrocarbyl or C1-C30 heterohydrocarbyl, and

o, p, q, r, s, u, v and w, are each, independently, an integer from 0 to 3.

In an embodiment, Ar is a heteroaryl ring selected from the group consisting of pyrazolyl, imidazolyl, triazolyl, pyrimidinyl, pyridazinyl, triazinyl and tetrazinyl.

In another embodiment, Ar is a heteroaryl ring selected from the group consisting of pyrimidinyl, pyridazinyl, triazinyl and tetrazinyl.

In an embodiment, An is a 5- or 6-membered aryl or heteroaryl ring.

In another embodiment, An is identical to Ar. In an embodiment, m and n are 1 .

In an embodiment, Ar is substituted with at least one aryl group. In an embodiment, Ar has the structure

wherein A represents C, N, 0 or S, provided that at least two atoms A are nitrogen and wherein the carbon atoms of Ar are substituted or unsubstituted.

In an embodiment, the compound of general formula 1 is a compound represented by any one of the following structures:

wherein

R-1 , which may be the same or different at each occurrence, is d -C₃₀ hydrocarbyl or C1-C30 heterohydrocarbyl;

A is C, N, 0, or S, with the proviso that at least two A atoms in the same ring are nitrogen. Typically, the compound of general formula 1 is a compound represented by any one of the following structures:





wherein Ri represents a phenyl group. The spirobifluorene compounds suitable for use in the emissive layer and the electron transport layer, typically compounds of general formula 1 or formula 2, may be obtained from commercial sources or synthesized according to methods known to those of ordinary skill in the chemical art. For example, nucleophilic aromatic substitution reactions and metal-catalyzed coupling reactions, such as, for example, Suzuki coupling using boronic ester derivatives, are suitable for the synthesis of the spirobifluorene compounds of general formula 1 or formula 2. Thus, a compound of general formula 1 may be synthesized by coupling, under palladium catalysis, a spirobifluorene compound substituted by a boronic acid or a boronic acid derivative, such as a boronic ester, to a nitrogen-containing heteraromatic compound having at least one reactive leaving group, such as Ar-LG or Ar-i-LG, wherein LG is a reactive leaving group. Suitable reactive leaving groups are, for example, halogens, in particular chlorine, bromine or iodine, triflate or tosylate. An exemplary synthesis pathway is shown in Scheme 1 . Sche

Similarly, a compound of general formula 2 may be synthesized by coupling, under palladium catalysis, an open spirobifluorene compound substituted by a boronic acid or a boronic acid derivative, such as a boronic ester, to a nitrogen-containing

heteraromatic compound having at least one reactive leaving group, such as Ar-LG or Ar-i-LG. An exemplary synthesis pathway is shown in Scheme 2.

The nitrogen-containing heteraromatic compound Ar-LG or Ar-i-LG is itself obtained by commercial sources or synthesized according to methods known to those of ordinary skill in the art. For example, Ar-LG may be a diaryltriazine compound having a chlorine reactive leaving group prepared from the reaction of an aromatic Grignard compound with 1 ,3,5-trichlorotriazine in a nucleophilic aromatic substitution reaction. Materials suitable for use in the electron injection layer are known in the art. Examples of suitable electron injection materials include, for example, 9, 10-di(naphthalene-2- yl)anthracene (ADN); metal chelated oxinoid compounds, such as bis(2-methyl-8- quinolinolato-N1 ,O8)-(1 , 1 '-biphenyl-4-olato)aluminum (BAIq),

berylliumbis(benzoquinolin-I O-olate) (Bebq2), bis(2-methyl-8-quinolinolato)(para- phenyl-phenolato)aluminum(lll), tris(8-hydroxyquinolato)aluminum (Alq3), (8- hydroxyquinolato)lithium (LiQ), and tetrakis(8-hydroxyquinolinato)zirconium; azole compounds, such as 1 ,3,5-tri(phenyl-2-benzimidazole)benzene, 3-(4-biphenylyl)-4- phenyl-5-tert-butylphenyl-1 ,2,4-triazole (TAZ), 4-(naphthalen-1 -yl)-3,5-diphenyl-4H- 1 ,2,4-triazole (NTAZ), and 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1 ,3,4-oxadiazole (tBu- PBD); quinoxaline derivatives such as 2,3-bis(4-fluorophenyl)quinoxaline;

phenanthroline derivatives such as 9, 10-diphenylphenanthroline, 4,7-diphenyl-1 ,10- phenanthroline (Bphen), 2,9-dimethyl-4,7-diphenyl-1 , 10-phenanthroline (BCP), and as well as mixtures thereof.

Other suitable materials for use in the electron injection layer include, but are not limited to, 5-(4,6-diphenyl-1 ,3,5-triazin-2-yl)-1 1 -phenyl-5, 1 1 -dihydroindolo[3,2-b]carbazole; 4- (3-(triphenylen-2-yl)phenyl)dibenzo[b,d]thiophene; imidazole derivatives, such as, for example, DMBI (2,3-dihydro-1 ,3-dimethyl-2-phenyl-1 H-benzo[d]imidazole), CI-DMBI (2- (2,4-dichlorophenyl)-2,3-dihydro-1 ,3-dimethyl-1 H-benzo[d]imidazole), N-DMBI (4-(2,3- dihydro-1 ,3-dimethyl-1 H-benzo[d]imidazol-2-yl)-N,N-dimethylbenzenamine), OH-DMBI (2-(2,3-dihydro-1 ,3-dimethyl-1 H-benzo[d]imidazol-2-yl)phenol); 2-(4-(9, 10- di(naphthalen-2-yl)anthracen-2-yl)phenyl)-1 -phenyl-1 H-benzo[d]imidazole, 2-(9, 10- di(naphthalen-2-yl)anthracen-2-yl)-1 -phenyl-1 H-benzo[d]imidazole, and 1 ,3,5-tri(1 - phenyl-1 H-benzo[d]imidazol-2-yl)phenyl (TPBi).

Further materials suitable for use in the electron injection layer include, but are not limited to, alkali metal salts, such as LiF, lithium quinolate (LiQ), Li₂O, NaCI, Cs₂CO₃, Li₂O, LiBO₂, K2S1O3, and Cs₂O. The electron transport layer, in addition to the spirobifluorene compound represented by general formula 1 or general formula 2, may further comprise other materials, such as, for example, the materials used in the electron injection layer described herein. Any of the materials described herein that are suitable for use in the electron injection and electron transport layers may be used singly or as a combination of two or more components.

In general, the emissive layer comprises a matrix material and an emitter compound. In the device of the present disclosure, the matrix material of the emissive layer is a substituted or unsubstituted spirobifluorene compound described herein.

In an embodiment, the emissive layer comprises a compound represented by general formula 1 or general formula 2, as described herein.

The substituted or unsubstituted spirobifluorene compound used in the emissive layer may be the same as or different from the substituted or unsubstituted spirobifluorene compound used in the electron transport layer. In an embodiment, the substituted or unsubstituted spirobifluorene compound used in the emissive layer is the same as the substituted or unsubstituted spirobifluorene compound used in the electron transport layer.

The emissive layer of the device of the present disclosure may further comprise materials useful in emissive layers, such as triphenylene derivatives, for example, those disclosed in U.S. Patent 8,652,652.

Emitter compounds useful in the emissive layer are known in the art and are available from commercial sources. In an embodiment, the emissive layer comprises an emitter compound having a LUMO energy of at least 1 .8 eV.

As used herein, and as would be generally understood by the ordinarily-skilled artisan, "HOMO" refers to highest occupied molecular orbital and "LUMO" refers to lowest unoccupied molecular orbital. A first HOMO or LUMO energy level is "greater than" or "higher than" a second HOMO or LUMO energy level if the first energy level is closer to the vacuum energy level. Since ionization potentials (IP) are measured as a negative energy relative to a vacuum level, a higher HOMO energy level corresponds to an IP having a smaller absolute value (an IP that is less negative). Similarly, a higher LUMO energy level corresponds to an electron affinity (EA) having a smaller absolute value (an EA that is less negative). On a conventional energy level diagram, with the vacuum level at the top, the LUMO energy level of a material is higher than the HOMO energy level of the same material. Herein, unless otherwise stated, the HOMO and LUMO energy will be given as an absolute value. Thus, for example, the phrase "a LUMO energy of at least 1 .8 eV" means 1 .8 eV or more below the vacuum level energy.

The HOMO and LUMO energy levels for organic materials to be used in OLEDs may be estimated according to methods known in the art. For example, two common methods for estimating HOMO and LUMO levels may be determined using solution

electrochemistry.

In determining HOMO and LUMO levels using solution electrochemistry, oxidation and reduction potentials are first obtained and then HOMO and LUMO energies are calculated from oxidation potential, in the case of HOMO energy, and reduction potential, in the case of LUMO energy, relative to a reference of known oxidation potential. Typically, the determination of oxidation and reduction potentials is done via cyclic voltammetry. Generally, the unknown is dissolved along with a high

concentration of electrolyte. Electrodes are inserted and the voltage scanned in either the positive or negative direction (depending on whether an oxidation or reduction is being performed). The presence of a redox reaction is indicated by current flowing through the cell. The voltage scan is then reversed and the redox reaction is reversed. If the areas of the two redox waves are the same the process was reversible. The potential at which these events occur give the value of the reduction or oxidation potential relative to a reference. The reference can be an external electrode, such as Ag/AgCI or SCE, or it can be an internal one, such as ferrocene, which has a known oxidation potential.

HOMO and LUMO energies of some emitter compounds may be found in reference texts known to those of ordinary skill in the art, such as, for example, "Highly Efficient OLEDs with Phosphoresent Materials" Hartmut Yersin, ed. (2008, Wiley-VCH,

Weinheim).

In an embodiment, the emitter compound has a LUMO energy of at least 1 .9 eV, at least 2.0 eV, at least 2.1 eV, at least 2.2 eV, at least 2.3 eV, at least 2.4 eV, at least 2.5 eV, at least 2.6 eV, at least 2.7 eV, or at least 2.8 eV.

In an embodiment, the emitter compound has a LUMO energy of at least 2.1 eV, typically at least 2.2 eV.

In an embodiment, the emitter compound is a compound represented by the formula lr(L1 )x(L2)_3-x, wherein L1 is an ancillary ligand and L2 is a ligand represented by the structure

wherein R₂, R3, R₄, R5, R6, R7, Rs, and R₉ are each, independently, H, halogen, cyano, or alkyl; and x is an integer from 0 to 3.

Ancillary ligands suitable for use according to the present disclosure are typically bidentate ligands. Ancillary ligands may be selected from the group consisting of acetylacetonate, picolinate, substituted picolinate, hexafluoroacetylacetonate, salicylidene, 8-hydroxyquinolinate; amino acids, salicylaldehydes, iminoacetonates, ethylene diamine derivatives, amidinate, biphenyl, bipyridyl, phenylpyridyl, 2-(1 - naphthyl)benzoxazole, 2-phenylbenzoxazole, 2-phenylbenzothiazole, coumarin, thienylpyridine, benzothienylpyridine, thienylpyridine, tolylpyridine, phenylimines, vinylpyridines, arylquinolines, pyndylnaphthalenes, pyridylpyrroles, pyridylimidazoles, phenylindoles, and derivatives thereof.

In an embodiment, the emitter does not comprise any ancillary ligands wherein x is 0.

In another embodiment, each occurrence of L2 is represented by the structure

Examples of suitable emitter compounds include, but are not limited to, tris(2- phenylpyridine)iridium(lll) (also referred to as lr(ppy)₃); tris[2-(4,6- difluorophenyl)pyridinato-C²,N]iridium(lll) (also referred to as lr(dfppy)₃); bis(3,5-difluoro- 4-cyano-2-(2-pyridyl)phenyl-(2-carboxypyridyl)iridium(lll) (also referred to as FCNIrPic); bis[2-(4,6-difluorophenyl)pyridinato-C²,N](picolinato)iridium(lll) (also referred to as FlrPic), and iridium (III) tris(2-(4-tolyl)pyridinato-N,C2') (also referred to as lr(mppy)₃). The ordinarily-skilled artisan would recognize that the ligands of such suitable emitter compounds may be in the facial (fac) or meridianal (mer) configurations, both of which are contemplated in the present disclosure.

The emitter compounds suitable for use according to the present disclosure may be obtained from commercial sources or synthesized according to methods known to those of ordinary skill in the art. For example, lr(ppy)₃, lr(mppy)₃, lr(dfppy)₃ and FlrPic are available from American Dye Source, Inc. (Quebec, Canada) and FCNIrPic is available from Lumtec (Taiwan, ROC).

The emissive layer may further comprise other light emitters that are known in the art and are commercially available. Such light emitter include various conducting polymers as well as organic molecules, such as compounds available from Sumation, Merck Yellow, Merck Blue, American Dye Source, Kodak (e.g., A1 Q3 and the like), and even Aldrich, such as BEHP-PPV. Examples of such organic electroluminescent compounds include: (i) poly(p-phenylene vinylene) and its derivatives substituted at various positions on the phenylene moiety; (ii) poly(p-phenylene vinylene) and its derivatives substituted at various positions on the vinylene moiety;

(iii) poly(p-phenylene vinylene) and its derivatives substituted at various positions on the phenylene moiety and also substituted at various positions on the vinylene moiety;

(iv) poly(arylene vinylene), where the arylene may be such moieties as naphthalene, anthracene, furylene, thienylene, oxadiazole, and the like;

(v) derivatives of poly(arylene vinylene), where the arylene may be as in (iv) above, and additionally have substituents at various positions on the arylene;

(vi) derivatives of poly(arylene vinylene), where the arylene may be as in (iv) above, and additionally have substituents at various positions on the vinylene; (vii) derivatives of poly(arylene vinylene), where the arylene may be as in (iv) above, and additionally have substituents at various positions on the arylene and substituents at various positions on the vinylene;

(viii) co-polymers of arylene vinylene oligomers, such as those in (iv), (v), (vi), and (vii) with non-conjugated oligomers; and

(ix) poly(p-phenylene) and its derivatives substituted at various positions on the phenylene moiety, including ladder polymer derivatives such as poly(9,9-dialkyl fluorene) and the like; (x) poly(arylenes) where the arylene may be such moieties as naphthalene, anthracene, furylene, thienylene, oxadiazole, and the like; and their derivatives substituted at various positions on the arylene moiety; (xi) co-polymers of oligoarylenes, such as those in (x) with non-conjugated oligomers;

(xii) polyquinoline and its derivatives;

(xiii) co-polymers of polyquinoline with p-phenylene substituted on the phenylene with, for example, alkyl or alkoxy groups to provide solubility; and

(xiv) rigid rod polymers, such as poly(p-phenylene-2,6-benzobisthiazole), poly(p- phenylene-2,6-benzobisoxazole), poly(p-phenylene-2,6-benzimidazole), and their derivatives;

(xv) polyfluorene polymers and co-polymers with polyfluorene units.

Suitable organic emissive polymers include SUMATION Light Emitting Polymers

("LEPs") that emit green, red, blue, or white light or their families, copolymers, derivatives, or mixtures thereof. SUMATION LEPs are available from Sumation KK. Other polymers include polyspirofluorene-like polymers available from Covion Organic Semiconductors GmbH, Frankfurt, Germany (now owned by Merck®).

Alternatively, rather than polymers, the emissive layer of the device according to the present disclosure may further comprise small organic molecules that emit by

fluorescence or by phosphorescence. Examples of small-molecule organic

electroluminescent compounds include: (i) tris(8-hydroxyquinolinato) aluminum (Alq); (ii) 1 ,3-bis(N,N-dimethylaminophenyl)-1 ,3,4-oxidazole (OXD-8); (iii) -oxo-bis(2-methyl-8- quinolinato)aluminum; (iv) bis(2-methyl-8-hydroxyquinolinato) aluminum; (v) bis(hydroxybenzoquinolinato) beryllium (BeQ₂); (vi) bis(diphenylvinyl)biphenylene (DPVBI); (vii) arylamine-substituted distyrylarylene (DSA amine).

Such polymer and small-molecule compounds are well known in the art and are described in, for example, U.S. Patent 5,047,687.

The weight ratio of the substituted or unsubstituted spirobifluorene compound, typically a compound of formula 1 or formula 2, to the emitter compound in the emissive layer may be measured and controlled. The weight ratio of the substituted or unsubstituted spirobifluorene compound to the emitter compound is 50:50, typically 80:20, more typically 90: 10, even more typically 92:8, in the emissive layer of the device according to the present disclosure.

The hole injection layer plays a role in efficiently injecting the holes that have been transferred from the anode into the emissive layer or the hole transport layer. The hole transport layer plays a role in efficiently transporting the holes that have been injected from the anode or the holes that have been injected from the anode through the hole injection layer to the emissive layer. The hole injection/transport material needs to efficiently inject/transport the holes from the positive electrode between the electrodes to which an electric field has been provided, and it is desirable that the hole injection efficiency is high and the injected holes are efficiently transported. In an embodiment, the hole injection layer comprises a polythiophene comprising a repeating unit complying with formula (I)

wherein R-n and R₁₂ are each, independently, H, alkyl, fluoroalkyl, alkoxy, aryloxy, or -

0-[Z-0]_a-R_e;

wherein

Z is an optionally halogenated hydrocarbylene group,

a is equal to or greater than 1 , and

R_e is H, alkyl, fluoroalkyl, or aryl. In an embodiment, R-n and Ri₂ are each, independently, H, fluoroalkyl, -0[C(R_aRb)- C(R_cRd)-0]a-R_e, -ORf; wherein each occurrence of R_a, Rb, R_c, and R_d, are each, independently, H, halogen, alkyl, fluoroalkyl, or aryl; R_e is H, alkyl, fluoroalkyl, or aryl; a is 1 , 2, or 3; and R_f is alkyl, fluoroalkyl, or aryl. In an embodiment, R-n is H and Ri₂ is other than H. In such an embodiment, the repeating unit is derived from a 3-substituted thiophene.

In another embodiment, Ri₂ -0[C(R_aRb)-C(R_cRd)-0]a-Re, or -ORf, typically Ri₂ is - 0[C(R_aRb)-C(R_cRd)-0]a-Re.

In an embodiment, each occurrence of R_a, Rb, R_c, and R_d, are each, independently, H, (Ci-C8)alkyl, (Ci-C8)fluoroalkyl, or phenyl; and R_e is (Ci-C8)alkyl, (Ci-C8)fluoroalkyl, or phenyl. In an embodiment, Ri₂ is -0[CH₂-CH₂-0]_a-R_e- In another embodiment, Ri₂ is - 0[CH(CH₃)-CH₂-0]a-R_e. In an embodiment, R_e is methyl, propyl, or butyl.

The polythiophene can be a regiorandom or a regioregular compound. Due to its asymmetrical structure, the polymerization of 3-substituted thiophenes produces a mixture of polythiophene structures containing three possible regiochemical linkages between repeat units. The three orientations available when two thiophene rings are joined are the 2,2'; 2,5', and 5,5' couplings. The 2,2' (or head-to-head) coupling and the 5,5' (or tail-to-tail) coupling are referred to as regiorandom couplings. In contrast, the 2,5' (or head-to-tail) coupling is referred to as a regioregular coupling. The degree of regioregularity can be, for example, about 0 to 100%, or about 25 to 99.9%, or about 50 to 98%. Regioregularity may be determined by standard methods known to those of ordinary skill in the art, such as, for example, using NMR spectroscopy. In an embodiment, the polythiophene is regioregular. In some embodiments, the regioregularity of the polythiophene can be at least about 85%, typically at least about 95%, more typically at least about 98%. In some embodiments, the degree of regioregularity can be at least about 70%, typically at least about 80%. In yet other embodiments, the regioregular polythiophene has a degree of regioregularity of at least about 90%, typically a degree of regioregularity of at least about 98%.

3-substituted thiophene monomers, including polymers derived from such monomers, are commercially-available or may be made by methods known to those of ordinary skill in the art. Synthetic methods, doping, and polymer characterization, including regioregular polythiophenes with side groups, is provided in, for example, U.S. Patent No. 6,602,974 to McCullough et al. and U.S. Patent No. 6, 166, 172 to McCullough et al.

In an embodiment, R-n and R ₂ are both other than H. In such an embodiment, the repeating unit is derived from a 3,4-disubstituted thiophene. In an embodiment, R-n and R12 are each, independently, -0[C(R_aRb)-C(R_cRd)-0]a-Re, or -ORf. In another embodiment, R-n and R12 are each, independently, -0[C(R_aR_b)- C(R_cRd)-0]a-R_e- Rii and R ₂ may be the same or different. In an embodiment, each occurrence of R_a, R_b, R_c, and R_d, are each, independently, H, (Ci-C8)alkyl, (Ci-C8)fluoroalkyl, or phenyl; and R_e is (Ci-C8)alkyl, (Ci-C8)fluoroalkyl, or phenyl.

In an embodiment, R-n and R12 are each -0[CH₂-CH₂-0]_a-R_e. In another embodiment, Rn and R₁₂ are each -0[CH(CH₃)-CH₂-0]_a-R_e.

In an embodiment, R_e is methyl, propyl, or butyl.

3,4-disubstituted thiophene monomers, including polymers derived from such

monomers, are commercially-available or may be made by methods known to those of ordinary skill in the art. For example, a 3,4-disubstituted thiophene monomer may be produced by reacting 3,4-dibromothiophene with the metal salt, typically sodium salt, of a compound given by the formula HO-[Z-0]_a-R_e or HORf, wherein Z, R_e, Rf and a are as defined herein.

The polymerization of 3,4-disubstituted thiophene monomers may be carried out by, first, brominating the 2 and 5 positions of the 3,4-disubstituted thiophene monomer to form the corresponding 2,5-dibromo derivative of the 3,4-disubstituted thiophene monomer. The polymer can then be obtained by GRIM (Grignard methathesis) polymerization of the 2,5-dibromo derivative of the 3,4-disubstituted thiophene in the presence of a nickel catalyst. Such a method is described, for example, in US Patent 8,865,025, the entirety of which is hereby incorporated by reference. Another known method of polymerizing thiophene monomers is by oxidative polymerization using organic non-metal containing oxidants, such as 2,3-dichloro-5,6-dicyano-1 ,4- benzoquinone (DDQ), or using a transition metal halide, such as, for example, iron(lll) chloride, molybdenum(V) chloride, and ruthenium(lll) chloride, as oxidizing agent.

Examples of compounds having the formula HO-[Z-0]_a- _e or HOR_f that may be converted to the metal salt, typically sodium salt, and used to produce 3,4-disubstituted thiophene monomers include, but are not limited to, trifluoroethanol, ethylene glycol monohexyl ether (hexyl Cellosolve), propylene glycol monobutyl ether (Dowanol PnB), diethylene glycol monoethyl ether (ethyl Carbitol), dipropylene glycol n-butyl ether (Dowanol DPnB), diethylene glycol monophenyl ether (phenyl Carbitol), ethylene glycol monobutyl ether (butyl Cellosolve), diethylene glycol monobutyl ether (butyl Carbitol), dipropylene glycol monomethyl ether (Dowanol DPM), diisobutyl carbinol, 2-ethylhexyl alcohol, methyl isobutyl carbinol, ethylene glycol monophenyl ether (Dowanol Eph), propylene glycol monopropyl ether (Dowanol PnP), propylene glycol monophenyl ether (Dowanol PPh), diethylene glycol monopropyl ether (propyl Carbitol), diethylene glycol monohexyl ether (hexyl Carbitol), 2-ethylhexyl carbitol, dipropylene glycol monopropyl ether (Dowanol DPnP), tripropylene glycol monomethyl ether (Dowanol TPM), diethylene glycol monomethyl ether (methyl Carbitol), and tripropylene glycol monobutyl ether (Dowanol TPnB). In an embodiment, the polythiophene comprises a repeating unit selected from the group consisting of

—

and combinations thereof.

It would be understood by the ordinarily-skilled artisan that the repeating unit

is derived from a monomer represented by the structure

3-(2-(2-methoxyethoxy)ethoxy)thiophene [referred to herein as 3-MEET]; and the repeating unit

is derived from a monomer represented by the structure

3,4-bis(2-(2-butoxyethoxy)ethoxy)thiophene [referred to herein as 3,4-diBEET].

The polythiophene having a repeating unit complying with formula (I) in the hole injection layer may be further modified subsequent to its formation by polymerization. For instance, polythiophenes having one or more repeating units derived from 3- substituted thiophene monomers may possess one or more sites where hydrogen may be replaced by a substituent, such as a sulfonic acid group (-S0₃H) by sulfonation.

As used herein, the term "sulfonated" in relation to the polythiophene polymer means that the polythiophene comprises one or more sulfonic acid groups (-SO3H). The sulfur atom of the -SO3H group may be directly bonded to the backbone of the polythiophene polymer and/or to a side group. For the purpose of the present disclosure, a side group is a monovalent radical that when theoretically or actually removed from the polymer does not shorten the length of the polymer chain. Typically, the sulfur atom of the - SO3H group is directly bonded to the backbone of the polythiophene polymer and not to a side group. The sulfonated polythiophene polymer and/or copolymer may be made using any method known to those of ordinary skill in the art. For example, the polythiophene may be sulfonated by reacting the polythiophene with a sulfonating reagent such as, for example, fuming sulfuric acid, acetyl sulfate, pyridine SO3, or the like. In another example, monomers may be sulfonated using a sulfonating reagent and then polymerized according to known methods and/or methods described herein. It would be understood by the ordinarily-skilled artisan that sulfonic acid groups in the presence of a basic compound, for example, alkali metal hydroxides, ammonia, and alkylamines, such as, for example, mono-, di-, and trialkylamines, such as, for example, triethylamine, may result in the formation of the corresponding salt or adduct. Thus, the term "sulfonated" in relation to the polythiophene polymer includes the meaning that the polythiophene may comprise one or more -SO3M groups, wherein M may be an alkali metal ion, such as, for example, Na⁺, Li⁺, K⁺, Rb⁺, Cs⁺; ammonium (NH₄ ⁺), mono-, di-, and trialkylammonium, such as triethylammonium.

The sulfonation of conjugated polymers and sulfonated conjugated polymers, including sulfonated polythiophenes, are described in U.S. Patent No. 8,017,241 to Seshadri et al., which is incorporated herein by reference in its entirety.

In an embodiment, the polythiophene is sulfonated.

In an embodiment, the polythiophene is sulfonated poly(3-MEET). The polythiophene polymers suitable for use according to the present disclosure may be homopolymers or copolymers, including statistical, random, gradient, and block copolymers. For a polymer comprising a monomer A and a monomer B, block copolymers include, for example, A-B diblock copolymers, A-B-A triblock copolymers, and -(AB)n-multiblock copolymers. The polythiophene may comprise repeating units derived from other types of monomers such as, for example, thienothiophenes, selenophenes, pyrroles, furans, tellurophenes, anilines, arylamines, and arylenes, such as, for example, phenylenes, phenylene vinylenes, and fluorenes.

In an embodiment, the polythiophene comprises repeating units complying with formula (I) in an amount of greater than 50% by weight, typically greater than 80% by weight, more typically greater than 90% by weight, even more typically greater than 95% by weight, based on the total weight of the repeating units.

It would be clear to a person of ordinary skill in the art that, depending on the purity of the starting monomer compound(s) used in the polymerization, the polymer formed may contain repeating units derived from impurities. As used herein, the term

"homopolymer" is intended to mean a polymer comprising repeating units derived from one type of monomer, but may contain repeating units derived from impurities. In an embodiment, the polythiophene is a homopolymer wherein essentially all of the repeating units are repeating units complying with formula (I).

The polythiophene polymer typically has a number average molecular weight between about 1 ,000 and 1 ,000,000 g/mol. More typically, the conjugated polymer has a number average molecular weight between about 5,000 and 100,000 g/mol, even more typically about 10,000 to about 50,000 g/mol. Number average molecular weight may be determined according to methods known to those of ordinary skill in the art, such as, for example, by gel permeation chromatography.

The hole injection layer in the organic light-emitting device of the present disclosure may optionally further comprise hole carrier compounds known to be useful for hole injection/transport. The term "hole carrier compound" refers to any compound that is capable of facilitating the movement of holes, i.e., positive charge carriers, and/or blocking the movement of electrons, for example, in an electronic device. Suitable hole carrier compounds include, for example, low molecular weight compounds or high molecular weight compounds. The optional hole carrier compounds may be non- polymeric or polymeric. Non-polymeric hole carrier compounds include, but are not limited to, cross-linkable and non-crosslinked small molecules. Examples of non- polymeric hole carrier compounds include, but are not limited to, N,N'-bis(3- methylphenyl)-N,N'-bis(phenyl)benzidine (CAS # 65181 -78-4); N,N'-bis(4- methylphenyl)-N,N'-bis(phenyl)benzidine; N,N'-bis(2-naphtalenyl)-N-N'- bis(phenylbenzidine) (CAS # 139255-17-1 ); 1 ,3,5-tris(3-methyldiphenylamino)benzene (also referred to as m-MTDAB); N,N'-bis(1 -naphtalenyl)-N,N'-bis(phenyl)benzidine (CAS # 123847-85-8, NPB); 4,4',4"-tris(N,N-phenyl-3- methylphenylamino)triphenylamine (also referred to as m-MTDATA, CAS # 124729-98- 2); 4,4',N,N'-diphenylcarbazole (also referred to as CBP, CAS # 58328-31 -7); 1 ,3,5- tris(diphenylamino)benzene; 1 ,3,5-tris(2-(9-ethylcarbazyl-3)ethylene)benzene; 1 ,3,5- tris[(3-methylphenyl)phenylamino]benzene; 1 ,3-bis(N-carbazolyl)benzene; 1 ,4-bis( diphenylamino)benzene; 4,4'-bis(N-carbazolyl)-1 , 1 '-biphenyl; 4,4'-bis(N-carbazolyl)-1 , 1 '- biphenyl; 4-(dibenzylamino)benzaldehyde-N,N-diphenylhydrazone; 4- (diethylamino)benzaldehyde diphenylhydrazone; 4-(dimethylamino)benzaldehyde diphenylhydrazone; 4-(diphenylamino)benzaldehyde diphenylhydrazone; 9-ethyl-3- carbazolecarboxaldehyde diphenylhydrazone; copper(ll) phthalocyanine; N,N'-bis(3- methylphenyl)-N,N'-diphenylbenzidine; N, N'-di-[(1 -naphthyl)-N,N'-diphenyl]-1 , 1 '- biphenyl)-4,4'-diamine; N,N'-diphenyl-N,N'-di-p-tolylbenzene-1 ,4-diamine; tetra-N- phenylbenzidine; titanyl phthalocyanine; tri-p-tolylamine; tris(4-carbazoyl-9- ylphenyl)amine (TCTA); and tris[4-( diethylamino)phenyl]amine.

Optional polymeric hole carrier compounds include, but are not limited to, poly[(9,9- dihexylfluorenyl-2,7-diyl)-alt-co-(N,N'bis{p-butylphenyl}-1 ,4-diaminophenylene)];

poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(N,N'-bis{p-butylphenyl}-1 , 1 '-biphenylene-4,4'- diamine)]; poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) (also referred to as TFB) and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine] (commonly referred to as poly-TPD). Other optional hole carrier compounds are described in, for example, US Patent Publications 2010/0292399 published Nov. 18, 2010; 2010/010900 published May 6, 2010; and 2010/ 0108954 published May 6, 2010. Optional hole carrier compounds described herein are known in the art and are commercially available.

In an embodiment, the polythiophene comprising a repeating unit complying with formula (I) in the hole injection layer may be doped. In such an embodiment, the hole injection layer further comprises a dopant. As used herein, the term "doped" in reference to the polythiophene comprising a repeating unit complying with formula (I) means that the polythiophene has undergone a chemical transformation, typically an oxidation or reduction reaction, more typically an oxidation reaction, facilitated by a dopant. As used herein, the term "dopant" refers to a substance that oxidizes or reduces, typically oxidizes, the polythiophene polymer.

Herein, the process in which the polythiophene undergoes a chemical transformation, typically an oxidation or reduction reaction, more typically an oxidation reaction, facilitated by a dopant is called a "doping reaction" or simply "doping". Doping alters the properties of the polythiophene polymer, which properties may include, but may not be limited to, electrical properties, such as resistivity and work function, mechanical properties, and optical properties. In the course of a doping reaction, the hole-carrying polythiophene becomes charged, and the dopant, as a result of the doping reaction, becomes the oppositely-charged counterion for the doped compound. As used herein, a substance must chemically react, oxidize or reduce, typically oxidize, the

polythiophene to be referred to as a dopant. Substances that do not react with the polythiophene but may act as counterions are not considered dopants according to the present disclosure. Accordingly, the term "undoped" in reference to the polythiophene polymer means that the polythiophene has not undergone a doping reaction as described herein. In the case in which the polythiophene polymer is sulfonated, such sulfonated polythiophenes are typically known to be "self-doped" and do not require doping by an externally-added dopant. Thus, in an embodiment, the hole injection layer is free of externally-added dopant.

Dopants are known in the art. See, for example, U.S. Patent 7,070,867; US Publication 2005/0123793; and US Publication 2004/01 13127. The dopant can be an ionic compound. The dopant can comprise a cation and an anion. One or more dopants may be used to dope the polythiophene comprising a repeating unit complying with formula (I). The cation of the ionic compound can be, for example, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Ta, W, Re, Os, Ir, Pt, or Au.

The cation of the ionic compound can be, for example, gold, molybdenum, rhenium, iron, and silver cation.

In some embodiments, dopants may comprise sulfonylimides, such as, for example, bis(trifluoromethanesulfonyl)imide; antimonates, such as, for example,

hexafluoroantimonate; arsenates, such as, for example, hexafluoroarsenate;

phosphorus compounds, such as, for example, hexafluorophosphate; and borates, such as, for example, tetrafluoroborate, tetraarylborates, and trifluoroborates. Examples of tetraary I borates include, but are not limited to, halogenatedtetraarylborates, such as tetrakispentafluorophenylborate (TPFB). Examples of trifluoroborates include, but are not limited to, (2-nitrophenyl)trifluoroborate, benzofurazan-5-trifluoroborate, pyrimidine- 5-trifluoroborate, pyridine-3-trifluoroborate, and 2,5-dimethylthiophene-3-trifluoroborate.

In an embodiment, the dopant comprises a tetraarylborate.

In one embodiment the dopant may be a silver salt comprising a tetraarylborate, typically a halogenatedtetraarylborate. In an embodiment, the dopant comprises tetrakis(pentafluorophenyl)borate (TPFB).

In an embodiment, the dopant is silver tetrakis(pentafluorophenyl)borate. The hole injection layer of the device of the present disclosure may optionally further comprise one or more matrix compounds known to be useful in hole injection layers or hole transport layers.

The matrix compound can be, for example, a synthetic polymer that is different from the polythiophene. See, for example, US Patent Publication No. 2006/0175582 published Aug. 10, 2006. The synthetic polymer can comprise, for example, a carbon backbone. In some embodiments, the synthetic polymer has at least one polymer side group comprising an oxygen atom or a nitrogen atom. The synthetic polymer may be a Lewis base. Typically, the synthetic polymer comprises a carbon backbone and has a glass transition temperature of greater than 25 °C. The synthetic polymer may also be a semi-crystalline or crystalline polymer that has a glass transition temperature equal to or lower than 25 °C and/or a melting point greater than 25 °C. The synthetic polymer may comprise one or more acidic groups, for example, sulfonic acid groups. In an embodiment, the hole injection layer comprises a synthetic polymer, wherein the synthetic polymer is a polymeric acid comprising a repeating unit complying with formula (II) and a repeating unit complying with formula (III)

wherein

each occurrence of R-|₃, R-|₄, Ri₅, Ri₆, R17, R18, and R19 is, independently, H, halogen, fluoroalkyl, or perfluoroalkyl; and

X10 is -[OC(R_hRi)-C(RjR_k)]_b-0-[CR|R_m]c-S0₃H,

wherein each occurrence of R_h, Rj, R_j, Rk, Ri and R_m is, independently, H, halogen, fluoroalkyl, or perfluoroalkyl;

b is 0 to 10; and

c is 1 -5.

In an embodiment, each occurrence of R-13, Ri₄, R-1 5, and Ri₆ is F.

In an embodiment, each occurrence of R-17, Ri₈, and R-19 is F.

In an embodiment, each occurrence of R_h and Rj is F; R_j is (Ci-C8)perfluoroalkyl; R_k, Ri and R_m are each F.

Such polymeric acids are, for instance, those marketed by E. I. DuPont under the trade name NAFION®, those marketed by Solvay Specialty Polymers under the trade name AQUIVION®, or those marketed by Asahi Glass Co. under the trade name FLEMION®.

The optional matrix compound can be a planarizing agent. A matrix compound or a planarizing agent may be comprised of, for example, a polymer or oligomer such as an organic polymer, such as poly(styrene) or poly(styrene) derivatives; polyvinyl acetate) or derivatives thereof; poly(ethylene glycol) or derivatives thereof; poly(ethylene-co-vinyl acetate); poly(pyrrolidone) or derivatives thereof (e.g., poly(1 -vinylpyrrolidone-co-vinyl acetate)); polyvinyl pyridine) or derivatives thereof; poly(methyl methacrylate) or derivatives thereof; poly(butyl acrylate); poly(aryl ether ketones); poly(aryl sulfones); poly(esters) or derivatives thereof; or combinations thereof. In an embodiment, the matrix compound is poly(styrene) or poly(styrene) derivative.

In an embodiment, the matrix compound is poly(4-hydroxystyrene).

The hole transport layer of the device according to the present disclosure may comprise one or more hole carrier molecules and/or polymers. Commonly used hole carrier molecules include, but are not limited to: 4,4',4"-tris(N,N-diphenyl-amino)- triphenylamine, 4,4',4"-tris(N-3-methylphenyl-N-phenyl-amino)-triphenylamine, Ν,Ν'- diphenyl-N,N'-bis(3-methylphenyl)-(1 ,1 '-biphenyl)-4,4'-diamine, 1 ,1 -bis((di-4- tolylamino)phenyl)cyclohexane, N,N'-bis(4-methylphenyl)-N,N'-bis(4-ethylphenyl)-(1 , 1 '- (3,3'-dimethyl)biphenyl)-4,4'-diamine, tetrakis-(3-methylphenyl)-N,N,N',N'-2,5- phenylenediamine, a-phenyl-4-N,N-diphenylaminostyrene, p- (diethylamino)benzaldehyde diphenylhydrazone, triphenylamine, bis(4-(N,N- diethylamino)-2-methylphenyl)(4-methylphenyl)methane, 1 -phenyl-3-(p- (diethylamino)styryl)-5-(p-(diethylamino)phenyl)pyrazoline, 1 ,2-trans-bis(9H-carbazol-9- yl)cyclobutane, N,N,N',N'-tetrakis(4-methylphenyl)-(1 , 1 '-biphenyl)-4,4'-diamine, Ν,Ν'- bis(naphthalen-1 -yl)-N,N'-bis-(phenyl)benzidine, 2,7-di-9H-carbazol-9-yl-9,10-dihydro- 9,9-dimethyl-10-phenyl-acridine (CAS # 1639425-16-3), N-([1 ,1 '-biphenyl]-4-yl)-9,9- dimethyl-N-(4-(9-phenyl-9H-carbazol-3-yl)phenyl)-9H-fluoren-2-amine (CAS # 1242056- 42-3), and porphyrinic compounds, such as copper phthalocyanine. Commonly used hole carrier polymers include, but are not limited to, polyvinylcarbazole,

(phenylmethyl)polysilane, poly(dioxythiophenes), polyanilines, and polypyrroles.

In an embodiment, the hole transport layer comprises a compound selected from the group consisting of 2,7-di-9H-carbazol-9-yl-9, 10-dihydro-9,9-dimethyl-10-phenyl- acridine (CAS # 1639425-16-3), N-d^ -bipheny^-y -g^-dimethyl-NWS-phenyl-SH- carbazol-3-yl)phenyl)-9H-fluoren-2-amine (CAS # 1242056-42-3), and a mixture thereof.

The substrate of the organic light-emitting device can be flexible or rigid, organic or inorganic. Suitable substrate compounds include, for example, glass, including, for example, display glass, ceramic, metal, and plastic films. In an embodiment, the substrate is glass.

The anode may itself be a single layer or multilayer structure. Suitable anode materials include, but are not limited to, metal, mixed metal, alloy, metal oxide, and mixed oxide. Suitable materials include the mixed oxides of the Group 2 elements (i.e., Be, Mg, Ca, Sr, Ba, Ra), the Group 1 1 elements, the elements in Groups 4, 5, and 6, and the Group 8-10 transition elements. Mixed oxides of Groups 12, 13 and 14 elements, such as indium-tin-oxide (ITO), may be used. As used herein, the phrase "mixed oxide" refers to oxides having two or more different cations selected from the Group 2 elements or the Groups 12, 13, or 14 elements. Some non-limiting, specific examples of materials for the anode include, but are not limited to, indium-tin-oxide, indium-zinc-oxide, aluminum-tin-oxide, gold, silver, copper, and nickel. Typically, the anode is ITO. The cathode layer can be any metal or nonmetal having a lower work function than anode layer. Materials suitable for use as the cathode layer are known in the art and include, for example, alkali metals of Group 1 , such as Li, Na, K, Rb, and Cs, Group 2 metals, such as, Mg, Ca, Ba, Group 12 metals, lanthanides such as Ce, Sm, and Eu, and actinides, as well as aluminum, indium, yttrium, and combinations of any such materials. Specific non-limiting examples of materials suitable for the cathode include, but are not limited to, barium, lithium, cerium, cesium, europium, rubidium, yttrium, magnesium, samarium, and alloys and combinations thereof.

The organic light-emitting device of the present disclosure may be encapsulated to prevent entry of undesirable components, such as water and oxygen, using any method known to a person of ordinary skill. For example, the devices described herein may be encapsulated using securing a capglass onto the device using glue, such as, for example, UV-curable epoxy, under inert atmosphere. It is understood that the organic light-emitting device of the present disclosure may comprise additional layers, such as interfacial modification layers, for example, interlayers, and other hole transport, hole injection, electron transport, and electron injection layers. Other layers that are known in the art or otherwise may be used. In addition, any of the above-described layers may comprise two or more sub-layers or may form a laminar structure. Alternatively, some or all of the anode layer, hole transport layer, electron transport layer, cathode layer, and any additional layers, such as, for example, hole injection layer and electron injection layer may be treated, especially surface treated, to increase charge carrier transport efficiency or other physical properties of the devices. The choice of materials for each of the component layers is preferably determined by balancing the goals of providing a device with high device efficiency with device operational lifetime considerations, fabrication time and complexity factors and other considerations appreciated by persons skilled in the art. It will be appreciated that determining optimal components, component configurations, and compositional identities would be routine to those of ordinary skill of in the art.

The various layers of the electronic device can be formed by any conventional deposition technique, including vapor deposition, liquid deposition (continuous and discontinuous techniques), and thermal transfer. Chemical vapor deposition may be performed as a plasma-enhanced chemical vapor deposition ("PECVD") or metal organic chemical vapor deposition ("MOCVD"). Physical vapor deposition can include vacuum thermal evaporation (sublimation) and all forms of sputtering, including ion beam sputtering, as well as e-beam evaporation and resistance evaporation. Specific forms of physical vapor deposition include radio frequency magnetron sputtering and inductively-coupled plasma physical vapor deposition ("IMP- PVD"). These deposition techniques are well known within the semiconductor fabrication arts.

Continuous deposition techniques, include but are not limited to, spin coating, gravure coating, curtain coating, dip coating, slot-die coating, spray coating, and continuous nozzle coating. Discontinuous deposition techniques include, but are not limited to, ink jet printing, gravure printing, and screen printing. Other layers in the device can be made of any materials which are known to be useful in such layers upon consideration of the function to be served by such layers.

The techniques used for the formation of each layer in the organic light-emitting device may be determined by the ordinarily-skill artisan. Multiple techniques may be used to form the layers of the organic light-emitting device. For example, one or more layers may be formed by a physical vapor deposition process, such as vacuum thermal evaporation (sublimation), while one or more other layers are formed from a solution or ink using a solution process such as spin coating, gravure coating, curtain coating, dip coating, slot-die coating, spray coating, and continuous nozzle coating.

Methods are known in the art and can be used to fabricate organic electronic devices including, for example, OLED and OPV devices. Methods known in the art can be used to measure brightness, efficiency, and lifetimes. Organic light emitting diodes (OLED) are described, for example, in U.S. Patents 4,356,429 and 4,539,507 (Kodak).

Conducting polymers which emit light are described, for example, in U.S. Patents 5,247, 190 and 5,401 ,827 (Cambridge Display Technologies). Device architecture, physical principles, solution processing, multilayering, blends, and compounds synthesis and formulation are described in Kraft et al., "Electroluminescent Conjugated Polymers— Seeing Polymers in a New Light," Angew. Chem. Int. Ed., 1998, 37, 402- 428, which is hereby incorporated by reference in its entirety. The devices, methods, and processes according to the present disclosure are further illustrated by the following non-limiting examples.

Examples

The components used in the following examples are summarized in the following Table 1 .

Table 1 . Summary of components

HT1

2,7-di-9H-carbazol-9-yl-9, 10-dihydro-9,9-dimethyl-10- phenyl-acridine

HT2

N-([1 , 1 '-biphenyl]-4-yl)-9,9-dimethyl-N-(4-(9-phenyl- 9H-carbazol-3-yl)phenyl)-9H-fluoren-2-amine

NPB N,N'-bis(1 -naphtalenyl)-N,N'-bis(phenyl)benzidine

Alq₃ tris(8-hydroxyquinolato)aluminum

LiQ (8-hydroxyquinolinolato)lithium

Hole injection layer comprising sulfonated poly(3-

HIL1

MEET), poly(4-hydroxystyrene), and NAFION®

GH1 Hydrocarbon-based matrix

E1 Iridium-based emitter

Example 1. Synthesis of 1 -(9,9'-spirobi[9H-fluoren]-3-yl)-3,5-diphenyl-1,3,5- triazine (H1) Cyanuric chloride was combined with 2 molar equivalents of phenyl magnesium bromide in tetrahydrofuran at -40 °C. The temperature was slowly allowed to warm to room temperature and the reaction was allowed to react for 4 hours. The disubstituted product, 2-chloro-4,6-diphenyl-1 ,3,5-triazine, was isolated in 74% yield.

Spirobifluorene boronic ester, 2-(9,9'-spirobi[fluoren]-3-yl)-4,4,5,5-tetramethyl-1 ,3,2- dioxaborolane, was reacted with 2-chloro-4,6-diphenyl-1 ,3,5-triazine in the presence of Pd(OAc)₂ and P(o-tolyl)₃ in a solvent mixture of water, toluene, and dioxane at reflux for 24 hours in a Suzuki coupling reaction. The desired compound, 1 -(9,9'-spirobi[9H- fluoren]-3-yl)-3,5-diphenyl-1 ,3,5-triazine (H1 ), was isolated in 92% yield with excellent purity (99.2%) as determined by HPLC-MS.

Example 2. OLED fabrication and characterization

Green phosphorescence-based OLEDs with an active area of 9 mm² were fabricated on glass substrates coated with 100 nm indium tin oxide (ITO).

The device fabrication described below is intended as an example and does not in any way imply the limitation of the invention to the said fabrication process, device architecture (sequence, number of layers, etc.) or materials other than the materials claimed.

The OLED devices of the present examples consist of the layer sequence shown in FIG. 1 .

The devices were fabricated by vacuum thermal evaporation, except for the hole injecting layer, which was deposited by spin-coating an HIL ink composition having the components indicated in Table 1 for HIL1 on the ITO surface. Before depositing the ink to form an HIL on the substrates, pre-conditioning of the substrates was performed. The device substrates were first cleaned by ultrasonication in various solutions or solvents. The device substrates were ultrasonicated in a dilute soap solution, followed by distilled water, then acetone, and then isopropanol, each for about 20 minutes. The substrates were dried under nitrogen flow. Subsequently, the device substrates were then transferred to a vacuum oven set at 120 °C and kept under partial vacuum (with nitrogen purging) until ready for use. The device substrates were treated in a UV- Ozone chamber operating at 300 W for 20 minutes immediately prior to use.

The HIL was formed on the device substrate by spin coating the ink in air. The substrates comprising the HIL layers were stored in the dark under partial vacuum before subsequent steps. The remaining layers of the device stack were deposited by means of vacuum thermal evaporation (VTE). VTE was performed under vacuum at a base pressure of 10-7 mbar in a Super-SPECTROS 200 Organic Thin Film Deposition and Metallization System (available from Kurt J. Lesker Company).

Subsequently, the hole transport layer and the emissive layer were deposited.

The hole transport layer comprised HT1 or HT2. The emissive layer (EML) comprised H1 or GH1 combined with various emitter compounds, such as lr(ppy)₃, lr(mppy)₃, or another Ir-based emitter E1.

Ir(ppy)₃ is tris(2-phenylpyridine)iridium(lll) and has a LUMO energy of 3 eV. Ir(mppy)₃ is iridium (III) tris(2-(4-tolyl)pyridinato-N,C2') and has a LUMO energy of 2.2 eV, according to "Highly Efficient OLEDs with Phosphoresent Materials" Hartmut Yersin, ed. (2008, Wiley-VCH, Weinheim). The host (H1 or GH1 ) and emitter (lr(ppy)₃, lr(mppy)₃, or E1 ) were each evaporated simultaneously and independently to form the emissive layer by co-deposition. The electron transport layer (ETL) was deposited on the EML, followed by the electron injection layer (EIL). The ETL comprised either Alq₃ or H1 .

Aluminium was deposited as the cathode.

All layers were deposited sequentially without vacuum break.

After fabrication, the devices were immediately encapsulated using a UV-curable epoxy glue in an N₂-filled glovebox (O2 < 6 ppm, H₂0 < 0.1 ppm). A commercial desiccant (Dynic Co, Japan) was attached to the capglass prior to encapsulation.

The OLED device comprises pixels on a glass substrate whose electrodes extended outside the encapsulated area of the device which contain the light emitting portion of the pixels. The electrodes were contacted with a current source meter such as a Keithley 2400 source meter with a bias applied to the aluminum electrode while the ITO electrode was earthed. This results in positively charged carriers (holes) and negatively charged carriers being injected into the device which form excitons and generate light.

Simultaneously, another Keithley 2400 source meter is used to address a large area silicon photodiode. This photodiode is maintained at zero volts bias by the 2400 source meter. It is placed in direct contact with area of the glass substrate directly below the lighted area of the OLED pixel. The photodiode collects the light generated by the OLED converting them into photocurrent which is in turn read by the source meter. The photodiode current generated is quantified into optical units (candelas/sq. meter) by calibrating it with the help of a Minolta CS-200 Chromameter.

During the testing of the device, the Keithley 2400 addressing the OLED pixel applies a voltage sweep to it. The resultant current passing through the pixel is measured. At the same time the current passing through the OLED pixel results in light being generated which then results in a photocurrent reading by the other Keithley 2400 connected to the photodiode. Thus the current-voltage-luminance or IVL data for the pixel is generated.

From the IVL data, the external quantum efficiency (EQE, reported as a percentage) can be determined. The CIE (Commission Internationale de I'Eclairage) x and y coordinates of the color of the organic light emitting devices were measured.

Example 3. Properties of inventive OLEDs OLEDs were fabricated and their performance evaluated. As described herein, the components used in the HTL, EML, EIL, and ETL were varied. Table 2 summarizes the devices made in accordance with the present disclosure. The HIL in the devices was maintained as HIL1 . Table 2. Devices made in accordance with the present disclosure

The performance of devices 3A-3I was evaluated and their properties are summarized in Table 3 below. Table 3. Performance of devices 3A-3I

Claims

WHAT IS CLAIMED IS:

1 . An organic light-emitting device comprising:

a substrate,

an anode,

a hole injection layer,

a hole transporting layer,

an emissive layer,

an electron transport layer,

an electron injection layer, and

a cathode layer;

wherein the emissive layer and the electron transport layer each comprise a substituted or unsubstituted spirobifluorene compound, with the proviso that the spirobifluorene compound of the electron transport layer is a compound represented by general formula 1

(1 ) or general formula 2

(2) wherein

Ar is a substituted or unsubstituted nitrogen-containing heteroaryl ring comprising at least two nitrogen atoms in the ring,

An is a substituted or unsubstituted aryl or heteroaryl ring,

m is 0 or 1 ,

n is 0 or 1 ,

Xi to X₈ are each, independently, other than Ar or Αη and is a Ci-C₃₀ hydrocarbyl or C1-C30 heterohydrocarbyl, and

o, p, q, r, s, u, v and w, are each, independently, an integer from 0 to 3.

2. The organic light-emitting device according to claim 1 , wherein, in the

spirobifluorene compound of the electron transport layer, Ar is a heteroaryl ring selected from the group consisting of pyrazolyl, imidazolyl, triazolyl, pyrimidinyl, pyridazinyl, triazinyl and tetrazinyl.

3. The organic light-emitting device according to claim 1 or 2, wherein, in the spirobifluorene compound of the electron transport layer, Ar is a heteroaryl ring selected from the group consisting of pyrimidinyl, pyridazinyl, triazinyl and tetrazinyl.

4. The organic light-emitting device according to any one of claims 1 to 3, wherein, in the spirobifluorene compound of the electron transport layer, An is a 5- or 6- membered aryl or heteroaryl ring.

5. The organic light-emitting device according to claim 4, wherein, in the

spirobifluorene compound of the electron transport layer, An is identical to Ar.

6. The organic light-emitting device according to any one of claims 1 to 5, wherein, in the spirobifluorene compound of the electron transport layer, m or n are 1.

7. The organic light-emitting device according to any one of claims 1 to 6, wherein, in the spirobifluorene compound of the electron transport layer, Ar is substituted with at least one aryl group.

8. The organic light-emitting device according to any one of claims 1 to 7, wherein, in the spirobifluorene compound of the electron transport layer, Ar has the structure

wherein A represents C, N, 0 or S, provided that at least two atoms A are nitrogen and wherein the carbon atoms of Ar are substituted or unsubstituted.

9. The organic light-emitting device according to any one of claims 1 to 8, wherein the spirobifluorene compound of the electron transport layer is a compound of general formula 1 represented by any one of the following structures:

wherein

R-i , which may be the same or different at each occurrence, is Ci -C₃₀ hydrocarbyl or C1-C30 heterohydrocarbyl;

A is C, N, 0, or S, with the proviso that at least two A atoms in the same ring are nitrogen.

10. The organic light-emitting device according to claim 9, wherein the compound of general formula 1 is a compound represented by any one of the following structures:

54

55

wherein Ri represents a phenyl group.

1 1 . The organic light-emitting device according to any one of claims 1 -10, wherein the substituted or unsubstituted spirobifluorene compound of the emissive layer and the electron transport layer are the same or different.

12. The organic light-emitting device according to claim 1 1 , wherein the substituted or unsubstituted spirobifluorene compound of the emissive layer and of the electron transport layer are the same.

13. The organic light-emitting device according to any one of claims 1 -12, wherein the hole injection layer comprises a polythiophene comprising a repeating unit complying with formula (I)

wherein R-n and R₁₂ are each, independently, H, alkyl, fluoroalkyi, alkoxy, aryloxy, or -0-[Z-0]_a-R_e;

wherein

Z is an optionally halogenated hydrocarbylene group,

a is equal to or greater than 1 , and

R_e is H, alkyl, fluoroalkyi, or aryl.

14. The organic light-emitting device according to claim 13, wherein R-n and Ri₂ are each, independently, H, fluoroalkyi, -0[C(R_aRb)-C(R_cRd)-0]a-Re, -ORf; wherein each occurrence of R_a, R_b, R_c, and R_d, are each, independently, H, halogen, alkyl, fluoroalkyi, or aryl; R_e is H, alkyl, fluoroalkyi, or aryl; a is 1 , 2, or 3; and R_f is alkyl, fluoroalkyi, or aryl.

15. The organic light-emitting device according to claim 13 or 14, wherein R-n is H and R-I 2 is other than H.

The organic light-emitting device according to claim 15, wherein Ri₂ -0[C(R

17. The organic light-emitting device according to claim 16, wherein Ri₂ is - O[C(R_aRb)-C(R_cRd)-O]a-Re.

18. The organic light-emitting device according to claim 17, wherein each occurrence of R_a, R_b, Rc, and R_d, are each, independently, H, (Ci -C8)alkyl, (Ci-C8)fluoroalkyl, or phenyl; and R_e is (CrC₈)alkyl, (CrC₈)fluoroalkyl, or phenyl.

19. The organic light-emitting device according to claim 18, wherein the

polythiophene comprises a repeating unit represented by the structure

20. The organic light-emitting device according to any one of claims 13-19, wherein the polythiophene is sulfonated.

21 . The organic light-emitting device according to any one of claims 13-20, wherein the polythiophene is sulfonated poly(3-MEET).

22. The organic light-emitting device according to any one of claims 1 -21 , wherein the hole injection layer comprises a poly(styrene) or poly(styrene) derivative.

23. The organic light-emitting device according to claim 22, wherein the poly(styrene) or poly(styrene) derivative is poly(4-hydroxystyrene).

24. The organic light-emitting device according to any one of claims 1 -23, wherein the hole injection layer comprises a polymeric acid comprising a repeating unit complying with formula (II) and a repeating unit complying with formula (III)

wherein

each occurrence of R ₃, R ₄, R ₅, R ₆, R17, R18, and R ₉ is, independently, H, halogen, fluoroalkyl, or perfluoroalkyl; and

X10 is -[OC(R_hRi)-C(RjR_k)]_b-0-[CR|R_m]c-S0₃H,

wherein each occurrence of R_h, Rj, Rj, Rk, Ri and R_m is, independently, H, halogen, fluoroalkyl, or perfluoroalkyl;

b is 0 to 10; and

c is 1 -5.

25. The organic light-emitting device according to claim 24, wherein each occurrence of Ri3, Ri₄, Ri5, and Ri₆ is F.

26. The organic light-emitting device according to claim 24 or 25, wherein each occurrence of R ₇, R ₈, and R ₉ is F.

27. The organic light-emitting device according to any one of claims 24-26, wherein each occurrence of R_h and Rj is F; R_j is (Ci-C8)perfluoroalkyl; R_k, Ri and R_m are each F.

28. The organic light-emitting device according to any one of claims 1 -27, wherein the hole transport layer comprises a compound selected from the group consisting of

mixture thereof.