WO2017116625A1

WO2017116625A1 - Spirobifluorene derivatives having nitrogen-containing heteroaryl rings and their use in organic electronics

Info

Publication number: WO2017116625A1
Application number: PCT/US2016/065102
Authority: WO
Inventors: Marc Sims; Enrico Orselli; Jonathan Maunoury; Dominique Bascour; Morgane Virboul
Original assignee: Solvay Usa Inc.
Priority date: 2015-12-30
Filing date: 2016-12-06
Publication date: 2017-07-06

Abstract

The present disclosure relates to emissive films comprising at least one emitter compound having a LUMO energy of at least 1.8 eV and spirobifluorene derivatives having nitrogen-containing heteroaryl rings. The present disclosure also relates to their use in the emissive layer of organic electronic devices, such as, for example, organic light-emitting devices.

Description

SPIROBIFLUORENE DERIVATIVES HAVING NITROGEN-CONTAINING HETEROARYL RINGS AND THEIR USE IN ORGANIC ELECTRONICS

Cross Reference to Related Applications

This application claims the priority of U.S. Provisional Application No. 62/272,836 filed December 30, 2015, which is hereby incorporated by reference in its entirety.

Field of the Invention

The present invention relates to spirobifluorene derivatives having nitrogen- containing heteroaryl rings and their use in the emissive layer 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 emissive materials, particularly matrix materials used in the emissive layers, of organic electronic devices, such as OLEDs, to result in high efficiency, long lifetime and low operating voltages.

Accordingly, an object of the present invention is to provide emissive films having high efficiency, long lifetime and/or low operating voltages that are useful in organic electronics applications.

Summary of the Invention In a first aspect, the present disclosure relates to an emissive film comprising: a) at least one emitter compound having a LUMO energy of at least 1 .8 eV, and b) a compound of general formula 1 or a compound of general formula 2,

wherein

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

Ar₁ 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 Ar₁ 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.

In a second aspect, the present disclosure relates to an organic electronic device comprising an emissive layer, wherein the emissive layer comprises the emissive film described herein.

Brief Description of the Figures

FIG. 1 shows the device structure of inventive green OLEDs described herein. FIG. 2 shows the current density as a function of voltage for an example green OLED. FIG. 3 shows the %EQE as a function of luminance for an example green OLED, wherein NPB is present.

FIG. 4 shows the %EQE as a function of luminance for example green OLEDs wherein the NPB layer is either present or absent.

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 (C₁-C₄₀) 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 ( C₁ -C₄₀) 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 ( C₁ -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 (C₁-C₄₀) 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.

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 (N0₂), cyano (CN), and hydroxy (OH).

The present disclosure relates to an emissive film comprising:

a) at least one emitter compound having a LUMO energy of at least 1 .8 eV, and b) a compound of general formula 1 or a compound of general formula 2,

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

Ar₁ 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 Ar₁ 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. 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, Ar₁ is a 5- or 6-membered aryl or heteroaryl ring. In another embodiment, Ar₁ is identical to Ar. In an embodiment, m or 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 are substituted or unsubstituted.

In an embodiment, compound b) is a compound of formula 1 .

In an embodiment, compound b) is a compound represented by any one of the following structures:

wherein R₁, which may be the same or different at each occurrence, is C₁ -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, compound b) is a compound represented by any one of the following structures:

wherein R₁ represents a phenyl group.

The spirobifluorene 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.

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.

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. The emitter of the emissive film according to the present disclosure is 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 at least one 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, R₈, 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, L1 is picolinate.

In another embodiment, L2 is a ligand represented by the structure

In an embodiment, L2 is the ligand represented by the structure

In an embodiment, x is 0 or 1 .

Examples of suitable emitter compounds include, but are not limited to, tris(2- phenylpyridine)iridium(lll); 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 FIrPic), 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(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 film 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 film 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); and (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 compound of formula 1 or formula 2 to the at least one emitter compound may be measured and controlled. The weight ratio of the compound of formula 1 or formula 2 to the at least one emitter compound is 50:50, typically 80:20, more typically 90: 10, even more typically 92:8, in the emissive film of the present disclosure.

The present disclosure further relates to an organic electronic device, typically an organic light-emitting device, comprising an emissive layer, wherein the emissive layer comprises the emissive film described herein.

The organic light-emitting device according to the present disclosure comprises: a substrate,

an anode,

a hole transporting layer (HTL),

an emissive layer (EML),

an electron transporting layer (ETL), and

a cathode layer, wherein the emissive layer comprises the emissive film described herein.

The substrate 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 layer 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 emissive layer comprises the emissive film described herein. In an

embodiment, the emissive layer consists essentially of the emissive film described herein. In another embodiment, the emissive layer consists of the emissive film described herein. The hole transport layer may comprise one or more hole carrier molecules and/or polymers. As used herein, the term "hole carrier compound (or molecule)" refers to any compound or molecule that is capable of facilitating the movement of holes, i.e., positive charge carriers, and/or blocking the movement of electrons. 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, N,N'-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, .alpha-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, N,N'-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) 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.

The organic light-emitting device of the present disclosure may comprise a hole injection layer, typically disposed between the hole transport layer and the anode. The hole injection layer may include, for example, low molecular weight compounds or high molecular weight compounds. The hole carrier compounds of the hole injection layer 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-carbazol-9-ylphenyl)amine; and tris[4-( diethylamino )phenyl]amine. 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 suitable 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. Hole carrier compounds described herein are known in the art and are commercially available.

The electron transport layer typically promotes electron mobility and reduces the likelihood of a quenching reaction while electrons are directed towards the emissive layer. Examples of materials suitable for the elctron transport layer include, for example, metal chelated oxinoid compounds, such as bis(2-methyl-8- quinolinolato)(para-phenyl-phenolato)aluminum(lll) and tris(8- hydroxyquinolato)aluminum, (8-hydroxyquinolato)lithium, tetrakis(8- hydroxyquinolinato)zirconium, azole compounds such as 2-(4-biphenylyl)-5-(4-t- butylphenyl)-1 ,3,4-oxadiazole, 3-(4-biphenylyl)-4-phenyl-5-(4-t-butylphenyl)-1 ,2,4- triazole, and 1 ,3,5-tri(phenyl-2-benzimidazole)benzene, quinoxaline derivatives such as 2,3-bis(4-fluorophenyl)quinoxaline, phenanthroline derivatives such as 9, 10- diphenylphenanthroline and 2,9-dimethyl-4,7-diphenyl-1 , 10-phenanthroline, and as well as mixtures thereof. Alternatively, the electron transport layer may comprise an inorganic material, such as, for example, BaO, LiF, and Li₂0.

The organic light-emitting device of the present disclosure may comprise an electron injection layer, typically disposed between the electron transport layer and the cathode. Suitable materials for such an electron injection layer are, for example, LiF, (8-hydroxyquinolato)lithium (LiQ), CsF, Cs₂C0₃, Li₂0, LiB0₂, K₂Si0₃, Cs₂0 or AI₂0₃.

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 films, methods and processes, and devices according to the present disclosure are further illustrated by the following non-limiting examples.

Examples

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 4 mm² were fabricated on 150nm-thick indium tin oxide (ITO)-coated glass substrates.

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 aqueous ink composition designated "AQ1 100", which comprises a conductive polymer in a mixture of water and butyl cellusolve, 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 AQ1 100 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).

In some examples, N,N'-bis(1 -naphtalenyl)-N,N'-bis(phenyl)benzidine (NPB) was deposited on top of the HIL. In other examples, no NPB was used.

2,7-di-9H-carbazol-9-yl-9, 10-dihydro-9,9-dimethyl-10-phenyl-acridine, herein designated ΉΤ1 ", was deposited on top of NPB (when present) or directly on the HIL when NPB was not used. Subsequently, an inventive emissive layer was deposited. The emissive layer comprises 1 -(9,9'-spirobi[9H-fluoren]-3-yl)-3,5-diphenyl-1 ,3,5-triazine (H1 ) and lr(mppy)₃. 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). Each of H1 and lr(mppy)₃ were evaporated simultaneously and independently to form the emissive layer by co-deposition. This layer was followed by a layer of H1 .

LiQ (8-hydroxyquinolinolato)lithium and then aluminium were 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 (0₂ < 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.

The external quantum efficiency (EQE, measured in percent) as a function of the luminance, calculated from current-voltage-luminance data, was also investigated.

Example 3. Green OLED properties The current density vs. voltage characteristics of the green OLED having the device structure shown in FIG. 1 , wherein NPB is present, were determined. FIG. 2 shows the current density as a function of voltage for the green OLED.

FIG. 3 shows the %EQE as a function of luminance for the green OLED having the device structure shown in FIG. 1 , wherein NPB is present.

FIG. 4 shows the %EQE as a function of luminance for green OLEDs wherein the NPB layer is either present or absent.

Claims

WHAT IS CLAIMED IS:

1 . An emissive film comprising:

a) at least one emitter compound having a LUMO energy of at least 1 .8 eV, and

b) a compound of general formula 1 or a compound of general formula 2,

wherein

Ar-ι is a substituted or unsubstituted aryl or heteroaryl ring,

m is 0 or 1 ,

n is 0 or 1 ,

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

2. The emissive film according to claim 1 , wherein Ar is a heteroaryl ring selected from the group consisting of pyrazolyl, imidazolyl, triazolyl, pyrimidinyl, pyridazinyl, triazinyl and tetrazinyl.

3. The emissive film according to claim 1 , wherein Ar is a heteroaryl ring selected from the group consisting of pyrimidinyl, pyridazinyl, triazinyl and tetrazinyl.

4. The emissive film according to any one of claims 1 to 3, wherein Ar₁ is a 5- or 6-membered aryl or heteroaryl ring.

5. The emissive film according to claim 4, wherein Ar₁ is identical to Ar.

6. The emissive film according to any one of claims 1 to 5, wherein m or n are 1 .

7. The emissive film according to any one of claims 1 to 6, wherein Ar is substituted with at least one aryl group.

8. The emissive film according to any one of claims 1 to 7, wherein Ar has the structure

9. The emissive film according to any one of claims 1 to 8, wherein compound b) is a compound represented by any one of the following structures:

wherein

R₁, which may be the same or different at each occurrence, is C₁ -C₃₀ hydrocarbyl or C₁ -C₃₀ heterohydrocarbyl;

10. The emissive film according to claim 9, wherein compound b) is a compound represented by any one of the following structures:

33

wherein R₁ represents a phenyl group.

1 1 . The emissive film according to any one of claims 1 -10, wherein the at least one emitter compound is a compound represented by the formula

wherein L1 is an ancillary ligand 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, benzot

thienylpyridine, tolylpyridine, phenylimines, vinylpyridines, arylquinolines, pyndylnaphthalenes, pyndylpyrroles, pyridylimidazoles, phenylindoles, and derivatives thereof;

L2 is a ligand represented by the structure

wherein R₂, R₃, R₄, R₅, R₆, R₇, R₈, and R₉ are each, independently, H, halogen, cyano, or alkyl; and

x is an integer from 0 to 3.

12. The emissive film according to claim 1 1 , wherein each occurrence of L1 is picolinate.

13. The emissive film according to claim 1 1 or 12, wherein each occurrence of L2 is represented by the structure

14. The emissive film according to any one of claims 1 1

occurrence of L2 is represented by the structure

15. The emissive film according to any one of claims 1 1 -13, wherein x is 0 or 1.

16. An organic light-emitting device comprising an emissive layer, wherein the emissive layer comprises the emissive film according to any one of claims 1 -14.

17. The organic light-emitting device according to claim 16, wherein said organic light-emitting device comprises:

a substrate,

an anode,

a hole transporting layer,

an emissive layer,

an electron transporting layer, and

a cathode layer.