OLED DEVICES WITH IMPROVED LIFETIME USING NON-CRYSTALLIZABLE MOLECULAR GLASS MIXTURE HOSTS
20170237004 · 2017-08-17
Assignee
Inventors
Cpc classification
H10K85/626
ELECTRICITY
H10K85/6572
ELECTRICITY
H10K85/633
ELECTRICITY
H10K85/636
ELECTRICITY
H10K85/615
ELECTRICITY
C09K11/025
CHEMISTRY; METALLURGY
H10K85/621
ELECTRICITY
International classification
Abstract
An OLED multilayer electroluminescent device includes a cathode, an anode, a light-emitting layer (LEL) disposed therebetween, and charge-transporting layers disposed between (A) the cathode and the light-emitting layer, (B) the anode and the light-emitting layer, or (C) both (A) and (B). The light-emitting layer (LEL) includes a host material and an emitter. The host material includes a high-entropy non-crystallizable molecular glass mixture, which includes hole-transporting capabilities, electron-transporting capabilities, or ambipolar capabilities. The ambipolar capabilities include hole-transporting capabilities and electron-transporting capabilities.
Claims
1. An OLED multilayer electroluminescent device comprising: a cathode, an anode, a light-emitting layer (LEL) disposed there between, and charge-transporting layers disposed between (A) the cathode and the light-emitting layer, (B) the anode and the light-emitting layer, or (C) both (A) and (B); wherein: the light-emitting layer (LEL) comprises a host material and an emitter-dopant; the host material comprises a high-entropy non-crystallizable molecular glass mixture, the high-entropy non-crystallizable molecular glass mixture having hole-transporting capabilities, electron-transporting capabilities, or ambipolar capabilities, wherein the ambipolar capabilities comprises hole-transporting capabilities and electron-transporting capabilities.
2. The OLED multilayer electroluminescent device according to claim 1, wherein the host material is chosen from a neat host or a mixed-host having more than one host-type, wherein the neat host or at least one host-type of the mixed host.
3. The OLED multilayer electroluminescent device according to claim 1, wherein high-entropy non-crystallizable molecular glass mixture comprising three or more than three components.
4. The OLED multilayer electroluminescent device according to claim 3, wherein components are structural isomers.
5. The OLED multilayer electroluminescent device according to claim 1, wherein the host material is chosen from glass mixtures 4, 6, 7, 8, 9, 22, 32, 50, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, or 135.
6. The OLED multilayer electroluminescent device according to claim 1, wherein the host material is selected from the group consisting of glass mixtures 4 and 22.
7. The OLED multilayer electroluminescent device according to claim 1, wherein the host material is of from 4 to 75 wt. % of the total weight of the light emitting layer.
8. The OLED multilayer electroluminescent device according to claim 1, wherein the host material is of from 4 to 32 wt. % of the total weight of the light emitting layer.
9. The OLED multilayer electroluminescent device according to claim 1, wherein the emitter dopant is of from 2 to 32 wt. % of the total weight of the light emitting layer.
10. The OLED multilayer electroluminescent device according to claim 3, wherein at least two of the three or more than three components comprising a structure according to formula (1):
(R.sup.1Y.sup.1).sub.p[(R.sup.2Y.sup.2).sub.mR.sup.2Y.sup.3].sub.nZ.sup.2Y.sup.4R.sup.3 where: m is zero or one; n is zero eight; and p is one to eight; R.sup.3 and each R.sup.1 independently represents a monovalent aliphatic or cycloaliphatic hydrocarbon group having 1 to 20 carbon atoms or an aromatic group or a multicyclic aromatic nucleus; each R.sup.2, Z.sup.1, and Z.sup.2 independently represent multivalent aliphatic or cycloaliphatic hydrocarbon groups having 1 to 20 carbon atoms or an aromatic group; and each Y.sup.1, Y.sup.2, Y.sup.3, and Y.sup.4 independently represents a triple bond, a double bond, or a single bond link; provided that at least one of R.sup.1, Z.sup.1, R.sup.2, Z.sup.2 and R.sup.3 is a multicyclic aromatic nucleus.
11. The OLED multilayer electroluminescent device according to claim 10, wherein the monovalent charge transport moiety is an electron-transport moiety and the multivalent transport moiety is a hole-transport moiety.
12. The OLED multilayer electroluminescent device according to claim 10, wherein the monovalent charge transport moiety is a mixture of electron-transport and hole-transport moiety and the multivalent transport moiety is a hole-transport moiety.
13. The OLED multilayer electroluminescent device according to claim 1 further comprising charge-injecting layers disposed between (A) the cathode and the light emitting layer, (B) the anode and the light emitting layer, or (C) both (A) and (B).
Description
BRIEF DESCRIPTION OF FIGURES
[0016]
[0017]
[0018]
[0019]
[0020]
[0021]
DETAILED DESCRIPTION
[0022] Throughout this document, the following terms will have the following meanings.
[0023] The term “amorphous” means that the mixture is noncrystalline. That is, the mixture has no molecular lattice structure.
[0024] The term “non-equilibrium molecular glass” means a glass forming material that is crystallizable under certain conditions, for example above their glass transition temperature, or in contact with certain solvents.
[0025] The term ‘“non-crystallizable molecular glass” means a glass composition that will never crystallize under any circumstances and is amorphous.
[0026] The term “asymmetric glass mixture” means a glass mixture where all the components are asymmetric, i.e. have all distinct substituents.
[0027] The term “isomeric glass mixture” means a glass mixture where all the components have the same molecular weight.’
[0028] The term “high-entropy” when referring to a glass mixture means that the glass mixture has high level of disorganization. The higher the number of components, the higher the entropy.
[0029] A hole transporting material may conduct positive charge.
[0030] An electron-transporting material may conduct negative charge (electrons).
[0031] An ambipolar material may conduct both positive and negative charges (electrons).
[0032] The term “hole-trapping emitter” refers to an emitter that can transport positive charges.
[0033] The term “electron-trapping emitter” refers to an emitter that can transport negative charges (electrons).
[0034] The term “isomeric glass mixture” refers to a glass mixture where all the components have the same molecular weight.
[0035] The term “multicyclic aromatic nucleus” refers to a nucleus comprising at least two cyclic groups one of which is aromatic, including aromatic heterocyclic ring groups. The cyclic group may be substituted with substituents such as aliphatic hydrocarbons, including cycloaliphatic hydrocarbons, other aromatic ring groups such as aryl, and heterocyclic ring groups such as substituted or fused thiazole, oxazole, imide, pyrazole, triazole, oxadiazole, pyridine, pyrimidine, pyrazine, triazine, tetrazine and quinoline groups. The substituents are fused or non-fused and mono or polycyclic. Examples of multicyclic aromatic nuclei include 9,9-bis(4-hydroxy-3,5-dichlorophenyl)fluorene, 4,4′-hexahydro-4,7-methanoindan-5-ylidenebis(2,6-dichlorophenol); 9,9-bis(4-hydroxy-3,5-dibromophenyl(fluorene, 4,4′-hexahydro-4,7-methanoindan-5-ylidenebis(2,6-dibromophenol); 3′,3″,5′,5″-tetrabromophenolphthalein, 9,9-bis(4-aminophenyl)fluorene, phenylindandiols; 1,1′-spirobiindandiols, 1,1′-spirobiindandiamines, 2,2′-spirobichromans; 7,7-dimethyl-7H-dibenzo [c,h]xanthenediol; xanthylium salt diols; 9,9-dimethylxanthene-3,6-bis(oxyacetic acids); 4,4′(3-phenyl-1-indanylidene)diphenol and other bisphenols; 3′,3″-dibromo-5′,5″-dinitro-2′,2″-oxaphenolphthalein; 9-phenyl-3-oxo-2,6,7-trihydroxyxanthene; and the like.
[0036] “Aliphatic hydrocarbon group” refers to monovalent or divalent, alkanes, alkenes, alkadienes and alkynes having from 1 to 20 carbon atoms. The groups are straight or branched chain and include carbohydrate, carboxylic acid, alcohol, ether aldehyde and ketone functions.
[0037] “Cycloaliphatic” refers to cyclic aliphatic hydrocarbon groups. The groups may be substituted with halogen, alkoxy, amide, nitro, esters and aromatic groups.
[0038] Exemplary aliphatic groups include methyl, ethyl, propyl, isopropyl, butyl, hexyl, 2-ethylhexyl, methoxyethyl, ethoxycarbonylpropyl, 3-oxobutyl, 3-thiapentyl, furfuryl, 2-thiazolylmethyl, cyclohexylmethyl, benzyl, phenethyl, phenoxyethyl, vinyl (—CH═CH—), 2-methylvinyl, allyl, allylidene, butadienyl, butenylidene, propargyl, and the like.
[0039] “Aromatic” and “aromatic heterocyclic” group refers to organic groups which undergo the same type of substitution reaction as benzene. In benzene, substitution reactions are preferred over addition reactions. Such groups preferably have from 6 to about 40 nuclear atoms and are mono- and polycyclic.
[0040] Exemplary aromatic groups include quinolinyl, pyrimidinyl, pyridyl, phenyl, tolyl, xylyl, naphthyl, anthryl, triptycenyl, p-chlorophenyl, p-nitrophenyl, p-bromophenyl, 2,4-dichlorophenyl, 2-chlorophenyl, 3,5-dinitrophenyl, p-(tetrabromophthalimido)phenyl, p-(tetrachlorophthalimido)phenyl, p-tetraphenylphthalimido)phenyl, p-naphthalimidophenyl, p-(4-nitrophthalimido)phenyl, p-phthalimidophenyl, 1-hydroxy-2-naphthyl, 3,5-dibromo-4-(4-bromobenzoyloxyl)phenyl, 3,5-dibromo-4-(3,5-dinitrobenzoyloxyl)phenyl, 3,5-dibromo-4-(1-naphthoyloxyl)phenyl, thiazolyl, oxazolyl, imidazolyl, pyrazolyl, triazolyl, oxadiazolyl, pyrazinyl, etc and their corresponding multivalent and fused ring configurations.
[0041] In some embodiments, the high-entropy non-crystallizable material includes three or more components, and at least two of the three or more components are structures according to formula (1):
(R.sup.1Y.sup.1).sub.p[(R.sup.2Y.sup.2).sub.mR.sup.2Y.sup.3].sub.nZ.sup.2Y.sup.4R.sup.3 (I)
[0042] In formula (I), subscript m is zero or one; subscript n is zero to eight; and subscript p is one to eight. R.sup.3 and each R.sup.1 independently represents a monovalent aliphatic or cycloaliphatic hydrocarbon group having 1 to 20 carbon atoms or an aromatic group or a multicyclic aromatic nucleus. Each R.sup.2, Z.sup.1, and Z.sup.2 independently represents multivalent aliphatic or cycloaliphatic hydrocarbon groups having 1 to 20 carbon atoms or an aromatic group. Each Y.sup.1, Y.sup.2, Y.sup.3, and Y.sup.4 independently represents a triple bond, a double bond, or a single bond link, provided that at least one of R.sup.1, Z.sup.1, R.sup.2, Z.sup.2 and R.sup.3 is a multicyclic aromatic nucleus.
[0043] An OLED device of this disclosure includes a multilayer electroluminescent device comprising a cathode, an anode, an optional charge-injecting layers, charge-transporting layers, and a light-emitting layer (LEL) comprising a neat host or a mixed-host, wherein the neat host or at least one member of the mixed host is a high-entropy non-crystallizable molecular glass mixture comprising three or more than three components. The host material can be hole-transporting, electron-transporting, or ambipolar, that is capable on transporting both positive and negative charges (electrons). In some embodiments, the host material includes a mixed-host, which is a mixture of a hole-transporting high-entropy non-crystallizable material and an electron-transporting high-entropy non-crystallizable material. However, in some embodiments of the OLED, as demonstrated in U.S. Patent Publication No. 2015/0053894, the high-entropy non-crystallizable materials can be mixed with highly crystalline materials at high concentration to yield a new mixture that is non-crystallizable. Thus, the mixed-host may be either a mixture a high-entropy hole-transporting material, as described herein, and an electron-transporting crystallizable material, or a high-entropy electron-transporting material and a hole-transporting crystallizable material.
[0044] To achieve a highly efficient phosphorescent OLED, triplet emitter-dopants are usually embedded in a suitable host to reduce concentration quenching. A good host material should fulfill the following requirements: (1) the triplet energy must be higher compared to the emitter, which prevents energy back transfer to the host material, (2) suitable energy levels aligned with the neighboring layers for efficient charge carrier injection to obtain a low driving voltage; (3) decent charge carrier transporting abilities to increase the chance for hole and electron recombination within the emitting layer; and (4) the HOMO (highest occupied molecular orbital) of the host materials should be deeper than that of the emitters, while the LUMO (lowest unoccupied molecular orbital) of the host materials should be shallower than that of the emitters.
[0045] Blue phosphorescent and thermally assisting delayed fluorescent emitters have higher triplet energy than green, yellow and red emitters, in that order. Thus blue emitters require higher triplet host (2.8 eV to 3.0 eV) than green, yellow and red emitters.
[0046] In mixed-host systems, the triplet energy of the individual host should meet the requirements described above such that the triplet energy of the mixed host is greater than the emitter. The triplet energy of the host materials is estimated from the phosphorescence emission of the host at or below 77 K.
[0047] In some embodiments, the light-emitting layer of the device includes host material and an emitter-dopant. The emitter-dopant may be present in an amount of up to 20 wt. % of the host, from 0.1 to 18.0 wt. % of the host, from 0.5 to 10 wt. % of the host, or from 0.1 to 5 wt. %. The emitter-dopant may include a fluorescent emitter, a phosphorescent emitter, a thermally delayed fluorescent emitter, or a combination thereof.
[0048] The emitter dopant can be a fluorescent emitter, a phosphorescent emitter, or a thermally delayed fluorescent emitter. The composition of the host is adjusted for the type of emitter. For example, high-triplet energy host is required for phosphorescent and thermally activated delayed fluorescence (TADF) emitters.
[0049] Examples of fluorescent emitters include coumarin dyes such as 2,3,5,6-1H,4H-tetrahydro-8-trichioromethylquinolizino(9,9a,1gh) coumarin, cyanine-based dyes such as 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyrylene)-4H-pyran, pyridine-based dyes such as 1-ethyl-2-(4-(p-dimethylaminophenyl)-1,3-butadienyl)-pyridium perchlorate, xanthene-based dyes such as rhodamine B, and oxazine-based dyes. The fluorescent material can also include inorganic phosphors.
[0050] Examples of phosphorescent emitters include Ir(ppy).sub.3 (fac tris(2 phenylpyridine) iridium) (green) or FIrpic (iiidium(III)bis[4,6-di-(fluorophenyl)-pyridinato-N, C2′]picolinate) (blue), a red phosphorescent dopant RD61 available from UDC. Other blue phosphorescence emitter include iridium (III) bis(4′,6′-difluorophenylpyridanato) tetrakis(1-pyrazolyl)borate (FIr6) (HOMO level=6.1 eV, LUMO level=3.1 eV, T.sub.1=2.71 eV), iridium (III) bis[4,6-(di-fluorophenyl)-pyridinato-N, C2′]picolinate (FIrpic), iridium (III) tris[N-(4′-cyanophenyl)-N′-methylimidazole-2-ylidene-C2, C2′] (Ir(cn-pmic).sub.3), tris((3,5-difluoro-4-cyanophenyl)pyridine)iridium (FCNIr), and Ir(cnbic).sub.3, and complexes of heavy atom metals such as platinum (Pt), rhenium (Re), ruthenium (Ru), copper (Cu), and osmium (Os). (2,4-Pentanedionato)bis[2-(2-quinolinyl)phenyl]iridium(III), Bis[5-methyl-2-(2-pyridinyl-N)phenyl-C](2,4-pentanedionato-O.sup.2,O.sup.4)iridium(III), Bis[2-(2-benzothiazolyl-N3)phenolato-O]zinc, Bis [2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridiumn(III), Bis[2-(1-isoquinolin-N)phenyl-C](2,4-pentanedionato-O.sup.2O.sup.4)iridium(III), Tris[2-(benzo[b]thiophen-2-yl)pyridinato-C.sup.3,N]iridium(III), Bis[2-(1-isoquinoinyl-N)phenyl-C](2,4-pentanedionato-O.sup.2,O.sup.4)iridium(III), Bis[2-(2-pyridinyl-N)phenyl-C](2,4-pentanedionato-O.sup.2, O.sup.4)iridium(III, Dichlorotris(1,10-phenanthroline)ruthenium(II) hydrate, Bis(2-benzo[b]thiophen-2-ylpyridine)(acetyacetonate)iridium(III), Lithium tetra(2-methyl-8-hydroxyquinolinato)boron, bis(2,2′-bipyridyl)dichlororuthenium(II) hexahydrate, and other emitting materials capable of phosphorescence.
[0051] Examples of thermally activated delayed fluorescence (TADF) emitter-dopants include but are not limited to: 2,5-bis(carbazol-9-yl)-1,4-dicyanobenzene (4CzTPN described in Mater. Horiz., 2014, 1, 264-269; the Organic Luminescent Compound with Delayed Fluorescence of US application 20140145149 to Lin; Chun et al; the delayed fluorescence material of US application 20140138669 to Nakagawa, and Tetsuya (Fukuoka, J P) Adachi, Chihaya (Fukuoka, J P) the benzothiophene or benzofuran fused to a carbazoles delayed fluorescent material of US application 20140145151 to Xia;
[0052] The high-entropy non-crystallizable molecular glass mixture of this invention can increase the operational lifetime of the OLED device when present in an amount of up to 99 wt. % of the emitter-dopant. The increase in operational lifetime is relative to the situation where the non-crystallizable molecular glass mixture is absent. Operational lifetime is commonly defined as the time to reach defined ratio (90%, 70%, or 50%) of the initial luminance at a given temperature and current density.
[0053] High-entropy non-crystallizable molecular glass mixtures are defined as a mixture of compatible organic monomeric molecules with an infinitely low crystallization rate under the most favorable conditions. These mixtures can be formed in a one-part reaction of a multifunctional nucleus with a mixture of substituents. The “non-crystallizability” and the “high-entropy” of the mixture is controlled by the structural dissymmetry of the nucleus, the substituents, or a combination thereof, and the number of components making up the mixture. In cases, where the nucleus is highly symmetric and rigid, the components with similar (non-distinct) substituents might crystallize out under the right conditions. Thus it is advantageous when possible to avoid those components, by designing an asymmetric glass mixture, wherein all the components of the mixture have distinct substituents. Without being bound to theory, we predict that the asymmetric mixtures are more likely to be fully non-crystallizable.
[0054] Increasing the number of components of the glass mixture, by adding more substituents, is another way to enhance the non-crystallizability and the entropy of the glass mixtures having highly symmetric and rigid nuclei.
[0055] The high-entropy non-crystallizable glass mixtures of this invention are described by Molaire in United States Patent Application 2015/0275076, Non-crystallizable Pi-conjugated Molecular Glass Mixtures, Charge Transporting Molecular Glass Mixtures, Luminescent Molecular Glass Mixtures, or Combinations Thereof for Organic Light Emitting Diodes and other Organic Electronics and Photonics Applications; United States Patent Application 20150053894 Charge-transporting Molecular Glass Mixtures, Luminescent Molecular Glass Mixtures, or Combinations Thereof for Organic Light Emitting Diodes and other Organic Electronics and Photonics Applications; United States Patent Application 20150179714 Crosslinkable/Polymerizable and Combinations Thereof Charge-transporting Molecular Glass Mixtures, Luminescent Molecular Glass Mixtures, or Combinations Thereof for Organic Light Emitting Diodes and other Organic Electronics and Photonics Applications and Method of Making Same; WIPO Patent Publication No. WO/2015/148327 PI-CONJUGATED SEMICONDUCTIVE ORGANIC GLASS MIXTURES FOR OLED AND OEDS; WIPO Patent Publication No. WO/2015/117100 NONCRYSTALLIZABLE SENSITIZED LAYERS FOR OLED AND OEDS; WIPO Patent Publication No. WO/2015/031242 MOLECULAR GLASS MIXTURES FOR ORGANIC ELECTRONICS APPLICATIONS; WIPO Patent Publication No. WO/2015/095859 MOLECULAR GLASS MIXTURES FOR ORGANIC ELECTRONICS APPLICATIONS. International PCT Application No. PCT/US2016/052884, “Isomeric and Asymmetric Molecular Glass Mixtures for OLED and Other Organic Electronics and Photonics Applications.”
[0056] In some embodiments, the light-emitting layer includes the high-entropy non-crystallizable glass mixture hosts and dopant-emitter. The high-entropy non-crystallizable glass mixture hosts may include hole-transporting, electron-transporting, or ambipolar. The high-entropy non-crystallizable glass mixture host and the emitter dopant should be chosen so that a hole-transporting host is combined with an electron-trapping emitter-dopant or an electron-transporting host with a hole-trapping emitter-dopant. Ambipolar host can be used with either type of emitter-dopant.
[0057] Specific examples of high-entropy non-crystallizable hosts include those disclosed in International PCT Application No. PCT/US2016/052884, which is incorporated by reference herein in its entirety. Specific examples of high-entropy non-crystallizable hosts include the isomeric hole-transporting materials.
[0058] Hole-Transporting Isomeric Asymmetric Glass Mixture 7 contains the following compounds:
##STR00001## ##STR00002##
[0059] Ambipolar Isomeric Asymmetric Glass Mixture 8 contains the following compounds:
##STR00003## ##STR00004##
[0060] Ambipolar Isomeric asymmetric glass mixture 6 contains the following compounds:
##STR00005## ##STR00006##
[0061] Ambipolar Isomeric asymmetric glass mixture 4 contains the following compounds:
##STR00007## ##STR00008##
[0062] Electron-Transporting Isomeric Asymmetric Glass Mixture 9 contains the following compounds:
##STR00009## ##STR00010##
[0063] The non-crystallizable hole-transporting materials of United States Patent Application 2015/0275076, Non-crystallizable Pi-conjugated Molecular Glass Mixtures, Charge Transporting Molecular Glass Mixtures, Luminescent Molecular Glass Mixtures, or Combinations Thereof for Organic Light Emitting Diodes and other Organic Electronics and Photonics Applications.
[0064] Hole-Transporting Isomeric Glass Mixture 22 contains the following compounds:
##STR00011## ##STR00012##
[0065] Ambipolar Isomeric Glass Mixture 32 contains the following compounds:
##STR00013## ##STR00014##
[0066] Other examples of non-crystallizable mixtures include Glass Mixtures 50, 60, 65, 70, 75, and 80.
[0067] Hole-Transporting Isomeric Glass Mixture 50 contains the following compounds:
##STR00015## ##STR00016## ##STR00017##
[0068] Ambipolar Glass Mixture 60 contains the following compounds:
##STR00018## ##STR00019##
[0069] Ambipolar Glass Mixture 65 contains the following compounds:
##STR00020## ##STR00021##
[0070] Hole-Transporting Glass Mixture 70 contains the following compounds:
##STR00022## ##STR00023##
[0071] Ambipolar Glass Mixture 75 contains the following compounds:
##STR00024## ##STR00025## ##STR00026##
[0072] Electron-Transporting Glass Mixture 80 contains the following compounds:
##STR00027## ##STR00028##
[0073] Ambipolar Glass Mixture 85 contains the following compounds:
##STR00029## ##STR00030## ##STR00031##
[0074] Ambipolar Glass Mixture 90 contains the following compounds:
##STR00032## ##STR00033##
[0075] Hole-Transporting Glass Mixture 95 contains the following compounds:
##STR00034## ##STR00035## ##STR00036##
[0076] Ambipolar Glass Mixture 100 contains the following compounds:
##STR00037## ##STR00038## ##STR00039##
[0077] Ambipolar Glass Mixture 105 contains the following compounds:
##STR00040## ##STR00041## ##STR00042##
[0078] Ambipolar Glass Mixture 110 contains the following compounds:
##STR00043## ##STR00044## ##STR00045##
[0079] Hole-Transporting Glass Mixture 115 contains the following compounds:
##STR00046## ##STR00047## ##STR00048##
[0080] Electron-Transporting Glass Mixture 120 contains the following compounds:
##STR00049## ##STR00050##
[0081] Hole-Transporting Glass Mixture 121 contains the following compounds:
##STR00051## ##STR00052## ##STR00053##
[0082] Hole-Transporting Glass Mixture 122 contains the following compounds:
##STR00054## ##STR00055##
[0083] Ambipolar Glass Mixture 123 contains the following compounds:
##STR00056## ##STR00057##
[0084] Ambipolar Glass Mixture 124 contains the following compounds:
##STR00058## ##STR00059##
[0085] Electron-Transporting Glass Mixture 125 contains the following compounds:
##STR00060##
[0086] Hole-Transporting Glass Mixture 126 contains the following compounds:
##STR00061## ##STR00062##
[0087] Hole-Transporting Glass Mixture 127 contains the following compounds:
##STR00063## ##STR00064## ##STR00065## ##STR00066##
[0088] Hole-Transporting Glass Mixture 128 contains the following compounds:
##STR00067## ##STR00068##
[0089] Electron-Transporting Glass Mixture 129 contains the following compounds:
##STR00069## ##STR00070##
[0090] Hole-Transporting Glass Mixture 130 contains the following compounds:
##STR00071## ##STR00072##
[0091] Electron-Transporting Glass Mixture 132 contains the following compounds:
##STR00073## ##STR00074##
[0092] Hole-Transporting Glass Mixture 133 contains the following compounds:
##STR00075## ##STR00076##
[0093] Hole-Transporting Glass Mixture 134 contains the following compounds:
##STR00077## ##STR00078##
[0094] Electron-Transporting Glass Mixture 135 contains the following compounds:
##STR00079##
General Device Architecture
[0095] Embodiments of this disclosure include very simple structures comprising a single anode and cathode to more complex devices, such as passive matrix displays comprised of orthogonal arrays of anodes and cathodes to form pixels, and active-matrix displays where each pixel is controlled independently, for example, with a thin film transistor (TFT).
[0096] There are numerous configurations of the organic layers wherein the present invention can be successfully practiced. Essential requirements are a cathode, an anode, an HTL and an LEL. A more typical structure is shown in
Substrate
[0097] The substrate 101 can either be light transmissive or opaque, depending on the intended direction of light emission. The light transmissive property is desirable for viewing the EL emission through the substrate. Transparent glass or organic material are commonly employed in such cases. For applications where the EL emission is viewed through the top electrode, the transmissive characteristic of the bottom support is immaterial, and therefore can be light transmissive, light absorbing or light reflective. Substrates for use in this case include, but are not limited to, glass, plastic, semiconductor materials, ceramics, and circuit board materials. Of course it is necessary to provide in these device configurations a light-transparent top electrode.
Anode
[0098] The conductive anode layer 103 is commonly formed over the substrate and, when EL emission is viewed through the anode, should be transparent or substantially transparent to the emission of interest. Common transparent anode materials used in this invention are indium-tin oxide (ITO) and tin oxide, but other metal oxides can work including, but not limited to, aluminum- or indium-doped zinc oxide (IZO), magnesium-indium oxide, and nickel-tungsten oxide. In addition to these oxides, metal nitrides, such as gallium nitride, and metal selenides, such as zinc selenide, and metal sulfides, such as zinc sulfide, can be used in layer 103. For applications where EL emission is viewed through the top electrode, the transmissive characteristics of layer 103 are immaterial and any conductive material can be used, transparent, opaque or reflective. Example conductors for this application include, but are not limited to, gold, iridium, molybdenum, palladium, and platinum. Typical anode materials, transmissive or otherwise, have a work function of 4.1 eV or greater. Desired anode materials are commonly deposited by any suitable means such as evaporation, sputtering, chemical vapor deposition, or electrochemical means. Anodes can be patterned using well-known photolithographic processes.
Hole-Injecting Layer (HIL)
[0099] Optionally, a hole-injecting layer 105 be provided between anode 103 and hole-transporting layer 107. The hole-injecting material can serve to improve the film formation property of subsequent organic layers and to facilitate injection of holes into the hole-transporting layer. Suitable materials for use in the hole-injecting layer include, but are not limited to, porphyrinic compounds such as those described in U.S. Pat. No. 4,720,432, and plasma-deposited fluorocarbon polymers such as those described in U.S. Pat. No. 6,208,075. Alternative hole-injecting materials reportedly useful in organic EL devices are described in EP 0 891 121 A1 and EP 1 029 909 A1.
Hole-Transporting Layer (HTL)
[0100] The hole-transporting layer 107 of the organic EL device contains at least one hole-transporting compound such as an aromatic tertiary amine, where the latter is understood to be a compound containing at least one trivalent nitrogen atom that is bonded only to carbon atoms, at least one of which is a member of an aromatic ring. In one form the aromatic tertiary amine can be an arylamine, such as a monoarylamine, diarylamine, triarylamine, or a polymeric arylamine group. Exemplary monomeric triarylamines are illustrated by Klupfel et al. U.S. Pat. No. 3,180,730. Other suitable triarylamines substituted with one or more vinyl radicals and/or comprising at least one active hydrogen containing group are disclosed by Brantley et al U.S. Pat. Nos. 3,567,450 and 3,658,520.
[0101] One particular class of aromatic tertiary amines includes those which include at least two aromatic tertiary amine moieties as described in U.S. Pat. Nos. 4,720,432 and 5,061,569. Such compounds include those represented by structural formula (II).
##STR00080##
[0102] In formula (II), Q.sub.1 and Q.sub.2 are independently selected aromatic tertiary amine moieties and G is a linking group such as an arylene, cycloalkylene, or alkylene group of a carbon to carbon bond. In one embodiment, at least one of Q.sub.1 or Q.sub.2 contains a polycyclic fused ring group, e.g., a naphthalene. When G is an aryl group, it is conveniently a phenylene, biphenylene, or naphthalene group.
[0103] A useful class of triarylamine groups satisfying structural formula (II) and containing two triarylamine groups is represented by structural formula (III):
##STR00081##
[0104] In formula (III), R.sup.11 and R.sup.12 each independently represents a hydrogen atom, an aryl group, or an alkyl group or R.sup.11 and R.sup.12 together represent the atoms completing a cycloalkyl group; and R.sup.13 and R.sup.14 each independently represents an aryl group, which is in turn substituted with a diaryl substituted amino group, as indicated by structural formula (IV):
##STR00082##
[0105] In formula (IV), R.sup.15 and R.sup.16 are independently selected aryl groups. In one embodiment, at least one of R.sup.15 and R.sup.16 contains a polycyclic fused ring group, e.g., a naphthalene.
[0106] Another class of aromatic tertiary amine groups are the tetraaryldiamines. Tetraaryldiamines groups include two diarylamino groups, such as indicated by formula (IV), linked through an arylene group. Useful tetraaryldiamines include those represented by formula (V):
##STR00083##
[0107] In formula (V), Are is selected from arylene group, such as a phenylene or anthracene group, n is an integer of from 1 to 4, and Ar, R.sup.7, R.sup.8, and R.sup.9 are independently selected aryl groups.
[0108] In a typical embodiment, at least one of Ar, R.sup.7, R.sup.8, and R.sup.9 is a polycyclic fused ring group, e.g., a naphthalene.
[0109] The various alkyl, alkylene, aryl, and arylene groups of the foregoing structural formulae (II), (III), (IV), (V), can each in turn be substituted. Typical substituents include alkyl groups, alkoxy groups, aryl groups, aryloxy groups, and halogen such as fluoride, chloride, and bromide. The various alkyl and alkylene groups typically contain from about 1 to 6 carbon atoms. The cycloalkyl moieties can contain from 3 to about 10 carbon atoms, but typically contain five, six, or seven ring carbon atoms—e.g., cyclopentyl, cyclohexyl, and cycloheptyl ring structures. The aryl and arylene groups are usually phenyl and phenylene moieties.
[0110] The hole-transporting layer can be formed of a single or a mixture of aromatic tertiary amine compounds. Specifically, one may employ a triarylamine, such as a triarylamine satisfying the formula (III), in combination with a tetraaryldiamine, such as indicated by formula (V). When a triarylamine is employed in combination with a tetraaryldiamine, the latter is positioned as a layer interposed between the triarylamine and the electron injecting and transporting layer. Illustrative of useful aromatic tertiary amines are the following:
[0111] 1,1 Bis(4-di-p-tolylaminophenyl)cyclohexane
[0112] 1,1-Bis(4-di-p-tolylaminophenyl)-4-phenylcyclohexane
[0113] 4,4′-Bis(diphenylamino)quadriphenyl
[0114] Bis(4-dimethylamino-2-methylphenyl)-phenylmethane
[0115] N,N,N-Tri(p-tolyl)amine
[0116] 4-(di-p-tolylamino)-4′-[4(di-p-tolylamino)-styryl]stilbene
[0117] N,N,N′,N′-Tetra-p-tolyl-4-4′-diaminobiphenyl
[0118] N,N,N′,N′-Tetraphenyl-4,4′-diaminobiphenyl
[0119] N,N,N′,N′-tetra-l-naphthyl-4,4′-diaminobiphenyl
[0120] N,N,N′,N′-tetra-2-naphthyl-4,4′-diaminobiphenyl
[0121] N-Phenylcarbazole
[0122] 4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl
[0123] 4,4′-Bis[N-(1-naphthyl)-N-(2-naphthyl)amino]biphenyl
[0124] 4,4″-Bis[N-(1-naphthyl)-N-phenylamino]p-terphenyl
[0125] 4,4′-Bis[N-(2-naphthyl)-N-phenylamino]biphenyl
[0126] 4,4′-Bis[N-(3-acenaphthenyl)-N-phenylamino]biphenyl
[0127] 1,5-Bis[N-(1-naphthyl)-N-phenylamino]naphthalene
[0128] 4,4′-Bis[N-(9-anthryl)-N-phenylamino]biphenyl
[0129] 4,4″-Bis[N-(1-anthryl)-N-phenylamino]-p-terphenyl
[0130] 4,4′-Bis[N-(2-phenanthryl)-N-phenylamino]biphenyl
[0131] 4,4′-Bis[N-(8-fluoranthenyl)-N-phenylamino]biphenyl
[0132] 4,4′-Bis[N-(2-pyrenyl)-N-phenylamino]biphenyl
[0133] 4,4′-Bis[N-(2-naphthacenyl)-N-phenylamino]biphenyl
[0134] 4,4′-Bis[N-(2-perylenyl)-N-phenylamino]biphenyl
[0135] 4,4′-Bis[N-(1-coronenyl)-N-phenylamino]biphenyl
[0136] 2,6-Bis(di-p-tolylamino)naphthalene
[0137] 2,6-Bis[di-(1-naphthyl)amino]naphthalene
[0138] 2,6-Bis[N-(1-naphthyl)-N-(-2-naphthyl)amino]naphthalene
[0139] N,N,N′,N′-Tetra(2-naphthyl)-4,4″-diamino-p-terphenyl
[0140] 4,4′-Bis[N-phenyl-N-[4-(1-naphthyl)-phenyl]amino]biphenyl
[0141] 4,4′-Bis[N-phenyl-N-(2-pyrenyl)amino]biphenyl
[0142] 2,6-Bis[N,N-di(2-naphthyl)amine]fluorine
[0143] 1,5-Bis[N-(1-naphthyl)-N-phenylamino]naphthalene
[0144] Another class of useful hole-transporting materials includes polycyclic aromatic compounds as described in EP 1 009 041. In addition, polymeric hole-transporting materials can be used such as poly(N-vinylcarbazole) (PVK), polythiophenes, polypyrrole, polyaniline, and copolymers such as poly(3,4-ethylenedioxythiophene)/poly (4-styrenesulfonate) also called PEDOT/PSS.
[0145] Light-Emitting Layer (LEL)
[0146] As more fully described in U.S. Pat. Nos. 4,769,292 and 5,935,721, the light-emitting layer (LEL) 109 of the OLED multilayer electroluminescent device includes a host and an emitter-dopant. The emitter dopant is chosen from luminescent material or fluorescent material where electroluminescence is produced as a result of electron-hole pair recombination in this region. The luminescent material can also phosphorescent or thermally delayed fluorescent. The host materials in the light-emitting layer can be an electron-transporting material, as defined below, a hole-transporting material, as defined above, or another material or combination of materials that support hole-electron recombination. The emitter-dopant is usually chosen from highly fluorescent dyes, but phosphorescent compounds, e.g., transition metal complexes as described in WO 98/55561, WO 00/18851, WO 00/57676, and WO 00/70655 are also useful. Emitter-dopants are typically coated as 0.01 to 10% by weight into the host material.
[0147] An important relationship for choosing a dye as a dopant is a comparison of the bandgap potential which is defined as the energy difference between the highest occupied molecular orbital and the lowest unoccupied molecular orbital of the molecule. For efficient energy transfer from the host to the dopant molecule, a necessary condition is that the band gap of the dopant is smaller than that of the host material.
[0148] Emitting molecules known to be of use include, but are not limited to, those disclosed in U.S. Pat. Nos. 4,768,292, 5,141,671, 5,150,006, 5,151,629, 5,405,709, 5,484,922, 5,593,788, 5,645,948, 5,683,823, 5,755,999, 5,928,802, 5,935,720, 5,935,721, and 6,020,078.
Testing Process:
[0149] All OLEDs are fabricated on glass substrates pre-coated with 145 nm of ITO. The substrates are cleaned in standard Ultra T cleaner tool and baked at 120° C. for 2 hours. Next, the substrates are transferred into a vacuum chamber for sequential deposition of organic layers by thermal evaporation under a vacuum 10.sup.−6-10.sup.−7 Torr. During deposition, layer thicknesses and doping concentrations are controlled using calibrated deposition sensors. Next, a bilayer of 0.5 nm LiF 1125 nm Al was deposited to form a cathode. Devices are encapsulated using standard metal can with UV adhesive and desiccant. The device emission area is 0.1 cm.sup.2. No light extraction enhancement was used.
[0150] After OLED processing, all samples are fully characterized using the standard test procedures. The standard test procedures include powering the devices using a Keithly 2400 power supply and measuring the electrical-optical characteristics using a PR-650 spectrophotometer. External quantum efficiencies (EQE) is calculated assuming that device emission is lambertian.
[0151] Aging Test
[0152] The samples are aged at a constant current density of 20 mA/cm2. The luminance is measured at the beginning of the test and followed during the aging period, as well as the voltage. Devices were run until 20% of the luminance was decayed (T80).
[0153] A linear regression model is obtained for the luminance Vs current curve. The regression model is used to calculate the required current for a specific luminance, for example 3000 or 1000 nits. Then the ratio of the aging current to the current to 3000 or 1000 nits is calculated:
[0154] (20 mA/cm.sup.2)/(calculated current)=Ratio (3000 nits) or Ratio (1000 nits) (A)
[0155] Ratiô1.5=Multiplier where 1.5 is the acceleration factor determined by experiment (B)
[0156] The measured T80@20 mA/cm.sup.2)=T80(measured) (C)
[0157] Then T80@calculated current=T80(measured)*Multiplier
[0158] Then T70 at (3000 nits) or T70@(1000 nits)=2.5*T80@calculated current
EXAMPLES
[0159] The main materials used are shown in Table 1 below.
##STR00084## ##STR00085##
Comparative Example C1
Conventional Host mCBP
[0160] A set of devices were made according to the procedure described above in the Test Procedures, using mCBP, a hole-transporting host. The properties of mCBP are listed in Table 1. The general structure of the devices is shown in Table 2. The concentration of proprietary yellow phosphorescent emitter provided by the device fabricating service company OLEDworks LLC., was varied at 4, 8,18, 36 wt. %. The hole-blocking layer used is also a proprietary electron-transporting material provided by the device fabricating service company OLEDworks LLC. The fabricated devices shown in Table 3 were tested according to the procedure described above. The results are shown on Table 3.
TABLE-US-00001 TABLE 2 OLED Device Arrangement of Comparative Example C1 and Examples 1 and 2. HIL HTL EBL EML HBL ETL EIL Cathode ITO HATCN NPB TCTA or Neat mCBP Vs HBL TBPi EIL LiF AI NONE Neat Noncrystallizable hole transport host Emitter Concentration: 4%, 8%, 16%, 32%
TABLE-US-00002 TABLE 3 Lifetime Expectancy of Comparative Example C1 Lum Luminance % Voltage Yield, T80, hr @ @ 20 T80, hr @ Device Host Emitter EBL V Cd/A Lm/W % EQE 20 mA/cm.sup.2 mA/cm2 1000 cd/m.sup.2 A m-CBP 4% None 6.8 23.3 10.8 6.4 32 3550 260 B m-CBP 8% None 4.8 51.2 35.7 13.8 14 6830 515 E m-CBP 16% None 4.0 42.3 33.6 11.5 4 7730 33 F m-CBP 32% None 3.8 23.9 19.8 6.6 2 4330 19 C m-CBP 8% TCTA 5.7 51.7 28.6 13.9 17 4260 642 D m-CBP 16% TCTA 4.6 47.3 32.5 12.9 4 4660 61
Example 1
High-Entropy Non-Crystallizable Hole-Transporting Host
[0161] Another set of devices were fabricated using the design, materials and procedure of Comparative Example C1, except that the high-entropy non-crystallizable hole-transporting glass mixture host 1 (Glass Mixture 22). The results are shown in Table 4 below. The T80 lifetimes at 1000 cd/m.sup.2 for Comparative Example C1 and Example 1 are plotted in
[0162] In
[0163] The T80 lifetime is longer for the high-entropy non-crystallizable hole-transporting glass mixture host, Example 1, lasting up to 2,169 hours, as opposed to the Comparative Example lasting 642 hours. Example 1 had a T80 lifetime that was increased by 600% when compared to the Comparative Example. This increase in T80 lifetime is attributed to the high-entropy non-crystallizable hole-transporting glass mixture host. The increase in lifetime is further attributed to the suppression of emitter aggregation by the high-entropy host in Example 1.
[0164] In
Example 2
High-Entropy Non-Crystallizable Ambipolar Host
[0165] Three devices were fabricated using the procedure of inventive example 1 at 4 and 8% emitter and the host replaced by the high-entropy ambipolar isomeric asymmetric glass mixture 4.
[0166] The results are shown in Table 5 and the T80 1000 cd/m.sup.2 life data plotted as shown in
TABLE-US-00003 TABLE 5 Lifetime Expectancy of High-entropy Non-Crystallizable Hole-Transporting Host (Example 2) Lum % Voltage Yield Efficacy LT80, hr @ LT95, hr @ LT80, hr @ Device Host Emitter EBL V Cd/A Lm/W % EQE 20 mA/cm.sup.2 1000 cd/m.sup.2 1000 cd/m.sup.2 G Non-Crystallizable 4% TCTA 5.0 70.7 44.1 18.9 18 122 1,229 Ambipolar Host H Non-Crystallizable 4% None 4.7 31.7 21.0 8.4 311 525 4,276 Ambipolar Host I Non-Crystallizable 8% None 4.4 46.7 33.6 12.4 138 307 4,322 Ambipolar Host
[0167] In
Inventive Example 3
Mixed Host
[0168] A set of devices were fabricated according to the procedure used for the other devices. The structure of the devices is shown in Table 6. A mixed-host system was used consisting of 25 wt. % of hole-transporting (host glass mixture 22) and 59 wt. % of the proprietary electron-transporting host provided by the device testing service company, OLEDWorks LLC. The concentration of the emitter was set at 16 wt. %. One of the devices used the conventional mCBP 55 hole-transporting host; the other used the high-entropy non-crystallizable hole-transporting molecular glass mixture of this invention. Both devices include a TCTA exciton/electron blocking layer.
[0169] The results for the two devices are shown in Table 7. Both devices exhibited high external quantum efficiency of 19.5%. However, the lifetime for the Device I, which contained the high-entropy non-crystallizable hole-transporting molecular glass mixture (Glass Mixture 22) exhibited significantly longer lifetime of 9,398 hr, as compared to 3,650 hr of the Comparative Example, Device D as shown in Table 7.
TABLE-US-00004 TABLE 6 Structure of Device for Example 3 anode HIL HTL EBL1 EBL2 EML HBL ETL EIL Cathode ITO HATCN NPB TCTA Noncrystallizable HT-Host (25%) HBL TBPi EIL LiF AI hole transport ET-Host (59%) Phosphorescent Yellow Emitter Concentration set @ 16%
TABLE-US-00005 TABLE 7 Lifetime Expectancy of High-entropy Non-Crystallizable Hole-Transporting Host (Example 3) Lum % % % Voltage, Yield, Efficacy, T80, hr @ T80, hr @ Device Host ET-Co-Host HT-Host Emitter ETL V Cd/A Lm/W % EQE 20 mA/cm2 1000 cd/m.sup.2 D m-CBP 59 25 16 TCTA 5.5 68.9 39.0 19.5 172 3,650 I Non- 59 25 16 TCTA 5.1 68.1 41.7 19.2 156 9,398 crystallizable hole transport host
Inventive Example 4
Mixed Host
[0170] A set of devices were fabricated according to the procedure used for the other devices. The structure of the devices is shown in Table 8. A mixed-host system was used consisting of 25 wt. % of a hole-transporting host and 60 wt. % of the proprietary electron-transporting host provided by the device testing service company, OLEDWorks LLC. The concentration of the emitter was set at 15 wt. %. Three devices used the high-entropy non-crystallizable hole-transporting molecular glass mixture (Glass Mixture 22) with TCTA, the high-entropy non-crystallizable hole-transporting molecular glass mixture, or a combination of TCTA and the high-entropy non-crystallizable hole-transporting molecular glass mixture as exciton/electron blocking layers (EBL). One of the devices used 60% of a proprietary commercially available electron-transporting host (no hole-transporting host) and TCTA as EBL.
[0171] The results for the four devices are shown in Table 9. All four devices similarly exhibited high external quantum efficiency (18 to 19.5%). However, the lifetime for the devices containing even just 25% of the non-crystallizable hole-transporting molecular glass mixture exhibited significantly longer lifetime.
TABLE-US-00006 TABLE 8 Structure of Device for Example 4 anode HIL HTL EBL1 EBL2 EML HBL ETL EIL Cathode ITO HATCN NPB TCTA Noncrystallizable Emitter Concentration HBL TBPi EIL LiF AI hole transport @ 15% HT Host (25%)/ET Host(60%) or ET Host (75%)
TABLE-US-00007 TABLE 9 Lifetime Expectancy of High-entropy Non-Crystallizable Hole-Transporting Host (Example 4) Lum Lumen % Yield Yield LT80 @ LT80 @ Device EBL1 EBL2 ET-Host HT-Host Emitter Voltage cd/amp Lm/watt % EQE 20 mA/cm2 1000 cd/m2 A None Noncrystallizable 85% 0% 15% 4.3 61.6 44.7 18.8 62 1742 Hole Transport C None Noncrystallizable 60% 25% 15% 4.3 60.8 44.3 18.4 70 3459 Hole Transport E TCTA Noncrystallizable 60% 25% 15% 3.7 58.8 49.3 17.5 140 6170 Hole Transport F TCTA Noncrystallizable 60% 25% 15% 3.9 60.5 48.7 18 140 7227 Hole Transport
[0172] The external quantum efficiency (% EQE) versus current for four devices was plotted in
[0173] In