Organic Semiconducting Material Comprising an Electrical n-Dopant and an Electron Transport Matrix and Electronic Device Comprising the Semiconducting Material

Abstract

The present invention relates to an organic semiconducting material and to an electronic device comprising the semiconducting material, particularly to an electroluminescent device, particularly to an organic light emitting diode (OLED), wherein the semiconducting material comprises a first electron transport matrix compound and an electrical n-dopant; the invention pertains also to a device comprising the electric device and/or the electroluminescent device, particularly to a display device, particularly to a display device comprising the OLED.

Claims

1. An organic semiconducting material comprising at least one electron transport matrix and at least one electrical n-dopant, wherein the electron transport matrix comprises at least one first matrix compound according to Chemical Formula I: ##STR00048## wherein A.sup.1, A.sup.2, A.sup.3 and A.sup.4 is independently selected from single bond, an unsubstituted or substituted C.sub.6 to C.sub.30 arylene and an unsubstituted or substituted C.sub.1 to C.sub.30 heteroarylene; A.sup.5 is selected from an unsubstituted or substituted C.sub.6 to C.sub.40 aryl group and/or from an unsubstituted or substituted C.sub.2 to C.sub.40 heteroaryl group; R.sup.1 to R.sup.5 are independently a substituted or unsubstituted C.sub.6 to C.sub.30 aryl group, a substituted or unsubstituted C.sub.2 to C.sub.30 heteroaryl group; a to e are independently an integer of 0 or 1 and 4a+b+c+d+e5; wherein, in formula (I), in the substituted group, at least one hydrogen is replaced by (i) deuterium, (ii) a halogen, (iii) a C.sub.2 to C.sub.60 tertiary amino group, wherein the nitrogen atom of the tertiary amino group is substituted with two independently selected C.sub.1 to C.sub.30 hydrocarbyl groups or the nitrogen atom of the C.sub.2 to C.sub.60 tertiary amino group forms a C.sub.1 to C.sub.30 heterocyclic group, (iv) a C.sub.2 to C.sub.60 phosphine oxide group, wherein the phosphorus atom of the phosphine oxide group is substituted with two C.sub.1 to C.sub.30 groups independently selected from hydrocarbyl, halogenated hydrocarbyl and hydrocarbyloxy or the phosphorus atom of the phosphine oxide group forms a C.sub.1 to C.sub.30 heterocyclic group, (v) a C.sub.1 to C.sub.22 silyl group, (vi) a C.sub.1 to C.sub.30 alkyl group, (vii) a C.sub.1 to C.sub.10 alkylsilyl group, (viii) a C.sub.6 to C.sub.22 arylsilyl group, (ix) a C.sub.3 to C.sub.30 cycloalkyl group, (x) a C.sub.2 to C.sub.30 heterocycloalkyl group, (xi) a C.sub.6 to C.sub.30 aryl group, (xii) a C.sub.2 to C.sub.30 heteroaryl group, (xiii) a C.sub.1 to C.sub.20 alkoxy group, (xiv) a C.sub.1 to C.sub.30 perfluoro-hydrocarbyl group, (xv) a C.sub.1 to C.sub.10 trifluoroalkyl group, or (xvi) a cyano group.

2. The organic semiconducting material according to claim 1, wherein the electrical n-dopant is selected from elemental metals, metal salts, metal complexes and organic radicals.

3. The organic semiconducting material according to claim 1, wherein the electrical n-dopant is selected from alkali metal salts and alkali metal complexes.

4. The organic semiconducting material according to claim 1, wherein the electrical n-dopant is a redox n-dopant.

5. The organic semiconducting material according to claim 1, wherein the redox n-dopant is selected from an elemental metal, an electrically neutral metal complex and/or an electrically neutral organic radical.

6. The organic semiconducting material according to claim 5, wherein the electrically neutral metal complex and/or the electrically neutral organic radical, has a redox potential which has a value which is more negative than 0.5 V, if measured by cyclic voltammetry against ferrocene/ferrocenium reference redox couple.

7. The organic semiconducting material according to claim 4, wherein the redox n-dopant is an electropositive elemental metal selected from alkali metals, alkaline earth metals, rare earth metals, and transition metals Ti, V, Cr and Mn.

8. The organic semiconducting material according to claim 1, wherein the first matrix compound is a compound according to Chemical Formula (Ia) ##STR00049## wherein, in Chemical Formula Ia, Ar.sup.1 is selected from C.sub.6 to C.sub.12 arylene and C.sub.1 to C.sub.11 heteroarylene; and R.sup.1 to R.sup.5 are independently a substituted or unsubstituted C6 to C30 aryl group, a substituted or unsubstituted C.sub.2 to C.sub.30 heteroaryl group; a to e are independently an integer of 0 or 1 and 4a+b+c+d+e5; L is a single bond, a substituted or unsubstituted C.sub.6 to C.sub.30 arylene group, or a substituted or unsubstituted C.sub.2 to C.sub.30 heteroarylene group; ET is a unsubstituted C.sub.6 to C.sub.40 aryl or C.sub.5 to C.sub.40 heteroaryl group; or a substituted C.sub.6 to C.sub.40 aryl or C.sub.5 to C.sub.40 heteroaryl group, wherein, in formula (Ia), in the substituted group, at least one hydrogen is replaced by (i) deuterium, (ii) a halogen, (iii) a C.sub.2 to C.sub.60 tertiary amino group, wherein the nitrogen atom of the C.sub.2 to C.sub.60 tertiary amino group is substituted with two independently selected C.sub.1 to C.sub.30 hydrocarbyl groups or forms a C.sub.1 to C.sub.30 heterocyclic group, (iv) a C.sub.2 to C.sub.60 phosphine oxide group, wherein the phosphorus atom of the phosphine oxide group is substituted with two C.sub.1 to C.sub.30 groups independently selected from hydrocarbyl, halogenated hydrocarbyl and hydrocarbyloxy or the phosphorus atom of the phosphine oxide group forms a C.sub.1 to C.sub.30 heterocyclic group, (v) a C.sub.1 to C.sub.22 silyl group, (vi) a C.sub.1 to C.sub.30 alkyl group, (vii) a C.sub.1 to C.sub.10 alkylsilyl group, (viii) a C.sub.6 to C.sub.22 arylsilyl group, (ix) a C.sub.3 to C.sub.30 cycloalkyl group, (x) a C.sub.2 to C.sub.30 heterocycloalkyl group, (xi) a C.sub.6 to C.sub.30 aryl group, (xii) a C.sub.2 to C.sub.30 heteroaryl group, (xiii) a C.sub.1 to C.sub.20 alkoxy group, (xiv) a C.sub.1 to C.sub.30 perfluoro-hydrocarbyl group, (xv) a C.sub.1 to C.sub.10 trifluoroalkyl group, or (xvi) a cyano group.

9. The organic semiconducting material according to claim 1, wherein the first matrix compound is a compound according to Chemical Formula (Ib) ##STR00050## wherein in Chemical Formula Ib: X.sup.1 to X.sup.11 are independently, N, C, or CR.sup.a; R.sup.a is independently, hydrogen, deuterium, a C.sub.1 to C.sub.30 alkyl group, a C.sub.3 to C.sub.30 cycloalkyl group, a C.sub.6 to C.sub.30 aryl group, a C.sub.6 to C.sub.30 diarylamine group, a C.sub.1 to C.sub.30 alkoxy group, a C.sub.3 to C.sub.21 silyl group, a C.sub.3 to C.sub.21 silyloxy group, a C.sub.1 to C.sub.30 alkylthiol group, a C.sub.6 to C.sub.30 arylthiol group, a halogen, a C.sub.1 to C.sub.30 halogenated hydrocarbyl group, a cyano group; R.sup.1 to R.sup.5 are independently a substituted or unsubstituted C.sub.6 to C.sub.30 aryl group, a substituted or unsubstituted C.sub.2 to C.sub.30 heteroaryl group; a to e are independently an integer of 0 or 1 and 4a+b+c+d+e5, L is a single bond, a substituted or unsubstituted C.sub.6 to C.sub.30 arylene group, a substituted or unsubstituted C.sub.2 to C.sub.30 heteroarylene group, and ET is a unsubstituted C.sub.6 to C.sub.40 aryl or C.sub.2 to C.sub.40 heteroaryl group, or a substituted C.sub.6 to C.sub.40 aryl or C.sub.2 to C.sub.40 heteroaryl group; wherein, in formula (Ib), in the substituted group, at least one hydrogen is replaced by (i) deuterium, (ii) a halogen, (iii) a C.sub.1 to C.sub.60 tertiary amino group, wherein the nitrogen atom of the C.sub.2 to C.sub.60 tertiary amino group is substituted with two independently selected C.sub.1 to C.sub.30 hydrocarbyl groups or forms a C.sub.1 to C.sub.30 heterocyclic group, a C.sub.2 to C.sub.60 phosphine oxide group, wherein the phosphorus atom of the phosphine oxide group is substituted with two C.sub.1 to C.sub.30 groups independently selected from hydrocarbyl, halogenated hydrocarbyl and hydrocarbyloxy or the phosphorus atom of the phosphine oxide group forms a C.sub.1 to C.sub.30 heterocyclic group, (iv) a C.sub.1 to C.sub.22 silyl group, (v) a C.sub.1 to C.sub.30 alkyl group, (vi) a C.sub.1 to C.sub.10 alkylsilyl group, (vii) a C.sub.6 to C.sub.22 arylsilyl group, (viii) a C.sub.3 to C.sub.30 cycloalkyl group, (ix) a C.sub.2 to C.sub.30 heterocycloalkyl group, (x) a C.sub.6 to C.sub.30 aryl group, (xi) a C.sub.2 to C.sub.30 heteroaryl group, (xii) a C.sub.1 to C.sub.20 alkoxy group, (xiii) a C.sub.1 to C.sub.30 perfluoro-hydrocarbyl group, (xiv) a C.sub.1 to C.sub.10 trifluoroalkyl group, or (xv) a cyano group.

10. The organic semiconducting material according to claim 8, wherein the group ET is a C.sub.2 to C.sub.30 heteroaryl group.

11. The organic semiconducting material according to claim 8, wherein the group ET includes at least one N, with the proviso that the group ET is not a carbazolyl group.

12. An electronic device comprising a first electrode, a second electrode, and arranged between the first and second electrode, a layer of the organic semiconducting material according to claim 1.

13. The electronic device according to claim 12, wherein the layer of the semiconducting material is a charge injection layer or a charge transport layer or a charge generating layer.

14. The electronic device according to claim 12, wherein the electronic device is an electroluminescent device.

15. The electronic device according to claim 12, wherein the electronic device is an organic light emitting diode.

16. A display device comprising an electronic device, wherein the display device comprises an organic light emitting diode according to claim 15.

Description

DESCRIPTION OF THE DRAWINGS

[0228] FIG. 1 is a cross-sectional view showing an organic light emitting diode according to an embodiment of the invention.

[0229] FIGS. 2 and 3 are cross-sectional views specifically showing a part of an organic layer of an organic light emitting diode according to an embodiment of the invention.

[0230] Hereinafter, the figures are illustrated in more detail with reference to examples. However, the present disclosure is not limited to the following figures.

[0231] FIGS. 1 to 3 are schematic cross-sectional views of organic light emitting diodes 100, 300, and 400 according to an embodiment of the present invention. Hereinafter, referring to FIG. 1, a structure of an organic light emitting diode according to an embodiment of the present invention and a method of manufacturing the same are as follows. The organic light emitting diode 100 has a structure where an anode 110, a stack of organic layers 105 including an optional hole transport region; an emission layer 130; and a cathode 150 that are sequentially stacked.

[0232] A substrate may be disposed on the anode 110 or under the cathode 150. The substrate may be selected from usual substrate used in a general organic light emitting diode and may be a glass substrate or a transparent plastic substrate.

[0233] The anode 110 may be formed by depositing or sputtering an anode material on a substrate. The anode material may be selected from materials having a high work function that makes hole injection easy. The anode 110 may be a reflective electrode, a transflective electrode, or a transmissive electrode. The anode material may use indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO.sub.2), zinc oxide (ZnO), and the like. Or, it may be a metal such as silver (Ag), or gold (Au), or an alloy thereof.

[0234] The anode 110 may have a monolayer or a multi-layer structure of two or more layers.

[0235] The organic light emitting diodes 100, 300, and 400 according to an embodiment of the present invention may include a hole transport region; an emission layer 130; and a first electron transport layer 31 comprising a compound according to formula I.

[0236] Referring to FIG. 2, the hole transport region of the stack of organic layers 105 may include at least two layered hole transport layers, and in this case, the hole transport layer contacting the emission layer (130) is defined as a second hole transport layer 135 and a the hole transport layer contacting the anode (110) is defined as a first hole transport layer 34. The stack of organic layers 105 further includes two electron transport layers, namely second electron transport layer 33 and the first electron transport layer 31. The hole transport region of the stack 105 may further include at least one of a hole injection layer, a hole transport layer, an electron blocking layer, and a buffer layer.

[0237] The hole transport region of the stack 105 may include only hole injection layer or only hole transport layer. Or, the hole transport region may have a structure where a hole injection layer 36/hole transport layer 34 or hole injection layer 36/hole transport layer 34/electron blocking layer (135) is sequentially stacked from the anode 110.

[0238] For example, the hole injection layer 36 and the electron injection layer 37 can be additionally included, so that an OLED may comprise an anode 110/hole injection layer 36/first hole transport layer 34/electron blocking layer 135/emission layer 130/second electron transport layer 33/first electron transport layer 31/electron injection layer 37/cathode 150, which are sequentially stacked.

[0239] According to another aspect of the invention, the organic electroluminescent device (400) comprises an anode (110), a hole injection layer (36), a first hole transport layer (34), optional an electron blocking layer (135), an emission layer (130), second electron transport layer (33), first electron transport layer (31), an optional electron injection layer (37), a cathode (150) wherein the layers are arranged in that order.

[0240] The hole injection layer 36 may improve interface properties between ITO as an anode and an organic material used for the hole transport layer 34, and is applied on a non-planarized ITO and thus planarizes the surface of the ITO. For example, the hole injection layer 36 may include a material having a median value of the energy level of its highest occupied molecular orbital (HOMO) between the work function of ITO and the energy level of the HOMO of the hole transport layer 34, in order to adjust a difference between the work function of ITO as an anode and the energy level of the HOMO of the first hole transport layer 34.

[0241] When the hole transport region includes a hole injection layer 36, the hole injection layer may be formed on the anode 110 by any of a variety of methods, for example, vacuum deposition, spin coating, casting, Langmuir-Blodgett (LB) method, or the like.

[0242] When hole injection layer is formed using vacuum deposition, vacuum deposition conditions may vary depending on the material that is used to form the hole injection layer, and the desired structure and thermal properties of the hole injection layer to be formed and for example, vacuum deposition may be performed at a temperature of about 100 C. to about 500 C., a pressure of about 10.sup.6 Pa to about 10.sup.1 Pa, and a deposition rate of about 0.1 to about 10 nm/sec, but the deposition conditions are not limited thereto.

[0243] When the hole injection layer is formed using spin coating, the coating conditions may vary depending on the material that is used to form the hole injection layer, and the desired structure and thermal properties of the hole injection layer to be formed. For example, the coating rate may be in the range of about 2000 rpm to about 5000 rpm, and a temperature at which heat treatment is performed to remove a solvent after coating may be in a range of about 80 C. to about 200 C., but the coating conditions are not limited thereto.

[0244] Conditions for forming the hole transport layer and the electron blocking layer may be defined based on the above-described formation conditions for the hole injection layer.

[0245] A thickness of the hole transport part of the charge transport region may be from about 10 nm to about 1000 nm, for example, about 10 nm to about 100 nm. When the hole transport transport part of the charge transport region includes the hole injection layer and the hole transport layer, a thickness of the hole injection layer may be from about 10 nm to about 1000 nm, for example about 10 nm to about 100 nm and a thickness of the hole transport layer may be from about 5 nm to about 200 nm, for example about 10 nm to about 150 nm. When the thicknesses of the hole transport part of the charge transport region, the HIL, and the HTL are within these ranges, satisfactory hole transport characteristics may be obtained without a substantial increase in driving voltage.

[0246] Hole transport matrix materials used in the hole transport region are not particularly limited. Preferred are covalent compounds comprising a conjugated system of at least 6 delocalized electrons. The term covalent compound is in more detail explained below, in the paragraph regarding the second electron transport matrix. Typical examples of hole transport matrix materials which are widely used in hole transport layers are polycyclic aromatic hydrocarbons, triaryl amine compounds and heterocyclic aromatic compounds. Suitable ranges of frontier orbital energy levels of hole transport matrices useful in various layer of the hole transport region are well-known. In terms of the redox potential of the redox couple HTL matrix/cation radical of the HTL matrix, the preferred values (if measured for example by cyclic voltammetry against ferrocene/ferrocenium redox couple as reference) may be in the range 0.0-1.0 V, more preferably in the range 0.2-0.7 V, even more preferably in the range 0.3-0.5 V.

[0247] The hole transport region of the stack of organic layers may further include a charge-generating material to improve conductivity, in addition to the materials as described above. The charge-generating material may be homogeneously or non-homogeneously dispersed in the hole transport region.

[0248] The charge-generating material may be, for example, a p-dopant. The p-dopant may be one of a quinone derivative, a metal oxide, and a cyano group-containing compound, but is not limited thereto. Non-limiting examples of the p-dopant are quinone derivatives such as tetracyanoquinonedimethane (TCNQ), 2,3,5,6-tetrafluoro-tetracyano-1,4-benzoquinonedimethane (F4-TCNQ), and the like; metal oxides such as tungsten oxide, molybdenum oxide, and the like; and cyano-containing compounds such as compound HT-D1 below.

##STR00013##

[0249] The hole transport part of the charge transport region may further include a buffer layer.

[0250] The buffer layer may compensate for an optical resonance distance of light according to a wavelength of the light emitted from the EML, and thus may increase efficiency.

[0251] The emission layer (EML) may be formed on the hole transport region by using vacuum deposition, spin coating, casting, LB method, or the like. When the emission layer is formed using vacuum deposition or spin coating, the conditions for deposition and coating may be similar to those for the formation of the hole injection layer, though the conditions for the deposition and coating may vary depending on the material that is used to form the emission layer. The emission layer may include an emitter host (EML host) and an emitter dopant (further only emitter).

[0252] The emitter may be a red, green, or blue emitter.

[0253] In one embodiment, the emitter host is an anthracene matrix compound represented by formula 400 below:

##STR00014##

[0254] In formula 400, Ar.sub.111 and Ar.sub.112 may be each independently a substituted or unsubstituted C.sub.6-C.sub.60 arylene group; Ar.sub.113 to Ar.sub.116 may be each independently a substituted or unsubstituted C.sub.1-C.sub.10 alkyl group or a substituted or unsubstituted C.sub.6-C.sub.60 aryl group; and g, h, i, and j may be each independently an integer from 0 to 4. In some embodiments, Ar.sub.111 and Ar.sub.112 in formula 400 may be each independently one of a phenylene group, a naphthylene group, a phenanthrenylene group, or a pyrenylene group; or a phenylene group, a naphthylene group, a phenanthrenylene group, a fluorenyl group, or a pyrenylene group, each substituted with at least one of a phenyl group, a naphthyl group, or an anthryl group.

[0255] In formula 400, g, h, i, and j may be each independently an integer of 0, 1, or 2.

[0256] In formula 400, Ar.sub.113 to Ar.sub.116 may be each independently one of [0257] a C.sub.1-C.sub.10 alkyl group substituted with at least one of a phenyl group, a naphthyl group, or an anthryl group; [0258] a phenyl group, a naphthyl group, an anthryl group, a pyrenyl group, a phenanthrenyl group, or a fluorenyl group; [0259] a phenyl group, a naphthyl group, an anthryl group, a pyrenyl group, a phenanthrenyl group, or [0260] a fluorenyl group, each substituted with at least one of a deuterium atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxyl group or a salt thereof, [0261] a sulfonic acid group or a salt thereof, [0262] a phosphoric acid group or a salt thereof, [0263] a C.sub.1-C.sub.60 alkyl group, a C.sub.2-C.sub.60 alkenyl group, a C.sub.2-C.sub.60 alkynyl group, a C.sub.1-C.sub.60 alkoxy group, a phenyl group, a naphthyl group, an anthryl group, a pyrenyl group, a phenanthrenyl group, or [0264] a fluorenyl group; or

##STR00015##

or formulas (Y2) or (Y3):

##STR00016##

[0265] Wherein in the formulas (Y2) and (Y3), X is selected form an oxygen atom and a sulfur atom, but embodiments of the invention are not limited thereto.

[0266] In the formula (Y2), any one of R.sub.11 to R.sub.14 is used for bonding to Ar.sub.111. R.sub.11 to R.sub.14 that are not used for bonding to Ar.sub.111 and R.sub.15 to R.sub.20 are the same as R.sub.1 to R.sub.8.

[0267] In the formula (Y3), any one of R.sub.21 to R.sub.24 is used for bonding to Ar.sub.111. R.sub.21 to R.sub.24 that are not used for bonding to Ar.sub.111 and R.sub.25 to R.sub.30 are the same as R.sub.1 to R.sub.8.

[0268] Preferably, the EML host comprises between one and three heteroatoms selected from the group consisting of N, O or S. More preferred the EML host comprises one heteroatom selected from S or O.

[0269] According to a further aspect of the invention, the emitter host respectively has a reduction potential which, if measured under the same conditions by cyclic voltammetry against Fc/Fc.sup.+ in tetrahydrofuran, has a value more negative than the respective value obtained for 7-([1,1-biphenyl]-4-yl)dibenzo[c,h]acridine, preferably more negative than the respective value for 9,9,10,10-tetraphenyl-2,2-bianthracene, more preferably more negative than the respective value for 2,9-di([1,1-biphenyl]-4-yl)-4,7-diphenyl-1,10-phenanthroline, even more preferably more negative than the respective value for 2,4,7,9-tetraphenyl-1,10-phenanthroline, even more preferably more negative than the respective value for 9,10-di(naphthalen-2-yl)-2-phenylanthracene, even more preferably more negative than the respective value for 2,9-bis(2-methoxyphenyl)-4,7-diphenyl-1,10-phenanthroline, most preferably more negative than the respective value for 9,9-spirobi[fluorene]-2,7-diylbis(diphenylphosphine oxide).

[0270] The emitter is mixed in a small amount to cause light emission, and may be generally a material such as a metal complex that emits light by multiple excitation into a triplet or more. The emitter may be, for example an inorganic, organic, or organometallic compound, and one or more kinds thereof may be used.

[0271] The emitter may be a fluorescent emitter, for example ter-fluorene, the structures are shown below. 4,4-bis(4-diphenyl amiostyryl)biphenyl (DPAVBi), 2,5,8,11-tetra-tert-butyl perylene (TBPe), and Compound 4 below are examples of fluorescent blue emitters.

##STR00017##

[0272] According to another aspect, the organic semiconductor layer comprising a compound of formula I is arranged between a fluorescent blue emission layer and the cathode electrode.

[0273] The emitter may be a phosphorescent emitter, and examples of the phosphorescent emitters may be organometallic compounds including Jr, Pt, Os, Ti, Zr, Hf, Eu, Tb, Tm, Fe, Co, Ni, Ru, Rh, Pd, or a combination thereof. The phosphorescent emitter may be, for example a compound represented by formula Z, but is not limited thereto:

L.sub.2MX (Z).

[0274] In formula Z, M is a metal, and L and X are the same or different, and are a ligand to form a complex compound with M.

[0275] The M may be, for example Ir, Pt, Os, Ti, Zr, Hf, Eu, Tb, Tm, Fe, Co, Ni, Ru, Rh, Pd or, in a polynuclear complex, a combination thereof, and the L and X may be, for example, a bidendate ligand.

[0276] A thickness of the emission layer may be about 10 nm to about 100 nm, for example about 20 nm to about 60 nm. When the thickness of the emission layer is within these ranges, the emission layer may have improved emission characteristics without a substantial increase in a driving voltage.

[0277] Next, the electron transport region of the stack of organic layers 105 is disposed on the emission layer.

[0278] The electron transport region of the stack of organic layers includes at least the first electron transport layer. The electron transport region of the stack of organic layers may further include an electron injection layer and/or the second electron transport layer. At least the first electron transport layer comprises the n-doped semiconducting material according to one of its various embodiments.

[0279] For example, the electron transport region of the stack of organic layers may have a structure of the first electron transport layer/second electron transport layer/electron injection layer but is not limited thereto. For example, an organic light emitting diode according to an embodiment of the present invention includes at least two electron transport layers in the electron transport region of the stack of organic layers 105, and in this case, the electron transport layer contacting the emission layer is defined as the second electron transport layer 33.

[0280] The electron transport layer may include two or more different electron transport matrix compounds.

Second Electron Transport Matrix Compound

[0281] Various embodiments of the electron transport region in the device according to invention, e.g. devices comprising hole blocking layers, electron injecting layers, may comprise a second electron transport matrix compound.

[0282] Second electron transport matrix compound is not particularly limited. Similarly as other materials which are in the inventive device comprised outside the emitting layer, the second electron transport matrix compound may not emit light.

[0283] According to one embodiment, the second electron transport matrix can be an organic compound, an organometallic compound, or a metal complex.

[0284] According to one embodiment, the second electron transport matrix may be a covalent compound comprising a conjugated system of at least 6 delocalized electrons. Under a covalent material in a broadest possible sense, it might be understood a material, wherein at least 50% of all chemical bonds are covalent bonds, wherein coordination bonds are also considered as covalent bonds. In the present application, the term encompasses in the broadest sense all usual electron transport matrices which are predominantly selected from organic compounds but also e.g. from compounds comprising structural moieties which do not comprise carbon, for example substituted 2,4,6-tribora-1,3,5 triazines, or from metal complexes, for example aluminium tris(8-hydroxyquinolinolate).

[0285] The molecular covalent materials can comprise low molecular weight compounds which may be, preferably, stable enough to be processable by vacuum thermal evaporation (VTE). Alternatively, covalent materials can comprise polymeric covalent compounds, preferably, compounds soluble in a solvent and thus processable in form of a solution. It is to be understood that a polymeric substantially covalent material may be crosslinked to form an infinite irregular network, however, it is supposed that such crosslinked polymeric substantially covalent matrix compound still comprises both skeletal as well as peripheral atoms. Skeletal atoms of the covalent compound are covalently bound to at least two neighbour atoms. Other atoms of the covalent compound are peripheral atoms which are covalently bound with a single neighbour atom. Inorganic infinite crystals or fully crosslinked networks having partly covalent bonding but substantially lacking peripheral atoms, like silicon, germanium, gallium arsenide, indium phosphide, zinc sulfide, silicate glass etc. are not considered as covalent matrices in the sense of present application, because such fully crosslinked covalent materials comprise peripheral atoms only on the surface of the phase formed by such material. A compound comprising cations and anions is still considered as covalent, if at least the cation or at least the anion comprises at least ten covalently bound atoms.

[0286] Preferred examples of covalent second electron transport matrix compounds are organic compounds, consisting predominantly from covalently bound C, H, O, N, S, which may optionally comprise also covalently bound B, P, As, Se. In one embodiment, the second electron transport matrix compound lacks metal atoms and majority of its skeletal atoms is selected from C, O, S, N.

[0287] In another embodiment, the second electron transport matrix compound comprises a conjugated system of at least six, more preferably at least ten, even more preferably at least fourteen delocalized electrons.

[0288] Examples of conjugated systems of delocalized electrons are systems of alternating pi- and sigma bonds. Optionally, one or more two-atom structural units having the pi-bond between its atoms can be replaced by an atom bearing at least one lone electron pair, typically by a divalent atom selected from O, S, Se, Te or by a trivalent atom selected from N, P, As, Sb, Bi. Preferably, the conjugated system of delocalized electrons comprises at least one aromatic or heteroaromatic ring adhering to the Hckel rule. Also preferably, the second electron transport matrix compound may comprise at least two aromatic or heteroaromatic rings which are either linked by a covalent bond or condensed.

[0289] In one of specific embodiments, the second electron transport matrix compound comprises a ring consisting of covalently bound atoms and at least one atom in the ring is phosphorus.

[0290] In a more preferred embodiment, the phosphorus-containing ring consisting of covalently bound atoms is a phosphepine ring.

[0291] In another preferred embodiment, the covalent matrix compound comprises a phosphine oxide group. Also preferably, the substantially covalent matrix compound comprises a heterocyclic ring comprising at least one nitrogen atom. Examples of nitrogen containing heterocyclic compounds which are particularly advantageous as second electron transport matrix compound for the inventive device are matrices comprising, alone or in combination, pyridine structural moieties, diazine structural moieties, triazine structural moieties, quinoline structural moieties, benzoquinoline structural moieties, quinazoline structural moieties, acridine structural moieties, benzacridine structural moieties, dibenzacridine structural moieties, diazole structural moieties and benzodiazole structural moieties.

[0292] The second matrix compound may have a molecular weight (Mw) of 400 to 850 g/mol, preferably 450 to 830 g/mol. If the molecular weight is selected in this range, particularly reproducible evaporation and deposition can be achieved in vacuum at temperatures where good long-term stability is observed.

[0293] Preferably, the second matrix compound may be essentially non-emissive.

[0294] According to another aspect, the reduction potential of the second electron transport compound may be selected more negative than 2.2 V and less negative than 2.35 V against Fc/Fc.sup.+ in tetrahydrofuran, preferably more negative than 2.25 V and less negative than 2.3 V.

[0295] According to one embodiment, the first and the second matrix compound may be selected different, and [0296] the second electron transport layer consist of a second matrix compound; and [0297] the first electron transport layer consist of the first matrix compound of formula (I), and an electrical n-dopant, preferably an alkali metal salt or an alkali metal organic complex.

[0298] Preferably, the first and second electron transport layer may be essentially non-emissive.

[0299] According to another embodiment, the second electron transport layer can be in direct contact with the emission layer.

[0300] According to another embodiment, the first electron transport layer can be in direct contact with the second electron transport layer.

[0301] According to another embodiment, the second electron transport layer can be contacting sandwiched between the emission layer and the first electron transport layer.

[0302] According to another embodiment, the first electron transport layer can be in direct contact with the electron injection layer.

[0303] According to another embodiment, the first electron transport layer can be contacting sandwiched between the second electron transport layer and the electron injection layer.

[0304] According to another embodiment, the first electron transport layer can be in direct contact with the cathode electrode.

[0305] According to another embodiment, the first electron transport layer can be contacting sandwiched between the second electron transport layer and the cathode layer.

[0306] According to another embodiment, the second electron transport layer can be contacting sandwiched between the emission layer and the first electron transport layer, and the first electron transport layer can be contacting sandwiched between the second electron transport layer and the electron injection layer.

[0307] The formation conditions of the first electron transport layer 31, second electron transport layer 33, and electron injection layer 37 of the electron transport region of the stack of organic layers refer to the formation conditions of the hole injection layer.

[0308] The thickness of the first electron transport layer may be from about 2 nm to about 100 nm, for example about 3 nm to about 30 nm. When the thickness of the first electron transport layer is within these ranges, the first electron transport layer may have improved electron transport auxiliary ability without a substantial increase in driving voltage.

[0309] A thickness of the second electron transport layer may be about 10 nm to about 100 nm, for example about 15 nm to about 50 nm. When the thickness of the electron transport layer is within these ranges, the electron transport layer may have satisfactory electron transporting ability without a substantial increase in driving voltage.

[0310] According to another aspect of the invention, the organic electroluminescent device further comprises an electron injection layer between the second electron transport layer and the cathode.

[0311] The electron injection layer (EIL) 37 may facilitate injection of electrons from the cathode 150.

[0312] According to another aspect of the invention, the electron injection layer 37 comprises: [0313] (i) an electropositive metal selected from alkali metals, alkaline earth metals and rare earth metals in substantially elemental form, preferably selected from Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Eu and Yb, more preferably from Li, Na, Mg, Ca, Sr and Yb, even more preferably from Li and Yb, most preferably Yb; and/or [0314] (ii) an alkali metal complex and/or alkali metal salt, preferably the Li complex and/or salt, more preferably a Li quinolinolate, even more preferably a lithium 8-hydroxyquinolinolate, most preferably the alkali metal salt and/or complex of the second electron transport layer is idencial with the alkali metal salt and/or complex of the injection layer.

[0315] The electron injection layer may include at least one selected from LiF, NaCl, CsF, Li.sub.2O, and BaO.

[0316] A thickness of the EIL may be from about 0.1 nm to about 10 nm, or about 0.3 nm to about 9 nm. When the thickness of the electron injection layer is within these ranges, the electron injection layer may have satisfactory electron injection ability without a substantial increase in driving voltage.

[0317] A material for the cathode 150 may be a metal, an alloy, or an electrically conductive compound that have a low work function, or a combination thereof. Specific examples of the material for the cathode 150 may be lithium (Li), magnesium (Mg), aluminum (Al), aluminum-lithium (AlLi), calcium (Ca), magnesium-indium (MgIn), magnesium-silver (MgAg), etc. In order to manufacture a top-emission light-emitting device having a reflective anode 110 deposited on a substrate, the cathode 150 may be formed as a transmissive electrode from, for example, indium tin oxide (ITO) or indium zinc oxide (IZO).

[0318] Hereinafter, the embodiments are illustrated in more detail with reference to examples. However, the present disclosure is not limited to the following examples.

DETAILED DESCRIPTION

[0319] Synthesis and Physical Properties of Compound of Formula I

[0320] Triazine compounds of formula I may be synthesized in accordance with the methods described in PCT-KR2015-012551.

SYNTHESIS EXAMPLE 1

Compound A6 (in the Scheme Referred as Compound [3])

[0321] ##STR00018##

[0322] First Step: Synthesis of Intermediate I-5

[0323] 13 g of an intermediate I-5 (61%) was obtained in the same synthesis method as the synthesis method of the compound 1 by using the intermediate I-4 (20.4 g, 34.92 mmol) and 1-bromo-3-iodobenzene (16.5 g, 52.39 mmol) under a nitrogen environment.

[0324] Second Step: Synthesis of Intermediate 1-6

[0325] 10 g of an intermediate I-6 (74%) was obtained in the same synthesis method as the synthesis method of the intermediate I-4 by using the intermediate I-5 (12.6 g, 20.54 mmol) under a nitrogen environment.

[0326] Third Step: Synthesis of Compound A6

[0327] 8.7 g of compound A6 (in the scheme referred as [3]) was obtained in 68% yield by using the intermediate 1-6 (10 g, 15.2 mmol) and 2-(3-bromophenyl)-4,6-diphenyl-1,3,5-triazine (7.9 g, 18.32 mmol). These reagents were dissolved in 250 mL tetrahydrofuran under a nitrogen environment, tetrakis(triphenylphosphine)palladium (0.9 g, 0.75 mmol) was added thereto, and the mixture was stirred. Then, potassium carbonate saturated in water (5.2 g, 37 mmol) was added thereto, and the mixture was heated and refluxed at 80 C. for 24 hours. When the reaction was complete, water was added to the reaction solution, dichloromethane was used to perform an extraction, an anhydrous MgSO.sub.4 was used to remove moisture therefrom, and a resultant therefrom was filtered and concentrated under a reduced pressure. This obtained residue was separated and purified through column chromatography.

[0328] LC Mass (theoretical value: 842.04 g/mol, measured value: M+H.sup.+=843.03 g/mol)

[0329] The benzoquinazoline compound A9 was prepared analogously. Physical properties of tested compounds of formula (I) are summarized in Table 1.

[0330] Dibenzoacridine compounds of formula I may be synthesized in accordance with the methods described in WO2011/154131A1.

[0331] Another alternative is demonstrated in Synthesis example 2. The procedure is generally applicable for the synthesis of compounds comprising the hexaphenylbenzene structural moiety.

SYNTHESIS EXAMPLE 2

Compound A16

Step 1: Synthesis of 7-(4-(phenylethynyl)phenyl)dibenzo[c,h]acridine

[0332] ##STR00019##

[0333] A three necked 250-mL round bottom flask is purged with N.sub.2. Under a constant flow of N.sub.2 7-(4-bromophenyl)dibenzo[c,h]acridine (10.0 g, 23.0 mmol), phenylacetylene (4.70 g, 46.0 mmol, 2.0 eq.), and bis (triphenylphosphine)-palladium chloride (3.23 g, 4.6 mmol, 0.2 eq.) were introduced, followed by a 1M-solution of tetrabutylammonium fluoride in THF (70 mL). The resulting mixture was warmed up to reflux and reacted for 2 h. After completion of the reaction, MeOH (70 mL) was added, and the solution was left to cool down to room temperature. The precipitate formed upon cooling was collected by filtration, washed with MeOH (250 mL), then hexane (350 mL), and finally dried under vacuum at 40 C.

[0334] Yield: about 7.0 g (about 67%, yellowish solid).

Step 2: Synthesis of 7-(3,4,5,6-tetraphenyl-[1,1:2,1-terphenyl]-4-yl)dibenzo[c,h]acridine

[0335] ##STR00020##

[0336] A three necked 100-mL round bottom flask was charged with 7-(4-(phenylethynyl)phenyl)dibenzo[c,h]acridine (6.8 g, 14.9 mmol), 2,3,4,5-tetraphenylcyclopenta-2,4-dienone (6.31 g, 16.4 mmol, 1.1 eq.), and benzophenone (35 g as molten solvent). After degassing the solids with N.sub.2, the resulting mixture was warmed up to 300 C. After 1 h of reflux at 300 C., gas evolution had stopped and the mixture was hence cooled down to ca. 80 C. Toluene (100 mL), was added, and the resulting precipitate was filtered off and washed with toluene (240 mL), followed by hexane (240 mL). The solid was then purified by trituration in hot chlorobenzene (60 mL), followed by trituration in hot MeOH (60 mL). After filtration and drying under vacuum at 120 C., the desired was isolated as a yellowish powder.

[0337] Yield: about 6.8 g (about 56%, yellowish solid).

[0338] The benzoacridine compound A18 was prepared analogously. In Table 1 are summarized dibenzoacridine compounds of formula I and their starting material, yield, m/z, glass transition temperature, reduction potential against Fc/Fc.sup.+ in tetrahydrofuran.

TABLE-US-00001 TABLE 1 Redox poten- tial against Yield Tg Fc/Fc.sup.+ Comp. I: Starting materials Structure of compound I [%] [ C.] [V] A1 [00021] [00022] 62% 175 2.25 A2 [00023] 138 2.20 A3 [00024] 135 2.20 A4 [00025] 140 2.22 A5 [00026] [00027] 86% 165 2.29 A6 [00028] 139 2.18 A7 [00029] 147 2.15 A8 [00030] 147 2.18 A9 [00031] 144 2.25 A10 [00032] 149 2.14 A12 [00033] 2.18 A13 [00034] 2.23 A15 [00035] [00036] 58% 159 2.29 A16 [00037] Not ob- served 2.31 A17 [00038] [00039] 50% 175 A18 [00040] Not ob- served 2.25

General Procedure for Fabrication of OLEDs

[0339] The model top emitting blue fluorescent OLED is described below.

[0340] It was prepared using auxiliary materials F1, F2, F3, F4, F5, F6 and PD-2:

##STR00041##

[0341] biphenyl-4-yl(9,9-dimethyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine, CAS 1242056-42-3, F1;

##STR00042##

[0342] N,N-bis(4-(dibenzo[b,d]furan-4-yl)phenyl)-[1,1:4,1-terphenyl]-4-amine, CAS 1198399-61-9, F2;

##STR00043##

[0343] 2-(10-phenyl-9-anthracenyl)-benzo[b]naphtho[2,3-d]furan, CAS 1627916-48-6, F3;

##STR00044##

7-(3-(pyridine-2-yl)phenyl)dibenzo[c,h]acridine, F4

##STR00045##

7-(3-(pyren-1-yl)phenyl)dibenzo[c,h]acridine, F5

##STR00046##

2-([1,1-biphenyl]-4-yl)-4-(9,9-diphenyl-9H-fluoren-4-yl)-6-phenyl-1,3,5-triazine, CAS 1801992-44-8, F6

##STR00047##

[0344] 2,2,2-(cyclopropane-1,2,3-triylidene)tris(2-(p-cyanotetrafluorophenyl)acetonitrile), CAS 1224447-88-4, PD-2.

DEVICE EXAMPLE 1

Top Emitting Blue OLED

[0345] A glass substrate was cut to a size of 50 mm50 mm0.7 mm, ultrasonically cleaned with isopropyl alcohol for 5 minutes and then with pure water for 5 minutes, and cleaned again with UV ozone for 30 minutes, to prepare a first electrode. 100 nm Ag were deposited as anode at a pressure of 10.sup.5 to 10.sup.7 mbar.

[0346] Then, 92 wt.-% F1 with 8 wt.-% PD2 were vacuum deposited on the ITO electrode, to form a HIL having a thickness of 10 nm. Then, undoped F1 was vacuum deposited on the HIL, to form a HTL having a thickness of 122 nm.

[0347] Then, F2 was vacuum deposited on the HTL, to form an electron blocking layer (EBL) having a thickness of 5 nm.

[0348] Then, 97 wt.-% F3 as EML host and 3 wt.-% blue dopant NUBD370 (Sun Fine Chemicals) were deposited on the EBL, to form a blue-emitting EML with a thickness of 20 nm.

[0349] Then the second electron transport layer 33, if present, is formed with a thickness of 5 nm by depositing compound A6, and the first electron transport layer 31 is formed either directly on the emission layer or on the second electron transport layer according. If the first electron transport layer is in direct contact with the emission layer, the thickness is 36 nm. If the first electron transport layer is deposited on top of the second electron transport layer, the thickness is 31 nm.

[0350] The first electron transport layer comprises 50 wt.-% matrix compound and 50 wt.-% of LiQ. The composition is shown in Table 2.

[0351] Then the electron injection layer 37 is formed on the electron transport layer 31 by depositing LiQ with a thickness of 1.5 nm or Yb with a thickness of 2 nm.

[0352] The cathode was evaporated at ultra-high vacuum of 10.sup.7 mbar. Therefore, a thermal single co-evaporation of one or several metals was performed with a rate of 0, 1 to 10 nm/s (0.01 to 1 /s) in order to generate a homogeneous cathode with a thickness of 5 to 1000 nm. The cathode was formed from 13 nm magnesium silver alloy (90:10 vol.-%) or from 11 nm Ag.

[0353] A cap layer of F1 was formed on the cathode with a thickness of 60 nm in case of MgAg cathode and 75 nm in case of Ag cathode.

[0354] Evaluation of Device Experiments

[0355] To assess the performance of the inventive examples compared to the prior art, the current efficiency is measured under ambient conditions (20 C.). Operational voltage measurements are performed using a Keithley 2400 sourcemeter, and reported in V at standard current density 10 mA/cm.sup.2 for top emission devices. For bottom emission devices, the standard current density is usually 15 mA/cm.sup.2. A calibrated spectrometer CAS140 from Instrument Systems is used for measurement of CIE coordinates and brightness in Candela. Lifetime LT of the device is measured at ambient conditions (20 C.) and standard current density 10 mA/cm.sup.2 or 15 mA/cm.sup.2, using a Keithley 2400 sourcemeter, and recorded in hours. The brightness of the device is measured using a calibrated photo diode. The lifetime LT is defined as the time till the brightness of the device is reduced to 97% of its initial value.

[0356] The light output in external efficiency EQE and power efficiency P.sub.eff (lm/W) are determined at 10 mA/cm.sup.2 for top emission devices.

[0357] To determine the efficiency EQE in % the light output of the device is measured using a calibrated photodiode.

[0358] To determine the power efficiency in lm/W, in a first step the luminance in candela per square meter (cd/m.sup.2) is measured with an array spectrometer CAS140 CT from Instrument Systems which has been calibrated by Deutsche Akkreditierungsstelle (DAkkS). In a second step, the luminance is then multiplied by and divided by the voltage and current density.

[0359] In bottom emission devices, the emission is predominately Lambertian and quantified in percent external quantum efficiency (EQE) and power efficiency in lm/W. [0360] The auxiliary compounds F4-F6 served as state-of-art references; the results in terms of operational voltage U, and current efficiency Ceff are shown in Table 2.

TABLE-US-00002 TABLE 2 Performance at 10 mA/cm.sup.2 of top emission devices comprising a second ETL (33), a first ETL (34) and a lithium organic complex, and an EIL (37) second ETL first ETL EIL Cathode U (V) C.sub.eff (cd/A) Comparative F4:LiQ LiQ Mg:Ag 3.39 7.2 device 1 Device 1 A15:LiQ Yb Ag 3.71 9.2 Device 2 A5:LiQ Yb Ag 3.56 9.2 Comparative A6 F5:LiQ LiQ Mg:Ag 3.41 6.5 device 2 Device 3 A6 A16:LiQ Yb Ag 3.77 9.2 Device 4 A6 A15:LiQ Yb Ag 3.78 9.1 Comparative F5 F6:LiQ LiQ Mg:Ag 3.34 6.8 device 3
Technical Effect of the invention

[0361] As it may be taken from the Table 2, tested compounds of formula (I) implemented in a state-of-art semiconducting material doped with LiQ showed better results (highlighted in boldface letters) in terms of improved current efficiency than the state-of-art matrix compounds F4, F5 and F6 used as reference.

[0362] While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Therefore, the aforementioned embodiments should be understood to be exemplary but not limiting the present invention in any way.