Electroluminescent device comprising a defined layer arrangement comprising a light-emitting layer, a hole-transporting layer and an electron-transporting layer

Abstract

The present invention relates to an electroluminescent device comprising a defined layer arrangement comprising a light-emitting layer, a hole-transporting layer and an electron-transporting layer. In particular, the present invention relates to an electroluminescent device comprising: - at least one anode layer, - at least one cathode layer, - at least one light-emitting layer, - at least one first hole-transporting layer, - at least one first electron-transporting layer; wherein for improving the power efficiency the composition of the light-emitting layer, the hole-transporting layer and the electron-transporting layer are matched to each other, wherein - the at least one light-emitting layer comprises: - at least one fluorescent emitter compound embedded in at least one polar emitter host compound, wherein - the at least one polar emitter host compound has at least three aromatic rings independently selected from carbocyclic and heterocyclic rings; - the first electron-transporting layer comprises: - at least one redox n-type dopant, and - at least one first electron-transporting matrix compound.

Description

[0001] This application is a divisional application of the Chinese patent application No. 201880009172.1, filed on January 30, 2018, with the title “Electroluminescent device comprising a confinement layer arrangement comprising a light-emitting layer, a hole-transporting layer and an electron-transporting layer”. TECHNICAL FIELD

[0002] The present invention relates to an electroluminescent device comprising a confinement layer arrangement comprising a light-emitting layer, a hole-transporting layer and an electron-transporting layer. In particular, the present invention relates to an electroluminescent device, in particular to an organic light-emitting diode (OLED), comprising a confinement layer arrangement comprising a light-emitting layer, a hole-transporting layer and an electron-transporting layer, wherein the composition of the layers matches each other completely, and to a display device of an electroluminescent device. BACKGROUND

[0003] Organic light-emitting diodes (OLEDs), which are self-luminescent devices, have a wide viewing angle, excellent contrast, fast response, high brightness, excellent driving voltage characteristics and color reproduction. A typical OLED comprises an anode, a hole-transporting layer (HTL), a light-emitting layer (EML), an electron-transporting layer (ETL) and a cathode, which are sequentially stacked on a substrate. In this regard, the HTL, the EML and the ETL are thin films formed of organic compounds.

[0004] When a voltage is applied to the anode and the cathode, holes injected from the anode move to the EML via the HTL, and electrons injected from the cathode move to the EML via the ETL. The holes and the electrons recombine in the EML to generate excitons. Light is emitted when the excitons drop from the excited state to the ground state. In a fluorescent OLED, the EML contains a fluorescent emitter capable of radiative transition from a short-lived singlet excited state. The fluorescent emitter is mainly used in an OLED that emits blue or blue-green light.

[0005] There is a continuing need for the development of improved OLED materials, which aim to work at as low a voltage as possible while having a high brightness / luminance, and the injection and flow of holes and electrons are balanced, so that an OLED having the above structure has excellent efficiency and / or long lifetime.

[0006] Furthermore, a large number of various host compounds for fluorescent emitters in the light-emitting layer of an OLED and a large number of various electron-transporting matrices for the electron-transporting layer are known in the art. However, the question whether the polarity of the emitter host and, in addition, the matching between the polarity of the emitter host and the polarity of the electron-transporting matrix in the electron-transporting layer adjacent to the light-emitting layer can be of importance for the device efficiency has not been specifically addressed.

[0007] To further improve the performance of electroluminescent devices, especially the power efficiency, the present invention implements the use of a defined layer arrangement comprising a light-emitting layer, a hole-transporting layer and an electron-transporting layer, wherein the compositions of the layers are fully matched to each other. SUMMARY

[0008] Aspects of the present invention provide an electroluminescent device comprising a defined layer arrangement comprising a light-emitting layer, a hole-transporting layer and an electron-transporting layer, wherein the compositions of the light-emitting layer, the hole-transporting layer and the electron-transporting layer are fully matched to each other to improve efficiency, in particular power efficiency, and advantageously also external quantum efficiency EQE, low operating voltage and long lifetime, in particular in top- and / or bottom-emitting organic light-emitting diodes (OLEDs).

[0009] One aspect of the present invention provides an electroluminescent device comprising:

[0010] - at least one anode layer,

[0011] - at least one cathode layer,

[0012] - at least one light-emitting layer,

[0013] - at least one first hole-transporting layer,

[0014] - at least one first electron-transporting layer;

[0015] wherein for improving the power efficiency the compositions of the light-emitting layer, the hole-transporting layer and the electron-transporting layer are matched to each other, wherein

[0016] - the at least one light-emitting layer is arranged between the anode layer and the cathode layer, wherein the at least one light-emitting layer comprises:

[0017] - at least one fluorescent emitter compound embedded in at least one polar emitter host compound, wherein

[0018] - the at least one polar emitter host compound has at least three aromatic rings independently selected from carbocyclic and heterocyclic rings;

[0019] - the at least one first hole-transporting layer is arranged between the anode layer and the light-emitting layer, wherein the at least one first hole-transporting layer comprises:

[0020] - at least one p-type electrical dopant, or

[0021] - at least one p-type electrical dopant and at least one first hole-transporting matrix compound;

[0022] - the at least one first electron-transporting layer is arranged between the cathode layer and the light-emitting layer, wherein the first electron-transporting layer comprises:

[0023] at least one redox n-type dopant, and

[0024] at least one first electron transport matrix compound.

[0025] Another aspect of the present application provides an electroluminescent device comprising:

[0026] at least one anode layer,

[0027] at least one cathode layer,

[0028] at least one light-emitting layer,

[0029] at least one first hole transport layer,

[0030] at least one first electron transport layer;

[0031] wherein for improving the power efficiency the composition of the light-emitting layer, the hole transport layer and the electron transport layer are matched to each other, wherein

[0032] the at least one light-emitting layer is arranged between the anode layer and the cathode layer, wherein the at least one light-emitting layer comprises:

[0033] at least one fluorescent emitter compound embedded in at least one polar emitter host compound, wherein

[0034] the at least one polar emitter host compound has at least three aromatic rings independently selected from the group consisting of carbocyclic and heterocyclic rings and has a gas phase dipole moment in the range of about > 0.2 Debye to about < 2.0 Debye, calculated using the hybrid functional B3LYP with Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5 for the lowest energy conformational isomer found by using the program package TURBOMOLE V6.5 with hybrid functional B3LYP with Gaussian 6-31G* basis set;

[0035] the at least one first hole transport layer is arranged between the anode layer and the light-emitting layer, wherein the at least one first hole transport layer comprises:

[0036] at least one p-type electrical dopant, or

[0037] at least one p-type electrical dopant and at least one first hole transport matrix compound;

[0038] the at least one first electron transport layer is arranged between the cathode layer and the light-emitting layer, wherein the first electron transport layer comprises:

[0039] at least one first electron transport matrix compound.

[0040] at least one first electron transport matrix compound.

[0041] Another aspect of the present application provides an electroluminescent device comprising:

[0042] at least one anode layer,

[0043] at least one cathode layer,

[0044] at least one light-emitting layer,

[0045] at least one first hole transport layer,

[0046] at least one first electron transport layer;

[0047] wherein for improving the power efficiency the composition of the light-emitting layer, the hole transport layer and the electron transport layer are matched to each other, wherein

[0048] the light-emitting layer is arranged between the anode layer and the cathode layer, wherein the light-emitting layer comprises at least one fluorescent emitter compound embedded in at least one polar emitter host compound;

[0049] the first hole transport layer is arranged between the anode layer and the light-emitting layer, wherein the first hole transport layer comprises at least one p-type electrical dopant and / or at least one hole transport matrix compound;

[0050] the first electron transport layer is arranged between the cathode layer and the light-emitting layer, wherein the first electron transport layer comprises at least one redox n-type dopant and at least one first electron transport aromatic matrix compound;

[0051] wherein

[0052] the polar emitter host material comprises at least one polar emitter host compound having at least three aromatic rings independently selected from the group consisting of carbocyclic and heterocyclic rings.

[0053] According to one embodiment, the polar emitter host compound can have at least three aromatic rings and is an anthracene compound represented by Formula 1, the aromatic rings being independently selected from the group consisting of carbocyclic and heterocyclic rings:

[0054]

[0055] wherein

[0056] A 1 selected from substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl;

[0057] A 2 selected from substituted or unsubstituted C1to C 10 alkyl groups, substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl;

[0058] A 3 selected from substituted or unsubstituted C1to C 10 alkyl groups, substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl;

[0059] A 4 selected from substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl, preferably C6-C 60 heteroaryl.

[0060] According to one embodiment, the at least one light-emitting layer comprises:

[0061] at least one fluorescent emitter compound embedded in at least one polar emitter host compound, wherein the at least one polar emitter host compound has at least three aromatic rings independently selected from carbocyclic and heterocyclic rings and has a gas phase dipole moment in the range of about > 0.2 Debye to about < 2.0 Debye, the gas phase dipole moment is calculated using the hybrid functional B3LYP with Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5 for the lowest energy conformational isomer found by using the program package TURBOMOLE V6.5 with hybrid functional B3LYP with Gaussian 6-31G* basis set, and the polar emitter host compound is an anthracene compound represented by Chemical Formula 1:

[0062]

[0063] wherein

[0064] A 1 selected from substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl;

[0065] A 2 selected from substituted or unsubstituted C1to C 10 alkyl groups, substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl;

[0066] A 3 selected from substituted or unsubstituted C1to C10 Alkyl groups, substituted or unsubstituted C6-C 60 Aryl or C6-C 60 Mixed aromatics;

[0067] A 4 Selected from substituted or unsubstituted C6-C 60 Aryl or C6-C 60 Heteroaryl, preferably C6-C 60 Mixed aromatic compounds.

[0068] Another aspect of the present invention provides an electroluminescent device comprising:

[0069] -At least one anode layer,

[0070] -At least one cathode layer,

[0071] -At least one light-emitting layer,

[0072] -At least one first hole transport layer,

[0073] -At least one first electron transport layer;

[0074] To improve power efficiency, the compositions of the light-emitting layer, the hole transport layer, and the electron transport layer are matched.

[0075] - The at least one light-emitting layer is disposed between the anode layer and the cathode layer, wherein

[0076] The at least one light-emitting layer comprises:

[0077] - At least one fluorescent light-emitting compound embedded in at least one polar light-emitting host compound, wherein the at least one polar light-emitting host compound has at least three aromatic rings and is an anthracene compound represented by Formula 1, wherein the aromatic rings are independently selected from carbocyclic and heterocyclic compounds:

[0078]

[0079] in

[0080] A 1 Selected from substituted or unsubstituted C6-C 60 Aryl or C6-C 60 Mixed aromatics;

[0081] A 2 Selected from substituted or unsubstituted C1 to C 10 Alkyl groups, substituted or unsubstituted C6-C 60 Aryl or C6-C 60 Mixed aromatics;

[0082] A 3selected from substituted or unsubstituted C1to C 10 alkyl groups, substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl;

[0083] A 4 selected from substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl, preferably C6-C 60 heteroaryl;

[0084] - the at least one first hole transport layer is arranged between the anode layer and the light-emitting layer, wherein

[0085] The at least one first hole transport layer comprises:

[0086] - at least one p-type electrical dopant selected from:

[0087] a) an organic compound comprising at least one, preferably at least two, more preferably at least three, most preferably at least four electron- withdrawing groups selected from:

[0088] (i) a perhalogenated alkyl group, wherein the halogen in the perhalogenated alkyl group is preferably selected from F and CI, more preferably the perhalogenated alkyl group is a perfluoroalkyl group,

[0089] (ii) a carbonyl group,

[0090] (iii) a sulfonyl group,

[0091] (iv) a nitrile group,

[0092] (v) a nitro group;

[0093] b) a metal oxide, a metal salt and a metal complex, wherein the metal in the metal oxide, metal salt and / or metal complex is preferably present in its highest oxidation state; or

[0094] - optionally at least one further first hole transport matrix compound selected from organic conjugated aromatic systems having at least 6 delocalized electrons;

[0095] - the at least one first electron transport layer is arranged between the cathode layer and the light-emitting layer, wherein the first electron transport layer comprises:

[0096] - at least one redox n-type dopant of an elemental metal selected from:

[0097] a) The element is a metal, preferably selected from alkali metals, alkaline earth metals and rare earth metals; more preferably selected from Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Sm, Eu, Yb; more preferably selected from Li, Na, Cs, Mg, Sr, Yb; even more preferably selected from Li, Na, Mg, Yb; most preferably selected from Li and / or Yb;

[0098] b) An organic group, preferably selected from a diazole group. azole group and thiazolyl group;

[0099] c) A transition metal complex, wherein the transition metal is selected from Group 3, Group 4, Group 5, Group 6, Group 7, Group 8, Group 9 or Group 10 of the periodic table and is in an oxidation state (-I), (0), (I) or (II), preferably, the transition metal complex is electrically neutral;

[0100] and

[0101] -At least one aromatic matrix compound having a first electron transport function of formula 2:

[0102]

[0103] in

[0104] X is selected from O, S, and Se;

[0105] R 1 and R 2 Independently selected from C1 to C 12 Alkyl, C6 to C 20 Aryl and C5 to C 20 Mixed aromatics;

[0106] R 3 Selected from formula (2A),

[0107]

[0108] Or formula (2B)

[0109]

[0110] in

[0111] * Mark the corresponding R 4 Or Ar 1 The group used to make the R 4 Or Ar 1 The position where it bonds with the phosphorus atom in formula (I);

[0112] R 4 Selected from C1 to C8 alkyl, C6 to C 20 Aryl and C5 to C20 heteroaryl;

[0113] Ar 1 selected from C6to C 20 aryl and C5to C 20 heteroaryl;

[0114] Ar 2 selected from C 18 to C 40 aryl and C 10 to C 40 heteroaryl;

[0115] R 5 selected from H, C1to C 12 alkyl, C6to C 20 aryl and C5to C 20 heteroaryl;

[0116] n is selected from 0, 1 or 2.

[0117] Surprisingly, it has been found that a defined layer arrangement comprising a light-emitting layer, a hole-transporting layer and an electron-transporting layer, wherein its composition is fully matched to each other, improves the power efficiency of an electroluminescent device.

[0118] It is furthermore surprising that for a defined layer arrangement, the use of at least one fluorescent emitter compound embedded in at least one polar emitter host compound enables better device performance compared to its non-polar alternative.

[0119] Furthermore, it has been found that for a defined layer arrangement of a light-emitting layer, a hole-transporting layer and an electron-transporting layer, an appropriate match between the polarity of the emitter host and the polarity of the electron-transporting layer matrix compound forming the electron-transporting layer adjacent to the light-emitting layer can have an additional improvement effect on the device efficiency, which can be achieved by using a redox n-type dopant in at least one electron-transporting layer matrix compound in an electroluminescent device, for example in prior art devices with high brightness.

[0120] Particular aspects of the device are described in detail below.

[0121] The working conditions of an electroluminescent device, for example an OLED, are described in the experimental section of the present specification.

[0122] According to another aspect of the present application, the electroluminescent device can be an organic light-emitting diode, OLED. In one embodiment, the OLED comprising a defined layer arrangement can be a tandem OLED, for example a white tandem OLED.

[0123] Like other compounds contained in the device of the present invention outside the light-emitting layer, the first electron transport matrix compound can not emit visible light under the operating conditions of an electroluminescent device, such as an OLED.

[0124] An elemental metal is to be understood as a metal in its pure metallic state, in the state of a metal alloy, or in the state of free atoms or metal clusters. It is to be understood that the metal deposited by vacuum thermal evaporation from a metallic phase, such as from a pure bulk metal, is vaporized in its elemental form. It is also to be understood that, if the vaporized elemental metal is deposited together with a covalent matrix, the metal atoms and / or clusters are embedded in the covalent matrix. In other words, it is to be understood that any metal-doped covalent material prepared by vacuum thermal evaporation contains at least some of the metal in its elemental form.

[0125] For use in consumer electronics, only metals containing stable nuclides or nuclides with very long radioactive decay half-lives can be used. As an acceptable level of nuclear stability, the nuclear stability of natural potassium can be employed.

[0126] In the present specification, when not otherwise provided, "substituted" means substituted with C1to C 10 alkyl substituents.

[0127] In the present specification, when not otherwise provided, "alkyl group" means a saturated aliphatic hydrocarbon group. The alkyl group can be a C1to C 10 alkyl group. More specifically, the alkyl group can be a C1to C 10 alkyl group or a C1to C6alkyl group. For example, a C1to C4alkyl group includes 1 to 4 carbons in the alkyl chain and can be selected from the group consisting of methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and t-butyl.

[0128] Specific examples of the alkyl group can be a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, a hexyl group.

[0129] In the present specification, "aryl group" means a hydrocarbon group that can be produced by formally abstracting one hydrogen atom from an aromatic ring in a corresponding aromatic hydrocarbon. An aromatic hydrocarbon refers to a hydrocarbon containing at least one aromatic ring or aromatic ring system. An aromatic ring or aromatic ring system refers to a planar ring or ring system of covalently bonded carbon atoms, wherein the planar ring or ring system comprises a conjugated system of delocalized electrons obeying Hückel's rule. Examples of aryl groups include monocyclic groups such as phenyl or tolyl, polycyclic groups comprising more aromatic rings connected by single bonds, such as biphenyl, and polycyclic groups comprising fused rings, such as naphthyl or fluorene-2-yl.

[0130] Similarly, heteroaryl is to be understood as a radical obtained by formally abstracting one ring hydrogen from a heteroaromatic ring comprising at least one heteroaromatic ring.

[0131] Heterocycloalkyl is to be understood as a radical obtained by formally abstracting one ring hydrogen from a saturated heterocyclic ring comprising at least one saturated heterocyclic ring.

[0132] The term "hetero" is to be understood as a way in which at least one carbon atom of a structure that can be formed from covalently bound carbon atoms is replaced by another polyvalent atom. Preferably, the heteroatom is selected from B, Si, N, P, O, S; more preferably from N, P, O, S.

[0133] In the present description, a single bond means a direct bond.

[0134] In the context of the present invention, "different" means that the compounds do not have the same chemical structure.

[0135] The terms "free of", "free from", "not containing" do not exclude impurities that can be present in the compounds before deposition. The impurities have no technical influence on the purpose achieved by the present invention.

[0136] The term "adjacent" means an arrangement of two layers in which the layers are in direct contact.

[0137] In the context of the present description, the term "essentially not emitting light" means that the contribution of the compound or layer to the visible emission spectrum from the device is less than 10%, preferably less than 5% relative to the visible emission spectrum. The visible emission spectrum is the emission spectrum with wavelengths of about > 380 nm to about < 780 nm.

[0138] In the present description, hole properties mean the ability to provide an electron to form a hole when an electric field is applied, and the hole formed in the anode can easily inject and transport in the light-emitting layer due to the conduction properties according to the highest occupied molecular orbital (HOMO) level.

[0139] In addition, electron properties mean the ability to accept an electron when an electric field is applied, and the electron formed in the cathode can easily inject and transport in the light-emitting layer due to the conduction properties according to the lowest unoccupied molecular orbital (LUMO) level.

[0140] Another aspect of the present invention provides an electroluminescent device comprising:

[0141] - at least one anode layer,

[0142] - at least one cathode layer,

[0143] - at least one light-emitting layer,

[0144] - at least one first hole transport layer,

[0145] - at least one first electron transport layer;

[0146] wherein for improving power efficiency the composition of the light emitting layer, the hole transport layer and the electron transport layer match each other, wherein

[0147] - the at least one light emitting layer is arranged between the anode layer and the cathode layer, wherein the at least one light emitting layer comprises:

[0148] - at least one fluorescent emitter compound embedded in at least one polar emitter host compound, wherein

[0149] - the at least one polar emitter host compound has at least three aromatic rings and preferably it can have a gas phase dipole moment in the range of about > 0.2 Debye to about < 2.0 Debye, the aromatic rings are independently selected from the group consisting of carbocyclic and heterocyclic rings, the gas phase dipole moment is calculated using the hybrid functional B3LYP with Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5 for the lowest energy conformational isomer found by using the program package TURBOMOLE V6.5 with hybrid functional B3LYP with Gaussian 6-31G* basis set;

[0150] - the at least one first hole transport layer is arranged between the anode layer and the light emitting layer, wherein the at least one first hole transport layer comprises:

[0151] - at least one p-type electrical dopant of a quinone derivative, a metal oxide and / or a cyano-containing compound, or

[0152] - at least one p-type electrical dopant of a quinone derivative, a metal oxide and / or a cyano-containing compound, and at least one first hole transport matrix compound of a polycyclic aromatic hydrocarbon, a triarylamine compound and / or a heterocyclic aromatic compound;

[0153] - the at least one first electron transport layer is arranged between the cathode layer and the light emitting layer, wherein the first electron transport layer comprises:

[0154] - at least one redox n-type dopant of an elemental metal, an electrically neutral metal complex and / or an electrically neutral organic group, and

[0155] - at least one first electron transport aromatic matrix compound, wherein the aromatic matrix compound is a compound according to formula (2):

[0156]

[0157] wherein

[0158] X is selected from O, S, and Se;

[0159] R 1 and R 2 Independently selected from C1 to C 12 Alkyl, C6 to C 20 Aryl and C5 to C 20 Mixed aromatics;

[0160] R 3 Selected from formula (2A),

[0161]

[0162] Or formula (2B)

[0163]

[0164] in

[0165] * Mark the corresponding R 4 Or Ar 1 The group used to make the R 4 Or Ar 1 The position where it bonds with the phosphorus atom in formula (I);

[0166] R 4 Selected from C1 to C8 alkyl, C6 to C 20 Aryl and C5 to C 20 Mixed aromatics;

[0167] Ar 1 Selected from C6 to C 20 Aryl and C5 to C 20 Mixed aromatics;

[0168] Ar 2 Selected from C 18 To C 40 Aryl and C 10 To C 40 Mixed aromatics;

[0169] R 5 Selected from H, C1 to C 12 Alkyl, C6 to C 20 Aryl and C5 to C 20 Mixed aromatics;

[0170] n is selected from 0, 1, or 2.

[0171] Another aspect of the present invention provides an electroluminescent device comprising:

[0172] -At least one anode layer,

[0173] -At least one cathode layer,

[0174] - at least one light emitting layer,

[0175] - at least one first hole transport layer,

[0176] - at least one first electron transport layer;

[0177] wherein for improving the power efficiency the composition of the light emitting layer, the hole transport layer and the electron transport layer are matched to each other, wherein

[0178] - the at least one light emitting layer is arranged between the anode layer and the cathode layer, wherein the at least one light emitting layer comprises:

[0179] - at least one fluorescent emitter compound, preferably a blue fluorescent emitter compound, embedded in at least one polar emitter host compound, wherein

[0180] - the at least one polar emitter host compound is an anthracene compound represented by chemical formula 1 and optionally at least one polar emitter host compound can additionally have a gas phase dipole moment in the range of about > 0.2 Debye to about < 2.0 Debye, calculated using the hybrid functional B3LYP with Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5 for the lowest energy conformational isomer found by using the program package TURBOMOLE V6.5 with hybrid functional B3LYP with Gaussian 6-31G* basis set:

[0181]

[0182] wherein

[0183] A 1 selected from substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl;

[0184] A 2 selected from substituted or unsubstituted C1 to C 10 alkyl groups, substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl;

[0185] A 3 selected from substituted or unsubstituted C1 to C 10 alkyl groups, substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl;

[0186] A 4 selected from substituted or unsubstituted C6-C 60 aryl or C6-C 60heteroaryl, preferably C6-C 60 heteroaryl;

[0187] - the at least one first hole transport layer is arranged between the anode layer and the light-emitting layer, wherein the at least one first hole transport layer comprises:

[0188] - at least one p-type electrical dopant of tetracyanoquinodimethane (TCNQ), 2,3,5,6-tetrafluoro-tetracyano-1,4-benzoquinone dimethane (F4-TCNQ), tungsten oxide, molybdenum oxide and / or a compound according to formulae HT-D1 and PD-2:

[0189] or

[0190] - at least one p-type electrical dopant of tetracyanoquinodimethane (TCNQ), 2,3,5,6-tetrafluoro-tetracyano-1,4-benzoquinone dimethane (F4-TCNQ), tungsten oxide, molybdenum oxide and / or a compound according to formulae HT-D1 and PD-2;

[0191] and additionally

[0192] - at least one first hole transport matrix compound of the following:

[0193]

[0194] and / or

[0195]

[0196] - the at least one first electron transport layer is arranged between the cathode layer and the light-emitting layer, wherein the first electron transport layer comprises:

[0197] - at least one redox n-type dopant of at least one electropositive metal selected from the group consisting of the essentially stable alkali metals, alkaline earth metals, rare earth metals and transition metals Ti, V, Cr and Mn; preferably selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Sm, Eu, Tm, Yb; more preferably selected from the group consisting of Li, Na, K, Rb, Cs, Mg and Yb; even more preferably selected from the group consisting of Li, Na, Cs and Yb; most preferably selected from the group consisting of Li, Na and Yb, and

[0198] - at least one first electron transport matrix compound, wherein the matrix compound is a compound according to formula 2 selected from the group consisting of compounds according to formulae Va to Vai:

[0199] - formulae Va to Ve:

[0200]

[0201] - formulae Vf to Vq:

[0202]

[0203]

[0204] - formulae Vr to Vt:

[0205]

[0206] - formulae Vu to Vai:

[0207]

[0208]

[0209] According to another embodiment of the electroluminescent device, wherein the at least one light-emitting layer comprises a light-emitter host compound comprising 4, 5, 6, 7, 8, 9, 10, 11 or 12 aromatic rings, independently selected from carbocyclic and heterocyclic rings, preferably at least three of the aromatic rings in the light-emitter host compound are fused aromatic rings, and further preferably at least one of the aromatic rings of the light-emitter host compound is a five- or six-membered heterocyclic ring, and further preferably at least one aromatic ring is a five-membered heterocyclic ring comprising an atom selected from one N, O and S, preferably a furan ring.

[0210] According to another embodiment of the electroluminescent device, wherein the at least one first hole-transporting layer comprises a p-type electrical dopant selected from:

[0211] a) an organic compound comprising at least one, preferably at least two, more preferably at least three, most preferably at least four electron-withdrawing groups selected from:

[0212] (i) a perhalogenated alkyl group, wherein the halogen in the perhalogenated alkyl group is preferably selected from F and CI, more preferably the perhalogenated alkyl group is a perfluoroalkyl group,

[0213] (ii) a carbonyl group,

[0214] (iii) a sulfonyl group,

[0215] (iv) a nitrile group, and

[0216] (v) a nitro group;

[0217] b) metal oxides, metal salts and metal complexes, wherein the metal in the metal oxide, metal salt and / or metal complex is preferably present in its highest oxidation state.

[0218] According to another embodiment of the electroluminescent device, wherein the at least one first hole transport layer comprises a p-type electrical dopant and at least one first hole transport matrix compound.

[0219] According to another embodiment of the electroluminescent device, wherein the at least one first hole transport matrix compound is selected from organic conjugated aromatic systems having at least 6 delocalized electrons.

[0220] According to another embodiment of the electroluminescent device, wherein the at least one first electron transport layer comprises a redox n-type dopant selected from:

[0221] a) an elemental metal, preferably selected from alkali metals, alkaline earth metals and rare earth metals; further preferably selected from Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Sm, Eu, Yb; more preferably selected from Li, Na, Cs, Mg, Sr, Yb; even more preferably selected from Li, Na, Mg, Yb; most preferably selected from Li and / or Yb;

[0222] b) an organic radical, preferably selected from diazolyl radicals, oxazolyl radicals and thiazolyl radicals;

[0223] c) a transition metal complex, wherein the transition metal is selected from group 3, 4, 5, 6, 7, 8, 9 or 10 of the periodic table and is in oxidation state (-I), (0), (I) or (II), preferably the transition metal complex is electrically neutral.

[0224] According to another embodiment of the electroluminescent device, wherein the at least one first electron transport aromatic matrix compound is selected from organic conjugated aromatic systems having at least 6 delocalized electrons.

[0225] According to another embodiment of the electroluminescent device:

[0226] For at least one light emitting layer:

[0227] - the emitter host compound comprises 4, 5, 6, 7, 8, 9, 10, 11 or 12 aromatic rings, independently selected from carbocyclic and heterocyclic rings, preferably at least three of the aromatic rings in the emitter host compound are fused aromatic rings, and further preferably at least one aromatic ring of the emitter host compound is a five- or six-membered heterocyclic ring, and further preferably at least one aromatic ring is a five-membered heterocyclic ring containing one atom selected from N, O and S, preferably a furan ring; and

[0228] For at least one first hole transport layer:

[0229] - the p-type electrical dopant is selected from:

[0230] a) organic compounds comprising at least one, preferably at least two, more preferably at least three, most preferably at least four electron- withdrawing groups selected from:

[0231] (i) perhalogenated alkyl groups, wherein the halogen in the perhalogenated alkyl group is preferably selected from F and CI, more preferably the perhalogenated alkyl group is a perfluoroalkyl group,

[0232] (ii) carbonyl groups,

[0233] (iii) sulfonyl groups,

[0234] (iv) nitrile groups, and

[0235] (v) nitro groups;

[0236] b) metal oxides, metal salts and metal complexes, wherein the metal in the metal oxide, metal salt and / or metal complex is preferably present in its highest oxidation state; and

[0237] - optionally at least one first hole transport matrix compound selected from organic conjugated aromatic systems having at least 6 delocalized electrons;

[0238] For at least one first electron transport layer:

[0239] - the redox n-type dopant is selected from:

[0240] a) an elemental metal, preferably selected from alkali metals, alkaline earth metals and rare earth metals; further preferably selected from Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Sm, Eu, Yb; more preferably selected from Li, Na, Cs, Mg, Sr, Yb; even more preferably selected from Li, Na, Mg, Yb; most preferably selected from Li and / or Yb;

[0241] b) an organic group, preferably selected from diazolyl groups, oxazolyl groups and thiazolyl groups;

[0242] c) a transition metal complex, wherein the transition metal is selected from group 3, group 4, group 5, group 6, group 7, group 8, group 9 or group 10 of the periodic table and is in oxidation state (-I), (0), (I) or (II), preferably the transition metal complex is electrically neutral;

[0243] - at least one first electron transport aromatic matrix compound is selected from organic conjugated aromatic systems having at least 6 delocalized electrons.

[0244] According to another embodiment of the electroluminescent device, wherein the emitter host compound has a gas phase dipole moment in the range of about > 0.3 Debye to about < 1.8 Debye, preferably in the range of about > 0.5 Debye to about < 1.6 Debye, even more preferred in the range of about > 0.6 Debye to about < 1.4 Debye and most preferred in the range of about > 0.7 Debye to about < 1.3 Debye, wherein the gas phase dipole moment is calculated using the hybrid functional B3LYP with Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5 for the lowest energy conformational isomer found by using the program package TURBOMOLE V6.5 with hybrid functional B3LYP with Gaussian 6-31G* basis set.

[0245] According to another embodiment of the electroluminescent device, wherein the first electron transporting aromatic matrix compound is an organic conjugated aromatic system with at least 6 delocalized electrons comprising a phosphine oxide group.

[0246] According to another embodiment of the electroluminescent device, wherein

[0247] - the emitter host compound has a gas phase dipole moment in the range of about > 0.3 Debye to about < 1.8 Debye, preferably in the range of about > 0.5 Debye to about < 1.6 Debye, even more preferred in the range of about > 0.6 Debye to about < 1.4 Debye and most preferred in the range of about > 0.7 Debye to about < 1.3 Debye, wherein the gas phase dipole moment is calculated using the hybrid functional B3LYP with Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5 for the lowest energy conformational isomer found by using the program package TURBOMOLE V6.5 with hybrid functional B3LYP with Gaussian 6-31G* basis set; and

[0248] - the first electron transporting aromatic matrix compound is an organic conjugated aromatic system with at least 6 delocalized electrons comprising a phosphine oxide group or the first electron transporting aromatic matrix compound is a compound according to formula 2, and preferably the first electron transporting aromatic matrix compound is an organic conjugated aromatic system with at least 6 delocalized electrons comprising a phosphine oxide group.

[0249] According to another embodiment of the electroluminescent device, wherein the emitter host compound is an anthracene compound represented by formula 1:

[0250]

[0251] wherein

[0252] A 1 selected from substituted or unsubstituted C6-C 60 aryl or C6-C 60heteroaryl;

[0253] A 2 selected from substituted or unsubstituted C1to C 10 alkyl groups, substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl;

[0254] A 3 selected from substituted or unsubstituted C1to C 10 alkyl groups, substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl;

[0255] A 4 selected from substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl, preferably C6-C 60 heteroaryl.

[0256] According to another embodiment of the electroluminescent device, wherein the first electron transporting aromatic matrix compound has the chemical formula 2:

[0257]

[0258] wherein

[0259] X is selected from O, S, Se;

[0260] R 1 and R 2 are independently selected from C1to C 12 alkyl, C6to C 20 aryl and C5to C 20 heteroaryl;

[0261] R 3 is selected from formula (2A),

[0262]

[0263] or formula (2B)

[0264]

[0265] wherein

[0266] * marks the respective R 4 or Ar 1 group which is used to bind the R 4 or Ar 1 group to the phosphorus atom in formula (I);

[0267] R 4 is selected from C1to C8alkyl, C6to C20 Aryl and C5 to C 20 Mixed aromatics;

[0268] Ar 1 Selected from C6 to C 20 Aryl and C5 to C 20 Mixed aromatics;

[0269] Ar 2 Selected from C 18 To C 40 Aryl and C 10 To C 40 Mixed aromatics;

[0270] R 5 Selected from H, C1 to C 12 Alkyl, C6 to C 20 Aryl and C5 to C 20 Mixed aromatics;

[0271] n is selected from 0, 1, or 2.

[0272] According to another embodiment of the electroluminescent device, wherein

[0273] -The host compound of the luminescent organism is an anthracene compound represented by chemical formula 1:

[0274]

[0275] in

[0276] A 1 Selected from substituted or unsubstituted C6-C 60 Aryl or C6-C 60 Mixed aromatics;

[0277] A 2 Selected from substituted or unsubstituted C1 to C 10 Alkyl groups, substituted or unsubstituted C6-C 60 Aryl or C6-C 60 Mixed aromatics;

[0278] A 3 Selected from substituted or unsubstituted C1 to C 10 Alkyl groups, substituted or unsubstituted C6-C 60 Aryl or C6-C 60 Mixed aromatics;

[0279] A 4 Selected from substituted or unsubstituted C6-C 60 Aryl or C6-C 60 Heteroaryl, preferably C6-C 60 heteroaryl; and

[0280] - said first electron transporting aromatic matrix compound has the chemical formula 2:

[0281]

[0282] wherein

[0283] X is selected from O, S, Se;

[0284] R 1 and R 2 are independently selected from C1to C 12 alkyl, C6to C 20 aryl and C5to C 20 heteroaryl;

[0285] R 3 is selected from formula (2A),

[0286]

[0287] or formula (2B)

[0288]

[0289] wherein

[0290] * marks the position in the respective R 4 or Ar 1 group which is used to bind said R 4 or Ar 1 group to the phosphorous atom in formula (I);

[0291] R 4 is selected from C1to C8alkyl, C6to C 20 aryl and C5to C 20 heteroaryl;

[0292] Ar 1 is selected from C6to C 20 aryl and C5to C 20 heteroaryl;

[0293] Ar 2 is selected from C 18 to C 40 aryl and C 10 to C 40 heteroaryl;

[0294] R 5 is selected from H, C1to C 12 alkyl, C6to C 20 aryl and C5to C 20 heteroaryl;

[0295] n is selected from 0, 1 or 2.

[0296] According to another embodiment of the electroluminescent device, wherein in chemical formula 1, C6-C 60 The heteroatom of the heteroaryl group is selected from N, O and / or S, preferably O.

[0297] According to another embodiment of the electroluminescent device, wherein in chemical formula 2, R 1 , R 2 , R 5 , Ar 1 and Ar 2 are substituted by at least one or all of a Ci to C 12 alkyl group and a Ci to C 12 heteroalkyl group.

[0298] According to another embodiment of the electroluminescent device, wherein

[0299] - in chemical formula 1, C6-C 60 The heteroatom of the heteroaryl group is selected from N, O and / or S, preferably O; and

[0300] - in chemical formula 2, R 1 , R 2 , R 5 , Ar 1 and Ar 2 are substituted by at least one or all of a Ci to C 12 alkyl group and a Ci to C 12 heteroalkyl group.

[0301] According to another embodiment of the electroluminescent device, wherein in chemical formula 1 :

[0302] - the C6-C 60 heteroaryl group comprises at least one five-membered ring, preferably the five-membered ring is a furan or thiophene ring; or

[0303] - the C6-C 60 aryl group comprises anthracene or benzanthracene; or

[0304] - the C6-C 60 heteroaryl group comprises benzofuran, dibenzofuran, benzonaphthofuran or dinaphthofuran.

[0305] According to another embodiment of the electroluminescent device, wherein in chemical formula 2, two substituents selected from R 1 , R 2 and R 3 form a 7-membered phosphacyclheptane with the phosphorus atom.

[0306] According to another embodiment of the electroluminescent device, wherein

[0307] - in chemical formula 1 :

[0308] - the C6-Ci8aryl group is selected from the group consisting of phenyl, biphenyl, terphenyl, quaterphenyl, anthracenyl, benzanthracenyl, fluorenyl, phenanthrenyl, and naphthyl; or 60 the heteroaryl group comprises at least one five-membered ring, preferably the five-membered ring is a furan or thiophene ring; or

[0309] - the C6-Ci8aryl group is selected from the group consisting of phenyl, biphenyl, terphenyl, quaterphenyl, anthracenyl, benzanthracenyl, fluorenyl, phenanthrenyl, and naphthyl; or 60 the aryl group comprises an anthracene or benzanthracene; or

[0310] - the C6-Ci8aryl group is selected from the group consisting of phenyl, biphenyl, terphenyl, quaterphenyl, anthracenyl, benzanthracenyl, fluorenyl, phenanthrenyl, and naphthyl; or 60 the heteroaryl group comprises a benzofuran, a dibenzofuran, a benzonaphthofuran, or a dinaphthofuran; and

[0311] - in chemical formula 2:

[0312] - two substituents selected from the group consisting of R 1 , R 2 , and R 3 form a 7-membered phosphacyclheptane with the phosphorus atom.

[0313] According to another embodiment of the electroluminescent device, wherein

[0314] - in chemical formula 1:

[0315] A 4 has the following formulae (IIa) to (IIi):

[0316]

[0317] wherein the * marks the position of the respective A 4 group in combination with the anthracene compound.

[0318] According to another embodiment of the electroluminescent device, wherein the anthracene compound according to chemical formula I is selected from the group consisting of formulae B1 to B7:

[0319]

[0320]

[0321] According to another embodiment of the electroluminescent device, wherein the first electron transporting aromatic matrix compound according to chemical formula 2 is selected from the group consisting of formulae Va to Vai:

[0322] - formulae Va to Ve:

[0323]

[0324] - formulae Vf to Vq:

[0325]

[0326] or

[0327] - formulae Vr to Vt:

[0328]

[0329] - formula Vu to Vai:

[0330]

[0331]

[0332]

[0333] According to a further embodiment of the electroluminescent device, wherein

[0334] - the anthracene compound according to formula 1 is selected from formulae B1 to B7:

[0335]

[0336] and

[0337] - the first electron transport aromatic matrix compound according to formula 2 is selected from formulae Va to Vai:

[0338] - formulae Va to Ve:

[0339]

[0340] - formulae Vf to Vq:

[0341]

[0342]

[0343] or

[0344] - formulae Vr to Vt:

[0345]

[0346] - formula Vu to Vai:

[0347]

[0348]

[0349] According to a further embodiment of the electroluminescent device, wherein the device additionally comprises a second electron transport layer comprising at least one second electron transport matrix compound, preferably a conjugated system comprising at least six delocalized electrons, and the second electron transport layer is arranged between the first electron transport layer and the light-emitting layer, preferably the second electron transport layer is arranged adjacent to the first electron transport layer and / or the light-emitting layer.

[0350] According to another embodiment of the electroluminescent device, wherein the second electron transport compound is an aromatic compound having a redox potential in the range of -2.2 to -2.4 V, the redox potential being measured against ferrocene / ferrocenium as reference by the standard procedure described below. The redox potential is measured against ferrocene / ferrocenium as reference by the standard procedure described below.

[0351] According to another embodiment of the electroluminescent device, wherein the second electron transport aromatic matrix compound has a gas phase dipole moment in the range of 0.1 Debye to 5.0 Debye, preferably 0.5 Debye to 4.5 Debye, more preferably 1.0 Debye to 4.0 Debye, even more preferably 1.2 Debye to 3.8 Debye and most preferably 1.5 Debye to 3.5 Debye, the gas phase dipole moment being calculated using the hybrid functional B3LYP with Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5 for the lowest energy conformational isomer found by using the program package TURBOMOLE V6.5 with hybrid functional B3LYP with Gaussian 6-31G* basis set.

[0352] The present application is further described in more detail.

[0353] electron transport region

[0354] The electron transport region of the organic layer stack can be provided on the light-emitting layer.

[0355] The electron transport region of the organic layer stack comprises at least a first electron transport layer and optionally a second electron transport layer. The electron transport region of the organic layer stack can further comprise an electron injection layer.

[0356] For example, the electron transport region of the organic layer stack can have the following structure: first electron transport layer / electron injection layer, or alternatively first electron transport layer / second electron transport layer / electron injection layer, but is not limited thereto. For example, the organic light-emitting diode according to one embodiment of the present application comprises at least one electron transport layer, and in this case, the electron transport layer comprising a p-type electrical dopant and at least one first electron transport matrix compound is defined as the first electron transport layer. In another embodiment, the organic light-emitting diode can comprise at least two electron transport layers in the electron transport region of the organic layer stack, and in this case, the electron transport layer in contact with the light-emitting layer is defined as the second electron transport layer.

[0357] The electron transport layer can comprise one or two or more different electron transport matrix compounds.

[0358] The thickness of the first electron transport layer can be from about 2 nm to about 100 nm, for example, from about 3 nm to about 30 nm. When the thickness of the first electron transport layer is in these ranges, the first electron transport layer can have improved electron transport auxiliary ability without significantly increasing the driving voltage.

[0359] The thickness of the optional second electron transport layer can be from about 10 nm to about 100 nm, for example, from about 15 nm to about 50 nm. When the thickness of the electron transport layer is in these ranges, the electron transport layer can have satisfactory electron transport ability without significantly increasing the driving voltage.

[0360] first electron transport matrix compound

[0361] The first electron transport matrix is not particularly limited. Like other materials contained outside the light-emitting layer in the device of the present application, the second electron transport matrix can not emit light.

[0362] According to one embodiment, the first electron transport matrix can be an organic compound, an organometallic compound, or a metal complex.

[0363] According to one embodiment, the first electron transport matrix can be a covalent compound comprising a conjugated system of at least 6 delocalized electrons. A covalent material in the broadest possible sense can be understood as a material in which at least 50% of all chemical bonds are covalent bonds, wherein coordination bonds are also considered to be covalent bonds. In the present application, the term encompasses in the broadest sense all usual electron transport matrices, which are mainly selected from organic compounds, but can also be selected, for example, from compounds comprising structural moieties not containing carbon, such as substituted 2,4,6-tri-bora-1,3,5 triazine, or from metal complexes, such as tris(8-hydroxyquinoline)aluminum.

[0364] The molecular covalent material can comprise low molecular weight compounds, which can preferably be stable enough to be processable by vacuum thermal evaporation (VTE). Alternatively, the covalent material can comprise polymeric covalent compounds, preferably compounds which are soluble in solvents and thus can be processed in solution. It is to be understood that a polymeric substantially covalent material can be cross-linked to form an infinite irregular network, however, it is assumed that such a cross-linked polymeric substantially covalent matrix compound still comprises a backbone as well as peripheral atoms. The backbone atoms of a covalent compound are covalently bound to at least two adjacent atoms. The other atoms of a covalent compound are peripheral atoms which are covalently bound to a single adjacent atom. Inorganic infinite crystals or fully cross-linked networks with partial covalent bonding but substantially lacking peripheral atoms, such as silicon, germanium, gallium arsenide, indium phosphide, zinc sulfide, silicate glass, etc. are not considered covalent matrices in the sense of the present application, as these fully cross-linked covalent materials only comprise peripheral atoms at the surface of the phase formed by such a material. A compound comprising at least a cation or at least an anion is still considered covalent if the at least cation or the at least anion comprises at least ten covalently bound atoms.

[0365] A preferred example of a covalent first electron transport matrix compound is an organic compound which consists mainly of covalently bound C, H, O, N, S, which can optionally further comprise covalently bound B, P, As, Se. In one embodiment, the first electron transport matrix compound lacks metal atoms and the majority of its backbone atoms are selected from C, O, S, N.

[0366] In another embodiment, the first 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.

[0367] An example of a conjugated system of delocalized electrons is a system of alternating pi bonds and sigma bonds. Optionally, one or more two-atom structural units with a pi bond between their atoms can be replaced by an atom with at least one lone electron pair, typically a divalent atom selected from O, S, Se, or 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 obeying Hückel's rule. Further preferably, the first electron transport matrix compound can comprise at least two aromatic or heteroaromatic rings connected or fused by covalent bonds.

[0368] In one specific embodiment, the first electron transport matrix compound comprises a ring consisting of covalently bound atoms, and at least one of the atoms in the ring is phosphorus.

[0369] In a more preferred embodiment, the phosphorus-containing ring consisting of covalently bound atoms is a phosphacyclheptane.

[0370] In another preferred embodiment, the first electron transport compound comprises a phosphine oxide group. Furthermore preferably, the first electron transport matrix compound comprises a heterocycle comprising at least one nitrogen atom. Examples of particularly advantageous nitrogen-containing heterocycle compounds for the first electron transport matrix compound of the inventive device are matrices comprising pyridine moieties, diazine moieties, triazine moieties, quinoline moieties, benzoquinoline moieties, quinazoline moieties, acridine moieties, benzoacridine moieties, dibenzoacridine moieties, oxadiazole moieties and benzoxadiazole moieties, alone or in combination.

[0371] The molecular weight (Mw) of the first electron transport matrix compound can be in the range of > 400 to < 850 g / mol, preferably in the range of > 450 to < 830 g / mol. If the molecular weight is chosen in this range, a particularly reproducible evaporation and deposition in vacuum at temperatures at which a good long-term stability is observed can be achieved.

[0372] Preferably, the first electron transport matrix compound can be essentially non- emissive.

[0373] In another embodiment, the first electron transport matrix compound can have a dipole moment higher than 2.3 Debye, the dipole moment being calculated using the hybrid functional B3LYP with the Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5 for the lowest energy conformational isomer found by using the program package TURBOMOLE V6.5 with the hybrid functional B3LYP with the Gaussian 6-31G* basis set. Combination with a redox dopant selected from the group of elemental metals can be one preferred embodiment.

[0374] According to another aspect of the present application, the first electron transport matrix compound has a value of the reduction potential which is not as negative as the value obtained for triphenylphosphine oxide and which is more negative than the value obtained for tetrakis(quinolin-5-yloxy)zirconium, if measured by cyclic voltammetry in tetrahydrofuran under the same conditions versus Fc / Fc +

[0375] Under these conditions, the redox potential of triphenylphosphine oxide is about -3.06 V and the reduction potential of tetrakis(quinolin-5-yloxy)zirconium is about -1.78 V.

[0376] According to another aspect of the present application, the first electron transport matrix compound has a value of the reduction potential which is not as negative as the value obtained for triphenylphosphine oxide and which is more negative than the value obtained for tetrakis(quinolin-5-yloxy)zirconium, if measured by cyclic voltammetry in tetrahydrofuran under the same conditions versus Fc / Fc + ​the value of the redox potential of the first electron transport matrix compound is more negative than the corresponding value obtained for tris(quinolin-5-yloxy)zirconium, preferably more negative than the corresponding value of 4,4'-bis(4,6-diphenyl-1,3,5-triazin-2-yl)-1,1 '-biphenyl, most preferably more negative than the corresponding value of 2,4,6-tris(biphenyl-4-yl)-1,3,5-triazine.

[0377] According to another aspect of the application, if measured by cyclic voltammetry in tetrahydrofuran under the same conditions with respect to Fc / Fc + the value of the redox potential of the first electron transport matrix compound is more negative than the corresponding value obtained for tris(quinolin-5-yloxy)zirconium, preferably more negative than the corresponding value of 4,4'-bis(4,6-diphenyl-1,3,5-triazin-2-yl)-1,1 '-biphenyl, most preferably more negative than the corresponding value of 2,4,6-tris(biphenyl-4-yl)-1,3,5-triazine.

[0378] The redox potential can be determined by the following standard method, at room temperature, using cyclic voltammetry with a potentiostat device Metrohm PGSTAT30 and software Metrohm Autolab GPES. The redox potential given under a particular compound is measured in an argon-deaerated anhydrous 0.1 M solution of the test substance in THF, with a 0.1 M tetrabutylammonium hexafluorophosphate supporting electrolyte between the platinum working electrodes, and with an Ag / AgCl quasi-standard electrode consisting of a silver wire covered with silver chloride and directly immersed in the measuring solution (Metrohm silver rod electrode), with a scan rate of 100 mV / s. The first operation is performed over the widest potential range set on the working electrode, then the range is adjusted as appropriate in the subsequent operations. The last three operations are performed by adding ferrocene (0.1 M concentration) as a standard. The average of the potentials corresponding to the cathodic and anodic peaks of the compound under study, minus the value of the redox potential of the standard Fc +The average values of the observed cathodic and anodic potentials after / Fc redox couple observation finally lead to the values reported above. All the compounds studied as well as the reported comparative compounds show a clear reversible electrochemical behavior.

[0379] According to various embodiments of the electroluminescent device, the first electron transport matrix compound can be selected from:

[0380] - an anthracene compound substituted with an aryl, heteroaryl or alkyl group, such as 3-[3'-(10-phenyl-9-anthryl)[1,1 '-biphenyl]-4-yl]-quinoline;

[0381] - a benzimidazole compound substituted with an aryl, heteroaryl or alkyl group, preferably 2-(4-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)-1 -phenyl-1 H- benzo[d]imidazole and / or 1 -(4-(10-([1,1 '-biphenyl]-4-yl)anthracen-9-yl)phenyl)-2- ethyl-1 H-benzo[d]imidazole;

[0382] - a phosphine oxide compound substituted with an aryl, heteroaryl or alkyl group, preferably (3-(dibenzo[c,h]acridin-7-yl)phenyl)diphenylphosphine oxide, 3-phenyl-3H- benzo[b]dinaphtho[2,1 -d: 1 ',2'-f]phosphinine-3-oxide, phenyldi(pyren-1 -yl)phosphine oxide, bis(4-(anthracen-9-yl)phenyl)(phenyl)phosphine oxide, (3-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)diphenylphosphine oxide, phenyldi(pyren-1 -yl)phosphine oxide, diphenyl(5-(pyren-1 -yl)pyridin-2-yl)phosphine oxide, diphenyl(4'-(pyren-1 -yl)-[1,1 '-biphenyl]-3-yl)phosphine oxide, diphenyl(4'-(pyren-1 -yl)-[1,1 '-biphenyl]-3-yl)phosphine oxide, (3'-(dibenzo[c,h]acridin-7-yl)-[1,1 '-biphenyl]-4-yl)diphenylphosphine oxide and / or phenylbis(3-(pyren-1 -yl)phenyl)phosphine oxide;

[0383] - a phenanthroline compound substituted with an aryl or heteroaryl group, preferably 2,4,7,9-tetraphenyl-1,10-phenanthroline, 4,7-diphenyl-2,9-di-p-tolyl-1,10- phenanthroline, 2,9-bis(biphenyl-4-yl)-4,7-diphenyl-1,10-phenanthroline, 1,3-bis(9- phenyl-1,10-phenanthrolin-2-yl)benzene and / or 3,8-bis(6-phenyl-2-pyridyl)-1,10- phenanthroline;

[0384] - a quinazoline compound substituted with an aryl or heteroaryl group, preferably 9-phenyl-9'-(4-phenyl-2-quinazolinyl)-3,3'-bi-9H-carbazole;

[0385] - a benzo[h]quinazoline compound substituted with an aryl or heteroaryl group, preferably 4-(2-naphthyl)-2-[4-(3-quinolinyl)phenyl]-benzo[h]quinazoline;

[0386] - a pyrido[3,2-h]quinazoline compound substituted with an aryl or heteroaryl group, preferably 4-(naphthalen-1-yl)-2,7,9-triphenylpyrido[3,2-h]quinazoline;

[0387] - a triazine compound substituted with an aryl or heteroaryl group, preferably 4,4'-bis(4,6-diphenyl-1,3,5-triazin-2-yl)biphenyl, 3-[4-(4,6-di-2-naphthalenyl-1,3,5-triazin-2-yl)phenyl]quinoline and / or 2-[3-(6'-methyl[2,2'-bipyridin]-5-yl)-5-(9-phenanthryl)phenyl]-4,6-diphenyl-1,3,5-triazine, and / or

[0388] - an acridine compound substituted with an aryl or heteroaryl group, preferably 7-(naphthalen-2-yl)dibenzo[c,h]acridine.

[0389] According to various embodiments of the electroluminescent device, the matrix compound for the first electron transport layer can be more preferably selected from a phosphine oxide compound substituted with an aryl, heteroaryl or alkyl group, preferably (3-(dibenzo[c,h]acridin-7-yl)phenyl)diphenylphosphine oxide, 3-phenyl-3H-benzo[b]dibenzonaphtho[2,1 -d: 1 ',2'-f]phosphepin-3-oxide, phenyldi(pyren-1 -yl)phosphine oxide, bis(4-(anthracen-9-yl)phenyl)(phenyl)phosphine oxide, (3-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)diphenylphosphine oxide, diphenyl(5-(pyren-1 -yl)pyridin-2-yl)phosphine oxide, diphenyl(4'-(pyren-1 -yl)-[1,1 '-biphenyl]-3-yl)phosphine oxide, diphenyl(4'-(pyren-1 -yl)-[1,1 '-biphenyl]-3-yl)phosphine oxide, (3'-(dibenzo[c,h]acridin-7-yl)-[1,1 '-biphenyl]-4-yl)diphenylphosphine oxide and / or phenylbis(3-(pyren-1 -yl)phenyl)phosphine oxide.

[0390] Suitable matrix compounds which can be suitable for the first electron transport layer are summarized in Table 1 below.

[0391] Table 1

[0392] Chemical structures of first ETL matrix compounds which can be suitable for use

[0393]

[0394]

[0395]

[0396]

[0397]

[0398]

[0399] According to various embodiments of the electroluminescent device, wherein the first electron transport layer comprises about < 100 wt.% to about > 30 wt.%, preferably < 95 wt.% to about > 40 wt.% of a matrix compound, based on the total weight of the first electron transport layer.

[0400] Preferably, the first electron transport matrix compound can be essentially non- emitting.

[0401] second electron transport matrix

[0402] The second electron transport compound is not particularly limited. Similar to the other materials comprised outside the light-emitting layer in the inventive device, the second electron transport matrix can be non-emitting.

[0403] According to one embodiment, the second electron transport matrix compound can be an organic compound, an organometallic compound or a metal complex.

[0404] The compounds listed as examples for the first electron transport matrix compound can also be used as second electron transport matrix compounds.

[0405] According to one embodiment, the device additionally comprises a second electron transport layer comprising at least one second electron transport matrix compound selected from the group consisting of covalent compounds comprising a conjugated system of at least 6 delocalized electrons, preferably from the group consisting of organic compounds comprising at least one aromatic ring, more preferably from the group consisting of organic compounds comprising at least two aromatic rings, even more preferably from the group consisting of organic compounds comprising at least three aromatic rings, most preferably from the group consisting of organic compounds comprising at least four aromatic rings; and the second electron transport layer is arranged between the first electron transport layer and the light-emitting layer, preferably the second hole transport layer is formed by a second electron transport matrix compound, and further preferably the second electron transport layer is arranged adjacent to the first electron transport layer and / or to the light-emitting layer.

[0406] According to one embodiment, the second electron transport matrix compound can be a covalent compound comprising a conjugated system of at least 6 delocalized electrons.

[0407] In one embodiment, the dipole moment of the second electron transport matrix compound is selected from ≥0.5 Debye to ≤4.5 Debye, preferably ≥1.0 Debye to <4.0 Debye, and more preferably ≥1.5 Debye to <3.5 Debye.

[0408] According to another aspect of the invention, when in tetrahydrofuran relative to Fc / Fc + During measurement, the redox potential of the second electron matrix compound can be selected from one that is not as negative as -2.35V and more negative than -2.14V, preferably one that is not as negative as -2.3V and more negative than -2.16V, and more preferably one that is not as negative as -2.25V and more negative than -2.16V.

[0409] redox n-type dopant

[0410] Redox n-type dopants should be understood as being equivalent to ferrocene / ferrocene when embedded in an electron transport matrix, compared to ferrocene under the same physical conditions via cyclic voltammetry. Reference redox compounds are compounds that increase the concentration of free electrons relative to the pure matrix being measured.

[0411] Under the operating conditions of electroluminescent devices (such as OLEDs), redox n-type dopants may not emit light. In one embodiment, the redox n-type dopant is selected from elemental metals, electrically neutral metal complexes, and / or electrically neutral organic groups.

[0412] The most practical benchmark for the strength of n-type dopant is its redox potential. There are no particular restrictions on how negative the redox potential can be.

[0413] The redox potential of ferrocene / ferrocene, a commonly used electron transport matrix in organic light-emitting diodes, can be determined by cyclic voltammetry. When measured with reference to the redox pair, the range is approximately -1.8V to -3.1V; for n-type dopants, the practically applicable range of the redox potential for n-type dopants that can effectively dope these matrices is a slightly wider range, approximately -1.7V to -3.3V.

[0414] Redox potential measurements are actually performed on corresponding redox pairs consisting of the reduced and oxidized forms of the same compound. In the case where the redox n-type dopant is an electrically neutral metal complex and / or an electrically neutral organic group, its redox potential is actually measured on redox pairs formed by:

[0415] (i) Electroneutral metal complexes and their cationic groups formed by extracting an electron from said electroneutral metal complexes, or

[0416] (ii) an electrochemically neutral organic group and a cation formed therefrom by extracting one electron from said electrochemically neutral organic group.

[0417] Preferably, for the respective redox couple consisting of measured by cyclic voltammetry against ferrocene / ferrocenium

[0418] (i) an electrochemically neutral metal complex and a cationic group formed therefrom by extracting one electron from said electrochemically neutral metal complex, or

[0419] (ii) an electrochemically neutral organic group and a cation formed therefrom by extracting one electron from said electrochemically neutral organic group.

[0420] In a preferred embodiment, the redox potential value of the n-dopant is between a value more positive by about 0.5 V and a value more negative by about 0.5 V compared to the reduction potential value of the selected electron transport matrix.

[0421] Electrochemically neutral metal complexes suitable as redox n-dopants can be, for example, strongly reducing complexes of some transition metals in low oxidation states. Particularly strong redox n-dopants can be selected from, for example, Cr(II), Mo(II) and / or W(II) guanidinate complexes such as W2(hpp)4, as described in more detail in WO 2005 / 086251.

[0422] Electrochemically neutral organic groups suitable as redox n-dopants can be, for example, organic groups that generate additional energy by stabilizing dimers, oligomers or polymers thereof, as described in more detail in EP 1 837 926 B1, WO 2007 / 107306 or WO 2007 / 107356. Specific examples of such suitable groups can be diazolyl groups, oxazolyl groups and / or thiazolyl groups.

[0423] An elemental metal is to be understood as a metal in its pure metallic state, in the state of a metal alloy or in the state of free atoms or metal clusters. It is to be understood that a metal deposited by vacuum thermal evaporation from a metallic phase, for example from a pure bulk metal, is vaporized in its elemental form. It is also to be understood that, if the vaporized elemental metal is deposited together with a covalent matrix, the metal atoms and / or clusters are embedded in the covalent matrix. In other words, it is to be understood that any metal-doped covalent material prepared by vacuum thermal evaporation contains at least some of the metal in its elemental form.

[0424] For use in consumer electronics, only metals containing stable nuclides or nuclides with very long radioactive decay half-lives can be applicable. As an acceptable level of nuclear stability, the nuclear stability of natural potassium can be adopted.

[0425] In one embodiment, the n-type dopant is selected from the group consisting of electropositive metals selected from the group consisting of alkali metals, alkaline earth metals, rare earth metals and first transition period metals Ti, V, Cr and Mn. Preferably, the n-type dopant is selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Sm, Eu, Tm, Yb; more preferably from the group consisting of Li, Na, K, Rb, Cs, Mg and Yb; even more preferably from the group consisting of Li, Na, Cs and Yb; most preferably from the group consisting of Li, Na and Yb.

[0426] The redox dopant can be substantially non-emissive.

[0427] hole injection layer

[0428] The hole injection layer can improve the interface properties between the anode and the organic material used for the hole transport layer, and can be applied on a non-planarized anode, thereby planarizing the surface of the anode. For example, the hole injection layer can include a material having a median value of energy level of highest occupied molecular orbital (HOMO) between the work function of the anode material and the HOMO level of the hole transport layer, to adjust the difference between the work function of the anode and the HOMO level of the hole transport layer.

[0429] When the hole transport region includes the hole injection layer 36, the hole injection layer can be formed on the anode by any one of a variety of methods, such as vacuum deposition, spin coating, casting, a Langmuir-Blodgett (LB) method, etc.

[0430] When the hole injection layer is formed using vacuum deposition, the vacuum deposition conditions can vary depending on the material 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, the vacuum deposition can be performed at a temperature of about 100°C to about 500°C, a pressure of about 10 -6 Pa to about 10 -1 Pa, and a deposition rate of about 0.1 to about 10 nm / sec, but the deposition conditions are not limited thereto.

[0431] When the hole injection layer is formed using spin coating, the coating conditions can vary depending on the material 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 can be in the range of about 2000 rpm to about 5000 rpm, and the temperature at which a heat treatment is performed after coating to remove the solvent can be in the range of about 80°C to about 200°C, but the coating conditions are not limited thereto.

[0432] hole transport layer

[0433] The conditions for forming the hole transport layer and the electron blocking layer can be defined based on the formation conditions of the hole injection layer described above.

[0434] The thickness of the hole transport portion of the charge transport region can be about 10 nm to about 1000 nm, for example, about 10 nm to about 100 nm. When the hole transport portion of the charge transport region includes a hole injection layer and a hole transport layer, the thickness of the hole injection layer can be about 10 nm to about 1000 nm, for example, about 10 nm to about 100 nm, and the thickness of the hole transport layer can be about 5 nm to about 200 nm, for example, about 10 nm to about 150 nm. When the thicknesses of the hole transport portion of the charge transport region, the HIL, and the HTL are within these ranges, satisfactory hole transport characteristics can be obtained without a significant increase in driving voltage.

[0435] The hole transport matrix material for the hole transport region is not particularly limited. It is preferable that it be a covalent compound comprising a conjugated system of at least 6 delocalized electrons, preferably an organic compound comprising at least one aromatic ring, more preferably an organic compound comprising at least two aromatic rings, even more preferably an organic compound comprising at least three aromatic rings, and most preferably an organic compound comprising at least four aromatic rings. Typical examples of hole transport matrix materials widely used in hole transport layers are polycyclic aromatic hydrocarbons, triarylamine compounds, and heterocyclic aromatic compounds. Suitable ranges of the frontier orbital energy levels of hole transport matrices useful in the respective layers of the hole transport region are well known. In terms of the redox potential of the redox couple of the HTL matrix / cationic group of the HTL matrix, the preferred value (as measured by cyclic voltammetry with respect to ferrocene / ferrocenium redox couple as a reference) can be in the range of 0.0-1.0 V, more preferably in the range of 0.2-0.7 V, and even more preferably in the range of 0.3-0.5 V.

[0436] In addition to the materials described above, the hole transport region of the organic layer stack should also include a p-type electrical dopant, which improves the electrical conductivity and / or hole injection from the anode.

[0437] p-type electrical dopant

[0438] The charge generation material can be uniformly or non-uniformly dispersed in the first hole transport layer.

[0439] The p-type electrical dopant can be one of a quinone derivative, an axi compound, a metal oxide, and a cyano-containing compound, but is not limited thereto. Non-limiting examples of the p-type dopant are a quinone derivative such as tetracyanoquinodimethane (TCNQ), 2,3,5,6-tetrafluoro-tetracyano-1,4-benzoquinone dimethane (F4-TCNQ), an axi compound such as PD-2, etc.; a metal oxide such as tungsten oxide, molybdenum oxide, etc.; and a cyano-containing compound such as the following compound HT-D1.

[0440]

[0441] buffer layer

[0442] The hole transport portion of the charge transport region can further include a buffer layer.

[0443] Suitable buffer layers can be disclosed in US 6 140 763, US 6 614 176, and US2016 / 248022.

[0444] The buffer layer can compensate for the optical resonance distance of light emitted from the EML according to the wavelength of the light, and thus can improve efficiency.

[0445] emissive layer

[0446] The light-emitting layer (EML) can be formed on the hole transport region by using vacuum deposition, spin coating, casting, an LB method, etc. When the light-emitting layer is formed using vacuum deposition or spin coating, the conditions of deposition and coating can be similar to those of the formation of the hole injection layer, but the conditions of deposition and coating can vary according to the materials used to form the light-emitting layer. The light-emitting layer can include a light-emitting host (EML host) and a light-emitting dopant (hereinafter, simply light-emitting).

[0447] The light-emitting can be a red, green, or blue light-emitting.

[0448] In one embodiment, the light-emitting host material is a polar light-emitting host compound. Preferably, the light-emitting host material can be a polar light-emitting host compound having a gas phase dipole moment in the range of about ≥ 0.2 Debye to about ≤ 2.0 Debye, calculated using the hybrid functional B3LYP with the Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5, for the lowest energy conformational isomer found by using the program package TURBOMOLE V6.5 with the hybrid functional B3LYP with the Gaussian 6-31G* basis set.

[0449] In one embodiment, the light-emitting host material is a polar light-emitting host compound having at least three aromatic rings independently selected from carbocyclic and heterocyclic rings.

[0450] In a preferred embodiment, the emitter host material can be a polar emitter host compound having at least three aromatic rings independently selected from carbocyclic and heterocyclic rings, said compound having a gas phase dipole moment in the range of about > 0.2 Debye to about < 2.0 Debye, calculated using the hybrid functional B3LYP with Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5 for the lowest energy conformational isomer found by using the program package TURBOMOLE V6.5 with hybrid functional B3LYP with Gaussian 6-31G* basis set.

[0451] In one embodiment, the emitter host material is a polar emitter host compound represented by chemical formula 1:

[0452]

[0453] wherein

[0454] A 1 selected from substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl;

[0455] A 2 selected from substituted or unsubstituted C1 to C 10 alkyl groups, substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl;

[0456] A 3 selected from substituted or unsubstituted C1 to C 10 alkyl groups, substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl;

[0457] A 4 selected from substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl, preferably C6-C 60 heteroaryl.

[0458] emissive host

[0459] The polar emitter host compound has at least three aromatic rings independently selected from carbocyclic and heterocyclic rings.

[0460] The polar emitter host compound can have a gas phase dipole moment in the range of about > 0.2 Debye to about < 2.0 Debye, calculated using the hybrid functional B3LYP with Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5 for the lowest energy conformational isomer found by using the program package TURBOMOLE V6.5 with hybrid functional B3LYP with Gaussian 6-31G* basis set.

[0461] According to one embodiment of the electroluminescent device, the polar emitter host compound has at least three aromatic rings independently selected from carbocyclic and heterocyclic rings and can have a gas phase dipole moment in the range of about > 0.2 Debye to about < 2.0 Debye, calculated using the hybrid functional B3LYP with Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5 for the lowest energy conformational isomer found by using the program package TURBOMOLE V6.5 with hybrid functional B3LYP with Gaussian 6-31G* basis set.

[0462] In another embodiment, the emitter host compound can have a gas phase dipole moment in the range of about > 0.3 Debye to about < 1.8 Debye, preferably in the range of about > 0.5 Debye to about < 1.6 Debye, even more preferably in the range of about > 0.6 Debye to about < 1.4 Debye and most preferably in the range of about > 0.7 Debye to about < 1.3 Debye, calculated using the hybrid functional B3LYP with Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5 for the lowest energy conformational isomer found by using the program package TURBOMOLE V6.5 with hybrid functional B3LYP with Gaussian 6-31G* basis set.

[0463] Dipole moment of a molecule containing N atoms Given by

[0464]

[0465]

[0466] where q i and is the local charge and position of atom i in the molecule.

[0467] The local charges and atomic positions are calculated for the lowest energy conformation of the ground state of the gas phase molecule using the hybrid functional B3LYP implemented in the program package TURBOMOLE V6.5 with the Gaussian 6-31G* basis set by a standardization method. If more than one conformation is possible, the energies of the possible conformations are first calculated using the hybrid functional B3LYP implemented in the program package TURBOMOLE V6.5 with the Gaussian 6-31G* basis set, and the conformation with the lowest total energy is selected to determine the dipole moment.

[0468] The dipole moments and redox potentials of selected compounds suitable as second electron transport matrix compounds are given in Table 2.

[0469] Table 2

[0470]

[0471]

[0472]

[0473] According to another aspect of the present application, the emitter host has a redox potential, respectively, which is more negative than the corresponding value obtained for 7-([1,1 '-biphenyl]-4-yl)dibenzo[c,h]acridine, preferably more negative than the corresponding value of 9,9',10,10'-tetraphenyl-2,2'-bianthracene, more preferably more negative than the corresponding value of 2,9-di([1,1 '-biphenyl]-4-yl)-4,7-diphenyl-1,10-phenanthroline, even more preferably more negative than the corresponding value of 2,4,7,9-tetraphenyl-1,10-phenanthroline, even more preferably more negative than the corresponding value of 9,10-di(naphthalen-2-yl)-2-phenylanthracene, even more preferably more negative than the corresponding value of 2,9-bis(2-methoxyphenyl)-4,7-diphenyl-1,10-phenanthroline, most preferably more negative than the corresponding value of 9,9'-spirobi[fluorene]-2,7-diylbis(diphenylphosphine oxide), if measured by cyclic voltammetry in tetrahydrofuran under the same conditions. +

[0474] The emitter is mixed in a small amount to cause light emission. The emitter can be, for example, an inorganic, organic, or organometallic compound, and one or more of these can be used.

[0475] The emitter can be a fluorescent emitter; for example, the following compounds 4, 4,4'-bis(4-diphenylaminostyryl)biphenyl (DPAVBi), 2,5,8,1 1 -tetra-tert-butylperylene (TBPe), and 2,5,8,1 1 -tetra-tert-butylperylene (TBPe) are examples of fluorescent blue emitters.

[0476] ​

[0477] The thickness of the light-emitting layer can be about 10 nm to about 100 nm, for example, about 20 nm to about 60 nm. When the thickness of the light-emitting layer is within these ranges, the light-emitting layer can have improved light-emitting characteristics without a significant increase in driving voltage.

[0478] electron injection layer

[0479] According to another aspect of the present application, the organic electroluminescent device can further include an electron injection layer between the first electron transport layer and the cathode.

[0480] The electron injection layer (EIL) can facilitate injection of electrons from the cathode.

[0481] According to another aspect of the present application, the electron injection layer comprises:

[0482] (i) a positively electronegative metal selected from alkali metals, alkaline earth metals, and rare earth metals in a substantially elemental form, preferably selected from Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Eu, and Yb, more preferably selected from Li, Na, Mg, Ca, Sr, and Yb, even more preferably selected from Li and Yb, most preferably Yb; and / or

[0483] (ii) an alkali metal complex and / or an alkali metal salt, preferably a Li complex and / or salt, more preferably lithium hydroxyquinolinate, even more preferably lithium 8-hydroxyquinolinate, most preferably the alkali metal salt and / or complex of the second electron transport layer is the same as the alkali metal salt and / or complex of the injection layer.

[0484] The electron injection layer can include at least one selected from LiF, NaCl, CsF, Li2O, and BaO.

[0485] The thickness of the EIL can be 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 can have satisfactory electron injection capability without a significant increase in driving voltage.

[0486] cathode

[0487] The material for the cathode can be a metal, an alloy, or an electrically conductive compound having a low work function, or a combination thereof. Specific examples of the material for the cathode can be lithium (Li), magnesium (Mg), aluminum (Al), aluminum-lithium (Al-Li), calcium (Ca), magnesium-indium (Mg-In), magnesium-silver (Mg-Ag), etc. In order to manufacture a top emission light-emitting device having a reflective anode deposited on a substrate, the cathode can be shaped as a transmissive electrode made of, for example, indium tin oxide (ITO) or indium zinc oxide (IZO).

[0488] In devices comprising a transparent metal oxide cathode or a reflective metal cathode, the cathode can have a thickness of about 50 nm to about 100 nm, while a semi-transparent metal cathode can be as thin as about 5 nm to about 15 nm.

[0489] anode

[0490] The material for the anode can be a metal or a metal oxide, or an organic material, preferably a material having an ionization potential higher than about 4.8 eV, more preferably higher than about 5.1 eV, most preferably higher than about 5.3 eV. Preferred metals are noble metals such as Pt, Au or Ag, preferred metal oxides are transparent metal oxides such as ITO or IZO, which can be advantageously used in bottom emission OLEDs with a reflective cathode.

[0491] In devices comprising a transparent metal oxide anode or a reflective metal anode, the anode can have a thickness of about 50 nm to about 100 nm, while a semi-transparent metal anode can be as thin as about 5 nm to about 15 nm.

[0492] electroluminescent device

[0493] According to another embodiment of the electroluminescent device, the first hole transport layer is arranged adjacent to the anode layer.

[0494] According to another embodiment of the electroluminescent device, the electroluminescent device additionally comprises a second hole transport layer, the second hole transport layer comprising a second hole transport matrix compound, preferably the second hole transport layer being formed of a second hole transport matrix compound, wherein the second hole transport layer is arranged between the first hole transport layer and the light-emitting layer, and further preferably the second hole transport layer is arranged adjacent to the first hole transport layer and adjacent to the light-emitting layer.

[0495] According to another embodiment, a display device comprising at least one electroluminescent device according to the present application is provided.

[0496] According to another embodiment, the hole transport region can comprise a third hole transport layer, which can be in direct contact with the light-emitting layer.

[0497] According to another embodiment, the third hole transport layer can be in direct contact with the second hole transport layer.

[0498] According to another embodiment, the second electron transport layer can be in contact sandwiched between the light-emitting layer and the first electron transport layer.

[0499] According to another embodiment, the second electron transport layer can be in direct contact with the light-emitting layer.

[0500] According to another embodiment, the first electron transport layer can be in contact with the second electron transport layer and the electron injection layer.

[0501] According to another embodiment, the first electron transport layer can be in direct contact with the cathode electrode.

[0502] According to another embodiment, the second electron transport layer can be in contact with the first electron transport layer and the cathode layer.

[0503] According to another aspect of the present application, there is provided an electronic device comprising at least one organic light emitting device according to any of the embodiments described throughout the present application, preferably, the electronic device comprises an organic light emitting diode according to one of the embodiments described throughout the present application. More preferably, the electronic device is a display device.

[0504] Hereinafter, the embodiments are explained in more detail with reference to Examples. However, the present disclosure is not limited to the following Examples. BRIEF DESCRIPTION OF DRAWINGS

[0505] figure 1 is a cross-sectional view illustrating an organic light emitting diode according to one embodiment of the present application.

[0506] figure 2 and figure 3 is a cross-sectional view illustrating a part of an organic layer of an organic light emitting diode according to one embodiment of the present application.

[0507] Hereinafter, the drawings are explained in more detail with reference to Examples. However, the present disclosure is not limited to the following drawings.

[0508] figures 1 to 3 is a schematic cross-sectional view of organic light emitting diodes 100, 300 and 400 according to one embodiment of the present application. Hereinafter, referring to figure 1 The structure of an organic light emitting diode according to one embodiment of the present application and a method of manufacturing the same are as follows. The organic light emitting diode 100 has the following structure in which an anode 110; an organic layer stack 105 including a hole transport region (not shown), an electron transport region (not shown), an emission layer 130; and a cathode 150 are sequentially stacked.

[0509] A substrate can be provided on the anode 110 or under the cathode 150. The substrate can be selected from common substrates used in general organic light emitting diodes, and can be a glass substrate or a transparent plastic substrate.

[0510] The anode 110 can be formed by depositing or sputtering an anode material onto a substrate. The anode material can be selected from materials with high work function to facilitate hole injection. The anode 110 can be a reflective electrode, a transflective electrode, or a transmissive electrode. The anode material can be indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO2), zinc oxide (ZnO), etc. Alternatively, it can be a metal such as silver (Ag) or gold (Au) or an alloy thereof.

[0511] The anode 110 may have a single-layer or a multi-layer structure with two or more layers.

[0512] Organic light-emitting diodes 100, 300, and 400 according to one embodiment of the present invention may include a hole transport region; a light-emitting layer 130; and a first electron transport layer 31.

[0513] See figure 2 The organic layer stack 105 may include at least two layered hole transport layers, and in this case, the hole transport layer in contact with the light-emitting layer (130) is defined as the second hole transport layer 135 and the hole transport layer in contact with the anode (110) is defined as the first hole transport layer 34. The organic layer stack 105 also includes two electron transport layers, namely the first electron transport layer 31 and the second electron transport layer 33. The first hole transport layer of the stack 105 may have a hole injection layer function, and the third hole transport layer, which has an electron blocking layer function and / or a buffer layer function, may be further sandwiched between the second hole transport layer 135 and the light-emitting layer 130.

[0514] The hole transport region of stack 105 may consist only of the hole injection layer or only of the hole transport layer. Alternatively, the hole transport region may have the following characteristics: figure 3 The structure shown has hole injection layer 36 / hole transport layer 34 or hole injection layer 36 / hole transport layer 34 / electron blocking layer (135) stacked sequentially from anode 110.

[0515] For example, an electron injection layer 37 may be additionally included, such that the OLED may include an anode 110, a first hole transport layer 36 with hole injection function, a second hole transport layer 34, a third hole transport layer 135 with electron blocking function, an emitting layer 130, a second electron transport layer 33, a first electron transport layer 31, an electron injection layer 37, and a cathode 150, which are stacked in sequence.

[0516] according to figure 3An organic electroluminescent device (400) comprises an anode (110), a first hole transport layer (36), a second hole transport layer (34), an optional electron blocking layer (135), an emission layer (130), an optional second electron transport layer (33), a first electron transport layer (31), an optional electron injection layer (37), a cathode (150), wherein the layers are arranged in this order.

[0517] The first hole transport layer 36 comprises at least one p-type electrical dopant, which can be a material having a median value of energy levels of the highest occupied molecular orbital (HOMO) between the work function of the anode and the HOMO energy level of the second hole transport matrix of the second hole transport layer 34 to adjust the difference between the work function of the anode and the HOMO energy level of the second hole transport matrix of the second hole transport layer 34. DETAILED DESCRIPTION

[0518] synthesis of auxiliary compounds

[0519] The compounds ETM-7, ETM-10 and ETM-11 were prepared by the methods disclosed in WO2011 / 154131 and WO2016 / 171356.

[0520] general procedure for manufacturing oleds

[0521] Model devices were prepared using the auxiliary materials according to formulae F1, F2 and PD-2:

[0522]

[0523] Biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine, CAS 1242056-42-3, F1;

[0524]

[0525] N,N-Bis(4-(dibenzo[b,d]furan-4-yl)phenyl)-[1,1':4',1"-terphenyl]-4-amine, CAS 1198399-61-9, F2;

[0526]

[0527] 2,2',2"-(Cyclopropane-1,2,3-triylidene)tris(2-(p-cyanotetrafluorophenyl)acetonitrile), CAS 1224447-88-4, PD-2.

[0528] The compound ETM-12 has the following formula:

[0529] and its redox potential is -2.27 V.

[0530] device example 1 (top-emitting blue oled)

[0531] On a glass substrate, a 100 nm thick silver layer was deposited by vacuum thermal evaporation (VTE) as anode, followed by a 10 nm thick first hole transport layer of a compound according to F1 doped with a compound according to formula PD2, wherein the weight ratio of matrix to dopant is 92:8 wt.%, followed by a 117 nm thick undoped second hole transport layer made of pure compound according to formula F1, and followed by a 5 nm thick undoped third hole transport layer made of pure compound according to formula F2. Subsequently, a blue fluorescent light emitting layer of compound B1 (Sun Fine Chemicals) with a thickness of 20 nm was deposited, which was doped with the fluorescent emitter NUBD370 (Sun Fine Chemicals) (97:3 wt.%). A second electron transport layer of 5 nm thickness of the second electron transport matrix compounds of Table 3 tested and a first electron transport layer of 33 nm thickness of the first electron transport matrix compound (Vr) doped with elemental Ytterbium (90:10 wt.%); or, subsequently on the light emitting layer, a metal alloy ND1 comprising 2.6 wt.% Na and 97.4% Zn was deposited. Finally, a silver layer with a thickness of 11 nm was deposited as cathode on top of the metal doped layer, followed by a 75 nm thick light outcoupling layer made of pure compound according to formula F1.

[0532] By encapsulating the device with a glass slide, the OLED stack can be protected from environmental conditions. Thereby, a cavity is formed, which comprises a getter material for further protection.

[0533] evaluation of device experiments

[0534] To evaluate the performance of the embodiments of the present application compared to the prior art, the current efficiency was measured at ambient conditions (20°C). The operating voltage measurements were performed using a Keithley 2400 source meter, and for top emitting devices at a standard current density of 10 mA / cm 2 and for bottom emitting devices at a standard current density of 15 mA / cm 2 The CIE coordinates and the luminance in candela were measured using a calibrated spectrometer CAS 140 from Instrument Systems. The lifetime LT of the devices was measured using a Keithley 2400 source meter at ambient conditions (20°C) and a standard current density of 10 mA / cm 2 or 15 mA / cm 2 and is reported in hours.

[0535] The luminance of the devices was measured using a calibrated photodiode. The lifetime LT is defined as the time it takes until the luminance of the device decreases to 97% of its initial value.

[0536] For top-emitting devices, the luminance was determined at 10 mA / cm 2 The external quantum efficiency EQE and the power efficiency P eff (lm / W) in terms of the optical output.

[0537] For determining the efficiency EQE (%) the optical output of the device was measured using a calibrated photodiode.

[0538] For determining the power efficiency (lm / W), in a first step the luminous density (Candela per square meter, cd / m2) was measured using a spectrometer array CAS 140 CT from Instrument Systems, which has been calibrated by Deutsche Akkreditierungsstelle (DAkkS). 2 In a second step, the luminous density was then multiplied by p and divided by the voltage and the current density.

[0539] In bottom-emitting devices, the emission is mainly Lambertian and is quantified in terms of external quantum efficiency in percent (EQE) and power efficiency (lm / W).

[0540] The results in terms of operating voltage and current efficiency C eff are shown in Table 3.

[0541] Table 3a: Top-emitting device (application, see above) comprising: a 20 nm thick light-emitting layer consisting of compound B-1 (having a dipole moment of 0.94 Debye, calculated using the hybrid functional B3LYP with Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5 for the lowest energy conformational isomer found by using the program package TURBOMOLE V6.5 with the hybrid functional B3LYP with Gaussian 6-31G* basis set) with 3 wt% NUBD-370; an undoped 5 nm thick second electron transport layer (ETL); a 33 nm thick first electron transport layer (EIL1) comprising a first electron transport matrix compound of formula 2, e.g. compound Vr, doped with 10 wt% of a given n-type dopant; and an 11 nm thin silver cathode. ND-1 is an alloy comprising 2.6 wt% Na and 97.4% Zn.

[0542] Table 3a

[0543]

[0544] The comparative device is completely analogous to the device of table 3a, with the difference that the emitter host B1 of the present application is replaced by the less polar compound ABH-113 having the structure according to formula C1

[0545]

[0546] The compound C1 (CAS 1214263-47-4) has a dipole moment of 0.14 Debye, calculated using the hybrid functional B3LYP with Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5 for the lowest energy conformation isomer found by using the program package TURBOMOLE V6.5 with hybrid functional B3LYP with Gaussian 6-31G* basis set. The performance of the comparative device is given in table 3b.

[0547] Table 3b: Top-emitting device (comparative)

[0548]

[0549] A comparison of the results of the inventive devices according to table 3a and the comparative devices according to table 3b shows that the matching of the dipole moment of the emitter host to the adjacent layers as required by the present application significantly improves the device performance.

[0550] Analogous to example 1, another device was prepared which lacks a second electron transport layer. Comparative devices 2A, 2B and 2C were prepared with compound C1 as emitter host instead of compound B1. The results of the color coordinates y, operating voltage, current efficiency C eff and power efficiency P eff are reported in table 4.

[0551] Table 4

[0552]

[0553] A comparison of the results of the inventive devices 2a, 2b and 2c with the results of the corresponding comparative devices 2A, 2B and 2C, respectively, shows that even if the second electron transport layer is omitted, the matching of the dipole moment of the emitter host to the adjacent layers as required by the present application significantly improves the device performance.

[0554] Table 5 gives the energy levels and dipole moments of exemplary emitter hosts B1-B7, calculated using the hybrid functional B3LYP with Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5 for the corresponding lowest energy conformation isomer found by using the program package TURBOMOLE V6.5 with hybrid functional B3LYP with Gaussian 6-31G* basis set.

[0555] Table 5

[0556] structure homo [e v] lumo [e v] energy gap [e v] dipole [debye] B1 -5.13 -1.65 3.48 0.93 B2 -5.11 -1.63 3.48 0.64 B3 -5.11 -1.65 3.46 0.92 B4 -5.21 -1.58 3.63 0.77 B5 -5.16 -1.55 3.61 1.00 B6 -5.18 -1.58 3.60 1.51 B7 -5.10 -1.64 3.46 1.37

[0557] Clearly, the introduction of the furan and / or thiophene ring significantly increases the dipole moment of the lowest energy conformation isomer compared to compound C1.

[0558] It should be understood that wherever values and ranges of values are provided herein, all values and ranges of values between the stated values and ranges of values are also intended to be encompassed. Furthermore, any value or range of values provided herein is intended to be a maximum or minimum value or range of values.

Claims

1. An electroluminescent device, comprising: - at least one anode layer, - at least one cathode layer, - at least one light-emitting layer, - at least one first hole transport layer, - at least one first electron transport layer; wherein for improving power efficiency the composition of the light-emitting layer, the hole transport layer and the electron transport layer are matched to each other, wherein - the at least one light-emitting layer is arranged between the anode layer and the cathode layer, wherein the at least one light-emitting layer comprises: - at least one fluorescent emitter compound embedded in at least one polar emitter host compound, wherein - the at least one polar emitter host compound has at least three aromatic rings independently selected from carbocyclic and heterocyclic rings and has a gas phase dipole moment in the range of > 0.2 Debye to < 2.0 Debye, calculated using the hybrid functional B3LYP with Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5 for the lowest energy conformational isomer found by using the program package TURBOMOLE V6.5 with hybrid functional B3LYP with Gaussian 6-31G* basis set; - the at least one first hole transport layer is arranged between the anode layer and the light-emitting layer, wherein the at least one first hole transport layer comprises: - at least one p-type electrical dopant, or - at least one p-type electrical dopant and at least one first hole transport matrix compound; - the at least one first electron transport layer is arranged between the cathode layer and the light-emitting layer, wherein the first electron transport layer comprises: - at least one redox n-type dopant, and - at least one first electron transport matrix compound; - the redox n-type dopant does not emit light under operating conditions of the electroluminescent device; wherein the electroluminescent device additionally comprises a second electron transport layer, which comprises at least one second electron transport matrix compound selected from covalent compounds comprising a conjugated system of at least 6 delocalized electrons; - the second electron transport layer is arranged between the first electron transport layer and the light-emitting layer, - the second electron transport layer is formed from a second electron transport matrix compound, - the second electron transport layer is arranged adjacent to the first electron transport layer and / or the light-emitting layer, and - the second electron transport matrix compound has a gas phase dipole moment in the range of 0.1 Debye to 5.0 Debye, calculated using the hybrid functional B3LYP with Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5 for the lowest energy conformational isomer found by using the program package TURBOMOLE V6.5 with hybrid functional B3LYP with Gaussian 6-31G* basis set, the dipole moment of a molecule containing an N atom is given by where q i and are the local charge and position of atom i in the molecule and are calculated for the ground state of the lowest energy conformation of the gas phase molecule using the hybrid functional B3LYP with the Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5 by a standardization procedure, if more than one conformation is feasible, the conformation with the lowest total energy is chosen to determine the dipole moment.

2. The electroluminescent device according to claim 1, wherein for the at least one light-emitting layer: - the emitter host compound comprises 4, 5, 6, 7, 8, 9, 10, 11 or 12 aromatic rings independently selected from carbocyclic and heterocyclic rings; and For the at least one first hole transport layer: - the p-type electrical dopant is selected from: a) organic compounds comprising at least one electron withdrawing group selected from: (i) a perhalogenated alkyl group, (ii) a carbonyl group, (iii) a sulfonyl group, (iv) a nitrile group, and (v) a nitro group; b) metal oxides, metal salts and metal complexes; and - the optional at least one first hole transport matrix compound is selected from covalent compounds comprising a conjugated system of at least 6 delocalized electrons; For the at least one first electron transport layer: - the redox n-type dopant is selected from: a) an elemental metal; b) an organic radical; c) a transition metal complex, wherein the transition metal is selected from group 3, 4, 5, 6, 7, 8, 9 or 10 of the periodic table and is in oxidation state (-I), (0), (I) or (II); - the at least one first electron transport matrix compound is selected from covalent compounds comprising a conjugated system of at least 6 delocalized electrons.

3. The electroluminescent device according to claim 1, wherein - the emitter host compound has a gas phase dipole moment in the range of > 0.3 Debye to < 1.8 Debye, calculated using the hybrid functional B3LYP with Gaussian 6-31G* basis set implemented in the program package TURBOMOLE V6.5 for the lowest energy conformational isomer found by using the program package TURBOMOLE V6.5 with hybrid functional B3LYP with Gaussian 6-31G* basis set; - the first electron transport matrix compound comprises at least one phosphine oxide group or at least one phenanthroline group.

4. The electroluminescent device according to any one of claims 1 to 3, wherein - the polar emitter host compound is an anthracene compound represented by chemical formula 1: wherein A 1 selected from substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl; A 2 selected from substituted or unsubstituted C1to C 10 alkyl groups, substituted or unsubstituted C6-C 60 aryl groups, or C6-C 60 heteroaryl groups; A 3 selected from substituted or unsubstituted C1to C 10 alkyl groups, substituted or unsubstituted C6-C 60 aryl groups, or C6-C 60 heteroaryl groups; A 4 selected from substituted or unsubstituted C6-C 60 aryl or C6-C 60 heteroaryl; and - the first electron transport matrix compound has chemical formula 2: wherein X is selected from O, S, Se; R 1 and R 2 are independently selected from the group consisting of C1to C 12 alkyl, C6to C 20 aryl and C5to C 20 heteroaryl; R 3 selected from formula (2A), or formula (2B) wherein * the corresponding R 4 or Ar 1 group for the position of R 4 or Ar 1 bonding to the phosphorus atom in formula (2); R 4 selected from C1to C8alkyl, C6to C 20 aryl and C5to C 20 heteroaryl; Ar 1 selected from C6to C 20 aryl and C5to C 20 heteroaryl; Ar 2 selected from C 18 to C 40 aryl and C 10 to C 40 heteroaryl; R 5 selected from H, C1to C 12 alkyl, C6to C 20 aryl and C5to C 20 heteroaryl; n is selected from 0, 1 or 2.

5. The electroluminescent device according to claim 4, wherein - in the chemical formula 1, the C6-C 60 the heteroatom of the heteroaryl group is selected from N, O and / or S; and - in Chemical Formula 2, at least one or all of R 1 , R 2 , R 5 , Ar 1 , and Ar 2 are substituted with a C1 to C 12 alkyl and a C1 to C 12 heteroalkyl group.

6. The electroluminescent device according to claim 4, wherein - in chemical formula 1: -The C6-C 60 Heteroaryl groups contain at least one five-membered ring; or - said C6-Ci8-aryl comprises anthracene or benzanthracene; or 60 - said C6-Ci8-aryl comprises anthracene or benzanthracene; or - said C6-Ci8-aryl comprises phenyl, biphenyl, terphenyl, quaterphenyl, or benzophenone; and 60 heteroaryl comprises benzofuran, dibenzofuran, benzonaphthofuran, or dinaphthofuran; and - in chemical formula 2: - two substituents selected from R 1 , R 2 , and R 3 form a 7-membered phosphacyclononane with the phosphorus atom.

7. The electroluminescent device according to claim 4, wherein - in chemical formula 1: A 4 having the following formulae (IIa) to (IIi): wherein the asterisk marks the corresponding A 4 position of the combination of the group with the anthracene compound.

8. The electroluminescent device according to claim 4, wherein - the anthracene compound according to chemical formula 1 is selected from formulae B1 to B7: and - the first electron transport aromatic matrix compound comprising a phosphine oxide group according to chemical formula 2 is selected from formulae Va to Vai: - formulae Va to Ve: - formulae Vf to Vq: or - formulae Vr to Vt: - formulae Vu to Vai:

9. Electroluminescent device according to any one of claims 1 to 3, wherein the second electron transport matrix compound has a redox potential in the range of -2.2 V to -2.4 V measured against ferrocenium / ferrocene as reference by standard method. a redox potential in the range of -2.2 V to -2.4 V measured against ferrocenium / ferrocene as reference by standard method, using cyclic voltammetry at room temperature with a potentiostat device Metrohm PGSTAT30 and software Metrohm Autolab GPES, under argon atmosphere, with a 0.1 M tetrabutylammonium hexafluorophosphate supporting electrolyte between platinum working electrodes, and with a Metrohm silver rod electrode Ag / AgCl standard electrode consisting of a silver wire covered with silver chloride and directly immersed in the measuring solution, the redox potential was measured in an argon deaerated anhydrous 0.1 M test substance THF solution with a scan rate of 100 mV / s, the first operation was performed in the widest potential range set on the working electrode, then the range was adjusted as appropriate in the subsequent operations, the last three operations were performed by adding ferrocene as standard at a 0.1 M concentration, corresponding to the average of the potentials of the cathodic and anodic peaks of the compound under study, after subtracting the average of the cathodic and anodic potentials observed for the standard Fc + / Fc redox couple, the values reported above are finally obtained.

10. The electroluminescent device according to any one of claims 1 to 3, wherein the first hole transport layer is arranged adjacent to the anode layer.

11. The electroluminescent device according to claim 10, additionally comprising a second hole transport layer, the second hole transport layer comprising a second hole transport matrix compound selected from covalent compounds comprising a conjugated system of at least 6 delocalized electrons; wherein the second hole transport layer is arranged between the first hole transport layer and the light-emitting layer.

12. A display device comprising at least one electroluminescent component according to any of claims 1 to 11.

13. An illumination device comprising at least one electroluminescent component according to any of claims 1 to 11.

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