WO2025119813A1

WO2025119813A1 - Materials for organic electroluminescent devices

Info

Publication number: WO2025119813A1
Application number: PCT/EP2024/084250
Authority: WO
Inventors: Rouven LINGE; Elvira Montenegro; Marie MEIJER
Original assignee: Merck Patent GmbH
Current assignee: Merck Patent GmbH
Priority date: 2023-12-06
Filing date: 2024-12-02
Publication date: 2025-06-12
Anticipated expiration: 2026-06-06

Abstract

The present application relates to an electronic device comprising a first electrode, a second electrode facing the first electrode, an interlayer between the first electrode and the second electrode comprising a hole transport region comprising at least two hole-transporting layers and an emitting layer comprising a fluorescent emitter.

Description

Materials for organic electroluminescent devices

The present application relates to an electronic device comprising a first electrode, a second electrode facing the first electrode, an interlayer between the first electrode and the second electrode comprising a hole transport region comprising at least two holetransporting layers and an emitting layer comprising a fluorescent emitter.

Electronic devices in the context of this application are understood to mean what are called organic electronic devices, which comprise organic semiconductor materials as functional materials. More particularly, these are understood to mean OLEDs (organic light-emitting diodes, organic electroluminescent devices). These are electronic devices which have one or more layers comprising organic compounds and emit light on application of electrical voltage. The construction and general principle of function of OLEDs are known to those skilled in the art.

In electronic devices, especially OLEDs, there is great interest in an improvement in the performance data, especially lifetime, efficiency, operating voltage and colour purity. In these aspects, it has not yet been possible to find any entirely satisfactory solution.

Hole-transporting layers in electronic devices, especially OLEDs, have a great influence on the abovementioned performance data of electronic devices. The hole-transporting layers may, as well as their hole-transporting function, also have an electron-blocking function, meaning that they block the passage of electrons from the emitting layer to the anode. In addition, the hole-transporting layers of the OLED preferably have suitable HOMO levels to efficiently enable the transport of the holes from the anode to the emitting layer.

Materials for hole-transporting layers that are known in the prior art are primarily amine compounds, especially triarylamine compounds. Examples of such triarylamine compounds are spirobifluoreneamines, fluoreneamines, indenofluoreneamines, phenanthreneamines, carbazoleamines, xantheneamines, spirodihydroacridineamines, biphenylamines and combinations of these structural elements having one or more amino groups, and the person skilled in the art is aware of further structure classes. It has now been found that, surprisingly, the combination of at least two hole-transporting layers as defined below with a light emitting layer comprising a fluorescent emitter leads to very good properties of the OLED, especially to very good efficiency and very good lifetime. The present application thus provides an electronic device comprising: a first electrode; a second electrode facing the first electrode; an interlayer between the first electrode and the second electrode and comprising an emission layer, wherein: the emission layer comprises a host material and a dopant, where the dopant is selected from fluorescent emitters, the interlayer further comprises a hole transport region between the emission layer and the first electrode, the hole transport region comprises a hole transport layer and a first auxiliary layer, where the first auxiliary layer is between the hole transport layer and the emission layer, the hole transport layer comprises a monoamine-based compound A of formula (I),

Formula (I) where the following applies to the symbols and indices occurring: Ar¹⁰, Ar¹¹, Ar¹² are on each occurrence, identically or differently, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may be substituted by one or more radicals R¹²; L¹⁰, L¹¹, L¹² are on each occurrence, identically or differently, a single bond, an aromatic having 6 to 30 aromatic ring atoms or heteroaromatic ring system having 5 to 30 aromatic ring atoms, which may be substituted by one or more radicals R¹²; R¹² stands on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CHO, CN, C(=O)Ar, P(=O)(Ar)2, S(=O)Ar, S(=O)2Ar, NO2, Si(R¹⁹)3, B(OR¹⁹)2, OSO2R¹⁹, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R¹⁹, where in each case one or more non-adjacent CH2 groups may be replaced by R¹⁹C=CR¹⁹, C≡C, Si(R¹⁹)2, Ge(R¹⁹)2, Sn(R¹⁹)2, C=O, C=S, C=Se, P(=O)(R¹⁹), SO, SO2, O or S and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R¹⁹; where two radicals R¹² may form an aliphatic, aromatic or heteroaromatic ring system together, which may be substituted by one or more radicals R¹⁹; R¹⁹ stands on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CHO, CN, C(=O)Ar, P(=O)(Ar)2, S(=O)Ar, S(=O)2Ar, NO2, Si(R´)3, B(OR´)2, OSO2R´, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R´, where in each case one or more non-adjacent CH2 groups may be replaced by R´C=CR´, C≡C, Si(R´)2, Ge(R´)2, Sn(R´)2, C=O, C=S, C=Se, P(=O)(R´), SO, SO2, O or S and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R´; where two radicals R¹⁹ may form an aliphatic, aromatic or heteroaromatic ring system together, which may be substituted by one or more radicals R´; Ar is, on each occurrence, identically or differently, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case also be substituted by one or more radicals R´; where R´ is as defined below, the first auxiliary layer comprises a compound B selected from compounds of formula (II), (III) or (IV),

where the following applies to the symbols and indices occurring: L²⁰, L²¹, L²² are on each occurrence, identically or differently, a single bond, an aromatic ring system having 6 to 30 aromatic ring atoms or heteroaromatic ring system having 5 to 30 aromatic ring atoms, which may be substituted by one or more radicals R²²; Ar²¹, Ar²² are on each occurrence, identically or differently, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may be substituted by one or more radicals R²²; X stands on each occurrence, identically or differently, for CR²⁰ or N; or X stands for C when it is bonded to the group L²⁰-N(L²¹Ar²¹)(L²²Ar²²); T²⁰, T²¹ are the same or different at each instance and are selected from single bond, O, S, NR²¹, and C(R²¹)2; R²⁰, R²¹, R²² stand on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CHO, CN, C(=O)Ar, P(=O)(Ar)2, S(=O)Ar, S(=O)2Ar, NO2, Si(R)3, B(OR)2, N(R)2, N(Ar)2, OSO2R, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R, where in each case one or more non- adjacent CH2 groups may be replaced by RC=CR, C≡C, Si(R)2, Ge(R)2, Sn(R)2, C=O, C=S, C=Se, P(=O)(R), SO, SO2, O or S and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R; where two radicals R²⁰, two radicals R²¹ and/or two radicals R²² may form an aliphatic, aromatic or heteroaromatic ring system together, which may be substituted by one or more radicals R; R stands on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CHO, CN, C(=O)Ar, P(=O)(Ar)2, S(=O)Ar, S(=O)2Ar, NO2, Si(R´)3, B(OR´)2, N(R´)2, N(Ar)2, OSO2R´, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R´, where in each case one or more non-adjacent CH₂ groups may be replaced by R´C=CR´, C≡C, Si(R´)₂, Ge(R´)₂, Sn(R´)₂, C=O, C=S, C=Se, P(=O)(R´), SO, SO₂, O or S and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO₂, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R´; where two radicals R may form an aliphatic, aromatic or heteroaromatic ring system together, which may be substituted by one or more radicals R´; R´ stands on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CN, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 20 C atoms or branched or cyclic alkyl, alkoxy or thioalkyl group having 3 to 20 C atoms, where in each case one or more non-adjacent CH2 groups may be replaced by SO, SO2, O, S and where one or more H atoms may be replaced by D, F, Cl, Br or I, or an aromatic ring system having 6 to 24 aromatic ring atoms or heteroaromatic ring system having 5 to 24 aromatic ring atoms; and where the following conditions apply: T1 (B) ≤ 2.65 eV FE)

│ ≤ 0.4 eV where: T₁ (HOST) is the lowest excitation triplet energy level of the host material in the emission layer as determined by quantum-chemical calculation; T₁ (FE) is the lowest excitation triplet energy level of the fluorescent emitter in the emission layer as determined by quantum-chemical calculation; and T₁ (B) is the lowest excitation triplet energy level of the compound B present in the first auxiliary layer as determined by quantum-chemical calculation. The definitions which follow are applicable to the chemical groups that are used in the present application. They are applicable unless any more specific definitions are given. An aryl group in the context of this invention is understood to mean either a single aromatic cycle, i.e. benzene, or a fused aromatic polycycle, for example naphthalene, phenanthrene or anthracene. A fused aromatic polycycle in the context of the present application consists of two or more single aromatic cycles fused to one another. Fusion between cycles is understood here to mean that the cycles share at least one edge with one another. An aryl group in the context of this invention contains 6 to 40 aromatic ring atoms. In addition, an aryl group does not contain any heteroatom as aromatic ring atom, but only carbon atoms. A heteroaryl group in the context of this invention is understood to mean either a single heteroaromatic cycle, for example pyridine, pyrimidine or thiophene, or a fused heteroaromatic polycycle, for example quinoline or carbazole. A fused heteroaromatic polycycle in the context of the present application consists of two or more single aromatic or heteroaromatic cycles that are fused to one another, where at least one of the aromatic and heteroaromatic cycles is a heteroaromatic cycle. Fusion between cycles is understood here to mean that the cycles share at least one edge with one another. A heteroaryl group in the context of this invention contains 5 to 40 aromatic ring atoms of which at least one is a heteroatom. The heteroatoms of the heteroaryl group are preferably selected from N, O and S. An aryl or heteroaryl group, each of which may be substituted by the abovementioned radicals, is especially understood to mean groups derived from benzene, naphthalene, anthracene, phenanthrene, pyrene, dihydropyrene, chrysene, perylene, triphenylene, fluoranthene, benzanthracene, benzophenanthrene, tetracene, pentacene, benzopyrene, furan, benzofuran, isobenzofuran, dibenzofuran, thiophene, benzothiophene, isobenzothiophene, dibenzothiophene, pyrrole, indole, isoindole, carbazole, pyridine, quinoline, isoquinoline, acridine, phenanthridine, benzo-5,6-quinoline, benzo-6,7-quinoline, benzo-7,8-quinoline, phenothiazine, phenoxazine, pyrazole, indazole, imidazole, benzimidazole, benzimidazolo[1,2-a]benzimidazole, naphthimidazole, phenanthrimidazole, pyridimidazole, pyrazinimidazole, quinoxalinimidazole, oxazole, benzoxazole, naphthoxazole, anthroxazole, phenanthroxazole, isoxazole, 1,2-thiazole, 1,3-thiazole, benzothiazole, pyridazine, benzopyridazine, pyrimidine, benzopyrimidine, quinoxaline, pyrazine, phenazine, naphthyridine, azacarbazole, benzocarboline, phenanthroline, 1,2,3- triazole, 1,2,4-triazole, benzotriazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole, 1,3,4-thiadiazole, 1,3,5-triazine, 1,2,4-triazine, 1,2,3-triazine, tetrazole, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine, 1,2,3,5-tetrazine, purine, pteridine, indolizine and benzothiadiazole. An aromatic ring system in the context of this invention is a system which does not necessarily contain solely aryl groups, but which may additionally contain one or more nonaromatic rings fused to at least one aryl group. These nonaromatic rings contain exclusively carbon atoms as ring atoms. Examples of groups covered by this definition are tetrahydronaphthalene, fluorene and spirobifluorene. In addition, the term "aromatic ring system" includes systems that consist of two or more aromatic ring systems joined to one another via single bonds, for example biphenyl, terphenyl, 7-phenyl-2-fluorenyl, quaterphenyl and 3,5-diphenyl-1-phenyl. An aromatic ring system in the context of this invention contains 6 to 40 carbon atoms and no heteroatoms in the ring system. The definition of "aromatic ring system" does not include heteroaryl groups. A heteroaromatic ring system conforms to the abovementioned definition of an aromatic ring system, except that it must contain at least one heteroatom as ring atom. As is the case for the aromatic ring system, the heteroaromatic ring system need not contain exclusively aryl groups and heteroaryl groups, but may additionally contain one or more nonaromatic rings fused to at least one aryl or heteroaryl group. The nonaromatic rings may contain exclusively carbon atoms as ring atoms, or they may additionally contain one or more heteroatoms, where the heteroatoms are preferably selected from N, O and S. One example of such a heteroaromatic ring system is benzopyranyl. In addition, the term "heteroaromatic ring system" is understood to mean systems that consist of two or more aromatic or heteroaromatic ring systems that are bonded to one another via single bonds, for example 4,6-diphenyl-2-triazinyl. A heteroaromatic ring system in the context of this invention contains 5 to 40 ring atoms selected from carbon and heteroatoms, where at least one of the ring atoms is a heteroatom. The heteroatoms of the heteroaromatic ring system are preferably selected from N, O and S. The terms "heteroaromatic ring system" and "aromatic ring system" as defined in the present application thus differ from one another in that an aromatic ring system cannot have a heteroatom as ring atom, whereas a heteroaromatic ring system must have at least one heteroatom as ring atom. This heteroatom may be present as a ring atom of a nonaromatic heterocyclic ring or as a ring atom of an aromatic heterocyclic ring. In accordance with the above definitions, any aryl group is covered by the term "aromatic ring system", and any heteroaryl group is covered by the term "heteroaromatic ring system". An aromatic ring system having 6 to 40 aromatic ring atoms or a heteroaromatic ring system having 5 to 40 aromatic ring atoms is especially understood to mean groups derived from the groups mentioned above under aryl groups and heteroaryl groups, and from biphenyl, terphenyl, quaterphenyl, fluorene, spirobifluorene, dihydrophenanthrene, dihydropyrene, tetrahydropyrene, indenofluorene, truxene, isotruxene, spirotruxene, spiroisotruxene, indenocarbazole, or from combinations of these groups. In the context of the present invention, a straight-chain alkyl group having 1 to 20 carbon atoms and a branched or cyclic alkyl group having 3 to 20 carbon atoms and an alkenyl or alkynyl group having 2 to 40 carbon atoms in which individual hydrogen atoms or CH₂ groups may also be substituted by the groups mentioned above in the definition of the radicals are preferably understood to mean the methyl, ethyl, n-propyl, i-propyl, n-butyl, i- butyl, s-butyl, t-butyl, 2-methylbutyl, n-pentyl, s-pentyl, cyclopentyl, neopentyl, n-hexyl, cyclohexyl, neohexyl, n-heptyl, cycloheptyl, n-octyl, cyclooctyl, 2-ethylhexyl, trifluoromethyl, pentafluoroethyl, 2,2,2-trifluoroethyl, ethenyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl, cyclooctenyl, ethynyl, propynyl, butynyl, pentynyl, hexynyl or octynyl radicals. An alkoxy or thioalkyl group having 1 to 20 carbon atoms in which individual hydrogen atoms or CH2 groups may also be substituted by the groups mentioned above in the definition of the radicals is preferably understood to mean methoxy, trifluoromethoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy, n-pentoxy, s-pentoxy, 2-methylbutoxy, n-hexoxy, cyclohexyloxy, n-heptoxy, cycloheptyloxy, n-octyloxy, cyclooctyloxy, 2-ethylhexyloxy, pentafluoroethoxy, 2,2,2-trifluoroethoxy, methylthio, ethylthio, n-propylthio, i-propylthio, n-butylthio, i-butylthio, s-butylthio, t-butylthio, n- pentylthio, s-pentylthio, n-hexylthio, cyclohexylthio, n-heptylthio, cycloheptylthio, n-octylthio, cyclooctylthio, 2-ethylhexylthio, trifluoromethylthio, pentafluoroethylthio, 2,2,2- trifluoroethylthio, ethenylthio, propenylthio, butenylthio, pentenylthio, cyclopentenylthio, hexenylthio, cyclohexenylthio, heptenylthio, cycloheptenylthio, octenylthio, cyclooctenylthio, ethynylthio, propynylthio, butynylthio, pentynylthio, hexynylthio, heptynylthio or octynylthio. The wording that two or more radicals together may form a ring, in the context of the present application, shall be understood to mean, inter alia, that the two radicals are joined to one another by a chemical bond. In addition, however, the abovementioned wording shall also be understood to mean that, if one of the two radicals is hydrogen, the second radical binds to the position to which the hydrogen atom was bonded, forming a ring. Preferably, the energy of the highest occupied molecular orbital of the monoamine-based compound A, HOMO (A), in the hole-transport layer is: -5.30 ≤ HOMO (A) ≤ -5.00 eV More preferably: -5.25 ≤ HOMO (A) ≤ -5.05 eV Preferably, the energy of the highest occupied molecular orbital of the compound B present in the first auxiliary layer, HOMO (B), is: -5.50 ≤ HOMO (B) ≤ -5.10 eV More preferably: -5.40 ≤ HOMO (B) ≤ -5.20 eV The HOMO and LUMO energies are determined by quantum-chemical calculation as described below. It is preferred that: │T1 (FE) – T1 (B)│ ≤ 0.3 eV It is even more preferred that: │T1 (FE) – T1 (B)│ ≤ 0.25 eV Preferably, T1 (FE) ≥ 2.30 eV. More preferably, T1 (FE) ≥ 2.40 eV. Even more preferably, T1 (FE) ≥ 2.50 eV. Preferably, T1(B) ≤ 2.60 eV, more preferably T1(B) ≤ 2.57 eV, even more preferably, T1(B) ≤ 2.55 eV. As, montioned above, the energy levels of molecular orbitals, like the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), and of the lowest triplet state T1 or of the lowest excited singlet state S1 of materials are determined via quantum-chemical calculations. For all quantum-chemical calculations, the Gaussian program package is used (Gaussian16). The singlet ground state geometries are optimized at the B3LYP/6-31G(d) level of theory. Subsequently, TD-DFT singlet and triplet excitation energies (vertical transitions) are computed using the optimized ground state geometry and the same method (B3LYP/6-31G(d)). Default settings for SCF and geometry convergence are employed. For structures containing heavy metal atoms the calculation is carried out analogously to the above-described method for the organic substances, with the difference that the "LanL2DZ" base set is used for the metal atom and the "6-31G(d)" base set is used for the ligands. The energy calculation gives the HOMO energy level HEh or LUMO energy level LEh in hartree units. The HOMO and LUMO energy levels in electron volts calibrated with reference to cyclic voltammetry measurements are determined therefrom as follows: HOMO(eV) = (HEh*0.90603) - 0.84836 LUMO(eV) = (LEh*0.99687) - 0.72445 For the purposes of this application, these values are to be regarded as HOMO and LUMO energy levels respectively of the materials. The lowest triplet state T1 is defined as the energy of the triplet state having the lowest energy which arises from the quantum-chemical calculation described. The lowest excited singlet state S1 is defined as the energy of the excited singlet state having the lowest energy which arises from the quantum-chemical calculation described. The method described herein is independent of the software package used and always gives the same results. Examples of frequently used programs for this purpose are "Gaussian16" (Gaussian Inc.) and Q Chem 4.1 (Q Chem, Inc.). In accordance with the present invention, the hole transport layer comprises a monoamine- based compound A of formula (I). The term monoamine means that the compound A contains only one amino group. Preferably, the hole transport layer is an undoped layer, which means that the hole transport layer is not p-doped, i.e. the material of the hole transport layer is not doped with p-dopants. Furthermore, it is preferred that the compound A does not contain any carbazole group. Preferably, the monoamine-based compound A is selected from compound of formula (I-1),

Formula (I-1) where the following applies to the symbols and indices occurring: E¹ is equal to C(R¹¹)₂ or equal to

where the dashed lines represent the bonds emanating from the group E¹; T¹, T² are the same or different at each instance and are selected from single bond, O, S, NR¹³, and C(R¹³)2; R¹⁰, R¹¹, R¹³ stand on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CHO, CN, C(=O)Ar, P(=O)(Ar)2, S(=O)Ar, S(=O)2Ar, NO2, Si(R¹⁹)3, B(OR¹⁹)2, OSO2R¹⁹, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R¹⁹, where in each case one or more non-adjacent CH2 groups may be replaced by R¹⁹C=CR¹⁹, C≡C, Si(R¹⁹)2, Ge(R¹⁹)2, Sn(R¹⁹)2, C=O, C=S, C=Se, P(=O)(R¹⁹), SO, SO2, O or S and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R¹⁹; where two or more radicals R¹⁰, two or more radicals R¹¹ or two or more radicals R¹³ an aliphatic, aromatic or heteroaromatic ring system together, which may be substituted by one or more radicals R¹⁹; m is equal to 0, 1, 2 or 3; n is equal to 0, 1, 2, 3 or 4; and the symbols Ar¹⁰, Ar¹¹, L¹⁰, L¹¹, L¹² and R¹⁹ have the same meaning as above. More preferably, the monoamine-based compound A is selected from compounds of formula (I-2),

Formula (I-2) where: E¹⁰ is equal to C(R¹¹)₂ or equal to

, where the dashed lines represent the bonds emanating from the group E¹⁰; and where the symbols and indices R¹⁰, Ar¹⁰, Ar¹¹, L¹⁰, L¹¹, L¹², m and n have the same meaning as above. Even more preferably, the monoamine-based compound A is selected from compound of formula (I-3A) or (I-3B),

Formula (I-3B) where the symbols and indices R¹⁰, R¹¹, Ar¹⁰, Ar¹¹, L¹⁰, L¹¹, L¹², m and n have the same meaning as above. Particularly preferably, the monoamine-based compound A is selected from compounds of formula (I-4A) or (I-4B),

s Formula (I-4B) where A² is equal to C(R¹¹)2, O, S or equal to

, where the dashed lines represent the bonds emanating from the group A²; and where R¹⁴ stands on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CHO, CN, C(=O)Ar, P(=O)(Ar)2, S(=O)Ar, S(=O)2Ar, NO2, Si(R¹⁹)3, B(OR¹⁹)2, OSO2R¹⁹, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R¹⁹, where in each case one or more non-adjacent CH2 groups may be replaced by R¹⁹C=CR¹⁹, C≡C, Si(R¹⁹)2, Ge(R¹⁹)2, Sn(R¹⁹)2, C=O, C=S, C=Se, P(=O)(R¹⁹), SO, SO2, O or S and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R¹⁹; where two or more radicals R¹⁴ may be linked to one another and form a substituted or unsubstituted aliphatic, aromatic ring or heteroaromatic ring, which may be substituted by one or more radicals R¹⁹; s is 0, 1, 2, 3 or 4; t is 0, 1, 2 or 3; and where the other symbols and indices have the same meaning as above. More particularly preferably, the monoamine-based compound A is selected from compounds of formula (I-5A) or (I-5B),

Formula (I-5A) Formula (I-5B) where the symbols and indices have the same meaning as above. Even more particularly preferably, the monoamine-based compound A is selected from compounds of formulae (I-6A) to (I-6D),

Formula (I-6A) Formula (I-6B)

Formula (I-6C) Formula (I-6D) where the symbols and indices have the same meaning as above. Preferably, in formulae (I-6A) and (I-6B), the index m is equal to 0 and the index n is equal to 1 or 2. Preferably, in formulae (I-6C) and (I-6D), the index m is equal to 0 and the index n is, identically or differently equal to 0 or 1, where it is preferred that at least one index n is ≥ 1. In accordance with a preferred embodiment, the monoamine-based compound A is selected from compounds of formulae (I-6E) to (I-6R),

Formula (I-6G) Formula (I-6H)

Formula (I-6K) Formula (I-6L)

Formula (I-6O) Formula (I-6P)

Formula (I-6Q) Formula (I-6R) where R¹⁰ stands on each occurrence, identically or differently, for a straight-chain alkyl group having 1 to 40 C atoms or branched or a cyclic alkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R¹⁹, where one or more H atoms may be replaced by D, or an aromatic ring system having 6 to 18 aromatic ring atoms, which may in each case be substituted by one or more radicals R¹⁹; and where the other symbols have the same meaning as above and where the free position in the compounds of formulae (I-6E) to (I-6R) might be substituted by a Deuterium. Preferably, the formulae (I-6E) to (I6-R) are selected from the formulae (I-6E-1) to (I-6R-1),

Formula (I-6G-1) Formula (I-6H-1)

Formula (I-6K-1) Formula (I-6L-1)

Formula (I-6O-1) Formula (I-6P-1)

where R¹⁰ stands on each occurrence, identically or differently, for a straight-chain alkyl group having 1 to 40 C atoms or branched or a cyclic alkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R¹⁹, where one or more H atoms may be replaced by D, or an aromatic ring system having 6 to 18 aromatic ring atoms, which may in each case be substituted by one or more radicals R¹⁹; and where the other symbols have the same meaning as above and where the free position in the compounds of formulae (I-6E-1) to (I-6R-1) might be substituted by a Deuterium. Preferably, in formulae (I-6A) to (I-6D), (I-6E) to (I-6R) and (I-6E-1) to (I-6R-1), the fluorene group bonded to L¹⁰, or to N if L¹⁰ is a single bond, is bonded to the structure on the 2- position of the fluorene as follows:

where the dashed bon represent the bond position to L¹⁰, or to N if L¹⁰ is a single bond. In a preferred embodiment of the present invention, L¹⁰, L¹¹, L¹² are, identically or differently, a single bond or are selected aromatic ring systems having 6 to 30 aromatic ring atoms, which may be substituted by one or more radicals R¹². More preferably, L¹⁰, L¹¹, L¹² are, identically or differently, a single bond or are selected from the group consisting of benzene, biphenyl, terphenyl, naphthyl, fluorenyl, indenofluorenyl, spirobifluorenyl, dibenzofuranyl and dibenzothiophenyl, which may each be substituted by one or more radicals R¹². More preferably, L¹⁰, L¹¹, L¹² are, identically or differently, a single bond or are selected from the group consisting of benzene, biphenyl, terphenyl, naphthyl, dibenzofuranyl and dibenzothiophenyl, which may be substituted by one or more radicals R¹². Even more preferably, L¹⁰, L¹¹, L¹² stand for a single bond or benzene, which may be substituted by one or more radicals R¹². Preferably, Ar¹¹ is on each occurrence, identically or differently, an aromatic ring system having 6 to 30, preferably 6 to 24 aromatic ring atoms or heteroaromatic ring system having 5 to 30, preferably 5 to 24 aromatic ring atoms, which may be substituted by one or more radicals R¹². More preferably, Ar¹¹ is selected from the group consisting of phenyl, biphenyl, terphenyl, quarterphenyl, naphthyl, fluorenyl, especially 9,9'-dimethylfluorenyl and 9,9'- diphenylfluorenyl, benzofluorenyl, spirobifluorenyl, indenofluorenyl, dibenzofuranyl, dibenzothiophenyl, benzofuranyl, benzothiophenyl, indolyl, quinolinyl, pyridyl, pyrimidyl, pyrazinyl, pyridazinyl and triazinyl, and combinations of two or three of these groups, which are each optionally substituted by one or more radicals R¹². Particularly preferably, Ar¹¹ is selected from the group consisting of phenyl, biphenyl, terphenyl, quarterphenyl, naphthyl, fluorenyl, especially 9,9'-dimethylfluorenyl and 9,9'- diphenylfluorenyl, benzofluorenyl, spirobifluorenyl, indenofluorenyl, dibenzofuranyl, dibenzothiophenyl, benzofuranyl, benzothiophenyl, benzofused dibenzofuranyl, benzofused dibenzothiophenyl, naphthyl-substituted phenyl, fluorenyl-substituted phenyl, spirobifluorenyl-substituted phenyl, dibenzofuranyl-substituted phenyl, dibenzothiophenyl- substituted phenyl, pyridyl-substituted phenyl, pyrimidyl-substituted phenyl, and triazinyl- substituted phenyl, each of which may optionally be substituted by one or more radicals R¹². Example of very suitable groups Ar¹¹ are the groups (Ar¹-1) to (Ar¹-238) depicted in the following table:

where the dotted line represents the bond to the nitrogen atom, and where the groups may bear one or more substituents R¹² other than H at the positions shown as being unsubstituted, and preferably bear H or D at the positions shown as being unsubstituted. Among, the groups Ar¹-1 to Ar¹-237, following groups are preferred: Ar¹-1, Ar¹-2, Ar¹-4, Ar¹-7, Ar¹-52, Ar¹-63, Ar¹-64, Ar¹-65, Ar¹-66, Ar¹-107, Ar¹-108, Ar¹-109, Ar¹-110, Ar¹-141, Ar¹-142, Ar¹-176, Ar¹-177, Ar¹-178, Ar¹-181, Ar¹-182, Ar¹-183, Ar¹-184, Ar¹- 185, Ar¹-186, Ar¹-187, Ar¹-210, Ar¹-229, Ar¹-230, Ar¹-231. In accordance with a very particularly preferred embodiment, Ar¹¹ is selected from the group of formula (Ar¹¹-1):

Formula (Ar¹¹-1) Where the dotted line represents the bond to the nitrogen atom, and: u is 0, 1, 2, 3 or 4; v is 0, 1, 2, 3, 4 or 5. Preferably, R¹⁰, R¹¹, R¹², R¹³, R¹⁴ stand on each occurrence, identically or differently, for H, D, F, CN, Si(R¹⁹)₃, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40, preferably 1 to 30, more preferably 1 to 20, even more preferably 1 to 10 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl group having 3 to 40, preferably 3 to 30, more preferably 3 to 20, even more preferably 3 to 10 C atoms, each of which may be substituted by one or more radicals R¹⁹, where in each case one or more non-adjacent CH₂ groups may be replaced by O or S and where one or more H atoms may be replaced by D or F, an aromatic ring system having 6 to 40, preferably 6 to 30, more preferably 6 to 24, even more preferably 6 to 18 aromatic ring atoms or heteroaromatic ring system having 5 to 40, preferably 5 to 30, more preferably 5 to 24, even more preferably 5 to 18 aromatic ring atoms, which may in each case be substituted by one or more radicals R¹⁹; where two radicals R¹⁰, two radicals R¹¹, two radicals R¹², two radicals R¹³ and/or two radicals R¹⁴ may form an aliphatic, aromatic or heteroaromatic ring system together, which may be substituted by one or more radicals R¹⁹. More preferably, R¹¹ stands on each occurrence, identically or differently, for H, D, a straight-chain alkyl group having 1 to 10, preferably 1 to 5, more preferably 1 to 3 C atoms, which may be substituted by one or more radicals R¹⁹, where one or more H atoms may be replaced by D or F, an aromatic ring system having 6 to 18, preferably 6 to 12 aromatic ring atoms, which may in each case be substituted by one or more radicals R¹⁹. Very preferably, R¹¹ is a methyl group, where one or more H atoms may be replaced by D or F. Preferably, R¹⁹ stands on each occurrence, identically or differently, for H, D, F, CN, Si(R^´)3, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40, preferably 1 to 30, more preferably 1 to 20, even more preferably 1 to 10 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl group having 3 to 40, preferably 3 to 30, more preferably 3 to 20, even more preferably 3 to 10 C atoms, each of which may be substituted by one or more radicals R^´, where in each case one or more non-adjacent CH2 groups may be replaced by O or S and where one or more H atoms may be replaced by D or F, an aromatic ring system having 6 to 40, preferably 6 to 30, more preferably 6 to 24, even more preferably 6 to 18 aromatic ring atoms or heteroaromatic ring system having 5 to 40, preferably 5 to 30, more preferably 5 to 24, even more preferably 5 to 18 aromatic ring atoms, which may in each case be substituted by one or more radicals R´; where two radicals R¹⁹ may form an aliphatic, aromatic or heteroaromatic ring system together, which may be substituted by one or more radicals R´. Preferably, Ar is, on each occurrence, identically or differently, an aromatic ring system having 6 to 30, preferably 6 to 24, more preferably 6 to 18 aromatic ring atoms or heteroaromatic ring system having 5 to 30, preferably 5 to 24, more preferably 5 to 18 aromatic ring atoms, which may in each case also be substituted by one or more radicals R´. Preferably, R´ stands on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CN, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 20 C atoms or branched or cyclic alkyl, alkoxy or thioalkyl group having 3 to 20 C atoms, where in each case one or more non-adjacent CH₂ groups may be replaced by SO, SO₂, O, S and where one or more H atoms may be replaced by D, F, Cl, Br or I, or an aromatic ring system having 6 to 24 aromatic ring atoms or heteroaromatic ring system having 5 to 24 aromatic ring atoms. In accordance with a preferred embodiment, the monoamine-based compound A is a deuterated compound. The term “deuterated compound” refers here to a compound in which deuterium is present in at least 100 times the natural abundance level. A higher deuteration degree than in nature can be achieved by using building blocks which have been previously enriched with deuterium via a deuteration method or by submitting a compound to a deuteration method. In accordance with the present invention, the deuteration degree corresponds to the number of deuterium atoms in a compound on the total number of deuterium atoms and protium atoms in the compound in %, as follows: Deuteration degree (%) = (ND * 100) / (NP + ND) where: ND is the number of deuterium atoms in the compound NP is the number of deuterium and protium atoms in the compounds Unless specified otherwise, the term hydrogen in the present invention design the protium isotope of hydrogen, which accounts for more that 99.98% of the natural occurring hydrogen in the oceans. Preferably, the compound A has a deuteration degree higher than 20%, 40%, 60% or 80%. Examples of the compounds A are depicted in the following table:

Processes for synthesis of the compounds of the formula (I) are known in the prior art, especially in the publications cited in the table below:

Preferably, the compound B in the first auxiliary layer is selected from the compounds of formulae (II), (III) and (IV), where at least one group selected from the groups L²⁰, Ar²¹ and Ar²² stands for a group of formula (C-1) or (C-2):

where one symbol selected from L³⁰, L³¹ or Z is bonded to an adjacent group in formula (II), (III) or (IV) if the group of formula (C-1) or (C-2) is Ar²¹ or Ar²², or two symbols selected from L³⁰, L³¹ or Z are bonded to an adjacent group in formula (II), (III) or (IV) if the group of formula (C-1) or (C-2) is L²⁰, and L³⁰, L³¹ are on each occurrence, identically or differently, a single bond, an aromatic ring system having 6 to 30, preferably 6 to18 aromatic ring atoms or heteroaromatic ring system having 5 to 30, preferbaly 5 to 18 aromatic ring atoms, which may be substituted by one or more radicals R²²; where R²² has the same meaning as above; T³⁰ stands for O, S or C(R²¹)2; where R²¹ has the same meaning as above; preferably, T³⁰ stands for O; Z stands on each occurrence, identically or differently, for CR²³, N or C when it is bonded to an adjacent group in formulae (II), (III) or (IV); where two groups Z may also form a condensed ring; R²³ stands on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CHO, CN, C(=O)Ar, P(=O)(Ar)2, S(=O)Ar, S(=O)2Ar, NO2, Si(R)3, B(OR)2, N(R)2, N(Ar)2, OSO2R, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R, where in each case one or more non-adjacent CH2 groups may be replaced by RC=CR, C≡C, Si(R)2, Ge(R)2, Sn(R)2, C=O, C=S, C=Se, P(=O)(R), SO, SO2, O or S and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R; where two radicals R²³ may form an aliphatic, aromatic or heteroaromatic ring system together, which may be substituted by one or more radicals R; where R has the same definition as above, and r stands for 0, 1 or 2. More preferably, the compound B in the first auxiliary layer is selected from the compounds of formulae (II), (III) and (IV), where at least one group selected from the groups L²⁰, Ar²¹ and Ar²² stands for a group of formula (C-3) or (C-4):

where one symbol Z is bonded to an adjacent group in formula (II), (III) or (IV) if the group of formula (C-1) is Ar²¹ or Ar²², or two symbols Z are bonded to an adjacent group in formula (II), (III) or (IV) if the group of formula (C-1) is L²⁰, where Z and the index r have the same meaning as in claim 3, and p, q stand, identically or differently, for 0, 1, 2 or 3. As mentioned above, two groups Z may form a condensed ring. Preferably, when two groups Z form a condensed ring, then the condensed ring is a ring of formula (Ring-1):

where the dashed bonds indicate the position of the adjacent ring and Z¹ stands on each occurrence, identically or differently, for CR²³, where C²³ is as defined above. Examples of groups of formulae (C-3) and (C-4), where two groups Z form a condensed ring together are the groups of formulae (C-5) and (C-6) below:

where the symbols and indices have the same meaning as above. Preferably, the compound B in the first auxiliary layer is selected from the compounds of formulae (II-1) to (II-4), (III-1) to (III-4) and (IV-1) to (IV-4),

where the symbols and indices X, Z, R²¹, T²⁰, T²¹, T³⁰, L²⁰, L²¹, L²², Ar²¹, Ar²², p, q and r have the same meaning as above, and where X^1, X², X³, X⁴ stand on each occurrence, identically or differently, for CR²⁰ or stand for C when bonded to the adjacent group depicted in formulae (II-1) to (II-4) and (III-1) to (III-4). Preferably, the adjacent group depicted in formulae (II-1) to (II-4) and (III-1) to (III-4), which is adjacent to the ring comprising X^1, X², X³, X⁴, is bonded to X¹ or X⁴. Preferably, T²⁰, T²¹ are the same or different at each instance and are selected from single bond, O and C(R²¹)₂, more preferably from single bond and O. Even more preferably, T²⁰, T²¹ stand for a single bond. More preferably, the compound B in the first auxiliary layer is selected from the compounds of formulae (II-1A) to (II-4A), (III-1A) to (III-4A) and (IV-1A) to (IV-4A),

where the symbols and indices X, Z, R²¹, T³⁰, L²⁰, L²¹, L²², Ar²¹, Ar²², p, q and r have the same meaning as above, and where X^1, X², X³, X⁴ stand on each occurrence, identically or differently, for CR²⁰ or stand for C when bonded to the adjacent group depicted in formulae (II-1) to (II-4) and (III-1) to (III-4). Preferably, the adjacent group depicted in formulae (II-1A) to (II-4A) and (III-1A) to (III-4A), which is adjacent to the ring comprising X^1, X², X³, X⁴, is bonded to X¹ or X⁴. In accordance with a preferred embodiment, the index p is equal to 1, 2 or 3 and the index q is equal to 0. In accordance with another preferred embodiment, the index p is equal to 0 and the index q is equal to 1, 2 or 3. Preferably, in formulae (II-1), (III-1), (IV-1), (II-1A), (III-1A) and (IV-1A), the group Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z ^p Z Z ^r Z ^q is selected from the groups of formulae (CA-1) to (CA-10),

where the dashed bond represents the bond to the adjacent group in formulae (II-1), (III-1), (IV-1), (II-1A), (III-1A) and (IV-1A), and where Z has the same meaning as above. More preferably, in formulae (II-1), (III-1), (IV-1), (II-1A), (III-1A) and (IV-1A), the group Z Z

^q is selected from the groups of formulae (CA-1A) to (CA-16A),

where the dashed bond represents the bond to the adjacent group in formulae (II-1), (III-1), (IV-1), (II-1A), (III-1A) and (IV-1A), and where Z has the same meaning as above. Preferably, in formulae (II-2), (III-2), (IV-2), (II-2A), (III-2A) and (IV-2A), the group

is selected from the groups of formulae (CB-1) to (CB-11),

where the dashed bonds represent the bonds to the adjacent groups in formulae (II-2), (III- 2), (IV-2), (II-2A), (III-2A) and (IV-2A), and where Z has the same meaning as above. More preferably, in formulae (II-2), (III-2), (IV-2), (II-2A), (III-2A) and (IV-2A), the group is selected from the groups of formulae (CB-1A) to (CB-11A),

where the dashed bonds represent the bonds to the adjacent groups in formulae (II-2), (III- 2), (IV-2), (II-2A), (III-2A) and (IV-2A), and where Z has the same meaning as above. Preferably, in formulae (II-3), (III-3), (IV-3), (II-3A), (III-3A) and (IV-3A), the group is selected from the groups of formulae (CC-1) to (CC-8),

where the dashed bond represents the bond to the adjacent group in formulae (II-3), (III-3), (IV-3), (II-3A), (III-3A) and (IV-3A), and where Z and T³⁰ have the same meaning as above. More preferably, in formulae (II-3), (III-3), (IV-3), (II-3A), (III-3A) and (IV-3A), the group

is selected from the groups of formulae (CC-1A) to (CC-24A),

where the dashed bond represents the bond to the adjacent group in formulae (II-3), (III-3), (IV-3), (II-3A), (III-3A) and (IV-3A), and where Z and T³⁰ have the same meaning as above. Preferably, in formulae (II-4), (III-4), (IV-4), (II-4A), (III-4A) and (IV-4A), the group

is selected from the groups of formulae (CD-1) to (CD-8),

where the dashed bonds represent the bond to the adjacent groups in formulae (II-4), (III- 4), (IV-4), (II-4A), (III-4A) and (IV-4A), and the symbols Z and T³⁰ have the same meaning as above. More preferably, in formulae (II-4), (III-4), (IV-4), (II-4A), (III-4A) and (IV-4A), the group

is selected from the groups of formulae (CD-1A) to (CD-28A),

where the dashed bonds represent the bond to the adjacent groups in formulae (II-4), (III- 4), (IV-4), (II-4A), (III-4A) and (IV-4A), and the symbols Z and T³⁰ have the same meaning as above. In accordance with a preferred embodiment, the compound B in the first auxiliary layer is selected from the compounds of formulae (II-1B), (II-3B), (III-1B), (III-3B), (IV-1B) and (IV- 3B),

where the symbols and indices X, Z, R²¹, T²⁰, T²¹, T³⁰, L²⁰, L²¹, L²², Ar²¹, Ar²² and p have the same meaning as above, and where X^1, X², X³, X⁴ stand on each occurrence, identically or differently, for CR²⁰ or stand for C when bonded to the adjacent group depicted in formulae (II-1B), (II-3B), (III-1B), (III- 3B), (IV-1B) and (IV-3B). Preferably, the adjacent group depicted in formulae (II-1B), (II-3B), (III-1B), (III-3B), (IV-1B) and (IV-3B), which is adjacent to the ring comprising X^1, X², X³, X⁴, is bonded to X¹ or X⁴. In accordance with a very preferred embodiment, the compound B in the first auxiliary layer is selected from the compounds of formulae (II-1B), (III-1B) and (IV-1B). In a preferred embodiment of the present invention, L²⁰, L²¹, L²² are, identically or differently, a single bond or are selected from aromatic ring systems having 6 to 20, preferably 6 to 12 aromatic ring atoms or heteroaromatic ring system having 5 to 20, preferably 5 to 12 aromatic ring atoms, which may be substituted by one or more radicals R²². More preferably, L²⁰, L²¹, L²² are, identically or differently, a single bond or are selected from the group consisting of benzene, biphenyl, terphenyl, naphthyl, fluorenyl, indenofluorenyl, spirobifluorenyl, dibenzofuranyl and dibenzothiophenyl, and carbazolyl, which may each be substituted by one or more radicals R²². More preferably, L²⁰, L²¹, L²² are, identically or differently, a single bond or are selected from the group consisting of benzene, biphenyl, terphenyl, naphthyl, dibenzofuranyl and dibenzothiophenyl, and carbazolyl, which may be substituted by one or more radicals R²². Even more preferably, L²⁰, L²¹, L²² stand for a single bond or benzene, biphenyl or terphenyl, which may be substituted by one or more radicals R²². In accordance with a preferred embodiment, the compound B in the first auxiliary layer is selected from the compounds of formulae (II-1), (II-3), (III-1), (III-3), (IV-1), (IV-3), (II-1A), (II- 3A), (III-1A), (III-3A), (IV-1A), (IV-3A), (II-1B), (II-3B), (III-1B), (III-3B), (IV-1B) and (IV-3B), where the group L²⁰ stands for a single bond. In accordance with another preferred embodiment, the compound B in the first auxiliary layer is selected from the compounds of formulae (II-1), (II-3), (III-1), (III-3), (IV-1), (IV-3), (II-1A), (II-3A), (III-1A), (III-3A), (IV-1A), (IV-3A), (II-1B), (II-3B), (III-1B), (III-3B), (IV-1B) and (IV-3B), where the group L²⁰ stands for benzene, biphenyl or terphenyl, which may be substituted by one or more radicals R²². In this case, L²⁰ stands more preferably for group of formula (L20-1), (L20-2) or (L20-3),

where the groups of formulae (L20-1) to (L20-3) may be substituted by one or more radicals R²² at the free positions (meaning positions bearing an H). Preferably, the free positions in formulae (L20-1) to (L20-3) bear an Hydrogen or a Deuterium atom. Preferably, Ar²¹ in compound B stands for an aromatic ring system having 6 to 30, preferably 6 to 24 aromatic ring atoms or heteroaromatic ring system having 5 to 30, preferably 5 to 24 aromatic ring atoms, which may be substituted by one or more radicals R²². More preferably, Ar²¹ in compound B is selected from monovalent groups derived from benzene, biphenyl, terphenyl, quaterphenyl, naphthalene, fluorene, especially 9,9'- dimethylfluorene and 9,9'-diphenylfluorene, benzofluorene, spirobifluorene, indenofluorene, indenocarbazole, dibenzofuran, dibenzothiophene, benzocarbazole, carbazole, benzofuran, benzothiophene, indole, quinoline, pyridine, pyrimidine, pyrazine, pyridazine and triazine, where the monovalent groups may each be substituted by one or more R²² radicals. Particularly preferably, Ar²¹ is compound B is selected from phenyl, biphenyl, terphenyl, quaterphenyl, naphthyl, fluorenyl, especially 9,9'-dimethylfluorenyl and 9,9'- diphenylfluorenyl, benzofluorenyl, spirobifluorenyl, indenofluorenyl, indenocarbazolyl, dibenzofuranyl, dibenzothiophenyl, carbazolyl, benzofuranyl, benzothiophenyl, benzofused dibenzofuranyl, benzofused dibenzothiophenyl, naphthyl-substituted phenyl, fluorenyl- substituted phenyl, spirobifluorenyl-substituted phenyl, dibenzofuranyl-substituted phenyl, dibenzothiophenyl-substituted phenyl, carbazolyl-substituted phenyl, pyridyl-substituted phenyl, pyrimidyl-substituted phenyl, and triazinyl-substituted phenyl, where the groups mentioned may each be substituted by one or more R²² radicals. Preferred Ar²¹ groups correspond to the groups Ar²-1 to Ar²-252 shown below:

Ar²-23 Ar²-24 Ar²-25 Ar²-26 Ar²-27 Ar²-28 Ar²-29 Ar²-30 Ar²-31

Ar²-41 Ar²-42 Ar²-43 Ar²-44 Ar²-45 Ar²-46

where the dotted line represents the bond to the nitrogen atom, and where the groups may bear one or more substituents R²² other than H at the positions shown as being unsubstituted, and preferably bear H or D at the positions shown as being unsubstituted. Among, the groups Ar²-1 to Ar²-252, following groups are preferred: Ar²-1 to Ar²-7, Ar²-24, Ar²-39, Ar²-40, Ar²-48 to Ar²-66, Ar²-78 to Ar²-80, Ar²-82, Ar²-83, Ar²- 112, Ar²-113, Ar²-134, Ar²-139 to Ar²-145, Ar²-202 to Ar²-210. In accordance with a preferred embodiment, Ar²¹ stands for a group of formula (C-3-1) or (C-4-1):

where the dashed bond indicates the position of the bond to the adjacent nitrogen atom, and where the symbols Z, T³⁰ and the indices p, q, r have the same meaning as above. In case p is equal to 0, then the corresponding group is absent and the next group, namely the group between the bracket with the index r is bonded to the adjacent nitrogen atom as follows:

where the dashed bond indicates the position of the bond to the adjacent nitrogen atom, and where the symbols Z, T³⁰ and the indices q, r have the same meaning as above. Preferably, R²⁰, R²¹, R²², R²³ stand on each occurrence, identically or differently, for H, D, F, CN, Si(R)3, N(Ar)2, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40, preferably 1 to 30, more preferably 1 to 20, even more preferably 1 to 10 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl group having 3 to 40, preferably 3 to 30, more preferably 3 to 20, even more preferably 3 to 10 C atoms, each of which may be substituted by one or more radicals R, where in each case one or more non-adjacent CH2 groups may be replaced by O or S and where one or more H atoms may be replaced by D or F, an aromatic ring system having 6 to 40, preferably 6 to 30, more preferably 6 to 24 aromatic ring atoms or heteroaromatic ring system having 5 to 40, preferably 5 to 30, more preferably 5 to 24 aromatic ring atoms, which may in each case be substituted by one or more radicals R; where two radicals R²⁰, two radicals R²¹, two radicals R²² and/or two radicals R²² may form an aliphatic, aromatic or heteroaromatic ring system together, which may be substituted by one or more radicals R. More preferably, R²⁰, R²¹, R²², R²³ stand on each occurrence, identically or differently, for H, D, F, CN, Si(R)₃, a straight-chain alkyl group having 1 to 10 C atoms or branched or a cyclic alkyl group having 3 to 10 C atoms, each of which may be substituted by one or more radicals R, where one or more H atoms may be replaced by D or F, an aromatic ring system having 6 to 18 aromatic ring atoms or heteroaromatic ring system having 5 to 18 aromatic ring atoms, which may in each case be substituted by one or more radicals R; where two radicals R²⁰, two radicals R²¹, two radicals R²² and/or two radicals R²² may form an aliphatic, aromatic or heteroaromatic ring system together, which may be substituted by one or more radicals R. Preferably, R stands on each occurrence, identically or differently, for H, D, F, CN, Si(R´)3, N(Ar)2, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40, preferably 1 to 30, more preferably 1 to 20, even more preferably 1 to 10 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl group having 3 to 40, preferably 3 to 30, more preferably 3 to 20, even more preferably 3 to 10 C atoms, each of which may be substituted by one or more radicals R´, where in each case one or more non-adjacent CH2 groups may be replaced by O or S and where one or more H atoms may be replaced by D or F, an aromatic ring system having 6 to 40, preferably 6 to 30, more preferably 6 to 24 aromatic ring atoms or heteroaromatic ring system having 5 to 40, preferably 5 to 30, more preferably 5 to 24 aromatic ring atoms, which may in each case be substituted by one or more radicals R^´; where two radicals R may form an aliphatic, aromatic or heteroaromatic ring system together, which may be substituted by one or more radicals R´. In accordance with a preferred embodiment, the compound B is a deuterated compound. Examples of the suitable compounds B are depicted in the table below:

Processes for synthesis of the compound of the formula (II), (III) and (IV) are known in the prior art, especially in the publications cited in the table below: ,

0 Preferred combinations of compound A in the hole transport layer and compound B in the first auxiliary layer of the electronic device according to the present invention are disclosed in the table below:

In accordance with a preferred embodiment, the hole transport region further comprises a hole injection layer between the first electrode and the hole transport layer comprising the compound A. In the present application, the hole transport layer comprising the compound A is called HTL and the hole injection layer between the first electrode and the hole transport layer HTL is called HIL. Preferably, the hole transport layer HTL consists of a compound A as defined above. Preferably, the hole injection layer is in direct contact with the first electrode, and more preferably, additionally in direct contact with the hole transport layer HTL. The hole injection layer HIL preferably conforms to one of the following embodiments: a) it contains a triarylamine and at least one p-dopant; or b) it contains a single electron- deficient material (electron acceptor). In a preferred embodiment of embodiment b), the electron-deficient material is a hexaazatriphenylene derivative as described in US 2007/0092755. It is further preferable that the hole injection layer HIL contains a monoamine-based compound of formula (I), preferably comprising a 4-substituted spirobifluorene group, especially a compound having a spirobifluorene group 4-substituted by an amino group or an amino group bonded via an aromatic system. In a preferred embodiment, the hole injection layer HIL comprises a monoamine-based compound of formula (I) as the main component, which is doped by a p-dopant. p-Dopants according to the present application are organic electron acceptor compounds. p-Dopants used are preferably those organic electron acceptor compounds capable of oxidizing one or more of the other compounds in the p-doped layer. Particularly preferred as p-dopants are quinodimethane compounds, azaindenofluorenediones, azaphenalenes, azatriphenylenes, I₂, metal halides, preferably transition metal halides, metal oxides, preferably metal oxides comprising at least one transition metal or a metal from main group 3, and transition metal complexes, preferably complexes of Cu, Co, Ni, Pd and Pt with ligands containing at least one oxygen atom as binding site. Preference is further given to transition metal oxides as dopants, preferably oxides of rhenium, molybdenum and tungsten, more preferably Re₂O₇, MoO₃, WO₃ and ReO3. Still further preference is given to complexes of bismuth in the (III) oxidation state, more particularly bismuth(III) complexes with electron-deficient ligands, more particularly carboxylate ligands. The p-dopants are preferably in substantially homogeneous distribution in the p-doped layers. This can be achieved, for example, by co-evaporation of the p-dopant and the hole transport material matrix. The p-dopant is preferably present in a proportion of 1% to 10% in the p-doped layer. Preferred p-dopants are especially the compounds shown in WO2021/104749 on pages 99- 100 as (D-1) to (D-14). Preferably, the hole transport layer HTL is in direct contact with the first auxiliary layer. It is also preferred that the first auxiliary layer is in direct contact with the emission layer. Preferably, the first auxiliary layer consists of a compound B as described above. In accordance with a preferred embodiment, the hole transport layer HTL is in direct contact with the first auxiliary layer and the first auxiliary layer is in direct contact with the emission layer. In accordance with another preferred embodiment, the hole transport region further comprises a second auxiliary layer between the hole transport layer HTL and the first auxiliary layer. Preferably, the hole transport layer HTL is in direct contact with the second auxiliary layer, the second auxiliary layer is in direct contact with the first auxiliary layer and the first auxiliary layer is in direct contact with the emission layer. The second auxiliary layer preferably comprises a triarylamine compound. The hole transport region comprises in this sequence (from the first electrode to the emission layer): - optionally a hole injection layer HIL, - a hole transport layer HTL comprising a compound A as defined above, - optionally a second auxiliary layer AUX2, - a first auxiliary layer AUX1 comprising a compound B as defined above. Layers HIL, HTL, AUX1 and AUX2 are all hole-transporting layers. Hole-transporting layers are understood here to mean all layers disposed between anode and emission layer, preferably hole injection layers, hole transport layers, and electron blocker layers. A hole injection layer is understood here to mean a layer that preferably directly adjoins the anode. A hole transport layer is understood here to mean a layer which is between the anode and emission layer but preferably does not directly adjoin the anode, and preferably does not directly adjoin the emitting layer either. An electron blocker layer is understood here to mean a layer which is between the anode and emission layer and directly adjoins the emission layer and preferably has a high-energy LUMO and hence prevents electrons from exiting from the emitting layer. The hole transport layer HTL is preferably a hole transport layer. The layer HTL preferably has a thickness of 50 to 150 nm, more preferably of 70 to 120 nm. The first auxiliary layer AUX1 is preferably an electron blocker layer. When the second auxiliary layer AUX2 is present, then AUX2 and AUX1 form the electron blocker layer. The layer AUX1 preferably has a thickness of 5 to 50 nm, more preferably of 5 to 30 nm. Besides the layers HIL, HTL, AUX1 and AUX2, the hole tansport region may comprise further hole transport layers. Preferably, the first electrode is an anode and the second electrode is a cathode. Preferred cathodes of the electronic device are metals having a low work function, metal alloys or multilayer structures composed of various metals, for example alkaline earth metals, alkali metals, main group metals or lanthanoids (e.g. Ca, Ba, Mg, Al, In, Mg, Yb, Sm, etc.). Additionally suitable are alloys composed of an alkali metal or alkaline earth metal and silver, for example an alloy composed of magnesium and silver. In the case of multilayer structures, in addition to the metals mentioned, it is also possible to use further metals having a relatively high work function, for example Ag or Al, in which case combinations of the metals such as Ca/Ag, Mg/Ag or Ba/Ag, for example, are generally used. It may also be preferable to introduce a thin interlayer of a material having a high dielectric constant between a metallic cathode and the organic semiconductor. Examples of useful materials for this purpose are alkali metal or alkaline earth metal fluorides, but also the corresponding oxides or carbonates (e.g. LiF, Li₂O, BaF₂, MgO, NaF, CsF, Cs₂CO₃, etc.). It is also possible to use lithium quinolinate (LiQ) for this purpose. The layer thickness of this layer is preferably between 0.5 and 5 nm. Preferred anodes are materials having a high work function. Preferably, the anode has a work function of greater than 4.5 eV versus vacuum. Firstly, metals having a high redox potential are suitable for this purpose, for example Ag, Pt or Au. Secondly, metal/metal oxide electrodes (e.g. Al/Ni/NiOx, Al/PtOx) may also be preferred. For some applications, at least one of the electrodes has to be transparent or partly transparent in order to enable either the irradiation of the organic material (organic solar cell) or the emission of light (OLED, O-LASER). Preferred anode materials here are conductive mixed metal oxides. Particular preference is given to indium tin oxide (ITO) or indium zinc oxide (IZO). Preference is further given to conductive doped organic materials, especially conductive doped polymers. In addition, the anode may also consist of two or more layers, for example of an inner layer of ITO and an outer layer of a metal oxide, preferably tungsten oxide, molybdenum oxide or vanadium oxide. The emission layer comprises a host and a fluorescent emitter. Examples of fluorescent emitters are aromatic anthracenamines, aromatic anthracenediamines, aromatic pyrenamines, aromatic pyrenediamines, aromatic chrysenamines or aromatic chrysenediamines. An aromatic anthracenamine is taken to mean a compound in which one diarylamino group is bonded directly to an anthracene group, preferably in the 9-position. An aromatic anthracenediamine is taken to mean a com- pound in which two diarylamino groups are bonded directly to an anthracene group, preferably in the 9,10-position. Aromatic pyrenamines, pyrenediamines, chrysenamines and chrysenediamines are defined analogously thereto, where the diarylamino groups are preferably bonded to the pyrene in the 1-position or in the 1,6-position. Further fluorescent emitters are indenofluorenamines or indenofluorenediamines, for example in accordance with WO 2006/108497 or WO 2006/122630, benzoindenofluorenamines or benzoindenofluorenediamines, for example in accordance with WO 2008/006449, and dibenzoindenofluorenamines or dibenzoindenofluorenediamines, for example in accordance with WO 2007/140847, and the indenofluorene derivatives containing con- densed aryl groups which are disclosed in WO 2010/012328. Still further examples of fluorescent emitters are benzanthracene derivatives as disclosed in WO 2015/158409, anthracene derivatives as disclosed in WO 2017/036573, fluorene dimers connected via heteroaryl groups like in WO 2016/150544 or phenoxazine derivatives as disclosed in WO 2017/028940 and WO 2017/028941. Further examples of fluorescent emitters are pyren- arylamines as disclosed in WO 2012/048780 and WO 2013/185871, benzoindenofluoren- amines as disclosed in WO 2014/037077, benzofluorenamines as disclosed in WO 2014/106522 and indenofluorenes as disclosed in WO 2014/111269 or WO 2017/036574, WO 2018/007421. Futher examples of fluorescent emitters are the emitters comprising dibenzofuran or indenodibenzofuran moieties as disclosed in WO 2018/095888, WO 2018/095940, WO 2019/076789, WO 2019/170572 as well as in WO 2020/043657, WO 2020/043646 and WO/2020/043640, boron derivatives as disclosed, for example, in WO 2015/102118, CN108409769, CN107266484, WO2017195669, US2018069182 as well as in WO 2020/208051, WO2021/058406, and WO 2021/094269. Preferred fluorescent emitters are those described in WO 2021/090932, WO 2020/054676, WO 2018/212169, US 10,249,832, WO 2021/014001, where T1 (FE) ≥ 2.30 eV. Preferably, the fluorescent emitter has an emission peak wavelength between 420-550 nm. More preferably, the fluorescent emitter is a blue fluorescent emitter and the emission layer of the device is a blue-fluorescing emitting layer. Preferably, the fluorescent emitter has a full width at half maximum FWHM ≤ 50 nm, preferably FWHM ≤ 40 nmm, more preferably FWHM ≤ 30 nm. The optical bandwidth of a light source is measured by its full width at half maximum (FWHM). The term FWHM refers to the width of an optical signal at half its maximum intensity. FWHM of the fluorescent emitter is determined here at the peak emission wavelength ^max, which corresponds to the wavelength of the first maximum of the emission spectrum. To determine the peak emission wavelength of the fluorescent emitter, the fluorescent emitter is dissolved in toluene and a photoluminescent spectrum is obtained using a fluorescence spectrometer. More specifically, a concentration of 1 mg/100 mL is used. The solution is excited in a fluorescence spectrometer, for example Hitachi F-4500. Typically, the first maximum is also the global maximum of the spectrum. To determine the FWHM of the fluorescent emitter, the wavelengths values at half the maximum of the peak emission wavelength, are subtracted. Preferably, the fluorescent emitter is selected from compounds of formula (F-1):

Ar³⁰, Ar³¹, Ar³² stand on each occurrence, identically or differently, for a substituted or unsubstituted aromatic ring system having 6 to 30, preferably 6 to 18, more preferably 6 to 12 aromatic ring atoms or heteroaromatic ring system having 5 to 30, preferably 5 to 18, more preferably 5 to 13, even more preferably 5 to 7 aromatic ring atoms, which may be substituted by one or more radicals R³⁰; Y³⁰ stands for B or N; Y³¹, Y³², Y³³ stand on each occurrence, identically or differently, for O, S, C(R⁰)2, C=O, C=S, C=NR⁰, C=C(R⁰)2, Si(R⁰)2, BR⁰, NR⁰, PR⁰, SO2, SeO2 or a chemical bond, with the proviso that if Y³⁰ is B, then at least one of the groups Y³¹, Y³², Y³³ stands for NR⁰ and if Y³⁰ is N, then at least one of the groups Y³¹, Y³², Y³³ stands for BR⁰; R⁰ stands on each occurrence, identically or differently, for H, D, F, a straight-chain alkyl group having 1 to 20 C atoms or branched or a cyclic alkyl group having 3 to 20, each of which may be substituted by one or more radicals R, where in each case one or more non- adjacent CH2 groups may be replaced by O or S and where one or more H atoms may be replaced by D or F, or an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring systems having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R, where two adjacent radicals R⁰, may form an aliphatic, aromatic or heteroaromatic ring system together, which may be substituted by one or more radicals R; R³⁰ stands on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CHO, CN, C(=O)Ar, P(=O)(Ar)2, S(=O)Ar, S(=O)2Ar, NO2, Si(R)3, B(OR)2, OSO2R, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R, where in each case one or more non-adjacent CH2 groups may be replaced by RC=CR, C≡C, Si(R)2, Ge(R)2, Sn(R)2, C=O, C=S, C=Se, P(=O)(R), SO, SO2, O or S and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R; where two radicals R³⁰ may form an aliphatic, aromatic or heteroaromatic ring system together, which may be substituted by one or more radicals R; R has the same meaning as above; and q is 0 or 1. Preferably, the compounds of formula (F-1) are selected from the compounds of formulae (F-2) to (F-7) as depicted below:

(F-2) (F-3)

Where Y³⁴ stands on each occurrence, identically or differently, for O, S, C(R⁰)2, C=O, C=S, C=NR⁰, C=C(R⁰)2, Si(R⁰)2, BR⁰, NR⁰, PR⁰, SO2, SeO2, preferably for O, S, C(R⁰)2, BR⁰ or NR⁰; a, b, c stand, identically or differently for 0, 1, 2 or 3; d stands for 0, 1, 2, 3 or 4. Examples of suitable fluorescent emitters are depicted in the table below:

In accordance with a preferred embodiment, the emission layer is a classical fluorescent- emitting layer comprising a host material, also called matrix material, and a dopant, where the dopant is selected from fluorescent emitters. Suitable host materials for fluorescent emitters are selected from the classes of the oligoarylenes (e.g.2,2’,7,7’-tetraphenylspirobifluorene), especially the oligoarylenes containing fused aromatic groups, the oligoarylenevinylenes, the polypodal metal complexes, the hole-conducting compounds, the electron-conducting compounds, especially ketones, phosphine oxides and sulfoxides; the atropisomers, the boronic acid derivatives or the benzanthracenes. Particularly preferred host materials are selected from the classes of the oligoarylenes comprising naphthalene, anthracene, benzanthracene and/or pyrene or atropisomers of these compounds, the oligoarylenevinylenes, the ketones, the phosphine oxides and the sulfoxides. Very particularly preferred host materials are selected from the classes of the oligoarylenes comprising anthracene, benzanthracene, benzophenanthrene and/or pyrene or atropisomers of these compounds. An oligoarylene in the context of this invention shall be understood to mean a compound in which at least three aryl or arylene groups are bonded to one another. Preferably, the following condition is fulfilled: │T1 (Host) – T1 (B)│ ≤ 1.0 eV. The electronic device preferably contains a single emitting layer. In this case, the emitting layer is preferably selected from blue-fluorescing emitting layers. In a preferred embodiment, the electronic device is part of an arrangement consisting of three or more, preferably three, electronic devices, of which one device contains a blue- emitting layer, one device a green-emitting layer, and one device a red-emitting layer (called an RGB side-by-side arrangement). The electronic device according to the application is preferably the blue-emitting device in the arrangement. The electronic devices in the arrangement are preferably arranged alongside one another. In a particularly preferred embodiment, the arrangement contains a first device according to the application containing a hole transport layer HTL, a first auxiliary layer AUX1 and a blue-fluorescing emitting layer, and a second device according to the application containing a green-phosphorescing or green-fluorescing emitting layer. There is preferably a third electronic device in the arrangement that contains a red-emitting layer, preferably a red- phosphorescing layer. Preferably, the hole transport layer HTL is identical, especially containing the same material, in the first and second devices according to the application in the arrangement, and preferably also in the third electronic device of the arrangement. A particularly preferred example of such an arrangement 100 containing three electronic devices, one of which is an electronic devices according to the application, is shown in Figure 1. In this figure, 100a is an electronic device, preferably the above-mentioned first device according to the application, 100b is an electronic device, preferably the above- mentioned second device, and 100c is a red-emitting electronic device. Layer 101c is the anode of the red-emitting electronic device, layer 101b is the anode of the second device according to the application, and layer 101a is the anode of the first device according to the application, layer 102 is a hole injection layer, preferably HIL as described above, in the form of a common layer, layer 103 is the hole transport layer HTL, designed as a common layer, layer 105c is a red-emitting layer, layer 105b is a green-emitting layer, layer 105a is a blue light-emitting layer, layer 106 is a hole blocker layer, designed as a common layer, layer 107 is an electron transport layer, designed as a common layer, layer 108 is an electron injection layer, designed as a common layer, layer 109c is the cathode of the red- emitting electronic device, layer 109b is the cathode of the second device according to the application, and layer 109a is the cathode of the first device according to the application. Layers 104a is the first auxiliary layer AUX1. Layers 104c is an auxiliary layer of the red- emitting electronic device, layer 104b is an auxiliary layer of the green-emitting electronic device. What is meant by a “common layer” in the above details is that the layer contains the same material in all three layers of the arrangement. This preferably means that the layer is identical in all three devices in the arrangement, i.e. extends as one layer across all three devices in the arrangement. Another particularly preferred example of such an arrangement 200 containing three electronic devices, one of which is an electronic devices according to the application, is shown in Figure 2. In this figure, 200a is an electronic device, preferably the above- mentioned first device according to the application, 200b is an electronic device, preferably the above-mentioned second device, and 200c is a red-emitting electronic device. Layer 201c is the anode of the red-emitting electronic device, layer 201b is the anode of the second device according to the application, and layer 201a is the anode of the first device according to the application, layer 202 is a hole injection layer, preferably HIL as described above, in the form of a common layer, layer 203 is the hole transport layer HTL, designed as a common layer, layer 205c is a red-emitting layer, layer 205b is a green-emitting layer, layer 205a is a blue light-emitting layer, layer 206 is a hole blocker layer, designed as a common layer, layer 207 is an electron transport layer, designed as a common layer, layer 208 is an electron injection layer, designed as a common layer, layer 209c is the cathode of the red-emitting electronic device, layer 209b is the cathode of the second device according to the application, and layer 209a is the cathode of the first device according to the application. Layers 204a is the first auxiliary layer AUX1. Layers 204c is an auxiliary layer of the red-emitting electronic device, layer 204b is an auxiliary layer of the green-emitting electronic device. Layers 204´a is the second auxiliary layer AUX2. Layers 204´c is a second auxiliary layer of the red-emitting electronic device, layer 204´b is a second auxiliary layer of the green-emitting electronic device. The electronic devices of the arrangement shown in Figure 1 and in Figure 2 may contain additional layers not shown in the figure. In an alternative, likewise preferred embodiment, the electronic device contains multiple emitting layers arranged in succession, each having different emission maxima between 380 nm and 750 nm. In other words, different emitting compounds used in each of the multiple emitting layers fluoresce or phosphoresce and emit blue, green, yellow, orange or red light. In a preferred embodiment, the electronic device contains three emitting layers in succession in a stack, of which one in each case exhibits blue emission, one green emission, and one orange or red, preferably red, emission. Preferably, in this case, the blue-emitting layer is a fluorescent layer, and the green-emitting layer is a phosphorescent layer, and the red-emitting layer is a phosphorescent layer. An emitting layer of the electronic device may also contain systems comprising a plurality of matrix materials (mixed matrix systems) and/or a plurality of emitting compounds. When the electronic device contains a phosphorescent emitting layer, it is preferable that this layer contains two or more, preferably exactly two, different matrix materials. Mixed matrix systems preferably comprise two or three different matrix materials, more preferably two different matrix materials. Preferably, in this case, one of the two materials is a material having hole-transporting properties and the other material is a material having electron-transporting properties. It is further preferable when one of the materials is selected from compounds having a large energy differential between HOMO and LUMO (wide-bandgap materials). The two different matrix materials may be present in a ratio of 1:50 to 1:1, preferably 1:20 to 1:1, more preferably 1:10 to 1:1 and most preferably 1:4 to 1:1. The desired electron-transporting and hole-transporting properties of the mixed matrix components may, however, also be combined mainly or entirely in a single mixed matrix component, in which case the further mixed matrix component(s) fulfil(s) other functions. Suitable mixtures of host materials for use in the device according to the invention are obtained by combination of the compounds E1 to E21 with the compounds H1 to H12 as described below. The following table shows said mixtures. The first mixture M1, for example, is a combination of compound E1 with H1.

As mentioned above, the electronic device may contain multiple emitting layers and, in this case, the blue-emitting layer is a preferably a fluorescent layer comprising at least one fluorescent emitter and one host as described above, whereas the green-emitting layer and the red-emitting layer are preferably phosphorescent layers comprising at least one phosphorescent emitter and one host or matrix material (host ans matrix material are used synonymously in the present application) as described below. Phosphorescent emitters: The term "phosphorescent emitters" typically encompasses compounds where the emission of light is effected through a spin-forbidden transition, for example a transition from an excited triplet state or a state having a higher spin quantum number, for example a quintet state. Suitable phosphorescent emitters are especially compounds which, when suitably excited, emit light, preferably in the visible region, and also contain at least one atom of atomic number greater than 20, preferably greater than 38, and less than 84, more preferably greater than 56 and less than 80. Preference is given to using, as phosphorescent emitters, compounds containing copper, molybdenum, tungsten, rhenium, ruthenium, osmium, rhodium, iridium, palladium, platinum, silver, gold or europium, especially compounds containing iridium, platinum or copper. In the context of the present invention, all luminescent iridium, platinum or copper complexes are considered to be phosphorescent compounds. In general, all phosphorescent complexes as used for phosphorescent OLEDs according to the prior art and as known to those skilled in the art in the field of organic electroluminescent devices are suitable for use in the devices according to the application. Matrix materials for phosphorescent emitters: Preferred matrix materials for phosphorescent emitters are aromatic ketones, aromatic phosphine oxides or aromatic sulfoxides or sulfones, triarylamines, carbazole derivatives, e.g. CBP (N,N-biscarbazolylbiphenyl), indolocarbazole derivatives, indenocarbazole derivatives, azacarbazole derivatives, bipolar matrix materials, silanes, azaboroles or boronic esters, triazine derivatives, zinc complexes, diazasilole or tetraazasilole derivatives, diazaphosphole derivatives, bridged carbazole derivatives, triphenylene derivatives, or lactams. Apart from cathode, anode, emitting layer, layer HTL1 and layer HTL2, the electronic device may comprise further layers. These are selected, for example, from in each case one or more hole injection layers, hole transport layers, hole blocker layers, electron transport layers, electron injection layers, electron blocker layers, exciton blocker layers, interlayers, charge generation layers and/or organic or inorganic p/n junctions. However, it should be pointed out that not every one of these layers need necessarily be present and the choice of layers always depends on the compounds used and especially also on whether the device is a fluorescent or phosphorescent electroluminescent device. The sequence of layers in the electronic device is preferably as follows: - first electrode, preferably anode - hole injection layer HIL, preferably p-doped - Hole transport layer HTL - optionally further hole transport layer(s), for example a second auxiliary layer AUX2 - first auxiliary layer AUX1 - emission layer - optionally hole blocker layer - electron transport layer - electron injection layer - second electrode, preferably cathode. It is not obligatory for all the layers mentioned to be present, and/or further layers may additionally be present. Compounds that are preferably used in further hole-transporting layers of the device according to the application, like the second auxiliary layer AUX2, are indenofluoreneamine derivatives, amine derivatives, hexaazatriphenylene derivatives, amine derivatives with fused aromatic systems, monobenzoindenofluoreneamines, dibenzoindenofluoreneamines, spirobifluoreneamines, fluoreneamines, spirodibenzopyranamines, dihydroacridine derivatives, spirodibenzofurans and spirodibenzothiophenes, phenanthrenediarylamines, spirotribenzotropolones, spirobifluorenes having meta-phenyldiamine groups, spirobisacridines, xanthenediarylamines, and 9,10-dihydroanthracene spiro compounds having diarylamino groups. The electronic device preferably contains at least one electron transport layer. In addition, the electronic device preferably contains at least one electron injection layer. The electron injection layer preferably directly adjoins the cathode. In a preferred embodiment, the electron transport layer contains a triazine derivative and lithium quinolinate. In a preferred embodiment, the electron injection layer contains a triazine derivative and lithium quinolinate. In a particularly preferred embodiment, the electron transport layer and/or the electron injection layer, most preferably the electron transport layer and the electron injection layer, contain a triazine derivative and lithium quinolinate (LiQ). In a preferred embodiment, the electronic device contains at least one hole blocker layer. This preferably has hole-blocking and electron-transporting properties, and directly adjoins this emitting layer on the cathode side in a device containing a single emitting layer. In a device comprising multiple emitting layers that are arranged in succession, the hole blocker layer directly adjoins those of the multiple emitting layers that are closest to the cathode on the cathode side. Suitable electron-transporting materials are, for example, the compounds disclosed in Y. Shirota et al., Chem. Rev.2007, 107(4), 953-1010, or other materials used in these layers according to the prior art. Materials used for the electron transport layer may be any materials that are used as electron transport materials in the electron transport layer according to the prior art. Especially suitable are aluminium complexes, for example Alq3, zirconium complexes, for example Zrq4, lithium complexes, for example Liq, benzimidazole derivatives, triazine derivatives, pyrimidine derivatives, pyridine derivatives, pyrazine derivatives, quinoxaline derivatives, quinoline derivatives, oxadiazole derivatives, aromatic ketones, lactams, boranes, diazaphosphole derivatives and phosphine oxide derivatives. In a preferred embodiment, the electronic device is characterized in that one or more layers are applied by a sublimation process. In this case, the materials are applied by vapour deposition in vacuum sublimation systems at an initial pressure of less than 10^-5 mbar, preferably less than 10^-6 mbar. In this case, however, it is also possible that the initial pressure is even lower, for example less than 10^-7 mbar. Preference is likewise given to an electronic device, characterized in that one or more layers are coated by the OVPD (organic vapour phase deposition) method or with the aid of a carrier gas sublimation. In this case, the materials are applied at a pressure between 10^-5 mbar and 1 bar. A special case of this method is the OVJP (organic vapour jet printing) method, in which the materials are applied directly by a nozzle and thus structured (for example M. S. Arnold et al., Appl. Phys. Lett.2008, 92, 053301). Preference is additionally given to an electronic device, characterized in that one or more layers are produced from solution, for example by spin-coating, or by any printing method, for example screen printing, flexographic printing, nozzle printing or offset printing, but more preferably LITI (light-induced thermal imaging, thermal transfer printing) or inkjet printing. It is further preferable that an electronic device according to the application is produced by applying one or more layers from solution and one or more layers by a sublimation method. After application of the layers, according to the use, the device is structured, contact- connected and finally sealed, in order to rule out damaging effects of water and air. The electronic device may be used in displays, as light source in lighting applications, and as light source in medical and/or cosmetic applications. Examples Production of the OLEDs 1) General production process for the OLEDs and characterization of the OLEDs Glass plaques which have been coated with structured ITO (indium tin oxide) in a thickness of 50 nm are the substrates to which the OLEDs are applied. The OLEDs basically have the following layer structure: substrate / hole injection layer (HIL) / hole transport layer (HTL) / electron blocker layer (EBL) / emission layer (EML) / electron transport layer, optionally with second layer (ETL) / electron injection layer (EIL) and finally a cathode. The cathode is formed by an aluminum layer of thickness 100 nm. The exact structure of the OLEDs can be found in the tables which follow. The materials used for production of the OLEDs are shown in a table below. All materials are applied by thermal vapor deposition in a vacuum chamber. In this case, the emission layer consists of at least one matrix material (host material) and an emitting dopant which is added to the matrix material(s) in a particular proportion by volume by co- evaporation. Details given in such a form as H:SEB (3%) mean here that the material H is present in the layer in a proportion by volume of 97% and SEB in a proportion of 3%. In an analogous manner, the electron transport layer and the hole injection layer also consist of a mixture of two materials. The structures of the materials that are used in the OLEDs are shown in Table 1. The OLEDs are characterized in a standard manner. For this purpose, the electroluminescence spectra, the external quantum efficiency (EQE, measured in %) as a function of the luminance, calculated from current-voltage-luminance characteristics assuming Lambertian radiation characteristics, and the lifetime are determined. The parameter EQE @ 10 mA/cm² refers to the external quantum efficiency which is attained at 10 mA/cm². The lifetime LT is defined as the time after which the luminance drops from the starting luminance to a certain proportion in the course of operation with constant current density. An LT90 number means here that the lifetime reported corresponds to the time after which the luminance has dropped to 90% of its starting value. The figure @60 mA/cm² means here that the lifetime in question is measured at 60 mA/cm². The figure Rel LT90 @ 60 mA/cm2 (%) means the LT90@60 mA/cm² in relation to the given comparative example CE1 in percentage.

The compounds C1 to C3 and EBM1 to EBM11 have been synthesised according to the processes as described in WO2020159266, WO2022154282, KR2021123664, WO2017/144150 and WO2013120577. 2) Inventive OLEDs containing a compound A in the HTL and a compound B in the EBL of blue-fluorescing OLEDs The device architecture of OLEDs with SEB1 as dopant are shown in the following table: ess

The lifetime improvement of the OLEDs, which can be achieved with SEB1 as dopant, is shown in the following tables 3 to 5:

OLEDs of the examples E1 to E11, which comprise a material A in the HTL and a material B as defined above in the EBL have improved properties in terms of lifetime in comparison with the comparative OLED in CE1 to CE3, while the efficiency of the inventive and comparative OLEDs is similar. Further examples are disclosed in Table 4: ess

OLEDs of the examples E12 to E39, which comprise a material A in the HTL and a material B as defined above in the EBL have improved properties in terms of lifetime in comparison with comparative OLEDs of the comparative examples CE4 to CE11, while the efficiency of the inventive and comparative OLEDs is similar.

Claims

Claims 1. An electronic device comprising: a first electrode; a second electrode facing the first electrode; an interlayer between the first electrode and the second electrode and comprising an emission layer, wherein: the emission layer comprises a host material and a dopant, where the dopant is selected from fluorescent emitters, the interlayer further comprises a hole transport region between the emission layer and the first electrode, the hole transport region comprises a hole transport layer and a first auxiliary layer, where the first auxiliary layer is between the hole transport layer and the emission layer, the hole transport layer comprises a monoamine-based compound A of formula (I),

Formula (I) where the following applies to the symbols and indices occurring: Ar¹⁰, Ar¹¹, Ar¹² are on each occurrence, identically or differently, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may be substituted by one or more radicals R¹²; L¹⁰, L¹¹, L¹² are on each occurrence, identically or differently, a single bond, an aromatic having 6 to 30 aromatic ring atoms or heteroaromatic ring system having 5 to 30 aromatic ring atoms, which may be substituted by one or more radicals R¹²; R¹² stands on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CHO, CN, C(=O)Ar, P(=O)(Ar)2, S(=O)Ar, S(=O)2Ar, NO2, Si(R¹⁹)3, B(OR¹⁹)2, OSO2R¹⁹, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R¹⁹, where in each case one or more non-adjacent CH2 groups may be replaced by R¹⁹C=CR¹⁹, C≡C, Si(R¹⁹)2, Ge(R¹⁹)2, Sn(R¹⁹)2, C=O, C=S, C=Se, P(=O)(R¹⁹), SO, SO2, O or S and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R¹⁹; where two radicals R¹² may form an aliphatic, aromatic or heteroaromatic ring system together, which may be substituted by one or more radicals R¹⁹; R¹⁹ stands on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CHO, CN, C(=O)Ar, P(=O)(Ar)2, S(=O)Ar, S(=O)2Ar, NO2, Si(R´)3, B(OR´)2, OSO2R´, a straight- chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R´, where in each case one or more non-adjacent CH2 groups may be replaced by R´C=CR´, C≡C, Si(R´)2, Ge(R´)2, Sn(R´)2, C=O, C=S, C=Se, P(=O)(R´), SO, SO2, O or S and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO₂, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R´; where two radicals R¹⁹ may form an aliphatic, aromatic or heteroaromatic ring system together, which may be substituted by one or more radicals R´; Ar is, on each occurrence, identically or differently, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case also be substituted by one or more radicals R´; the first auxiliary layer comprises a compound B selected from compounds of formula (II), (III) or (IV)

where the following applies to the symbols and indices occurring: L²⁰, L²¹, L²² are on each occurrence, identically or differently, a single bond, an aromatic ring system having 6 to 30 aromatic ring atoms or heteroaromatic ring system having 5 to 30 aromatic ring atoms, which may be substituted by one or more radicals R²²; Ar²¹, Ar²² are on each occurrence, identically or differently, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may be substituted by one or more radicals R²²; X stands on each occurrence, identically or differently, for CR²⁰ or N; or X stands for C when it is bonded to the group L²⁰-N(L²¹Ar²¹)(L²²Ar²²); T²⁰, T²¹ are the same or different at each instance and are selected from single bond, O, S, NR²¹, and C(R²¹)2; R²⁰, R²¹, R²² stand on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CHO, CN, C(=O)Ar, P(=O)(Ar)2, S(=O)Ar, S(=O)2Ar, NO2, Si(R)3, B(OR)2, N(R)2, N(Ar)2, OSO2R, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R, where in each case one or more non- adjacent CH2 groups may be replaced by RC=CR, C≡C, Si(R)2, Ge(R)2, Sn(R)2, C=O, C=S, C=Se, P(=O)(R), SO, SO2, O or S and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R; where two radicals R²⁰, two radicals R²¹ and/or two radicals R²² may form an aliphatic, aromatic or heteroaromatic ring system together, which may be substituted by one or more radicals R; R stands on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CHO, CN, C(=O)Ar, P(=O)(Ar)₂, S(=O)Ar, S(=O)₂Ar, NO₂, Si(R´)₃, B(OR´)₂, N(R´)₂, N(Ar)₂, OSO₂R´, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R´, where in each case one or more non-adjacent CH₂ groups may be replaced by R´C=CR´, C≡C, Si(R´)₂, Ge(R´)₂, Sn(R´)₂, C=O, C=S, C=Se, P(=O)(R´), SO, SO₂, O or S and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO₂, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R´; where two radicals R may form an aliphatic, aromatic or heteroaromatic ring system together, which may be substituted by one or more radicals R´; R´ stands on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CN, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 20 C atoms or branched or cyclic alkyl, alkoxy or thioalkyl group having 3 to 20 C atoms, where in each case one or more non-adjacent CH2 groups may be replaced by SO, SO2, O, S and where one or more H atoms may be replaced by D, F, Cl, Br or I, or an aromatic ring system having 6 to 24 aromatic ring atoms or heteroaromatic ring system having 5 to 24 aromatic ring atoms; and where the following conditions apply: T₁ (B) ≤ 2.65 eV FE)

│ ≤ 0.4 eV where: T₁ (HOST) is the lowest excitation triplet energy level of the host material in the emission layer as determined by quantum-chemical calculation; T₁ (FE) is the lowest excitation triplet energy level of the fluorescent emitter in the emission layer as determined by quantum-chemical calculation; and T₁ (B) is the lowest excitation triplet energy level of the compound B present in the first auxiliary layer as determined by quantum-chemical calculation.

2. An electronic device according to claim 1, characterized in that T₁ (B) ≤ 2.60 eV.

3. An electronic device according to claim 1 or 2, characterized in that the first auxiliary layer comprises a compound B, where at least one group selected from the groups L²⁰, Ar²¹ and Ar²², in formulae (II), (III) and (IV), stands for a group of formula (C-1) or (C-2): L³¹

F^{ormula (C-1)}

where one symbol selected from L³⁰, L³¹ or Z is bonded to an adjacent group in formula (II), (III) or (IV) if the group of formula (C-1) or (C-2) is Ar²¹ or Ar²², or two symbols selected from L³⁰, L³¹ or Z are bonded to an adjacent group in formula (II), (III) or (IV) if the group of formula (C-1) or (C-2) is L²⁰, and L³⁰, L³¹ are on each occurrence, identically or differently, a single bond, an aromatic ring system having 6 to 30 aromatic ring atoms or heteroaromatic ring system having 5 to 30 aromatic ring atoms, which may be substituted by one or more radicals R²²; where R²² has the same meaning as in claim 1; T³⁰ stands for O, S or C(R²¹)₂; where R²¹ has the same meaning as in claim 1; Z stands on each occurrence, identically or differently, for CR²³, N or C when it is bonded to an adjacent group in formulae (II), (III) or (IV); where two groups Z may also form a condensed ring; R²³ stands on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CHO, CN, C(=O)Ar, P(=O)(Ar)₂, S(=O)Ar, S(=O)₂Ar, NO₂, Si(R)₃, B(OR)₂, N(R)₂, N(Ar)₂, OSO₂R, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R, where in each case one or more non-adjacent CH₂ groups may be replaced by RC=CR, C≡C, Si(R)2, Ge(R)2, Sn(R)2, C=O, C=S, C=Se, P(=O)(R), SO, SO2, O or S and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R; where two radicals R²³ may form an aliphatic, aromatic or heteroaromatic ring system together, which may be substituted by one or more radicals R; where R has the same definition as in claim 1, and r stands for 0, 1 or 2.

4. An electronic device according to one or more of the preceding claims, characterized in that the first auxiliary layer comprises a compound B, where at least one group selected from the groups L²⁰, Ar²¹ and Ar²², in formulae (II), (III) and (IV), stands for a group of formula (C-3) or (C-4):

where one symbol Z is bonded to an adjacent group in formula (II), (III) or (IV) if the group of formula (C-1) is Ar²¹ or Ar²², or two symbols Z are bonded to an adjacent group in formula (II), (III) or (IV) if the group of formula (C-1) is L²⁰, where Z and the index r have the same meaning as in claim 3, and p, q stand, identically or differently, for 0, 1, 2 or 3.

5. An electronic device according to one or more of the preceding claims, characterized in that the first auxiliary layer comprises a compound B, which is selected from the compounds of formulae (II-1) to (II-4), (III-1) to (III-4) and (IV-1) to (IV-4),

(III-4)

d 4.

6. An electronic device according to claim 4 or 5, characterized in that the index p is equal to 0 and the index q is equal to 1, 2 or 3.

7. An electronic device according to claim 4 or 5, characterized in that the index p is equal to 1, 2 or 3 and the index q is equal to 0

8. An electronic device according to one or more of claims 1 to 5 and 7, characterized in that the first auxiliary layer comprises a compound B, which is selected from the compounds of formulae (II-1B), (II-3B), (III-1B), (III-3B), (IV-1B) and (IV-3B),

where the symbols and indices have the same meaning as in claims 1, 3 and 4.

9. An electronic device according to one or more of the preceding claims, characterized in that the symbols T²⁰, T²¹ stand for a single bond.

10. An electronic device according to one or more of the preceding claims, characterized in that the compound B is a deuterated compound.

11. An electronic device according to one or more of the preceding claims, characterized in that: -5.30 ≤ HOMO (A) ≤ -5.00 eV where HOMO (A) corresponds to the energy of the highest occupied molecular orbital of the monoamine-based compound (A) in the hole-transport layer as determined by quantum-chemical calculation.

12. An electronic device according to one or more of the preceding claims, characterized in that: -5.50 ≤ HOMO (B) ≤ -5.10 eV where HOMO (B) corresponds to the energy of the highest occupied molecular orbital of the compound B in the first auxiliary layer as determined by quantum-chemical calculation.

13. An electronic device according to one or more of the preceding claims, characterized in that : │T1 (FE) – T1 (B)│ ≤ 0.3 eV where T1 (FE) and T1 (B) have the same definition as in claim 1.

14. An electronic device according to one or more of the preceding claims, characterized in that the first auxiliary layer is in direct contact with the emission layer.

15. An electronic device according to one or more of the preceding claims, characterized in that the hole transport layer is not doped with p-dopants.

16. An electronic device according to one or more of the preceding claims, characterized in that the monoamine-based compound A does not contain any carbazole group.

17. An electronic device according to one or more of the preceding claims, characterized in that the monoamine-based compound A is selected from compound of formula (I-1),

where the dashed lines represent the bonds emanating from the group E¹; T¹, T² are the same or different at each instance and are selected from single bond, O, S, NR¹³, and C(R¹³)₂; R¹⁰, R¹¹, R¹³ stand on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CHO, CN, C(=O)Ar, P(=O)(Ar)₂, S(=O)Ar, S(=O)₂Ar, NO₂, Si(R¹⁹)₃, B(OR¹⁹)₂, OSO₂R¹⁹, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R¹⁹, where in each case one or more non-adjacent CH₂ groups may be replaced by R¹⁹C=CR¹⁹, C≡C, Si(R¹⁹)₂, Ge(R¹⁹)₂, Sn(R¹⁹)₂, C=O, C=S, C=Se, P(=O)(R¹⁹), SO, SO2, O or S and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R¹⁹; where two or more radicals R¹⁰, two or more radicals R¹¹ or two or more radicals R¹³ an aliphatic, aromatic or heteroaromatic ring system together, which may be substituted by one or more radicals R¹⁹; m is equal to 0, 1, 2 or 3; n is equal to 0, 1, 2, 3 or 4; and the other symbols have the same meaning as in claim 1.

18. An electronic device according to according to one or more of the preceding claims, characterized in that the monoamine-based compound A is selected from compounds of formula (I-2),

Formula (I-2) where: E¹⁰ is equal to C(R¹¹)2 or equal to

, where the dashed lines represent the bonds emanating from the group E¹⁰; and where the others symbols and indices have the same meaning as in claims 1 and 17.

19. An electronic device according to one or more of the preceding claims, characterized in that the monoamine-based compound A is selected from compound of formula (I-3A) or (I- 3B),

Formula (I-3A)

Formula (I-3B) where the symbols and indices have the same meaning as in claims 1 and 17.

20. An electronic device according to one or more of the preceding claims, characterized in that the monoamine-based compound A is selected from compounds of formula (I-4A) or (I-4B),

Formula (I-4A)

⁴

s Formula (I-4B) where A² is equal to C(R¹¹)2, O, S or equal to

, where the dashed lines represent the bonds emanating from the group A²; and where R¹⁴ stands on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CHO, CN, C(=O)Ar, P(=O)(Ar)₂, S(=O)Ar, S(=O)₂Ar, NO₂, Si(R¹⁹)₃, B(OR¹⁹)₂, OSO₂R¹⁹, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R¹⁹, where in each case one or more non-adjacent CH₂ groups may be replaced by R¹⁹C=CR¹⁹, C≡C, Si(R¹⁹)₂, Ge(R¹⁹)₂, Sn(R¹⁹)₂, C=O, C=S, C=Se, P(=O)(R¹⁹), SO, SO₂, O or S and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2, an aromatic ring system having 6 to 40 aromatic ring atoms or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R¹⁹; where two or more radicals R¹⁴ may be linked to one another and form a substituted or unsubstituted aliphatic, aromatic ring or heteroaromatic ring, which may be substituted by one or more radicals R¹⁹; s is 0, 1, 2, 3 or 4; t is 0, 1, 2 or 3; and where the other symbols and indices have the same meaning as in claims 1 and 17.

21. An electronic device according to one or more of the precedings claims, characterized in that the monoamine-based compound A is selected from compounds of formula (I-5A) or (I-5B),

Formula (I-5A) Formula (I-5B) where the symbols and indices have the same meaning as in claims 1, 17 and 20.

22. An electronic device according to one or more of the preceding claims, characterized in that the monoamine-based compound A is a deuterated compound.

23. An electronic device according to one or more of the preceding claims, characterized in that the hole transport region further comprises a hole injection layer between the first electrode and the hole transport layer comprising the monoamine-based compound A.

24. An electronic device according to claim 23, characterized in that the hole injection layer comprises a monoamine-based compound of formula (I) as defined in claim 1 and a p- dopant.

25. An electronic device according to one or more of the preceding claims, characterized in that the hole transport layer is in direct contact with the first auxiliary layer.

26. An electronic device according to one or more of claims 1 to 24, characterized in that the hole transport region further comprises a second auxiliary layer between the hole transport layer and the first auxiliary layer.

27. An electronic device according to claim 26, characterized in that the hole transport layer is in direct contact with the second auxiliary layer, the second auxiliary layer is in direct contact with the first auxiliary layer and the first auxiliary layer is in direct contact with the emission layer.