Donor-acceptor connections

Abstract

The invention relates to donor-acceptor compounds comprising at least one carbazole-based donor unit and one acceptor unit. The invention further relates to a method for preparing the above-mentioned donor-acceptor compounds. Furthermore, the invention relates to an emission layer (22) comprising the above donor-acceptor compounds, and to the use of the above donor-acceptor compounds as emitters in a light-emitting device (24). The invention also relates to an electrical device (24), in particular an organic light-emitting diode, comprising the above emission layer (22).

Description

[0001] The invention relates to donor-acceptor compounds comprising at least one carbazole-based donor unit and one acceptor unit.

[0002] Furthermore, the invention relates to an emission layer comprising the above donor-acceptor compounds.

[0003] Furthermore, the invention relates to the use of the above donor-acceptor compounds as emitters in a light-emitting device.

[0004] Furthermore, the invention relates to a method for producing the above donor-acceptor compounds.

[0005] Furthermore, the invention relates to an electrical device, in particular an organic light-emitting diode, comprising the emission layer mentioned above. Description

[0006] Organic light-emitting diodes (OLEDs) are light-emitting electrical devices characterized by, among other things, self-emission, light weight, flexibility, and high efficiency. Due to their good contrast, fast response times, high brightness, excellent operating voltage characteristics, and good color rendering, OLEDs are used particularly in display and lighting products.

[0007] A typical OLED comprises several stacked layers, one of which is an emission layer in which electrically induced holes and electrons recombine, creating excited compounds in the emission layer that emit photons upon relaxation.

[0008] Typically, fluorescent molecules are used in the emission layer. However, when a classical fluorescent molecule is excited, due to spin statistics, 25% of the excited states have a spin state known as a singlet state, and 75% have a spin state known as a triplet state. Since the dominant relaxation process for triplet states is emission-free thermal deactivation, essentially only 25% of the excited states can be used for potential light emission. Therefore, the maximum internal quantum efficiency (IQE) of an OLED using fluorescent molecules is only 25%.

[0009] One way to improve the emission efficiency of OLEDs is to use triplet-emitting materials, which can achieve an IQE of up to 100%. However, triplet-emitting materials are generally based on rare earth metals such as iridium, which makes these materials expensive. Furthermore, the mining of rare earths is complex and often associated with significant environmental impact.

[0010] An alternative approach involves thermally activated delayed fluorescence molecules (TADF molecules), which can also achieve an IQE of up to 100%. In TADF-based materials, the energy gap between the excited singlet and triplet states is small, so that the thermal energy at room temperature is sufficient to transform the excited triplet states from a non-light-emitting, low-energy triplet state to a light-emitting, higher-energy singlet state. Finally, light emission occurs through relaxation of the excited singlet state to the ground state.

[0011] However, the efficiency, molecular stability, difficult synthesis, and poor processability of TADF molecules continue to pose a challenge in their use in OLEDs.

[0012] Based on this, the object of the invention is to provide measures to improve the efficiency and environmental compatibility of OLEDs and to provide TADF molecules that are easier to process and / or synthesize. Furthermore, the object of the invention is to provide TADF molecules that are free of rare earth metals and / or that exhibit high biocompatibility and / or biodegradability.

[0013] The problem is solved according to the invention by the features of the independent claims. Advantageous embodiments of the invention are specified in the dependent claims.

[0014] According to the invention, a donor-acceptor compound of formula (I) is provided comprising at least one carbazole-based donor unit and one acceptor unit, wherein n 1 or 2 is; m 0, 1, or 2 is; XO, S, C=O, or SO2 is; and R 1 and R 2are selected independently of each other from H, deuterium, C1 to C6 alkyl, C1 to C6 alkoxy, aryl, phenyl, trimethylphenyl, Diphenylamine according to and carbazole according to

[0015] Furthermore, according to the invention an emission layer is provided, wherein the emission layer consists of or comprises at least one donor-acceptor compound specified above.

[0016] One aspect of the invention is that the donor-acceptor compounds have exactly one acceptor unit linked to one or more carbazole-based donor units. A carbazole-based donor unit is understood to be that part of the compound which is based on the carbazole structure and is capable of transferring a negative charge to the acceptor unit as an electron donor.

[0017] The donor-acceptor compounds according to the invention have at least one donor unit (n=1 and m=0), but can also have two (n=2 and m=0, or n=1 and m=1), three (n=1 and m=2, or n=2 and m=1), or four (n=2 and m=2) donor units.

[0018] The presence of a donor unit and an acceptor unit linked via a carbon-nitrogen bond ensures a small energy difference between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), resulting in a small energy difference between the first excited singlet state and the triplet state. This small energy difference allows for thermal activation from the triplet state to the singlet state, leading to an IQE of well over 25% and up to 100%. In other words, the donor-acceptor compounds are thermally activated delayed-release fluorescence (TADF) molecules.

[0019] The donor-acceptor compounds therefore exhibit a high IQE and are thus particularly suitable for use as emitters in emission layers of electrical devices and especially light-emitting electrical devices.

[0020] Furthermore, it was found that the donor-acceptor compounds exhibit high solubility in solvents, which offers advantages for the fabrication of emission layers. The donor-acceptor compounds can also be synthesized in simple, preferably one-step, reactions. Moreover, the donor-acceptor compounds proved to be efficient and stable under both electrical and light-induced excitation. This makes them particularly suitable for use in display, lighting, and sensor applications, as well as in photographic applications such as color-converting materials for agricultural films. The donor-acceptor compounds are metal-free, making them environmentally friendly. Moreover, due to their structural similarity, especially of the acceptor unit, to naturally occurring substances, particularly xanthones and anthraquinones, they exhibit high biocompatibility.

[0021] A single carbazole-based donor unit of the donor-acceptor compounds can be unsubstituted, i.e., if R 1 and R 2 which are configured as hydrogen (H), can be deuterated, i.e., R 1 and / or R 2 It is structured as deuterium, or may be further substituted.

[0022] In this context, for the purposes of the present application, the term "alkyl" refers to an alkyl group – that is, an aliphatic hydrocarbon group. The alkyl group is preferably a saturated alkyl group without double or triple bonds.

[0023] The alkyl group is a C1 to C6 alkyl group. The C1 to C6 alkyl group comprises 1 to 6 carbon atoms in an alkyl chain and can be selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl and its isomers, and n-hexyl and its isomers. Furthermore, the C1 to C6 alkyl group can be a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, or a cyclohexyl group.

[0024] In the present application, the term "alkoxy" refers to an alkoxy group – that is, an alkyl group linked via an oxygen atom. Examples of a C1 to C6 alkoxy group are a methoxy group or an ethoxy group.

[0025] In the present application, the term "aryl" refers to an aryl group—that is, a group comprising at least one aromatic hydrocarbon moiety. The aromatic carbon moiety is, for example, a phenyl group or a naphthyl group. Two or more aromatic carbon moiety can be linked by a sigma bond, as in a biphenyl group or a terphenyl group. Furthermore, the aryl group can be configured as a monocyclic, polycyclic, or polycyclic fused-ring functional group, where "fused ring" means that the rings share adjacent pairs of carbon atoms.

[0026] A phenyl group is a specific form of an aryl group formed by a benzene residue—that is, the C6H5 group. Trimethylphenyl is also a specific form of an aryl group formed by a trimethylbenzene residue—that is, a benzene residue substituted with three methyl groups. The trimethylbenzene residue can be a hemellitol, pseudocumene, or mesitylene residue.

[0027] In relation to R 1 and R 2 It may also be provided that these substituents are designed as a diphenylamine group according to (II) or as a carbazole group according to (III):

[0028] According to a preferred embodiment of the invention, the carbazole-based donor unit is not linked to the acceptor unit via position 3. It has been shown that donor-acceptor compounds in which the linkage of the donor unit to the acceptor unit occurs via a position other than the carbon atom at position 3 exhibit better emitter properties.

[0029] According to a preferred embodiment of the invention, n = 1 and the carbazole-based donor unit is connected to the acceptor unit at position 1 or 2 of the acceptor unit. In this preferred embodiment, the donor-acceptor connection thus preferably has a carbazole-based donor unit with respect to "n". The connection of this donor unit is made, as shown in the following examples (IV) and (V), at position 1 or 2 of the acceptor unit, where D is used here as an abbreviation for the donor unit.

[0030] For clarity, structural formulas (IV) and (V) are shown with m = 0. In this preferred embodiment of the invention, m can be 0, 1, or 2.

[0031] According to a further preferred embodiment of the invention, n = 2 and the carbazole-based donor units are connected to the acceptor unit at positions 1 and 2, or 1 and 4. In this preferred embodiment, the donor-acceptor compound thus preferably has two carbazole-based donor units with respect to n. The linkage of these donor units occurs, as shown in the following examples (VI) and (VII), at positions 1 and 2, or 1 and 4 of the acceptor unit, where D is used as an abbreviation for the donor unit, and for clarity, the structural formulas (VI) and (VII) are shown with m = 0. In this preferred embodiment of the invention, m can be 0, 1, or 2.

[0032] According to a further preferred embodiment of the invention, a donor-acceptor compound is provided in which m = 0. This compound therefore preferably has only one or two donor units on a benzene ring of the acceptor unit. Preferably, a donor-acceptor compound is provided which is configured according to the structural formulas (IV), (V), (VI), or (VII) shown, where D is used as an abbreviation for the donor unit.

[0033] According to a further preferred embodiment of the invention, m = 1 and the carbazole-based donor unit is connected to the acceptor unit at positions 5, 6, or 8 of the acceptor unit. In this preferred embodiment, the donor-acceptor connection thus preferably has exactly one carbazole-based donor unit with respect to "m". The connection of this donor unit is made at position 5, 6, or 8 of the acceptor unit, as shown in the following examples (VIII), (IX), and (X), where D is used as an abbreviation for the donor unit: "n" can be 1 or 2 in this preferred embodiment according to the preceding description.

[0034] According to a further preferred embodiment of the invention, m = 2 and the carbazole-based donor units are connected to the acceptor unit at positions 5 and 8, or 7 and 8. In this preferred embodiment, the donor-acceptor compound thus has two carbazole-based donor units with respect to 'm'. The linkage of these donor units occurs, as shown in the following examples (XI) and (XII), at positions 5 and 8, or 7 and 8 of the acceptor unit, where D is used as an abbreviation for the donor unit:

[0035] In this preferred embodiment of the invention, n can be 1 or 2.

[0036] According to a particularly preferred embodiment of the invention, a donor-acceptor compound is provided in which m = 0 and n = 1 and the carbazole-based donor unit is linked to the acceptor unit at position 2. In other words, the linkage of the donor-acceptor units according to structural formula (IV) constitutes a particularly preferred embodiment of the invention, where D is an abbreviation for the donor unit.

[0037] Further preferred are donor-acceptor compounds with symmetry relating to the linkage position of the donor and acceptor units. In this context, according to a preferred embodiment of the invention, m = 1 and n = 1, and the connection of the carbazole-based donor unit with the acceptor unit is such that the donor-acceptor compound exhibits mirror symmetry or rotational symmetry with respect to the linkage position between the donor and acceptor units.

[0038] Particularly preferred with respect to mirror symmetry is a donor-acceptor compound with a linkage of the donor-acceptor units according to structural formula (XIII). Particularly preferred with respect to rotational symmetry is a donor-acceptor compound with a linkage of the donor-acceptor units according to structural formulas (XIV) and (XV), where D is an abbreviation for the donor unit:

[0039] Furthermore, donor-acceptor compounds with n = 2 and m = 2 are preferably having a mirror symmetry with respect to the linkage position of the donor and acceptor units according to structural formula (XVI), where D is an abbreviation for the donor unit:

[0040] With regard to the acceptor unit, a further preferred embodiment of the invention provides that X is configured as oxygen, i.e., X = O, or carbonyl, i.e., X = C = O. When X is configured as O, the acceptor unit is based on the xanthone backbone – also called xanthen-9-one or dibenzo-γ-pyrone. When X is configured as C = O, the acceptor unit is based on the anthraquinone backbone. It has been shown that donor-acceptor compounds with acceptor units based on a xanthone or anthraquinone backbone exhibit higher biocompatibility than other acceptor units. Accordingly, the environmental compatibility of emission layers and OLEDs produced with such donor-acceptor compounds is improved.

[0041] According to a further preferred embodiment of the invention, it is also provided that R 1 and R 2The groups are independently selected from phenyl and trimethylphenyl. With respect to the trimethylphenyl group, this is preferably a mesityl group. R is particularly preferred. 1 = R 2 , and further preferred is R 1 = R 2 structured as phenyl.

[0042] According to a further preferred embodiment of the invention, in the donor-acceptor compound n = 1, m = 0, X = O or X = C=O; and R 1 and R 2 These are phenyl compounds, with the carbazole-based donor unit linked to the acceptor unit at position 2. The following two donor-acceptor compounds with structural formulas (XVII) and (XVIII) have proven particularly suitable for the fabrication of emission layers:

[0043] The invention further relates to the emission layer, wherein the emission layer consists of or comprises at least one donor-acceptor compound as described above. Particularly preferably, the emission layer consists of or comprises the donor-acceptor compound according to structural formulas (XVII) and (XVIII).

[0044] According to a further preferred embodiment of the invention, the emission layer is produced by a solvent-based thin-film process in which the donor-acceptor compound is dissolved in a solvent selected from 2-methyltetrahydrofuran and ethoxybenzene. The donor-acceptor compounds described above have the particular advantage of exhibiting high solubility in the aforementioned solvents, which greatly simplifies the production of the emission layer. Preferably, the solvent-based thin-film process is a rotary coating process, a dip coating process, and / or an inkjet printing process. These processes are also collectively referred to as solution processing and have the advantage over other deposition methods that no vacuum is required, thus making the manufacturing process simple and cost-effective.

[0045] The invention also relates to the use of the donor-acceptor compounds described above as emitters in a light-emitting device. Stable emission layers can be produced cost-effectively using the described donor-acceptor compounds.

[0046] The person skilled in the art can deduce the further advantages of the light-emitting device from the description of the donor-acceptor connections and the electrical device described below.

[0047] Furthermore, the problem is solved by a method for producing the donor-acceptor compounds described above, comprising the step: - Reacting a halogen-substituted, preferably bromine-substituted acceptor unit according to (XIX) with a carbazole-based donor unit according to (XX) in the presence of a preferably palladium-based catalyst and a base, wherein n 1 or 2 is; m 0, 1, or 2 is; XO, S, C=O, or SO2 is; and R 1 and R 2 Selected independently from H, deuterium, C1- to C6-alkyl, C1- to C6-alkoxy, aryl, phenyl, trimethylphenyl, Diphenylamine according to and carbazole according to

[0048] Donor-acceptor compounds can therefore be synthesized in a simple one-step process, reducing the effort and cost of production. Accordingly, these donor-acceptor compounds enable the simple and cost-effective fabrication of emissive layers, electrical and, in particular, light-emitting devices, and OLEDs.

[0049] Cs₂CO₃ can preferably be used as the base. The catalyst can preferably be prepared directly in a one-step synthesis from palladium(II) acetate (Pd(OAc₂)) as the catalyst precursor and the phosphorus ligand tri-tert-butylphosphine (P(C(CH₃)₃)₃) (also known as tri-tert-butylphosphine). Toluene is preferably used as the solvent.

[0050] Furthermore, the problem is solved by an electrical device with at least one emission layer as described above. According to a further preferred embodiment, the device has a cathode layer and an anode layer, wherein the emission layer is arranged between the cathode layer and the anode layer. An electric field can be generated by means of the cathode and anode layers to emit light via the emission layer.

[0051] According to a further preferred embodiment, the electrical device further comprises an electron transport layer, wherein the electron transport layer is preferably arranged between the emission layer and the cathode layer. Alternatively or additionally, the electrical device further comprises a hole transport layer, wherein the hole transport layer is preferably arranged between the emission layer and the anode layer. More preferably, the device can comprise an electron injection layer and / or a hole injection layer. Preferably, the electrical device is configured as a layer stack in the following sequence, wherein the individual layers are directly adjacent to one another: cathode layer, electron injection layer, electron transport layer, emission layer, hole transport layer, hole injection layer, anode layer.

[0052] Preferably, the electrical device comprises a substrate on which the layer stack is applied.

[0053] According to a preferred embodiment, the electrical device is a light-emitting device, a thin-film transistor, or a photovoltaic cell. Particularly preferred is an OLED.

[0054] The invention is explained below by way of example with reference to the drawing and preferred embodiments.

[0055] The drawing shows Fig. 1 schematically in a) an absorption spectrum and emission spectrum of a donor-acceptor compound (XVII) according to a preferred embodiment of the invention and in b) an absorption spectrum and emission spectrum of a donor-acceptor compound (XVIII) according to a further preferred embodiment of the invention, Fig. 2 the absorption spectrum from Fig.1. To determine an energy difference between HOMO and LUMO, Fig. 3 schematically generated measurement results using photoelectron yield spectroscopy in a) for the donor-acceptor compound (XVII) and in b) for the donor-acceptor compound (XVIII), Fig. 4 schematically a layer stack of an OLED, according to a further preferred embodiment of the invention, Fig. 5 schematically in a) electroluminescence measurement results and photoluminescence measurement results for an OLED comprising the donor-acceptor compound (XVII) in an emission layer and in b) electroluminescence measurement results for an OLED comprising the donor-acceptor compound (XVIII) in an emission layer, and Fig.6 schematically in a) measurement results of a luminance-voltage measurement (top) and a current density-voltage measurement (bottom) for an OLED which includes the donor-acceptor connection (XVII) in an emission layer and in b) measurement results of a luminance-voltage measurement (top) and a current density-voltage measurement (bottom) for an OLED which includes the donor-acceptor connection (XVII) in an emission layer.

[0056] Two donor-acceptor compounds according to preferred embodiments of the invention with structural formulas (XVII) and (XVIII) were synthesized as described below:

[0057] The synthesis was carried out using palladium(II) acetate as a catalyst precursor, cesium carbonate as a base, and tri-tert-butylphosphine as a catalyst ligand according to the following reaction scheme. Purification was achieved by chromatography, crystallization, and sublimation.

[0058] 2-Bromo-9H-xanthen-9-one for the donor-acceptor compound (XVII) or 2-bromanthracene-9,10-dione for the donor-acceptor compound (XVIII), 3,6-diphenyl-9H-carbazole, palladium diacetate, cesium carbonate, and tri-tert-butylphosphine were dissolved in anhydrous toluene and heated under reflux overnight. The solution was then filtered, the toluene removed under vacuum, and the resulting solid dissolved in dichloromethane. The dichloromethane solution was washed with saturated sodium chloride (NaCl in H₂O), dried over sodium sulfate, and the solvent removed under vacuum. Finally, the donor-acceptor compound was purified by silica gel column chromatography.

[0059] The donor-acceptor compounds (XVII) and (XVIII) were characterized and used to fabricate an OLED.

[0060] Table 1 shows the results of a solubility test for the donor-acceptor compounds (XVII) and (XVIII). The solubility of compound (XVII) in anisole, acetonitrile, and methyl benzoate was not determined. Table 1: Solubility of donor-acceptor compounds (XVII) and (XVIII) solvent Donor-acceptor connections (XVII) Donor-acceptor connections (18th century) Tetrahydrofuran (THF) Medium Medium 2-Methyltetrahydrofuran High Medium Ethoxybenzene High Medium Anisolone n / a Medium Acetonitril n / a High Methyl benzoate n / a Medium

[0061] The Fig. Figure 1 schematically shows in a) the absorption spectrum 10 and emission spectrum 12 of the donor-acceptor compound (XVII) and in b) the absorption spectrum 10 and emission spectrum 12 of the donor-acceptor compound (XVIII) in 2-methyltetrahydrofuran. The spectra in Fig. 1 is the x-axis, 14 the wavelength in nm, and 16 the y-axis the absorbance or emission in arbitrary units.

[0062] The Fig. Figure 2 schematically shows how to use the absorption spectrum from Fig.1. The energy difference between HOMO and LUMO is estimated for donor-acceptor compounds (XVII) and (XVIII). For donor-acceptor compounds (XVII), the HOMO-LUMO energy difference is estimated to be 2.64 eV, and for donor-acceptor compounds (XVIII), the HOMO-LUMO energy difference is estimated to be 2.16 eV.

[0063] Fig. Figure 3 shows schematically in Fig. 3a) Measurement results generated by photoelectron yield spectroscopy (PSY) for the determination of the ionization energy for the donor-acceptor compound (XVII) and in Fig.3b) for the donor-acceptor connection (XVIII). PSY is a method for measuring ionization energy using the photoemission effect. A sample surface is irradiated with tunable UV light, and the number of emitted photoelectrons is measured. The photoelectron quantum yield, i.e., the number of emitted photoelectrons per absorbed photon, is recorded as a function of the incident photon energy. The x-axis 18 in Fig. Figure 3 shows the photon energy in eV; the y-axis 20 shows the photoelectron yield in an arbitrary unit.

[0064] The donor-acceptor compounds (XVII) and (XVIII) were deployed in an emission layer 22 of an OLED. Fig.Figure 4 schematically shows the structure of the OLED. The OLED is designed as a layer stack 24 in the following sequence, with the individual layers directly adjacent to each other: cathode layer 26, electron injection layer 28, electron transport layer 30, emission layer 22, hole transport layer 32, hole injection layer 34, anode layer 36, substrate 38.

[0065] Fig. Figure 5 shows the measurement of the electroluminescence of the obtained OLEDs, where Fig. 4a) shows the electroluminescence spectrum 40 for the OLED, which includes the donor-acceptor junction (XVII) in the emission layer 22, and Fig. 4b) shows the electroluminescence spectrum 40 for the OLED, which includes the donor-acceptor junction (XVIII) in the emission layer 22. In electroluminescence, the OLED is excited to emit photons by applying an electric field. Fig.Figure 4a) also shows the photoluminescence spectrum 42 for comparison. In photoluminescence, excitation occurs through photons. The x-axis 14 in Fig. Figure 4 shows the wavelength in nm and the y-axis 16 shows the emission in an arbitrary unit.

[0066] Fig. Figure 6 shows in the upper half measurement results of a luminance-voltage measurement and in the lower half measurement results of a current density-voltage measurement of the obtained OLEDs, wherein Fig. 6a) shows the measurements for the OLED that includes the donor-acceptor junction (XVII) in the emission layer 22, and Fig. 6b) shows the measurements for the OLED, which includes the donor-acceptor junction (XVIII) in the emission layer 22. The x-axis 44 in Fig. Figure 6 shows the voltage applied to the OLED in V, the y-axis 46 for the luminance-voltage measurement shows the luminance in cd / m² 2 and the y-axis 48 for the current density-voltage measurement shows the current density in mA / cm².2 . Reference symbol list 10 Absorption spectrum 12 Emission spectrum 14 x-axis, wavelength in nm 16 y-axis, absorbance or emission in arbitrary unit 18 x-axis, photon energy in eV 20 y-axis, photoelectron yield in arbitrary units 22 Emission layer 24-layer stack 26 Cathode layer 28 Electron injection layer 30 Electron transport layer 32-hole transport layer 34-hole injection layer 36 Anode layer 38 Substrat 40 Electroluminescence spectrum 42 Photoluminescence spectrum 44 x-axis, voltage in V 46 y-axis, luminance in cd / m² 2 48 y-axis, current density in mA / cm² 2

Claims

[1] Donor-acceptor compound of formula (I) comprising at least one carbazole-based donor unit and one acceptor unit, wherein n 1 or 2 is; m 0, 1, or 2 is; XO, S, C=O, or SO2 is; and R 1 and R 2 are independently selected from H, deuterium, C1- to C6-alkyl, C1- to C6-alkoxy, aryl, phenyl, trimethylphenyl, diphenylamine according to and carbazole according to [2] Donor-acceptor compound according to claim 1, wherein the carbazole-based donor unit is not connected to the acceptor unit via position 3 of the acceptor unit. [3] Donor-acceptor compound according to claim 1 or 2, wherein n = 1 and the carbazole-based donor unit is connected to the acceptor unit at position 1 or 2 of the acceptor unit. [4] Donor-acceptor compound according to claim 1 or 2, wherein n = 2 and the carbazole-based donor units are connected to the acceptor unit at positions 1 and 2, or 1 and 4. [5] Donor-acceptor compound according to any one of claims 1 to 4, wherein m = 0. [6] Donor-acceptor compound according to any one of claims 1 to 4, wherein m = 1 and the carbazole-based donor unit is connected to the acceptor unit at positions 5, 6 or 8 of the acceptor unit. [7] Donor-acceptor compound according to any one of claims 1 to 4, wherein m = 2 and the carbazole-based donor units are connected to the acceptor unit at positions 5 and 8, or 7 and 8. [8] Donor-acceptor compound according to claim 1 or 2, wherein m = 0 and n = 1 and the carbazole-based donor unit is connected to the acceptor unit at position 2 of the acceptor unit. [9] Donor-acceptor compound according to claim 1 or 2, wherein m = 1 and n = 1 and the connection of the carbazole-based donor unit with the acceptor unit is such that the donor-acceptor compound has mirror symmetry or rotational symmetry with respect to the linkage position between donor unit and acceptor unit. [10] Donor-acceptor compound according to any one of claims 1 to 9, wherein XO or C=O. [11] Donor-acceptor compound according to any one of claims 1 to 10, wherein R 1 and R 2 They were selected independently from phenyl and trimethylphenyl. [12] Donor-acceptor compound according to claim 1, wherein n 1 is; m 0 is; X O or C=O is; and R 1 and R 2 Phenyl are, and the carbazole-based donor unit is connected to the acceptor unit at position 2. [13] Emission layer (22), wherein the emission layer (22) consists of or comprises at least one donor-acceptor compound according to any one of the preceding claims 1 to 12. [14] Emission layer (22) according to claim 13, produced by a solvent-based thin-film process wherein the donor-acceptor compound is dissolved in a solvent selected from 2-methyltetrahydrofuran and ethoxybenzene. [15] Use of a donor-acceptor connection according to any one of claims 1 to 12 as an emitter in a light-emitting device (24). [16] Method for producing a donor-acceptor compound according to any one of claims 1 to 12, comprising the step: - Reacting a halogen-substituted, preferably bromine-substituted acceptor unit according to (XIX) with a carbazole-based donor unit according to (XX) in the presence of a preferably palladium-based catalyst and a base, wherein n 1 or 2 is; m 0, 1, or 2 is; XO, S, C=O, or SO2 is; and R 1 and R 2 are independently selected from H, deuterium, C1- to C6-alkyl, C1- to C6-alkoxy, aryl, phenyl, trimethylphenyl, diphenylamine according to and carbazole according to [17] Electrical device (24) with at least one emission layer (22) according to claim 13 or 14. [18] Electrical device (24) according to claim 17 further comprising a cathode layer (26) and an anode layer (36), wherein the emission layer (22) is arranged between the cathode layer (26) and the anode layer (36). [19] Electrical device (24) according to claim 17 or 18, further comprising an electron transport layer (30), wherein the electron transport layer (30) is preferably arranged between the emission layer (22) and the cathode layer (26); and / or further comprising a hole transport layer (32), wherein the hole transport layer (32) is preferably arranged between the emission layer (22) and the anode layer (36). [20] Electrical device (24) according to any one of the preceding claims 17 to 19, wherein the electrical device is a light-emitting device (24), a thin-film transistor, or a photovoltaic cell.

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