DE102019118872A1 - Organic compound and optoelectronic component with such an organic compound - Google Patents

Abstract

The invention relates to a compound of the general formula I and an optoelectronic component with a layer system, at least one layer of the layer system having at least one compound of the general formula I

Description

The present invention relates to an organic compound and an optoelectronic component comprising a first electrode, a second electrode and a layer system, the layer system having at least one layer with at least one such organic compound.

Organic semiconductors based on low molecular weight or polymer compounds are increasingly being used in many areas of the electrical industry. Organic semiconductors are used, for example, in optoelectronic components such as OFETs, OLEDs, OPVs, and photodetectors. If the optoelectronic component is a photovoltaic component, such as a solar cell or a photodetector, then the component is suitable for converting light energy into electrical energy, the opposite conversion of electrical energy into light emission having a detrimental effect on efficiency. LEDs, on the other hand, convert electrical current or voltage signals or electrical energy into light emission.

Organic photovoltaic components, solar cells, usually consist of a sequence of thin layers between two electrodes, which are preferably evaporated in a vacuum or processed from a solution. The electrical contact can be made through metal layers, transparent conductive oxides (TCOs) and / or transparent conductive polymers (PEDOT-PSS, PANI). The vacuum evaporation of the organic layers is advantageous in the production of tandem, triple or multiple solar cells. The individual cells are stacked in tandem or multiple solar cells, with each cell containing at least one absorber layer, arranged between two electrodes and usually connected in series, so that the cell that produces the lowest current limits the entire system.

The photoactive compounds are usually used in one or two adjacent layers for the formation of donor-acceptor heterojunctions within a cell, in which at least one donor or one acceptor is the light-absorbing component. In contrast to inorganic solar cells based on silicon, light does not directly generate free charge carriers in organic solar cells, but excitons, i.e. electrically neutral states of excitation, in particular bound electron-hole pairs, are initially formed. These excitons are separated into charge carriers at the donor-acceptor interface in transitions between two adjacent layers or within a photoactive mixed layer, which then contribute to the flow of electrical current.

The term “photoactive” is understood to mean, in particular, a conversion of light energy into electrical energy. Photoactive compounds have a large absorption coefficient, at least for a certain wavelength range.

Optoelectronic components, in particular organic solar cells, can also have further layers, such as charge carrier transport layers - also called transport layers, between the electrodes, which make no or only a small contribution to absorption compared to a photoactive layer. These layers can be doped, partially doped, undoped or have a doping gradient.

The photoactive layers can be built up from polymers or small molecules. While polymers are characterized by the fact that they cannot be evaporated and can therefore only be applied from solution, small molecules can be evaporated.

Small molecules are understood to mean, in particular, non-polymeric organic molecules with monodisperse molar masses between 100 and 2000 g / mol, which are present in the solid phase under normal pressure and at room temperature. The small molecules are preferably photoactive, with photoactive being understood in particular to mean that the molecules change their charge state and / or their polarization state when light is introduced.

The use of such optoelectronic components based on small organic molecules offers the possibility of producing very thin solar cells with little use of material and energy.

WO 2006/092134 A1 discloses compounds that have an acceptor-donor-acceptor structure, the donor block having an extended π system.

WO 2006/111511 A1 discloses hexaarylene and pentaarylene tetracarboxylic acid diimides as active components in photovoltaics.

WO 2008/145172 A1 discloses substituted carboxyphthalocyanines and their use as active components in photovoltaics.

Photoactive organic molecules also include compounds of the BODIPY class, consisting of a fused planar structure that has two pyrrole rings and a central 6-ring, on which both pyrrole rings are connected via CCC and NBN linkages. The two F atoms on the B atom protrude from the conjugated surface, with the BF bonds having different lengths, which leads to a distorted tetrahedral coordination of the B atom. The bond length of the CC bonds and the CN bonds in the central 6-ring with a length of approx. 0.138 nm is comparable, which suggests a conjugated π-electron system. The two NB bonds have a similar length of 0.155 nm. Both the HOMO and the LUMO are delocalized over the entire molecule with the exception of the BF ₂ group. The compounds of the class of BODIPYs are 4,4-difluoro-4-bora-3a, 4a-diaza-s-indazene, and got their name from the abbreviation of the name of the borodipyrromethene, which is also used. The basic structure of an unsubstituted BODIPY is shown below:

WO 2007/126052 A1 discloses fluorescent compounds based on a BODIPY backbone and an application of the compounds described as fluorescent dyes.

The invention is therefore based on the object of providing an organic material which can be evaporated in a vacuum and can be used as an absorber to improve the efficiency of organic solar cells, and an optoelectronic component which contains such an organic material.

The object is achieved by the subjects of the independent claims. Advantageous configurations result from the subclaims.

A particular disadvantage of the prior art is that there is often no thermal stability for evaporation of organic molecules in a vacuum, the absorption strength in thin layers is insufficient, and / or transport properties for charge carriers are insufficient. The BODIPYs known from the prior art as a component in absorber or transport layers of optoelectronic components are not satisfactory with regard to the absorption spectrum. The currently achieved efficiency of organic solar cells is therefore not yet sufficient for commercial use, so that the efficiency must be increased through the use of improved organic molecules.

dadurch gekennzeichnet, dass

• • R4 und R5 jeweils unabhängig voneinander ausgewählt sind aus der Gruppe bestehend aus H, Alkoxy, Alkyl, fluoriertem Alkyl, teilfluoriertem Alkyl, Amino, und Aryl;
• • R6 und R7 jeweils unabhängig voneinander ausgewählt sind aus der Gruppe bestehend aus H, Alkoxy, Alkyl, fluoriertem Alkyl, teilfluoriertem Alkyl, und Amino;
• • R9, R10, R11, R12, R13 und R14 jeweils unabhängig voneinander ausgewählt sind aus der Gruppe bestehend aus H, Alkoxy, unsubstituiertem Alkyl, substituiertem Alkyl, Amino, Aryl und Heteroaryl, und/oder R9 und R10 oder R10 und R11, und/oder R12 und R13 oder R13 und R14 jeweils zusammen einen heterocyclischen oder homocyclischen 5-Ring oder 6-Ring bilden;
• • X1 und X2 jeweils unabhängig voneinander O oder S sind; und
• • Y1 und Y2 jeweils unabhängig voneinander ausgewählt sind aus der Gruppe bestehend aus O, S und N-R8, wobei R8 H oder Alkyl ist.

The object is achieved in particular by providing a compound of the general formula I,

characterized in that

• • R4 and R5 are each independently selected from the group consisting of H, alkoxy, alkyl, fluorinated alkyl, partially fluorinated alkyl, amino, and aryl;
• • R6 and R7 are each independently selected from the group consisting of H, alkoxy, alkyl, fluorinated alkyl, partially fluorinated alkyl, and amino;
• • R9, R10, R11, R12, R13 and R14 are each independently selected from the group consisting of H, alkoxy, unsubstituted alkyl, substituted alkyl, amino, aryl and heteroaryl, and / or R9 and R10 or R10 and R11, and / or R12 and R13 or R13 and R14 each together form a heterocyclic or homocyclic 5-ring or 6-ring;
• • X1 and X2 are each independently O or S; and
• • Y1 and Y2 are each independently selected from the group consisting of O, S and N-R8, where R8 is H or alkyl.

In connection with the invention it is also disclosed that on the central 6-ring of the BODIPYs C ₂ F ₅ by CF ₃ , C ₂ F ₄ H, C ₂ F ₃ H ₂ , C ₃ F ₇ , C ₃ F ₆ H, or C ₃ F ₅ H ₂ can be replaced.

In connection with the invention it is also disclosed that at least one F atom of the BF ₂ group on the central 6-ring of the BODIPYs can be replaced by CF ₃ and / or alkoxy.

In a preferred embodiment of the invention, the at least one heteroatom of the heterocyclic 5-ring or 6-ring formed by R9 and R10 or R10 and R11, and / or R12 and R13 or R13 and R14 together is selected from the group consisting of O, S, N and P, preferably selected from O or S.

In a preferred embodiment of the invention, both R9 and R10 as well as R12 and R13 each together form a heterocyclic 5-ring or 6-ring with at least one heteroatom selected from the group consisting of S, O, N or P.

In a preferred embodiment of the invention, both R9 and R10 and also R12 and R13 together each form a 5-ring or a 6-ring which is not further fused.

The compounds of the general formula I according to the invention have advantages compared to the prior art. Compounds of general formula I advantageously absorb red and near-infrared light in a wavelength range from 600 to 900 nm. Compounds of general formula I advantageously have suitable transport properties for optoelectronic components. Compounds of the general formula I can advantageously be adapted in terms of energy to the layer system of the optoelectronic component by variations. Optoelectronic components, in particular a solar cell, can advantageously be produced with improved efficiency.

Compounds of the general formula I are in particular thermally stable above 200 ° C., preferably above 300 ° C., and can be processed into layers at least largely free of decomposition by thermal evaporation in a vacuum. In addition, with the compounds of general formula I, the absorbed energy at a heterojunction to molecules with acceptor character (e.g. fullerene C60) can be converted into free charge carrier pairs and ultimately into electrical energy and used.

According to a further development of the invention it is provided that X1 and X2 are each O or S, and Y1 and Y2 are each O or S, with X1 and X2 being O and Y1 and Y2 being S preferably.

According to a further development of the invention it is provided that R4 is equal to R5, and R6 is equal to R7, and / or R9 is equal to R12, R10 is equal to R13 and R11 is equal to R14.

According to a further development of the invention it is provided that R4 and R5 are H, and R6 and R7 are H.

In a preferred embodiment of the invention, the compound of the general formula I is formed symmetrically with respect to the mirror axis through which the B atom and the point of attachment of C ₂ F _{5 are} built up.

According to a development of the invention it is provided that R9 and R10, or R10 and R11, and / or R12 and R13, or R13 and R14 each together form a heterocyclic 5-ring or homocyclic or heterocyclic 6-ring with at least one heteroatom selected from the Group consisting of S, O and N form.

In a preferred embodiment of the invention, the heterocyclic 5-ring or 6-ring formed by R9 and R10 or R10 and R11, and / or R12 and R13 or R13 and R14 is selected from one of the following formulas:

The parts of the above formulas marked with * represent the points of attachment to R9 and R10 or R10 and R11, and / or R12 and R13 or R13 and R14 of the compound of the general formula I. X, Y and Z are independently selected from O, S, Se or N-R15, with R15 selected from H or alkyl. R19 to R26 are independently selected from H, alkyl, alkynyl, alkenyl, alkoxy, alkthiooxy, aryl, heteroaryl, halogenated alkyl and cyanated alkyl.

In a preferred embodiment of the invention, furan, imidazole, isoxazole, oxadiazole, oxazole, pyrazole, pyrrole, thiazole, thiophene are formed at the binding sites R9 and R10 or R10 and R11, and / or R12 and R13 or R13 and R14 , or formed as a 6-ring benzene, diazine, pyridine, pyridazine, pyrimidine or pyrazine.

Preferred compounds of the general formula I according to the invention are shown below:

According to a further development of the invention it is provided that the compound is the formula II

The object of the present invention is also achieved by providing an optoelectronic component comprising a first electrode, a second electrode and a layer system, the layer system being arranged between the first electrode and the second electrode. The optoelectronic component is characterized in that at least one layer of the layer system has at least one compound of the general formula I according to the invention. The advantages for the optoelectronic component that have already been explained in connection with the compound of the general formula I result in particular.

According to a development of the invention, it is provided that the layer system has at least one photoactive layer, the at least one photoactive layer having the at least one compound of the general formula I.

A photoactive layer is understood to mean, in particular, a layer of an optoelectronic component which makes a contribution to the absorption of radiation and / or to the emission of radiation, in particular the photoactive layer absorbs radiation. The photoactive layer is preferably designed for a donor / acceptor heterojunction (heterojunction).

According to a development of the invention it is provided that the layer system has at least two, preferably at least three, or preferably at least four photoactive layers.

A plurality of photoactive layers, preferably at least two, preferably at least three, or preferably at least four photoactive layers, are preferably stacked one on top of the other between two electrodes.

In a preferred embodiment of the invention, the photoactive layer containing the at least one compound of the general formula I adjoins at least one charge carrier transport layer, the charge carrier transport layer preferably being doped, partially doped or undoped.

Doping is understood to mean, in particular, an admixture of a dopant to increase the density of free charge carriers, electrons for n-doping and holes for p-doping. Dopants are compounds, in particular organic molecules, that change the electrical properties of a matrix material without necessarily being semiconducting themselves. The concentration of the dopant is preferably between 1% and 30% by weight of the layer.

In a preferred embodiment of the invention, the compound of the general formula I has a molar mass of 100 to 1500 g / mol, preferably from 200 to 800 g / mol.

According to one development of the invention, it is provided that the optoelectronic component is a solar cell, an FET, an LED or a photodetector, preferably an organic solar cell, an OFET, an OLED or an organic photodetector.

According to a development of the invention it is provided that the photoactive layer is designed as a mixed layer of the at least one compound of the general formula I and at least one further compound, or as a mixed layer of the at least one compound of the general formula I and at least two further compounds.

The layer containing at least one compound of the formula I preferably adjoins an electron transport layer. The electron transport layer preferably has a fullerene or a fullerene derivative.

In a preferred embodiment of the invention, the compound of the general formula I is present as absorbing material in a layer system for absorbing light. The layer system contains at least one organic donor material in contact with at least one organic acceptor material, the donor material and the acceptor material forming a donor-acceptor heterojunction, and the at least one photoactive layer having at least one compound of the general formula I.

In a preferred embodiment of the invention, at least one of the photoactive mixed layers contains a fullerene and / or a fullerene derivative as an acceptor.

1. 1. Elektrode (Grundkontakt) auf einem Substrat;
2. 2. Transportschicht(en) - hier p-type,
3. 3. i-Schicht(en),
4. 4. Transportschicht(en) - hier n-type,
5. 5. Elektrode (Deckkontakt), als Single-Solarzelle.

A simple way of realizing an organic solar cell is, for example, in one embodiment in a pin diode with the following layer structure:

1. 1. Electrode (ground contact) on a substrate;
2. 2. Transport layer (s) - here p-type,
3. 3. i-layer (s),
4. 4. Transport layer (s) - here n-type,
5. 5. Electrode (cover contact), as a single solar cell.

Here, n or p denotes an n or p doping, which leads to an increase in the density of free electrons or holes in the thermal equilibrium state. In this sense, such layers are primarily to be understood as transport layers, in particular charge carrier transport layers. In contrast, the term i-layer (intrinsic layer) preferably denotes an undoped layer or a weakly doped layer, in particular a photoactive layer. One or more i-layer (s) can consist of one material or a mixture of two or more materials.

In a preferred embodiment of the invention, the i-layer of the optoelectronic component is designed as a mixed layer. This can be achieved, for example, by co-evaporating two or more materials.

In a preferred embodiment of the invention, an n-layer is arranged between the ground contact (electrode) and the p-layer and / or between the p-layer and the i-layer.

In a preferred embodiment of the invention, a p-layer is arranged between the cover contact (electrode) and the n-layer and / or between the n-layer and the i-layer.

In a preferred embodiment of the invention, the optoelectronic component is a tandem or multiple solar cell, with two or more layer systems preferably being stacked one on top of the other between the electrodes and being connected in series. Each layer system comprises at least one i-layer and at least one charge carrier transport layer (p- or n-layer). According to the invention, at least one i-layer of a layer system in a tandem or multiple solar cell comprises the compound according to the invention according to general formula I. When using highly doped charge carrier transport layers at the transitions between two layer systems, the use of a contact layer between the layer systems is not necessary.

In a preferred embodiment of the invention, the i-layers of the individual layer systems are made up of the same materials or material mixtures; in an alternatively preferred embodiment, the i-layers of the individual layer systems are made up of different materials or material mixtures.

In order to be able to use the full solar spectrum, however, several organic compounds are necessary in the layer system, which absorb at different wavelengths and are energetically optimized by optimizing layer thicknesses or the number of layers in the layer system (s).

The object of the present invention is also achieved by providing the use of a compound of the general formula I according to the invention in a photoactive layer of an optoelectronic component, preferably in an organic solar cell, an OFET, an OLED or an organic photodetector, in particular according to one of the previously described embodiments. The use of the compound of the general formula I in an optoelectronic component results in particular in the advantages that have already been explained in connection with the compound of the general formula I and the optoelectronic component with at least one compound of the general formula I.

• 1 eine schematische Darstellung einer Synthese einer Verbindung der allgemeinen Formel I in einem Ausführungsbeispiel,
• 2 eine schematische Darstellung eines optoelektronischen Bauelements in einem Ausführungsbeispiel,
• 3 eine grafische Darstellung einer Strom-Spannungskurve, einer spektralen externen Quantenausbeute und des Füllfaktors eines optoelektronischen Bauelements mit der Verbindung II,
• 4 eine grafische Darstellung eines Absorptionsspektrums der Verbindung II im Vergleich mit Verbindung III,
• 5 eine grafische Darstellung einer Strom-Spannungskurve, einer spektralen externen Quantenausbeute und des Füllfaktors eines optoelektronischen Bauelements mit der Verbindung III,
• 6 eine grafische Darstellung eines Absorptionsspektrums der Verbindungen IV und V,
• 7 eine grafische Darstellung einer Strom-Spannungskurve, einer spektralen externen Quantenausbeute und des Füllfaktors eines optoelektronischen Bauelements mit der Verbindung IV,
• 8 eine grafische Darstellung einer Strom-Spannungskurve, einer spektralen externen Quantenausbeute und des Füllfaktors eines optoelektronischen Bauelements mit der Verbindung V, und
• 9 eine grafische Darstellung einer Strom-Spannungskurve, einer spektralen externen Quantenausbeute und des Füllfaktors eines optoelektronischen Bauelements mit der Verbindung VI.
• 10 zeigt erfindungsgemäße Verbindung gemäß der allgemeinen Formel I.

The invention is explained in more detail with reference to the following exemplary embodiments and figures. It shows

• 1 a schematic representation of a synthesis of a compound of general formula I in one embodiment,
• 2 a schematic illustration of an optoelectronic component in one embodiment,
• 3 a graphic representation of a current-voltage curve, a spectral external quantum yield and the fill factor of an optoelectronic component with the compound II,
• 4th a graphic representation of an absorption spectrum of compound II compared with compound III,
• 5 a graphic representation of a current-voltage curve, a spectral external quantum yield and the fill factor of an optoelectronic component with compound III,
• 6th a graphic representation of an absorption spectrum of compounds IV and V,
• 7th a graphic representation of a current-voltage curve, a spectral external quantum yield and the fill factor of an optoelectronic component with the compound IV,
• 8th a graphical representation of a current-voltage curve, a spectral external quantum yield and the fill factor of an optoelectronic component with the connection V, and
• 9 a graphical representation of a current-voltage curve, a spectral external quantum yield and the filling factor of an optoelectronic component with the compound VI.
• 10 shows compound according to the invention according to the general formula I.

Exemplary embodiment - synthesis of BODIPYs

1 shows a schematic representation of a synthesis of a compound of the general formula I in one embodiment.

ist dadurch gekennzeichnet, dass

• • R4 und R5 jeweils unabhängig voneinander ausgewählt sind aus der Gruppe bestehend aus H, Alkoxy, Alkyl, fluoriertem Alkyl, teilfluoriertem Alkyl, Amino, und Aryl;
• • R6 und R7jeweils unabhängig voneinander ausgewählt sind aus der Gruppe bestehend aus H, Alkoxy, Alkyl, fluoriertem Alkyl, teilfluoriertem Alkyl, und Amino;
• • R9, R10, R11, R12, R13 und R14 jeweils unabhängig voneinander ausgewählt sind aus der Gruppe bestehend aus H, Alkoxy, unsubstituiertem Alkyl, substituiertem Alkyl, Amino, Aryl und Heteroaryl, und/oder R9 und R10 oder R10 und R11, und/oder R12 und R13 oder R13 und R14 jeweils zusammen einen heterocyclischen oder homocyclischen 5-Ring oder 6-Ring bilden;
• • X1 und X2 jeweils unabhängig voneinander O oder S sind; und
• • Y1 und Y2 jeweils unabhängig voneinander ausgewählt sind aus der Gruppe bestehend aus O, S und N-R8, wobei R8 H oder Alkyl ist.

The compound of the general formula I

is characterized in that

• • R4 and R5 are each independently selected from the group consisting of H, alkoxy, alkyl, fluorinated alkyl, partially fluorinated alkyl, amino, and aryl;
• • R6 and R7 are each independently selected from the group consisting of H, alkoxy, alkyl, fluorinated alkyl, partially fluorinated alkyl, and amino;
• • R9, R10, R11, R12, R13 and R14 are each independently selected from the group consisting of H, alkoxy, unsubstituted alkyl, substituted alkyl, amino, aryl and heteroaryl, and / or R9 and R10 or R10 and R11, and / or R12 and R13 or R13 and R14 each together form a heterocyclic or homocyclic 5-ring or 6-ring;
• • X1 and X2 are each independently O or S; and
• • Y1 and Y2 are each independently selected from the group consisting of O, S and N-R8, where R8 is H or alkyl.

The compounds of general formula I can as in WO 2007/126052 A1 , T.-y. Li et. al: Small Molecule Near-Infrared Boron Dipyrromethene Donors for Organic Tandem Solar Cells, J. Am. Chem. Soc., 2017, 139, 13636-13639. or J. Mater. Chem. A, 2018,6, 18583-18591 described.

An embodiment of a synthesis of a compound of general formula I is in 1 shown.

The synthesis of BODIPYs 17th with fused furan and meso-CF ₃ group with R = a, b, c, d, e, f, g is in 1 shown.

1. (i) Pd(dppf)Cl2, Na₂CO₃, PhMe, EtOH, H₂O, unter Rückfluss, 6 h;
2. (ii) NaOMe, MeOH, RT, 6 h;
3. (iii) PhMe, unter Rückfluss, 12 h;
4. (iv) NaOH, EtOH, unter Rückfluss, 1 h;
5. (v) TFA, TFA Anhydrid, bei 40°C unter Rückfluss, 1 h;
6. (vi) DIPEA, BF₃·OEt₂, DCM, RT, 2 h.

In one embodiment, the reaction conditions are as follows:

1. (i) Pd (dppf) Cl2, Na ₂ CO ₃ , PhMe, EtOH, H ₂ O, under reflux, 6 h;
2. (ii) NaOMe, MeOH, RT, 6 h;
3. (iii) PhMe, reflux, 12 h;
4. (iv) NaOH, EtOH, reflux, 1 h;
5. (v) TFA, TFA anhydride, at 40 ° C under reflux, 1 h;
6. (vi) DIPEA, BF ₃ • OEt ₂ , DCM, RT, 2 h.

Aromatic boronic acid reacts with 5-bromo-2-furaldehyde to introduce a peripherally aromatic residue into that obtained by Suzuki cross-coupling 12 (i). The Suzuki coupling connects the aromatic ring with the furalaldehyde residue in a yield of over 80%. A Knoevenagel condensation is carried out to condense an aldehyde group (ii), whereby by reaction of methyl azidoacetate with 12 the connection 13 is obtained. The condensation of 12 with methyl azidoacetate is carried out in anhydrous MeOH with sodium methoxide produced in situ. 13 is isolated by filtration after the reaction mixture has been passed into cold water with NH ₄ OAc. The light yellow solid obtained is dissolved in toluene and heated under reflux overnight in order to close the pyrrolo structure by ring closure with nitrogen. The following Hemetsberger indolization forms 14th with a fused pyrrole ring by heating 13 in toluene under reflux (iii). After removing the solvent, the dark brown solid obtained is washed with ether and 14th obtained as a light yellow or brown solid by filtering. The ester group in 14th is hydrolyzed into a carboxyl group and compound in heated NaOH solution 15th received (iv). The hydrolysis of the ester into a carboxyl group is carried out in ethanol solution by adding aqueous NaOH solution under reflux. After the reaction mixture has been introduced into cold water and neutralized with hydrochloric acid solution, becomes 15th obtained by filtration as a gray solid. The dried one 15th is heated in TFA at 40 ° C for 15 minutes to prepare the furan-fused pyrroles in-situ by decarboxylation, TFA anhydride is added dropwise to synthesize dipyrromethene 16 initiate. The BODIPY forerunner 16 is made by reaction of 15th obtained in TFA with TFA anhydride (v). The BODIPY precursor purified by column chromatography 16 is treated with DIPEA and BF ₃ · OEt ₂ in anhydrous DCM. The final product 17th is obtained by coordinating dipyrromethene with a BF ₂ group (vi) and purified by column chromatography.

The synthesis of BODIPYs with alkylated substituents (R = h, i, j, k) on the peripheral benzyl rings is also carried out according to the reaction scheme in 1 carried out.

1. (i) Pd(dppf)Cl2, Na₂CO₃, PhMe, EtOH, H₂O, unter Rückfluss, 6 h;
2. (ii) NaOMe, MeOH, RT, 6 h;
3. (iii) PhMe, unter Rückfluss, 12 h;
4. (iv) NaOH, EtOH, unter Rückfluss, 1 h;
5. (v) TFA, TFA Anhydrid, 40°C unter Rückfluss, 1 h;
6. (vi) DIPEA, BF₃·OEt₂, DCM, RT, 2 h.

The reaction conditions are as follows:

1. (i) Pd (dppf) Cl2, Na ₂ CO ₃ , PhMe, EtOH, H ₂ O, under reflux, 6 h;
2. (ii) NaOMe, MeOH, RT, 6 h;
3. (iii) PhMe, reflux, 12 h;
4. (iv) NaOH, EtOH, reflux, 1 h;
5. (v) TFA, TFA anhydride, 40 ° C under reflux, 1 h;
6. (vi) DIPEA, BF ₃ • OEt ₂ , DCM, RT, 2 h.

The BODIPYs with an alkyl side chain at the peripheral benzyl para position (R = h, i) are according to the synthesis according to 1 with the corresponding boronic acid 11 synthesized.

For the synthesis of BODIPYs with peripheral thiophene rings (R = j, k) 5-methylthiophene-2-boronic acid and 5-ethylthiophene-2-boronic acid are used as starting material.

BODIPYs with a fluorinated alkyl chain at the meso position are made from 15th synthesized using penta-fluoro-propionic acid / penta-fluoropropionic acid anhydride and hepta-fluoro-butyric acid / hepta-fluorobutyric acid anhydride under the same reaction conditions. For the synthesis of where R = h, i, TFA are used for decarboxylation and penta-fluoro-propionic acid / hepta-fluorobutyric acid anhydride for dimerization.

In one embodiment of the invention, X1 and X2 are each O or S, and Y1 and Y2 are each O or S, where X1 and X2 are preferably O and Y1 and Y2 are S.

In a further embodiment of the invention, R4 is equal to R5, and R6 is equal to R7, and / or R9 is equal to R12, R10 is equal to R13 and R11 is equal to R14.

In a further embodiment of the invention, R4 and R5 are H, and R6 and R7 are H.

In a further embodiment of the invention, R9 and R10, or R10 and R11, and / or R12 and R13, or R13 and R14 each together form a heterocyclic 5-ring or homocyclic or heterocyclic 6-ring with at least one heteroatom selected from the group consisting of from S, O and N.

In a further embodiment of the invention, the compound is the compound of the formula II

2 shows a schematic representation of an optoelectronic component 1 as a single solar cell in one embodiment. In an alternative embodiment, a tandem or multiple solar cell is also conceivable.

The optoelectronic component 1 comprises a first electrode 2 , a second electrode 3 and a shift system 4th , the layer system 4th between the first electrode 2 and the second electrode 3 is arranged. In this case, at least one layer of the layer system has 4th at least one compound of the general formula I. In one embodiment, an optoelectronic component is used 1 consisting of a sample on glass 9 with transparent ground contact ITO (M) (anode) 2 , a layer of fullerene C ₆₀ 5, a 1: 1 mixed layer of compound II with fullerene C ₆₀ 6, a p-doped hole transport layer made of Di-NPB and NDP9 7 and a cover contact made of aluminum 3 made, the mixed layer 6th from compound II and C _{60 is} deposited at a substrate temperature of 110 ° C. The photoactive layer 6th exhibits the compound of formula II for the absorption of light in a certain wavelength range.

The manufacture of the optoelectronic component 1 can be carried out by evaporation in a vacuum, with or without carrier gas, or processing from a solution or suspension, such as for example in coating or printing. Individual layers can also be applied by sputtering. It is preferred to produce the layers by evaporation in a vacuum.

In one embodiment of the invention, the layer system has 4th at least one photoactive layer 6th on, wherein the at least one photoactive layer 6th the compound II has.

In a further embodiment of the invention, the layer system has 4th a photoactive layer 6th and an electron transport layer 5 on.

In a further embodiment of the invention, the layer system has 4th at least two, preferably at least three, or preferably at least four photoactive layers 6th on.

In a further embodiment of the invention, the photoactive layer containing the compound II borders 6th to at least one charge carrier transport layer 5 , 7th on, the charge carrier transport layer 5 , 7th is preferably doped, partially doped or undoped.

In a further configuration of the invention, the optoelectronic component is 1 a solar cell, an FET, an LED or a photodetector, preferably an organic solar cell, an OFET, an OLED or an organic photodetector.

In a further embodiment of the invention, the photoactive layer is 6th formed as a mixed layer of the compound II and at least one further compound, or as a mixed layer of the compound II and at least two further compounds.

3 shows a graphic representation of a current-voltage curve, a spectral external quantum yield and the fill factor of an optoelectronic component with compound II.

The scheme of the spectral external quantum yield is defined as the number of electrons removed per incident photon. It is clearly shown that both C60 and compound II are photoactive.

The fill factor FF of the optoelectronic component with compound II is 65.6%, the open circuit voltage U _OC = 0.76 V and the short circuit current Jsc 8.9 mA / cm ² , which confirms a well-functioning solar cell. Out 3 it can also be seen that the fill factor and the voltage also increase with increasing irradiance.

The open circuit voltage U _oc , which reaches higher values through the use of the compounds according to the invention, serves as an important parameter in optoelectronic components. The open circuit voltage U _oc results from the relative position of the energy levels of the donor and acceptor material, the energy levels of which can be varied if necessary by suitable electron-withdrawing or electron-donating groups so that the energy loss during electron transfer is reduced and the open circuit voltage is increased.

The cell efficiency η of a solar cell with the irradiated area A and the irradiance E _{e is} calculated from the fill factor FF, the open circuit voltage U _oc , and the short circuit current j _sc according to: $\eta =\frac{\mathrm{F.}\mathrm{F.}{U}_{O\mathrm{C.}}{j}_{\mathrm{S.}\mathrm{C.}}}{\mathrm{A.}{\mathrm{E.}}_e}.$

The cell efficiency of the optoelectronic component, in particular the solar cell, with compound II is 4.43%.

A photoactive layer of a solar cell with compound II leads to improved saturation compared to a solar cell with compound III (LUMO offset) and a voltage increased by 0.06 V (see 5 ).

A significant increase in the voltage U _oc of more than 0.05 V was shown in the case of high-rate vaporization with compound II. In contrast, the opposite behavior is observed with conventional compounds. This effect can also be observed to a lesser extent for compound IV (see 7th ).

4th Fig. 13 shows a graph of an absorption spectrum of Compound II in comparison with Compound III.

The comparison of the film absorption spectra of the compounds II and III shows a steeper course of the absorption for compound II compared to compound III in the bathochromic range. As a result, a better energetic addition of the compound II to the acceptor material C60 is achieved, the open circuit voltage U _oc remaining the same. The absorption of compound II is more favorable in the red wavelength range compared to compound III, ie the LUMO is energetically more favorable to the HOMO of C60.

The compound of formula II is a particularly good absorber in the wavelength range from 600 to 900 nm. Surprisingly, the absorption spectrum of II could be improved by replacing only CF ₃ with C ₂ F _{5 in} such a way that a compound with poor properties for organic solar cells a compound with excellent properties for organic solar cells was obtained.

5 shows a graphic representation of a current-voltage curve, a spectral external quantum yield and the fill factor of an optoelectronic component with the compound III.

An optoelectronic component with compound III results in a good solar cell, but with reduced saturation compared to compound II (LUMO offset) (see 3 ). In an optoelectronic component with connection III, the fill factor FF = 66.2%, the open-circuit voltage U _OC = 0.70 V and the short-circuit current j _SC = 7.5 mA / cm ² . The cell efficiency of such an optoelectronic component, in particular a solar cell, with compound III is 3.46%.

However, the use of compound III leads to a slight increase in the voltage in solar cells compared to compound II (see 3 ). Compound II saturation and fill factor are improved in comparison. As a result, a gain in efficiency of a solar cell with compound II is achieved.

6th shows a graph of absorption spectra of compounds IV and V.

Compound IV also represents a compound of the BODIPYs according to the invention with a C ₂ F ₅ residue on the central 6-ring.

An optoelectronic component with the connection V leads to a slight increase in the voltage in solar cells. The compound V is not a compound according to the invention, since instead of the C ₂ F ₅ group there is a CF ₃ group on the central 6-ring.

A comparison of the absorption spectra of the compound V (with CF ₃ ) and of the compound IV (with C ₂ F ₅ ) shows a steeper course in the bathochromic region at the edges of the absorption in the case of compound IV compared to compound V. This behavior of compound IV is clearly visible, but not as pronounced in comparison to compound II (see 3 ).

7th shows a graphical representation of a current-voltage curve, a spectral external quantum yield and the fill factor of an optoelectronic component with the compound IV.

In an optoelectronic component with connection IV, the fill factor FF = 65.0%, the open-circuit voltage Uoc = 0.75 V and the short-circuit current j _SC 8.5 mA / cm ² . The cell efficiency of such an optoelectronic component, in particular a solar cell, with compound IV is 4.14%.

An optoelectronic component with the connection IV shows an improved open circuit voltage U _oc of 0.75 V compared to connection VU _oc of 0.71 V, in connection with a steeper curve in the edge area of the absorption and a LUMO offset.

In 7th it can be seen that the fill factor and the voltage for compound IV also increase with increasing irradiance. A slight increase in the no-load voltage U _oc can also be observed.

8th shows a graphic representation of a current-voltage curve, a spectral external quantum yield and the fill factor of an optoelectronic component V.

In an optoelectronic component with connection V, the fill factor FF = 68.1%, the open circuit voltage U _oc 0.71 V and the short circuit current j _SC = 7.3 mA / cm ² . The cell efficiency of such an optoelectronic component, in particular a solar cell, with the connection V is 3.52%.

An optoelectronic component with connection V leads to an acceptable solar cell, but without an increase in voltage compared to connection III, or as shown above with connection II (see 3 ).

9 shows a graphic representation of a current-voltage curve, a spectral external quantum yield and the fill factor of an optoelectronic component with the compound VI.

Compound VI (not according to the invention) has a similar structure to compound III, but without terminal methyl groups.

Compared to compound II, compound VI shows a less suitable absorption spectrum for optoelectronic components, in particular for solar cells.

In an optoelectronic component with connection VI, the fill factor is FF = 50.6%, the open circuit voltage U _OC = 0.76 V and the short circuit current j _SC = 4.6 mA / cm ² . The cell efficiency of such an optoelectronic component, in particular a solar cell, with compound VI is 1.77%.

The optoelectronic component with compound VI shows a significantly poorer cell efficiency compared to the solar cell with compound II.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• WO 2006/092134 A1 [0010]
• WO 2006/111511 A1 [0011]
• WO 2008/145172 A1 [0012]
• WO 2007/126052 A1 [0014, 0061]

Non-patent literature cited

• Li et. al: Small Molecule Near-Infrared Boron Dipyrromethene Donors for Organic Tandem Solar Cells, J. Am. Chem. Soc., 2017, 139, 13636-13639. or J. Mater. Chem. A, 2018,6, 18583-18591 [0061]

Claims (11)

Compound of the general formula I.

characterized in that • R4 and R5 are each independently selected from the group consisting of H, alkyl, fluorinated alkyl, partially fluorinated alkyl, alkoxy, amino, and aryl; • R6 and R7 are each independently selected from the group consisting of H, alkoxy, alkyl, fluorinated alkyl, partially fluorinated alkyl, and amino; • R9, R10, R11, R12, R13 and R14 are each independently selected from the group consisting of H, unsubstituted alkyl, substituted alkyl, alkoxy, amino, aryl and heteroaryl, and / or R9 and R10 or R10 and R11, and / or R12 and R13 or R13 and R14 each together form a heterocyclic or homocyclic 5-ring or 6-ring; • X1 and X2 are each independently O or S; and • Y1 and Y2 are each independently selected from the group consisting of O, S and N-R8, where R8 is H or alkyl. Connection after Claim 1 , characterized in that X1 and X2 are each O or S, and Y1 and Y2 are each O or S, with preferably X1 and X2 being O and Y1 and Y2 being S. Connection after Claim 1 or 2 , characterized in that R4 is R5, and R6 is R7, and / or R9 is R12, R10 is R13 and R11 is R14. A compound according to any one of the preceding claims, characterized in that R4 and R5 are H and R6 and R7 are H. Compound according to one of the preceding claims, characterized in that R9 and R10, or R10 and R11, and / or R12 and R13, or R13 and R14 each together a heterocyclic 5-ring or homocyclic or heterocyclic 6-ring with at least one heteroatom selected from the group consisting of S, O and N. Compound according to any one of the preceding claims, characterized in that the compound is the formula II

Optoelectronic component comprising a first electrode, a second electrode and a layer system, the layer system being arranged between the first electrode and the second electrode, characterized in that at least one layer of the layer system has at least one compound of the general formula I according to one of the Claims 1 to 6th having. Optoelectronic component according to Claim 7 , characterized in that the layer system has at least one photoactive layer, the at least one photoactive layer having the at least one compound of the general formula I. Optoelectronic component according to Claim 7 or 8th , characterized in that the layer system has at least two, preferably at least three, or preferably at least four photoactive layers. Optoelectronic component according to one of the Claims 7 to 9 , characterized in that the optoelectronic component is a solar cell, an FET, an LED or a photodetector, preferably an organic solar cell, an OFET, an OLED or an organic photodetector. Optoelectronic component according to one of the Claims 7 to 10 , characterized in that the photoactive layer is designed as a mixed layer of the at least one compound of the general formula I and at least one further compound, or as a mixed layer of the at least one compound of the general formula I and at least two further compounds.

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