Formulation containing an organic semiconductor and a metal complex

Abstract

The present invention relates to formulations which comprise at least one organic semiconductor, at least one metal complex and at least one solvent and the use of these formulations in electronic devices, in particular organic electroluminescent devices.

Claims

1. A formulation comprising at least one organic semiconductor, at least one metal complex and at least one organic solvent, wherein the solubility at 20 C. of the metal complex is 5 g/l in at least one organic solvent and the solubility at 20 C. of the organic semiconductor is 10 g/l in at least one organic solvent and wherein at least one organic semiconductor is a polymer comprising at least one structural unit of the following formula (I): ##STR00274## where Ar.sup.1 to Ar.sup.3 is on each occurrence, in each case identically or differently, a mono- or polycyclic, aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R; R is on each occurrence, identically or differently, H, D, F, Cl, Br, I, N(R.sup.1).sub.2, CN, NO.sub.2, Si(R.sup.1).sub.3, B(OR.sup.1).sub.2, C(O)R.sup.1, P(O)(R.sup.1).sub.2, S(O)R.sup.1, S(O).sub.2R.sup.1OSO.sub.2R.sup.1, a straight-chain alkyl, alkoxy or thioalkoxy group having 1 to 40 C atoms or a branched or cyclic alkyl, alkoxy or thioalkoxy group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R.sup.1, where one or more non-adjacent CH.sub.2 groups may be replaced by R.sup.1CCR.sup.1, CC, Si(R.sup.1).sub.2, CO, CS, CNR.sup.1, P(O)(R.sup.1), SO, SO.sub.2, NR.sup.1, O, S or CONR.sup.1 and where one or more H atoms may be replaced by D, F, Cl, Br, I or CN, or a mono- or polycyclic, aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R.sup.1, or an aryloxy or heteroaryloxy group having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R.sup.1, or an aralkyl or heteroaralkyl group having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R.sup.1, or a diarylamino group, diheteroarylamino group or arylheteroarylamino group having 10 to 40 aromatic ring atoms, which may be substituted by one or more radicals R.sup.1, or a crosslinkable group Q, where two or more radicals R may also form a mono- or polycyclic, aliphatic, aromatic and/or benzo-fused ring system with one another; R.sup.1 is on each occurrence, identically or differently, H, D, F or an aliphatic hydrocarbon radical having 1 to 20 C atoms, an aromatic and/or a heteroaromatic hydrocarbon radical having 5 to 20 C atoms, in which, in addition, one or more H atoms may be replaced by F; where two or more substituents R.sup.1 may also form a mono- or polycyclic, aliphatic or aromatic ring system with one another; and the dashed lines represent bonds to adjacent structural units in the polymer, and where at least one of Ar.sup.1, Ar.sup.2 and/or Ar.sup.3 is substituted by a radical R comprising at least 2 C atoms wherein the at least one metal complex comprises a metal atom of group 13 to 15 and a ligand of the following structure ##STR00275## where R.sup.11 and R.sup.12 are selected, identically or differently, from the group consisting of O, S, Se, NH or NR.sup.14, where R.sup.14 is an alkyl or aryl group; where R.sup.14 and R.sup.13 may form a ring with one other; and R.sup.13 is selected from the group consisting of a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms or an alkenyl or alkinyl group having 2 to 40 C atoms or a branched or cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R.sup.1, where in each case one or more non-adjacent CH.sub.2 groups may be replaced by R.sup.1CCR.sup.1, CC, Si(R.sup.1).sub.2, CO, CS, CNR.sup.1, P(O)(R.sup.1), SO, SO.sub.2, NR.sup.1, O, S or CONR.sup.1 and where one or more H atoms may be replaced by D, F, Cl, Br, I or CN, an aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R.sup.1, an aryloxy or heteroaryloxy group having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R.sup.1, or an aralkyl or heteroaralkyl group having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R.sup.1, or a diarylamino group, diheteroarylamino group or arylheteroarylamino group having 10 to 40 aromatic ring atoms, which may be substituted by one or more radicals R.sup.1; where R.sup.13 may form a ring with at least one of the radical R.sup.12; and R.sup.1 is defined above; and wherein the one organic solvent comprises at least two solvents wherein the formulation comprises a first organic solvent which has a boiling point of from 100 C. to 300 C. and a second organic solvent which has a boiling point of from 40 C. to 100 C.

2. The formulation according to claim 1, wherein the solubility at 20 C. of the metal complex is 7.5 g/l, in at least one organic solvent and the solubility at 20 C. of the organic semiconductor is 15 g/l, in at least one organic solvent.

3. The formulation according to claim 1, wherein the first solvent is Benzonitrile, Dimethylformamide, Dimethyl sulfoxide, Toluene, Anisole, Xylene, Chlorbenzene or mixture thereof.

4. The formulation according to claim 1, wherein the second solvent is Tetrahydrofurane, Hexafluorbenzene, Acetonitrile, Acetone, Methanol, Ethylene glycol dimethyl ether, or mixture thereof.

5. The formulation according to claim 1, wherein the proportion of the organic solvent in the formulation is at least 60% by weight, based on the total weight of the formulation.

6. The formulation according to claim 1, wherein at least one organic semiconductor is selected from the group consisting of hole-transport materials (HTM) and hole-injection materials (HIM).

7. The formulation according to claim 1, wherein at least one organic semiconductor is a polymer having a molecular weight (M.sub.w) in the range of 10,000 to 2,000,000 g/mol.

8. The formulation according to claim 1, wherein at least one of Ar.sup.1, Ar.sup.2 and/or Ar.sup.3 according to formula (I) or (I) is in at least one ortho-positions relating to the Nitrogen atom represented in formula (I) or (I), substituted by Ar.sup.4, where Ar.sup.4 is a mono- or polycyclic, aromatic or heteroaromatic ring system with 5 to 60 aromatic ring atoms, which may be substituted by one or more radical R.

9. The formulation according to claim 1 wherein the concentration of the organic semiconductor is in the range of from 10 g/l to 100 g/l, based on the total formulation.

10. The formulation according to claim 1 wherein the concentration of the metal complex is in the range of from 5 g/l to 100 g/l based on the total formulation.

11. A method for the preparation of the formulation according to claim 1 comprising the following steps: a. Preparing a first solution comprising at least one solvent and at least one metal complex and b. Preparing a second solution comprising at least one solvent and at least one organic semiconductor and c. Mixing the first solution obtained in step a) and the second solution obtained in step b) in a specific ratio and forming a formulation by a physical method.

12. A process for the production of an electronic device with a multilayer structure, wherein at least one layer is obtained from the application of the formulation according to claim 1.

13. The process according to claim 12, wherein the formulation is applied by flood coating, dip coating, spray coating, spin coating, screen printing, relief printing, gravure printing, rotary printing, roller coating, flexographic printing, offset printing, slot die coating or nozzle printing.

14. An electronic device obtainable by the process according to claim 12.

15. The electronic device according to claim 14, wherein the electronic device is selected from the group consisting of organic electroluminescent devices, organic integrated circuits, organic field-effect transistors, organic thin-film transistors, organic light-emitting transistors, organic solar cells, organic optical detectors, organic photoreceptors, organic field-quench devices, light-emitting electrochemical cells, organic laser diodes and organic light-emitting diodes.

16. The formulation according to claim 1, wherein the polymer comprises a polymer of the formula ##STR00276##

Description

WORKING EXAMPLES

(1) Part A: Organic Semiconductor

(2) The organic semiconductors (OS) used for the formation of the formulations according to the invention are already described in the prior art and were produced according to the literature instructions.

(3) They are represented in the table below:

(4) TABLE-US-00019 Organic semi- Synthesis con- according ductors Structure to OS1 WO2003/ 048225 WO2010/ 097155 OS2 WO2003/ 048225 OS3 WO2003/ 048225 OS4 WO2003/ 048225 WO2010/ 097155 OS5 WO2003/ 048225 OS6 WO2012- 034627
Part B: Metal Complex

(5) The metal complex used for the formation of the formulations according to the invention are already described in the prior art and were produced according to the literature instructions.

(6) An example is represented in the table below:

(7) TABLE-US-00020 Metal Synthesis complex Structure according to M1 WO 2013/182389
Part C: Formulation

(8) A formulation here is taken to mean a mixture comprising at least one organic semiconductor, at least one metal complex and at least one solvent.

(9) The solubility of a material in a solvent is the highest material-to-solvent ratio in which the solution at 20 C. is clear and stays clear for several hours.

(10) The solubility (g/l) is determined according to the following method:

(11) (1) A known amount of the solvent (for example 100 mL) is put in a container

(12) (2) A defined amount of the material is added and the mixture is stirred with a magnetic stirring bar;

(13) (3) Step (2) is repeated until some of the material does not dissolve despite a vigorous and prolonged stirring.

(14) The solubilities (in g/l) of the various materials in various solvent at 20 C. are listed in the table below.

(15) TABLE-US-00021 Material Solvent OS3 M1 OS5 OS6 LM1 Anisole:Xylene >20 g/l <7.5 g/l >20 g/l >50 g/l (2:1) LM2 Anisole >20 g/l <7.5 g/l >20 g/l 100 g/l LM3 Xylene >20 g/l <7.5 g/l >20 g/l 40 g/l LM4 Chlorobenzene >20 g/l <7.5 g/l >20 g/l LM5 THF >40 g/l >100 g/l >40 g/l >40 g/l LM6 Toluene:THF >50 g/l >30 g/l >50 g/l >50 g/l (9:1) LM7 Hexafluorobenzene 10 g/l 15-20 g/l LM8 Toluene: 40 g/l 15 g/l 40 g/l 30 g/l Hexafluorobenzene (7:3) LM9 Meta- >20 g/l <7.5 g/l >20 g/l difluorobenzene LM10 Fluorobenzene >30 g/l <7.5 g/l >30 g/l LM11 Acetonitrile <5 g/l <10 g/l <5 g/l LM12 Benzonitrile >20 g/l LM13 Acetone <5 g/l >20 g/l <5 g/l LM14 DMF <2 g/l >40 g/l <2 g/l 10 g/l LM15 Toluene:DMF 30 g/l 15 g/l 30 g/l 25 g/l (8:2) LM16 DMSO <2 g/l >20 g/l <2 g/l 10 g/l LM17 Methanol <5 g/l >20 g/l <5 g/l LM18 Toluene:Methanol 35 g/l 20 g/l 35 g/l 30 g/l (8:2) LM19 EGDME <5 g/l >20 g/l <5 g/l LM20 Toluene >40 g/l <7.5 g/l >40 g/l 60 g/l
Part D: Device Examples

(16) Formulations according to the invention, which comprise at least one organic semiconductor, at least one metal complex and at least one solvent, lead to OLEDs which are much easier to produce than OLEDs obtained from vacuum processes, and at the same time still exhibit good properties.

(17) The production of solvent-based OLEDs has already been described in the literature, e.g. in WO 2004/037887 and in WO 2010/097155. The method is adapted to the conditions described below (layer thickness variation, materials).

(18) The formulations according to the invention can be used in two different layer sequences:

(19) Stack A is as follows: Substrate, ITO (50 nm), Hole injection layer (HIL) (200 nm), Cathode.

(20) Stack B is as follows: Substrate, ITO (50 nm), HIL (150 nm), Hole transport layer (HTL) (40 nm) Emissive layer (EML) (30 nm) Electron transport layer (ETL) (20 nm), Cathode.

(21) The substrate consists of glass platelets, which are coated with a structured 50 nm thick ITO (indium tin oxide) layer. The functional layers are then applied onto the coated substrate according to the structures of Stacks A and B.

(22) For the preparation of the hole injection layer, the formulations according to the invention as well as comparative mixtures are used. The comparative mixture according to the prior art comprises a solvent consisting of Anisole: Xylene in the ratio 2:1 (LM1). The typical solid content of such solutions is about 8-35 g/l, when film thicknesses of between 20 nm and 200 nm have to be achieved by means of spin coating. The layers were spin coated in an inert gas atmosphere, in this case argon, and heated for 60 minutes at 180 C. or 220 C.

(23) The hole transport layer in Stack B is formed by thermal evaporation in a vacuum chamber. The materials used in this case are shown in Table D1.

(24) TABLE-US-00022 TABLE D1 Structural formula of the hole-transport material (vacuum processed) HT1

(25) The emissive layer in Stack B is formed by thermal evaporation in a vacuum chamber. In this case, the layer may consist of more than one material, which are deposited by means of co-evaporation in a given volume fraction. A reference such as MB1:SEB (95%:5%) in this case means that the materials MB1 and SEB are present in the layer in a volume fraction of 95%:5%.

(26) The materials used in this case are shown in Table D2.

(27) TABLE-US-00023 TABLE D2 Structural formulae of the materials used in the emissive layer 0 MB1 SEB

(28) The materials for the electron-transport layer are also thermally evaporated in a vacuum chamber and are shown in Table D3. The electron-transport layer consists of the two materials ETM1 and ETM2, which are deposited by means of co-evaporation in a volume fraction of 50%:50%.

(29) TABLE-US-00024 TABLE D3 Structural formulae of the materials used in the hole-blocking and/or electron-transport layers ETM1 ETM2

(30) Furthermore, the cathode is formed by the deposition of a 100 nm thick aluminum layer by means of thermal evaporation.

(31) The exact structure of the OLEDs is shown in Table D4.

(32) TABLE-US-00025 TABLE D4 Structure of the OLEDs HIL weight metal complex ratio T HTL EML Ex. Stack OS (M) (OS:M) solvent [ C.] material composition D1 B OS4 M1 85:15 LM6 180 HT1 MB1 95% SEB 5% D2 A OS5 M1 70:30 LM1 180 D3 A OS1 M1 70:30 LM1 180 D4 A OS5 M1 70:30 LM6 180 D5 A OS1 M1 70:30 LM6 180 D6 A OS6 M1 70:30 LM6 180 D7 A OS3 M1 70:30 LM8 180 D8 A OS4 M1 85:15 LM15 220 D9 A OS2 M1 85:15 LM18 180

(33) The OLEDs are characterized by standard methods. For this purpose, the electroluminescence spectra, the current-voltage-luminance characteristics (IUL characteristics), assuming a Lambertian radiation pattern and in the case of Stack B, the operating lifetime are determined. Data like the operating voltage (in V) and the external quantum efficiency (in %) at a certain brightness are determined from the IUL characteristics. LD80@4000 cd/m.sup.2 corresponds to the lifetime until which the brightness of the OLED drops from an initial brightness of 4000 cd/m.sup.2 to a brightness equal to 80% of the initial intensity, i.e. at 3600 cd m.sup.2.

(34) The properties of the different OLEDs are summarized in Tables D5a and D5b. Examples D2 and D3 were prepared according to the prior art, all the other examples show properties of components according to the invention.

(35) Table D5a shows results of hole-dominated components according to Stack A. In such components, the current is dominated by holes, which is why no recombination with electrons takes place that would lead to luminescence.

(36) TABLE-US-00026 TABLE D5a Current density at U = 3 V Scattering Ex. [mA/cm.sup.2] parameter D2 33 1.1 D3 1 0.9 D4 24 0.2 D5 2 0.1 D6 36 0.2 D7 39 0.4 D8 5 0.2 D9 19 0.3

(37) The scattering parameters in Table D5a correspond to the relative error of the mean value of the current density at U=3V, which corresponds to the standard deviation divided by the mean value.

(38) The results in Table D5a show that the scattering of the current density for components obtained from formulations according to the invention is significantly lower than the scattering of the current density for components obtained from formulations according to the prior art.

(39) TABLE-US-00027 TABLE D5b Efficiency at Voltage at LD80 at 1000 cd/m.sup.2 1000 cd/m.sup.2 4000 cd/m.sup.2 Ex. % EQE [V] [h] D1 7.7 4.5 420

(40) Table D5b shows that the use of formulations according to the invention leads to OLEDs with a good lifetime and efficiency.