Organic Electronic Device Comprising a Compound of Formula (I), Display Device Comprising the Organic Electronic Device as Well as Compounds of Formula (I) for Use in Organic Electronic Devices

Abstract

The present invention relates to an organic electronic device comprising a semiconductor layer which comprises a compound of formula (1).

Claims

1. An organic electronic device comprising an anode, a cathode, at least one photoactive layer and at least one semiconductor layer, wherein the at least one semiconductor layer is arranged between the anode and the at least one photoactive layer; and wherein the at least one semiconductor layer comprises a compound of Formula (1): ##STR00025## wherein M is a metal ion x is the valency of M B.sup.1 is selected from substituted or unsubstituted C.sub.1 to C.sub.16 alkyl, R.sup.1 to R.sup.5 are independently selected from H, F, CN, halogen, substituted or unsubstituted C.sub.1 to C.sub.6 alkyl, substituted or unsubstituted C.sub.6 to C.sub.12 aryl, substituted or unsubstituted C.sub.3 to C.sub.12 heteroaryl, wherein the substituents on B.sup.1 and/or R.sup.1 to R.sup.5 selected from D, C.sub.6 aryl, C.sub.3 to C.sub.9 heteroaryl, C.sub.1 to C.sub.6 alkyl, C.sub.1 to C.sub.6 alkoxy, C.sub.3 to C.sub.6 branched alkyl, C.sub.3 to C.sub.6 cyclic alkyl, C.sub.3 to C.sub.6 branched alkoxy, C.sub.3 to C.sub.6 cyclic alkoxy, partially or perfluorinated C.sub.1 to C.sub.16 alkyl, partially or perfluorinated C.sub.1 to C.sub.16 alkoxy, partially or perdeuterated C.sub.1 to C.sub.6 alkyl, partially or perdeuterated C.sub.1 to C.sub.6 alkoxy, COR.sup.6, COOR.sup.6, halogen, F or CN; and where at least one of R.sup.1 to R.sup.5 is selected from substituted or unsubstituted C.sub.1 to C.sub.6 alkyl or CN.

2. The organic electronic device of claim 1, whereby the substituents on B.sup.1 or R.sup.1 to R.sup.5 are selected from halogen, C.sub.1 to C.sub.3 perhalogenated alkyl or alkoxy, or —(O).sub.l—C.sub.mH.sub.2m—C.sub.nHal.sub.n2n+1 with l=0 or 1, m=1 or 2 and n=1 to 3 and Hal=halogen.

3. The organic electronic device of claim 1, whereby at least one of B.sup.1 or R.sup.1 to R.sup.5 is substituted alkyl and the substituents of the alkyl moiety are fluorine with the number n.sub.F (of fluorine substituents) and n.sub.H (of hydrogens) follow the equation: n.sub.F>n.sub.H+2.

4. The organic electronic device of claim 1, whereby at least one of B.sup.1 or R.sup.1 to R.sup.5 perfluorinated alkyl.

5. The organic electronic device of claim 1, whereby at least one of R.sup.1 to R.sup.5 is trifluoromethyl.

6. The organic electronic device of claim 1, whereby M has an atomic mass of ≥22 Da.

7. The organic electronic device of claim 1, whereby M is selected from a metal ion wherein the corresponding metal has an electronegativity value according to Allen of less than 2.4.

8. The organic electronic device of claim 1, whereby the compound of formula (1) is free of alkoxy, COR.sup.6 and/or COOR.sup.6 groups.

9. The organic electronic device of claim 1, whereby the anion of compound (1) is selected from A-1 to A-29: ##STR00026## ##STR00027## ##STR00028## ##STR00029## ##STR00030##

10. The organic electronic device of claim 1, whereby the at least one semiconductor layer is non-emissive.

11. The organic electronic device of claim 1, whereby at least one of the semiconductor layers is a hole-injection layer, which consists essentially of the compound of formula (1).

12. The organic electronic device of claim 1, whereby at least one of the at least one semiconductor layers further comprises a substantially covalent matrix compound.

13. The electronic organic device of claim 1, whereby the electronic organic device is an electroluminescent device.

14. A display device comprising an organic electronic device according of claim 1.

15. A compound of formula (1a): ##STR00031## Wherein M is a metal ion x is the valency of M B.sup.1 is selected from substituted or unsubstituted C.sub.1 to C.sub.16 alkyl, R.sup.1 to R.sup.5 are independently selected from H, F, CN, halogen, substituted or unsubstituted C.sub.1 to C.sub.6 alkyl, substituted or unsubstituted C.sub.6 to C.sub.12 aryl, substituted or unsubstituted C.sub.3 to C.sub.12 heteroaryl, wherein the substituents on B.sup.1 and/or R.sup.1 to R.sup.5 selected from D, C.sub.6 aryl, C.sub.3 to C.sub.9 heteroaryl, C.sub.1 to C.sub.6 alkyl, C.sub.1 to C.sub.6 alkoxy, C.sub.3 to C.sub.6 branched alkyl, C.sub.3 to C.sub.6 cyclic alkyl, C.sub.3 to C.sub.6 branched alkoxy, C.sub.3 to C.sub.6 cyclic alkoxy, partially or perfluorinated C.sub.1 to C.sub.16 alkyl, partially or perfluorinated C.sub.1 to C.sub.16 alkoxy, partially or perdeuterated C.sub.1 to C.sub.6 alkyl, partially or perdeuterated C.sub.1 to C.sub.6 alkoxy, COR.sup.6, COOR.sup.6, halogen, F or CN; and where at least one of R.sup.1 to R.sup.5 is selected from substituted or unsubstituted C.sub.1 to C.sub.6 alkyl or CN and wherein the following compounds are excluded where all of the following is fulfilled: M is Li or K; x is 1; B.sup.1 is CF.sub.3; R.sup.1, R.sup.3, and R.sup.5 are H; R.sup.2 and R.sup.4 are CF.sub.3.

Description

DESCRIPTION OF THE DRAWINGS

[0250] The aforementioned components, as well as the claimed components and the components to be used in accordance with the invention in the described embodiments, are not subject to any special exceptions with respect to their size, shape, material selection and technical concept such that the selection criteria known in the pertinent field can be applied without limitations.

[0251] Additional details, characteristics and advantages of the object of the invention are disclosed in the dependent claims and the following description of the respective figures which in an exemplary fashion show preferred embodiments according to the invention. Any embodiment does not necessarily represent the full scope of the invention, however, and reference is made therefore to the claims and herein for interpreting the scope of the invention. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the present invention as claimed.

[0252] FIG. 1 is a schematic sectional view of an organic light-emitting diode (OLED), according to an exemplary embodiment of the present invention;

[0253] FIG. 2 is a schematic sectional view of an organic light-emitting diode (OLED), according to an exemplary embodiment of the present invention;

[0254] FIG. 3 is a schematic sectional view of an organic light-emitting diode (OLED), according to an exemplary embodiment of the present invention.

[0255] FIG. 1 is a schematic sectional view of an organic light-emitting diode (OLED) 100, according to an exemplary embodiment of the present invention. The OLED 100 includes a substrate 110. On the substrate 110 an anode 120 is disposed. On the anode 120 a semiconductor layer comprising a compound of formula (1) is disposed and thereon a hole transport layer 140. Onto the hole transport layer 140 an emission layer 150 and an cathode electrode 190, exactly in this order, are disposed.

[0256] FIG. 2 is a schematic sectional view of an organic light-emitting diode (OLED) 100, according to an exemplary embodiment of the present invention. The OLED 100 includes a substrate 110, a first electrode 120, a semiconductor layer comprising a compound of formula (1) 130, a hole transport layer (HTL) 140, an emission layer (EML) 150, an electron transport layer (ETL) 161. The electron transport layer (ETL) 161 is formed directly on the EML 150. Onto the electron transport layer (ETL) 161 a cathode electrode 190 is disposed.

[0257] Instead of a single electron transport layer 161, optional an electron transport layer stack (ETL) can be used.

[0258] FIG. 3 is a schematic sectional view of an OLED 100, according to another exemplary embodiment of the present invention. FIG. 3 differs from FIG. 2 in that the OLED 100 of FIG. 3 comprises a hole blocking layer (HBL) 155 and an electron injection layer (EIL) 180.

[0259] Referring to FIG. 3 the OLED 100 includes a substrate 110, an anode electrode 120, a semiconductor layer comprising a compound of formula (1) 130, a hole transport layer (HTL) 140, an emission layer (EML) 150, a hole blocking layer (HBL) 155, an electron transport layer (ETL) 161, an electron injection layer (EIL) 180 and a cathode electrode 190. The layers are disposed exactly in the order as mentioned before.

[0260] In the description above the method of manufacture an OLED of the present invention is started with a substrate 110 onto which an anode electrode 120 is formed, on the anode electrode 120, an hole injection layer 130, hole transport layer 140, an emission layer 150, optional a hole blocking layer 155, optional at least one electron transport layer 161, optional at least one electron injection layer 180, and a cathode electrode 190 are formed, exactly in that order or exactly the other way around.

[0261] While not shown in FIG. 1, FIG. 2 and FIG. 3, a sealing layer may further be formed on the cathode electrodes 190, in order to seal the OLEDs 100. In addition, various other modifications may be applied thereto.

[0262] Hereinafter, one or more exemplary embodiments of the present invention will be described in detail with, reference to the following examples. However, these examples are not intended to limit the purpose and scope of the one or more exemplary embodiments of the present invention.

DETAILED DESCRIPTION

[0263] The invention is furthermore illustrated by the following examples which are illustrative only and non-binding.

[0264] The compounds of the present invention can be made by methods known to the skilled person in the art, some general procedures with exemplified educts are described in the following:

[0265] General Procedure for Synthesis of Sulfonamide Ligand

[0266] 3,5-bis(trifluoromethyl)sulfonylchloride was dissolved in dry acetone (ca. 10 ml/g) and 3 eq of K.sub.2CO.sub.3 was added. The mixture was cooled in an ice bath. 1eq of the desired B.sup.1 sulfonamide was added in counter flow. The mixture was stirred at room temperature, until .sup.19F-NMR shows complete conversion. The solid was filtered off and washed with acetone. The solvent was removed under reduced pressure. The residue was treated with ice-cold half concentrated sulfuric acid and extracted with diethyl ether. The combined organic layers were washed with a small amount of water, dried over sodium sulfate and the solvent removed under reduced pressure. The residue was distilled from bulb to bulb in high vacuum.

[0267] General Procedure for Compounds of Formula (I) Wherein M is Cu(II)

[0268] The sulfonamide ligand was dissolved in water (ca 10 ml/g) and 0.5 eq Cu(OAc).sub.2 was added. The mixture was stirred until a clear blue solution was obtained. The solvent was removed under reduced pressure. Residual acetic acid was removed by repeated adding of toluene and removal of solvents under reduced pressure. The crude material was purified by sublimation.

[0269] General Procedure for Compounds of Formula (I) Wherein M is Mn(II)

[0270] The sulfonamide ligand was dissolved in MeOH (ca. 10 ml/g) and carefully securated by bubbling nitrogen through the vigorously stirred solution. 0.5 eq metallic Mn powder was added and the mixture was stirred overnight at room temperature. The solvent was removed under reduced pressure and the remaining oil was stirred in degassed water to obtain a solid. The crude material was purified by sublimation.

[0271] General Procedure for Compounds of Formula (I) Wherein M is Mg(II)

[0272] The sulfonamide ligand was suspended under inert conditions in dry toluene (ca. 5 ml/g) and dissolved at 50° C. 0.5 eq. MgBu.sub.2 solution in heptane was added dropwise. The reaction mixture was stirred at 50° C. for 2 h. After cooling, the product was precipitated with dry hexane (ca. 10 ml/g). The precipitate was filtered off under inert conditions, washed with dry hexane and dried in high vacuum. The crude product was purified by sublimation.

As comparative examples, the following compounds were used:

TABLE-US-00003 Comparative example No Structure 1 Cu (TFSI).sub.2 2 Ag (TFSI) 3 Li (TFSI)

Sublimation Temperature

[0273] Under nitrogen in a glovebox, 0.5 to 5 g compound are loaded into the evaporation source of a sublimation apparatus. The sublimation apparatus consist of an inner glass tube consisting of bulbs with a diameter of 3 cm which are placed inside a glass tube with a diameter of 3.5 cm. The sublimation apparatus is placed inside a tube oven (Creaphys DSU 05/2.1). The sublimation apparatus is evacuated via a membrane pump (Pfeiffer Vacuum MVP 055-3C) and a turbo pump (Pfeiffer Vacuum THM071 YP). The pressure is measured between the sublimation apparatus and the turbo pump using a pressure gauge (Pfeiffer Vacuum PKR 251). When the pressure has been reduced to 10.sup.−5 mbar, the temperature is increased in increments of 10 to 30 K till the compound starts to be deposited in the harvesting zone of the sublimation apparatus. The temperature is further increased in increments of 10 to 30 K till a sublimation rate is achieved where the compound in the source is visibly depleted over 30 min to 1 hour and a substantial amount of compound has accumulated in the harvesting zone.

[0274] The sublimation temperature, also named T.sub.sub1, is the temperature inside the sublimation apparatus at which the compound is deposited in the harvesting zone at a visible rate and is measured in degree Celsius.

[0275] In the context of the present invention, the term “sublimation” may refer to a phase transfer from solid state to gas phase or from liquid state to gas phase.

Decomposition Temperature

[0276] The decomposition temperature, also named T.sub.dec, is determined in degree Celsius.

[0277] The decomposition temperature is measured by loading a sample of 9 to 11 mg into a Mettler Toledo 100 μL aluminum pan without lid under nitrogen in a Mettler Toledo TGA-DSC 1 machine. The following heating program was used: 25° C. isothermal for 3 min; 25° C. to 600° C. with 10 K/min.

[0278] The decomposition temperature was determined based on the onset of the decomposition in TGA.

Rate Onset Temperature

[0279] The rate onset temperature (TRO) is determined by loading 100 mg compound into a VTE source. As VTE source a point source for organic materials may be used as supplied by Kurt J. Lesker Com-pany (www.lesker.com) or CreaPhys GmbH (http://www.creaphys.com). The VTE source is heated at a constant rate of 15 K/min at a pressure of less than 10.sup.−5 mbar and the temperature inside the source measured with a thermocouple. Evaporation of the compound is detected with a QCM detector which detects deposition of the compound on the quartz crystal of the detector. The deposition rate on the quartz crystal is measured in Angstrom per second. To determine the rate onset temperature, the deposition rate is plotted against the VTE source temperature. The rate onset is the temperature at which noticeable deposition on the QCM detector occurs. For accurate results, the VTE source is heated and cooled three time and only results from the second and third run are used to determine the rate onset temperature.

[0280] To achieve good control over the evaporation rate of an organic compound, the rate onset temperature may be in the range of 200 to 255° C. If the rate onset temperature is below 200° C. the evaporation may be too rapid and therefore difficult to control. If the rate onset temperature is above 255° C. the evaporation rate may be too low which may result in low tact time and decomposition of the organic compound in VTE source may occur due to prolonged exposure to elevated temperatures.

[0281] The rate onset temperature is an indirect measure of the volatility of a compound. The higher the rate onset temperature the lower is the volatility of a compound.

Reduction Potential

[0282] The reduction potential is determined by cyclic voltammetry with potenioststic device Metrohm PGSTAT30 and software Metrohm Autolab GPES at room temperature. The redox potentials given at particular compounds were measured in an argon de-aerated, dry 0.1M THF solution of the tested substance, under argon atmosphere, with 0.1M tetrabutylammonium hexafluorophosphate supporting electrolyte, between platinum working electrodes and with an Ag/AgCl pseudo-standard electrode (Metrohm Silver rod electrode), consisting of a silver wire covered by silver chloride and immersed directly in the measured solution, with the scan rate 100 mV/s. The first run was done in the broadest range of the potential set on the working electrodes, and the range was then adjusted within subsequent runs appropriately. The final three runs were done with the addition of ferrocene (in 0.1M concentration) as the standard. The average of potentials corresponding to cathodic and anodic peak of the studied compound, after subtraction of the average of cathodic and anodic potentials observed for the standard Fc.sup.+/Fc redox couple, afforded finally the values reported above. All studied compounds as well as the reported comparative compounds showed well-defined reversible electrochemical behaviour.

Calculated HOMO and LUMO

[0283] The HOMO and LUMO are calculated with the program package TURBOMOLE V6.5 (TURBOMOLE GmbH, Litzenhardtstrasse 19, 76135 Karlsruhe, Germany). The optimized geometries and the HOMO and LUMO energy levels of the molecular structures are determined by applying the hybrid functional B3LYP with a 6-31G* basis set in the gas phase. If more than one conformation is viable, the conformation with the lowest total energy is selected. The HOMO and LUMO levels are recorded in electron volt (eV).

General Procedure for Fabrication of OLEDs

[0284] For OLEDs, see Examples 5 and 6, Examples 10 to 12, and comparative example 3 in Table 3, a 15Ω/cm.sup.2 glass substrate with 90 nm ITO (available from Corning Co.) was cut to a size of 50 mm×50 mm×0.7 mm, ultrasonically washed with isopropyl alcohol for 5 minutes and then with pure water for 5 minutes, and washed again with UV ozone for 30 minutes, to prepare the anode.

[0285] Then, 92 mol.-% Biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine (CAS 1242056-42-3) with 8 mol.-% compound of formula (1) was vacuum deposited on the anode, to form a HIL having a thickness of 10 nm. In comparative examples 4 and 5, the compounds shown in Table 3 were used in place of compounds of formula (1).

[0286] Then, Biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl) phenyl]-amine was vacuum deposited on the HIL, to form a first HTL having a thickness of 128 nm.

[0287] Then N,N-bis(4-(dibenzo[b,d]furan-4-yl)phenyl)-[1,1′:4′,1″-terphenyl]-4-amine (CAS 1198399-61-9) was vacuum deposited on the HTL, to form an electron blocking layer (EBL) having a thickness of 5 nm.

[0288] Then 97 vol.-% H09 (Sun Fine Chemicals, Korea) as EML host and 3 vol.-% BD200 (Sun Fine Chemicals, Korea) as fluorescent blue dopant were deposited on the EBL, to form a first blue-emitting emission layer (EML) with a thickness of 20 nm.

[0289] Then a hole blocking layer is formed with a thickness of 5 nm by depositing 2-(3′-(9,9-dimethyl-9H-fluoren-2-yl)-[1,1′-biphenyl]-3-yl)-4,6-diphenyl-1,3,5-triazine on the emission layer.

[0290] Then, the electron transporting layer having a thickness of 31 nm is formed on the hole blocking layer by depositing 4′-(4-(4-(4,6-diphenyl-1,3,5-triazin yl)phenyl)naphthalen-1-yl)-[1,1′-biphenyl]-4-carbonitrile and LiQ in a ratio of 50:50 vol.-%.

[0291] Al is evaporated at a rate of 0.01 to 1 Å/s at 10.sup.−7 mbar to form a cathode with a thickness of 100 nm.

[0292] A cap layer of Biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine is formed on the cathode with a thickness of 75 nm.

[0293] The OLED stack is protected from ambient conditions by encapsulation of the device with a glass slide. Thereby, a cavity is formed, which includes a getter material for further protection.

[0294] To assess the performance of the inventive examples compared to the prior art, the current efficiency is measured at 20° C. The current-voltage characteristic is determined using a Keithley 2635 source measure unit, by sourcing a voltage in V and measuring the current in mA flowing through the device under test. The voltage applied to the device is varied in steps of 0.1V in the range between 0V and 10V. Likewise, the luminance-voltage characteristics and CIE coordinates are determined by measuring the luminance in cd/m.sup.2 using an Instrument Systems CAS-140CT array spectrometer (calibrated by Deutsche Akkreditierungsstelle (DAkkS)) for each of the voltage values. The cd/A efficiency at 10 mA/cm.sup.2 is determined by interpolating the luminance-voltage and current-voltage characteristics, respectively.

[0295] Lifetime LT of the device is measured at ambient conditions (20° C.) and 30 mA/cm.sup.2, using a Keithley 2400 sourcemeter, and recorded in hours.

[0296] The brightness of the device is measured using a calibrated photo diode. The lifetime LT is defined as the time till the brightness of the device is reduced to 97% of its initial value.

[0297] To determine the voltage stability over time U(100h)−(1h) and U(100h-50h), a current density of at 30 mA/cm.sup.2 was applied to the device. The operating voltage was measured after 1 hour, after 50 hours and after 100 hours, followed by calculation of the voltage stability for the time period of 1 hour to 100 hours and for a time period of 50 hours to 100 hours.

Technical Effect of the Invention

[0298] In order to investigate the usefulness of the inventive compound preferred materials were tested in view of their thermal properties

[0299] As materials for organic electronics are typically purified by sublimation, a large offset between decomposition and sublimation temperature T.sub.dec-T.sub.sub1 are highly desirable. Thereby, a high sublimation rate may be achievable.

TABLE-US-00004 TABLE 2 Properties of compounds of formula (1) and comparative examples 1 and 2: Name T.sub.dec [° C.] T.sub.dec-T.sub.sub1 [° C.] Comparative Cu (TFSI).sub.2 180 10 example 1 Comparative Ag (TFSI) 320 5-10° C. example 2 Example 1 A1 >350 >41 Example 2 A2 ≥265 ≥30 Example 3 A3 >350 >41 Example 4 A5 >350 ≥30 Example 7 A6 >350 ≥30 Example 8 A7 >310 ≥108 Example 9 A8 >340 >20

[0300] In Table 2 are shown the temperature at which thermal decomposition is observed (T.sub.dec), difference between decomposition and sublimation temperature and yield after purification through sublimation.

[0301] The decomposition temperature of Cu (TFSI).sub.2 is 180° C., see comparative example 1 in Table 2. The difference between decomposition and sublimation temperature is 10° C. A sublimation rate which is suitable for mass production cannot be achieved as a substantial amount of compound decomposes before it sublimes.

[0302] The decomposition temperature of Ag (TFSI) is 320° C., see comparative example 2 in Table 2. Comparative example 2 differs from comparative example 1 in the metal ion (Ag.sup.+ instead of Cu.sup.2+). The decomposition temperature is increased from 180° C. in comparative example 1 to >320° C. The difference between decomposition and sublimation temperature is 5 to 10° C. Therefore, a high rate in sublimation cannot be achieved easily without decomposition.

[0303] Surprisingly, for compounds of formula (1) the temperature difference between decomposition and sublimation temperature is at least 30° C., see examples 1 to 4 and examples 7 to 9 in Table 2.

[0304] As materials for organic electronics are typically purified by sublimation, a high decomposition temperature, a large offset between decomposition and sublimation temperature is highly desirable. Thereby, a high sublimation rate may be achievable.

[0305] In Table 3 are shown the properties of organic electronic devices comprising compounds of formula (1) and comparative example 3.

TABLE-US-00005 TABLE 3 Properties of organic electronic device comprising compound of formula 1 and comparative examples 4 and 5 Chemical structure of the U(100 h)- U(100 h)- compound (1 h) @ (50 h) @ contained 30 mA/cm.sup.2 30 mA/cm.sup.2 in the device [V] [V] Comparative Li (TFSI) 1.11 0.33 example 3 Example 5 A2 0.04 0.02 Example 6 A5 0.06 0.04 Example 10 A6 0.03 0.02 Example 11 A7 0.04 0.01 Example 12 A8 0.04 0.02

[0306] A current density of 30 mA/cm.sup.2 was applied to the devices for 1 hour to achieve stable performance. Then, the change in operating voltage over 100 hours was determined.

[0307] In comparative example 3, Li (TFSI) was used. The operating voltage increases by 1.11 V over 100 hours.

[0308] Surprisingly, it was found that in devices comprising a compound of formula (1), the operating voltage increases much less over time compared to the comparative examples.

[0309] The beneficial effect is even more pronounced when the voltage change between 50 and 100 hours is measured. In comparative example 3, the operating voltage increases by 0.33 V.

[0310] In examples comprising compound of formula (I), the operating voltage increases only by 0.02 and 0.04 V, respectively. In examples 10 to 12 comprising compound of formula (I), the operating voltage increases only by 0.01 to 0.02 V.

[0311] A low increase or even decrease in operating voltage over time is highly desirable, as the power consumption over time does not increase. Low power consumption is important for long battery life, in particular in mobile devices.

[0312] Thereby, an improvement in performance has been achieved even for stronger oxidizing metal complexes. Without being bound by theory, it is believed that stronger oxidizing metal complexes may enable more effective hole injection into an organic electronic device. Therefore, it is highly desirable to provide stronger oxidizing metal complexes in a form which is suitable for mass production of organic electronic devices.

[0313] The particular combinations of elements and features in the above detailed embodiments are exemplary only; the interchanging and substitution of these teachings with other teachings in this and the patents/applications incorporated by reference are also expressly contemplated. As those skilled in the art will recognize, variations, modifications, and other implementations of what is described herein can occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the foregoing description is by way of example only and is not intended as limiting. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. The invention's scope is defined in the following claims and the equivalents thereto. Furthermore, reference signs used in the description and claims do not limit the scope of the invention as claimed.