Method for Preparing an Organic Semiconducting Layer, a Composition for Use Therein and an Organic Electronic Device

Abstract

The present invention relates to a method for preparing an organic semiconducting layer comprising the steps: a) providing a first composition in a first vacuum thermal evaporation source, the first composition comprising aa) a first organic compound, the first organic compound comprising at least one unsubstituted or substituted C.sub.10-C.sub.30 condensed aryl group and/or at least one unsubstituted or substituted C.sub.3-C.sub.30 heteroaryl group, wherein the one or more substituent(s) if present, are selected from the group consisting of (i) deuterium, (ii) a halogen, (iii) a C.sub.1 to C.sub.22 silyl group, (iv) a C.sub.1 to C.sub.30 alkyl group, (v) a C.sub.1 to C.sub.10 alkylsilyl group, (vi) a C.sub.6 to C.sub.22 arylsilyl group, (vii) a C.sub.3 to C.sub.30 cycloalkyl group, (viii) a C.sub.2 to C.sub.30 heterocycloalkyl group, (ix) a C.sub.6 to C.sub.30 aryl group, (x) a C.sub.2 to C.sub.30 heteroaryl group, (xi) a C.sub.1 to C.sub.30 perfluoro-hydrocarbyl group, or (xii) a C.sub.1 to C.sub.10 trifluoroalkyl group, wherein the first organic compound has i) a dipole moment in the range of ≥0 and ≤2 Debye; and ii) a molecular weight in the range of ≥400 and ≤1,800; and bb) a metal borate compound; b) transferring the first composition from the solid phase into the gas phase in a vacuum chamber; and c) depositing the first composition on a substrate to form the organic semiconducting layer, a composition for use therein, and an organic electronic device prepared this way.

Claims

1. Method for preparing an organic semiconducting layer comprising the steps: a) Providing a first composition in a first vacuum thermal evaporation source, the first composition comprising aa) a first organic compound, the first organic compound comprising at least one unsubstituted or substituted C.sub.10 to C.sub.30 condensed aryl group and/or at least one unsubstituted or substituted C.sub.3 to C.sub.30 heteroaryl group, wherein the one or more substituent(s) if present, are independently selected from the group consisting of (i) deuterium, (ii) a halogen, (iii) a C.sub.1 to C.sub.22 silyl group, (iv) a C.sub.1 to C.sub.30 alkyl group, (v) a C.sub.1 to C.sub.10 alkylsilyl group, (vi) a C.sub.6 to C.sub.22 arylsilyl group, (vii) a C.sub.3 to C.sub.30 cycloalkyl group, (viii) a C.sub.2 to C.sub.30 heterocycloalkyl group, (ix) a C.sub.6 to C.sub.30 aryl group, (x) a C.sub.2 to C.sub.30 heteroaryl group, (xi) a C.sub.1 to C.sub.30 perfluoro-hydrocarbyl group, and (xii) a C.sub.1 to C.sub.10 trifluoroalkyl group, wherein the first organic compound has i) a dipole moment in the range of ≥0 and ≤2 Debye; and ii) a molecular weight in the range of ≥400 and ≤1,800; and bb) a metal borate compound; b) Transferring the first composition from the solid phase into the gas phase in a vacuum chamber; and c) depositing the first composition to form the organic semiconducting layer.

2. Method according to claim 1, wherein the first organic compound comprises at least one group selected from C.sub.10 to C.sub.24 condensed aryl group, and/or a C.sub.3 to C.sub.24 heteroaryl group.

3. Method according to claim 1, wherein the heteroaryl group comprises one to three heteroatoms independently selected from N, O or S.

4. Method according to claim 1, wherein the first organic compound further comprises a group selected from substituted or unsubstituted spiro[fluorene-9,9′-xanthene]-yl, substituted or unsubstituted 9,9′-dimethylfluorenyl, substituted or unsubstituted 9,9′-diphenylfluorenyl, 9,9′-spiro[bifluorene]-yl, substituted or unsubstituted naphthyl, substituted or unsubstituted phenanthrenyl, substituted or unsubstituted fluoranthenyl, a substituted or unsubstituted group consisting of 3 to 6 connected phenyl rings or substituted or unsubstituted tetraphenylethenyl.

5. Method according to claim 1, wherein the first organic compound is represented by the Formula 1a ##STR00031## wherein A.sup.1, A.sup.2, A.sup.3 and A.sup.4 are independently selected from a single bond, a substituted or unsubstituted C.sub.6 to C.sub.18 arylene or unsubstituted or substituted C.sub.1 to C.sub.18 heteroarylene; A.sup.5 is selected from unsubstituted or substituted C.sub.10-C.sub.30 condensed aryl or from unsubstituted or substituted C.sub.3-C.sub.30 heteroaryl; R.sup.1 to R.sup.5 are independently selected from substituted or unsubstituted phenyl; a) to e) are independently selected as 0 or 1 with the provision that 2≤a+b+c+d+e≤5; wherein in the Formula 1a, the one or more substituent(s), if present, are independently selected from (i) deuterium, (ii) a halogen, (iii) a C.sub.1 to C.sub.22 silyl group, (iv) a C.sub.1 to C.sub.30 alkyl group, (v) a C.sub.1 to C.sub.10 alkylsilyl group, (vi) a C.sub.6 to C.sub.22 arylsilyl group, (vii) a C.sub.3 to C.sub.30 cycloalkyl group, (viii) a C.sub.2 to C.sub.30 heterocycloalkyl group, (ix) a C.sub.6 to C.sub.30 aryl group, (x) a C.sub.2 to C.sub.30 heteroaryl group, (xi) a C.sub.1 to C.sub.30 perfluoro-hydrocarbyl group, or (xii) a C.sub.1 to C.sub.10 trifluoroalkyl group; and/or the first organic compound is represented by Formula 1b ##STR00032## wherein A.sup.1, A.sup.2, A.sup.3 and A.sup.4 are independently selected from a single bond, a substituted or unsubstituted C.sub.6 to C.sub.18 arylene or unsubstituted or substituted C.sub.1 to C.sub.18 heteroarylene; A.sup.5 is selected from unsubstituted or substituted C.sub.10 to C.sub.30 condensed aryl or from unsubstituted or substituted C.sub.3 to C.sub.30 heteroaryl; R.sup.1 to R.sup.3 are independently selected from substituted or unsubstituted phenyl; wherein in Formula 1b, the one or more substituent(s), if present, are independently selected from the group consisting of (i) deuterium, (ii) a halogen, (iii) a C.sub.1 to C.sub.22 silyl group, (iv) a C.sub.1 to C.sub.30 alkyl group, (v) a C.sub.1 to C.sub.10 alkylsilyl group, (vi) a C.sub.6 to C.sub.22 arylsilyl group, (vii) a C.sub.3 to C.sub.30 cycloalkyl group, (viii) a C.sub.2 to C.sub.30 heterocycloalkyl group, (ix) a C.sub.6 to C.sub.30 aryl group, (x) a C.sub.2 to C.sub.30 heteroaryl group, (xi) a C.sub.1 to C.sub.30 perfluoro-hydrocarbyl group, (xii) a C.sub.1 to C.sub.10 trifluoroalkyl group; and/or the first organic compound may be represented by Formula 1c ##STR00033## wherein the compound of formula (1c) comprises one moiety A.sup.1-A.sup.2-A.sup.3-A.sup.4-A.sup.5, wherein the asterisk symbol “*” marks the possible binding positions of the moiety A.sup.1-A.sup.2-A.sup.3-A.sup.4-A.sup.5 to the remaining structure; A.sup.1, A.sup.2, A.sup.3 and A.sup.4 are independently selected from a single bond, a substituted or unsubstituted C.sub.6 to C.sub.18 arylene or unsubstituted or substituted C.sub.1 to C.sub.18 heteroarylene; A.sup.5 is selected from unsubstituted or substituted C.sub.10 to C.sub.30 condensed aryl or from unsubstituted or substituted C.sub.3 to C.sub.30 heteroaryl; wherein in Formula 1c, the one or more substituent(s), if present, are independently selected from the group consisting of (i) deuterium, (ii) halogen, (iii) a C.sub.1 to C.sub.22 silyl group, (iv) a C.sub.1 to C.sub.30 alkyl group, (v) a C.sub.1 to C.sub.10 alkylsilyl group, (vi) a C.sub.6 to C.sub.22 arylsilyl group, (vii) a C.sub.3 to C.sub.30 cycloalkyl group, (viii) a C.sub.2 to C.sub.30 heterocycloalkyl group, (ix) a C.sub.6 to C.sub.30 aryl group, (x) a C.sub.2 to C.sub.30 heteroaryl group, (xi) a C.sub.1 to C.sub.30 perfluoro-hydrocarbyl group, (xii) a C.sub.1 to C.sub.10 trifluoroalkyl group; and/or the first organic compound may be represented by Formula 1d ##STR00034## wherein the compound of formula (1d) comprises one moiety A.sup.1-A.sup.2-A.sup.3-A.sup.4-A.sup.5, wherein the asterisk symbol “*” marks the possible binding positions of the moiety A.sup.1-A.sup.2-A.sup.3-A.sup.4-A.sup.5 to the remaining structure; Y.sup.1 is selected from a single bond, O, S, CR.sub.2 or SiR.sub.2, wherein R is independently selected from C.sub.1 to C.sub.12 alkyl or C.sub.6 to C.sub.18 aryl; A.sup.1, A.sup.2, A.sup.3 and A.sup.4 are independently selected from a single bond, a substituted or unsubstituted C.sub.6 to C.sub.18 arylene or unsubstituted or substituted C.sub.1 to C.sub.18 heteroarylene; A.sup.5 is selected from unsubstituted or substituted C.sub.10 to C.sub.30 condensed aryl or from unsubstituted or substituted C.sub.3 to C.sub.30 heteroaryl; wherein in Formula 1d, the one or more substituent(s), if present, are independently selected from the group consisting of (i) deuterium, (ii) halogen, (iii) a C.sub.1 to C.sub.22 silyl group, (iv) a C.sub.1 to C.sub.30 alkyl group, (v) a C.sub.1 to C.sub.10 alkylsilyl group, (vi) a C.sub.6 to C.sub.22 arylsilyl group, (vii) a C.sub.3 to C.sub.30 cycloalkyl group, (viii) a C.sub.2 to C.sub.30 heterocycloalkyl group, (ix) a C.sub.6 to C.sub.30 aryl group, (x) a C.sub.2 to C.sub.30 heteroaryl group, (xi) a C.sub.1 to C.sub.30 perfluoro-hydrocarbyl group, (xii) a C.sub.1 to C.sub.10 trifluoroalkyl group.

6. Method according to claim 1, wherein the metal borate compound is an alkali metal borate, an alkaline earth metal borate or a rare earth metal borate having a molecular weight in the range of ≥100 to ≤1,200.

7. Method according to claim 1, wherein the metal borate compound has the following Formula 2 ##STR00035## wherein M is a metal ion, each of A.sup.6 to A.sup.9 is independently selected from H, substituted or unsubstituted C.sub.6-C.sub.20 aryl and substituted or unsubstituted C.sub.2-C.sub.20 heteroaryl and n is valency of the metal ion.

8. Method according to claim 1, further comprising the steps of e) providing a second organic compound in a second vacuum thermal evaporation source; f) transferring the second organic compound from the solid phase into the gas phase in the vacuum chamber; and g) depositing the first composition together with the second organic compound to form the organic semiconducting layer.

9. Method according to claim 8, wherein the second organic compound has a dipole moment in the range of ≥1.5 Debye and ≤10 Debye; and a molecular weight in the range of ≥400 and ≤1,800.

10. Method according to claim 8, wherein the second organic compound comprises at least one group selected from phenanthroline; benzimidazole; pyridine-4-yl; pyrimidine; quinoline; benzoquinoline; dibenzoquinoline; quinoxaline; benzoquinoxaline; dibenzoquinaxoline; xanthene; C═O; COOR, wherein R is selected from C.sub.1-C.sub.12 alkyl or C.sub.6-C.sub.18 aryl; and from P═X, wherein X is selected from O, S or Se.

11. Organic electronic device comprising an anode, a cathode and an organic semiconducting layer obtainable by the method according to claim 1.

12. Method for preparing an organic electronic device comprising a step of preparing an organic semiconducting layer according to the method of claim 1.

13. Composition consisting of a) a first organic compound, the first organic compound comprising at least one C.sub.10 to C.sub.30 condensed aryl group and/or at least one C.sub.3 to C.sub.30 heteroaryl group, wherein the first organic compound has (i) a dipole moment in the range of ≥0 and ≤2 Debye; and (ii) a molecular weight in the range of ≥400 to ≤1,800; and b) at least one metal borate.

14. Composition according to claim 13, wherein the metal in the metal borate is selected from alkali metal, alkaline earth metal or rare earth metal.

15. Composition according to claim 13, wherein the metal borate has a molecular weight in the range of ≥100 and ≤1,200.

16. Method according to claim 3, wherein the heteroaryl group comprises one to three N atoms or one O or S atom.

17. Method according to claim 10, wherein X is selected from O or S.

18. Method according to claim 10, wherein X is O.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0290] These and/or other aspects and advantages of the present invention will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings, of which:

[0291] FIG. 1 is a schematic sectional view of an organic light-emitting diode (OLED), according to an exemplary embodiment of the present invention;

[0292] FIG. 2 is a schematic sectional view of an OLED, according to an exemplary embodiment of the present invention.

[0293] FIG. 3 is a schematic sectional view of a tandem OLED comprising a charge generation layer, according to an exemplary embodiment of the present invention.

[0294] FIG. 4 shows a graph wherein the amount of first composition left in the VTE source in plotted against the concentration of compound in the first composition in wt.-%.

DETAILED DESCRIPTION

[0295] Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The exemplary embodiments are described below, in order to explain the aspects of the present invention, by referring to the figures.

[0296] Herein, when a first element is referred to as being formed or disposed “on” or “onto” a second element, the first element can be disposed directly on the second element, or one or more other elements may be disposed there between. When a first element is referred to as being formed or disposed “directly on” or “directly onto” a second element, no other elements are disposed there between.

[0297] 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, an anode 120, a hole injection layer (HIL) 130, a hole transport layer (HTL) 140, an emission layer (EML) 150, an electron transport layer (ETL) 160. The electron transport layer (ETL) 160 is formed on the EML 150. Onto the electron transport layer (ETL) 160, an electron injection layer (EIL) 180 is disposed. The cathode 190 is disposed directly onto the electron injection layer (EIL) 180.

[0298] Instead of a single electron transport layer 160, optionally an electron transport layer stack (ETL) can be used.

[0299] FIG. 2 is a schematic sectional view of an OLED 100, according to another exemplary embodiment of the present invention. FIG. 2 differs from FIG. 1 in that the OLED 100 of FIG. 2 comprises an electron blocking layer (EBL) 145 and a hole blocking layer (HBL) 155.

[0300] Referring to FIG. 2, the OLED 100 includes a substrate no, an anode 120, a hole injection layer (HIL) 130, a hole transport layer (HTL) 140, an electron blocking layer (EBL) 145, an emission layer (EML) 150, a hole blocking layer (HBL) 155, an electron transport layer (ETL) 160, an electron injection layer (EIL) 180 and a cathode electrode 190.

[0301] Preferably, the organic semiconducting layer comprising a first composition may be an ETL.

[0302] FIG. 3 is a schematic sectional view of a tandem OLED 200, according to another exemplary embodiment of the present invention. FIG. 3 differs from FIG. 2 in that the OLED 100 of FIG. 3 further comprises a charge generation layer (CGL) and a second emission layer (151).

[0303] Referring to FIG. 3, the OLED 200 includes a substrate 110, an anode 120, a first hole injection layer (HIL) 130, a first hole transport layer (HTL) 140, a first electron blocking layer (EBL) 145, a first emission layer (EML) 150, a first hole blocking layer (HBL) 155, a first electron transport layer (ETL) 160, an n-type charge generation layer (n-type CGL) 185, a hole generating layer (p-type charge generation layer; p-type GCL) 135, a second hole transport layer (HTL) 141, a second electron blocking layer (EBL) 146, a second emission layer (EML) 151, a second hole blocking layer (EBL) 156, a second electron transport layer (ETL) 161, a second electron injection layer (EIL) 181 and a cathode 190.

[0304] Preferably, the organic semiconducting layer comprising a t composition may be the first ETL and/or second ETL.

[0305] 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 and 200. In addition, various other modifications may be applied thereto.

[0306] 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.

[0307] Melting Point

[0308] The melting point (mp) is determined as peak temperatures from the DSC curves of the above TGA-DSC measurement or from separate DSC measurements (Mettler Toledo DSC822e, heating of samples from room temperature to completeness of melting with heating rate 10 K/min under a stream of pure nitrogen. Sample amounts of 4 to 6 mg are placed in a 40 μL Mettler Toledo aluminum pan with lid, a <1 mm hole is pierced into the lid).

[0309] Glass Transition Temperature

[0310] The glass transition temperature (Tg) is measured under nitrogen and using a heating rate of 10 K per min in a Mettler Toledo DSC 822e differential scanning calorimeter as described in DIN EN ISO 11357, published in March 2010.

[0311] Rate Onset Temperature

[0312] The rate onset temperature (T.sub.RO) 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 Company (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 to 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 Ångstrom 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.

[0313] 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.

[0314] 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.

[0315] According to another embodiment, the difference between rate onset temperature of the first organic compound and the metal borate compound is less than 60 K, alternatively less than 50 K, alternatively less than 40 K.

[0316] Thereby, homogeneity of the organic semiconducting layer prepared by the method according to invention may be improved.

[0317] Reduction Potential

[0318] 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.

[0319] Calculated HOMO and LUMO

[0320] The HOMO and LUMO are calculated with the program package TURBOMOLE V6.5. 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.

[0321] Preparation of the First Composition

[0322] The first organic compound and the metal borate compound may be prepared by methods known in the art.

[0323] In Table 1, properties are shown of first organic compounds which can be suitable used.

[0324] The first composition may be prepared by mixing the first organic compound and the metal borate compound as in the solid state, followed by evaporation and condensation at a pressure of 10.sup.−3 to 10.sup.−7 mbar.

[0325] In Table 2, first compositions are shown which can be suitable used. Metal borate compound of Formula (2a) may be referred to as Li-1 and metal borate compound of Formula (2b) may be referred to as Li-2.

[0326] Preparation of the Second Organic Compound

[0327] The second organic compounds may be prepared by methods known in the art. In Table 3 are shown examples of second organic compounds.

[0328] Electron-Only Devices (EOD)

[0329] To indirectly determine the conductivity of an organic semiconducting layer prepared by the method according to invention, election-only devices were prepared and the operating voltage determined. The lower the operating voltage is at a given current density, the higher the conductivity of the organic semiconducting layers.

[0330] To prepare the electron-only devices, Example 1 and comparative example 1 in Table 4, a glass substrate was cut to a size of 50 mm×50 mm×0.7 mm, ultrasonically cleaned with isopropyl alcohol for 5 minutes and then with pure water for 5 minutes, and cleaned again with UV ozone for 30 minutes.

[0331] Then, 11 nm Mg:Ag alloy (90:10 vol.-%) were deposited on the glass substrate at a pressure of 10.sup.−5 to 10.sup.−7 mbar to form a first electrode.

[0332] Then, dimethyl(3-(10-(naphthalen-2-yl)anthracen-9-yl)phenyl)phosphine oxide (also referred to as ETM-1) as second organic compound and first composition C-1, see Example 1 in Table 4, or Li-1, see comparative example 1, were co-deposited on the first electrode to form a first organic semiconducting layer having a thickness of 17 urn. The concentration of the compounds in the layer can be taken from Table 4.

[0333] Then, a second organic semiconducting layer comprising the first composition, see example 1 in Table 4, or Li-1, see comparative example 1, was deposited on the first organic semiconducting layer to form a second organic semiconducting layer. The thickness of the second organic semiconducting layer can be taken from Table 4.

[0334] Then, dimethyl(3-(10-(naphthalen-2-yl)anthracen-9-yl)phenyl)phosphine oxide (also referred to as ETM-1) as second organic compound and first composition C-1, see Example 1 in Table 4, or Lithium tetra(1H-pyrazol-1-yl)borate (also referred to as Li-1), see comparative example 1, were co-deposited on the second organic semiconducting layer to form a third organic semiconducting layer having a thickness of 17 nm. The concentration of the compounds in the layer can be taken from Table 4.

[0335] Then, 11 nm Mg:Ag alloy (90:10 vol.-%) were deposited on the third organic semiconducting layer at a pressure of 10.sup.−5 to 10.sup.−7 mbar to form a second electrode.

[0336] The operating voltage was determined as described for OLEDs below.

[0337] General Procedure for Fabrication of OLEDs

[0338] For top emission devices, Example 2 to 6 in Table 5, a glass substrate was cut to a size of 50 mm×50 mm×0.7 mm, ultrasonically cleaned with isopropyl alcohol for 5 minutes and then with pure water for 5 minutes, and cleaned again with UV ozone for 30 minutes. 100 nm Ag were deposited on the glass substrate at a pressure of 10.sup.−5 to 10.sup.−7 mbar to form the anode.

[0339] Then, 92 vol.-% 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 vol.-% 2,2′,2″-(cyclopropane-1,2,3-triylidene)tris(2-(p-cyanotetrafluorophenyl)acetonitrile) was vacuum deposited on the anode, to form a HIL having a thickness of 10 nm. 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 HTL having a thickness of 118 nm.

[0340] Then, for examples 2 and 3, N,N-bis(4-(dibenzo[b,d]furan-4-yl)phenyl)-[1,1′:4′,4″-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. For examples 4 to 6, N-(4-(dibenzo[b,d]furan-4-yl)phenyl)-N-(4-(9-phenyl-9H-fluoren-9-yl)phenyl)-[1,1′-biphenyl]-4-amine (CAS 1824678-59-2) was vacuum deposited on the HTL, to form an electron blocking layer (EBL) having a thickness of 5 nm.

[0341] Then, 97 vol.-% H09 (Sun Fine Chemicals, South Korea) as EML host and 3 vol.-% BD200 (Sun Fine Chemicals, South Korea) as fluorescent blue dopant were deposited on the EBL, to form a blue-emitting EML with a thickness of 20 nm.

[0342] Then the auxiliary ETL was 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 (CAS 1955543-57-3) on the emission layer (EML).

[0343] Then, the electron transporting layer was formed on the auxiliary electron transport layer according to Example 2 to Example 6 with a the thickness of 31 nm, see Table 5.

[0344] Then, the electron injection layer was formed on the electron transporting layer by deposing Yb with a thickness of 2 nm.

[0345] Then, Mg:Ag alloy (90:10 vol.-%) was evaporated at a rate of 0.01 to 1 Å/s at 10.sup.−7 mbar to form a cathode with a thickness of 13 nm.

[0346] A cap layer of Biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine was formed on the cathode with a thickness of 75 nm.

[0347] 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.

[0348] 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 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.

[0349] 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.

[0350] 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.

[0351] The light output in external efficiency EQE and power efficiency (lm/W efficiency) are determined at 10 mA/cm.sup.2 for top emission devices.

[0352] To determine the efficiency EQE in % the light output of the device is measured using a calibrated photodiode.

[0353] To determine the power efficiency in lm/W, in a first step the luminance in candela per square meter (cd/m.sup.2) is measured with an array spectrometer CAS140 CT from Instrument Systems which has been calibrated by Deutsche Akkreditierungsstelle (DAkkS). In a second step, the luminance is then multiplied by π and divided by the voltage and current density.

TABLE-US-00001 TABLE 1 Examples of first organic compounds Molecular Dipole Referred weight moment mp Tg T.sub.RO to as: Chemical formula (g/mol) (Debye) (° C.) (° C.) (° C.) OC-1 [00012] 658.83 1.21 262 135 228 OC-2 [00013] 658.83 1.02 n.o..sup.1) 129 216 OC-3 [00014] 582.75 0.19 338 140 230 OC-4 [00015] 689.84 0.57 280 138 211 OC-5 [00016] 689.84 0.92 268 149 221 OC-6 [00017] 613.76 0.26 n.o.  92 228 OC-7 [00018] 509.6  0.19 254 100 217 OC-8 [00019] 577.73 0.31 n.o.  95 220 OC-9 [00020] 625.81 1.77 n.o. 126 212 OC-10 [00021] 575.67 0.78 273 145 224 OC-11 [00022] 653.78 0.7  227 116 230 OC-12 [00023] 669.84 1.13 252 126 237 OC-13 [00024] 619.79 0.31 285 124 214 OC-14 [00025] 605.76 1.06 n.o. 117 230 OC-15 [00026] 605.76 0.17 266 138 220 OC-16 [00027] 550.66 0.68 n.d..sup.2) 105 218 OC-17 [00028] 420.50 0.77 249 n.d. n.d. .sup.1)not observed. .sup.2)not determined.

TABLE-US-00002 TABLE 2 Examples of first compositions Concentration Concentration of first organic of metal borate First compound in Metal compound in Referred organic first composition borate first composition to as: compound [wt.-%] compound [wt.-%] C-1 OC-2  50 Li-1 50 C-2 OC-17 50 Li-2 50 C-3 OC-5  50 Li-1 50

TABLE-US-00003 TABLE 3 Examples of second organic compounds Referred to as: Second organic compound Dipole moment (Debye) ETM-1 [00029] 4.62 ETM-2 [00030] 4.47

[0354] Stability of the First Composition Over Time

[0355] To check the stability of the first composition over time, a first composition consisting of 75 wt.-% first organic compound and 25 wt.-% metal borate compound was loaded into a source and evaporated at 10.sup.−5 to 10.sup.−7 mbar until 64 wt.-% of the content of the VTE source had been evaporated. As can be seen in FIG. 4, the ratio of first organic compound (full line) to metal borate compound (dotted line) does not change significantly over time.

TABLE-US-00004 TABLE 4 Operating voltage of electron-only devices comprising a layer stack comprising organic semiconducting layers comprising a first composition compared to the state of the art Composition of the first and third organic semiconducting layer Concentration Composition Thickness Concentration of second of the of the Operating of first Second organic second organic second organic voltage at First composition organic compound semiconducting semiconducting 15 mA/cm.sup.2 composition [vol.-%] compound [vol.-%] layer layer [nm] [V] Comparative Li-1 70 ETM-1 30 Li-1 0 0.3 example 1 1 0.4 2 1.5 3 3.7 Example 1 C-1 50 ETM-1 50 C-1 0 0.5 1 0.1 2 0.3 3 0.5

TABLE-US-00005 TABLE 5 Performance of an organic electroluminescent device comprising an electron transport layer comprising the first composition Concentration Thickness Concentration of second electron Operating cd/A of first Second organic transport voltage at efficiency at LT97 at First composition organic compound layer 10 mA/cm.sup.2 10 mA/cm.sup.2 30 mA/cm.sup.2 composition (vol.-%) compound (vol.-%) (nm) (V) (cd/A) (h) Example 2 C-2 50 ETM-1 50 31 3.7 7.1 93 Example 3 C-2 50 ETM-2 50 31 3.8 7.5 69 Example 4 C-1 50 ETM-1 50 31 3.7 7.6 60 Example 5 C-1 30 ETM-1 70 31 3.6 7.6 53 Example 6 C-1 50 ETM-2 50 31 3.8 7.4 65

[0356] Technical Effect of the Invention

[0357] In Table 4 is shown the operating voltage of EOD, wherein the second organic semiconducting layer has a thickness of 0 to 3 nm.

[0358] In comparative example 1, the first and third organic semiconducting layer comprise a second organic compound and metal borate compound Li-1. The second organic semiconducting layer consists of metal borate compound Li-1. The operating voltage increases with increased thickness of the second organic semiconducting layer. At 0 nm, the operating voltage is 0.3 Volt and at 3 nm the operating voltage is 3.7 V, see Table 4.

[0359] In example 1, the first and third organic semiconducting layer comprise a second organic compound and a first composition C-1. The second organic semiconducting layer consists of first composition C-1. At 0 nm, the operating voltage is 0.5 Volt. The operating voltage is comparable to comparative example 1. At 3 nm, the operating voltage is 0.5 V. Thereby, the operating voltage of devices comprising an organic semiconducting layer according to invention is substantially lower than in comparative example 1.

[0360] The operating voltage is an indication for conductivity of a semiconducting layer. The higher the conductivity the lower is the operating voltage.

[0361] In summary, an organic semiconducting layer prepared by the method according to invention has much improved conductivity compared to the state of the art.

[0362] In Table 5 is shown the performance of OLEDs comprising an organic semiconducting layer prepared according to invention.

[0363] As can be seen in Example 2 to 6, very good operating voltage, cd/A efficiency and lifetime can be obtained when the organic semiconducting layer is prepared according to invention.

[0364] In summary, an organic electronic device comprising an organic semiconducting layer prepared by the method according to invention shows very good performance, in particular operating voltage, cd/A efficiency and/or lifetime.

[0365] The features disclosed in the foregoing description and in the dependent claims may, both separately and in any combination thereof, be material for realizing the aspects of the disclosure made in the independent claims, in diverse forms thereof.