Organic Electroluminescent Device and Display Device Comprising the Organic Electroluminescent Device

Abstract

The present invention relates to an electroluminescent device comprising an electron injection layer comprising a compound of formula (I) and a metal and a display device comprising the organic electroluminescent device.

##STR00001##

Claims

1. An organic electroluminescent device comprising an anode layer, a cathode layer, a first emission layer (EML), an electron transport layer (ETL) and an electron injection layer (EIL), wherein the EML, ETL and EIL are arranged between the anode layer and the cathode layer and the EIL is in direct contact with the cathode layer, whereby the EIL comprises at least one compound of formula (I) ##STR00158## Wherein M is a metal ion, n is an integer selected from 1 to 4, which corresponds to the oxidation number of M; L is an anionic ligand, wherein the proton affinity of L is selected in the range of 10 eV and 15.6 eV and wherein L comprises at least four fluorine atoms; wherein the proton affinity is determined by performing the steps of calculation of the optimized geometries of the molecule and its deprotonated form; and calculation of the proton affinity of the ligand by determining the energy difference between the optimized structure of the molecule and of its deprotonated form; whereby the calculations are performed by applying the hybrid functional B3LYP with the 6-31G* basis set in the gas phase as implemented in the program package TURBOMOLE V6.5 or in the program package ORCA Version 5.0.3-f1; wherein if several conformers of the molecule are viable, the conformer with the lowest total energy is selected: AL is an ancillary ligand; m is an integer selected from 0 to 2; whereby the EIL comprises at least one metal; the ETL comprises a metal organic complex wherein the metal organic complex is free of fluorine atoms; wherein the electron transport layer is arranged between the first emission layer and the electron injection layer.

2. An organic electroluminescent device comprising an anode layer, a cathode layer, a first emission layer (EML), an electron transport layer (ETL) and an electron injection layer (EIL), wherein the EML, ETL and EIL are arranged between the anode layer and the cathode layer, and the EIL is in direct contact with the cathode layer, whereby the EIL comprises at least one compound of formula (Ia) ##STR00159## wherein M is a metal ion, n is an integer selected from 1 to 4, which corresponds to the oxidation number of M; L is an anionic ligand comprising at least 15 covalently bound atoms, wherein at least two atoms are selected from carbon atoms, and wherein L comprises at least four fluorine atoms; AL is an ancillary ligand; m is an integer selected from 0 to 2; whereby the EIL comprises at least one metal; the ETL comprises a metal complex wherein the metal organic complex is free of fluorine atoms; wherein the electron transport layer is arranged between the first emission layer and the electron injection layer.

3. The organic electroluminescent device according to claim 1, wherein the electron transport layer (ETL) further comprises at least one compound of formula (II): ##STR00160## whereby m and n are independently 1 or 2; k is independently 0, 1 or 2; Ar.sup.2 is independently selected from the group consisting of C.sub.2 to C.sub.42 heteroaryl and C.sub.6 to C.sub.60 aryl, wherein each Ar.sup.2 may be substituted with one or two substituents independently selected from the group consisting of C.sub.6 to C.sub.12 aryl, C.sub.3 to C.sub.11 heteroaryl, and C.sub.1 to C.sub.6 alkyl, D, 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.6 alkyl, partially or perfluorinated C.sub.1 to C.sub.6 alkoxy, partially or perdeuterated C.sub.1 to C.sub.6 alkyl, partially or perdeuterated C.sub.1 to C.sub.6 alkoxy, halogen, CN or PY(R.sup.10).sub.2, wherein Y is selected from O, S or Se, and R.sup.10 is independently selected from C.sub.6 to C.sub.12 aryl, C.sub.3 to C.sub.12 heteroaryl, C.sub.1 to C.sub.6 alkyl, C.sub.1 to C.sub.6 alkoxy, partially or perfluorinated C.sub.1 to C.sub.6 alkyl, partially or perfluorinated C.sub.1 to C.sub.6 alkoxy, partially or perdeuterated C.sub.1 to C.sub.6 alkyl, partially or perdeuterated C.sub.1 to C.sub.6 alkoxy; wherein each C.sub.6 to C.sub.12 aryl substituent on Ar.sup.2 and each C.sub.3 to C.sub.11 heteroaryl substituent on Ar.sup.2 may be substituted with C.sub.1 to C.sub.4 alkyl or halogen; Z is independently selected from C.sub.6 to C.sub.30 aryl, wherein each Z may be substituted with one or two substituents independently selected from the group consisting of C.sub.6 to C.sub.12 aryl and C.sub.1 to C.sub.6 alkyl, D, 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.6 alkyl, partially or perfluorinated C.sub.1 to C.sub.6 alkoxy, partially or perdeuterated C.sub.1 to C.sub.6 alkyl, partially or perdeuterated C.sub.1 to C.sub.6 alkoxy, halogen, CN or PY(R.sup.10).sub.2, wherein Y is selected from O, S or Se, and R.sup.10 is independently selected from C.sub.6 to C.sub.12 aryl, C.sub.3 to C.sub.12 heteroaryl, C.sub.1 to C.sub.6 alkyl, C.sub.1 to C.sub.6 alkoxy, partially or perfluorinated C.sub.1 to C.sub.6 alkyl, partially or perfluorinated C.sub.1 to C.sub.6 alkoxy, partially or perdeuterated C.sub.1 to C.sub.6 alkyl, partially or perdeuterated C.sub.1 to C.sub.6 alkoxy; wherein each C.sub.6 to C.sub.12 aryl substituent on Z may be substituted with C.sub.1 to C.sub.4 alkyl or halogen; and G is chosen so that the dipole moment of a compound G-phenyl is 1 D and 7 D.

4. An organic electroluminescent device according to claim 1, whereby the EIL comprises a first EIL sub-layer (EIL1) and a second EIL sub-layer (EIL2), wherein the first sub-layer is arranged closer to the anode layer and the second sub-layer is arranged closer to the cathode layer; and wherein the first EIL sub-layer comprises the compound of formula (I) and the second EIL sub-layer comprises the metal.

5. The organic electroluminescent device according to claim 1, wherein the EIL may be formed as a single layer.

6. The organic electroluminescent device according to claim 1, whereby in formula (I) L is selected from formulas La to Lc. ##STR00161## wherein A.sup.1 and A.sup.2 are independently selected from substituted or unsubstituted C.sub.1 to C.sub.12 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 of A.sup.1 and A.sup.2 may be independently 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, COOR, SO.sub.2R.sup.1, halogen, F or CN, wherein R.sup.1 may be selected from 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; A.sup.3 is selected from CN, substituted or unsubstituted C.sub.1 to C.sub.4 alkyl, or whereby A.sup.3 is selected as to form a cyclic structure with either A.sup.1 or A.sup.2, and whereby the ring may comprise one or more heteroatoms; wherein L comprises at least four fluorine atoms.

7. The organic electroluminescent device according to claim 1, wherein the ligand L of formula (I) is selected from G1 to G111: ##STR00162## ##STR00163## ##STR00164## ##STR00165## ##STR00166## ##STR00167## ##STR00168## ##STR00169## ##STR00170## ##STR00171##

8. The organic electroluminescent device according to claim 1, wherein the compound of formula (I) is selected from: LiTFSI, K TFSI, Cs TFSI, Ag TFSI, Mg(TFSI).sub.2, Mn(TFSI).sub.2, Sc(TFSI).sub.3, Na[N(SO.sub.2C.sub.4F.sub.9).sub.2], K[N(SO.sub.2C.sub.4F.sub.9).sub.2], Mg[N(SO.sub.2.sup.iC.sub.3F.sub.7).sub.2].sub.2, Zn[N(SO.sub.2.sup.iC.sub.3F.sub.7).sub.2].sub.2, Ag[N(SO.sub.2.sup.iC.sub.3F.sub.7).sub.2], Ag[N(SO.sub.2C.sub.3F.sub.7).sub.2], Ag[N(SO.sub.2C.sub.4F.sub.9).sub.2], Ag[N(SO.sub.2CF.sub.3)(SO.sub.2C.sub.4F.sub.9)], Cs[N(SO.sub.2C.sub.4F.sub.9).sub.2], Mg[N(SO.sub.2C.sub.4F.sub.9).sub.2].sub.2, Ca[N(SO.sub.2C.sub.4F.sub.9).sub.2].sub.2, Ag[N(SO.sub.2C.sub.4F.sub.9).sub.2], Cu[N(SO.sup.2C.sub.3F.sub.7).sub.2].sub.2, Cu[N(SO.sub.2C.sub.3F.sub.7).sub.2].sub.2, Cu[N(SO.sub.2CF.sub.3) (SO.sub.2C.sub.4F.sub.9)].sub.2, Cu[N(SO.sub.2C.sub.2H.sub.5) (SO.sub.2C.sub.4F.sub.9)].sub.2, Cu[N(SO.sub.2 .sup.iC.sub.3H.sub.7) (SO.sub.2C.sub.4F.sub.9)].sub.2, Cu[N(SO.sup.2C.sub.3F.sub.7) (SO.sub.2C.sub.4F.sub.9)].sub.2, Cu[N(SO.sub.2CH.sub.3) (SO.sub.2C.sub.4F.sub.9)].sub.2, Mg[N(SO.sub.2CF.sub.3) (SO.sub.2C.sub.4F.sub.9)].sub.2, Mn[N(SO.sub.2CF.sub.3) (SO.sub.2C.sub.4F.sub.9)].sub.2, Ag[N(SO.sub.2CH.sub.3) (SO.sub.2C.sub.4F.sub.9)], ##STR00172## ##STR00173## ##STR00174## ##STR00175## ##STR00176## ##STR00177## wherein .sup.i denotes iso.

9. The organic electroluminescent device according to claim 3, wherein the compound of formula (II) comprises a benzimidazole, CN or PO group.

10. The organic electroluminescent device according to claim 1, wherein the metal organic complex is a lithium complex.

11. The organic electroluminescent device according to claim 1, wherein the metal organic complex comprises a quinolate or borate ligand and the metal of the metal organic complex has a valency of (I) or (II).

12. The organic electroluminescent device according to claim 1, wherein the organic electroluminescent device further comprises a hole injection layer, wherein the hole injection layer is arranged between the anode layer and the first emission layer, wherein the hole injection layer comprises a compound of formula (I).

13. The organic electroluminescent device according to claim 1, whereby the cathode layer comprises 50 vol.-% and 100 vol.-% Ag.

14. The organic electroluminescent device according to claim 1, whereby the organic luminescent device is an organic light emitting diode.

15. A display device comprising an organic electroluminescent device according to claim 1.

Description

DESCRIPTION OF THE DRAWINGS

[0264] 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.

[0265] 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.

[0266] FIG. 1 is a schematic sectional view of an organic electroluminescent device, according to an exemplary embodiment of the present invention;

[0267] FIG. 2 is a schematic sectional view of an organic electroluminescent device, according to an exemplary embodiment of the present invention;

[0268] FIG. 3 is a schematic sectional view of an organic electroluminescent device, according to an exemplary embodiment of the present invention;

[0269] FIG. 4 is a schematic sectional view of an organic electroluminescent device, according to an exemplary embodiment of the present invention;

[0270] FIG. 5 is a schematic sectional view of an organic electroluminescent device, according to an exemplary embodiment of the present invention;

[0271] FIG. 6 is a schematic sectional view of an organic electroluminescent device, according to an exemplary embodiment of the present invention.

[0272] Hereinafter, the figures are illustrated in more detail with reference to examples. However, the present disclosure is not limited to the following figures.

[0273] 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.

[0274] FIG. 1 is a schematic sectional view of an organic electroluminescent device 100, according to an exemplary embodiment of the present invention. The organic electroluminescent device 100 includes a substrate 110, an anode layer 120, a first emission layer (EML) 150, an electron transport layer (ETL) 170, an electron injection layer (EIL) 180 and a cathode layer 190. The EML 150 is disposed on the anode layer. Onto the EML 150, the ETL 170, the EIL 180 and the cathode layer 190 are disposed.

[0275] FIG. 2 is a schematic sectional view of an organic electroluminescent device 100, according to an exemplary embodiment of the present invention. The organic electroluminescent device 100 includes a substrate 110, an anode layer 120, a first emission layer (EML) 150, an electron transport layer (ETL) 170, an electron injection layer (EIL) 180, wherein the EIL comprises a first EIL sub-layer (EIL1) 181 and a second EIL sub-layer (EIL2) 182, and a cathode layer 190. The EML 150 is disposed on the anode layer. Onto the EML 150, the ETL 170, the EIL 180 and the cathode layer 190 are disposed.

[0276] FIG. 3 is a schematic sectional view of an organic electroluminescent device 100, according to an exemplary embodiment of the present invention. The organic electroluminescent device 100 includes a substrate 110, an anode layer 120, a hole injection layer (HIL) 130, a hole transport layer (HTL) 140, a first emission layer (EML) 150, an electron transport layer (ETL) 170, an electron injection layer (EIL) 180 and a cathode layer 190. The HIL 130 is disposed on the anode layer. Onto the HIL 130, the HTL 140, the EML 150, the ETL 170, the EIL 180 and the cathode layer 190 are disposed.

[0277] FIG. 4 is a schematic sectional view of an organic electroluminescent device 100, according to an exemplary embodiment of the present invention. The organic electroluminescent device 100 includes a substrate 110, an anode layer 120, a hole injection layer (HIL) 130, a hole transport layer (HTL) 140, an electron blocking layer (EBL) 145, a first emission layer (EML) 150, a hole blocking layer (HBL) 160, an electron transport layer (ETL) 170, an electron injection layer (EIL) 180 and a cathode layer 190. The HIL 130 is disposed on the anode layer. Onto the HIL 130, the HTL 140, the EBL 145, the EML 150, the HBL 160, the ETL 170, the EIL 180 and the cathode layer 190 are disposed.

[0278] FIG. 5 is a schematic sectional view of an organic electroluminescent device 100, according to an exemplary embodiment of the present invention. The organic electroluminescent device 100 includes a substrate 110, an anode layer 120, a hole injection layer (HIL) 130, a hole transport layer (HTL) 140, an electron blocking layer (EBL) 145, a first emission layer (EML) 150, a hole blocking layer (HBL) 160, an electron transport layer (ETL) 170, an electron injection layer (EIL) 180, wherein the EIL comprises a first EIL sub-layer (EIL1) 181 and a second EIL sub-layer (EIL2) 182, and a cathode layer 190. The HIL 130 is disposed on the anode layer. Onto the HIL 130, the HTL 140, the EBL 145, the EML 150, the HBL 160, the ETL 170, the EIL 180 and the cathode layer 190 are disposed.

[0279] FIG. 6 is a schematic sectional view of an organic electroluminescent device 100, according to an exemplary embodiment of the present invention. The organic electroluminescent device 100 includes a substrate 110, an anode layer 120, wherein the anode layer 120 comprises a first anode sub-layer 121, a second anode sub-layer 122 and a third anode sub-layer 123, a hole injection layer (HIL) 130, a hole transport layer (HTL) 140, an electron blocking layer (EBL) 145, a first emission layer (EML) 150, a hole blocking layer (HBL) 160, an electron transport layer (ETL) 170, an electron injection layer (EIL) 180, wherein the EIL comprises a first EIL sub-layer (EIL1) 181 and a second EIL sub-layer (EIL2) 182, and a cathode layer 190. The HIL 130 is disposed on the anode layer. Onto the HIL 130, the HTL 140, the EBL 145, the EML 150, the HBL 160, the ETL 170, the EIL 180 and the cathode layer 190 are disposed.

[0280] While not shown in FIG. 1 to FIG. 6, a capping and/or sealing layer may further be formed on the cathode layer 190, in order to seal the organic electroluminescent device 100. In addition, various other modifications may be applied thereto.

[0281] 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

[0282] The invention is furthermore illustrated by the following examples which are illustrative only and non-binding.

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 all inventive and comparative examples (cf. Tables 6 and 7), a glass substrate with an anode layer comprising a first anode sub-layer of 120 nm Ag, a second anode sub-layer of 8 nm ITO and a third anode sub-layer of 10 nm ITO was cut to a size of 50 mm50 mm0.7 mm, ultrasonically washed with water for 60 minutes and then with isopropanol for 20 minutes. The liquid film was removed in a nitrogen stream, followed by plasma treatment to prepare the anode layer. The plasma treatment was performed in an atmosphere comprising 97.6 vol.-% nitrogen and 2.4 vol.-% oxygen.

[0285] 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.

[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 121 nm.

[0287] Then N-([1,1-biphenyl]-4-yl)-9,9-diphenyl-N-(4-(triphenylsilyl)phenyl)-9H-fluoren-2-amine (CAS 1613079-70-1) 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 EML with a thickness of 20 nm.

[0289] Then a hole blocking layer 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 on the emission layer EML.

[0290] Then, the electron transporting layer having a thickness of 31 nm is formed on the hole blocking layer. The composition of the ETL is shown in Tables 6 and 7. The electron transport layer may comprise 50 wt.-% LiQ and 50 wt.-% of a compound of formula (II). The compound of formula (II) may be selected from 2-(4-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)-1-phenyl-1H-benzo[d]imidazole (ETM1), or 4-(4-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)naphthalen-1-yl)-[1,1-biphenyl]-4-carbonitrile (ETM2), cf Tables 6 and 7.

Then the electron injection layer (EIL) was deposited on the ETL. The composition and thickness of the EIL can be seen in Tables 5 and 6. The chemical formulae of the used compounds of formula (I) (as well as (Ia)) were described above. In examples wherein the EIL is a single layer comprising a composition comprising compound of formula (I) and/or (Ia) and the metal, the concentration is provided in wt.-%. For example Yb: LiTFSI (90:10) is synonymous with a composition comprising 90 wt.-% Yb and 10 wt.-% LiTFSI.

[0291] Then Ag:Mg (90:10 vol.-%) was evaporated at a rate of 0.01 to 1 /s at 10.sup.7 mbar to form a cathode layer with a thickness of 13 nm on the electron injection layer.

[0292] Then, N-([1,1-biphenyl]-4-yl)-9,9-dimethyl-N-(4-(9-phenyl-9H-carbazol-3-yl)phenyl)-9H-fluoren-2-amine was deposited on the cathode layer to form a capping layer 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] In bottom emission devices, the emission is predominately Lambertian and quantified in percent external quantum efficiency (EQE). The light is emitted through the anode layer. To determine the efficiency EQE in % the light output of the device is measured using a calibrated photodiode at 10 mA/cm2.

[0296] In top emission devices, the emission is forward directed through the cathode layer, non-Lambertian and also highly dependent on the mirco-cavity. Therefore, the efficiency EQE will be higher compared to bottom emission devices. To determine the efficiency EQE in % the light output of the device is measured using a calibrated photodiode at 10 mA/cm.sup.2.

[0297] The color space is described by coordinates CIE-x and CIE-y (International Commission on Illumination 1931). For blue emission the CIE-y is of particular importance. A smaller CIE-y denotes a deeper blue color. The cd/A efficiency may be dependent on the CIE-y. Therefore, the cd/A efficiency was divided by the CIE-y to obtain the colour-corrected efficiency, also named CCEff.

[0298] Lifetime LT of the device is measured at ambient conditions (20 C.) and 30 mA/cm.sup.2, using a Keithley 2400 source meter, and recorded in hours.

[0299] 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.

[0300] To determine the voltage stability over time U(100h)-(1h), a current density of at 30 mA/cm.sup.2 was applied to the device. The operating voltage was measured after 1 hour and after 100 hours, followed by calculation of the voltage stability for the time period of 1 hour to 100 hours. A low value for U(100h)-(1h) denotes a low increase in operating voltage over time and thereby improved voltage stability.

Proton Affinities

[0301] In Table 5, the proton affinity of a range of ligands L of formula (I) and/or (Ia) are shown.

TABLE-US-00004 TABLE 5 Proton affinity of ligand L of formula (I) and/or (Ia) and comparative ligand Proton Affinity Proton Affinity calculated with calculated with Turbomole Name Chemical formula ORCA [eV] [eV] G1 [00141] 13.4 13.4 G4 [00142] 13.2 G5 [00143] 13.3 13.3 G48 [00144] 13.6 13.5 G80 [00145] 14.9 G77 [00146] 15.0 G76 [00147] 14.8 G54 [00148] 14.6 G70 [00149] 15.5 G71 [00150] 15.4 G72 [00151] 15.0 G73 [00152] 15.2 G74 [00153] 14.6 G75 [00154] 15.3 G90 [00155] 14.2 G82 [00156] 14.1 Comparative ligand 1 CL-1 [00157] 15.4

[0302] As can be seen in Table 5, the proton affinity of a wide range of ligands has been calculated. When ligand L of formula (I) and/or (Ia) is selected in this range, particularly efficient electron injection from the cathode layer into the electron transport layer may be achieved.

[0303] Comparative ligand 1, also named quinolate, is a ligand known in the art (cf. Table 6 and 7). The proton affinity is 15.4 eV. Comparative ligand 1 is free of fluorine atoms. As can be seen in Table 6, the performance is improved of compounds of formula (I) and/or (Ia) compared to lithium quinolate, also named LiQ.

Technical Effect of the Invention

[0304] Table 6 shows the setup and performance of several comparative and inventive examples.

[0305] In Comparative examples C-1a to C-1c several setups of an organic luminescent device were used, whereby in C-1a only Yb (a metal) was used in the EIL, in C-1b a first EIL sub-layer comprising a metal complex (LiQ) together with a second sub-layer of Yb and in C-1c merely LiTFSI without having a second EIL

[0306] In the inventive examples E-1a and E-1b, LiTFSI and Yb were used, once as separate sub-layers (E-1a), once in a single layer (E-1b). Compared to the comparative examples, the voltage stability was decreased, in case of C-1a and C-1c even significantly decreased.

[0307] Table 7 shows the setup and performance of several further comparative and inventive examples.

[0308] In Table 6, for every comparative example C-X corresponding inventive examples E-X were investigated, where sometimes, as with inventive examples E-1a and E-1b both a dual layer and a single layer setup was investigated.

[0309] It can be seen that, depending on the example, one or more properties of the corresponding organic luminescent device are greatly improved.

TABLE-US-00005 TABLE 6 Setup and performance of several comparative and inventive examples ETL U(100 h)- Thickness EIL Voltage at CCEff at LT97 at (1 h) at ETL ETL Composition Thickness Thickness 10 mA/cm.sup.2 10 mA/cm.sup.2 30 mA/cm.sup.2 30 mA/cm.sup.2 (wt/wt.-%) [nm] EIL1 EIL1 [nm] EIL2 EIL2 [nm] [V] [cd/A] [h] [V] C-1a ETM1:LiQ 31 Yb 2 3.97 143 84 0.058 (50:50) C-1b ETM1:LiQ 31 LiQ 1 Yb 2 3.98 141 88 0.056 (50:50) C-1c ETM1:LiQ 31 LiTFSI 1 8.94 89 3 0.652 (50:50) E-1 ETM1:LiQ 31 LiTFSI 1 Yb 2 3.95 148 81 0.044 (50:50) E-2 ETM1:LiQ 31 Yb:LiTFSI 2 3.97 148 85 0.050 (50:50) (90:10)

TABLE-US-00006 TABLE 7 Setup and performance of several comparative and inventive examples ETL U(100 h)- Thickness EIL Voltage at CCEff at LT97 at (1 h) at ETL ETL Composition Thickness Thickness 10 mA/cm.sup.2 10 mA/cm.sup.2 30 mA/cm.sup.2 30 mA/cm.sup.2 (wt/wt.-%) [nm] EIL1 EIL1 [nm] EIL2 EIL2 [nm] [V] [cd/A] [h] [V] C-2 ETM1:LiQ 31 I-4 1 8.30 101 2 1.062 (50:50) E-2a ETM1:LiQ 31 I-4 1 Yb 2 3.93 149 77 0.042 (50:50) E-2b ETM1:LiQ 31 Yb:I-4 3.94 149 84 0.044 (50:50) (90:10) C-3 ETM1:LiQ 31 I-5 1 4.32 124 2 1.874 (50:50) E-3 ETM1:LiQ 31 Yb:I-5 2 3.94 151 96 0.047 (50:50) (90:10) C-4 ETM1:LiQ 31 I-7 1 4.03 142 44 0.169 (50:50) E-4 ETM1:LiQ 31 Yb:I-7 2 3.96 152 96 0.048 (50:50) (90:10) C-5 ETM1:LiQ 31 I-6 1 4.88 120 2 1.558 (50:50) E-5a ETM1:LiQ 31 I-6 1 Yb 2 3.95 151 70 0.042 (50:50) E-5b ETM1:LiQ 31 Yb:I-6 2 4.00 154 97 0.052 (50:50) (90:10) C-6 ETM2:LiQ 31 LiTFSI 1 8.58 103 5 0.495 (50:50) E-6a ETM2:LiQ 31 LiTFSI 1 Yb 2 3.94 158 103 0.035 (50:50) E-6b ETM2:LiQ 31 Yb:LiTFSI 2 3.95 157 109 0.044 (50:50) (90:10) C-7 ETM2:LiQ 31 I-1 1 9.10 99 3 1.024 (50:50) E-7a ETM2:LiQ 31 I-1 1 Yb 2 3.82 164 78 0.050 (50:50) E-7b ETM2:LiQ 31 Yb:I- 2 3.88 165 104 0.052 (50:50) 1(90:10) C-8 ETM2:LiQ 31 I-2 1 9.63 95 5 0.575 (50:50) E-8a ETM2:LiQ 31 I-2 1 Yb 2 3.85 164 90 0.042 (50:50) E-8b ETM2:LiQ 31 Yb:I-2 2 3.91 166 110 0.052 (50:50) (90:10) C-9 ETM2:LiQ 31 I-8 1 >10 (50:50) E-9a ETM2:LiQ 31 I-8 1 Yb 2 3.97 163 100 0.025 (50:50) E-9b ETM2:LiQ 31 Yb:I-8 2 4.04 165 133 0.034 (50:50) C-10 ETM2:LiQ 31 I-3 1 4.34 124 2 0.693 (50:50) E-10a ETM2:LiQ 31 I-3 1 Yb 2 3.89 155 102 0.037 (50:50) E-10b ETM2:LiQ 31 Yb:I-3 2 3.94 157 121 0.042 (50:50) (90:10) C-11 ETM2:LiQ 31 I-4 1 8.10 112 3 1.046 (50:50) E-11a ETM2:LiQ 31 I-4 1 Yb 2 3.89 160 96 0.028 (50:50) E-11b ETM2:LiQ 31 Yb:I-4 2 3.91 162 106 0.028 (50:50) (90:10) C-12 ETM2:LiQ 31 I-5 1 4.62 133 2 1.563 (50:50) E-12a ETM2:LiQ 31 I-5 1 Yb 2 3.91 161 93 0.027 (50:50) E-12b ETM2:LiQ 31 Yb:I-5 2 3.97 161 124 0.041 (50:50) (89:11) C-13 ETM2:LiQ 31 I-7 1 4.09 142 106 0.189 (50:50) E-13 ETM2:LiQ 31 Yb:I-7 2 3.95 158 124 0.038 (50:50) (90:10) C-14 ETM2:LiQ 31 I-6 1 4.35 128 4 1.088 (50:50) E-14 ETM2:LiQ 31 Yb:I-6 2 3.94 161 116 0.040 (50:50) (90:10)
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.