Metal Complex, Semiconductor Layer Comprising a Metal Complex and Organic Electronic Device
20240383935 ยท 2024-11-21
Inventors
Cpc classification
C07C255/17
CHEMISTRY; METALLURGY
H10K85/331
ELECTRICITY
Y02E10/549
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
International classification
Abstract
The present invention relates to a metal complex, a semiconductor layer comprising the metal complex and an organic electronic device comprising at least one metal complex thereof.
Claims
1. A metal complex of formula (I)
Fe.sup.3?O(L.sup.?).sub.3(AL).sub.n(I), wherein L has formula (II) ##STR00045## whereby R.sup.1 is selected from substituted C.sub.2 to C.sub.12 alkyl, substituted C.sub.6 to C.sub.19 aryl, substituted or unsubstituted C.sub.2 to C.sub.20 heteroaryl, or substituted or unsubstituted 6-membered heteroaryl; R.sup.2 is selected from substituted C.sub.6 to C.sub.19 aryl, substituted or unsubstituted C.sub.2 to C.sub.20 heteroaryl, substituted or unsubstituted 6-membered heteroaryl; wherein at least one of the substituents of the substituted C.sub.1 to C.sub.12 alkyl, substituted C.sub.6 to C.sub.19 aryl, substituted C.sub.2 to C.sub.20 heteroaryl, or substituted 6-membered heteroaryl are independently selected from halogen, Cl, F, CN, partially or perfluorinated C.sub.1 to C.sub.8 alkyl, partially or perfluorinated C.sub.1 to C.sub.8 alkoxy; wherein L comprises at least two CF.sub.3 groups and/or at least one N atom; and wherein AL is an ancillary ligand which coordinates to the metal M; n is an integer selected from 0 to 2.
2. The metal complex of formula (I) according to claim 1, whereby R.sup.1 is selected from substituted C.sub.6 to C.sub.19 aryl, substituted or unsubstituted C.sub.2 to C.sub.20 heteroaryl, or substituted or unsubstituted 6-membered heteroaryl.
3. The metal complex of formula (I) according to claim 1, wherein R.sup.1 and R.sup.2 are identical.
4. The metal complex of formula (I) according to claim 1, wherein R.sup.1 and/or R.sup.2 are selected from one of the following groups D1 to D70 (in consideration of the above provisos for L): ##STR00046## ##STR00047## ##STR00048## ##STR00049## ##STR00050## ##STR00051## ##STR00052## ##STR00053## ##STR00054## wherein the * denotes the binding position.
5. The metal complex of formula (I) according to claim 1, wherein the ligand L is selected from one of the following groups L1 to L54: ##STR00055## ##STR00056## ##STR00057## ##STR00058## ##STR00059## ##STR00060## ##STR00061## ##STR00062## ##STR00063## ##STR00064## ##STR00065##
6. An organic semiconductor layer, whereby the organic semiconductor layer comprises a metal complex of formula (I) of claim 1.
7. An organic electronic device comprising an anode layer, a cathode layer, and at least one organic semiconductor layer, wherein the at least one organic semiconductor layer is arranged between the anode layer and the cathode layer, and wherein the at least one organic semiconductor layer is the organic semiconductor layer according to claim 6.
8. An organic electronic device according to claim 7, whereby the anode layer comprises at least a first anode sub-layer and a second anode sub-layer.
9. The organic electronic device of claim 7, whereby the organic electronic device further comprises at least one photoactive layer, wherein the at least one photoactive layer is arranged between the anode layer and the cathode layer.
10. The organic electronic device according to claim 7, whereby the photoactive layer is a light emitting layer.
11. The organic electronic device of claim 7, whereby the organic electronic device is an electroluminescent device, an organic light emitting diode (OLED), a light emitting device, thin film transistor, a battery, a display device or an organic photovoltaic cell (OPV).
12. A display device comprising an organic electronic device according to claim 7.
13. A compound of formula (IIa) ##STR00066## whereby R.sup.a is selected from substituted C.sub.2 to C.sub.12 alkyl, substituted C.sub.6 to C.sub.19 aryl, substituted or unsubstituted C.sub.2 to C.sub.20 heteroaryl, or substituted or unsubstituted 6-membered heteroaryl; R.sup.b is selected from substituted C.sub.2 to C.sub.20 heteroaryl or substituted 6-membered heteroaryl; wherein at least one of the substituents of the substituted C.sub.1 to C.sub.12 alkyl, substituted C.sub.6 to C.sub.19 aryl, substituted C.sub.2 to C.sub.20 heteroaryl, or substituted 6-membered heteroaryl are independently selected from halogen, Cl, F, CN, partially or perfluorinated C.sub.1 to C.sub.8 alkyl, partially or perfluorinated C.sub.1 to C.sub.8 alkoxy; wherein the compound comprises at least two CF.sub.3 groups and/or at least one N atom.
14. The compound of claim 13, whereby R.sup.b is selected from the formulae D38 to D68.
15. The compound of claim 13, whereby R.sup.a is selected from substituted C.sub.2 to C.sub.12 alkyl and substituted C.sub.6 to C.sub.19 aryl and R.sup.b is selected from formulae D39, D42, D45, D48, D56, D57, D58, D67.
Description
DESCRIPTION OF THE DRAWINGS
[0298] 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.
[0299] 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 embodiment 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.
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[0301]
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[0303]
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[0305]
[0306] Hereinafter, the figures are illustrated in more detail with reference to examples. However, the present disclosure is not limited to the following figures.
[0307] 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.
[0308]
[0309]
[0310]
[0311]
[0312] Referring to
[0313]
[0314]
[0315] While not shown in
[0316] 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.
Calculated LUMO of the Metal Complex of Formula (I)
[0317] The HOMO and LUMO are calculated with the program package ORCA V5.0.3 (Max Planck Institute fuer Kohlenforschung, Kaiser Wilhelm Platz 1, 45470, Muelheim/Ruhr, Germany) and WEASEL 1.9.2 (FAccTs GmbH, Rolandstrasse 67, 50677 Koln, Germany). The optimized geometries and the HOMO and LUMO energy levels of the molecular structures are determined by applying the hybrid functional (Gaussian)-B3LYP with a ZORA-Def2-TZVP basis set with inclusion of solvent effects via conductor-like polarizable continuum model (CPCM) and as solvent acetonitrile. If more than one conformation is viable, the conformation with the lowest total energy is selected. The structures of all the molecules were optimized without symmetry or internal constrains and were verified as true minima by the absence of negative eigenvalues in the harmonic vibrational frequency analysis.
HOMO and LUMO Levels of the Matrix Compound and/or Compound of Formula (IV) or (V)
[0318] The HOMO and LUMO levels of the matrix compound and/or compound of formula (IV) or (V) 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.
Experimental Data
[0319] Metal complexes and compounds of the present invention may be prepared using methods as described below or by methods known in the art.
General Method for the Preparation of Ligands HL
[0320] ##STR00037##
[0321] The HL precursor may be prepared by methods known in the art.
[0322] To a solution of HL precursor and K.sub.2CO.sub.3 in aqueous THF was added TsCN in one portion and the resulting mixture was stirred at RT for 3 h. The reaction mixture was concentrated under vacuum. The residue was stirred in DCM/water, the formed suspension was filtered, white solid was washed with 2?100 ml water and 100 ml DCM and dried. The product was stirred in 2M HCl/DCM mixture for 1 h. After separation of the layers, the organic phase was washed with 100 ml 2M HCl. Combined aqueous layers were washed with 200 ml DCM. Combined organic phases were washed with 300 ml water, dried over MgSO4, filtered and concentrated to give solid which was treated with hexane/diethyl ether. The solid was filtered off and dried in vacuum to yield HL.
TABLE-US-00001 Yield Purity by Chemical formula of HL [%] HPLC [%]
General Method for Preparation of Metal Complexes of Formula (I)
[0323] ##STR00042##
[0324] 3 equivalents HL was dissolved in methanol and 3 equivalents sodium bicarbonate was added. 1 equivalent iron trichloride was dissolved in water and added to the mixture under cooling. The mixture was stirred at room temperature overnight. The precipitate was filtered off, washed with water and dried in high vacuum.
TABLE-US-00002 Metal complex Purity by of formula (I) Yield [%] HPLC [%] MC-1 24 >94 MC-2 64 >98 MC-3 80 >98 MC-4 20 >94
[0325] The metal complexes of formula (I) may be purified further by methods known in the art prior to use in organic electronic devices, for example by distillation or sublimation in vacuum.
General Procedure for Fabrication of OLEDs
General Method for Preparation of the Ink Formulation
[0326] To prepare the ink formulation, the compounds were weighed into vials. Then, the solvent was added. The mixture was stirred for 10 min. The inks were transferred to inert atmosphere. An aliquot of benzonitrile solutions was added to the anisole solution to obtain a solution with a ratio of 5:1 of anisole to benzonitrile solution. The resulting solution was stirred again for at least 10 min at room temperature. The resulting ink formulation had a solid content of 4 wt.-%.
Ink Formulation for Comparative Example 1-1
[0327] The ink formulation for example 1-2 has the following composition: 4 wt.-% CC1:96 wt.-% K1 in anisole:benzonitrile (5:1). To prepare the ink, solutions of 12.4 mg (2 mol.-%, 2.35 wt. %) CC1 in 3 ml benzonitrile and 121 mg K1 in 3.3 ml anisole were prepared as described above. 0.7 ml benzonitrile solution was added to the anisole solution and stirred as described above.
Ink Formulation for Inventive Example 1-1
[0328] The ink formulation for example 1-x has the following composition: 4 wt.-% MC-2:K1 in anisole:benzonitrile (5:1). To prepare the ink, solutions of 16.3 mg (2 mol. %, 4.63 wt.-%) MC-2 in 2 ml benzonitrile and 118 mg K1 in 3.3 ml anisole were prepared as described above. 0.7 ml benzonitrile solution was added to the anisole solution and stirred as described above.
Ink Formulation for Inventive Example 1-2
[0329] The ink formulation for example 1-1 has the following composition: 4 wt.-% MC-3:96 wt.-% K1 in anisole:benzonitrile (5:1). To prepare the ink, solutions of 12.4 mg (2 mol.-%, 3.52 wt. %) MC-3 in 2 ml benzonitrile and 119 mg K1 in 3.3 ml anisole were prepared as described above. 0.7 ml benzonitrile solution was added to the anisole solution and stirred as described above.
General Procedure for Organic Electronic Devices Wherein the Semiconductor Layer is Deposited from Solution
[0330] For inventive example 1-1 and 1-2 and comparative examples 1-1, see Table 2, a 15 ?/cm.sup.2 glass substrate with 90 nm ITO (available from Corning Co.) with the dimensions 150 mm?150 mm?0.7 mm was ultrasonically washed with isopropyl alcohol for 5 minutes and then with pure water for 5 minutes and dried at elevated temperature.
[0331] Then, the metal complex and the matrix compound were co-deposited from solution on the anode layer, to form a hole injection layer (HIL) having a thickness of 50 nm. The formulae of the metal complexes can be seen in Table 1.
[0332] To form the hole injection layer, the substrate is placed on a spin-coater with ITO side facing upwards and fixed with vacuum. The ink is prepared as described above under general method. 4 ml of ink formulation is applied with a syringe with filter (PTFE-0.2 ?m) on the substrate. Spin-coating parameter are 850 rpm (3 sec ramp-up from zero to maximum speed) for 30 sec. The resulting film is dried at 60? C. for 1 minute on a hotplate. Next step is the cleaning of the substrate around the active area (to ensure a good encapsulation before measurement). An additional bake-out at 100? C. for 10 minutes on a hotplate is done. The composition of the hole injection layer can be seen in Table 2.
[0333] Then, the substrate is transferred to an evaporation tool for deposition of subsequent layers.
[0334] Then, N-([1,1-biphenyl]-4-yl)-9,9-dimethyl-N-(4-(9-phenyl-9H-carbazol-3-yl)phenyl)-9H-fluoren-2-amine was vacuum deposited on the HIL, to form a HTL having a thickness of 88 nm.
[0335] Then 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.
[0336] Then 97 vol.-% H09 as EML host and 3 vol.-% BD200 (Sun Fine Chemicals, Korea) as fluorescent blue emitter dopant were deposited on the EBL, to form a blue-emitting first emission layer (EML) with a thickness of 20 nm.
[0337] 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.
[0338] Then the electron transporting layer having a thickness of 31 nm was formed on the hole blocking layer by depositing 50 wt.-% 4-(4-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)naphthalen-1-yl)-[1,1-biphenyl]-4-carbonitrile and 50 wt.-% of LiQ.
[0339] Then Al 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 100 nm on the electron transporting layer.
[0340] 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.
General Procedure for Fabrication of Organic Electronic Devices Wherein the Semiconductor Layer is Deposited in Vacuum
[0341] For inventive examples 2-1 to 2-16 and comparative example 2-1 to 2-5, see Table 3, 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 mm?50 mm?0.7 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.
[0342] Then, the metal complex and the matrix compound were co-deposited in vacuum on the anode layer, to form a hole injection layer (HIL) having a thickness of 10 nm. The matrix compound may be a compound of formula (IV) or (V) The composition of the hole injection layer can be seen in Table 3. The formulae of the metal complexes can be seen in Table 1.
[0343] Then, the matrix compound was vacuum deposited on the HIL, to form a HTL having a thickness of 128 nm. The matrix compound in the HTL is selected the same as the matrix compound in the HIL. The matrix compound in the HIL can be seen in Table 3.
[0344] Then N,N-di([1,1-biphenyl]-4-yl)-3-(9H-carbazol-9-yl)-[1,1-biphenyl]-4-amine (CAS 1464822-27-2) was vacuum deposited on the HTL, to form an electron blocking layer (EBL) having a thickness of 5 nm.
[0345] Then 99 vol.-% blue emitter host BH1 (CAS 2457172-82-4) and 1 vol.-% BD1 (CAS 2482607-57-6) as blue emitter dopant were co-deposited on the EBL, to form a blue-emitting first emission layer (EML) with a thickness of 20 nm.
[0346] 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.
[0347] Then the electron transporting layer (ETL) having a thickness of 31 nm was formed on the hole blocking layer by depositing 50 wt.-% 2-(2,6-diphenyl-[1,1:4,1-terphenyl]-4-yl)-4-phenyl-6-(3-(pyridin-4-yl)phenyl)-1,3,5-triazine and 50 wt.-% of LiQ.
[0348] Then Yb was deposited on the ETL to form an electron injection layer (EIL) having a thickness of 2 nm.
[0349] 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.
[0350] 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.
[0351] 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.
[0352] 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.
[0353] 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.
[0354] 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.
[0355] 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.
[0356] 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.
[0357] To determine the voltage stability over time U(100 h)-(1 h), 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(100 h)-(1 h) denotes a low increase in operating voltage over time and thereby improved voltage stability.
Technical Effect of the Invention
[0358] In Table 1 are shown the calculated LUMO in electron volt of metal complexes of formula (I). Where more than one spin state is viable, the spin state is stated in brackets. As can be seen in Table 1, the LUMO levels of metal complexes of formula (I) are within the range suitable for organic electronic devices.
[0359] Also in Table 1 are shown calculated LUMO in electron volt of comparative compounds CC1 and CC2. The same method was used as for metal complexes of formula (I).
[0360] Comparative compound CC1 has the formula below:
##STR00043##
[0361] Comparative compound CC1 is lacking at least two CF.sub.3 groups and/or at least one N atom. As can be seen in Table 1, the LUMO level is closer to vacuum level than LUMO energies of metal complexes of formula (I).
[0362] Comparative compound CC2 has the formula below:
##STR00044##
[0363] Comparative compound CC2 is lacking the CN group in formula (II). As can be seen in Table 1, the LUMO level is closer to vacuum level than LUMO energies of metal complexes of formula (I).
[0364] Without being bound by theory, a LUMO energies further away from vacuum level is beneficial for improved performance of organic electronic devices.
TABLE-US-00003 TABLE 1 LUMO values of metal complexes according to Formula (I) and comparative compounds 1 and 2 Structure (if not LUMO [eV] Name already disclosed) (spin) Comparative CC1 ?4.09 eV (?) compound 1 Comparative CC2 ?3.92 eV (?) compound 2 Inventive MC-1 L52 ?4.67 eV (?) compound 1 Inventive MC-2 L1 ?4.48 eV (?) compound 2 Inventive MC-3 L9 ?4.63 eV (?) compound 3 Inventive MC-4 L10 ?4.80 eV (?) compound 4 Inventive MC-5 L11 ?4.63 eV (?) compound 5
[0365] In Table 2 are shown data for bottom emission organic electronic devices fabricated by co-deposition from solution of a composition comprising metal complex of formula (I) or comparative compound CC1 and matrix compound K1.
[0366] In comparative example 1-1, a metal complex known in the art is tested at 2 mol.-%. As can be seen in Table 2, in comparative example 1-1 the operating voltage is 6.63 V, the external quantum efficiency EQE is less than 5%. Due to the very high operating voltage and very poor efficiency, the lifetime and voltage stability over time were not determined.
[0367] In inventive example 1-1, solution processing of a composition comprising metal complex of formula (I) MC-2 and matrix compound K1 was attempted. However, no layer was formed. Therefore, this metal complex was deposited from vacuum in subsequent inventive examples, see Table 3.
[0368] In inventive example 1-2, a composition comprising metal complex of formula (I) MC-3 and matrix compound K1 was assessed. As can be seen in Table 2, the operating voltage is improved to 3.65 V, cd/A the EQE is improved to 10.28%, the lifetime is improved to 119 hours and operating voltage stability over time is improved to 0.404 V.
[0369] In Table 3 are shown data for top emission organic electronic devices fabricated by co-deposition from vacuum of the metal complex and the matrix compound.
[0370] In comparative example 2-1 to 2-5, a second metal complex known in the art is tested at concentrations in the range of 8 to 18 wt.-%.
[0371] As can be seen in Table 3, in comparative examples 2-1 to 2-5 the operating voltage is in the range of 3.52 to 3.54 V, the cd/A efficiency is in the range of 9.76 to 10.15 cd/A, the external quantum efficiency EQE is in the range of 19.59 to 20.42% and the voltage stability over time is in the range of 1.52 to 2.67 V.
[0372] In inventive example 2-1, the semiconductor layer comprises a metal complex of formula (I) MC-2. The matrix compound is the same as in comparative examples 2-1 to 2-5. The concentration of metal complex of formula (I) in the layer is 1.5 wt.-% As can be seen in Table 3, the operating voltage is improved to 3.47 V, cd/A efficiency is 10.52 cd/A, the EQE is 20.73%, the lifetime is 82 hours and operating voltage stability over time is improved to 0.11 V.
[0373] In inventive examples 2-2 to 2-7, the concentration of metal complex of formula (I) MC-2 has been varied from 2 to 14 wt.-%. As can be seen in Table 3, the operating voltage, is improved to 3.4 to 3.44 V compared to comparative examples 2-1 to 2-5. The cd/A efficiency is improved to 10.27 to 10.65 cd/A. The EQE is improved to 20.31 to 20.73%, the lifetime is in the range of 71 to 91 hours. The voltage stability over time is improved substantially to 0.04 to 0.11 V.
[0374] In inventive examples 2-8 to 2-11, the semiconductor layer comprises matrix compound K7. K7 has a HOMO level further away from vacuum level, namely ?4.84 eV compared to ?4.73 for K16. The concentration of metal complex of formula (I) MC-2 has been varied from 10 to 16 wt.-%. As can be seen in Table 3, the operating voltage, is improved to 3.38 to 3.44 V compared to comparative examples 2-1 to 2-5. The cd/A efficiency and EQE are lower than in comparative examples 2-1 to 2.5. However, the lifetime is substantially improved to 159 to 215 hours. The voltage stability over time is improved substantially to 0.07 to 0.18 V.
[0375] In inventive examples 2-12 to 2-16, the semiconductor layer comprises matrix compound K2. K2 has a HOMO level further away from vacuum level, namely ?4.85 eV compared to ?4.73 for K16. The concentration of metal complex of formula (I) MC-2 has been varied from 4 to 19 wt.-%. As can be seen in Table 3, the operating voltage, is improved to 3.33 to 3.35 V compared to comparative examples 2-1 to 2-5. The cd/A efficiency and EQE are in a similar range to comparative examples 2-1 to 2.5. However, the lifetime is improved to 92 to 114 hours. The voltage stability over time is improved substantially to 0.03 to 0.21 V.
[0376] A low operating voltage, high efficiency, high lifetime and/or improved operating voltage stability over time are important for the performance and long-term stability of organic electronic devices.
TABLE-US-00004 TABLE 2 Performance of an organic electroluminescent device prepared via deposition of the semiconductor layer from solution Percentage Percentage metal HOMO matrix Semicon- complex in level of compound in ductor Voltage U(100 h)- semicon- matrix semicon- layer at EQE at LT97 at (1h) at Metal ductor Matrix compound ductor thickness 10 mA/cm.sup.2 10 mA/cm.sup.2 30 mA/cm.sup.2 30 mA/cm.sup.2 complex layer [wt.-%] compound [eV] layer [wt.-%] [nm] [V] [%] [h] [V] Comparative CC1 4 K1 ?4.68 96 50 6.63 <5 n.d. .sup.1 n.d example 1-1 Inventive MC-2 4 K1 ?4.68 96 No layer n.d. n.d. n.d. n.d. example formed 1-1 Inventive MC-3 4 K1 ?4.68 96 50 3.65 10.28 119 0.404 example 1-2 .sup.1 n.d. = not determined
TABLE-US-00005 TABLE 3 Performance of an organic electroluminescent device prepared via deposition of the semiconductor layer in vacuum Percentage Percentage metal HOMO matrix Cd/A complex in level of compound in efficiency U(100 h)- semicon- matrix semicon- Voltage at at EQE at LT97 at (1 h) at Metal ductor Matrix compound ductor 10 mA/cm.sup.2 10 mA/cm.sup.2 10 mA/cm.sup.2 30 mA/cm.sup.2 30mA/cm.sup.2 complex layer [wt.-%] compound [eV] layer [wt.-%] [V] [cd/A] [%] [h] [V] Comparative CC2 8 K16 ?4.73 92 3.54 9.84 19.87 72 1.67 example 2-1 Comparative CC2 10 K16 ?4.73 90 3.53 9.98 19.77 71 1.52 example 2-2 Comparative CC2 13 K16 ?4.73 87 3.52 9.76 19.59 75 1.73 example 2-3 Comparative CC2 16 K16 ?4.73 84 3.54 10.15 20.42 85 2.67 example 2-4 Comparative CC2 18 K16 ?4.73 82 3.53 10.09 20.38 81 2.55 example 2-5 Comparative CC2 23 K16 ?4.73 77 3.52 9.99 20.38 81 2.34 example 2-6 Inventive MC?2 1.5 K16 ?4.73 98.5 3.47 10.52 20.73 82 0.11 example 2-1 Inventive MC?2 2 K16 ?4.73 98 3.44 10.44 20.66 80 0.08 example 2-2 Inventive MC?2 4 K16 ?4.73 96 3.42 10.65 20.53 70 0.05 example 2-3 Inventive MC?2 6 K16 ?4.73 94 3.40 10.52 20.54 71 0.04 example 2-4 Inventive MC?2 9 K16 ?4.73 91 3.40 10.41 20.39 91 0.06 example 2-5 Inventive MC?2 11 K16 ?4.73 89 3.40 10.27 20.41 82 0.05 example 2-6 Inventive MC?2 14 K16 ?4.73 86 3.40 10.27 20.31 83 0.05 example 2-7 Inventive MC?2 10 K7 ?4.84 90 3.38 8.45 18.00 172 0.18 example 2-8 Inventive MC?2 12 K7 ?4.84 88 3.44 8.88 18.16 214 0.13 example 2-9 Inventive MC?2 14 K7 ?4.84 86 3.43 8.87 18.18 178 0.09 example 2-10 Inventive MC?2 16 K7 ?4.84 84 3.42 8.87 18.20 159 0.07 example 2-11 Inventive MC?2 8 K2 ?4.85 92 3.35 9.90 19.81 113 0.21 example 2-12 Inventive MC?2 10 K2 ?4.85 90 3.35 9.76 19.45 114 0.17 example 2-13 Inventive MC?2 12 K2 ?4.85 88 3.33 9.88 19.81 107 0.11 example 2-14 Inventive MC?2 15 K2 ?4.85 85 3.34 9.76 19.50 93 0.05 example 2-15 Inventive MC?2 19 K2 ?4.85 81 3.34 9.64 19.46 92 0.03 example 2-16
[0377] 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.