Ink composition for forming an organic layer of a semiconductor

Abstract

The present invention is directed to an ink composition for forming an organic semiconductor layer, wherein the ink composition comprises: —at least one p-type dopant comprising electron withdrawing groups; —at least one first auxiliary compound, wherein the first auxiliary compound is an aromatic nitrile compound, wherein the aromatic nitrile compound has about ≥1 to about ≤3 nitrile groups and a melting point of about <100° C., wherein the first auxiliary compound is different from the p-type dopant; and wherein the electron withdrawing groups are fluorine, chlorine, bromine and/or nitrile.

Claims

1. An ink composition for forming an organic semiconductor layer, wherein the ink composition comprises: at least one p-type dopant comprising electron withdrawing groups; at least one first auxiliary compound, wherein the first auxiliary compound is an aromatic nitrile compound, wherein the aromatic nitrile compound has about ≥1 to about ≤3 nitrile groups and a melting point of about ≤100° C., wherein the first auxiliary compound is different from the p-type dopant; wherein the electron withdrawing groups are fluorine, chlorine, bromine and/or nitrile; wherein the ink composition is a homogeneous solution in which the at least one p-type dopant is dissolved by the at least one first auxiliary compound; and wherein the ink composition comprises about ≥0.00001 wt.-% to about ≤2 wt.-% of the at least one p-type dopant, based on the total weight of the ink composition.

2. The ink composition according to claim 1, wherein the ink composition comprises: at least one p-type dopant comprising electron withdrawing groups, and which is solid at about ≥100° C.; at least one organic charge transport material, which is solid at about ≥100° C., and wherein the organic charge transport material is different from the p-type dopant; at least one first auxiliary compound, wherein the first auxiliary compound is an aromatic nitrile compound, wherein the aromatic nitrile compound has about ≥1 to about ≤3 nitrile groups and a melting point of about <100° C., wherein the first auxiliary compound is different from the p-type dopant; and wherein the electron withdrawing groups are fluorine, chlorine, bromine and/or nitrile.

3. An ink composition according to claim 1, wherein the ink composition comprises: at least one p-type dopant, having about ≥4 atoms and wherein the amount of electron withdrawing groups in the sum formula of the at least one p-type dopant is about ≥17 atomic percent to about ≤90 atomic percent; at least one organic charge transport material, having about ≥4 atoms and wherein the amount of electron withdrawing groups in the sum formula of the at least one organic charge transport material is ≥0 to about <17 atomic percent and having a melting point of about ≥100° C.; at least one first auxiliary compound, wherein the first auxiliary compound is an aromatic nitrile compound, wherein the aromatic nitrile compound has about ≥1 to about ≤3 nitrile groups and a melting point of about <100° C., wherein the first auxiliary compound is different from the p-type dopant; and wherein the electron withdrawing groups are fluorine, chlorine, bromine and/or nitrile.

4. The ink composition according to claim 1, wherein the at least one p-type dopant has about ≥3 to about ≤100 electron withdrawing groups.

5. The ink composition according to claim 1, wherein the molecular mass of the p-type dopant is in the range of about ≥60 g/mol to about ≤5000 g/mol.

6. The ink composition according to claim 1, wherein the ink composition comprises at least two organic charge transport materials, of at least a first organic charge transport material and of at least a second organic charge transport material, wherein the molecular mass of the first organic charge transport material is lower than the molecular mass of the second organic charge transport material.

7. The ink composition according to claim 6, wherein the average molecular mass of the first organic charge transport material is in the range of about ≥300 g/mol to about ≤1500 g/mol; and/or the average molecular mass of the second organic charge transport material is in the range of ≥600 g/mol to about ≤2,000,000; wherein the molecular mass of the first organic charge transport material is lower than the molecular mass of the second organic charge transport material.

8. The ink composition according to claim 1, wherein the at least one first auxiliary compound is selected from the group comprising substituted or unsubstituted benzonitrile, alkylbenzonitrile, methylbenzonitrile, ortho-tolunitrile, 4-butyl-benzonitrile, and the substituents are selected from alkyl, aryl or halogen.

9. The ink composition according to claim 1, wherein the molecular mass of the at least one first auxiliary compound is in the range of about ≥100 g/mol to about ≤500 g/mol.

10. The ink composition according to claim 1, wherein the ink composition comprises in addition at least one second auxiliary compound, which is liquid at about 23° C., and wherein the at least one second auxiliary compound has a chemical structure that is different from the first auxiliary compound and is different from the p-type dopant.

11. The ink composition according to claim 10, wherein the at least one second auxiliary compound is selected from the group comprising: an alkane compound, such as nonane, decane, undecane, or dodecane; an aliphatic alcohol compound, such as hexanol, heptanol, octanol, nonyl alcohol, or decyl alcohol; an aliphatic ether compound, such as dibutyl ether, dipentyl ether, diethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol isopropyl methyl ether, diethylene glycol diethyl ether, diethylene glycol butyl methyl ether, diethylene glycol dibutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol methyl propyl ether, triethylene glycol dimethyl ether, triethylene glycol ethyl methyl ether, triethylene glycol butyl methyl ether, tripropylene glycol dimethyl ether, or tetraethylene glycol dimethyl ether; an aliphatic nitrile compound such as acetonitrile, propionitrile, or butyronitrile; an aromatic hydrocarbon compound, such as 1,3-diisopropylbenzene, 1,4-diisopropylbenzene, triisopropylbenzene, pentylbenzene, hexylbenzene, cyclohexylbenzene, heptylbenzene, octylbenzene, or nonylbenzene 3-phenoxy toluene, 2-isopropyl naphthalene, dibenzyl ether, isopropyl biphenyl, or bis dimethyl phenyl ethane a fluorinated hydrocarbon compound, such as hydro-fluoro ethers or methoxy-nonafluorobutane.

12. The ink composition according to claim 1, wherein the p-type dopant is selected from the group comprising: hexaazatriphenylene substituted with at least four nitrile groups; cyanobenzoquinone-dimethanes and/or cyanobenzoquinone-diimines, which are substituted with at least four electron withdrawing groups selected from the group comprising fluorine, chlorine, bromine and/or nitrile; radialene compounds; tris(1-(pyridin-2-yl)-1H-pyrazol)cobalt(III) tris(hexafluorophosphate); Molybdenum tris-[1,2-bis(trifluoromethyl)ethane-1,2-dithiolene]; C.sub.60F.sub.48; charge neutral metal amide compounds, which are substituted with at least four electron withdrawing groups selected from the group comprising fluorine, chlorine, bromine and/or nitrile; metal organic complex.

13. The ink composition according to claim 1, wherein the p-type dopant has the following chemical formula (P1) to (P25): ##STR00033## ##STR00034## ##STR00035## ##STR00036## ##STR00037## ##STR00038## wherein M.sup.+ is a monovalent cation.

14. A method of forming an organic semiconductor layer of an organic electronic device, wherein the ink composition according to claim 1 is processed by solution-processing, spin coating, slot die coating and/or inkjet printing.

15. The method of forming an organic semiconductor layer of claim 14, wherein the organic semiconductor layer is arranged in direct contact with the anode.

16. A method of forming an organic semiconductor layer according to claim 14, wherein the method comprises the steps, forming a layer of an ink composition by solution-processing in a pixel cell of an organic electronic device, in an organic light-emitting diode pixel bank or in a solar cell pixel bank, and allowing the auxiliary compounds from the ink composition to evaporate, whereby the organic semiconductor layer is formed.

17. The ink composition according to claim 10, wherein the second auxiliary compound has a boiling point at atmospheric pressure which is ≥50° C. and ≤350° C.

18. The ink composition according to claim 1, wherein the at least one p-type dopant has about ≥4 to about ≤70 electron withdrawing groups.

19. An ink composition for forming an organic semiconductor layer, wherein the ink composition comprises: at least one p-type dopant comprising electron withdrawing groups; at least one first auxiliary compound, wherein the first auxiliary compound is an aromatic nitrile compound, wherein the aromatic nitrile compound has about ≥1 to about ≤3 nitrile groups and a melting point of about <100° C., wherein the first auxiliary compound is different from the p-type dopant; wherein the electron withdrawing groups are fluorine, chlorine, bromine and/or nitrile; wherein the ink composition is a homogeneous solution in which the at least one p-type dopant is dissolved by the at least one first auxiliary compound; and wherein the ink composition comprises: about ≥0.00001 wt.-% to about ≤2 wt.-% of the at least one p-type dopant; about ≥0.01 wt.-% to about ≤5 wt.-% of the at least one first organic charge transport material and/or second organic charge transport material; about ≥0.01 wt.-% to about ≤99.97 wt.-% of the at least one first auxiliary compound; about ≥0 wt.-% to about ≤99.97 wt.-% of the at least one second auxiliary compound; about ≥0 wt.-% to about ≤5 wt.-% of water; wherein the wt.-% is based on the total weight of the ink composition, and the total amount of all components does not exceed 100 wt.-%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) at t.sub.0 (t.sub.0=measured immediately after dissolution) in different solvents of Molybdenum tris-[1,2-bis(trifluoromethyl)ethane-1,2-dithiolene] (Mo(tfd).sub.3) of compound P20;

(2) FIG. 2 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) at t.sub.0 in different solvents of the [3]-radialene compound P11, 4,4′,4″-((1E,1′E,1″E)-cyclopropane-1,2,3-triylidenetris(cyanomethanylylidene))tris(2,3,5,6-tetrafluorobenzonitrile);

(3) FIG. 3 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) at t.sub.0 in different solvents of the [3]-radialene of compound P15, 2,2′,2″-(cyclopropane-1,2,3-triylidene)tris(2-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenyl)-acetonitrile);

(4) FIG. 4 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) at t.sub.0 in different solvents of the [3]-radialene compound P18, (2E,2′E,2″E)-2,2′,2″-(cyclopropane-1,2,3-triylidene)tris(2-(2,3,5-trifluoro-4,6-bis(trifluoromethyl)phenyl)acetonitrile);

(5) FIG. 5 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) at t.sub.0 in different solvents of the fluorinated fullerene C.sub.60F.sub.48 of compound P21.

(6) FIG. 6 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) after 1 week in different solvents of Molybdenum tris-[1,2-bis(trifluoromethyl)ethane-1,2-dithiolene] (Mo(tfd).sub.3) of compound P20;

(7) FIG. 7 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) after 1 week in different solvents of the [3]-radialene of compound P11, 4,4′,4″-((1E,1′E,1″E)-cyclopropane-1,2,3-triylidenetris(cyanomethanylylidene))tris(2,3,5,6-tetrafluorobenzonitrile);

(8) FIG. 8 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) after 1 week in different solvents of the [3]-radialene compound P15, 2,2′,2″-(cyclopropane-1,2,3-triylidene)tris(2-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenyl)-acetonitrile);

(9) FIG. 9 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) after 1 week in different solvents of the [3]-radialene compound P18, (2E,2′E,2″E)-2,2′,2″-(cyclopropane-1,2,3-triylidene)tris(2-(2,3,5-trifluoro-4,6-bis(trifluoromethyl)phenyl)acetonitrile);

(10) FIG. 10 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) with respect to the absorption intensity of [3]-radialene compound P17 in different nitrile-free solvents, comparative examples 5a to 5e, for a time period from to to 22 h ink storage;

(11) FIG. 11 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) with respect to the absorption intensity of the [3]-radialene compound P17 in different nitrile solvents (inventive examples 6a an 6b) for a time period from t.sub.0 to 22 h ink storage time;

(12) FIG. 12 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) with respect to the absorption intensity of compound P8 in toluene (comparative example 7) at t.sub.0 and t.sub.7d (7 days ink storage time);

(13) FIG. 13 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) with respect to the absorption intensity of compound P8 in anisole (comparative example 8) at t.sub.0 and t.sub.7d (7 days ink storage time);

(14) FIG. 14 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) with respect to the absorption intensity of the inventive example compound P8 in benzonitrile (inventive example 9) at t.sub.0 and t.sub.7d (7 days ink storage time);

(15) FIG. 15 shows the absorption intensity in an UV-vis absorption spectrum (350 nm to 800 nm wavelength) for the organic charge transport material of polymer-1 in anisole for a time period starts at t.sub.0 to t.sub.17h (17 h);

(16) FIG. 16 shows the absorption intensity in an UV-vis absorption spectrum (350 nm to 800 nm wavelength) for the organic charge transport material of polymer-1 in benzonitrile for a time period starts at t.sub.0 to t.sub.17h (17 h);

(17) FIG. 17 shows the intensity of the UV-vis absorption maximum at 580 nm of Molybdenum tris-[1,2-bis(trifluoromethyl) ethane-1,2-dithiolene] (Mo(tfd).sub.3) [compound P20] dissolved in acetonitril and isovaleronitril;

(18) FIG. 18 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) at t=0 and t=22 h of Molybdenum tris-[1,2-bis(trifluoromethyl) ethane-1,2-dithiolene] (Mo(tfd).sub.3) [compound P20] in different solvents of acetonitril and isovaleronitril.

(19) Hereinafter, the figures are illustrated in more detail with reference to examples. However, the present disclosure is not limited to the following figures.

(20) The stability of different p-type dopants in the aromatic nitrile solvent and aromatic nitrile free solvents were tested by UV.vis absorption spectroscopy (350 nm to 800 nm wavelength). The absorption is normalized in order to ensure direct comparability between the samples.

(21) FIG. 1 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) at t.sub.0 of Molybdenum tris-[1,2-bis(trifluoromethyl)ethane-1,2-dithiolene] (Mo(tfd).sub.3) of the p-type dopant compound P20:

(22) ##STR00020##
in an aromatic nitrile solution, which is benzonitrile, and in aromatic nitrile-free solutions, which are toluene and anisole.

(23) FIG. 2 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) at t.sub.0 of the p-type dopant compound P11:

(24) ##STR00021##
in an aromatic nitrile solution, which is benzonitrile, and in aromatic nitrile-free solutions, which are toluene and anisole.

(25) FIG. 3 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) at t.sub.0 of the p-type dopant compound P15:

(26) ##STR00022##
in an aromatic nitrile solution, which is benzonitrile, and in aromatic nitrile-free solutions, which are toluene and anisole.

(27) FIG. 4 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) at t.sub.0 of the p-type dopant compound P18:

(28) ##STR00023##
in an aromatic nitrile solution, which is benzonitrile, and in aromatic nitrile-free solutions, which are toluene and anisole.

(29) FIG. 5 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) at t.sub.0 of the p-type dopant fullerene compound C.sub.60F.sub.48 (P21), in an aromatic nitrile solution, which is benzonitrile, and in aromatic nitrile-free solutions, which are toluene and anisole.

(30) FIG. 6 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) at t.sub.0 and t.sub.7d (1 week ink storage) for the p-type dopant compound P20:

(31) ##STR00024##
under air and under N.sub.2 atmosphere in an aromatic nitrile solution, which is benzonitrile, and in aromatic nitrile-free solutions, which are toluene and anisole. It can be seen that the compound P20 is stable over one week in a nitrile-solution, which is benzonitrile. However, P20 is not storage stable over one week in a nitrile free solution, which is toluene and anisole.

(32) FIG. 7 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) at t.sub.0 and t.sub.7d (1 week ink storage) for the p-type dopant compound P11:

(33) ##STR00025##
under air and under N.sub.2 atmosphere in an aromatic nitrile solution, which is benzonitrile, and in aromatic nitrile-free solutions, which are toluene and anisole. It can be seen that the compound P11 is stable over one week in a nitrile-solution, which is benzonitrile. However, P11 is not storage stable over one week in a nitrile free solution, which is toluene and anisole.

(34) FIG. 8 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) at t.sub.0 and t.sub.7d (1 week ink storage) for the p-type dopant compound P15:

(35) ##STR00026##
under air and under N.sub.2 atmosphere in an aromatic nitrile solution, which is benzonitrile, and in aromatic nitrile-free solutions, which are toluene and anisole. It can be seen that the compound P15 is stable over one week in a nitrile-solution, which is benzonitrile. However, P15 is not storage stable over one week in a nitrile free solution, which is toluene and anisole.

(36) FIG. 9 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) at t.sub.0 and t.sub.7d (1 week ink storage) for the p-type dopant compound P18:

(37) ##STR00027##
under air and under N.sub.2 atmosphere in an aromatic nitrile solution, which is benzonitrile, and in aromatic nitrile-free solutions, which are toluene and anisole. It can be seen that the compound P18 is stable over one week in a nitrile-solution, which is benzonitrile. However, P18 is not storage stable over one week in a nitrile free solution, which is toluene and anisole.

(38) FIG. 10 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) with respect to the absorption intensity of [3]-radialene p-type dopant compound P17 comparative examples 5a to 5e in different nitrile-free solvents, comparative examples 5a to 5e, for a time period at from t0 for to 22 h ink storage. It is evident that the absorption intensity decreases over time. The decrease of intensity is caused by a reduction of the amount of absorbing compound P17 in the solution. The reduction of the amount of absorbing compound P17 in the solution is attributed to a decomposition of P17 in the solution.

(39) FIG. 11 shows the UV-vis absorption spectrum (350 nm to 800 nm wavelength) with respect to the absorption intensity of [3]-radialene p-type dopant compound P17 in different nitrile solvents, inventive examples 6a and 6b, for a time period at from t0 for to 22 h ink storage. It is evident that the absorption intensity remains constant at high level (>97%) over time (6a) or increases (6b). Constant absorption intensity (6a) is attributed to constant amount of absorbing compound P17 in the solution over time. P17 is stable in the solution. Increasing absorption intensity (6b) is attributed to increasing amount of absorbing compound P17 in the solution over time. This is indicative of a slow dissolution of P17. After about 17 hours the absorption intensity reaches a constant and high (>97%) level. P17 is stable in the solution.

(40) FIG. 12 shows the absorption intensity in an UV-vis absorption spectrum (350 nm to 800 nm wavelength) for the p-type dopant compound P8:

(41) ##STR00028##
in toluene—comparative example 7—at t.sub.0 and t.sub.7d (7 days ink storage). The absorption intensity reduces. It can be clearly seen that the compound P8 is not stable over time in a nitrile-free solution, which is toluene.

(42) FIG. 13 shows the absorption intensity in an UV-vis absorption spectrum (350 nm to 800 nm wavelength) for the p-type dopant compound P8:

(43) ##STR00029##
in anisole—comparative example 8—at t.sub.0 and t.sub.7d (7 days ink storage). The absorption intensity reduces. It can be clearly seen that the compound P8 is not stable over time in a nitrile-free solution, which is anisole.

(44) FIG. 14 shows the absorption intensity in an UV-vis absorption spectrum (350 nm to 800 nm wavelength) for the p-type dopant compound P8:

(45) ##STR00030##
in benzonitrile—inventive example 9—at t.sub.0 and t.sub.7d (7 days ink storage). The absorption remains constant over time. It can be clearly seen that the compound P8 is stable over time in a nitrile solution, which is benzonitrile.

(46) FIG. 15 shows the absorption intensity in an UV-vis absorption spectrum (350 nm to 800 nm wavelength) for the organic charge transport material of polymer-1:

(47) ##STR00031##
in anisole for a time period starts at t.sub.0 to t.sub.17h (17 h).

(48) FIG. 16 shows the absorption intensity in an UV-vis absorption spectrum (350 nm to 800 nm wavelength) for the organic charge transport material of polymer-1:

(49) ##STR00032##
in benzonitrile for a time period starts at t.sub.0 to t.sub.17h (17 h). FIG. 16 shows that the loss in absorption of the solution of polymer-1 in anisole after 17 h storage at 23° C. is 3%.

(50) FIG. 16 shows that the loss in absorption of the solution of polymer-1 in benzonitrile after 17 h storage at 23° C. is below the resolution limit of the measurement technique which is 0.8%.

(51) FIGS. 17 and 18 clearly demonstrate that a p-type dopant, such as Molybdenum tris-[1,2-bis(trifluoromethyl) ethane-1,2-dithiolene] (Mo(tfd).sub.3) [compound P20], is not stable in a non-aromatic nitrile solution, such as acetonitrile solution or isovaleronitrile solution, compared with an aromatic nitrile solution—see FIG. 6 and FIG. 11.

(52) FIGS. 15 and 16 clearly demonstrate that an organic charge transport material can be stabilized in an aromatic nitrile solution for storage significant better than in a nitrile-free solvent—see FIG. 10 or in a non-aromatic nitrile solution—see FIGS. 17 and 18.

(53) According to Beer's law of Spectrophotometric Analysis (absorbance=e*L*c, with e=molar absorptivity, L=path length of the sample, c=molar concentration of the compound in solution) the absorption intensity is directly proportional to the concentration of the compound in solution. From that it is concluded that 3% of polymer-1 is decomposed in the anisole solution after 17 hours of storage.

(54) Printing Methods

(55) In the sense of this disclosure the layers of the organic electronic devices are processed from the ink composition. The deposition method may be a printing method like ink jet printing, screen printing, offset printing, flexographic printing, spin coating, slot-die coating, spray coating, Langmuir-Blodgett (LB)method.

(56) It may be a coating method like spin coating, slot-die coating, spray coating, or an imprinting method like nano-imprinting.

(57) These methods are to be understood as examples of layer formation by liquid processing. The methods in the sense of processing the disclosed formulation are not limited thereto.

(58) According to one embodiment the ink composition may be processed by solution-processing, preferably by spin coating, slot die coating and/or inkjet printing.

(59) According to another embodiment the method comprises: forming a layer of an ink composition, preferably by solution-processing, in a pixel cell of an organic electronic device, preferably an organic light-emitting diode pixel bank or solar cell pixel bank, and allowing the auxiliary compound from the ink composition to evaporate, whereby the organic semiconductor layer is formed.

(60) According to another embodiment the organic semiconductor layer obtained from the ink composition is arranged in direct contact with an anode.

(61) The organic layers that can be obtained by using the ink composition according to the invention, for example by means of a solution processing, may have a layer thickness in the range of about ≥1 nm to about ≤1 μm, preferably of about ≥2 nm to about ≤500 nm, and further preferred of about ≥5 nm to about ≤200 nm.

(62) The organic layers manufactured by the ink composition may have a conductivity sigma of about 1E-7 S/cm≤sigma≤1E1 S/cm.

(63) Electronic Device

(64) The organic layers obtained by using the ink composition according to the invention may be used in an electronic device as follows: 1) The organic layer may be used in an organic light emitting diode (OLED) device on the p-side of the device stack (hole transport region), preferably in direct contact with the anode, as hole injection layer (HIL) to enable efficient injection of positive charge carriers (“holes”) of the anode into the adjacent layers of the electronic device. 2) The organic layer may be used in an organic photovoltaic (OPV) device in proximity to—preferably in direct contact with—an electrode as a conductive layer to facilitate efficient extraction of charge carriers from the adjacent layers in the device stack like absorber layer, active layer, hole transport layer into to conductive electrode, which may be the anode or the cathode. 3) The organic layer may be used in organic photovoltaic (OPV) or and organic light emitting diode (OLED) device as “low electrical loss” connecting layer or as part of a “low electrical loss” connecting layer stack between at least two device elements. Such “low electrical loss” connecting layer or “low electrical loss” connecting layer stack may be a p-n-junction or charge generation layer (CGL). The “low electrical loss” connecting layer or “low electrical loss” connecting layer stack may be composed of several layers, preferably of an n-type layer and a p-type layer which may be in direct contact with each other or may be intersected by an interlayer. The organic layer according to the invention is preferably a p-type layer. 4) The organic layer may be used in organic thin film transistors on the transistor electrodes to reduce the contact resistance between the electrode and the layer in direct contact with the electrode.

EXAMPLES

(65) A standard OLED was used to test the inventive ink composition. The layers comprising the inventive OLED devices Inv-OLED-1 to Inv-OLED-4 were deposited sequentially as follows: ITO/Inventive HIL (40 nm)/HTM-1 (90 nm)/Host-1:Emitter-1 (5 wt %, 20 nm)/n-ETM-1 (30 nm)/LiQ (1 nm)/Al (100 nm)

(66) First, the ITO on a glass substrate was cleaned using clean-room wipe and toluene solvent and subsequently plasma-cleaned. Subsequently, inv-ink1 was deposited by spin coating in a nitrogen glove box using the following recipe: spin step 1: acceleration=2 s, speed=750 rpm, t=5 seconds; spin step 2: acceleration=2 s, speed=1200 rpm, t=30 seconds. The layer was dried on a hot plate at 60° C. for 1 min and subsequently a hard bake for cross-linking was applied for 30 mins at 150° C. All subsequent layers were deposited by vacuum thermal evaporation (VTE) at a pressure of about 1E-7 mbar and a deposition rate of about 1 Angstrom per second for the organic layers and about 3 Angstrom per second for the aluminium cathode layer. The materials deposited by VTE were HTM-1=N.sub.4,N.sub.4″-di(naphthalen-1-yl)-N4,N4″-diphenyl-[1,1′:4′,1″-terphenyl]-4,4″-diamine; Host-1=9-(4-(naphthalen-1-yl)phenyl)-10-(phenyl-d5)anthracene; Emitter-1=Compound BD 23 in KR20110015213; n-ETM-1=2-(4-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)-1-phenyl-1H-benzo[d]imidazole:LiQ (1:1 wt %).

(67) In examples Inv-OLED-1 to Inv-OLED-4 it is demonstrated that the inventive ink composition has a significant improved stability.

(68) For examples Inv-OLED-1 to Inv-OLED-4 a liquid ink composition, liquid at 23° C., was obtained by mixing the components: organic charge transport materials of a first organic charge transport material of Polymer-1 (Mn=15458.00 g/mol from GPC/SEC), Mw=23422.00 g/mol from GPC/SEC) and of a second organic charge transport material of Polymer-2 (Mn=17604.00 g/mol from GPC/SEC), Mw=31690.00 g/mol from GPC/SEC); a p-type dopant P17, benzonitrile anisole.

(69) The solvent volume ratio is anisole:benzonitrile=5:1 vol %. The total solid content in the ink was 2 wt.-%, based on the total weight amount of the ink composition. The content of p-type dopant P17 in the solid HIL-layer is 20 wt %, obtained after the benzonitrile and anisole was removed, and calculated on the total weight amount of the solid HIL-layer.

(70) The ratio between Polymer-1 and Polymer-2 is 3.6:10 by weight.

(71) An HIL-layer was prepared with the obtained ink composition according to the invention for example Inv-OLED-1 at t=0 example, for example Inv-OLED-2 at t=2 weeks, for example Inv-OLED-3 at t=12 weeks and for example Inv-OLED-4 at t=22 weeks,

(72) The device performance data of the OLEDs comprising a HIL-layer prepared with the inventive ink according to examples Inv-OLED-1 to Inv-OLED-4 are shown in table 5.

(73) TABLE-US-00005 TABLE 5 Storage time HIL bake OLED voltage OLED Qeff OLED OLED LT97 Ink of inv-ink1 conditions @15 mA/cm.sup.2 @15 mA/cm.sup.2 CIEy @15 mA/cm.sup.2 Inv-OLED-1 t = 0 2 h @ 180° C. 4.5 V 5.9% 0.14 24 h Inv-OLED-2 t = 2 weeks 2 h @ 180° C. 4.4 V 5.7% 0.14 38 h Inv-OLED-3 t = 12 weeks 2 h @ 180° C. 4.3 V 5.4% 0.14 n.a Inv-OLED-4 t = 22 weeks 2 h @ 180° C. 4.3 V 5.7% 0.14 34 h

(74) Excellent storage stability of the ink was demonstrated. The OLED performance does not change for ink storage times of up to 22 weeks.

(75) While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

(76) Therefore, the aforementioned embodiments should be understood to be exemplary but not limiting the present invention in any way.