Patent Description:
With respect to active OLED displays, comprising a plurality of OLED pixels sharing a common hole transport layer, challenging requirements are put on semiconducting materials used in layers arranged between the anode and the emitting layer and shared by the plurality of pixels. On one hand, the materials shall enable individual driving of individual pixels at operational voltages which are as low as possible. On the other hand, so called electrical crosstalk between neighbour pixels should be avoided. The <CIT> teaches that these contradictory requirements can be fulfilled by p-doped layers having electrical conductivity in the range <NUM>×<NUM><NUM> S·m-<NUM> and <NUM>×<NUM>-<NUM> S·m-<NUM>, most favourably between <NUM>×<NUM>-<NUM> S·m-<NUM> and <NUM>×<NUM>-<NUM> S·m-<NUM>. Such low-conductivity p-doped hole transport layers are achievable by use of usual state-of-art redox dopants, like strongly electron accepting radialene compounds, in matrices which are poorly dopable in terms of their deep HOMO level.

Document <CIT> discloses an OLED display having a conventional p-dopant in its hole transport layer, while documents <CIT>, <CIT> and <CIT> disclose metal salts used as p-dopants in OLED devices. Different metal salts are also disclosed in <NPL>, and <CIT>.

<CIT> discloses a display device includes an array substrate having a self-light emitting element. The self-light emitting element includes: a first electrode; a second electrode disposed closer to a side of a sealing substrate than the first electrode; and an organic active layer held between the first electrode and second electrode. The organic active layer contains metal salt or organic salt.

There is, however, continuing demand for p-dopants fulfilling these criteria and improved in other parameters, e.g. from the viewpoint of processability and device stability.

It is an object to provide improved active OLED displays and improved materials enabling this improvement. In one aspect, electrical crosstalk between neighbor pixels of the active OLED display shall be reduced. In another aspect, the improved materials should enable robust display manufacturing, e.g. in terms of improved device stability during any processing step which comprises a treatment of the device or its particular layer at an elevated temperature.

The above problems are solved in accordance with the subject-matter of the independent claims. Preferred embodiments are described in the sub-claims.

The object is achieved through a display device comprising.

alkaline earth metals, Pb, Mn, Fe, Co, Ni, Zn, Cd; rare earth metals in oxidation state (II) or (III); Al, Ga, In; and from Sn, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W in oxidation state (IV) or less.

In one embodiment, the anion and/or the anionic ligand is bound to the metal cation of the p-dopant through an oxygen atom, preferably through two oxygen atoms.

It is to be understood that the term "bound" encompasses structures of the p-dopant, wherein the distance between the metal cation and the oxygen atom/atoms is shorter that the distance between the metal cation and any other atom of the anion and/or of the anionic ligand.

For example, solid-state structure studies of some bis(sulfonyl)imide complexes of divalent and/or trivalent metals revealed that the bis(sulfonyl)imide ligand may be attached to the central metal atom rather by oxygen atoms of the sulfonyl groups than by the imide nitrogen atom which may be in fact arranged more distant from the central metal atom than the oxygen atoms.

In an embodiment, the oxygen atom of the anion and/or of the anionic ligand which is in the metal salt and/or in the metal complex bound to the metal cation has in dichloroethane lower basicity than at least one non-oxygen atoms of the anion and/or of the anionic ligand.

Analogously, in another embodiment, each of the oxygen atoms of the anion and/or of the anionic ligand which are in the metal salt and/or in the metal complex bound to the metal cation has in dichloroethane lower basicity than at least one non-oxygen atom of the anion and/or of the anionic ligand. It is to be understood that the basicity of an atom in the anion and/or in the anionic ligand in an environment, e.g. in <NUM>,<NUM>-dichloroethane, is inversely proportional to the acidity of a corresponding tautomeric form of the electrically neutral conjugated acid formed by addition of one or more protons in the same environment. Measurement of the acidity in <NUM>,<NUM>-dichloroethane as a versatile tool for comparison of various acids is described in <NPL>. It is understood that if the basicity of a particular atom in an anion and/or anionic ligand has to be assessed, the "corresponding tautomeric form" of the electrically neutral conjugated acid is the acid formed by proton addition to the particular atom.

In one embodiment, the anion and/or the anionic ligand consists of at least <NUM>, even more preferably at least <NUM>, most preferably at least <NUM> covalently bound atoms.

In one embodiment, the anion and/or the anionic ligand comprises at least one atom selected from B, C, N.

In one embodiment, the anion and/or the anionic ligand comprises at least two atoms selected from B, C and N which are bound to each other by a covalent bond.

In one embodiment, the anion and/or the anionic ligand comprises at least one peripheral atom selected from H, N, O, F, Cl, Br and I. Under "peripheral atom", it is to be understood an atom which is covalently bound to only one atom of the anion and/or of the anionic ligand. Oppositely, atoms covalently bound to at least two other atoms of the anion and/or of the anionic ligand are assigned as inner atoms.

Under covalent bond, it is to be understood any bonding interaction which involves electron density sharing between the two assessed atoms, wherein the bonding is stronger than van der Waals dispersive interactions; for the sake of simplicity, binding energy <NUM> kJ/mol may be taken as an arbitrary lower limit. In this sense, the term includes also coordination bonds or hydrogen bonds. Anions and/or anionic ligands comprising hydrogen bonds, however, are not particularly preferred.

In one embodiment, the anion and/or the anionic ligand comprises at least one electron withdrawing group selected from halogenated alkyl, halogenated (hetero)aryl, halogenated (hetero)arylalkyl, halogenated alkylsulfonyl, halogenated (hetero)arylsulfonyl, halogenated (hetero)arylalkylsulfonyl, cyano. It is to be understood that for the sake of brevity, halogenated (hetero)aryl means "halogenated aryl or halogenated heteroaryl", halogenated (hetero)arylalkyl means "halogenated heteroarylalkyl or halogenated arylalkyl", halogenated (hetero)arylsulfonyl means "halogenated heteroarylsulfonyl or halogenated arylsulfonyl" and halogenated (hetero)arylalkylsulfonyl means "halogenated heteroarylalkylsulfonyl or halogenated arylalkylsulfonyl".

In one embodiment, the electron withdrawing group is a perhalogenated group. It is to be understood that the term "halogenated" means that at least one hydrogen atom of a group comprising peripheral or inner hydrogen atoms is replaced with an atom selected from F, Cl, Br and I. It is further understood that in a perhalogenated group, all hydrogen atoms comprised in the unsubstituted group are replaced with atoms independently selected from F, Cl, Br and I. Accordingly, under perfluorinated group, it is to be understood a perhalogenated group, wherein all halogen atoms replacing hydrogen atoms are fluorine atoms.

In one embodiment, the metal cation of the p-dopant is selected from Li(I), Na(I), K(I), Rb(I), Cs(I); Mg(II), Ca(II), Sr(II), Ba(II), Sn(II), Pb(II), Mn(II), Fe(II), Co(II), Ni(II), Zn(II), Cd(II), Al(III); rare earth metal in oxidation state (III), V(III), Nb(III), Ta(III), Cr(III), Mo(III), W(III) Ga(III), In(III) and from Ti(IV), Zr(IV), Hf(IV), Sn(IV).

In one embodiment, in the p-dopant molecule, the atom of the anion and/or of the anionic ligand which is closest to the metal cation is a C or a N atom.

In one embodiment, the acidity of the electrically neutral conjugated acid formed from the anion and/or anionic ligand by addition of one or more protons in <NUM>,<NUM>-dichloroethane is higher than that of HCl, preferably higher than that of HBr, more preferably higher than that of HI, even more preferably higher than that of fluorosulfuric acid, and most preferably higher than that of perchloric acid.

In one embodiment, the electrical p-dopant has energy level of its lowest unoccupied molecular orbital computed by standard quantum chemical method and expressed in absolute vacuum scale at least <NUM> eV, preferably at least <NUM> eV, more preferably at least <NUM> eV, even more preferably at least <NUM> eV, most preferably at least <NUM> eV above the energy level of the highest occupied orbital of the covalent hole transport compound computed by the standard quantum chemical method.

The standard quantum chemical method may be the software package TURBOMOLE using DFT functional B3LYP with the basis set def2-TZVP.

In one embodiment, the first hole transport matrix compound is an organic compound, preferably an organic compound comprising a conjugated system of at least <NUM>, more preferably at least <NUM> delocalized electrons; also preferably, the first hole transport matrix compound comprises at least one triaryl amine structural moiety, more preferably, the first hole transport matrix compound comprises at least two triaryl amine structural moieties.

The object is further achieved by method for preparing the display device according to any of the preceding embodiments, the method comprising at least one step wherein the hole transport matrix compound and the electrical p-dopant are in mutual contact exposed to a temperature above <NUM>.

It is to be understood that "in mutual contact" does mean the presence of both components in a condensed phase, or their presence in two condensed phases which share a common phase interface.

The method may further comprise at least one step wherein the p-dopant is evaporated at a reduced pressure, preferably at a pressure below <NUM>×<NUM>-<NUM> Pa and at a temperature above <NUM>, more preferably at a pressure below <NUM>×<NUM>-<NUM> Pa and at a temperature above <NUM>, even more preferably at a pressure below <NUM>×<NUM><NUM> Pa and at a temperature above <NUM>, most preferably at a pressure below <NUM>×<NUM><NUM> Pa and at a temperature above <NUM>.

In one embodiment, the method may comprise the steps, wherein.

In one embodiment, the p-dopant may be used in form of a solid hydrate.

In another embodiment, the p-dopant may be used as an anhydrous solid comprising less than <NUM> wt% water, preferably less than <NUM> wt% water.

The object is further achieved by compound having formula (I)
<CHM>
wherein.

In one embodiment, M is selected from Mg(II), Mn(II) and Zn(II).

In one embodiment, the compound according to formula (I) is provided in a solid form, preferably in a solid form comprising less than <NUM> wt % water, more preferably in a solid form comprising less than <NUM> wt % water, most preferably in a solid crystalline form comprising less than <NUM> wt % water.

In another embodiment, the compound according to formula (I) is provided in form of a solid crystalline hydrate, preferably in form of a solid crystalline hydrate which has water content in the range.

An important property of materials comprised in organic semi-conducting devices is their conductivity. In a display device having a structured anode and at least two pixels sharing at least one hole transport and/or hole injection layer, as described in <CIT>, a limited conductivity of the shared layer may be favourable for achieving a low level of the undesired electrical crosstalk in the display. On the other hand, very low conductivity of the shared layer may increase the operational voltage of the display. <CIT> teaches a conductivity range which represents a trade-off between these contradictory requirements.

The authors of the present application, however, surprisingly found that electrical p-dopants based on certain metal salts and metal complexes enable, under certain conditions, preparing p-doped materials and/or p-doped layers providing stable hole injection from state-of-art anodes into state-of-art hole transport matrices, without substantially increasing the concentration of the free charge carriers above the level which corresponds to conductivities observed in a neat matrix.

This surprising finding offered an opportunity to build the displays of <CIT>, operating at fully comparable voltages, even though the hole transport and/or hole injection layers shared by the multiplicity of pixels have conductivities below the optimum range between <NUM>×<NUM>-<NUM> S. m-<NUM> and <NUM>×<NUM>-<NUM> S. m-<NUM> as disclosed in <CIT>. The dopants of the present application enable efficient operation of display devices of <CIT> at the level of electrical conductivity in p-doped layers shared by the multiplicity of pixels which is near to the detection limit of the available measuring procedure or below it. Thus, the dopants of the present application enable further suppressing the electrical crosstalk in OLED displays and offer new opportunities for designing efficient OLED displays exhibiting very low level of electrical crosstalk. These observations made by the authors will be further described in more detail.

In a previous <CIT> filed by the applicant, now <CIT>, some of the authors described successful use of some metal imides like
<CHM>
or
<CHM>
as hole injection materials in organic electronic devices.

Parallel with further investigation of analogous metal imide compounds, the authors surprisingly found that also some structurally quite different compounds, namely metal borate complexes like
<CHM>
are utilizable in an analogous way.

Some of the authors disclosed in a further application, namely in <CIT>, a compound E3 prepared by sublimation of a zinc sulfonamide complex, having composition C<NUM>F<NUM>N<NUM>O<NUM>S<NUM>Zn<NUM> and crystallizing in a monoclinic crystal lattice belonging to the space group P <NUM><NUM> with unit cell dimensions a = <NUM> (<NUM>) Å, α = <NUM>°; b = <NUM> (<NUM>) Å, β = <NUM> (<NUM>); c = <NUM> (<NUM>) Å;γ = <NUM>° and unit cell volume <NUM> (<NUM>) Å<NUM>. This compound has a structure shown in <FIG>, comprising a central oxygen dianion surrounded with a first coordination sphere which consists of four tetrahedrally arranged zinc dications, and a second coordination sphere consisting of six sulfonylamide ligands bridging with triatomic -N-S-O-bridges all six edges of the Zn<NUM> cluster.

Most surprisingly, the authors found that all these structurally different compounds analogously exhibit two different modes in their p-doping activity, depending on the process conditions during preparation of the doped material and/or layer.

In the first mode, semiconducting materials and/or layers doped with these compounds (which can be generalized as metal salts and/or electrically neutral metal complexes with an anionic ligand) exhibit well-measurable electrical conductivities which are only slightly lower in comparison with materials and/or layers doped with typical redox p-dopants. It appears that this mode occurs if the doped material and/or layer is exposed to oxygen, even though only in trace amounts.

In the second mode, the semiconducting materials and/or layers doped with the disclosed metal salts and/or electrically neutral metal complexes comprising an anionic ligand exhibit hardly measurable electrical conductivities. This mode occurs if the oxygen access to the doped material and/or layer is strictly avoided throughout processing thereof. The authors found that despite the extremely low conductivity of materials and/or layers doped in the second mode, devices comprising such materials and/or layers particularly as hole transporting or hole injecting layers still exhibit electrical behavior corresponding to an excellent hole injection.

The existence of the two above described modes of p-doping activity provides the disclosed p-dopants with a unique versatility in their use in organic electronic devices, and particularly in displays comprising an anode structured into a multiplicity of pixels sharing a common hole transport layer. The conductivity of the common p-doped layer can be either set in the limits taught in <CIT> by exploiting the first doping mode, or set below these limits, exploiting the second doping mode.

Furthermore, recent investigations made by the authors provided hints that the materials and/or layers doped with the presented metal salts and/or metal complexes may exhibit favourable thermal stability, particularly in materials provided according to the above described second mode of the p-doping action. These properties may be again particularly suitable for the use of the disclosed p-dopants in AMOLED displays, because the necessity of structuring such displays into separate pixels often requires a thermal treatment of p-doped layers or using another treatment which may result in an unavoidable heating of a previously deposited p-doped layer.

In a specific embodiment of the invention, the authors provided new amide compounds comprising bulkier fluorinated side chains in comparison with the compounds tested in <CIT>. This change resulted in favourable storage properties of the new compounds, which are substantially non-hygroscopic and remain solid even at high air humidity, whereas LiTFSI and analogous TFSI salts have tendency to deliquesce.

The electrical conductivity of a thin layer sample can be measured by, for example, the so called two-point method. At this, a voltage is applied to the thin layer and the current flowing through the layer is measured. The resistance, respectively the electrical conductivity, results by considering the geometry of the contacts and the thickness of the layer of the sample. The experimental setup for conductivity measurement used by the authors of the present application enables deposition of p-doped layers as well as conductivity measurement under controlled conditions, especially with regard to contact of deposited layers with an atmosphere comprising oxygen. In this regard, the whole deposition-measurement sequence may be carried out either in a glove-box or in a chamber comprising a controlled atmosphere, using solution processing techniques, or completely in a vacuum chamber, using vacuum thermal evaporation (VTE) as the method of choice, especially suitable for materials and/or layers doped in the second mode.

The electrical conductivity of the first hole transport layer may be lower than <NUM>×<NUM>-<NUM> S·m-<NUM>, preferably lower than <NUM>×<NUM>-<NUM> S·m-<NUM>, more preferably lower than <NUM>×<NUM>-<NUM> S·m-<NUM>. Alternatively, provided that the detection limit of the used conductivity measurement method is lower than <NUM>×<NUM>-<NUM> S·m-<NUM>, it is preferred that the conductivity of the first hole transport layer is lower than the detection limit.

The first hole transport layer (HTL) is formed for the plurality of OLED pixels in the OLED display. In the claimed invention, the first HTL extends over all pixels of the plurality of pixels in the OLED display. Similarly, the cathode may be formed as a common cathode for the plurality of pixels. The common cathode may extend over all pixels of the plurality of pixels in the OLED display. Every individual pixel may have its own anode that may not touch anodes of other individual pixels.

Optionally, for one or more of the plurality of OLED pixels, following organic layers may be provided: a hole blocking layer, an electron injection layer, and/or an electron blocking layer.

Further, the active OLED display has driving circuit configured to separately drive the individual pixels of the plurality of pixels provided in the OLED display. In one embodiment, a step of separately driving may comprise separate control of the driving current applied the individual pixels.

The first HTL is made of a hole transport matrix (HTM) material electrically doped with the p-dopant. The hole transport matrix material may be electrically doped with more than one p-dopant. It is to be understood that the HTM material may consist of one or more HTM compounds, whereas the term hole transport material is a broader term used throughout this application for all semiconducting materials comprising at least one hole transport matrix compound. The hole transport matrix material is not particularly limited. Generally, it is any material consisting of covalently bound atoms which allows embedding the p-dopant. In this sense, infinite inorganic crystals having predominantly covalent bonds like silicon or germanium, or extremely crosslinked inorganic glasses like silicate glass, do not fall in the scope of the definition of the hole transport matrix material. Preferably, the hole transport matrix material may consist of one or more organic compounds.

The first hole transport layer may have a thickness of less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>.

The first hole transport layer may have a thickness of more than <NUM>, more than <NUM>, more than <NUM>, or more than <NUM>.

In one embodiment of the the first hole transport layer, the p-dopant may be distributed homogeneously and isotropically. In another embodiment, the p-dopant may be homogeneously mixed with the matrix but the concentration of the p-dopant may exhibit a gradient across the layer. In one embodiment, the first hole transport layer may comprise a sub-layer, wherein the amount of the p-dopant may, by weight and/or by volume, exceed the total amount of other components which may additionally be comprised in the layer.

In one embodiment, the weight concentration of the p-dopant, based on the overall weight of the sub-layer, may exceed <NUM> %; alternatively, the p-dopant may form at least <NUM> wt%, alternatively at least <NUM> wt%, alternatively at least <NUM> wt%, alternatively at least <NUM> wt%, alternatively at least <NUM> wt%, alternatively at least <NUM> wt%, alternatively at least <NUM> wt%, with respect to the total weight of the layer. For the sake of simplicity, any sub-layer of the first transport layer prepared by depositing only the p-dopant may be assigned as a neat (hole injection) p-dopant sub-layer.

The same may apply for any other layer in the display device which may comprise an analogous combination of a hole transport matrix in contact with a metal salt or a metal complex as the first hole transport layer.

For example, pixels comprised in the display device may comprise a hole generation layer, which may, in one embodiment, consist of a hole transport matrix homogeneously doped with the p-dopant. In another embodiment, the hole generation layer may comprise a sub-layer, wherein the amount of the p-dopant exceeds, by weight and/or by volume, the total amount of other components.

The anode may be made of a transparent conductive oxide (TCO), like indium tin oxide (ITO) or aluminium zinc oxide (AZO). Alternatively, the anode may be made of one or more thin metallic layers leading to a semitransparent anode. In another embodiment, the anode may be made of a thick metallic layer which is not transparent to visible light.

The OLED pixel(s) may comprise an electron blocking layer (EBL) provided between the first hole transport layer and the light emitting layer. The EBL may be in direct contact with the first HTL and the EML. The electron blocking layer may be an electrically undoped layer (in other words, it may be free of an electrical dopant) made of an organic hole transport matrix material. The composition of the organic hole transport matrix material of the first hole transport layer may be the same as the composition of the organic hole transport matrix material of the electron blocking layer. In another embodiment of the invention, the composition of both hole transport matrix materials may be different.

The EBL may have a layer thickness of more than <NUM>, more than <NUM>, more than <NUM>, more than <NUM>, or more than <NUM>.

The thickness of the EBL may be less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>. Compared to the EBL, the common HTL may be thinner by about one order of magnitude.

Each compound forming the electron blocking layer may have a highest occupied molecular orbital (HOMO) energy level, expressed in the absolute scale referring to vacuum energy level being zero, higher than a HOMO level of any compound forming the hole transport matrix material of the common hole transport layer.

The organic matrix material of the electron blocking layer may have a hole mobility which is equal to or higher than the hole mobility of the matrix material of the hole transport layer.

The hole transport matrix (HTM) material of the common HTL and/or of the EBL may be selected from compounds comprising a conjugated system of delocalized electrons, the conjugated system comprising lone electron pairs of at least two tertiary amine nitrogen atoms.

Suitable compounds for the hole transport matrix material of the doped hole transport layer and / or the common hole transport layer may be selected from the known hole transport matrices (HTMs), e.g. from triaryl amine compounds. HTMs for the doped hole transport material may be compounds comprising a conjugated system of delocalized electrons, wherein the conjugated system comprises lone electron pairs of at least two tertiary amine nitrogen atoms. Examples are N4,N4'-di(naphthalen-<NUM>-yl)-N4,N4'-diphenyl-[<NUM>,<NUM>'-biphenyl]-<NUM>,<NUM>'-diamine (HT1), and N4,N4, N4'',N4"-tetra([<NUM>,<NUM>'-biphenyl]-<NUM>-yl)-[<NUM>,<NUM>':<NUM>',<NUM>"-terphenyl]-<NUM>,<NUM>''-diamine (HT4). The synthesis of terphenyldiamine HTMs is described e.g. in <CIT>, <CIT> or <CIT>; <NUM>,<NUM>-phenylenediamine matrices are described e.g. in <CIT>. Many triaryl amine HTMs are commercially available.

The light emitting layer of the OLED display may comprise a plurality of sub-regions, each of the sub-regions being assigned to one of the pixels from the plurality of pixels. The light emitting layer of an individual pixel, corresponding to a sub-region of the emitting layer of the display, preferably does not touch light emitting layers of neighbor pixels. In the display manufacturing process, the organic layer comprising EMLs of individual pixels may be patterned by known methods, for example, by fine-metal masking (FMM), laser induced thermal imaging (LITI), and / or ink-jet printing (IJP) in either top emission, bottom emission or bottom emission micro cavity (see, for example, <NPL>; <NPL>). A RGB layout may be provided.

For the plurality of OLED pixels, a common electron transport layer may be formed by the electron transport layers provided in the stack of organic layers of the plurality of OLED pixels.

The common electron transport layer may comprise an organic electron transport matrix (ETM) material. Further, the common electron transport layer may comprise one or more n-dopants-. Suitable compounds for the ETM contain aromatic or heteroaromatic structural moieties, as disclosed e.g. in documents <CIT> or <CIT>.

The cathode can be made of a metal or a metal alloy with a low work function. Transparent cathodes made of a TCO are also well-known in the art.

The stack of organic layers may be made of organic compounds having a molecular weight of less than <NUM>/mol. In an alternative embodiment, the organic compounds may have a molecular weight of less than <NUM>/mol.

In the following, further embodiments will be described in further detail, by way of example, with reference to figures. In the figures show:.

<FIG> shows a schematic representation of an active OLED display <NUM> having a plurality of OLED pixels <NUM>, <NUM>, <NUM> provided in an OLED display <NUM>.

In the OLED display <NUM>, each pixel <NUM>, <NUM>, <NUM> is provided with an anode 2a, 3a, 4a being connected to a driving circuit (not shown). Various equipment able to serve as a driving circuit for an active matrix display is known in the art. In one embodiment, the anodes 2a, 3a, 4a are made of a TCO, for example of ITO.

A cathode <NUM> is provided on top of an organic stack comprising an electrically doped hole transport layer (HTL) <NUM>, an electron blocking layer (EBL) <NUM>, a light emitting layer (EML) having sub-regions 2b, 3b, 4b assigned to the pixels <NUM>, <NUM>, <NUM> and being provided separately in an electron transport layer (ETL) <NUM>. For example, the sub-regions 2b, 3b, 4b can provide an RGB combination for a color display (R - red, G - green, B - blue). In another embodiment, pixels for individual colours may comprise analogous white OLEDs provided with appropriate combination of colour filters. By applying individual drive currents to the pixels <NUM>, <NUM>, <NUM> via the anodes 2a, 3a, 4a and the cathode <NUM>, the display pixels <NUM>, <NUM>, <NUM> are operated independently.

<FIG> is a schematic sectional view of an organic light-emitting diode (OLED) <NUM>, which may represent an OLED pixel in a display device according to an exemplary embodiment of the present invention. The OLED <NUM> includes a substrate <NUM>, an anode <NUM>, a hole injection layer (HIL) <NUM>, a hole transport layer (HTL) <NUM>, an emission layer (EML) <NUM>, an electron transport layer (ETL) <NUM>. The electron transport layer (ETL) <NUM> is formed directly on the EML <NUM>. Onto the electron transport layer (ETL) <NUM>, an electron injection layer (EIL) <NUM> is disposed. The cathode <NUM> is disposed directly onto the electron injection layer (EIL) <NUM>.

Instead of a single electron transport layer <NUM>, optionally an electron transport layer stack (ETL) can be used.

<FIG> is a schematic sectional view of an OLED <NUM>, which may represent an OLED pixel in a display device according to another exemplary embodiment of the present invention. <FIG> differs from <FIG> in that the OLED <NUM> of <FIG> comprises an electron blocking layer (EBL) <NUM> and a hole blocking layer (HBL) <NUM>.

Referring to <FIG>, the OLED <NUM> includes a substrate <NUM>, an anode <NUM>, a hole injection layer (HIL) <NUM>, a hole transport layer (HTL) <NUM>, an electron blocking layer (EBL) <NUM>, an emission layer (EML) <NUM>, a hole blocking layer (HBL) <NUM>, an electron transport layer (ETL) <NUM>, an electron injection layer (EIL) <NUM> and a cathode electrode <NUM>.

<FIG> is a schematic sectional view of a tandem OLED <NUM>, which may represent an OLED pixel in a display device according to another exemplary embodiment of the present invention. <FIG> differs from <FIG> in that the OLED <NUM> of <FIG> further comprises a charge generation layer and a second emission layer.

Referring to <FIG>, the OLED <NUM> includes a substrate <NUM>, an anode <NUM>, a first hole injection layer (HIL) <NUM>, a first hole transport layer (HTL) <NUM>, a first electron blocking layer (EBL) <NUM>, a first emission layer (EML) <NUM>, a first hole blocking layer (HBL) <NUM>, a first electron transport layer (ETL) <NUM>, an n-type charge generation layer (n-type CGL) <NUM>, a hole generating layer (p-type charge generation layer; p-type GCL) <NUM>, a second hole transport layer (HTL) <NUM>, a second electron blocking layer (EBL) <NUM>, a second emission layer (EML) <NUM>, a second hole blocking layer (EBL) <NUM>, a second electron transport layer (ETL) <NUM>, a second electron injection layer (EIL) <NUM> and a cathode <NUM>.

While not shown in <FIG> and <FIG>, a sealing layer may further be formed on the cathode electrodes <NUM>, in order to seal the OLEDs <NUM> and <NUM>. In addition, various other modifications may be applied thereto.

<NUM> (<NUM> mmol) N-(bis(perfluorophenyl)phosphoryl)-P,P-bis(perfluorophenyl)phosphinic amide is dissolved in <NUM> dry toluene and cooled to <NUM>. <NUM> (<NUM> mmol, <NUM> eq) lithium hydride are added. The mixture is heated to reflux for <NUM>. After cooling to room temperature, the product is precipitated with <NUM> n-hexane, filtered off, washed with n-hexane (<NUM>× <NUM>). <NUM> (<NUM> %) product is obtained as a white solid after drying in high vacuum.

<NUM> (<NUM> mmol) N-(bis(perfluorophenyl)phosphoryl)-P,P-bis(perfluorophenyl)phosphinic amide are dissolved in <NUM> dry toluene and cooled to o°C. <NUM> (<NUM> mmol, <NUM> eq) <NUM> diethylzinc solution in hexane are added. The mixture is heated to reflux for <NUM>. After cooling to room temperature, the product is precipitated with <NUM> n-hexane, filtered off, washed with n-hexane (<NUM>×<NUM>). <NUM> (<NUM> %) product is obtained as a white solid after drying in high vacuum.

<NUM> (<NUM> mmol) perfluorohexyl sulfonyl amide is dissolved in a dried Schlenk flask in <NUM> dry THF. <NUM> (<NUM> mmol, <NUM> eq) lithium hydride is added under Ar counter-flow to the ice-cooled solution. <NUM> (<NUM> mmol, <NUM> eq) perfluorohexylsulfonylfluoride is added dropwise to the resulting slurry. The mixture is heated to <NUM> for ca <NUM>. The mixture is cooled to room temperature, filtered and the solvent is removed under reduced pressure. The residue is treated with <NUM> toluene and concentrated again. The crude product is slurrywashed with <NUM> hexane, the solid is filtered-off and dried in vacuum. The <NUM> (<NUM> %) product is obtained as a pale yellow powder.

<NUM> (<NUM> mmol) bis((perfluorohexyl)sulfonyl)amide is dissolved in <NUM> diethyl ether and <NUM> <NUM>% aqueous sulfuric acid is cautiously added under ice cooling. The mixture is stirred vigorously for <NUM>. The organic phase is separated, dried over magnesium sulfate, <NUM> toluene is added to avoid foaming and the solvent is evaporated under reduced pressure. The residue is purified using a bulb-to-bulb-distillation apparatus at a temperature about <NUM> and a pressure about <NUM> Pa. <NUM> (<NUM> %) product is obtained as a yellowish, waxy solid.

<NUM> (<NUM> mmol) bis((perfluorohexyl)sulfonyl)amine is dissolved in <NUM> dry methyl-tert-butylether (MTBE). <NUM> (<NUM> mmol, <NUM> eq) LiH are added under Ar counter-flow. The reaction mixture is stirred overnight and the solvent subsequently removed under reduced pressure. The pale pink solid residue is dried at <NUM> in vacuum. <NUM> (<NUM>%) product are obtained as an off-white solid.

Mass spectroscopy with electrospray ionization (MS-ESI) confirmed the expected synthesis outcome by the dominant presence of m/z <NUM> (anion C<NUM>F<NUM>NO<NUM>S<NUM>) in the intermediate bis((perfluorohexyl)sulfonyl)amine as well as in the Li salt.

<NUM> (<NUM> mmol) bis((perfluorohexyl)sulfonyl)amine is dissolved in <NUM> dry MTBE. <NUM> (<NUM> mmol, <NUM> eq) diethyl zinc solution in hexane are added dropwise. The reaction mixture is stirred overnight and the solvent removed under reduced pressure. <NUM> (<NUM> %) pale pink solid are obtained after drying at <NUM> in vacuum.

Analogously, zinc bis (perfluoropropyl)sulfonylamide (<NPL>, ZnHFSI) has been prepared.

<NUM> (<NUM> mmol ) bis((perfluoropropan-<NUM>-yl)sulfonyl)amine is dissolved in <NUM> dry MTBE, <NUM> (<NUM> mmol, <NUM> eq) diethyl zinc solution in hexane are added dropwise and the mixture is stirred overnight at room temperature. <NUM> hexane are added and the resulting solid precipitate is filtered off and dried in high vacuum. <NUM> (<NUM> %) product are obtained as a white powder.

<NUM> (<NUM> mmol ) bis((perfluoropropan-<NUM>-yl)sulfonyl)amine are dissolved in <NUM> dry MTBE, <NUM> (<NUM> mmol, <NUM> eq) dibutyl magnesium solution in heptane are added dropwise and the mixture is stirred overnight at room temperature. The solvent is removed under reduced pressure and the residue is dried in high vacuum. <NUM> (<NUM> %) product are obtained as a white powder.

<NUM> (<NUM> mmol) perfluoroacetophenone are dissolved in <NUM> toluene. The solution is cooled with an ice bath and <NUM> (<NUM>, <NUM> mmol, <NUM> eq) hydrazine-monohydrate is added dropwise. The mixture is heated to reflux for <NUM> days. After cooling to room temperature, the mixture is washed two times with <NUM> saturated aqueous sodium hydrogen carbonate solution and two times with <NUM> water, dried over magnesium sulfate and the solvent is removed under reduced pressure. The yellow, oily residue is distilled from bulb to bulb at a temperature about <NUM> and pressure about <NUM> Pa. The crude product is dissolved in hot hexane and the solution stored at -<NUM>. The precipitated solid is filtered off and the slurry washed two times in <NUM> hexane. <NUM> (<NUM> %) product are obtained as a slightly yellow solid.

GCMS: confirms the expected M/z (mass/charge) ratio <NUM>.

<NUM> (<NUM> mmol) <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoro-<NUM>-(trifluoromethyl)-<NUM>-indazole is added under Ar counter-flow to an out-baked Schlenk flask and treated with <NUM> toluene. Freshly pulverized lithium borohydride is added to the starting material. The mixture is heated to <NUM>, until hydrogen formation ceases (ca. After slight cooling, <NUM> hexane are added, the mixture is heated to reflux for <NUM> and cooled to room temperature. The precipitated solid is filtered off, washed with <NUM> hot hexane and dried in high vacuum. <NUM> (<NUM> %) product are obtained as an off-white solid.

<NUM> ( <NUM> mmol, <NUM> eq) <NUM>,<NUM>-bis(trifluoromethyl)pyrazole in a baked-out Schlenk flask is dissolved in <NUM> dry toluene. <NUM> (<NUM> mmol, <NUM> eq) freshly pulverized lithium borohydride is added under Ar counter-flow and the mixture is heated to reflux for <NUM> days. The solvent and the excessive starting material are removed by distillation under reduced pressure and the residue is crystallized from n-chlorohexane. <NUM> (<NUM> %) product is obtained as a white solid.

<NUM> (<NUM> mmol) perfluorobenzophenone are dissolved in <NUM> toluene. <NUM> (<NUM>, <NUM> mmol, ca. <NUM> eq) hydrazine-monohydrate is added dropwise to the ice-cooled solution. <NUM> sodium sulfate are added and the mixture is heated to reflux for <NUM> days. After cooling, <NUM> acetone are added to the reaction mixture and the resulting slurry is stirred for <NUM> at room temperature. The solid is filtered off, thoroughly washed with <NUM>×<NUM> toluene, organic fractions are combined and washed two times with saturated aqueous sodium hydrogen carbonate. The solvent is removed under reduced pressure and the residue purified by column chromatography. <NUM> (<NUM> %) product are obtained as a pale yellow solid. GC-MS: confirms the expected M/z (mass/charge) ratio <NUM>.

<NUM> (<NUM> mmol, <NUM> eq) <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoro-<NUM>-(perfluorophenyl)-<NUM>-indazole are dissolved in <NUM> chlorobenzene in a baked-out Schlenk flask. Freshly pulverized lithium borohydride (<NUM>, <NUM> mmol, <NUM> eq) is added under Ar counter-flow. The mixture is heated to <NUM> for <NUM> days and cooled to room temperature. The solvent is removed under reduced pressure and the residue dried in high vacuum. The crude is further purified by drying in a bulb to bulb apparatus at a temperature about <NUM> and a pressure about12 Pa. <NUM> (<NUM> %) product are obtained as an off-white solid.

Freshly pulverized lithium borohydride (<NUM>, <NUM> mmol, <NUM> eq) is placed in a baked-out pressure tube, <NUM> (<NUM> mmol, <NUM> eq) <NUM>,<NUM>-difluoro-<NUM>-indazole-<NUM>-carbonitrile are added under Ar counter-flow and washed down with <NUM> toluene. The pressure tube is closed and heated to a temperature about <NUM> for ca <NUM>. After cooling to room temperature, the mixture is treated with <NUM> hexane in an ultra-sonic bath for ca <NUM>. The precipitated solid is filtered off and washed with hexane (<NUM> in total). After drying, <NUM> yellowish solid are obtained.

<NUM> (<NUM> mmol) lithium tris(<NUM>,<NUM>-bis(trifluoromethyl)-<NUM>-pyrazol-<NUM>-yl)hydroborate are dissolved in <NUM> N,N-dimethyl formamide. An aqueous solution of <NUM> zinc dichloride in <NUM> water is added dropwise. <NUM> water are further added and the mixture is treated in an ultra-sonic bath for <NUM>. The precipitate is filtered off and dried in high vacuum. <NUM> (<NUM> %) product are obtained as a white solid.

A precursor compound E2 has been prepared according to Scheme <NUM>
<CHM>.

A <NUM> Schlenk flask is heated in vacuum and, after cooling, purged with nitrogen. Perfluoroaniline is dissolved in <NUM> toluene and the solution cooled to -<NUM>. A <NUM> t-butyl lithium solution in hexane is added dropwise via syringe over <NUM>. The reaction solution changes from clear to cloudy and is stirred for <NUM> at -<NUM>. After that, the solution is allowed to warm to -<NUM> and <NUM> eq of trifluoromethanesulfonic anhydride is added dropwise to the solution. Then, the cooling bath is removed and the reaction mixture is allowed to warm slowly to ambient temperature and stirred overnight, whereby the color changes to light orange. Additionally, a white solid forms. The precipitated by-product lithium trifluoromethane sulfonate is filtered off by suction filtration over a sintered glass filter and washed with <NUM> × <NUM> toluene and <NUM> n-hexane. The orange filtrate is evaporated and dried in high vacuum, forming crystals. The crude product is then purified by bulb-to-bulb distillation (<NUM> @ <NUM>×<NUM>-<NUM> mbar), resulting in a crystalline colorless solid (main fraction).

A <NUM> Schlenk flask is heated in vacuum and, after cooling, purged with nitrogen. <NUM>,<NUM>,<NUM>-trifluoro-N-(perfluorophenyl) methane sulfonamide is dissolved in <NUM> toluene and <NUM> eq of diethyl zinc in hexane is added dropwise to the solution via syringe at ambient temperature. During the addition, a fog forms in the flask and the reaction solution becomes jelly and cloudy. The solution is stirred for further <NUM> at this temperature. After that, <NUM> n-hexane are added and a white precipitate forms, which is subsequently filtered over a sintered glass filter (pore <NUM>) under inert atmosphere. The filter cake is twice washed with <NUM> n-hexane and dried in high vacuum at <NUM> for <NUM>.

<NUM> E2 is sublimed at the temperature <NUM> and pressure <NUM>-<NUM> Pa.

The sublimed material forms colorless crystals. One crystal of an appropriate shape and size (<NUM> x <NUM> x <NUM><NUM>) has been closed under Ar atmosphere in a glass capillary and analyzed on Kappa Apex II diffractometer (Bruker-AXS, Karlsruhe, Germany) with monochromatic X-ray radiation from a source provided with molybdenum cathode (λ = <NUM> pm). Overall <NUM> reflexions were collected within the theta range <NUM> to <NUM>°. The structure was resolved by direct method (SHELXS-<NUM>, Sheldrick, <NUM>) and refined with a full-matrix least-squares method (SHELXL-<NUM>/<NUM>, Olex2 (Dolomanov, <NUM>).

ABH-<NUM> is an emitter host and NUBD-<NUM> and DB-<NUM> are blue fluorescent emitter dopants, all commercially available from SFC, Korea.

Before use in vacuum deposition processes, the auxiliary materials as well as the tested compounds, including commercially available sulfonyl imide salts, like MgTFSI (Alfa Aesar, <NPL>), MnTFSI (Alfa Aesar, <NPL>), ScTFSI (Alfa Aesar,<NPL>), Fe(III)(TFSI) (Alfa Aesar, <NPL>), LiNFSI (American Custom Chemicals Corporation, <NPL>), were purified by preparative vacuum sublimation.

Example <NUM> (bottom emitting white OLED pixel, comprising a metal complex or metal salt as a p-dopant concentrated in a neat hole generating sub-layer) (not forming part of the claimed invention).

On a glass substrate provided with an ITO anode having thickness <NUM>, there were subsequently deposited <NUM> hole injection layer made of F1 doped with <NUM> wt% PD-<NUM>; <NUM> thick undoped hole transport layer made of neat F1; <NUM> thick first emitting layer formed of ABH113 doped with <NUM> wt% BD200 (both supplied by SFC, Korea); <NUM> thick first electron transport layer made of neat F2; <NUM> thick electron-generating part of the charge-generating layer (n-CGL) made of F3 doped with <NUM> wt% Yb; <NUM> thick interlayer made of F4; <NUM> thick hole-generating part of the charge-generating layer (p-CGL) made of PB-<NUM>; <NUM> thick second hole transport layer made of neat F1; <NUM> second emitting layer of the same thickness and composition as the first emitting layer; <NUM> thick first electron transport layer made of neat F2; <NUM> thick electron injection layer (EIL) made of F3 doped with <NUM> wt% Yb; <NUM> Al cathode.

All layers were deposited by vacuum thermal evaporation (VTE).

At the current density <NUM> mA/cm<NUM>, the operational voltage of the device <NUM> V was well comparable with the same device comprising a commercial state-of-art p-dopant instead of PB-<NUM>. Exact calibration of measuring equipment necessary for luminance/efficiency comparison was not made in this experiment.

Example <NUM> (bottom emitting blue OLED pixel comprising a metal complex or metal salt as a p-dopant concentrated in a neat hole injecting sub-layer) (not forming part of the claimed invention).

On the same glass substrate provided with an ITO anode as in the Example <NUM>, following layers were subsequently deposited by VTE: <NUM> hole injection layer made of the compound PB-<NUM>; <NUM> thick HTL made of neat F1; <NUM> EML made of ABH113 doped with <NUM> wt% NUBD370 (both supplied by SFC, Korea), <NUM> EIL/ETL made of F2 doped with <NUM> wt% LiQ; <NUM> Al cathode.

Comparative device comprised the HIL made of the compound CN-HAT (<NPL>) instead of PB-<NUM>.

The device achieved current density <NUM> mA/cm<NUM> and external quantum efficiency (EQE) <NUM> % at an operational voltage <NUM> V, whereas the comparative device exhibited the same current density at a significantly higher voltage <NUM> V and with a significantly lower EQE <NUM> %.

Example <NUM> (bottom emitting blue OLED pixel comprising a hole injection sub-layer consisting of a hole transport matrix homogeneously doped with a metal complex or metal salt) On the same glass substrate provided with an ITO anode as in the Example <NUM>, following layers were subsequently deposited by VTE: <NUM> hole injection layer made of the matrix compound F2 doped with <NUM> weight % PB-<NUM>; <NUM> thick HTL made of neat F1; <NUM> EML made of ABH113 doped with <NUM> wt% NUBD370 (both supplied by SFC, Korea), <NUM> EIL/ETL made of F2 doped with <NUM> wt% LiQ; <NUM> Al cathode.

The inventive device achieved current density <NUM> mA/cm<NUM> and EQE <NUM> % at a voltage <NUM> V, LT97 (operational time necessary for luminance decrease to <NUM> % of its initial value at the current density <NUM> mA/cm<NUM>) was <NUM> hours.

Example <NUM> (white display pixel comprising a hole generating sub-layer consisting of a hole transport matrix homogeneously doped with a metal complex or a metal salt).

In the device prepared analogously as in Example <NUM>, the neat PB-<NUM> layer was replaced with a layer of the same thickness, consisting of F2 doped with <NUM> weight % PB-<NUM>.

Example <NUM> (blue display pixel comprising a metal complex or a metal salt as a p-dopant concentrated in a neat hole injection sub-layer).

Table 2a schematically describes the model device.

The results for two exemplary p-dopants are given in Table 2b.

Example <NUM> (blue display pixel comprising a hole injection sub-layer consisting of a hole transport matrix homogeneously doped with a metal complex or a metal salt).

Table 3a schematically describes the model device.

Example <NUM> (blue display pixel comprising a metal complex or a metal salt as a p-dopant concentrated in a neat hole generation sub-layer).

Table 4a schematically describes the model device.

The results for two exemplary p-dopants are given in Table 4b.

Example <NUM> (blue display pixel comprising a hole generation sub-layer consisting of a hole transport matrix homogeneously doped with a metal complex or a metal salt).

Table 5a schematically describes the model device.

The results for two exemplary p-dopants are given in Table 5b.

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

Claim 1:
Display device (<NUM>) comprising
- a plurality of OLED pixels (<NUM>, <NUM>, <NUM>) comprising at least two OLED pixels, the OLED pixels comprising an anode (2a, 3a, 4a), a cathode (<NUM>), and a stack of organic layers, wherein the stack of organic layers
- is arranged between and in contact with the cathode (<NUM>) and the anode (2a, 3a, 4a), and
- comprises a first electron transport layer (<NUM>), a first hole transport layer (<NUM>), and a first light emitting layer (2b, 3b, 4b) provided between the first hole transport layer (<NUM>) and the first electron transport layer (<NUM>), and
- a driving circuit configured to separately driving the pixels of the plurality of OLED pixels (<NUM>, <NUM>, <NUM>),
wherein, for the plurality of OLED pixels (<NUM>, <NUM>, <NUM>), the first hole transport layer (<NUM>) is provided in the stack of organic layers as a common hole transport layer (<NUM>) shared by the plurality of OLED pixels (<NUM>, <NUM>, <NUM>), and the first hole transport layer (<NUM>) comprises
(i) at least one first hole transport matrix compound consisting of covalently bound atoms and
(ii) at least one electrical p-dopant characterized in that the electrical p-dopant is selected from metal salts and from electrically neutral metal complexes comprising a metal cation and at least one anion and/or at least one anionic ligand, wherein the anion and/or the anionic ligand consists of at least <NUM> covalently bound atoms,
wherein the metal cation of the electrical p-dopant is selected from alkali metals; alkaline earth metals, Pb, Mn, Fe, Co, Ni, Zn, Cd; rare earth metals in oxidation state (II) or (III); Al, Ga, In; and from Sn, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W in oxidation state (IV) or less.