Organic light-emitting diode

Abstract

Organic light-emitting diode (1000) comprising an organic layer sequence (100) with: - a first organic emitter layer (1) for generating electromagnetic radiation of a first wavelength range (10), - a second organic emitter layer (2) for generating electromagnetic radiation of a second wavelength range (20), - a charge carrier generation layer sequence (33) arranged between the first (1) and the second (2) emitter layer, via which the first emitter layer (1) and the second emitter layer (2) are electrically connected in series, wherein - the charge carrier generation layer sequence (33) comprises a converter material which converts radiation of the first (10) and / or the second (20) wavelength range at least partially into radiation of a third wavelength range (30), so that the organic light-emitting diode (1000) emits mixed light with components of the first (10), second (20) and third (30) wavelength range, wherein the charge carrier generation layer sequence (33) comprises at least one n-type organic layer (6), at least one p-type organic layer (7) and a conversion layer (3), wherein the converter material is incorporated into the conversion layer (3), wherein the conversion layer (3) is arranged between the n-type layer (6) and the p-type layer (7) and separates the n-type layer (6) and the p-type layer (7) from each other.

Description

[0001] An organic light-emitting diode is specified.

[0002] One task to be solved is to specify an organic light-emitting diode, or OLED for short, which is particularly simple in structure and which generates and emits light with different color components particularly efficiently.

[0003] An organic light-emitting diode device is known from European patent EP 2 330 654 A1. European patent US 7 812 359 B2 describes an organic electroluminescent device. European patent WO 2013 / 104572 A1 describes an optoelectronic device, a method for manufacturing an optoelectronic device, a device for partitioning a room, and a piece of furniture.

[0004] This problem is solved by an OLED with the features of the independent patent claim. Advantageous embodiments and further developments are the subject of the dependent patent claims.

[0005] According to at least one embodiment, the OLED comprises an organic layer sequence. The organic layer sequence includes a first organic emitter layer for generating electromagnetic radiation of a first wavelength range. Furthermore, the organic layer sequence comprises a second organic emitter layer for generating electromagnetic radiation of a second wavelength range.

[0006] The first and second emitter layers can contain or consist of an organic or organometallic light-emitting material. The light-emitting material is selected, for example, from phosphorescent and / or fluorescent substances. Furthermore, the first and second emitter layers can contain a matrix material in which the light-emitting material is embedded. Suitable phosphorescent substances include, for example, the following materials or combinations of materials: FIr6, FPt1 ([2-(4',6'-Difluorophenyl)-pyridinato)-acetylacetonate]-platinum-II), FIrpic (Bis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl)-iridium-III), FIrN4, Irppy3 (fac-Tris(2-phenyl-pyridyl)iridium complex), Ir(ppy)2acac, Ir(typ)3 (Tris[2-(4-totyl)-pyridinato]-iridium(III)), Ir(typ)2acac, Ir(bt)2acac, Ir(btp)2acac (Bis[2-(2-benzothienyl-pyridinato]-[acetyl-acetonato]-iridium(III)), Ir(dbp)2acac (Iridium(III)bis(dibenzo-[f,h]quinoxaline)-(acetylacetonate)), Ir(mdp)2acac (Iridium(III)bis(2-methyldibenzo-[f,h]quinoxaline) (acetylacetonate)), Ir(pq)3, Ir(pq)2acac, Ir(piq)3, (CF3ppy)2Ir(pic), PtOEP (Platinium octaethylporphyrin) or Os complexes, such as 3 [Os(fppz)2(PPhMe2)2] and [Os(fptz)2(PPh2Me)2] or [Os(fppz)2(dppee)].

[0007] Suitable fluorescent substances include, for example, the following materials or combinations of materials: DCM (4-(Dicyanomethylene)-2-methyl-6-(p-dimethylamino-styryl)4H-pyran), DCM2 (4-(Dicyanomethylene)-2-methyl-6-(julolidin-4-yl-vinyl)-4H-pyran), Rubren (5,6,11,12-Tetraphenyl-naphthacene), Coumarin (C545T), TBSA (9,10-Bis[(2",7" "-di-t-butyl)-9',9'' - spirobifluorenyl]anthracene), Zn complexes, Cu complexes.

[0008] For the first and / or second emitter layer, or as a matrix material for the first and / or second emitter layer in which fluorescent and / or phosphorescent substances can be incorporated, the following materials or combinations of materials are suitable, for example: CBP (4,4'-Bis(carbazol-9-yl)-2-2'-dimethyl-biphenyl), TCTA (4,4',4''-Tris(n-(naphth-2-yl)-N-phenyl-amino)triphenylamine), mCP, TCP (1,3,5-Tris-carbazol-9-yl-bezene), CDBP (4,4'-Bis(carbazol-9-yl)-2,2'-dimethyl-biphenyl), DPVBi (4,4-Bis(2,2-diphenyl-ethen-1-yl)-diphenyl), Spiro-PVBi (spiro-4,4'-Bis(2,2-diphenyl-ethen-1-yl)-diphenyl), ADN (9,10-Di(2-naphthyl)anthracene), perylene, carbazole derivatives, fluorene derivatives.

[0009] Preferably, in the OLED described here, the first and second emitter layers are arranged in a single organic layer sequence. In other words, there are no complete interruptions in the layer sequence between the first and second emitter layers, for example, in the form of predominantly inorganic electrodes. The first and second emitter layers are thus part of a common, continuous organic layer sequence.

[0010] According to at least one embodiment, the organic layer sequence comprises a charge generation layer sequence, or CGL, arranged between the first and the second emitter layer.

[0011] The first and second emitter layers are electrically connected in series via the CGL. The CGL is preferably an organic CGL.

[0012] According to at least one embodiment, the CGL comprises a converter material. This converter material, for example, partially or completely converts radiation from the first and / or second wavelength range into radiation from a third wavelength range. For instance, the organic light-emitting diode thus formed emits mixed light with components from the first, second, and / or third wavelength range. In particular, the mixed light can be white light, preferably warm white or cool white light.

[0013] Preferably, the first, second, and third wavelength ranges are each distinct from one another. This does not necessarily mean that the first, second, and third wavelength ranges are distinct from each other. Rather, the wavelength ranges may differ but overlap in certain areas.

[0014] In at least one embodiment, the OLED comprises an organic layer sequence with a first organic emitter layer for generating electromagnetic radiation of a first wavelength range and a second organic emitter layer for generating electromagnetic radiation of a second wavelength range. A CGL (converter-gap liquid) is arranged between the first and second emitter layers, through which the first and second emitter layers are electrically connected in series. The CGL further comprises a converter material that converts radiation of the first and / or second wavelength range at least partially into radiation of a third wavelength range. In this way, the organic light-emitting diode can emit mixed light with components of the first, second, and third wavelength ranges.

[0015] Mixed-light, especially white-light-emitting OLEDs, often require a complex layer structure. Generally, red, green, and blue emitter materials are used, which can be present in separate layers within an OLED or mixed in a common layer. Energy transfer processes, which often reduce efficiency and are frequently difficult to control, often occur between co-doped or directly adjacent emitter layers.

[0016] The invention described here is based in particular on the idea of ​​replacing one of the emitter materials, especially the red emitter, with a converter material. The converter material is inserted directly into the organic layer sequence within a CGL between two emitter layers. By eliminating one emitter material, for example the red emitter, additional application and combination possibilities arise for the remaining two emitter materials, for example the blue and green emitters. Since, for example, codoping between green and red emitters can be avoided in the OLED described here, a matrix material can be optimized exclusively for the green emitter, or further matrix materials can be added.

[0017] A further advantage of the OLEDs described here arises from the fact that the converter material is located within the organic layer sequence and not, as is usually the case, outside the layer sequence, for example on transparent electrodes. This allows all radiation modes generated within the layer sequence to be absorbed by the converter material, and not only those modes that are actually coupled out from the layer sequence. Furthermore, the layer sequence can serve as a protective shell for the converter material, thus enabling the use of even sensitive converter materials.

[0018] The CGL of the organic light-emitting diode comprises at least one n-type (electron-conducting) organic layer and at least one p-type (hole-conducting) organic layer. The n-type and p-type organic layers together form a diode that is preferably operated in reverse bias. This allows for the formation of a tunnel junction. Such a tunnel junction enables the efficient generation of n- and p-type charge carriers, or alternatively, allows different emitter layers to be electrically connected in series.

[0019] The CGL features a conversion layer. The converter material is partially or completely embedded in the conversion layer. The conversion layer is positioned between the n-type organic layer and the p-type organic layer. The conversion layer separates the n-type and p-type organic layers from each other, preventing direct contact between them. The conversion layer may, for example, be in direct contact with the p-type layer and / or the n-type layer.

[0020] The conversion layer can therefore separate the often reactive p-type and n-type organic layers of the CGL from each other, which ensures stable and low-voltage operation of the OLED.

[0021] The n-type conductive layer can comprise a material selected from the group consisting of NET-18, 2,2',2"-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole), 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazo-5-yl, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 8-hydroxyquinolinolato-lithium, 4-(naphthalen-1-yl)-3,5-diphenyl-4H-1,2,4-triazole, 1,3-bis[2-(2,2'-bipyridine-6-yl)-1,3,4-oxadiazo-5-yl]benzene, 4,7-diphenyl-1,10-phenanthroline (BPhen). 3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole, bis(2-methyl-8-quinolinolate)-4-(phenylphenolato)aluminum, 6,6'-bis[5-(biphenyl-4-yl)-1,3,4-oxadiazo-2-yl]-2,2'-bipyridyl, 2-phenyl-9,10-di(naphthalen-2-yl)-anthracene, 2,7-bis[2-(2,2'-bipyridine-6-yl)-1,3,4-oxadiazo-5-yl]-9,9-dimethylfluorene, 1,3-bis[2-(4-tert-butylphenyl)-1,3,4-oxadiazo-5-yl]benzene, 2-(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline, 2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline, tris(2,4,6-trimethyl-3-(pyridin-3-yl)phenyl)borane,1-methyl-2-(4-(naphthalen-2-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline, phenyldipyrenylphosphine oxides, naphthalene tetracarboxylic dianhydride and its imides, perylene tetracarboxylic dianhydride and its imides, materials based on silols with a silacyclopentadiene unit, and mixtures of the aforementioned substances.

[0022] Furthermore, the n-type layer can be doped. If the n-type layer is formed from a mixture of matrix and n-type dopant, the matrix can comprise one of the materials mentioned above. For example, the matrix can comprise NET-18. The n-type dopant of the n-type layer can be selected from a group that includes NDN-1, NDN-26, Na, Ca, MgAg, Cs, Li, Mg, Cs₂CO₃, and Cs₃PO₄.

[0023] The n-conducting layer can have a thickness in a range of approximately 1 nm to approximately 500 nm.

[0024] The p-type conductive layer can be made of a material selected from the group consisting of HAT-CN, F16CuPc, LG-101, α-NPD, NPB (N,N'-Bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine), beta-NPB N,N'-Bis(naphthalen-2-yl)-N,N'-bis(phenyl)-benzidine), TPD (N,N'-Bis(3-methylphenyl)-N,N'-bis(phenyl)-benzidine), Spiro TPD (N,N'-Bis(3-methylphenyl)-N,N'-bis(phenyl)-benzidine), Spiro-NPB (N,N'-Bis(naphthalen-1-yl)-N,N'-bis(phenyl)-spiro), DMFL-TPD N,N'-Bis(3-methylphenyl)-N,N'-bis(phenyl)-9,9-dimethyl-fluorene), DMFL-NPB (N,N'-Bis(naphthalen-1-yl)-N,N'-bis(phenyl)-9,9-dimethyl-fluorene), DPFL-TPD (N,N'-Bis(3-methylphenyl)-N,N'-bis(phenyl)-9,9-diphenyl-fluorene), DPFL-NPB (N,N'-Bis(naphthalen-1-yl)-N,N'-bis(phenyl)-9,9-diphenyl-fluorene), Spiro-TAD (2,2',7,7'-Tetrakis(n,n-diphenylamino)-9,9'-spirobifluorene), 9,9-Bis[4-(N,N-bis-biphenyl-4-yl-amino)phenyl]-9H-fluorene, 9,9-Bis[4-(N,N-bis-naphthalen-2-yl-amino)phenyl]-9H-fluorene, 9,9-Bis[4-(N,N'-bis-naphthalen-2-yl-N,N'-bis-phenyl-amino)phenyl]-9H-fluorine, N,N'-bis(phenanthren-9-yl)-N,N'-bis(phenyl)-benzidine, 2,7-bis[N,N-bis(9,9-spiro-bifluorene-2-yl)-amino]-9,9-spiro-bifluorene, 2,2'-bis[N,N-bis(biphenyl-4-yl)amino]9, 9-spiro-bifluorene, 2,2'-bis(N,N-di-phenyl-amino)9,9-spiro-bifluorene, di-[4-(N,N-ditolyl-amino)-phenyl]cyclohexane, 2,2',7,7'-tetra(N,N-di-tolyl)amino-spiro-bifluorene, N,N,N',N'-tetra-naphthalen-2-yl-benzidine, and mixtures of these compounds.

[0025] The p-type layer can also be doped. If the p-type layer is formed from a mixture of matrix and p-doper, the dopant can be selected from a group containing MoO₂. x , WHERE x VO x The range includes Cu(I)pFBz, Bi(III)pFBz, F4-TCNQ, NDP-2, and NDP-9. One or more of the above-mentioned materials can be used as the matrix material for the p-type layer.

[0026] The p-type conductive layer can have a thickness in a range of approximately 1 nm to approximately 500 nm.

[0027] According to at least one embodiment, the converter material in the conversion layer is embedded in a matrix material. The matrix material is, for example, one of the matrix materials mentioned above, which can also be used for the light-emitting substances of the first and / or second emitter layer. In particular, the matrix material is selected such that only a small, for example negligible, voltage drop occurs across the conversion layer. Preferably, the matrix material provides good separation between the highly reactive n- and p-type layers, so that they do not react with each other or only to a negligible extent.

[0028] According to at least one embodiment, the concentration of the converter material in the conversion layer is at least 50 / d %·nm, preferably at least 60 / d %·nm, and particularly preferably at least 65 / d %·nm. Alternatively or additionally, the concentration of the converter material in the conversion layer is at most 90 / d %·nm, or at least 80 / d %·nm, or at least 70 / d %·nm. The thickness d denotes the thickness of the conversion layer in nanometers. These concentration values ​​are particularly suitable for conversion layer thicknesses of at least 1 nm. The concentrations mentioned are therefore layer-thickness dependent; the greater the layer thickness, the lower the concentration. This allows the proportion of radiation converted by the conversion layer to be kept constant regardless of the selected layer thickness.

[0029] The specified percentage concentrations may refer here and in the following to the volume percent, the mass percent, or the mole percent of the converter material in the conversion layer.

[0030] As an alternative to the layer thickness-dependent concentration specifications, the conversion layer can also have an absolute concentration of the converter material of, for example, at least 50%, 60%, or 65%. Alternatively or additionally, the absolute concentration of the converter material is at most 90%, 80%, or 75%.

[0031] According to at least one embodiment, the conversion layer is formed entirely from the converter material.

[0032] According to at least one embodiment, the CGL, with the converter material contained therein, is configured to convert at least 10%, preferably at least 30%, and particularly preferably at least 50% of the electromagnetic radiation incident upon it into radiation of the third wavelength range. This can apply to radiation of the first and / or second wavelength range incident upon the CGL.

[0033] According to at least one embodiment, the first emitter layer emits light in the blue spectral range during operation, preferably in the wavelength range between 400 nm and 480 nm inclusive. The second emitter layer preferably emits light in the green spectral range, preferably in the wavelength range between 480 nm and 560 nm inclusive. The converter material is then, for example, configured to convert the blue light and / or the green light at least partially into red light, preferably into light in the wavelength range between 560 nm and 790 nm inclusive, or between 630 nm and 790 nm inclusive. Overall, the OLED described here can then emit light with red, blue, and green color components, which preferably results in white mixed light for an observer.

[0034] By replacing a red emitter layer with a red converter material, the use of expensive iridium complexes, which are typically used for red emitter materials, can be avoided. This reduces the manufacturing costs of the OLED described here.

[0035] According to at least one embodiment, the CGL and / or the converter material contained therein of the specified OLED is itself not electroluminescent. This means, in particular, that unlike the emitter materials in the emitter layers, the converter material does not emit radiation, or at least not radiation perceptible to an observer, in the third wavelength range simply by applying a defined electrical voltage or current to the organic layer sequence. Rather, the CGL, or the converter material contained therein, requires optical excitation with radiation, preferably with radiation of wavelengths smaller than the third wavelength range, to emit electromagnetic radiation in the third wavelength range. That is, the CGL is photoluminescent.

[0036] According to at least one embodiment, the converter material is an organic converter material. For example, the converter material comprises or consists of one of the following materials: fluoresceins, coumarins, rhodamines, stilbene derivatives, porphyrin derivatives, phthalocyanine derivatives.

[0037] According to at least one embodiment, molecules of the converter material exhibit a preferred direction or plane of light emission. For example, the molecules of the converter material have their greatest extent along a principal direction. During conversion or optical excitation, the molecules of the converter material can then, for example, develop a dipole moment along the principal direction and thereby preferentially emit light perpendicular to the principal direction. Such a preferred direction or plane can occur, for example, in larger molecules of a converter material. A preferred direction or plane means, for example, that at least 80% or at least 90% of the light is emitted into a solid angle of at most 4 / 5 π, at most 4 / 10 π, or at most 4 / 20 π around the preferred direction, or into an angular range of at most 50°, 30°, or 20° around the preferred plane.

[0038] According to at least one embodiment, the molecules of the converter material are directionally integrated into the organic layer sequence. This means, for example, that the molecules of the converter material are integrated into the organic layer sequence such that the preferred direction or plane of light emission for each molecule points in the same direction or directions. For example, the principal directions of the molecules of the converter material can be largely aligned parallel to each other. With such a directional arrangement of the molecules in the converter material, a preferred emission direction of the converter material can be specifically set. In particular, the preferred emission direction is chosen to be perpendicular to the principal plane of extension of the organic layer sequence.

[0039] According to at least one embodiment, the converter material has quantum dots. The quantum dots can, for example, be made of or composed of one of the following materials: GaAs, GaP, GaN, sulfides such as ZnS or CdS, or selenides such as ZnSe or CdSe.

[0040] According to at least one embodiment, the conversion layer has a thickness of at least 1 nm, or at least 5 nm, or at least 10 nm. Alternatively or additionally, the thickness of the conversion layer is at most 20 nm, or at most 18 nm, or at most 15 nm.

[0041] Since the materials preferred as converter materials generally exhibit intense absorption bands, for example in the blue or green spectral range, the conversion effect occurs even with very thin layers. By varying the layer thickness, the proportion of converted light can be precisely controlled, thus enabling adjustment of the emission color or color temperature.

[0042] According to at least one embodiment, particles of the converter material have a particle size of at least 1%, at least 10%, or at least 30% of the layer thickness d of the conversion layer. Alternatively or additionally, the particle size is at most 90%, at most 80%, or at most 60% of the layer thickness d of the conversion layer. The particle size is defined, for example, as the particle diameter, such as the D 50 Diameter of the particles in Q0, understood.

[0043] In particular, the particle size of the converter material can be at least 1 nm, or at least 5 nm, or at least 10 nm. Alternatively or additionally, the particle size can be at most 30 nm, or at most 20 nm, or at most 15 nm.

[0044] According to at least one embodiment, the converter material for light conversion is designed as a singlet emitter. This means, in particular, that during operation, radiation of the third wavelength range is generated by a transition from a singlet state to the corresponding electrical ground state.

[0045] Advantageously, by using a converter material instead of an emitter material, triplet emitters, which are often expensive, can be avoided, unlike in electroluminescent excitation. Instead, singlet emitters with intense absorption bands and high photoluminescence quantum efficiencies can be used.

[0046] According to at least one embodiment, the organic light-emitting diode (OLED) is a bidirectionally emitting LED. This means that the LED emits radiation in both directions perpendicular to a principal plane of extension of the organic layer sequence or the CGL. The LED is therefore a double-sided emitting LED, colloquially called a top-bottom emitter.

[0047] According to at least one embodiment, the OLED emits warm white light in one direction with a color temperature of at most 3500 K or at most 3200 K or at most 2800 K.

[0048] In the other direction, that is, in the opposite direction, the OLED then emits, for example, cool white light with a color temperature of at least 4000 K or at least 4300 K or at least 4600 K.

[0049] Such a bidirectional emitting OLED, with two different color temperatures, can be achieved, for example, by having the first emitter layer be a green-emitting layer, the second emitter layer a blue-emitting layer, and the converter material emitting red light. To an observer, the light emitted from the blue emitter layer then appears cooler than the light emitted from the green emitter layer.

[0050] According to at least one embodiment of the OLED, one or more organic layers in the layer sequence contain scattering particles for efficient light extraction. The scattering particles can be made of or consist of at least one of the following materials: titanium oxide, aluminum oxide, yttrium oxide, or silicon oxide. The size of the scattering particles is, for example, at most 1 µm, 600 nm, or 400 nm. Alternatively or additionally, the size of the scattering particles is at least 50 nm, 100 nm, or 200 nm. Layers adjacent to the organic layer sequence can also contain such scattering particles.

[0051] The scattering particles incorporated into the organic layers can scatter light of the first, second, and / or third wavelength range, thereby reducing the proportion of light that is totally reflected at the interfaces of the OLED. The scattering particles thus improve the light extraction efficiency and, consequently, the overall efficiency of the OLED described here.

[0052] According to at least one embodiment, the OLED has two electrodes, in particular an anode and a cathode. The organic layer sequence is then arranged, for example, between the anode and the cathode. The anode and the cathode thus serve to inject current into the organic layer sequence. Preferably, the OLED is operated with direct current.

[0053] According to at least one embodiment, the anode and / or the cathode can be transparent to the light generated by the organic layer sequence. In this context, transparent means that the anode and / or the cathode are, for example, clear and / or non-absorbing and / or non-reflective to the light generated by the organic layer sequence. The light generated in the layer sequence can then be extracted from the OLED via the anode and / or the cathode.

[0054] The transparent electrodes can, for example, contain or consist of a transparent conductive oxide. Transparent conductive oxides (TCOs) are typically metal oxides such as zinc oxide, tin oxide, cadmium oxide, titanium oxide, indium oxide, or indium tin oxide (ITO). Aluminum zinc oxides (ACO) or indium zinc oxides (IZO) are also suitable.

[0055] According to at least one embodiment, an organic charge injection and / or an organic charge transport layer is arranged between the first emitter layer and the electrode nearest to the first emitter layer. Alternatively or additionally, an organic charge injection and / or an organic charge transport layer can also be arranged between the second emitter layer and the electrode nearest to the second emitter layer. Preferably, the charge injection and / or charge transport layer nearest to the anode is configured as a hole injection and / or hole transport layer. The charge injection and / or charge transport layer nearest to the cathode is then preferably configured as an electron injection and / or electron transport layer.Furthermore, additional charge transport layers can also be arranged between the first and second emitter layers, for example between the CGL and the first and / or second emitter layer.

[0056] The charge injection and charge transport layers serve to effectively couple charge carriers from the anode or cathode into the organic layer sequence and subsequently enable efficient charge transport. Preferably, the charge injection layers are in direct contact with the electrodes.

[0057] Examples of materials with hole-transporting and / or hole-injecting properties include: 1-TNATA (4,4',4''-Tris(N-(naphth-1-yl)-N-phenyl-amino)triphenylamine), 2-TNATA (4,4',4''-Tris(10-(naphth-2-yl)-N-phenyl-amino)triphenylamine), MTDATA (4,4,4-Tris(N-3-methylphenyl-N-phenyl-amino)-triphenylamine), aNPD (N,N'-Bis(naphthalen-1-yl)-N,N'-bis(phenyl)benzidine), bNPD (N,N'-Bis(naphthalen-2-yl)-N,N'-bis(phenyl)benzidine), TPD (N,N'-Bis(3-methylphenyl)-N,N'-bis(phenyl)benzidine), spTAD (2,2',7,7'-Diphenylamino-spiro-9,9'-bifluorene), Cu-PC (phthalocyanine copper complex) or other PC metal complexes, TAPC (1,1-Bis-[(4-phenyl-)-bis-(4',4''-methyl-phenyl)-amino]-cyclohexane) and combinations thereof.

[0058] Examples of materials with electron-transporting and / or electron-injecting properties are: Alq3 (Tris(8-hydroxyquinoline)aluminium), BAlq2 (Bis-[2-methyl-8-quinolato]-[4-phenylphenolato]-aluminium (III)), BPhen (4,7-Diphenyl-1,10-phenanthroline), BCP (2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline), TPBi (1,3,5-Tris-(1-phenyl-1H-benzimidatol-2-yl)-benzene), TAZ (3-(4-Biphenyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole), TAZ2 (3,5-Diphenyl-4-naphth-1-yl-1,2,4-triazole), t-Bu-PBD (2-(-Biphenyl)-5-(4-tert-butyl-phenyl)-1,3,4-oxadiazole), triazine, triazine derivatives and combinations thereof.

[0059] According to at least one embodiment, one of the two electrodes is transparent, while the other electrode is largely or entirely made of a metal that is reflective or specular to the radiation emitted by the organic layer sequence. For example, the metallic electrode is made of silver, gold, aluminum, titanium, magnesium, barium, indium, calcium, samarium, lithium, or platinum, or an alloy of these materials. Such an OLED with a metallic electrode emits radiation predominantly in only one direction, namely away from the non-transparent electrode and through the transparent electrode.

[0060] According to at least one embodiment, the OLED has a transparent substrate onto which the organic layer sequence is deposited. Such a transparent substrate can, for example, mechanically stabilize the organic layer sequence and make the OLED self-supporting. The transparent substrate can, for example, be made of or consist of a clear or milky-opaque material such as glass. Preferably, radiation generated in the organic layer sequence can be coupled out of the OLED via the transparent substrate. For this purpose, the electrode, which is arranged between the transparent substrate and the organic layer sequence, is preferably also transparent.

[0061] According to at least one embodiment, at least one of the transparent electrodes of the OLED has output coupling elements in the form of scattering particles and / or surface structures. The scattering particles can be the aforementioned scattering particles, which can also be incorporated into the organic layers of the organic layer sequence. The surface structures can, for example, be roughenings on the electrodes. These surface structures can then be arranged on the side of the transparent electrode facing the organic layer sequence or on the side facing away from it. Preferably, the surface structures or the scattering particles of the transparent electrode have an extent that is at least one-eighth, one-quarter, or one-half of the wavelength emitted by the organic layer sequence.In this way, the light generated by the organic layer can be scattered at the output coupling elements of the transparent electrode, which in turn reduces losses of the OLED due to total internal reflection.

[0062] The organic light-emitting diode described here is explained in more detail below with reference to the drawings and exemplary embodiments. The same reference symbols indicate identical elements in the individual figures. However, the figures are not to scale; rather, individual elements may be exaggerated for clarity.

[0063] They show: Fig. 1 to 5 schematic sectional views of exemplary embodiments of the organic light-emitting diodes described here.

[0064] Fig. Figure 1 shows an organic light-emitting diode 1000, or OLED for short, with a substrate 8 and an anode 4 applied to the substrate 8. The substrate 8 is, for example, a transparent, clear substrate such as glass, and the anode 4 is, for example, made of a transparent conductive oxide such as ITO.

[0065] An organic layer sequence 100 is deposited on the side of the anode 4 facing away from the substrate 8. A cathode 5, which in this case is formed, for example, from a metal such as aluminum or silver, is arranged on the opposite side of the organic layer sequence 100. The cathode 5 is reflective or specular in design, so that electromagnetic radiation generated in the organic layer sequence 100 is reflected at the cathode 5 and directed towards the anode 4, and can be coupled out of the OLED 1000 via the anode 4 and the transparent substrate 8. This embodiment is described in the following example: Fig. 1 also a bottom emitter.

[0066] The organic layer sequence 100 of the Fig. 1 has a plurality of organic layers. The anode 4 is in Fig. 1. A hole injection layer 11, abbreviated HIL, and a hole transport layer 12, abbreviated HTL, are applied. The HIL 11 is preferably in direct contact with the anode 4. Holes from the anode 4 can be efficiently injected into the organic layer sequence 100 via the HIL 11 and subsequently transported further by means of the HTL 12.

[0067] On one side of HTL 12 facing away from anode 4, there is in Fig. 1. A first emitter layer 1 is applied. The first emitter layer 1 has, for example, a fluorescent or phosphorescent emitter material embedded in a matrix material. The emitter material in the first emitter layer 1 is selected such that the first emitter layer 1 generates radiation in a first wavelength range 10 during operation. In this case, for example, this is blue light.

[0068] On one side of the first emitter layer 1 facing away from the anode 4, there is in Fig. 1. A charge generation layer sequence 33, or CGL for short, is deposited. On one side of the CGL 33 facing away from the first emitter layer 1, a second emitter layer 2 is deposited, so that the CGL 33 lies between the first 1 and the second 2 emitter layer.

[0069] The second emitter layer 2 can in turn contain fluorescent and / or phosphorescent emitter material in a matrix material. During operation, the second emitter layer 2 emits radiation in a second wavelength range 20, for example, in the green wavelength range.

[0070] On one side of the second emitter layer 2 facing away from CGL 33, there is in Fig. 1 An electron transport layer 22, abbreviated ETL, and an electron injection layer 21, abbreviated EIL, are arranged. The EIL 21 serves to efficiently inject electrons from the cathode 5 into the organic layer sequence 100, while the ETL 22 transports the electrons to the second emitter layer 2. The EIL 21 is preferably in direct contact with the cathode 5.

[0071] In Fig. 1. The CGL 33 serves to connect the first emitter layer 1 and the second emitter layer 2 in series with each other; therefore, additional electrodes between the first emitter layer 1 and the second emitter layer 2 are not required. Fig. 1. In the CGL 33, during operation of the OLED 1000, both electrons for the operation of the first emitter layer 1 and holes for the operation of the second emitter layer 2 are generated. For this purpose, in the present example, the CGL 33 is configured as a pn junction, which is operated in reverse bias and acts as a tunnel junction. The CGL 33 has an n-type organic layer 6 facing the anode 4, which effectively acts as the electron generation layer, or n-CGL for short. Furthermore, the CGL 33 includes a p-type organic layer 7 facing the cathode 5, which serves as the hole generation layer, or p-CGL for short.

[0072] Between the n-conducting organic layer 6 and the p-conducting organic layer 7 there is a Fig. Furthermore, a conversion layer 3 is arranged, which separates the n-type organic layer 6 and the p-type organic layer 7 from each other. The conversion layer 3 contains a converter material that can at least partially convert the radiation of the first wavelength range 10 generated by the first emitter layer 1 and / or the radiation of the second wavelength range 20 emitted by the second emitter layer 2 into radiation of a third wavelength range 30. In this case, for example, a red converter material is chosen for the conversion layer 3, so that the blue light emitted by the first emitter layer 1 and the green light emitted by the second emitter layer 2 can be at least partially converted into red light. In this way, light with red, green, and blue color components can be emitted via the transparent anode 4 and the transparent substrate 8.

[0073] Because of the fact that in Fig. Since the second, green-emitting emitter layer 2 is arranged between the conversion layer 3 and the reflective cathode 5, all the green light emitted by the second emitter layer 2 must pass through the conversion layer 3 before it can be coupled out of the OLED 1000. The first, blue-emitting emitter layer 1, on the other hand, is arranged between the transparent anode 4 and the conversion layer 3, so that only the portion emitted from the first emitter layer 1 towards the cathode 5 has to pass through the conversion layer 3. Overall, in this embodiment, the Fig. 1. Thus, a relatively large proportion of green light is converted into red light, whereas only a relatively small proportion of blue light is converted into red light. This is the case with the OLED 1000. Fig. 1. The emitted light therefore has a high blue component and can be perceived by an observer, for example, as cool white light with a color temperature of at least 4000 K.

[0074] In the exemplary embodiment of the Fig. 2 are in contrast to the embodiment of the Fig. 1 simply swaps the first 1 and the second 2 emitter layers. The first emitter layer 1, which emits blue light of the first wavelength range 20, is in Fig. The second emitter layer 2, which emits green light of the second wavelength range 20, is located between the conversion layer 3 and the transparent anode 4. In the example of the Fig. 2 must therefore, unlike Fig. 1. In operation, only a portion of the green light passes through conversion layer 3 before light extraction, whereas all of the blue light emitted by the first emitter layer 1 must pass through conversion layer 3. Therefore, in Fig. 2. A relatively small proportion of green light is converted into red light, whereas a large proportion of blue light is converted into red light. This is the case with the OLED 1000. Fig. 2. The emitted light therefore has a large proportion of green and a less high proportion of blue and thus appears to an observer, for example, as warm white light with a color temperature of at most 3000 K.

[0075] In the exemplary embodiment of the Fig. In step 3, the reflective cathode 5 is replaced by a transparent cathode 5. For example, the transparent cathode 5 can be formed from a transparent conductive oxide. Due to the fact that in Fig. 3. If both electrodes are transparent, the OLED 1000 can be used. Fig. 3 emit light in both directions perpendicular to the main direction of extension of the conversion layer 3. In the case of the OLED 1000 of the Fig. 3. This is therefore a bidirectionally emitting OLED 1000. The arrangement of the organic layers within the organic layer sequence 100 is in Fig. 3 just like in the Fig. 1. Light coupled out of the OLED 1000 via the cathode 5 appears, in this example, to an observer as warm white light, since some of the blue light emitted by the first emitter layer 1 is partially converted into red light on its way to the cathode 5. On the other hand, light coupled out of the OLED 1000 via the anode 4 and the transparent substrate 8 appears, for example, to an observer as cool white light, since the blue light emitted by the first emitter layer 1 does not have to pass through the red-converting conversion layer 3 on its way to the anode 4.

[0076] In Fig. Figure 4 also shows a bidirectionally emitting OLED 1000, which has a similar structure to the OLED 1000 of the Fig. 3 exhibits. The layer structure of the organic layer sequence 100 is in Fig. 4 but chosen in the same way as in the Fig. 2, that is, the first emitter layer 1 is arranged between cathode 5 and conversion layer 3, whereas the second emitter layer 2 is arranged between conversion layer 3 and anode 4. Due to this reversed arrangement of the first 1 and second 2 emitter layers, in the Fig. 4 the light emitted via the cathode 5, for example, is perceived as cool white light, whereas the light emitted via the anode 4 is perceived as warm white light.

[0077] The exemplary embodiment of the Fig. Figure 5 shows the same layer structure of the OLED 1000 as the embodiment of the Fig. 4. Additionally, in Fig. However, an output coupling element is also applied to the side of the cathode 5 facing away from the organic layer sequence 100. In the present example, the output coupling element is designed as a roughening of the surface of the cathode 5. Light can be scattered at this roughening, thereby reducing total internal reflection within the OLED and increasing the light output efficiency via the cathode 5.

[0078] Such coupling elements can also be applied to the anode 4 or to the transparent substrate 8.

[0079] Furthermore, unlike in the Fig.Figures 1 to 5 show one or more of the organic layers or the electrodes 4, 5 containing scattering particles, which are, for example, in the form of titanium oxide particles a few hundred nanometers in size. Radiation generated by the organic layer sequence 100 can also be effectively scattered by such scattering particles, thus increasing the light extraction efficiency of the OLED 1000. Reference symbol list 1 first emitter layer 2 second emitter layer 3 Conversion layer 4 Anode 5 Cathode 6 n-conducting organic layer 7 p-conducting organic layer 8 Substrat 10 Radiation of the first wavelength 20 Second wavelength radiation 30 Radiation of the third wavelength 33 Charge carrier generation layer sequence, abbreviated CGL 100 organic layer sequence 1000 organic light-emitting diodes

Claims

[1] Organic light-emitting diode (1000) comprising an organic layer sequence (100) with: - a first organic emitter layer (1) for generating electromagnetic radiation of a first wavelength range (10), - a second organic emitter layer (2) for generating electromagnetic radiation of a second wavelength range (20), - a charge carrier generation layer sequence (33) arranged between the first (1) and the second (2) emitter layer, via which the first emitter layer (1) and the second emitter layer (2) are electrically connected in series, wherein - the charge carrier generation layer sequence (33) comprises a converter material which converts radiation of the first (10) and / or the second (20) wavelength range at least partially into radiation of a third wavelength range (30), so that the organic light-emitting diode (1000) emits mixed light with components of the first (10), second (20) and third (30) wavelength range, wherein the charge carrier generation layer sequence (33) comprises at least one n-type organic layer (6), at least one p-type organic layer (7) and a conversion layer (3), wherein the converter material is incorporated into the conversion layer (3), wherein the conversion layer (3) is arranged between the n-type layer (6) and the p-type layer (7) and separates the n-type layer (6) and the p-type layer (7) from each other. [2] Organic light-emitting diode (1000) according to the preceding claim, wherein - the converter material in the conversion layer (3) is embedded in a matrix material and - the concentration of the converter material in the conversion layer (3) for thicknesses of the conversion layer (3) of at least 1 nm is between 50 / d %·nm and 90 / d %·nm inclusive, where d is the thickness of the conversion layer (3) in units of nanometers. [3] Organic light-emitting diode (1000) according to one of the preceding claims, wherein the conversion layer (3) is formed entirely from the converter material. [4] Organic light-emitting diode (1000) according to one of the preceding claims, wherein the charge carrier generation layer sequence (33) is configured to convert at least 10% of the electromagnetic radiation of the first (10) and / or second (20) wavelength range incident on it into radiation of the third wavelength range (30). [5] Organic light-emitting diode (1000) according to one of the preceding claims, wherein in operation the first emitter layer (1) emits light in the blue spectral range, the second emitter layer (2) emits light in the green spectral range and the converter material converts the blue light and / or the green light at least partially into red light. [6] Organic light-emitting diode (1000) according to one of the preceding claims, wherein the charge carrier generation layer sequence (33) itself and the converter material contained therein are non-electroluminescent. [7] Organic light-emitting diode (1000) according to one of the preceding claims, wherein the converter material comprises or is formed from one of the following materials: fluoresceins, coumarins, rhodamines, stilbene derivatives, porphyrin derivatives, phthalocyanine derivatives. [8] Organic light-emitting diode (1000) according to one of the preceding claims, wherein molecules of the converter material have a preferred direction or plane in light emission, and wherein the molecules of the converter material are directed into the organic layer sequence (100) such that a preferred emission direction of the converter material is selectively set. [9] Organic light-emitting diode (1000) according to any one of the preceding claims, wherein the converter material has quantum dots comprising GaAs and / or GaP and / or GaN and / or sulfides and / or selenides. [10] Organic light-emitting diode (1000) according to one of the preceding claims, wherein the conversion layer (3) has a layer thickness d between 1 nm and 20 nm inclusive. [11] Organic light-emitting diode (1000) according to one of the preceding claims, wherein the converter material for light conversion is a singlet emitter which generates radiation of the third wavelength range by a transition from a singlet state to the associated electrical ground state. [12] Organic light-emitting diode (1000) according to any one of the preceding claims, wherein the light-emitting diode (1000) is a bidirectionally differently emitting light-emitting diode (1000) which emits radiation in both directions perpendicular to a principal extension plane of the charge carrier generation layer sequence (33), wherein warm white light with a color temperature of no more than 3500 K is emitted in one direction and cool white light with a color temperature of at least 4000 K is emitted in the other, opposite direction. [13] Organic light-emitting diode (1000) according to one of the preceding claims, wherein one or more organic layers in the layer sequence (100) or layers adjacent to the layer sequence have scattering particles comprising or formed from at least one of the following materials: titanium oxide, aluminum oxide, yttrium oxide, silicon oxide. [14] Organic light-emitting diode (1000) according to one of the preceding claims, wherein at least one transparent electrode adjacent to the organic layer sequence (100) has scattering particles and / or surface structures for better light extraction. [15] Organic light-emitting diode (1000) according to one of the preceding claims, wherein no complete interruptions of the organic layer sequence (100) are arranged between the first emitter layer (1) and the second emitter layer (2).

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