Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
  • G02B1/11—Anti-reflection coatings
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/80—Constructional details
  • H10K50/85—Arrangements for extracting light from the devices
  • H10K50/852—Arrangements for extracting light from the devices comprising a resonant cavity structure, e.g. Bragg reflector pair
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/80—Constructional details
  • H10K50/85—Arrangements for extracting light from the devices
  • H10K50/854—Arrangements for extracting light from the devices comprising scattering means

Definitions

• the invention relates generally to electro-optical elements and methods for their production.
• the invention relates to an organic electro-optical element with increased coupling-out efficiency, and to a method for its production.
• OLEDs Organic light-emitting diodes
• OLED layer structures with internal quantum efficiencies of 85% are already known.
• the efficiency of OLEDs is significantly reduced by coupling losses. Reflection losses occur at the existing interfaces of adjoining media with different refractive indices.
• This jump in the refractive index leads to total reflection of light which, coming from the interior of the OLED, strikes the interface at an angle which is greater than the critical angle. This in turn reduces the solid angle at which the radiation can be coupled out.
• the approximation applies to the fraction ⁇ of the radiation that can be coupled out:
• n denotes the highest refractive index of the individual layers of the OLED.
• an OLED comprises an organic electroluminescent layer, the light of which is transmitted through a transparent, conductive electrode layer, e.g. made of indium tin oxide (ITO), and a transparent support, such as in particular a glass support, a glass ceramic or polymer film with a preferred barrier coating is coupled out.
• a transparent, conductive electrode layer e.g. made of indium tin oxide (ITO)
• ITO indium tin oxide
• An OLED is described in US 2002/0094422 Al further discloses, in which between the ITO transparent electrode layer and the substrate an intermediate layer is arranged, which has a varying refractive index, wherein the refractive index at the interfaces of the intermediate layer respectively to the refractive index of the adjacent materials Has.
• micro-optical elements such as lenses or truncated cones placed on the OLED structures.
• these structures are only effective if the active area of the OLED is smaller than the surface part assigned to this area.
• the coupling efficiency is increased considerably, but at the same time the. light-emitting surface of the OLED is reduced, so that no significant increase in the overall brightness is achieved in this way.
• Solutions to the problem are therefore at best suitable to achieve a higher luminance in pixel displays in which there are non-luminous gaps between the individual OLED structures anyway.
• the object of the invention is therefore to provide an organic electro-optical element with increased coupling-out efficiency, which can be produced in a simple manner and whose service life is not impaired by the measures for increasing the coupling-out efficiency.
• This object is already achieved in a most surprisingly simple manner by an organic, electro-optical element and a method for producing an organic, electro-optical element according to the independent claims.
• Advantageous further developments are the subject of the respective dependent claims.
• an organic, electro-optical element according to the invention, a substrate and at least one electro-optical structure which comprises an active layer with, at least one organic, electro-optical material, the substrate at least one
• the layer of the anti-reflective layer has a thickness and a refractive index for which the integral reflectivity at the interfaces of the anti-reflective layer for the active layer starts at all angles Light rays and for a wavelength in the spectral range of the emitted light is minimal, or for which the integral reflectivity is at most 25 percent, preferably 15 percent, particularly preferably 5 percent higher than the minimum of the integral reflectivity.
• the integral reflectivity is the reflectivity integrated across all emission angles of light rays emanating from the active layer, at the interfaces of the anti-reflective layer.
• the minimum of the integral reflectivity is also understood to mean the minimum value of the integral reflectivity which can be achieved by varying the values for the refractive index and the layer thickness of the anti-reflective layer, for example in the case of a single-layer layer, for the anti-reflective layer under otherwise unchanged conditions.
• the refractive index can be set uniformly and without dispersion over the entire layer thickness.
• An anti-reflective substrate in particular glass substrate with an anti-reflective layer with at least one layer, which has a thickness and a refractive index, for which the integral reflectivity at the interfaces of the anti-reflective layer is minimal for light rays emanating from all angles in the active layer or for which the integral Reflectivity which is at most 25 percent higher than the minimum can be used as a support for an organic, electro-optical element, such as in particular an organic, light-emitting diode, but of course also as a support or attachment for other light-emitting devices.
• a substrate provided with an anti-reflective layer according to the invention can also be used for all other applications in which light not only strikes the substrate or is transmitted through it under perpendicular incidence.
• an improved anti-reflective treatment can be achieved with a single-layer anti-reflective coating in a particularly advantageous manner.
• the invention can also be extended to multilayer anti-reflective coatings for these applications as well.
• Such a substrate according to the invention accordingly generally has an antireflection coating with at least one layer, as is here specifically for electro-optical
• optical devices such as optical components, panes, in particular window panes for buildings - both simple window panes, as well
• Optical components with anti-reflective layers according to the invention can be, for example, lenses, also spectacle lenses, prisms or optical filters.
• the invention is particularly suitable for optical devices of this type which are designed for the transmission of light emerging from the substrate or entering the substrate at a wide angular range.
• An anti-reflective layer significantly increases the out-coupling or coupling-in efficiency of light that passes through the substrate compared to an uncoated substrate, since the anti-reflective coating at least partially suppresses back reflections.
• the layer thickness and the refractive index of the anti-reflective coating are not optimized for vertical incidence, which leads to a layer thickness of a quarter of the light wavelength known from the prior art, but rather all possible directions of emitted light beams are taken into account.
• Anti-reflective coating to increase the transmission from the active layer into the substrate and / or by a factor of 2 when the light emerges on the visible side of the element, which accordingly also brings about a significant increase in the overall external quantum efficiency.
• the layer thickness and the refractive index of the anti-reflective layer are selected such that the integral of the reflectivity of the anti-reflective layer
• n 2 denote the refractive index of the
• Anti-reflective coating, ni and n 3 the refractive indices of the media adjacent to the anti-reflective coating, ⁇ den Angle of the emitted light to the perpendicular to the interface of the anti-reflective layer facing the emitter and d the layer thickness of the anti-reflective layer.
• R TE and R TM are the reflection coefficients for TE, 10 and TM polarized light, respectively. The following applies to the reflection coefficients:
• the angle oi designates the angle of a light beam striking the anti-reflective layer to the perpendicular to the interface and thus corresponds to the angle ⁇ .
• the angle ⁇ 2 is the angle measured at the interface to the perpendicular
• the angle ⁇ 3 also denotes the angle of the light beam refracted again at the opposite interface to the medium with the refractive index n 3 and traveling in this medium.
• Vacuum is designated ⁇ o.
• an anti-reflective layer designed as described above with minimal or only a maximum of 25% reflectivity deviating from the minimum generally has much thicker layer thicknesses than are usually used for anti-reflective layers.
• a good anti-reflective effect can already be achieved with a substrate with an anti-reflective layer with at least one layer, in which the layer of the
• Anti-reflective coating preferably all layers of the multi-layer anti-reflective coating
• Antireflection coating have an optical thickness of at least 3/8 'of a wavelength of the transmission or emission spectrum, preferably even at least half a wavelength.
• the wavelength to which this optical thickness relates preferably depends on the particular application.
• this wavelength preferably a wavelength of the spectral range of the emission spectrum, particularly preferably the mean wavelength- of the spectrum emitted by the element or the mean wavelength of that with the
• Eye sensitivity weighted emission spectrum In the case of window glass or a lens, the mean wavelength of the visible spectrum or of the visible spectrum weighted with the sensitivity to the eye can be used analogously to calculate the layer thickness.
• the integral reflectivity of the layer thickness and the refractive indices is the
• Antireflection coating n 2 and those of the adjacent media, n 2 and n 3 depending, the refractive indices of the adjacent media can be determined by specifying the material.
• the maximum integral transmission for light rays emanating from an imaginary emitter in the active layer could also be determined using the relationships 2) to 5), whereby for the integral transmission T (nj, n, n_, d, ⁇ ) applies:
• T (n ⁇ , n 2 , n 3 , d, ⁇ ) 1 - R (nn 2 , n 3 , d, ⁇ ).
• the position of the anti-reflective layer has a thickness and a refractive index for which the light beams emanating from all active angles and the wavelengths of the spectral range of the emitted radiation are integrated and with the spectral intensity distribution weighted reflectivity at the
• Interfaces of the anti-reflective layer is minimal, or at most 25 percent, preferably 15 percent, particularly preferably "5 percent higher than the minimum.
• This integral I (n ⁇ , n 2 , n 3 , d) can be determined by:
• Equation 6 For the reflectivity R (ni ( ⁇ ), n 2 ( ⁇ ), n 3 ( ⁇ ), ü, U) the same relationships apply as for equation (1), so that equations 2) - 5) are advantageous for calculation. can be used. If, as in Equation 6, integration is also carried out over a wavelength range, then the dispersion of the media or the dependence of the refractive indices ni, n 2 , n 3 on the wavelength must also be taken into account. S ( ⁇ ) denote the spectral
• Integration limits of the spectral range With the spectral intensity distribution function S ( ⁇ ) the values of the reflectivity R (m ( ⁇ ), n 2 ( ⁇ ), n 3 ( ⁇ ), d, ⁇ ) are weighted.
• the limit values ⁇ i and ⁇ 2 of the integration over the wavelength can denote, for example, the limits of the wavelength range of the emission. However, narrower limits or a sub-spectral range can also be selected as integration limits. This is useful, for example, if the active layer also emits in wavelengths for which one or more of the materials used are opaque.
• the extrinsic spectral emission probability is easier to determine than the intrinsic emission probability of the active layer. In general, however, this can be replaced by the extrinic spectral distribution to determine the layer thickness and the refractive index.
• the position of the anti-reflective layer has a thickness and a refractive index for which the light rays emanating from all the angles of the active layer and the wavelengths of the spectral range of the emitted radiation are integrated and with the spectral intensity distribution and the spectral Ocular sensitivity-weighted reflectivity at the interfaces of the anti-reflective layer is minimal, or at most 25 percent, preferably 15 Percent, particularly preferably 5 percent, is higher than the minimum.
• This integral I (n ⁇ , n 2 , n 3 , d) can be calculated by:
• an organic, electro-optical element encompasses both an organic electroluminescent or light-emitting element, such as an OLED, and a photovoltaic element which has an organic material as a photovoltaically active medium.
• OLED organic electroluminescent or light-emitting element
• a photovoltaic element which has an organic material as a photovoltaically active medium.
• OLED is also generally used for organic light-converting elements, that is to say both for light-emitting elements and for photovoltaic elements, on account of the equivalent structure.
• the layer structure of an OLED or an appropriately constructed photovoltaic element is understood as an electro-optical structure.
• Such a structure comprises, accordingly, generally a first and second conductive layers between which an active layer is arranged, which 'comprises the. At least one electro-optic material.
• the first and second conductive layers, which serve as electrodes for the electro-optical structure also generally have different work functions, so that a work function difference arises between the two layers.
• the mechanism of light generation in the electro-optical material of an OLED is generally understood to be based on the recombination of electrons and holes, or the recombination of excitons with the emission of light quanta.
• LUMO Large Unoccupied Molecular Orbital
• HOMO Highest Occupied Molecular Orbital
• the substrate comprises glass, in particular soda-lime glass and / or plastic.
• the integral 1) can be calculated, for example, by recursively applying the relationships 2) to 5) given above for the individual layers of the anti-reflective layer.
• the relationships 2) to 5) given above for the individual layers of the anti-reflective layer.
• Relevant computer programs or specialist articles or specialist books for calculation are known to the person skilled in the art.
• a plurality of 'anti-reflection layers, or a multi-layer system with a combination of high, medium or low-refractive individual layers For this purpose, the layer materials known from the coating of optical components, such as titanium oxide, tantalum oxide, niobium oxide, hafnium oxide, aluminum oxide or silicon oxide, but also nitrides, such as, for example, magnesium nitride, can advantageously be used. However, other coating materials or combinations and mixtures of these materials known to the person skilled in the art, in particular for producing middle refractive layers, are also to be provided for realizing the invention.
• the method comprises the steps: coating at least one side of a substrate with an anti-reflective layer, and
• At least one electro-optical structure which comprises at least one organic electro-optical material
• the substrate is coated with an antireflection coating comprising at least one layer with 'a thickness and a refractive index, for which the integral reflectivity at the interfaces the anti-reflective layer for light rays emanating from the active layer at all angles and for a wavelength in the spectral range of the emitted light of the electro-optical material is minimal or for which the integral reflectivity is at most 25 percent higher than the minimum.
• the layer thickness and the refractive index of the anti-reflective layer are selected in accordance with a minimization of the relationships 1), 7) or 8) given above in conjunction with equations 2) to 5).
• All known layer deposition processes such as vacuum coating processes, in particular physical vapor deposition (PVD) or sputtering, chemical deposition processes from the gas phase (CVD) which are thermally or plasma-assisted (PECVD) or pulsed (for example PICVD) are suitable for coating with the anti-reflective coating ) can be carried out, or coatings from the liquid phase, such as sol-gel coating, dip, spray or spin coating.
• PVD physical vapor deposition
• PECVD plasma-assisted
• PICVD pulsed
• Particularly inexpensive and advantageous for the large-scale manufacture of electro-optical elements is one-, pus formation of the inventive method, wherein the step of coating at least one side of a substrate with an antireflection coating includes the step of dip coating the substrate.
• Dip coating can be used to produce scratch-resistant and weather-resistant layers with versatile optical properties efficiently and inexpensively.
• the anti-reflective coating of the substrate has titanium oxide - titanium oxide has a high refractive index and can be applied to the substrate in a simple manner by means of dip coating.
• the desired refractive index of the anti-reflective layer or one of the layers of the anti-reflective layer can also be set during production.
• the step of applying at least one electro-optical structure preferably also comprises the steps of: applying a first conductive layer, applying an active layer which comprises the at least one organic, electro-optical material, and applying a second conductive layer.
• the at least one anti-reflective layer has several layers, or if the step of coating at least one side of a substrate with an anti-reflective layer comprises the step of coating with an anti-reflective layer which comprises several Layers. It is particularly advantageous if the
• Layers each have different refractive indices.
• the step of coating with an antireflection coating which has a plurality of layers, in particular three layers, can accordingly advantageously comprise the steps: applying a layer with a medium refractive index, applying a layer with a high refractive index, and applying a layer with a low refractive index.
• layers of the electro-optical structure itself can also be included in the anti-reflective coating.
• an ITO layer of the electro-optical structure can adjoin a two-layer anti-reflective layer in order to form a three-layer anti-reflective layer together with these two layers with correspondingly matched refractive indices.
• the anti-reflective layer has at least two layers, one of the conductive layers of the electro-optical structure being adjacent to the anti-reflective layer.
• the at least one antireflection coating and the at least one electro-optical structure can advantageously be applied to the same side of the substrate. This creates an electro-optical element in which reflections are reduced when the light passes through at the interface between the substrate and the electro-optical structure. Furthermore, at least one matching layer can be applied to the anti-reflective layer applied in this way before the layers of electro-optical structure are applied, in order to create an optical layer. To match the refractive indices of the electro-optical structure.
• the at least one antireflection coating and the at least one electro-optical structure can also be applied to opposite sides of the substrate.
• reflection suppression is created on the viewing or light exit side.
• An anti-reflective layer according to the invention is arranged on the side on which the electro-optical
• At least one matching layer is arranged between the anti-reflective layer and the electro-optical structure.
• the at least one adaptation layer advantageously also an adaptation layer stack, or a multilayer adaptation layer can advantageously serve to better coordinate the optical properties of the anti-reflection layer and the electro-optical structure.
• anti-reflective layers can also be applied to the substrate on both sides. If both sides of the substrate have anti-reflective layers according to the invention, an extensive improvement in the coupling and / or coupling of light out and into the element is brought about.
• the organic, electro-optical elements according to the invention in particular also OLEDs, can also be produced in a simple manner by, for example, already producing an anti-reflective substrate with at least one anti-reflective layer according to the invention which has an optimized or improved layer thickness and refractive index according to the invention with regard to the integral reflectivity, is used.
• the use of AMIRAN® glass as substrate as is already used extensively, for example, for low-reflection window glasses, with suitably adapted layer thicknesses of the layers of the anti-reflective layers, is particularly suitable for this purpose.
• an anti-reflective layer therefore also comprise an AMIRAN® coating, wherein the layer thicknesses of the anti-reflective layer can be adapted according to the invention, or an additional anti-reflective layer designed according to the invention is applied.
• an organic electro-optical element comprises at least one electro-optical structure with an active layer with organic, electro-optical material, wherein an anti-reflective layer is arranged between the substrate and the electro-optical structure, and wherein light-scattering structures between the electro-optical structure and the substrate are present.
• the light-scattering structures in a surprisingly simple manner, also bring about a significant increase in the coupling-out or coupling-in efficiency compared to known OLED elements, just like a layer which is optimized with regard to its thickness and refractive index.
• an anti-reflective glass substrate with "an anti-reflective layer with light-scattering structures can be used as a support for both an organic, electro-optical element, such as in particular an organic, light-emitting diode," and also for other light-emitting elements, such as semiconductor diodes or inorganic electroluminescent elements.
• an organic, electro-optical element such as in particular an organic, light-emitting diode
• other light-emitting elements such as semiconductor diodes or inorganic electroluminescent elements.
• the light-scattering structures can be present in the anti-reflective layer. This can be implemented in a simple manner, for example by a
• Anti-reflective layer is applied, the light-scattering structures, for example in the form of crystallites, Contains particles or inclusions that have a different refractive index and / or a different orientation from the surrounding material.
• an additional layer which has light-scattering structures to increase the coupling-out efficiency.
• This layer can be arranged, for example, between the substrate and the electro-optical structure.
• the additional layer is arranged on the substrate or in contact with the substrate, or is applied to it, and has a refractive index which essentially corresponds to the substrate refractive index. on . In this way arise at the
• Interface between this layer and the substrate has no reflections which reduce the coupling-out efficiency.
• Anti-reflective coating on light-scattering structures Such an arrangement can be produced by applying the anti-reflective layer to a structured side of the substrate.
• the substrate surface can - on that for the
• Antireflection layer provided side are roughened.
• the substrate surface can also be provided with regular structures and the anti-reflective layer can be applied to this substrate side.
• ⁇ are, for example, a hole injection layer and / or a potential adaptation layer and / or an electron blocking layer and / or a hole blocking layer, and / or a hole and / or an electron conductor layer and / or a
• Electron injection layer advantageous for the quantum efficiency of the organic, electro-optical structure, these layers also being arranged like the active layer between the first and second conductive layers.
• the layers are applied or arranged in the order hole injection layer / potential adaptation layer / hole conductor layer / electron blocking layer / active layer / hole blocking layer / electron conductor layer / electron direction layer. Parts, combinations or multiple uses of these functional layers which are known to the person skilled in the art can also be used.
• Fig. 5 is a calculation of the integral
• Reflectivity of an anti-reflective layer for different values of the layer thickness and the refractive index of the anti-reflective layer 6A and 6B embodiments of electro-optical
• Fig. 1 shows a cross section through a first embodiment of an electro-optical element according to the invention, which is designated as a whole with 1.
• a transparent, flat or plate-shaped substrate 2 serves as the carrier of the element 1, glass or and / or plastic being preferably used as the substrate material.
• substrate thicknesses in the range from 10 to 2000 micrometers, preferably in the range from 50 to 700 micrometers, are suitable.
• an electro-optical structure 4 is arranged on the side 22 of the substrate 2.
• the electro-optical structure 4 comprises a first and a second conductive layer 41 and 42, between which an active layer 6 is arranged.
• the active layer 6 contains organic, electro-optical material.
• an anti-reflective layer 10 is also arranged, which reflections between the substrate 2 facing conductive layer 41 and the surface of the substrate 2 is reduced.
• the refractive index of the anti-reflective layer 10 is preferably chosen so that it lies between the refractive index of the adjacent layers. In the case of customary simple, single-layer anti-reflective or refractive index matching layers, their thickness is generally chosen such that it corresponds to a quarter of the wavelength of the emerging light. For the refractive index of the anti-reflective layer, the geometric mean of the two refractive index values of the media adjacent to the anti-reflective layer is also set as the optimum, according to the teaching known from the prior art.
• a single-layer anti-reflective layer of an electro-optical element 1 according to the invention in which the integral reflectivity at the interfaces of the anti-reflective layer is minimal for light rays emanating from all angles in the active layer, has a refractive index and a layer thickness that deviates completely from these values.
• the values for the refractive index and layer thickness of layer 10 can also deviate so far that the integral reflectivity resulting from these values is at most 25 percent, preferably at most 15 percent, particularly preferably at most 5 percent, is higher than the theoretically achievable minimum of the integral reflectivity.
• Relationships 1) to 5) given above in FIG. 1 show an imaginary emitter 13 in the active layer 6 and a light beam 10 emanating from this emitter.
• the angle cti denotes the angle measured by the perpendicular to the interface between the layer 41 and the anti-reflective layer 10 of the through the Layer 41 of running light beam.
• the angle ⁇ 2 is the angle of the light beam measured at the interface between the layer 41 with the refractive index n x and the anti-reflective layer with the refractive index n 2, which is refracted in the anti-reflective layer.
• the angle ⁇ 3 is also the angle of the light beam which is running in the substrate 2 and is refracted at the opposite interface of the anti-reflective layer 10 to the substrate 2 with the refractive index n 3 .
• the refractive index and the layer thickness of the position of the anti-reflective layer 10 can also be selected such that the light rays emanating from the active layer 6 over all angles and the wavelengths integrated the Spe 'ktral Schemes "of the emitted radiation and preferablyete- with the spectral intensity distribution of reflectance at the interfaces of the Entspieg.elungs slaughter 10 is minimal, or at most 25 percent, preferably 15 percent, more preferably 5 percent higher than the minimum of the weighted and integrated
• This integral can be calculated according to equation 7) and the values of the refractive index and the layer thickness can be determined for the minimum achievable value of the integral.
• An additional improvement can also be achieved if one for the position of the anti-reflective layer 10 Thickness and a refractive index is selected for which the reflectivity at the interfaces of the anti-reflective layer 10, which is integrated over all angles of the light rays emanating from the active layer and the wavelengths of the spectral range of the emitted radiation and is weighted with the spectral intensity distribution and additionally the spectral sensitivity, is minimal , or at most 25 percent, preferably 15 percent, particularly preferably 5 percent, is higher than the minimum.
• Equation 8 can be made. Due to the additional consideration of eye sensitivity, an even better result regarding the brightness of the OLED element 1 is subjectively achieved for the viewer.
• the values for the refractive index and the layer thickness of the minima of the integrals of the reflectivities weighted with the spectral intensity distribution or - additionally with the eye sensitivity - usually also correspond to the minimum of the integral reflectivity for a single wavelength in the spectral range of the emitted radiation according to equation 1) , even if the light emitted is not monochromatic. However, the minimum of the integral reflectivity according to equation 1) can then be at a wavelength at which the emitted intensity is not maximum.
• FIG. 2 shows a cross section through a further embodiment of an organic, electro-optical element 1 according to the invention.
• a first anti-reflective layer 8 is applied to the substrate 2 on a first side 21 and a second anti-reflective layer 10 is applied to a second side 22.
• the anti-reflective layers each comprise three layers 81, 83, 85 or 101, 103 and 105.
• the layers of the Anti-reflective layers each have different refractive indices from one another.
• the layers are arranged in such a way that, starting from the substrate, they have a layer sequence with a medium refractive index / high refractive index / low layer
• layers 83 and 103 have a higher refractive index than layers 81 and 101, and layers 85 and 105, layers 85 and 105 each having the lowest refractive indices of the anti-reflective layers 8 and 10.
• each of the layers 81, 83, 85, or 101, 103 and 105 of the two anti-reflective layers 8 and 10 are chosen such that the integral reflectivities of the
• Anti-reflective layers 8, 10 are each minimal or deviate from the minimum by a maximum of 25%.
• an electro-optical structure 4 is applied with an active layer 6, which comprises an organic, electro-optical material.
• Anti-reflective layer 8 is on side 21 of the substrate
• the electro-optical structure 4 comprises a first and a second conductive layer 41 and 42, between which an active layer 6 is arranged, which contains the organic, electro-optical material.
• Layer 41 of the electro-optical structure is made, for example, of partially transparent, conductive material, such as indium tin oxide (ITO), a transparent conductive oxide (TCO) or a thin metal layer.
• ITO indium tin oxide
• TCO transparent conductive oxide
• FIG. 3 shows a cross section through a further embodiment of an organic, electro-optical element 1 according to the invention.
• This embodiment differs from the embodiment shown in FIG. 2 by an additional matching layer 5 between the electro-optical structure 4 and the anti-reflective layer 10.
• the matching layer 5 serves for better refractive index matching between the anti-reflective layer 10 and the conductive layer 41 of the electro-optical Structure 4.
• the adaptation layer can also be designed in multiple layers, the adaptation layer 5 shown by way of example comprising the four layers 51, 52, 53 and 54.
• the adaptation layers are particularly favorable when differently constructed electro-optical structures are to be combined with a substrate with a prefabricated anti-reflective coating.
• a specified type of substrate can be changed for several different ones without changes electro-optical structures can be used.
• the AMIRAN ® substrates that were originally intended for other applications can be used in this way.
• FIG. 4 shows yet another embodiment of the organic electro-optical element 1 according to the invention.
• the anti-reflective layer 10 comprises two layers 101 and 103.
• the anti-reflective layer 10 of this embodiment which is adjacent to the conductive layer 41, therefore no third layer 105. Rather, the conductive layer 41 itself takes on the function of a third layer of a three-layer anti-reflective layer.
• layer 103 preferably has the highest refractive index among the layers.
• Anti-reflective layer 8, 10 have a thickness and a refractive index for which the integral reflectivity at the interfaces of the anti-reflective layer 10 for at all angles in the active layer outgoing light rays for a wavelength in the emitted spectral range is minimal or for which the integral reflectivity is at most 25 percent higher than the minimum.
• the integral reflectivity can nevertheless accordance with above-mentioned equations 1), 7) or 8) of the complete, multi-layer anti-reflection layer 8, respectively 10.
• equations 1), 7) or 8) of the complete, multi-layer anti-reflection layer 8 respectively 10.
• the relationship 2) to 5) for the individual layers 81, 83, 85, and 101, 103, 105 of the anti-reflective layers are calculated numerically.
• Embodiments of organic electro-optical elements can also have one or more layers of the anti-reflective layer 10 and light-scattering structures.
• FIG. 5 shows graphs of the integral reflectivity of a single-layer anti-reflective layer, as it has the exemplary embodiment of FIG. 1, as a function of the refractive index and layer thickness of the anti-reflective layer 10.
• Refractive index of n 1.85 assumed.
• a glass with a refractive index of n 3 1.45 was used as the basis for the calculation 2.
• Various discrete values of the integral reflectivity in the range from 0.193 to 0.539 are shown in FIG. 5 as curves.
• the curve with an integral reflectivity of 0.193 also limits the range of values of refractive index and layer thickness of the anti-reflective coating, in which the integral reflectivity is at most 25% higher than the minimum value of 0.154.
• Point B denotes the values for the refractive index and layer thickness of an anti-reflective layer, which is conventionally optimized for perpendicular light emission as a quarter-wavelength layer with the same adjacent media.
• an inventive 'anti-reflection layer has surprisingly for the configuration described with respect to a conventional quarter-wavelength layer a considerably higher layer thickness and a significantly lower refractive index.
• the length of the anti-reflective layer is one has an optical thickness of at least 3/8 of a wavelength of the transmission or emission spectrum, preferably even at least half a wavelength.
• the range of at least half a wavelength of optical thickness is above . about 163 nanometers layer thickness.
• The. lower limit of this range is shown in FIG. 5 by a dashed line with " ⁇ / 2" line and the lower limit of the range of an optical thickness of at least 3/8 of the wavelength by a dotted line labeled "(3/8) - ⁇ .
• FIGS. 6A and 6B show cross sections through various exemplary embodiments of electro-optical structures 4.
• the substrate ' 2, on which the electro-optical structure .4 is applied, is shown without an anti-reflective layer in each case for the sake of clarity.
• the first conductive layer 41 comprises an indium-tin oxide layer 411, which in FIG. 6A.
• Hole injection layer 14 applied.
• This can comprise, for example, a polymer layer which contains, for example, polyanillin or PEDOT / PSS (“poly (3,4-ethylenedioxythiophene) / poly (styrene sulfonate)”).
• MEH-PPV denotes the polymer (poly (2-methoxy, 5- (29-ethyl-hexyloxy) -1, 4-phenylene vinylene)).
• the second conductive layer 42 applied to the active layer 6 comprises a calcium-aluminum two-layer system 421.
• the basic layer sequence ITO layer / PEDOT / PSS layer / MEH-PPV layer / Ca / Al layer of this embodiment has proven itself, inter alia, for use as OLED, with a layer structure of this type occasionally achieving well over 10,000 operating hours could.
• FIG. 6B A further exemplary embodiment of an electro-optical structure 4 is shown in FIG. 6B.
• This has an additional hole transport layer 18 which is applied after the hole injection layer 14.
• Suitable material for a hole transport layer 18 is, for example, N, N '-diphenyl-N,' -bis (3-methylphenyl) -1,1'-biphenyl-4, 4 '-diamine (TPD).
• the active, electroluminescent layer 6 comprises a layer 62 as organic, electro-optical material, which has Alq 3 (Tris (8-quinolinolato) - aluminum);
• organic molecules with a low mass number (“small molecules”), which can be vapor-deposited by means of PVD, as well as organic electroluminescent polymers can also be used as organic electroluminescent materials.
• the conductive layer 42 of this embodiment includes a layer 422 made of a low work function magnesium-silver alloy.
• a large number of further suitable electro-optical structures are known which are suitable for OLEDs or corresponding photovoltaic elements and can be used for the present invention.
• a large number of organic, electroluminescent materials, conductive electrode layers and, in addition to the hole transport and hole injection layers mentioned above, many other functional layers are known, which increase the efficiency of OLEDs or photovoltaic elements.
• FIGS. 7A to 7E show embodiments of the invention in which the anti-reflective layer 10 also has light-scattering structures 7 which at least a part of what passes through the layer 10
• the light-scattering structures can be present both inside the layer 10 and at one or both interfaces of the layer 10.
• FIG. 7A shows an exemplary embodiment of an organic electro-optical element 1 with a single-layer anti-reflective layer 10.
• the basic structure of this element 1 according to the invention corresponds to the embodiment shown in FIG. 1.
• the electro-optical structure 4 is shown in simplified form with a three-layer structure, but can be constructed, for example, in accordance with FIGS. 6A and 6B.
• the anti-reflective layer 10 arranged between the electro-optical structure 4 and the substrate 2 in the exemplary embodiment shown in FIG. 7A has light-scattering structures 7 in the form of small crystallites, particles or inclusions which at least partially scatter the light passing through the layer 10.
• the particles or inclusions have, for example, a different refractive index than the remaining layer 10, or the material surrounding the particles.
• the size of the particles is of the same order of magnitude or smaller than the light wavelength to which the anti-reflective layer 10 is adapted. Particles or inclusions of this size achieve particularly effective light scattering.
• FIG. 7B shows an embodiment of the invention with 'three-layer antireflection coating 10, as they have approximately the embodiments of Fig. 2 to Fig. 4.
• the light scattering structures are in this embodiment present in each of the layers 101, 103, 105 of the anti-reflective layer.
• FIG. 7C also shows an embodiment with a three-layer anti-reflective layer.
• Fig. 2 to Fig. 4 are each a three-layer antireflection '10 / respectively arranged both on the side 22 of the substrate, as well as on the opposite side 21 8.
• the light scattering structures are in the one shown in Fig. 7C
• the light-scattering structures can, however, also be arranged in another layer or in two layers of the anti-reflective layers 8, 10.
• FIG. 7D shows yet another exemplary embodiment with an anti-reflective layer 10 with light-scattering structures 7.
• the interface - between the substrate and the anti-reflective layer 10 is structured.
• the anti-reflective layer is applied to the structured side 21 of the substrate, so that the anti-reflective layer 2 has light-scattering structures 7 at its interface with the substrate.
• the anti-reflective layer is applied in particular to the side 22 of the substrate 2 provided with regular structures in the form of regular projections, so that correspondingly regular light-scattering structures 7 result at the interface.
• the surface 22 can also be simply roughened using a suitable method, for example by etching, so that the light-scattering structures are irregular.
• the light-scattering structures can also be applied in an additional layer 11 on the side 22 of the substrate 2.
• the refractive index of the matrix of this layer 11 arranged on the substrate 2 can advantageously be chosen such that it matches the refractive index of the substrate 2 as closely as possible. In this case, the layer has no refracting and reflecting effect at the interface with the substrate when the substrate is in contact, but only 'scattering effect and is not part of the Entspiegungstik.
• FIGS. 8A to 8C show ray tracing simulations for different layer arrangements of organic electro-optical elements.
• the graphs of FIGS. 8A to 8C each show the viewing side of an organic electro-optical element 1.
• Each point of the graph represents a light beam that has emerged, a point-shaped radiation source in the active one
• Fig. 8B is a result of simulation for a like 'shown in FIG. 1 arrangement of the invention, but shown without lichstreuende structures.
• FIG. 8C finally shows a simulation for an embodiment according to the invention as shown in FIG. 1 with additional light-scattering structures, corresponding to the one in FIG.
• Fig. 7A illustrated embodiment.
• Layer thicknesses and refractive indices correspond to the simulation on which FIG. 8B is based.
• the external quantum efficiency increases here by introducing the light-scattering
• FIG. 9 shows an example of an inventive anti-reflective optical component in the form of a lens shown in "cross-section 70.
• the lens may, for example, a spectacle lens or a lens may be a lens..
• both refractive surfaces 72, 73 of the substrate 71 of the lens 70 are coated with anti-reflective layers 8 or 10 according to the invention, which are formed in the same way as the anti-reflective layers of the electro-optical elements according to the examples described above.
• the thicknesses and refractive indices can be optimized to a wavelength of the visible spectrum, preferably the mean wavelength of the visible spectrum.
• each of the anti-reflective layers 8, 10 can again have an optical thickness which is at least 3/8, preferably at least 1/2 times the wavelength from the spectrum.
• FIG. 10 shows a further example of an optical component, here an optical filter 75 in cross section.
• the inlet surface 77 and outlet surface 78 of the transparent substrate 76 are each provided with anti-reflective layers 8 or 10 according to the invention.
• the layer thickness of the at least one layer of the anti-reflective layer it is advisable to adapt the layer thickness of the at least one layer of the anti-reflective layer to the smallest possible integral reflectivity for a wavelength of the filtered spectrum.
• the filtered spectrum for example, the
• the substrate 76 can also, for example, be a disk, such as a window, especially architectural glass windows for aircraft, ships or 'vehicles. In this case, it makes sense to use a layer thickness of the at least one layer of the anti-reflective layer, which with regard to its integral reflectivity for the central wavelength of the optical spectrum, or that with the
• FIG. 11 shows an example of a lighting fixture equipped with anti-reflective coatings according to the invention.
• the lighting fixture is a fluorescent tube 90 with a tubular glass substrate 91, which encloses a gas discharge space 92.
• Both the inner surface 93 and the outer surface of the substrate are equipped with anti-reflective layers 8, 10 optimized according to the invention for minimal integral reflectivity, for example for the weighted average of the fluorescence spectrum.

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• 2004
  • 2004-04-22 DE DE102004020245A patent/DE102004020245A1/de not_active Withdrawn
• 2005
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  • 2005-04-22 EP EP05738415A patent/EP1738423A1/de active Pending
  • 2005-04-22 WO PCT/EP2005/004356 patent/WO2005104261A1/de active Application Filing
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