BE1020675A3 - ORGANIC PHOTONIC DEVICE - Google Patents

Description

Organic photonic device

The present invention relates to photonic devices, in particular organic photonic devices. By photonic device is meant any type of device that can emit light. Such devices are, for example, optoelectronic devices such as organic electroluminescent devices known by the acronym OLED (Organic Light Emitting Device).

Organic electroluminescent devices generally comprise a substrate, an electrode disposed on the substrate to provide charges of a first polarity, an electrode disposed on the other side of the device to provide charges of a second polarity opposite to the first, charge-carrying semiconductor organic layers and electroluminescent layers disposed between the electrodes, and an encapsulation system. OLEDs can be used for lighting, whether architectural or decorative, backlighting, or for signage. OLEDs emitting in white are generally preferred for these applications.

In order to manufacture a white emitting OLED device for lighting applications, it is advantageous to make a light source with the highest color rendering or CRI (Color Rendering Index) possible. and to limit the angular dependence of the polychromatic emission spectrum of said device by ensuring a low color variability according to the viewing angle (color Delta).

The Color Rendering Index (CRI) is a quantitative measure of the ability of a light source to faithfully reproduce the colors of different objects in comparison with an ideal or natural light source. Light sources with a high CRI are desirable in most lighting applications because they improve the perception of color shades of illuminated objects. The color rendering index is defined by the International Commission on Illumination as the effect of an illuminant on the chromatic aspect of the objects it illuminates, this aspect being compared consciously or not with that of the same illuminated objects. by a reference illuminant, as defined in the following works: "CIE 17.4-1987

International Lighting Vocabulary "or Nickerson, Dorothy, Jerome, Charles W. (April 1965)," Color Rendering of light sources: CIE method of specification and its application, "llluminating Engineering (IESNA) 60 (4): 262-271.

The color Delta combines the color variation along the Planck locus and orthogonally to it. The Planck locus groups the emission points of the different Planckian sources and is therefore close to the majority of standard white sources (for example, the illuminants D65, C, A). For devices emitting white or near-white light, it is therefore advisable to penalize the orthogonal hue differences with respect to this curve of the Planck locus more strongly as they move away from the white.

The delta of color is thus represented, by the following formula:

in which - n is the number of experimental data (with n> 5, distributed in a range of 0 to 60 °).

p (x) is a cubic approximation of the Planck locus and the choice of the two scale constants imply that variations parallel to the Planck locus are penalized 2.5 times less than orthogonal variations at the Planck locus. This choice favors angular paths close to the Planck locus compared to other angular paths.

- X, and y, are the chromatic coordinates in the CIE 1931 system, at each angle i.

It is known for OLEDs to use indium tin oxide (ITO: Indium Tin Oxide), aluminum doped zinc oxide (AZO) or other layers as a transparent electrode. conductive multilayers, for example, a fluorine doped tin oxide layer or a dielectric / metal / dielectric layer (multilayer) layer assembly, for example comprising at least one silver-based metal layer, similar to those used in glass pilings for the thermal management of buildings, trains or automobiles.

It is also known that each of these electrodes has its advantages and defects. For example, multilayers including at least one silver-based layer may be sometimes preferred because they substantially improve conduction properties compared to ITO layers for reasonable electrode thicknesses. Conductive structures comprising two silver layers may also sometimes be preferred to limit problems of angular stability of the emitted color. But in practice, ΓΙΤΟ remains for the moment always the most used electrode, preferred to dielectric / metal / dielectric multilayers.

As for the organic part of the OLED, it is the "traditional performing organic stacks" which are more and more generally used. By "conventional performance organic stacking" is meant that the organic part of the device is chosen "thick", that is to say that at least two of the different emitting sources (red, green, blue, yellow) are separated. from one another by an organic separation layer. Conventionally, G represents the organic emitting layer emitting predominantly green light, B represents the organic emitting layer emitting predominantly blue light and R represents the organic emitting layer emitting predominantly red light. The order of these emitting layers is usually "RGB" sequence expressed relative to the transparent electrode, the first letter of the sequence corresponding to the emitter layer furthest from said electrode.

Now it has become apparent to us that, surprisingly, it is not only by changing the nature of the electrode that OLED devices with the best possible combination of a high CRI, a luminance high, and low color variability depending on the angle of view, but that one could also play on these parameters by changing the order of the emitting layers within the OLED system itself.

The objective of the present invention is the selection of organic systems of "conventional high performance organic stack" type for obtaining for OLED devices incorporating them, the best possible combination of a high CRI, a high luminance (c '). that is, a high amount of emitted light, a high efficiency), and a low color variability depending on the viewing angle (color Delta).

According to one of its aspects, the present invention relates to an organic electroluminescent device according to claim 1, the dependent claims having preferred embodiments.

An organic electroluminescent device comprises (i) a transparent substrate comprising an electrode carrier, and (ii) an OLED system emitting white light, adjacent to the transparent substrate electrode, comprising a succession of at least three emitter layers, one emitting in green, one in blue and one in red, of which at least two are separated from each other by an organic separation layer. It is characterized by the fact that, among these three emitting layers, the emitting layer furthest from the electrode is that emitting in the green and the emitting layer closest to the electrode is that emitting in the red.

Such devices have the advantage of offering an excellent compromise between a high CRI, a high luminance, and a low color variability depending on the viewing angle, and although organic electroluminescent devices exist offering for one of these properties With better results, we found that this particular sequence of "GBR" transmitting layers offered both high CRI, high luminance, and low color Delta, or better color stability at angle.

The substrate of the present invention is said to be transparent, that is to say that it has a light absorption of at most 50%, or even at most 30%, preferably at most 20% or at most 15%. %, more preferably at most 12% or at most 10% in the wavelength range of visible light. The substrate of the present invention comprises a support and an electrode.

The support preferably has a refractive index of at least 1.2.1.4 or 1.5 at a wavelength of 550 nm. This makes it possible, with an equal substrate structure, to increase the quantity of light transmitted or emitted.

The term "support" is intended to denote not only the support as such but also any structure comprising the support and at least one layer of a material having a refractive index, a material, close to the refractive index. of the support, nsupport, in other words | nsupport-rWéiïaul ^ 0,1, I nSUpp0rt-nmaterial I representing the absolute value of the difference between the refractive indices. There may be mentioned as an example a silicon oxide layer deposited on a soda-lime-silica glass support.

The support can include additional devices that promote the extraction of light on one or the other of its faces. One of these devices, namely a diffusion layer, is described in published documents WO2009 / 017035, WO2009 / 116531, WO2010 / 084922, WO2010 / 084925, WO2011 / 046156, WO2011 / 046190 and PCT / JP2011 / 074358, all incorporated herein by reference. Generally, this diffusion layer has a thickness of more than 5 μm and is not considered a coherent optical system. In the case where such a diffusion layer is in contact with the electrode according to the invention, nSupport is then considered to be the index, possibly of the matrix, of this diffusion layer.

Alternatively, it may be desirable to avoid or minimize the diffusion of the support. The substrate according to the invention can thus display a haze value of less than 20%, more preferably less than 10%, or even more preferably less than 2% or 1%. The advantage is that the organic device including such a substrate has an attractive appearance and non-milky when off. A mirror aesthetic may, for example, be obtained if the second opposite charge electrode is reflective; or it is possible to make a transparent glazing assembly if the second electrode is also semi-transparent.

In the case of a second reflecting electrode, the complete organic device can then have a light reflection (according to CIE, illuminant D65 2 °) measured on the support side of more than 20%, or more preferably of more than 40% or even more advantageously more than 60%. In the case of a second semi-transparent electrode, the complete organic device can then have a light transmission of at least 5% (according to CIE, illuminant D65 2 °), or more advantageously at least 10% or more preferably at least 20%.

The function of the support is to support and / or protect the electrode. The support may be made of glass, rigid plastics material (for example: organic glass, polycarbonate) or flexible polymeric films (for example: PVC, PET, PP, PTFE). The support is preferably rigid. Alternatively, it can be rolled on itself (for example an extra-fine flexible glass that can be used in a "roll to roll" deposition process).

When the support is made of glass, for example a glass sheet, the latter preferably has a geometrical thickness of at least 0.05 mm. The glass is preferably clear or colored in the mass or in the form of silico-soda-lime. area. Advantageously, it can be extra-clear, that is to say a glass with a total iron content, expressed as Fe 2 O 3, of less than 0.020% by weight, preferably less than 0.015% by weight. The glass, because of its low porosity, has the advantage of providing good protection against any form of contamination of a device comprising the transparent substrate according to the invention.

In certain particular embodiments, the support carries a functional coating located on the face opposite to the face on which the electrode is deposited. This functional coating may be a layer or stack of several functional layers, for example, antireflection, diffusing, anti-fogging, anti-fouling, anti-scrape or selective absorbent.

The electrode according to the invention may comprise or consist essentially of a tin-doped indium oxide (ITO) layer, a doped aluminum oxide (AZO) or gallium-doped (GZO) zinc oxide layer, or a layer of tin oxide doped with fluorine. Preferably, the electrode consists essentially of a tin-doped indium oxide layer; this may advantageously have a thickness of at least 50 nm, preferably at least 75 nm, and / or at most 500 nm or 400 nm, preferably at most 350 nm or 300 nm, more preferably 250 nm or less. The electrode can behave as an anode or, on the contrary, as a cathode.

Alternatively, the electrode may be formed of a conductive multilayer, comprising at least one conductive metal layer surrounded by dielectric layers.

The conduction metal layers of the electrode may be one, two or three. They mainly provide the electrical conduction of said electrode. They comprise at least one layer comprising a metal or a mixture of metals. The metal and / or the mixture of metals preferably comprises at least one element selected from Ag, Au, Pd, Pt, Al, Cu, Zn, Cd, In, Si, Zr, Mo, Ni, Cr, Mg, Mn, Co, Sn. Preferably, the metal and / or the mixture of metals comprises at least one element selected from Ag, Au, Cu, Al. More preferentially, the conductive metal layer comprises at least silver in pure form or in combination with another metal. preferably selected from Pd and Au. The geometrical thickness of the conductive metal layers is at least 6 nm, preferably at least 7 nm, more preferably at least 8 nm. Preferably, the geometric thickness of the conductive metal layers is at most 25 nm, preferably at most 20 nm.

The dielectric layers may comprise one or more sublayers of different natures. Advantageously, they comprise a compound having a refractive index at a wavelength of 550 nm of at least 1.6, at least 1.8 or at least 1.9, and / or at most 2.7 or at most 2.5.

Preferably, they have a refractive index which is greater than that of the support by at least 0.1, preferably at least 0.2. Preferably, the dielectric layers comprise at least one compound selected from: - oxides of at least one element selected from Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Zn, Al, Ga, In, Si, Ge, Sn, Sb and Bi, as well as mixtures of at least two of them; silicon nitride, silicon oxynitride, silicon oxycarbide, silicon oxycarbonitride, aluminum nitride, aluminum oxynitride and mixtures of at least two of them.

More preferably still, they comprise at least one compound selected from zinc oxides, tin oxides, titanium oxides, aluminum nitrides, silicon nitrides, and mixtures of at least two of them. , zinc-tin mixed oxides and titanium-zirconium-yttrium mixed oxides. The geometric thickness of the dielectric layers is at least 20 nm or at least 30 nm, more preferably at least 55 nm. Preferably, it is less than 100 nm or 90 nm, preferably less than 80 nm. In preferred embodiments of the invention, the last dielectric layer of the electrode, the one farthest from the support has a geometric thickness of at least 5 nm or at least 8 nm, more preferably at least 10 nm. and / or less than 50 nm or 40 nm, preferably less than 30 nm or 25 nm, more preferably less than 22 nm, 20 nm or 18 nm.

In general, when geometric thickness values are given here for the dielectric layers of the electrode, they are for a constituent material having a refractive index between 1.8 and 2.2, more preferably between 1.9 and 2.1 or even more preferentially. between 1.95 and 2.05 at a wavelength of 550 nm. They therefore correspond to an optical thickness equal to the geometrical thickness multiplied by this refractive index which is close to 2. If another choice of material is made, with a different refractive index, it is sufficient to recalculate a corresponding geometrical thickness.

Alternatively, the electrode may comprise or consist essentially of a transparent conductive polymer, for example PEDOT: PSS, or silver nano-wires, for example a ClearOhm ™ film from CAMBRIOS.

The organic electroluminescent device according to the invention further comprises a system of organic electroluminescent layers (OLED system) emitting a white light, adjacent to the electrode of the transparent substrate.

For an OLED system to emit white light, it can include, and this is the case in the present invention, a stack of three organic layer structures corresponding to the red, green and blue light emitting portions. In the present case, the organic emitting layers are separated by one or more organic separation layers (for example: charge transport layers); these structures are called "traditional performance organic stacks".

The organic layers may consist of a single material layer or a plurality of layers each of a different material. It is also possible to use systems with four emitting layers where the yellow color (represented by the letter Y) makes it possible to extend the spectral coverage of the visible light of the OLED system.

The term "white light" is intended to designate a light whose chromatic coordinates at 0 °, for a radiation perpendicular to the surface of the substrate, are included in one of the eight quadrilaterals of chromaticity, including the contours of the quadrilaterals. These quadrilaterals are defined on pages 10 to 12 of the standard ANSI_NEMA_ANSLG C78.377-2008. These quadrilaterals are represented in FIG. A1, entitled "Graphical representation of the chromaticity specification of SSL products in Table 1, on the CIE (x, y) chromaticity diagram".

Preferably, the organic separation layer (s), separating at least two of the different emitting layers, has a thickness of at least 5 nm, more preferably at least 15 nm, or even more preferably at least 30 nm. nm.

Materials making it possible to manufacture an OLED system according to the invention are described for example in Reineke et al. (NATURE, Vol 459, 14 May 2009) or in Rosenow et al. (Journal of Applied Physics, Vol 108, 11313 (2010).

According to a particular embodiment, the organic electroluminescent device is integrated in a glazing unit, a double glazing unit or a laminated glazing unit. It is also possible to integrate several electroluminescent organic devices.

According to another particular embodiment, the organic electroluminescent device is enclosed in at least one encapsulating material made of glass and / or plastic. The different embodiments of organic electroluminescent devices can be combined.

Finally, the various organic electroluminescent devices have a wide field of use. The invention is particularly directed to the possible uses of these organic electroluminescent devices for producing one or more light surfaces. The term illuminated surface includes, for example, illuminating slabs, illuminated panels, light partitions, worktops, greenhouses, flashlights, wallpapers, drawer bottoms, illuminated roofs, touch screens, lamps, photo flashes, illuminated backgrounds. display, safety signs, shelves, car or airplane cockpit lights.

The organic electroluminescent devices according to the invention may advantageously have, in combination: a CRI greater than 60, preferably greater than 70, a color Delta less than 2.4, preferably less than 2.0 or 1.8.

The organic electroluminescent devices according to the invention can also advantageously have an efficiency greater than 15 lumen / watt at a luminance of 10,000 cd / m 2.

In general, the present description has focused on "bottom-emission" OLEDs, but the same principles apply for OLEDs of the "top-emission" type.

Particular embodiments of the invention will now be described, as examples, while referring to Figure 1 and Examples 1 and 2. Comparative Examples 1 and 2, not forming part of the invention are also presented.

Fig. 1: cross section of an organic electroluminescent device according to the invention

The organic electroluminescent device (100) of FIG. 1 comprises a transparent substrate (1), a system, OLED (2) and a counter-electrode (3), the transparent substrate (1) comprising a carrier (10) carrying an electrode (11). The OLED system (2) comprises, in order from the medium (10), a first organic layer (OD4) including a hole transport layer, a red emitter layer (EMR), a second organic layer (OD3) including an electron transport layer and a hole transport layer, a blue emitting layer (EMB), a third organic layer (OD2) including an electron transport layer and a hole transport layer, an emitting layer green (EMG), and a fourth organic layer (OD1) including an electron transport layer. This OLED system is called "GBR". One or more blocking layer (s) (not shown in FIG. 1) may also be provided in the OLED system in one or more charge transport layer (s).

The different elements of the figures are not represented on the scale.

Examples of organic electroluminescent devices according to the invention as well as comparative examples not forming part of the invention are shown in Table I.

For each part of the organic electroluminescent device, the layer (s) forming the electrode and the organic system are described therein: their nature and their geometrical thickness expressed in nanometers.

Zn90Sn10O represents a mixed oxide of Zn (90% weight) and Sn (10% by weight)

Zn48Sn520 represents a mixed oxide of Zn (48% weight) and Sn (52% weight)

TxO represents a layer of TiO2 deposited by magnetron sputtering from a ceramic target ITO represents a layer of tin doped indium oxide

All the organic electroluminescent devices of the examples and comparative examples have a sodo-silico-calcic glass support with a refractive index of about 1.5.

The performance of organic electroluminescent devices of the Examples and Comparative Examples are given in Table I.

The performance of Example 1 and Comparative Example 1 were measured on fabricated samples, while the performance of Example 2 and Comparative Example 2 were calculated using the SETFOS (Semiconducting Emissive Thin Film Opti- firm Fluxim (http://www.fluxim.ch), version 2.

The luminance is expressed in arbitrary units. Only the luminances of Example 1 and Comparative Example 1 can be compared with each other and those of Examples 2 and Comparative Example 2 with each other, the same scale having not been used in both cases (1 and 2). The given CRI values are CRI averages calculated at angles of 0, 10, 20, ..., 80 degrees according to the formula above. Delta color values (Deltacol) were also calculated according to the formula given above.

The performances of the examples certainly show a lower luminance in the "GBR" cases than in the "RGB" cases, but an improved CRI and Delta of color (higher CRI, lower color Delta). The "GBR" stacks thus offer an excellent combination of luminance, CRI and color Delta values, with a CRI greater than 75 and a color Delta of less than 1.6.

In addition, "uncoupling" or "light extraction", organic electroluminescent devices manufactured according to Example 1 and Comparative Example 1 were measured Despite a lower luminance, the GBR system offers better outcoupling than the RGB system. Without being bound by the theory, this phenomenon, quite unexpected, could be explained by the fact that the variability of the luminance and outcoupling values between the different colors of the visible spectrum is less marked in the GBR system than RGB. In other words, a GBR system coupled to a conventional light extraction device works better because the spectrum of GBR devices is less sensitive to dispersion, especially in the red, so the color and extraction in white are better.

Claims (22)

An organic electroluminescent device (100) comprising (i) a transparent substrate (1) comprising a carrier (10) carrying an electrode (11), and (ii) an OLED system (2) emitting a white light, adjacent to the electrode (11) of the transparent substrate (1), comprising a succession of at least three emitting layers, one emitting in the green (EMG), one in the blue (EMB) and one in the red (EMR), among which at least two are separated from each other by an organic separation layer (OD2, OD3), characterized in that, among these three emitter layers, the emitting layer furthest from the electrode (11) is that emitting in the green (EMG) and the emitting layer closest to the electrode (11) is that emitting in the red (EMR). 2. Organic electroluminescent device according to claim 1, characterized in that it comprises no more than three emitter layers. 3. Organic electroluminescent device according to claim 1, characterized in that it further comprises a emitting layer emitting in the yolk. 4. Organic electroluminescent device according to one of the preceding claims, characterized in that each emitter layer is separated from another emitter layer by an organic separation layer (OD2, OD3). 5. Organic electroluminescent device according to one of the preceding claims, characterized in that the at least one organic separation layer (OD2, OD3) has a geometric thickness of at least 5 nm, preferably at least 15 nm. 6. Organic electroluminescent device according to one of the preceding claims, characterized in that the electrode (11) consists essentially tin-doped indium oxide. 7. Organic electroluminescent device according to the preceding claim, characterized in that the electrode (11) has a geometric thickness of at most 350 nm. 8. organic electroluminescent device according to one of claims 1 to 5, characterized in that the electrode (11) consists essentially of a multilayer comprising at least one layer based on silver. 9. Organic electroluminescent device according to the preceding claim, characterized in that the at least one silver-based layer has a geometric thickness of at least 6 nm and at most 25 nm. 10. Organic electroluminescent device according to one of the preceding claims, characterized in that it has a CRI greater than 60 and a color Delta less than 2.4.