EP2311093A2 - Polychromatic electronic display device with electroluminescent screen - Google Patents

Abstract

The invention relates to a polychromatic electronic display device with an electroluminescent screen, particularly with organic light-emitting diodes (OLEDs), wherein the polychromatic electronic display device comprises an electroluminescent emission surface and, towards the inside of the device, at least one substrate (2) coated with a pixel matrix, said device including a stack of a plurality of electroluminescent cells (U_I and U_e) in which each pixel comprises at least three sub-pixels having different colours. According to the invention, for each pixel, the sub-pixel having the lowest emission wavelength λ_c, or critical sub-pixel, is exclusively located in the external unit (U_e) adjacent to said emission surface, each of the other sub-pixels emitting at a wavelength higher than λ_c being exclusively located in an internal unit (U_I) relative to said external unit and adjacent to the substrate, the surface area of this critical sub-pixel being higher than that of each of the other sub-pixels.

Description

 SCREEN POLYCHROME ELECTRONIC DISPLAY DEVICE

ELECTROLUMINESCENT.

The present invention relates to a polychromatic electronic display device with electroluminescent screen. The invention applies in particular to organic light-emitting diode ("OLED") screens.

In known manner, the display devices using "OLEDs" comprise a transmission zone formed of a matrix of pixels, each pixel typically consisting of several subpixels of different colors (RGB: red, green and blue in color). general), and an electrical connection area arranged adjacent to this active area. Each pixel of this "OLED" matrix usually incorporates a multilayer light-emitting structure comprising an organic film interposed between two lower and upper electrodes which serve as anode and cathode, and one of which is transparent or semi-transparent to light. emitted while the other is generally reflective.

To produce these screens, organic layers are deposited at each sub-pixel (a type of layer or stack of layers by color) by means of a stencil or "shadow mask". The minimum dimension of the openings of this stencil therefore defines a minimum size for these sub-pixels. This minimum size for each sub-pixel can also be imposed by the dimensions of the addressing circuit used for the power supply of each sub-pixel, via the aforementioned connection area. It has therefore been sought to increase the resolution of the screens by playing on one of these two parameters, i.e. the size of the openings of the stencil or, if it is the limiting factor, that of the addressing circuit.

Other ways of improving the resolution of such screens have been explored in the past, consisting of stacks of "OLED" units. In this type of screen, certain sub-pixels and their corresponding transmitting structures are located in an so-called external "OLED" unit, adjacent to the transmitting face, while others are located in a so-called internal "OLED" unit, adjacent to the substrate, an electrode of the pixel thus formed can be common to two superposed units.

In addition, it has been sought in these stacks to minimize the current density flowing in the sub-pixel which is the most sensitive to aging - the one whose wavelength is the smallest, typically the blue in the RGB case - giving priority to its emission surface at the expense of that of the other sub-pixels, so as to increase the lifetime of this critical sub-pixel and therefore of the entire device. For example, document US Pat. No. 6,747,618, which has in FIG. 8 such a stack with the two red and green subpixels located in the external unit, and the blue subpixel located in the internal unit with an emission area greater than the sum of the areas of the red and green subpixels. Reference may also be made to US-B-7,250,722, which describes a stack in which the red and blue subpixels are located in the same internal or external unit and the green sub-pixel in the other unit, always ensuring the emission area of the blue subpixel is greater than that of the other subpixels to increase its lifetime.

A major disadvantage of the stacks of "OLED" units presented in these documents is that the gain in lifetime that they provide in each pixel for the critical sub-pixel (typically blue), by maximizing the area of its structure transmitter, does not optimize the resolution of the screen, which is limited by the stencil used for the deposition of sub-pixels of smaller dimensions. Another disadvantage of known stacks where the critical subpixels (eg blue) are located in the internal "OLED" unit is that the photons they emit are reabsorbed by the emitting structures of the other sub-pixels in the unit " OLED "external, which results in a loss of flux for these photons on the emission side of the screen. An object of the present invention is to provide a polychromatic display device comprising an electroluminescent emission face and, towards the inside of the device, at least one substrate coated with a matrix of pixels, this device comprising a stack of electroluminescent units where each pixel consists of at least three sub-pixels of different colors, a device that overcomes these disadvantages.

For this purpose, a device according to the invention is such that, for each pixel, the sub-pixel of the lowest transmission wavelength λ _c , or critical sub-pixel, is exclusively located in that of the units, or external unit, which is adjacent to this transmitting face, each other sub-pixel emitting at a wavelength greater than λ _c being exclusively located in a unit which is internal with respect to this external unit and which is adjacent to the substrate (as opposed to the external unit which is distal to this substrate), the area of this critical sub-pixel being greater than that of each other sub-pixel.

It will be noted that this arrangement of the sub-pixels within the stack of light-emitting units according to the invention makes it possible to gain both resolution and life time for the matrix of pixels obtained. In particular, it is possible to provide an identical visual luminance (in cd / m ² ) for each of these sub-pixels, among which the critical sub-pixel (of the lowest wavelength, for example of blue color in the case RGB, indigo or violet) can have, without any dimensional limitation, a much larger emission area than that of each other sub-pixel underlying, which results in a lifetime that can be very significantly increased for the device. display.

In addition, the sub-pixels of smaller dimensions (red and green in the RGB case) are located directly on the substrate, thus allowing the use of conventional technologies of microelectronics for their manufacture and thus the realization of smaller patterns. sizes (hence the gain in resolution).

Preferably, the area A of this critical subpixel is at least equal to the sum of those of the other subpixels (ie A _b ι _e u ≥ A _r0U ge + A _ve rt). which makes it possible to gain even more resolution and longer life for the screen. Even more preferably, the critical subpixel can extend beyond (ie in excess of) the edges of all the other sub-pixels underlying.

It will also be noted that the location of the critical sub-pixels in the unit turned on the side of the transmission face makes it possible to avoid, within each pixel, the aforementioned phenomenon of loss of luminous flux emitted by the critical sub-pixel .

Advantageously, the critical sub-pixel can be activatable independently of each other sub-pixel: it is transparent when it is not activated and, when it is activated, transmits at said wavelength λ _c by adding if necessary the radiation emitted by each other sub-pixel.

According to another characteristic of the invention, each pixel advantageously comprises organic structures emitting radiation, such as organic light-emitting diodes ("OLEDs"), which respectively form the sub-pixels and which are each interposed between and in electrical contact with two electrodes respectively serving as anode and cathode for the corresponding emitting structure, one of these electrodes being transparent or semitransparent and the other electrode being reflective. Preferably, said stack consists of two electroluminescent units respectively external and internal, said critical sub-pixel emitting within said external unit and being stacked on the other sub-pixels that all emit within said internal unit.

According to a first embodiment of the invention, this display device comprises a single active or passive matrix type substrate, each pixel being delimited by an external electrode applied to the emitting structure of said critical sub-pixel, or critical structure. , and by several internal electrodes which are applied on this substrate and on which the emitting structures of the other sub-pixels, or non-critical structures, are deposited spaced apart, at least one intermediate electrode being applied to the non-critical structures and / or under the critical structure. According to this first mode, this device may comprise a single intermediate electrode which is applied at a time, for each pixel, under said critical structure and on said non-critical structures with which this critical structure is substantially aligned. As a variant, the device according to this first embodiment may comprise two external and internal intermediate electrodes which are superimposed by being separated by at least one electrically insulating and transparent inorganic layer, preferably deposited by the "ALD" technique for depositing an atomic layer (" atomic layer deposition "in English) and made of a material selected from the group consisting of oxides of aluminum, silicon, zinc and silicon nitrides, these intermediate electrodes being respectively applied, for each pixel, under the critical structure and on all non-critical structures. In this variant, the internal electrodes and the external intermediate electrode may each form a (semi) transparent anode, and the inner intermediate electrode and the outer electrode may then each form a reflective cathode. The thickness of this layer can be optimized by simulation to allow the extraction of the maximum luminous flux of the internal and external units. In this case we find for each electroluminescent unit the preferred arrangement of an emitting structure interposed between a lower anode and an upper cathode.

It will be noted that the aforementioned transparent inorganic material which forms the insulating layer used in this variant could also be used for the encapsulation of the screen according to the invention.

According to a second embodiment of the invention, the display device comprises two respectively external and internal substrates which are each active or passive matrix and which are assembled to one another at their peripheries by adhesive strings. forming a sealed encapsulation for the device, the external substrate being provided with regularly spaced critical emitting structures which each form a critical subpixel, and the inner substrate being provided with non-transmitting structures regularly spaced critics which each form at least one of the other sub-pixels and which are separated from these critical structures by an electrical insulator, the two matrices formed by these substrates being connected to independent power supply circuits. It should be noted that the use of these two substrates on which the emitting structures are deposited does not really complicate the manufacturing process of the display device according to the invention, since it is not necessary in this second mode of to precisely align the critical and non-critical emitting structures deposited opposite, and especially that the encapsulation of the screen is performed by the aforementioned adhesive strands forming a hermetic enclosure.

This device also provides a very high resolution and less destructive operating modes for the electroluminescent units, as will be explained later. In accordance with this second mode, said insulator consists of a vacuum separating these critical and non-critical structures, so as to overcome the efficiency limitations of each critical sub-pixel by controlling the light interferences between these structures.

Advantageously according to this second mode, said substrates are separated from each other by a distance of less than 2 μm, to minimize the emissions of a non-critical structure towards a neighboring non-critical structure and to maximize them towards the critical structure vis-à-vis .

According to another general characteristic of the invention, said sub-pixels may for example consist of three sub-pixels respectively red, green and blue, said critical sub-pixel located exclusively in said external unit being a sub-pixel emitting in the blue, and the other sub-pixels exclusively located in said internal unit being sub-pixels emitting in the red and / or in the green.

According to another feature of the invention particularly common to these first and second modes, the transmitting structure of each of the sub-pixels other than said critical sub-pixel is able to selectively transmit, depending on the voltage applied to it, at at least two distinct radiations of wavelengths both greater than that of this critical sub-pixel so as to successively form at least two-color non-critical subpixels.

In the aforementioned example of sub-pixels emitting in blue, red and green, the emitting structure of each non-critical sub-pixel can then comprise two different emitting materials capable of emitting in the low-voltage red and in the green at higher voltage, for obtaining two-color sub-pixels.

It will be noted that these non-critical sub-pixels, which are at least two-colored, have the advantage, in this first embodiment of the invention, of simplifying the addressing of the electroluminescent units by requiring two fewer internal electrodes for the corresponding electroluminescent units and, in this second embodiment of the invention, also to simplify the structure of the internal substrate. In general, for all the display devices according to the present invention, it should be noted that they can be sealed encapsulated by various means, including:

- For the first embodiment of the invention, the bonding of a transparent protection plate for example of glass or plastic and provided with colored optical filters on its assembly face with the screen, or the recovery of the screen with one or more encapsulation layers capable of being formed of the above-mentioned transparent inorganic material, and

- For the second embodiment of the invention, by the beads of adhesive deposited between the two substrates and forming the aforementioned hermetic enclosure.

Other advantages, characteristics and details of the invention will emerge from the additional description which follows with reference to the accompanying drawings, given solely by way of example and in which: FIG. 1 is a diagrammatic view from above of a arrangement according to the prior art of three respectively red, green and blue subpixels of a light-emitting screen, FIG. 2 is a schematic view from above of an arrangement according to the principle of the invention of these three sub-pixels, distributed in two superimposed units of a light-emitting screen, FIG. 3 is a partial diagrammatic cross-sectional view of a display device according to the first embodiment of the invention using the stacking principle of FIG. 2, FIG. 4 is a schematic view from above of the essential components of the stack of a display device. according to a variant of Figure 3, and Figure 5 is a partial schematic cross-sectional view of a display device according to the second embodiment of the invention.

The display devices 1, 1 ', 101 according to the invention described hereinafter with reference to FIGS. 2 to 5 are of the "OLED" type, comprising in known manner at least one substrate 2, 102a, 102b, typically in silicon coated with a matrix of pixels which overcomes an integrated circuit structure for addressing each pixel and which may comprise for example for each pixel two transistors and a capacitor or more complex circuits, and which is connected to an electrical connection zone ( not shown) for the establishment of a potential difference between electrodes 3 to 6 in contact with which are interlaced multilayer emitting structures organic film (monolayer or multilayer, not shown). As will be explained below, these electrodes 3 to 6 each serve as anode or cathode and at least one of them is transparent to the light emitted by the pixels in order to radiate this light emitted towards the external device 1, the, 101. As for the organic film inserted between these electrodes 3 to 6, it is designed to transfer the electrons and holes that come from the electrodes 3 to 6 and which are recombined to generate excitons and therefore the light emission.

FIG. 1 shows a known arrangement of three sub-pixels R, V, B (respectively red, green and blue) for each pixel of an "OLED" screen matrix, in which an attempt has been made to maximize the size of the shortest wavelength subpixel B at the expense of that of the subpixel R and the subpixel V, which have been reduced with the dimensional limit I imposed by the size of the openings of the stencil used to deposit these sub-pixels and / or that of the addressing circuit for the supply of each sub-pixel. In this way, the current density in the subpixel B, which is known to be the most sensitive to aging, has been minimized, so as to increase the lifetime of this sub-pixel B of the highest transmission area. high, and we obtained a pixel of dimension L in the direction of the succession of the three sub-pixels R, V and B.

Is illustrated in Figure 2 the general principle of the invention using a stack of two units "OLED" respectively internal (ie opposite to the transmitting face of the screen) and external (ie adjacent to this emission face) where, for each pixel, the blue sub-pixel B 'is only located in the external unit and the red sub-pixels R and green V are only located in the internal unit, with a transmission area for the sub-pixel. pixel B 'which is equal to or greater than the sum of the respective emission areas of the other two sub-pixels R and V. It can be seen in FIG. 2 that this sub-pixel B' advantageously exceeds on each side of the edges of the set of sub-pixels R and V, having a dimension L "reduced compared to the corresponding dimension L of Figure 1.

Depending on the desired color, the sub-pixels R ₁ V and B 'can be solicited independently or simultaneously, the superimposed subpixel B' being transparent when it is not activated so as not to alter the emission of the sub-pixels R and V in this case. Once activated, the sub-pixel B 'emits a radiation which is added, if necessary, to those of the sub-pixels R and V.

This particular arrangement of the sub-pixels R, V and B 'in this stack, combined with the choice of a maximum area for the sub-pixel B' allows both to optimize the life of this blue sub-pixel and to win in resolution. In particular, this location of the sub-pixel B 'on the side of the emission face of the screen makes it possible to keep intact the stream of blue photons, avoiding reabsorption of these latter by the sub-pixels R and V. As an indication, the area of each sub-pixel that can be used in a screen according to the invention can vary from 400 μm ² to approximately 90000 μm ² .

The display device 1 according to the first embodiment of the invention which is illustrated in FIG. 3 comprises a single substrate 2 of active or passive matrix type, each pixel being delimited by:

an external electrode 3 applied to the emitting structure EB of the sub-pixel B 'and forming for example a reflective cathode,

by two internal or bottom electrodes 4 and 5 which are applied on this substrate 2 and on which the emitting structures ER and Ev of the sub-pixels R and V, respectively spaced apart (preferably separated by vacuum), are respectively deposited electrodes 4 and 5 forming, for example, transparent or semi-transparent anodes, and by

an intermediate electrode 6 which overcomes these emitting structures E _R and Ev and on which the emitting structure EB is applied, this electrode 6 forming, for example, both a cathode for the internal "OLED" unit U ₁ and an anode for the external OLED unit U _e .

As can be seen in FIG. 3, the edges of the emitting structure EB are substantially aligned with those of the emitting structure ER and of the emitting structure Ev although, as illustrated in FIG. 4, this alignment can only be approximate for the device the. It may be noted in this regard that this precise alignment is not imperative, whether in terms of colorimetry (insofar as the luminance of the sub-pixels R, V, B 'can be adjusted by the addressing as a function of the desired color and solicited pixels) or in terms of resolution (insofar as the illuminated maximum elementary surface does not exceed the size of the pixel).

In a variant, the display device 1 or the device could comprise not one but two external and internal intermediate electrodes which are superimposed by being separated by an electrically insulating transparent inorganic layer, and which are respectively applied, for each pixel, under the emitting structure E ₆ and on both structures E _R and E _v . This layer, preferably deposited by the "ALD" layer deposition technique atomic, can be advantageously made of a material selected from the group consisting of oxides of aluminum, silicon, zinc and silicon nitrides.

In this stacking configuration, the two inner electrodes and the outer intermediate electrode can each form a transparent or semi-transparent anode, and the inner intermediate electrode and the outer electrode can each then form a reflective cathode, which allows to find for each electroluminescent unit Uj and U _e the preferred arrangement of an emitting structure ER, EV or EB interposed between a lower anode and an upper cathode.

According to another variant of this first mode, the sub-pixels R and V are produced in a single two-color R / V sub-pixel which has the property of transmitting in the low-voltage red and in the higher-voltage green. For this purpose, for each two-color sub-pixel, a multilayer emitter structure composed of at least two distinct materials emitting respectively in red and green, which is for example the following: doped doped anode / HTM014 p / NPB / TMM004 Irppy / TMM004 doped TER04 / Alq3 / N-doped Bphen / cathode, where Alq3 and Bphen materials are available from Aldrich and where other materials are available from Merck Germany.

Note that this variant with two-color sub-pixels R / V simplifies the addressing of each unit "OLED" in comparison with the units of Figures 3 and 4 requiring four independent electrodes.

In general with reference to this first embodiment of the invention, it should be noted that the stack obtained makes it possible specifically to optimize the optical cavity of the blue sub-pixel to increase the optical coupling output, while compromise will be found for the other underlying red and green subpixels, if it is desired to deposit the transport layers in a common way. Also for this first mode of the invention, it should be noted that the or each intermediate electrode must be structured, which is for example achievable by depositing this electrode by means of a conventional stencil.

The device 101 according to the second embodiment of the invention illustrated in FIG. 5 comprises two external 102a and internal 102b active or passive matrix substrates (commonly called "backplanes" in English by those skilled in the art) assembled by cords. 110 glue peripherals forming sealed encapsulation. The outer substrate 102a is provided, on its side facing the other substrate 102b, emitting structures E'B in the regularly spaced blue which each form in contact with a pair of electrodes (not shown) a blue sub-pixel and the inner substrate is provided with regularly spaced emitting structures E ' _R and EV which each form a red and / or green subpixel in contact with a pair of electrodes (not shown) and which are separate from the structures E' _B by vacuum forming electrical insulation. The two matrices formed by these substrates 102a and 102b are respectively connected to independent power supply circuits (not shown). This spatial separation between the emitting structures E ' _B and the emitting structures E'R and EV advantageously makes it possible to overcome the yield limitations of each blue sub-pixel by controlling the light interferences between these structures E'B, E'R and EV

As indicated above, the use of the two substrates 102a and 102b on which are deposited the emitting structures E'B, E'R and EV does not really penalize the manufacture of the device 101, because it is not necessary to to precisely align these structures E ' _B , E' _R and EV and that the encapsulation of the screen is obtained in a very simple manner by the only adhesive beads 110. This device 101 also provides a very high resolution and different modes. less destructive operations for Uj and U _{e units} . Indeed, the spatial separation of the emitting structures of these two units Uj and U _e allows, on the one hand, to overcome performance limitations, particularly noticeable for the E'B emitting structures and, on the other hand, to operate in parallel these very sensitive E'B structures with densities lower current, so with a longer life. Advantageously, the substrates 102a and 102b are separated from one another by a distance of less than 2 μm, to avoid "parallax" errors by minimizing the emissions of a structure E'R OR EV towards a neighboring structure E'R OR EV to focus on the E'B structure vis-à-vis.

Of course, this display device 101 of FIG. 5 requires the connection of power supply circuits (called

"Drivers" in English) specific to the two matrices deposited on the substrates 102a and 102b, i.e. with a number of hoses multiplied by two in comparison with the devices 1, l 'to a single matrix.

As a variant and as indicated above for the first embodiment of the invention, two-color subpixels RA / emitting either in the red or in the green depending on the applied electrical voltage can advantageously be made, in place of the remote arrangement of red and green subpixels on the "backplane" 102b. Such a two-color emitting structure RA / may for example have the following configuration: "backplane" / reflective electrode / p-doped HTL / EBL /

EL green / EL red / HBL / ETL doped n / electrode (semi) transparent, where HTL stands for "hole transport layer", EBL stands for "electron blocking layer", EL stands for "Emissive layer", HBL stands for "hole blocking layer" and ETL stands for "electron transport layer".

As for the emitting structure E'B in blue, it can for example have the following configuration:

"Backplane" / (semi) transparent electrode / HTL doped p / EBL / EL blue / HBL / ETL doped n / electrode (semi) transparent. In the examples mentioned above, it will be noted that the transfer layers (HTL and ETL) of the two emitting structures (the blue outer structure and the red / green internal structure) are doped, but that this is not necessary. Thus, for example at least one of the two emitting structures (preferably the blue structure) could be undoped.

Semi-transparent electrodes and optical cavities receiving these sub-pixels can be optimized, so as to maximize the efficiency of these OLED units and the light emission cones, via the inter-electrode space and the distances between diodes. It should be noted that the precise alignment of the transmitting structures of these two backplanes 102a and 102b is not as essential as for the screens with a single backplane, except for the purpose of optimizing the total luminance because the inter-pixel areas of the upper matrix 102a hide the flux emitted by the pixels of the lower matrix 102b. However, a misalignment does not induce a loss of resolution in the device 101.

In addition, one advantageously chooses for each blue sub-pixel a transmission area twice as large as that of each green or red pixel. The resolution of the screen then corresponds to the size of each blue subpixel and the addressing of the screen takes into account this difference in size between sub-pixels to compensate for the differences in resolution of the two backplanes 102a and 102b. .

In summary, the major advantage of this device 101 is the considerable gain in definition provided by these two "backplanes" 102a and 102b, and also in the lifetime of the "OLED" units, without being penalized by a requirement of precise alignment of the sub-pixels.

Claims

1) A polychromatic electronic display device (1, 1, 101) comprising an electroluminescent emission face and, towards the interior of the device, at least one substrate (2, 102a, 102b) coated with a matrix of pixels , this device comprising a stack of several light-emitting units (U i and U _e) in which each pixel consists of three sub-pixels (R, G, B ₁ ') of different colors, characterized in that, for each pixel, the sub-pixel of the lowest transmission wavelength λ _c , or critical sub-pixel (B '), is exclusively located in that of the units, or external unit (U _e ), which is adjacent to this face of emission, each other sub-pixel (R, V) emitting at a wavelength greater than λ _c being exclusively located in a unit (U ₁ ) which is internal with respect to this external unit and which is adjacent to the substrate , the area of this critical sub-pixel (B ') being greater than that of each other sub-pixel (R , V). 2) Device (1, l ', 101) according to claim 1, characterized in that said critical subpixel (B') is activatable independently of each other sub-pixel (R, V) ₁ being designed to be transparent when it is not activated and, when it is activated, to emit at said wavelength λ _c by adding, if necessary, the radiation emitted by each other sub-pixel. 3) Device (1, l ', 101) according to claim 1 or 2, characterized in that the area of said critical sub-pixel (B') is at least equal to the sum of those of the other sub-pixels (R '). and V). 4) Device (1, l ', 101) according to one of the preceding claims, characterized in that each pixel comprises organic structures emitting radiation (E _R or E' _R , E _v or E ' _v , E _B or E' _B ), such as organic light-emitting diodes ("OLEDs"), which respectively form the sub-pixels (R, V, B ') and which are each interposed between and in electrical contact with two electrodes (4 and 6, 5 and 6, 6 and 3), one of these electrodes being transparent or semi-transparent (4, 5). 5) Device (1, l ', 101) according to claim 4, characterized in that said stack consists of two electroluminescent units respectively external (U _e ) and internal (Uj), said critical sub-pixel (B') emitting within said external unit and being stacked on the other subpixels (R and V) which all emit within said internal unit. 6) Device (1, l ') according to claim 5, characterized in that it comprises a single substrate (2) of the active or passive matrix type, each pixel being delimited by an external electrode (3) applied to the structure transmitting said critical sub-pixel (B '), or critical structure (E _B ), and a plurality of internal electrodes (4 and 5) which are applied to said substrate and on which are deposited spacially the transmitting structures of the other sub-pixels. pixels (R and V), or non-critical structures (E _R and E _v ), at least one intermediate electrode (6) being applied to the non-critical structures and / or the critical structure. 7) Device (1, l ') according to claim 6, characterized in that it comprises a single intermediate electrode (6) which is applied at a time, for each pixel, under said critical structure (E _B ) and on said non-critical structures (E _R and Ev) with which this critical structure is substantially aligned. 8) Device according to claim 6, characterized in that it comprises two outer and inner intermediate electrodes which are superimposed by being separated by at least one electrically insulating and transparent layer, preferably made of a material selected from the group consisting of aluminum oxides, silicon oxides, zinc oxides and silicon nitrides, and which are respectively applied, for each pixel, under said critical structure (E ₆ ) and on all of said non-critical structures (E _R and Ev). 9) Device according to claim 8, characterized in that said inner electrodes and said external intermediate electrode each form a transparent or semi-transparent anode, and in that the inner intermediate electrode and the outer electrode each form a reflective cathode. 10) Device (101) according to claim 5, characterized in that it comprises two substrates respectively external (102a) and internal (102b) which are each active or passive matrix and which are assembled to one another in their peripheries by adhesive-sealing beads (110) for the device, the external substrate being provided with regularly spaced critical emitting structures (E'B) which each form a critical subpixel (B '), and the inner substrate being provided with regularly spaced non-critical emitting structures (E'R, E ' _V ) which each form at least one of the other sub-pixels (R, V) and which are separated from these critical structures by an electrical insulator, the two matrices formed by these substrates being connected to independent power supply circuits. 11) Device (101) according to claim 10, characterized in that said substrates (102a and 102b) are separated from each other by a distance of less than 2 microns, to minimize the emissions of a non-critical structure (E'R, E'v) to a neighboring non-critical structure and maximize them towards the critical structure (E ' _B ) vis-à-vis. 12) Device (1, l ', 101) according to one of claims 5 to 11, characterized in that the emitting structure (ER OR E'R, EV OR EV) of each of the sub-pixels (R, V) other than said critical sub-pixel (B ') is able to emit selectively, as a function of the electrical voltage which is applied, at least two distinct radiation wavelengths both greater than the λ _c of this critical sub-pixel so as to successively form at least two-color non-critical subpixels. 13) Device (1, l ', 101) according to one of the preceding claims, characterized in that said sub-pixels consist of three sub-pixels (R, V, B ¹ ) respectively red, green and blue, said sub-pixels critical pixel (B ') exclusively located in said external unit (U _e ) being a sub-pixel emitting in blue, and the other sub-pixels (R and V) exclusively located in said internal unit (UO being sub-pixels emitting in red and / or green. 14) Device (1, l ', 101) according to claims 12 and 13, characterized in that the emitting structure of each non-critical sub-pixel (R, V) comprises two separate emitting materials capable of emitting in the red at low voltage and in the green at higher voltage.