Method for manufacturing a color conversion optoelectronic device, comprising a step of polarizing an electret layer in a localized manner by means of the upper electrodes of the diodes

Abstract

The invention relates to a method for manufacturing an optoelectronic device (1) comprising a matrix of diodes (D1, D2, D3) and a matrix of color conversion portions (P1, P2), comprising the following steps: providing the matrix of diodes (D1, D2, D3), and upper electrode layers (E1, E2, E3); depositing a dielectric layer (26) having a substantially zero surface potential; applying a potential difference between an electrode (2) and the first upper electrode layers (E1), resulting in the formation of first patterns (M1) with a non-zero surface potential in the dielectric layer (26); producing the first color conversion portions (P1), by bringing the dielectric layer (26) into contact with a colloidal solution (S1) containing first photoluminescent particles (p1). Figure for abstract: Fig. 1E

Description

Title of the invention: Method for manufacturing a color conversion optoelectronic device, comprising a step of polarizing an electret layer in a localized manner by means of the upper electrodes of the diodes Technical field

[0001] The field of the invention is that of methods for manufacturing optoelectronic devices comprising a matrix of diodes for emitting or detecting electroluminescent radiation, associated with color conversion portions. The invention finds application in particular in display screens and image projectors. STATE OF THE PRIOR ART

[0002] There are optoelectronic devices comprising a matrix of identical light-emitting diodes covered at least in part by color conversion portions. Such optoelectronic devices can form display screens or image projection systems comprising a matrix of luminous pixels of different colors.

[0003] In such an optoelectronic device, each light pixel comprises one or more light-emitting diodes associated with a color conversion portion. In order to obtain light pixels adapted to emit light radiation of different colors, for example blue, green or red, the light-emitting diodes may be adapted to emit all of the same light, for example blue, and the green and red pixels comprise light conversion portions adapted to absorb at least part of the incident blue light, and to emit in response green light or red light.

[0004] The light-emitting diodes are therefore preferably identical to each other, and emit light radiation of the same wavelength. They may be formed from a semiconductor material comprising elements from column III and column V of the periodic table, such as a III-V compound, in particular gallium nitride (GaN), indium gallium nitride (InGaN) or aluminum gallium nitride (AlGaN). They are arranged so as to form a matrix of light-emitting diodes having a front face through which the generated light radiation is transmitted.

[0005] The light converting portions may be formed from a binder matrix comprising particles of a photoluminescent material such as yttrium garnet. and aluminum (YAG, for Yttrium Aluminum Garnet, in English) activated by the cerium ion YAG:Ce. The photoluminescent particles can also be quantum dots, that is to say in the form of semiconductor nanocrystals whose quantum confinement is substantially three-dimensional.

[0006] The manufacturing method may comprise the deposition and then the structuring of a photoluminescent layer to form first light conversion portions, for example adapted to convert blue into red. These steps are carried out again to form second light conversion portions, for example adapted to convert blue into green. However, this method has the disadvantage of being poorly suited to diode matrices with a small pixel pitch, for example of the order of 5 μm, since problems of alignment or overlapping of the light conversion portions with each other may be present.

[0007] Document WO2014 / 136023 describes another manufacturing method, which uses an electret layer covering the diode matrix. The method firstly comprises a step of writing electrical charge patterns on the upper face of a dielectric layer to obtain the electret layer. For this, a polarized AFM (Atomic Force Microscopy) tip is used to locally inject the electrical charges. Then, a step of localized deposition of colloidal nanocrystals on the electrical charge patterns is carried out. For this, the electret layer is brought into contact with a colloidal solution containing the nanocrystals, which are naturally deposited on the electrical charge patterns under the effect of a di-electrophoretic force.However, this method has the particular disadvantage of having to inject the electrical charges sequentially, by moving the AFM tip on the surface of the upper face to form the electrical charge patterns there.

[0008] Document WO2021 / 023656 describes a similar method, where the electrical charge patterns are defined by a stamping technique, i.e. by bringing an electrically polarized pad into contact with a dielectric layer intended to form the electret layer. The lower face of the pad is structured to form polarized teeth, which come into contact with the dielectric layer. This produces the electret layer, the upper face of which has the electrical charge patterns. The electret layer is then brought into contact with a colloidal solution, the nanocrystals present then being deposited on the electrical charge patterns by dielectrophoresis. However, this method has the particular disadvantage of having to precisely position the pad with respect to the diode matrix.However, the uncertainty of positioning of the buffer with respect to the diode matrix can become problematic, in particular for diode matrices with small pixel pitch, for example of the order of 5 pm. Indeed, this uncertainty or imprecision of positioning can lead to poor positioning of the light conversion portions with respect to . diodes, and therefore to a degradation of the performance of the optoelectronic device. Statement of the invention

[0009] The invention aims to remedy at least in part the drawbacks of the prior art, and more particularly to propose a method for manufacturing an optoelectronic device, where the color conversion portions are produced in a localized and self-aligned manner on the corresponding diodes, while limiting the risk of misalignment with respect to the diodes.

[0010] For this, the subject of the invention is a method for manufacturing an optoelectronic device, which comprises: a matrix of diodes, having rear and front faces opposite one another, the front face being intended to receive or transmit light radiation; and a matrix of color conversion portions arranged on the front face, including first color conversion portions arranged opposite diodes called first diodes of the matrix of diodes.

[0011] The method comprises the following steps: - providing an optoelectronic structure comprising: the diode matrix; at least one lower electrode layer arranged at the rear face and adapted to polarize the diodes; and upper electrode layers arranged at the front face and adapted to polarize the diodes, including first upper electrode layers adapted to polarize the first diodes and distinct from the other upper electrode layers; - depositing a dielectric layer, an upper face of which opposite the front face has a substantially zero surface potential, covering the diode matrix and the upper electrode layers; - applying a potential difference between, on the one hand, a temporary electrode arranged on the dielectric layer, and on the other hand, the first upper electrode layers, resulting in the formation of first patterns with non-zero surface potential in the dielectric layer located only opposite the first upper electrode layers; then removing the temporary electrode; - carrying out the first color conversion portions, by bringing the dielectric layer into contact with a first colloidal solution containing first photoluminescent particles, which are deposited on the dielectric layer only opposite the first patterns with non-zero surface potential, thus forming the first color conversion portions.

[0012] Some preferred but non-limiting aspects of this manufacturing method are as follows.

[0013] The color conversion portion matrix may include second color conversion portions, distinct from the first color conversion portions, and arranged opposite diodes called second diodes of the diode matrix. In addition, the optoelectronic structure may comprise, among the upper electrode layers, second upper electrode layers adapted to polarize the second diodes. The method may then comprise, following the production of the second color conversion portions, the following steps: - applying a potential difference between, on the one hand, a temporary electrode arranged on the dielectric layer, and on the other hand, the second upper electrode layers, resulting in the formation of second patterns with non-zero surface potential in the dielectric layer located only opposite the second upper electrode layers; then removing the temporary electrode; - carrying out the second color conversion portions, by bringing the dielectric layer into contact with a second colloidal solution containing second photoluminescent particles distinct from the first photoluminescent particles, which are deposited on the dielectric layer only opposite the second patterns with non-zero surface potential, thus forming the second color conversion portions.

[0014] Each upper electrode layer may completely cover the diode above which it is located.

[0015] In the step of applying a potential difference between the temporary electrode and the upper electrode layers, the lower electrode layers may be unpolarized.

[0016] During the step of applying a potential difference between the temporary electrode and the upper electrode layers, said upper electrode layers then polarized can be connected to each other.

[0017] The diodes may be in contact with lower electrode layers, the lower electrode layers being distinct from each other, so that each diode can be selectively activated.

[0018] The method may comprise, after the color conversion portions have been produced, a step of connecting the first and second upper electrode layers to each other.

[0019] The method may comprise, after the color conversion portions have been carried out, a step of connecting all the upper electrode layers together.

[0020] The diodes may have identical light radiation emission or absorption properties.

[0021] The diodes can be made from an organic semiconductor compound or inorganic.

[0022] The invention also relates to a method for collectively and simultaneously manufacturing several optoelectronic devices from the same substrate, comprising the simultaneous implementation of the steps of the method according to any one of the preceding characteristics for each optoelectronic device.

[0023] In the context of the collective manufacturing method, during the step of applying a potential difference between the temporary electrode and the upper electrode layers, the temporary electrode can continuously cover all the diode matrices. Furthermore, said upper electrode layers, then polarized, can be connected to each other. Brief description of the drawings

[0024] Other aspects, aims, advantages and characteristics of the invention will appear better on reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example, and made with reference to the appended drawings in which:

[0025] Figures 1A to 1M illustrate different steps of a method of manufacturing an optoelectronic device according to one embodiment, where the electret dielectric layer is locally polarized by means of the upper electrode layers ensuring the electrical polarization of the diodes during their activation;

[0026] [Fig.2A] is a schematic and partial top view of an optoelectronic device according to another embodiment, where the upper electrode layers of the DI type diodes are connected to each other at the scale of the optoelectronic device, just like the upper electrode layers of the D2 type diodes;

[0027] [Fig.2B] is a top view, schematic and partial, of several optoelectronic devices according to another embodiment, manufactured collectively from the same substrate (wafer), where the upper electrode layers of the diodes of a first type of light pixel are connected to each other at the scale of the substrate, just like the upper electrode layers of the diodes of a second type of light pixel;

[0028] Figures 3A to 3D illustrate different steps of a method of manufacturing an optoelectronic device according to another embodiment, where the diodes are organic light-emitting diodes.

[0029] DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0030] In the figures and in the remainder of the description, the same references represent identical or similar elements. In addition, the different elements are not shown to scale so as to enhance the clarity of the figures. Furthermore, the different embodiments and variants are not mutually exclusive and may be combined with each other. Unless otherwise stated, the terms "substantially", "approximately", "in the order of" mean to within 10%, and preferably to within 5%. Furthermore, the terms "between ... and ..." and equivalents mean that the limits are included, unless otherwise stated.

[0031] The invention relates to a method for manufacturing an optoelectronic device comprising a matrix of diodes, at least a portion of the diodes being covered by color conversion portions, so as to form a matrix of luminous pixels of different colors. The diodes may be emissive diodes so that the optoelectronic device may be, for example, a display screen, or may be detector diodes so that the optoelectronic device may be a matrix photodetector. Furthermore, the diodes may be organic (OLED) or inorganic (LED) light-emitting diodes, or organic or inorganic photodetectors.

[0032] The production of the color conversion portions is obtained by the localized deposition of photoluminescent particles on an electret dielectric layer where non-zero surface potential patterns are previously defined. As detailed below, the formation of these surface potential patterns is carried out in particular by means of the upper electrode layers which also ensure the electrical polarization of the diodes during their activation. As detailed below, these upper electrode layers can be common per type of color pixel and are distinct from one type of color pixel to another. On the other hand, once the color conversion portions are produced, the upper electrode layers can remain common per type of color pixel, or can even be common for all the color pixels, or can be made distinct per pixel.By common, we mean that they are connected together to apply the same electrical potential.

[0033] Generally speaking, an electret layer is a dielectric layer containing electrical charges or a quasi-permanent dipole polarization. Also, the electret dielectric layer has, on its upper face, a non-zero surface potential. This results in the fact that the electret dielectric layer emits an external electric field in the absence of an applied field. In the context of the invention, the upper face of the electret dielectric layer has areas (called patterns) where the surface electric potential is non-zero. Outside of these patterns, the surface potential is substantially zero.

[0034] Thus, when producing the color conversion portions, the upper electrode layers are distinct, and distributed by type of color conversion pixel. Thus, non-zero surface potential patterns are formed where photoluminescent particles will then be naturally deposited, in a localized manner, by electrophoresis or dielectrophoresis during the formation of the color conversion portions. color conversion. Also, the light conversion portions are naturally located opposite (i.e. "perpendicular") the surface potential patterns, and are not located outside these predefined patterns. This process then makes it possible to precisely define the surface potential patterns on the upper face of the electret dielectric layer, even when the diode matrix has a large dimension (in particular when it is produced using 200 mm wafer technology) and / or the pixel pitch of the diode matrix is small (for example, of the order of 5 pm).

[0035] Thus, for example, in the case of a matrix of red, green, blue (RGB) pixels where the diodes are identical and all emit the same blue light, when producing the red color conversion portions, only the upper electrode layers of the red pixels are activated, while the upper electrode layers of the other pixels (green and blue) are not activated. Similarly, when producing the green color conversion portions, only the upper electrode layers of the green pixels are activated, while the upper electrode layers of the other pixels (red and blue) are not activated.

[0036] The color conversion portions are formed from particles made of at least one photoluminescent material, and preferably nanoparticles whose maximum dimension is between 0.2nm and 1000nm, for example between 0.2nm and 1000nm, and for example between 1nm and 30nm. The size and / or composition of the photoluminescent particles are chosen according to the desired luminescence wavelength. The shape of the particles can be any, for example spherical, angular, flattened, elongated, etc.

[0037] The photoluminescent particles may be quantum dots, i.e. semiconductor nanocrystals whose quantum confinement is substantially three-dimensional. The average size of the quantum dots may then be between 0.2 nm and 50 nm, for example between 1 nm and 30 nm. They may also be nanoplatelets, i.e. nanoparticles having an essentially two-dimensional shape. Also, the smallest dimension (thickness) is less than the other two dimensions of length and width, preferably by a ratio of at least 1.5.

[0038] The photoluminescent particles may in particular be formed from at least one semiconductor compound, which may be chosen, for example, from cadmium selenide (CdSe), indium phosphorus (InP), indium gallium phosphorus (InGaP), cadmium sulfide (CdS), zinc sulfide (ZnS), cadmium oxide (CdO) or zinc oxide (ZnO), zinc cadmium selenide (CdZnSe), zinc selenide (ZnSe) doped for example with copper or manganese, graphene or from other suitable semiconductor materials. Nanoparticles may also have a core / shell structure, such as CdSe / ZnS, CdSe / CdS, CdSe / CdS / ZnS, PbSe / PbS, CdTe / CdSe, CdSe / ZnTe, InP / ZnS or other. The particles may also have a perovskite crystal structure containing atoms such as those listed for nanoparticles but also Cs, Mn, Br.

[0039] Furthermore, the light conversion portions are adapted to convert at least in part incident light radiation of a first wavelength Xi into luminescence light radiation of longer wavelength X2. By way of illustration, they may be adapted to absorb blue light, i.e. light whose wavelength is between approximately 440nm and 490nm, and to emit in the green, i.e. at a wavelength between approximately 495nm and 560nm, or even in the red, i.e. at a wavelength between 600nm and 650nm. Wavelength is understood here to mean the wavelength at which the emission spectrum has an intensity peak.

[0040] For purely illustrative purposes, the diodes may be emissive and have an emission spectrum in the visible or infrared (for example in the NIR or the SWIR), or even ultraviolet (200-400 nm). In the case of an array of emissive diodes, the incident light radiation is the radiation emitted by the diodes, whereas in the case of photodiodes, it is the light radiation coming from an external environment and directed towards the photodiodes. In the latter case, the diodes are then adapted to absorb incident light radiation of different wavelengths all contained in the same predefined absorption spectrum.

[0041] Figures 1A to 1M illustrate different steps of a method for manufacturing an optoelectronic device 1 according to one embodiment. In this example, the optoelectronic device 1 comprises a matrix of light pixels of the RGB (red, green, blue) type. Each pixel is formed of at least one light-emitting diode (here one diode per pixel). Alternatively, the optoelectronic device 1 could comprise a matrix of light pixels of other types, for example of the RGB-IR (IR for Infrared) type. Also as a variant, the diodes may be photodiodes.

[0042] Here and for the remainder of the description, a direct three-dimensional orthogonal reference frame XYZ is defined, where the X and Y axes form a main plane in which a control substrate 10 extends, and where the Z axis is oriented along the thickness of the diode matrix in the direction of the front face. The terms 'lower' and 'upper' are defined with respect to an increasing positioning along the +Z direction.

[0043] With reference to [Fig. 1 A], the matrix of light-emitting diodes is provided. In this example, the diodes are divided into three types denoted D1, D2, D3, according to the type of luminous pixel to which they belong, for example here blue pixels for the diodes D1, red pixels for the diodes D2, and green pixels for the diodes D3. The diodes rest here on a control substrate 10, and are electrically polarized here by one or more lower electrode layers 11 and by upper electrode layers E1, E2, E3. Other configurations are possible, in particular in the case where the control substrate 10 is electrically conductive. The diode matrix has a rear face, by which it is assembled and connected to the control substrate 10, and a front face, opposite the rear face, which is intended to receive or transmit light radiation. In this example where the diodes are emissive, the front face transmits the light radiation emitted by the diodes.

[0044] In this example, the control substrate 10 provides several functions: the mechanical support of the diode matrix, the electrical polarization of the upper electrode layers E1, E2 during the steps of producing the light conversion portions P1, P2, and the electrical polarization of the diodes D1, D2, D3 during operation of the optoelectronic device. Here, it comprises a CMOS type control circuit, and has electrical connection pads 11 which are flush with the upper face and come into contact with lower electrode layers 21 of the diodes D1, D2, D3. These lower electrode layers 21 are here layers distinct from each other, in the sense that each lower electrode layer 21 of a diode is physically distinct from that of the adjacent diode. This configuration is described in detail in the document WO2017 / 194845 AL

[0045] The diodes D1, D2, D3 are here inorganic light-emitting diodes. They can be produced in a conventional manner, for example by epitaxy of semiconductor layers from a growth substrate, then by transfer to the control substrate 10. Each diode D1, D2, D3 can be formed from a stack of: a lower semiconductor portion 22 (oriented towards the control substrate 10) doped with a first type of conductivity, for example p-type, in electrical contact with a lower electrode layer 21; an active zone 23 where the light radiation of the light-emitting diode is emitted; and an upper semiconductor portion 24 doped with a second type of conductivity, for example n-type, in electrical contact with an upper electrode layer E1, E2 or E3. Diodes D1, D2, D3 can be made from the same semiconductor compound, for example based on a III-V compound such as GaN, InGaN, AlGaN.

[0046] Preferably, the diodes D1, D2, D3 are structurally identical, so that the light radiation emitted is identical from one diode to another in terms of wavelength. In this example, the diodes D1, D2, D3 are adapted to emit light radiation in the blue, that is to say whose emission spectrum has an intensity peak at a wavelength between approximately 440nm and 490nm.

[0047] [Fig.lB] is a top view of the diode matrix illustrated in [Fig.lA]. This is obviously an example because other configurations are possible. Here, each RGB pixel comprises three diodes D1, D2, D3. The upper electrode layers El intended to polarize the diodes D1 extend here over several adjacent diodes D1. The same is true for the upper electrode layers E2 intended to polarize the diodes D2 and for the upper conductors intended to polarize the diodes D3. Preferably, the upper electrode layers El are connected to each other by a lateral conductive strip Eli. The upper electrode layers E2 are also connected to each other by a lateral conductive strip E21. The upper electrode layers are connected to the control substrate by connection pads 3 (pad 3i for the electrode layers El, pad 32 for the layers E2....), for example by conductive vias which extend through the dielectric filling material 25 which surrounds the diodes D1, D2, D3.

[0048] Preferably, the electrode layers El completely cover the diodes D1 in the XY plane, just as the electrode layers E2 completely cover the diodes D2, and the electrode layers E3 completely cover the diodes D3. Obviously, the electrode layers of the same type (e.g. El) do not extend opposite the diodes of the other types (e.g. D2 and D3).

[0049] The lower and upper electrode layers are made of an electrically conductive material. The lower electrode layers 21 may be made of at least one metallic material chosen from Ti, Ni, Pt, Sn, Au, Ag, Ai, Pd, W, Pb, Cu, AuSn, TiSn or an alloy of these elements. They may preferably be reflective to the light radiation emitted by the diodes, and may thus be made from Ag. Furthermore, the material of the upper electrode layers E1, E2, E3 is at least partly transparent to the light radiation emitted by the diodes, and may be for example ITO (indium tin oxide), or even semi-transparent thin metallic materials (e.g. Ag).

[0050] With reference to [Fig. 1C], a dielectric layer 26 is then produced intended to form the electret layer. The dielectric layer 26 covers the diode matrix, and therefore the upper electrode layers E1, E2 and E3. It initially has a substantially zero surface potential, so that there are no unwanted patterns of non-zero surface potential. The dielectric layer 26 is made of a dielectric material, for example inorganic, such as a silicon oxide, nitride or oxynitride, for example SiO2, Si3N4, Al2O3 (in particular in the case of OLED), among others. It may have a thickness of the order of a few hundred nanometers, for example approximately 400nm.

[0051] With reference to [Fig.lD], the surface potential patterns Ml are produced by localized electrostatic polarization of the dielectric layer 26, which then forms the layer electret dielectric. To do this, a temporary electrode 2 is placed above the dielectric layer 26, and preferably in contact with it. Note that this temporary electrode 2 can be formed from a rigid conductive plate, or even a layer of an electrically conductive liquid (metal, electrolyte, etc.), among others. A potential difference is applied between the temporary electrode 2 on the one hand, and only the upper electrode layers El on the other hand. This potential difference can be of the order of a few tens or hundreds of volts, for example between 10V and 200V. During this step, only the upper electrode layers El are activated, and not the other upper electrode layers E2 and E3. Non-zero surface potential patterns Ml are formed in a localized manner at the upper face of the electret dielectric layer 26, opposite only the diodes Dl, and not opposite the diodes D2 and D3.The temporary electrode 2 is then removed. Note that, during this step, the lower electrode layers 21 remain unpolarized, so that the diodes D1, D2, D3 are inactive.

[0052] [Fig.lE] and [Fig.lF] illustrate the structure obtained. The surface potential patterns Ml are present only opposite the upper electrode layers EL. In other words, the electret dielectric layer 26 has a surface potential that is substantially zero everywhere, except opposite the upper electrode layers EL. Note that, in this example, the surface potential patterns Ml may not extend opposite the lateral conductive strip E1 connecting the upper electrode layers EL.

[0053] With reference to [Fig. IG], the first color conversion portions PI are then carried out by localized deposition of first photoluminescent particles pl on the electret dielectric layer 26, opposite only the surface potential patterns ML. For this, the procedure is similar to that described in documents WO2014 / 136023 and WO2021 / 023656. Thus, a colloidal solution SI containing the first photoluminescent particles pl is placed in contact with the upper face of the electret dielectric layer 26. The photoluminescent particles pl are suitable for converting blue light into red light. The entire stack can thus be immersed in the colloidal solution SI, or a drop of such a solution can be deposited on the electret dielectric layer 26.Due to the non-zero surface potential located in the patterns Ml, a non-uniform electric field is generated which causes a localized deposition of the photoluminescent particles pl by electrophoresis or dielectrophoresis. Also, the photoluminescent particles pl are deposited essentially opposite the first patterns Ml (and therefore opposite the diodes D1), and substantially not outside the patterns Ml (i.e. not opposite the diodes D2 and D3). The contact time of the colloidal solution SI on the electret dielectric layer 26 depends in particular on the quantity of photoluminescent particles pl to be deposited and therefore on the thickness. desired thickness of the PI color conversion portions, as well as the value of the surface potential. For example, the thickness of the PI color conversion portions can be of the order of a few hundred nanometers, for example equal to approximately 400nm. The SI colloidal solution is then removed and the electret dielectric layer can be dried.

[0054] [Fig. 1H] and [Fig. II] illustrate the structure obtained. The color conversion portions PI are present only opposite the upper electrode layers E1 and therefore the diodes DI. They do not extend opposite the diodes D2 and D3. This produces the red pixels whose relative positioning of the color conversion portions PI with respect to the diodes DI is optimal. The PI portions do not extend opposite the diodes D2 and D3, and advantageously completely cover the diodes DI in the XY plane. Note that, here, the color conversion portions PI form separate pads, the same pad however extending opposite several adjacent diodes DI. A thin-layer encapsulation (e.g. in Al2O3) of the color conversion portions PI can be carried out.

[0055] The preceding steps can then be repeated to produce the color conversion portions P2 located opposite the diodes D2, forming green pixels here. Indeed, the color conversion portions PI are adapted here to convert blue light (wavelength between approximately 440nm and 490nm) into red light (wavelength between approximately 600nm and 650nm). On the other hand, the color conversion portions P2 are adapted here to convert blue light into green light (wavelength between approximately 495nm and 560nm).

[0056] With reference to [Fig.U], the surface potential patterns M2 are produced by localized electrostatic polarization of the electret dielectric layer 26. For this, a temporary electrode 2 is again placed above the electret dielectric layer 26, and preferably in contact with it. In this example, this temporary electrode 2 is a layer of a liquid metal (or an electrolyte), but it can obviously be a rigid conductive plate. A potential difference is applied between the temporary electrode 2 on the one hand, and only the upper electrode layers E2 on the other hand. This potential difference can be of the order of ..., for example between 10V and 200V. During this step, only the upper electrode layers E2 are activated, and not the other upper electrode layers E1 and E3.Non-zero surface potential patterns M2 are formed locally at the upper face of the electret dielectric layer 26, opposite only the diodes D2, and not opposite the diodes DI and D3. The temporary electrode is then removed.

[0057] [Fig.1K] illustrates the structure obtained, where the electret dielectric layer 26 comprises only the surface potential patterns M2. Indeed, the patterns M1 can have disappeared after a predefined period, or may have been removed (e.g. during a cleaning bath). They may also be present but be screened by the facing PI pads. The surface potential patterns M2 are present only facing the upper electrode layers E2. In this example, the electret dielectric layer 26 has a surface potential that is substantially zero everywhere, except facing the upper electrode layers E2. Note that, in this example, the surface potential patterns M2 do not extend facing the lateral conductive strip E21 connecting the upper electrode layers E2, since the temporary electrode 2 has not been placed above it.

[0058] With reference to [Fig.11], the color conversion portions P2 are then produced by localized deposition of first photoluminescent particles p2 on the electret dielectric layer 26, opposite only the surface potential patterns M2. For this, the procedure is as previously, by placing a colloidal solution S2 containing the photoluminescent particles p2 in contact with the upper face of the electret dielectric layer 26. The photoluminescent particles p2 are different from the particles pl in that they are adapted to convert blue light into green light. The entire stack can thus be immersed in the colloidal solution S2, or a drop of such a solution can be deposited on the electret dielectric layer. Due to the non-zero surface potential located in the surface potential patterns M2, a non-uniform electric field is generated which causes localized deposition of the photoluminescent particles p2 by electrophoresis or dielectrophoresis.Also, the photoluminescent particles p2 are deposited essentially opposite the patterns M2 (and therefore opposite the diodes D2), and substantially not outside the patterns M2 (i.e. not opposite the diodes DI and D3). The contact time of the colloidal solution S2 on the electret dielectric layer 26 depends in particular on the quantity of photoluminescent particles p2 to be deposited and therefore on the desired thickness of the color conversion portions P2. For example, the thickness of the color conversion portions P2 may be of the order of a few hundred nanometers, for example equal to approximately 400 nm. The colloidal solution S2 is then removed and the electret dielectric layer 26 can be dried. An encapsulation layer can be deposited.

[0059] [Fig. 1M] illustrates the optoelectronic device 1 obtained. The color conversion portions P1 are present only opposite the diodes D1 and define the red pixels; the color conversion portions P2 are located only opposite the diodes D2 and define the green pixels. The diodes D3 are here not covered by color conversion portions, thus forming blue pixels. A device with an RGB pixel matrix is thus obtained, where the color conversion portions P1, P2 have been deposited in a localized and self-aligned manner opposite the desired diodes, by electrophoresis or dielectrophoresis on the layer di electret electric 26 whose localized polarization was obtained by taking advantage of the upper electrode layers E1, E2 for polarizing the diodes. Thus, there was no need to produce upper electrodes dedicated to the production of the light conversion portions, which are different from the upper polarizing electrodes of the diodes during operation of the optoelectronic device 1.

[0060] This avoids having to resort to a step of localized injection of electric charges into a dielectric layer initially without electric charges, by means of an AFM tip or a conductive pad. Also, the method is rapid and the production of the light conversion portions is spatially precise, even in the context of a matrix of diodes produced from a large substrate (for example 200 mm) and / or whose pixel pitch is very small (for example 5 pm).

[0061] [Fig.2A] is a top view of an optoelectronic device 1 according to a variant of [Fig.1B]. The emissive surface of the optoelectronic device 1 is delimited by the dotted lines.

[0062] Here, each upper electrode layer El of the different pixels is electrically connected to the same connection pad 3i by a lateral conductive strip Eli which extends at the edge of the emissive surface. This connection pad 3i can be a conductive via which passes through the dielectric filling layer 25 of the optoelectronic structure to come into contact with a conductive pad 11 of the control substrate 10 (see [Fig.lA]). Similarly, each upper electrode layer E2 is electrically connected to the same connection pad 32 by a lateral conductive strip E21. This connection pad 32 can also be a conductive via connected to the control substrate 10.

[0063] Furthermore, in this example, each upper electrode layer E3 comes into contact with a conductive via 33 connected to the control substrate 10. Here, the diodes D3 are not covered by light conversion portions since the pixels here are blue pixels.

[0064] Thus, during the step of localized and self-aligned deposition of the photoluminescent particles p1, the upper electrode layers E1 are all connected to each other and polarized simultaneously, while the upper electrode layers E2 and E3 are unpolarized. And during the step of localized deposition of the photoluminescent particles p2, the upper electrode layers E2 are all connected to each other and polarized simultaneously, while the upper electrode layers E1 and E3 are unpolarized.

[0065] Finally, at the end of the manufacture of the optoelectronic device 1, the upper electrode layers E1 and E2 can be connected together to form an upper electrode common to the diodes D1 and D2. This can be done by means of a lateral conductive strip E121, which here extends from the lateral conductive strip Eli of the El layers towards a lateral conductive strip E21 of the E2 layers. A conductive pad 4 (dotted line) can then be deposited to connect the interconnecting lateral conductive strip El21 to the lateral conductive strip E21. This can be a conductive paste deposited by an inkjet type technique. Thus, the upper electrode layers El and E2 form a single interdigitated upper electrode which can be brought to an electrical potential, when the diodes DI and D2 are activated. The selective activation of the diodes DI and D2 can then be carried out by the polarization of this or that lower electrode layer 21.

[0066] It should also be noted that the upper electrode layers E3 can also be connected to the upper electrode layers E1 and E2, so as to form a single common interdigitated upper electrode. Different conventional techniques can be used (deposition of conductive pads to ensure interconnection, laser firing, etc.).

[0067] [Fig.2B] is a top view of several identical optoelectronic devices 1 according to an alternative embodiment, which illustrates a way of connecting the side bands to peripheral polarization bands.

[0068] In this example, the method relates to the collective and simultaneous manufacturing of identical optoelectronic devices 1, on the scale of the same substrate 5 (or wafer in English) of large dimension, for example having a diameter of 200 or 300 mm.

[0069] Here, when producing the color conversion portions PI, the upper electrode layers El are all connected to each other and are polarized together during the step of [Fig.lD]. Thus, the same lateral conductive strip Eli extends along several adjacent optoelectronic devices (see [Fig.2A]), and comes into contact with a main lateral conductive strip Ellp located at the edge of the substrate. Note that the temporary electrode 2 preferably extends so as to continuously cover all the diode matrices.

[0070] Similarly, when producing the color conversion portions P2, the upper electrode layers E2 are all connected to each other and are polarized together during the step of [Fig.U]. For this, the same lateral conductive strip E21 extends along several adjacent optoelectronic devices (see [Fig.2A]), and comes into contact with a main lateral conductive strip E21p located at the edge of the substrate.

[0071] At the end of the manufacturing process, the substrate 5 is cut to individualize the optoelectronic devices 1.

[0072] Also, the manufacturing method makes it possible to produce the color conversion portions PI, P2 by localized and self-aligned deposition of the photoluminescent particles with respect to the desired diodes, on the scale of the substrate 5.

[0073] Figures 3A to 3D illustrate different steps of a method of manufacturing a optoelectronic device 1 according to another embodiment. Here, the optoelectronic device 1 differs from that of figures 1A and following essentially in that the diodes D1, D2, D3 are organic light-emitting diodes, here in top emission (top emission in English). The optoelectronic device can thus be an OLED color screen having a high resolution (small pixels) and a high luminance linked to a high quantum efficiency. In this example, there will be a blue OLED emitting layer, deposited on all the pixels, and the coloring will be done by selective deposition of converters on the green and red pixels, respectively.

[0074] With reference to [Fig.3A], a control substrate 10 (CMOS) is provided having connection pads 11 which are flush with the upper face. These connection pads 11 form the lower electrode layers on the one hand, and others 12.1, 12.2 (not shown), 12.3 are intended to ensure the electrical polarization of the upper electrode layers E1, E2, E3.

[0075] With reference to [Fig.3B], a stack 30 of organic semiconductor layers is then produced, which extends over the control substrate 10 and covers the lower electrode layers 11. Conventionally, this is a stack of an HTL layer, emission layers, and an ETL layer. Then upper electrode layers E1, E2 and E3 are produced on the organic semiconductor stack 30. The upper electrode layers E1 are connected here to the same connection pad 12.1, just like the upper electrode layers E2 to a connection pad 12.2 (not shown).

[0076] With reference to [Fig.3C], a thin encapsulation film 26 (TFE in English) is then deposited, which covers the organic semiconductor stack 30 and the upper electrode layers E1, E2 and E3. This TFE layer 26 is made of a dielectric material, and is intended to form the electret dielectric layer. Note that the TFE can serve as an electret according to a variant. In the general case, we have the TFE then an electret above.

[0077] With reference to [Fig.3D], the color conversion pads P1 and P2 are then produced, which are located opposite, respectively, the upper electrode layers E1 and E2. These color conversion pads are produced as described previously with reference to Figures 1A and following. Thus, an organic diode optoelectronic device is obtained, which can have a high resolution, with color conversion pads P1 and P2 produced in a localized and self-aligned manner by means of the upper electrode layers E1 and E2.

[0078] Particular embodiments have just been described. Different variants and modifications will appear to those skilled in the art.

Claims

Claims

1. A method of manufacturing an optoelectronic device (1), which comprises: a matrix of diodes (Dl, D2, D3), having rear and front faces opposite each other, the front face being intended to receive or transmit light radiation; a matrix of color conversion portions (PI, P2) arranged on the front face, including first color conversion portions (PI) arranged opposite diodes called first diodes (Dl) of the matrix of diodes; the process comprising the following steps: providing an optoelectronic structure comprising: the diode matrix (Dl, D2, D3); at least one lower electrode layer (21) arranged at the rear face and adapted to polarize the diodes; and upper electrode layers (El, E2, E3) arranged at the front face and adapted to polarize the diodes, including first upper electrode layers (El) adapted to polarize the first diodes (Dl) and distinct from the other upper electrode layers (E2, E3); depositing a dielectric layer (26), an upper face of which opposite the front face has a substantially zero surface potential, covering the diode matrix (Dl, D2, D3) and the upper electrode layers (El, E2, E3); applying a potential difference between, on the one hand, a temporary electrode (2) arranged on the dielectric layer (26), and on the other hand, the first upper electrode layers (El), resulting in the formation of first patterns (Ml) with non-zero surface potential in the dielectric layer (26) located only opposite the first upper electrode layers (El); then removing the temporary electrode (2); carrying out the first color conversion portions (PI), by bringing the dielectric layer (26) into contact with a first colloidal solution (SI) containing first photoluminescent particles (pl), which are deposited on the dielectric layer (26) only opposite the first patterns (Ml) with non-zero surface potential, thus forming the first color conversion portions (PI).

2. A manufacturing method according to claim 1, • the matrix of color conversion portions comprising second color conversion portions (P2), distinct from the first color conversion portions (PI), and arranged opposite diodes called second diodes (D2) of the diode matrix; • the optoelectronic structure comprising, among the upper electrode layers (El, E2, E3), second upper electrode layers (E2) adapted to polarize the second diodes (D2); • the method comprising, following the performance of the second color conversion portions (P2), the following steps: • applying a potential difference between, on the one hand, a temporary electrode (2) arranged on the dielectric layer (26), and on the other hand, the second upper electrode layers (E2), resulting in the formation of second patterns (M2) with non-zero surface potential in the dielectric layer (26) located only opposite the second upper electrode layers (E2); then removing the temporary electrode (2); • carrying out the second color conversion portions (P2), by bringing the dielectric layer (26) into contact with a second colloidal solution (S2) containing second photoluminescent particles (p2) distinct from the first photoluminescent particles (pl), which are deposited on the dielectric layer (26) only opposite the second patterns (M2) with non-zero surface potential, thus forming the second color conversion portions (P2).

3. A manufacturing method according to claim 1 or 2, wherein each upper electrode layer (El, E2, E3) completely covers the diode above which it is located.

4. A manufacturing method according to any one of claims 1 to 3, wherein, in the step of applying a potential difference between the temporary electrode (2) and the upper electrode layers (E1, E2), the lower electrode layers (21) are unpolarized.

5. A manufacturing method according to any one of claims 1 to 4, wherein, during the step of applying a potential difference between the temporary electrode (2) and the upper electrode layers (E1, E2), said upper electrode layers then polarized are connected to each other.

6. A manufacturing method according to any one of claims 1 to 5, wherein the diodes are in contact with lower electrode layers (21), the lower electrode layers (21) being distinct from each other, so as to be able to activate each diode selectively.

7. A manufacturing method according to any one of claims 1 to 6, comprising, after the production of the color conversion portions (PI, P2), a step of connecting the first and second upper electrode layers (El, E2, E3) to each other.

8. A manufacturing method according to any one of claims 1 to 7, comprising, after the color conversion portions (PI, P2) have been produced, a step of connecting all the upper electrode layers (El, E2, E3) to each other.

9. Manufacturing method according to any one of claims 1 to 8, in which the diodes have identical light radiation emission or absorption properties.

10. Manufacturing method according to any one of claims 1 to 9, in which the diodes are made from an organic or inorganic semiconductor compound.

11. Method for collectively and simultaneously manufacturing several optoelectronic devices (1) from the same substrate (5), comprising the simultaneous implementation of the steps of the method according to any one of the preceding claims for each optoelectronic device (1).

12. A method of collective manufacturing according to claim 11, wherein, during the step of applying a potential difference between the temporary electrode (2) and the upper electrode layers (El, E2), the temporary electrode (2) continuously covers all the diode matrices, and wherein said upper electrode layers then polarized are connected to each other.

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