OPTOELECTRONIC DEVICE WITH A POLARIZER AND AT LEAST ONE RADIATION EMISSION

Description

FIELD OF INVENTION

[0001] The present invention relates to an optoelectronic device comprising a polarizer and at least one first emitting element configured to emit a first radiation. CONTEXT OF THE INVENTION

[0002] Many types of optoelectronic devices include radiation-emitting elements and polarizers. The emitting elements are designed to emit radiation that will be used, for example, to form part of an image. Examples of such electronic devices include display screens, projectors, and virtual reality headsets.

[0003] The emitting elements include, in particular, sets of light-emitting diodes, or sets of liquid crystals that allow the passage of light emitted by a light source to be blocked or allowed locally.

[0004] The polarizer is likely to fulfill a large number of roles, notably in conjunction with a quarter-wave plate to limit the reflection on the optoelectronic device of external radiation, or to control the emission of light according to the orientation of a liquid crystal through which the emitted light passes.

[0005] However, the passage of radiation emitted by the various emitting elements through the polarizer results in a loss of intensity, which depends on the polarization of the emitted radiation and the spatial orientation of the polarizer. In particular, if the emitting elements emit light with elliptical polarization, 50 percent (%) of the emitted radiation is blocked by the polarizer. Light sources, such as light-emitting diodes (LEDs), used in the prior art, naturally emit radiation with such polarization. This results in a significant loss of efficiency in the optoelectronic device.

[0006] The relevant prior art is described, for example, in patent documents US 2017 / 123267 A1, US 2019 / 018287 A1, US 2008 / 116468 A1 and US 2017 / 365749 A1. SUMMARY OF THE INVENTION

[0007] Therefore, there is a need for an optoelectronic device comprising a polarizer and an emitter that offers better performance than state-of-the-art optoelectronic devices.

[0008] To this end, an optoelectronic device is proposed according to claim 1

[0009] According to particular embodiments, the optoelectronic device has characteristics according to dependent claims 2-13. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings, in which: There figure 1 is a partial schematic cross-sectional representation of an example of an optoelectronic device according to the invention, comprising a set of emitting elements, The figure 2 is a partial schematic cross-sectional representation of another example of an optoelectronic device according to the invention, comprising a set of emitting elements, and the figure 3 is a partial schematic cross-sectional representation of an example of an emitting element of the figure 1 . DETAILED DESCRIPTION OF PREFERRED METHODS OF IMPLEMENTATION

[0011] A first example of an optoelectronic device 10 is shown on the figure 1 .

[0012] The optoelectronic device 10 is, for example, a display screen suitable for displaying images. Alternatively, the optoelectronic device 10 is a lamp, a projector, or even a pair of virtual reality or augmented reality glasses.

[0013] The optoelectronic device 10 comprises a substrate 12, a set of emitting elements 15A, 15B, 15C, a polarizer 20 and a control circuit 25. Optionally, the optoelectronic device 10 further comprises a set of walls 70.

[0014] Substrate 12 is configured to carry each emitter element 15A, 15B, 15C.

[0015] The substrate 12 is, for example, planar. In particular, the substrate 12 extends in a plane perpendicular to a normal direction N.

[0016] In addition, two directions D1 and D2 are defined, perpendicular to each other and each perpendicular to the normal direction N.

[0017] The substrate 12 is delimited along the main direction N by a first face 30 and by a second face 35 of the substrate 12.

[0018] Each of the first face 30 and the second face 35 is, for example, flat.

[0019] The substrate 12 is, for example, made at least partially of a first semiconductor material such as silicon, or an insulating material such as glass or sapphire.

[0020] The set of emitting elements 15A, 15B, 15C includes at least one set of first emitting elements 15A. Optionally, the set of emitting elements also includes a set of second emitting elements 15B and / or a set of third emitting elements 15C.

[0021] Each emitting element 15A, 15B, 15C is configured to emit a first radiation R1A, R1B, R1C.

[0022] Each first radiation comprises a first set of electromagnetic waves R1A, R1B, R1C.

[0023] A wavelength is defined for each electromagnetic wave.

[0024] Each initial set corresponds to a first range of wavelengths. The first range of wavelengths is the group formed by the set of wavelengths of the first set of electromagnetic waves.

[0025] A first average wavelength is defined for each first range of wavelengths.

[0026] Each first R1A, R1B, R1C radiation is, in particular, a visible radiation. A first R1A, R1B, R1C radiation whose first average wavelength is between 430 nanometers (nm) and 750 nm is an example of visible light.

[0027] Each first 15A emitting element is, for example, configured to emit a first red R1A radiation.

[0028] Each second emitting element 15B is, for example, configured to emit a first green R1B radiation.

[0029] Each third emitting element 15C is, for example, configured to emit a first blue R1C radiation.

[0030] A first blue R1C radiation, for example, has an average wavelength between 430 nm and 470 nm.

[0031] A first green R1B radiation, for example, has an average wavelength between 520 nm and 560 nm.

[0032] A first red R1A radiation, for example, has an average wavelength between 580 nm and 700 nm.

[0033] Each emitting element 15A, 15B, 15C is, for example, intended to form part of an image element 37, also called a "pixel" from the English "Picture Element".

[0034] Each pixel 37 groups together one or more emitting elements 15A, 15B, 15C that are close to each other. For example, when the screen is a monochrome screen, each pixel 37 contains a single emitting element 15A, 15B, 15C.

[0035] When the screen is a polychrome screen, each pixel 37 has several emitting elements 15A, 15B, 15C, at least one of the emitting elements 15A, 15B, 15C being configured to emit a first radiation R1A, R1B, R1C having a mean wavelength different from the mean wavelengths of the other emitting elements 10 of the same pixel 37.

[0036] In particular, each pixel 37 has at least one first emitting element 15A, at least one second emitting element 15B and at least one third emitting element 15C.

[0037] In the example shown on the figure 1 , each pixel 37 has three emitting elements 15A, 15B, 15C aligned successively along the direction D1, however the spatial distribution of the emitting elements 15A, 15B, 15C of the same pixel 37 is likely to vary.

[0038] It should be noted that the number of emitting elements 15A, 15B, 15C of each pixel 37 is likely to vary, as well as their colours.

[0039] Alternatively, each first radiation R1A, R1B, R1C is identical to the other first radiations R1A, R1B, R1C. For example, each first radiation R1A, R1B, R1C is a blue radiation, or even an ultraviolet radiation.

[0040] Each emitting element 15A, 15B, 15C includes an emitter 40. Furthermore, each first or second emitting element 15A, 15B also includes a converter 45.

[0041] It should be noted that, in the first example of optoelectronic device 10, each third emitting element 15C is devoid of a converter 45. However, embodiments in which at least one third emitting element 15C includes a radiation converter are also conceivable.

[0042] In addition, each emitting element 15A, 15B, 15C includes a quarter wave plate 48.

[0043] The quarter-wave plate 48 is, for example, interposed between the emitter 40 and the corresponding converter 45 as shown in the figure 1 Alternatively, as shown on the figure 2 , the converter 45 is interposed between the emitter 40 and the quarter-wave plate 48.

[0044] Each emitter 40 is carried by the first face 30. For example, each emitter 40 extends from the first face 30 in the normal direction N.

[0045] The emitters 40 of the different emitting elements 10 form, for example, a two-dimensional lattice in a plane perpendicular to the normal direction N, for example a square mesh lattice. Alternatively, the mesh is hexagonal, triangular, or rectangular.

[0046] Each emitter 40 comprises, for example, a semiconductor structure 47. By the expression "semiconductor structure" is meant any structure made at least partially of a semiconductor material.

[0047] A stack of semiconductor layers arranged along the normal D direction is an example of a semiconductor structure. Such a structure is often called a "two-dimensional structure".

[0048] A three-dimensional semiconductor structure or a set of three-dimensional semiconductor structures are other examples of semiconductor structures.

[0049] A lateral dimension is defined for each emitter 40. The lateral dimension is the maximum dimension of a contour surrounding the emitter 40 in a plane perpendicular to the normal direction N, while not surrounding any part of another emitter 40.

[0050] The lateral dimension is less than or equal to 1 millimeter (mm), in particular less than or equal to 20 µm. For example, the lateral dimension is less than or equal to 10 µm. In one embodiment, the lateral dimension is less than or equal to 5 µm. It should be noted that the lateral dimension is subject to variation.

[0051] Each emitter 40 is configured to emit a second radiation R2. For example, each emitting structure is an LED structure.

[0052] In particular, each emitter 40 is configured to emit the second radiation R2 when the emitter 40 is traversed by an electric current, as will be explained in more detail below.

[0053] The second radiation R2 exhibits a second range of wavelengths. This second range is distinct from the first. In particular, the second range has a second average wavelength, which is different from the first average wavelength. Specifically, the second average wavelength is strictly shorter than the first average wavelength.

[0054] The second radiation R2 is, for example, blue light. In particular, the second radiation R2 is identical to the first radiation R1C of each third emitting element 15C, when these third emitting elements 15C are devoid of converters 45.

[0055] Alternatively, the second radiation R2 is ultraviolet radiation, that is to say radiation with a second average wavelength between 200 nm and 405 nm.

[0056] Each second radiation R2 is, for example, a radiation exhibiting elliptical polarization.

[0057] An example of a 15A, 15B, 15C emitting element comprising a 40 emitter is shown on the figure 3 .

[0058] The transmitter 40 comprises, for example, one or a set of semiconductor structure(s) 47 at least one first contact 49A, at least one second contact 49B and a block 50.

[0059] Each semiconductor structure 47 is, for example, an LED structure.

[0060] Each semiconductor structure 47 is, for example, a three-dimensional structure. It should be noted that in conceivable variants, the semiconductor structure 47 is a two-dimensional structure.

[0061] According to the example shown on the figure 3 The emitting element 15A, 15B, 15C comprises a plurality of three-dimensional semiconductor structures 47, these emitting structures 47 being notably identical to one another. Two semiconductor structures 47 are represented on the figure 3 However, this number is subject to change.

[0062] Each semiconductor structure 47 extends from the first face 35 along the normal direction N.

[0063] Each semiconductor structure 47 is configured to emit all or part of the second radiation R2 when the semiconductor structure 47 is traversed by an electric current.

[0064] Semiconductor structure 47 is, for example, a microwire.

[0065] The semiconductor structure 47 comprises a core 52 and a covering layer 55.

[0066] The 52 core acts as either an n-doped layer or a p-doped layer. The 52 core is made of a semiconductor material referred to as the "core semiconductor material" in the following.

[0067] For example, the core semiconductor material is n-doped.

[0068] The core semiconductor material is, for example, GaN.

[0069] The 52 kernel is configured to support the 55 cover layer.

[0070] The core 52 extends from the first face 35 along the normal direction N. In particular, the core 52 is electrically connected to the substrate 12.

[0071] The core 52 extends, for example, through an electrically insulating layer 57 covering part of the first face 35.

[0072] Core 52 is, for example, a cylinder.

[0073] A cylindrical surface is a surface consisting of all points on all lines parallel to a given line that pass through a fixed plane curve in a plane not parallel to the line. A solid bounded by a cylindrical surface and two parallel planes is called a cylinder. When a cylinder is said to extend in a given direction, that direction is parallel to the line.

[0074] A cylinder has a uniform cross-section along the direction in which the cylinder extends.

[0075] The cross-section of the 52 core is polygonal. For example, the cross-section is hexagonal.

[0076] However, other shapes can be considered for the cross-section.

[0077] It should be noted that the shape of the nucleus 52 can vary, for example if the semiconductor structure 47 is not a microwire.

[0078] A diameter is defined for the core 52. The diameter is, in the case of a cylindrical core 52, the maximum distance between two points of the core 52 which are diametrically opposite in a plane perpendicular to the normal direction N.

[0079] When the 52 core has a hexagonal cross-section, the diameter of the core is measured between two opposite angles of the hexagon.

[0080] The diameter of the 52 core is between 10 nm and 5 µm.

[0081] A length measured along the normal direction N is defined for the 52 nucleus. The length is between 10 nm and 100 µm.

[0082] The 52 core has a top face and a lateral face.

[0083] The upper face delimits the core 52 along the normal direction N. For example, the upper face is perpendicular to the normal direction N.

[0084] The lateral face surrounds the core 52 in a plane perpendicular to the normal direction N.

[0085] The lateral face extends between the upper face and the substrate 12. When the core 52 has a polygonal section, the lateral face has a set of planar facets.

[0086] The cover layer 55 covers at least partially the core 52. For example, the cover layer 55 covers at least partially the top face of the core 52. In particular, the cover layer 55 completely covers the top face.

[0087] In the example illustrated in the figure 3 , the cover layer 55 covers at least partially the upper face and at least partially the lateral face.

[0088] As can be seen in the figure 3 , the cover layer 55 completely surrounds the core 52 in a plane perpendicular to the normal direction N. In other words, the cover layer 55 forms a shell around the core 52.

[0089] The cover layer 55 includes at least one emitting layer 60 and one doped layer 65.

[0090] Each emitting layer 60 is configured to emit the second radiation R2 when the electric current passes through the semiconductor structure 47.

[0091] Each emitting layer 60 is interposed between the nucleus 52 and the doped layer 65.

[0092] Each emitting layer 60 is made of a semiconductor material.

[0093] For example, the cover layer 55 comprises a stack of emitting layers 60 interposed between the core 52 and the doped layer 65.

[0094] Each emitting layer 60 is, for example, a quantum well. In particular, the thickness of each emitting layer 60 is, at every point of the emitting layer 60, between 1 nm and 200 nm.

[0095] When several superimposed emitting layers 60 are present, these emitting layers are, in particular, separated from each other by semiconductor barrier layers, each barrier layer having a band gap value strictly greater than the band gap value of the emitting layers between which the barrier layer is interposed.

[0096] The thickness of each emitting layer 60 is measured, at any point of the emitting layer 60, along a direction perpendicular to the surface of the core 52 at the point on the surface of the core 52 which is closest to the point of the emitting layer 60 under consideration.

[0097] For example, the thickness of each emitting layer 60 at a point of the emitting layer 60 that is aligned with a point of the core 52 along the normal direction N is measured along the normal direction N. The thickness of each emitting layer 60 at a point of the emitting layer 60 that is aligned in a plane perpendicular to the normal direction with a point of the core 52 is measured along a direction perpendicular to the facet closest to the core 52.

[0098] Each emitting layer 60 is, for example, made of InGaN.

[0099] The doped layer 65 at least partially covers the emitting layer(s) 60.

[0100] The doped layer 65 is made of a semiconductor material.

[0101] The 65-doped layer plays the role of an n-doped or p-doped layer in the LED structure.

[0102] The doping type (n or p) of the doped layer 65 is opposite to the doping type (p or n) in the nucleus 52. For example, the doped layer 65 is p-doped.

[0103] The doped layer 65 is, for example, made of GaN.

[0104] The first and second contacts 49A, 49B are electrically connected to the control circuit 25 and are configured to allow the control circuit 25 to generate an electric current through each semiconductor structure 47 by imposing an electrical potential difference between each first contact 49A and each second contact 49B. In particular, the contacts 49A, 49B are configured so that this electric current passes through the cover layer 55.

[0105] For example, each first contact 49A is electrically connected, through the substrate 12, to the core 52 of a corresponding semiconductor structure 47 while each second contact 49B is electrically connected to the doped layer 65 of the same semiconductor structure 47.

[0106] According to the embodiment shown in the figure 3 , the emitter 40 has a single first contact 49A connected to the core 52 of each semiconductor structure 47 and a single second contact 49B electrically connected to the doped layer 65 of each semiconductor structure 47.

[0107] In particular, the single second contact 49B is electrically connected through the substrate 12 to the block 50, which is itself electrically connected to the doped layer 65 of each semiconductor structure 47.

[0108] In particular, each semiconductor structure 47 is embedded in the block 50.

[0109] Block 50 is supported by substrate 12, specifically by the first face 30. In the embodiment shown in the figure 3 , block 50 is supported by insulating layer 57.

[0110] Block 50, for example, contains a layer 72 of a conductive and transparent or semi-transparent material that makes contact with layer 65 and is connected to electrode 49B. This material is, for example, ITO (indium tin oxide), graphene, or a zinc oxide doped with gallium or aluminum. Layer 72 is, for example, a conformal layer covering the semiconductor structure(s) 47 of the emitter 15A, 15B, 15C under consideration.

[0111] Block 50, for example, also contains a mass 73 of a transparent planarizing material such as SiO2 or a transparent polymer.

[0112] It should be noted that the materials used for block 50 are likely to vary.

[0113] Block 50 has, in particular, a height greater than or equal to the height of each semiconductor structure 47, measured along the normal direction N.

[0114] Block 50 is in contact with each doped layer 65. Furthermore, block 50 is not in contact with the nuclei 52. In particular, each cover layer 55 is interposed between the nucleus 52 of the same semiconductor structure 47 and block 50.

[0115] Each converter 45 is interposed in the normal direction N between the corresponding emitter 40 and the polarizer 20. For example, each emitter 40 of a first or second emitting element 15A, 15B is interposed between the corresponding converter 45 and the substrate 12.

[0116] Each 45 converter is made of a conversion material.

[0117] The conversion material is configured to convert the second radiation R2 emitted by the emitter 40 belonging to the same emitting element 15A, 15B into the corresponding first radiation R1A, R1B. In other words, the conversion material is configured to be excited by the second radiation R2 and to emit the first radiation R1A, R1B in response.

[0118] The second radiation R2 exhibits a second range of wavelengths. This second range is, for example, distinct from the first range. In particular, the second range has a second average wavelength, which is different from the first average wavelength. Specifically, the second average wavelength is strictly greater than the first average wavelength.

[0119] However, embodiments in which the second beach is identical to the first beach are also conceivable.

[0120] The conversion material is, for example, a semiconductor material.

[0121] For example, the conversion material is chosen from the set consisting of: CdSe, CdTe, ZnSe, ZnTe, InP, InPZnS, Ag2S, CulnS, CulnSe, AgInS2, AgInSe2, or InPZnXSeXySy. However, other types of materials are possible.

[0122] In other embodiments, the conversion material is a non-semiconductor material such as an inorganic garnet. For example, the conversion material is a doped yttrium-aluminum garnet. However, other types of non-semiconductor conversion materials, including other garnets, are possible.

[0123] In particular, the conversion material can be an inorganic phosphorus.

[0124] Yttrium aluminum garnet-based particles (e.g., YAG:Ce), aluminum terbium garnet-based particles, TAG, (e.g., TAG:Ce), silicate-based particles (e.g., SrBaSiO4:Eu), sulfide-based particles (e.g., SrGa2S4:Eu, SrS:Eu, CaS:Eu, etc.), nitride-based particles (e.g., Sr2Si5N8:Eu, Ba2Si5N8:Eu, etc.), oxynitride-based particles (e.g., Ca-α-SiAlON:Eu, SrSi2O2N2:Eu, etc.), fluoride-based particles (e.g., K2SiF6:Mn, Na2SiF6:Mn, etc.) are examples of inorganic phosphors.

[0125] Many other conversion materials can be used, such as doped aluminates, doped nitrides, doped fluorides, doped sulfides, or doped silicates.

[0126] The conversion material is, for example, doped with rare earth elements, alkaline earth metals, or transition metals. Cerium, for example, is sometimes used for doping yttrium-aluminum garnets.

[0127] The converter 45 includes, for example, a set of P particles made of the conversion material. These P particles are sometimes called "luminophores".

[0128] In particular, the converter 45 comprises a plurality of layers of P particles, these layers of P particles being superimposed along the normal N direction.

[0129] The converter 45 is, in particular, configured so that the first radiation R1A, R1B has linear polarization.

[0130] In particular, each first radiation R1A, R1B has a polarization direction DP, this polarization direction being for example perpendicular to the normal direction N. In particular, the polarization direction DP is parallel to the direction D1, however the orientation of the polarization direction DP is likely to vary in the plane formed by the directions D1 and D2.

[0131] In particular, "parallel" is understood to mean parallelism to within 10 degrees (°), for example within 5°, especially within 1° or better.

[0132] Each particle P has a first dimension along the first direction D1 and a second dimension along the second direction D2.

[0133] Each first or second dimension is between 1 nm and 1000 nm.

[0134] Furthermore, a ratio between, in the numerator, the first dimension and, in the denominator, the second dimension, is strictly greater than 1, in particular between 2 and 1000. For example, the ratio is greater than or equal to 4.5.

[0135] Each particle P is, for example, a rod, a tube or a wire extending along the first direction D1.

[0136] Alternatively, each particle P is a plate extending in a plane perpendicular to the second direction D2.

[0137] Alternatively or in addition, each particle P is, for example, a quantum dot.

[0138] According to one embodiment, each particle P comprises a core made of the conversion material and a shell surrounding the core. The core has, for example, a diameter less than or equal to 50 nm, in particular less than or equal to 20 nm.

[0139] The shell is, for example, made of a semiconductor material having a band gap value strictly greater than the band gap value of the conversion material, or alternatively of an electrically insulating material.

[0140] The P particles are, for example, arranged along a set of eigenlines. Each eigenline is, for example, parallel to the DP polarization direction.

[0141] In particular, proper lines are parallel to each other.

[0142] The distance between two consecutive eigenlines is, for example, between 1 nm and 10 µm.

[0143] A plurality of particles P are arranged along each eigenline.

[0144] According to one embodiment, the particles P are arranged on at least one plane perpendicular to the normal direction N, for example on several parallel planes, the particles of each plane forming a two-dimensional lattice in that plane.

[0145] The two-dimensional network is, for example, a rectangular mesh network. Alternatively, the network is a hexagonal, square, or even rhombic mesh network.

[0146] It should be noted that embodiments in which the P particles are arranged along a set of parallel eigenlines without forming a lattice in the corresponding plane are also envisaged.

[0147] The quarter-wave plate 48 of each emitting element 15A, 15B, 15C is interposed between the emitter 40 and the polarizer 20. For example, the quarter-wave plate 48 is in contact with the block 50, in particular with a face of the block 50 delimiting the block 50 in the normal direction N.

[0148] In particular, each converter 45 is carried by the corresponding quarter-wave plate 48, and is therefore interposed between the quarter-wave plate 48 and the polarizer 20 in the normal direction N. Thus, the quarter-wave plate 48 is intended to be crossed by the second radiation R2 when the second radiation R2 leaves the emitter 40 before reaching the corresponding converter 45 (in the case of a first or second emitting element 15A, 15B) or the polarizer 20 (in the case of a third emitting element 15C).

[0149] The quarter-wave plate 48 has a slow axis. The slow axis is perpendicular to the normal direction N. Furthermore, the slow axis forms an angle of 45° with the polarization direction DP.

[0150] The quarter-wave plate 48 is configured to introduce, in the second radiation R2, a phase shift equal to one quarter of π, or 90°, between the component along the slow axis of the second radiation R2 and the component along a direction, called the fast axis, perpendicular to the slow axis and to the normal direction N. In particular, the quarter-wave plate 48 is configured to delay the component along the slow axis.

[0151] According to one variant, shown on the figure 2 The quarter-wave plate 48 is interposed between the converter 45 and the polarizer 20. In this case, the quarter-wave plate 48 is configured to introduce, in the first radiation R1A, R1B, a phase shift equal to one quarter of π, or 90°, between the component along the slow axis of the first radiation R1A, R1B and the component along a direction, called the fast axis, perpendicular to the slow axis and to the normal direction N. In particular, the quarter-wave plate 48 is configured to delay the component along the slow axis.

[0152] The quarter-wave plate 48 is made of a birefringent material.

[0153] The quarter-wave plate 48 is, for example, made of silica SiO2, notably quartz or spar.

[0154] The quarter-wave plate 48 is, for example, common to each emitting element 15A, 15B, 15C. For example, the quarter-wave plate 48 is a single plate between which and the substrate 12 each emitter 40 is interposed.

[0155] As depicted on the figures 1 , 2 And 3 , the quarter-wave blade 48 delimits, for example, for each wall 70, a trench crossing the quarter-wave blade 48 along the normal direction N and accommodating the corresponding wall 70.

[0156] Polarizer 20 is configured to be crossed in the normal direction N by each first radiation R1A, R1B, R1C.

[0157] For example, the polarizer 20, each converter 45 and the corresponding emitter 40 are arranged along the same straight segment parallel to the normal direction N.

[0158] The polarizer 20 is, for example, a plate extending in a plane perpendicular to the normal direction N.

[0159] In particular, the polarizer 20 is opposite the first face 30 of the substrate 12, each emitting element 15A, 15B, 15C being interposed between the first face 30 and the polarizer 20.

[0160] The polarizer 20 has one axis.

[0161] The axis of the polarizer 20 is parallel to the polarization direction DP. The axis of the polarizer 20 is, for example, parallel to the first direction D1.

[0162] The polarizer 20 is configured to be traversed in the normal direction N by the component along the axis of the polarizer 20 of each first radiation R1A, R1B, R1C, and to prevent propagation in the normal direction N of the component of each first radiation R1A, R1B, R1C in a direction perpendicular to the normal direction N and to the axis of the polarizer 20.

[0163] Polarizer 20 is, for example, a metallic absorption polarizer, comprising metallic wires perpendicular to the DP polarization direction.

[0164] The wall assembly 70 is configured to prevent each first radiation R1A, R1B, R1C emitted by an emitting element 15A, 15B, 15C from reaching another emitting element 15A, 15B, 15C. In addition, the wall assembly 70 is configured to prevent each second radiation R2 emitted by an emitting element 15A, 15B, 15C from reaching another emitting element 15A, 15B, 15C, in particular from reaching the converter 45 of this other emitting element 15A, 15B, 15C.

[0165] For example, the set of walls 70 delimits a set of cells 75 in a plane perpendicular to the normal direction N, each cell 75 accommodating at least the quarter-wave plate 48, for example the converter 45 and the quarter-wave plate 48, in particular the converter 45, the quarter-wave plate 48 and the emitter 40 of a single emitting element 15A, 15B, 15C.

[0166] According to one embodiment, each wall 70 extends along the normal direction N from the first face 30. Alternatively, each wall 70 is accommodated between two adjacent quarter-wave plates 48, but does not extend between the emitters 40 corresponding to these quarter-wave plates 48. For example, each wall 70 is provided in the layer formed by the quarter-wave plates 48.

[0167] It should be noted that embodiments in which at least one wall 70 extends from the first face 30 in a direction distinct from the normal direction N are conceivable.

[0168] Each wall 70 is configured to prevent each R1A, R1B, R1C, R2 radiation from passing through the barrier, including in a direction perpendicular to the normal direction.

[0169] Each wall 70 is, for example, configured to reflect the radiation(s) R1A, R1B, R1C, R2 emitted by the emitting element 15A, 15B, 15C accommodated in the cell(s) 75 delimited by the wall 70.

[0170] Each wall 70 is, for example, made of a metallic material such as aluminum, or silver.

[0171] Alternatively, each wall 70 is configured to absorb each R1A, R1B, R1C, R2 radiation reaching the wall 70.

[0172] The control circuit 25 is electrically connected to each first or second contact 49A, 49B and configured to impose a potential difference between the contacts 49A, 49B of each transmitter element 15A, 15B, 15C so as to generate an electric current through the transmitter 40 of said transmitter element 15A, 15B, 15C.

[0173] The control circuit 25 includes, for example, a set of components, including transistors, CMOS (from the English "Complementary Metal-Oxide Semiconductor") carried by the substrate 12, especially when the substrate 12 is a semiconductor such as silicon.

[0174] As an alternative or complement, particularly when the substrate 12 is electrically insulating, the control circuit 25 includes a set of thin-film transistors. A thin-film transistor is a type of field-effect transistor formed by the successive deposition of several thin layers (a few hundred nanometers thick).

[0175] Thanks to the use of a converter 45 emitting a first radiation R1A, R1B linearly polarized along a direction DP parallel to the axis of the polarizer 20, the presence of the polarizer 20 does not cause a loss of intensity of this first radiation R1A, R1B.

[0176] The performance of the optoelectronic device 10 is therefore improved compared to other optoelectronic devices 10 comprising an emitting element and a polarizer.

[0177] Furthermore, when the quarter-wave plate 48 is placed between the converter 45 and the polarizer 20, its presence reduces the intensity of stray light originating from outside the optoelectronic device 10 and reflected off the emitting elements 15A, 15B, 15C and / or the substrate 12. This unpolarized stray light would have its intensity greatly reduced by its initial passage through the polarizer 20, then through the quarter-wave plate 48, followed by reflection off the substrate or elements 15A, 15B, 15C, and then another passage through the quarter-wave plate 48 before reaching the polarizer 20, which would then block the vast majority of it. The contrast of the optoelectronic device 10, particularly when it is a screen, is thus improved.

[0178] Particles P exhibiting a ratio strictly greater than 1, in particular between 2 and 1000, between the first and second dimensions make it possible to obtain a converter 45 emitting a first radiation R1A, R1B linearly polarized easily, in particular via the deposition of these particles under an electric field oriented along the first direction D1.

[0179] Other methods of obtaining converter 45 are also conceivable, such as optical lithography or grafting.

[0180] When the third emitting elements 15C are not equipped with a converter 45, the intensity of the radiation R1C is reduced by 50% as it passes through the polarizer 20. This can be useful when the radiation R2, R1C emitted by the corresponding emitter 40 is very intense compared to the intensity of the radiations R1A, R1B, particularly for controlling the output of the emitting elements 15A, 15B, and 15C if they are all illuminated simultaneously. This is especially helpful when the radiation R2 is blue, in order to achieve a good white balance.

[0181] The presence of the walls 70 helps to avoid crosstalk between neighboring emitting elements 15A, 15B, 15C, and therefore to better control the colors emitted by the optoelectronic device 10.

[0182] Grafting is a process for attaching particles (P) to a surface, in which the surface is coated with a layer specifically designed to bind the P particles. For example, the surface is functionalized using molecules that are surface-bound and designed to allow each P particle to bind to the surface via the molecule. In particular, one end of each molecule is designed to bind to the surface, and the other end is designed to bind to a P particle of the conversion material, so that the P particle is attached to the surface by the molecule.

[0183] These molecules are sometimes called "surface agents", "bifunctional ligands", "polyfunctional ligands", "binders", "linkers", "coating agents", etc.

[0184] It should be noted that any functional organic molecule having at least two functional reactive groups can be used as molecule M in the present invention.

[0185] Examples of M molecules can be selected, for example, from the "organosilane" group, the "thiol" group, the "acrylate" group, and the "amine" group.

[0186] The "organosilane" group includes, for example, the molecules 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane and allyltrimethoxysilane.

[0187] The "thiol" group includes, for example, the molecules 1,6-hexanedithiol, trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionate).

[0188] Examples of acrylates include poly(ethylene glycol)diacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate.

[0189] The molecules of the "amine" group include bis(hexamethylene)triamine, bis(3-aminopropyl)amine, 3,3'-diamino-N-methyldipropylamine, etc.

[0190] The length of each molecule is chosen to impose an average distance between the particles. Specifically, the length of each molecule is chosen to limit the risk of absorption, by a particle P, of a first radiation R1A, R1B emitted by a neighboring particle P.

[0191] It should be noted that embodiments in which several layers of molecules and several layers of P particles are stacked can be considered. For example, a layer of molecules is used to attach a first layer of P particles, with each subsequent layer of P particles being attached to an underlying layer of P particles by a layer of molecules interposed between the two layers.

[0192] It should be noted that, although the optoelectronic device 10 has been described previously in a case where each emitter 40 comprises one or more semiconductor structures, in particular of the LED type, other embodiments are conceivable.

[0193] For example, each emitter 40 is likely to include a light source emitting the second radiation R2, for example, and a liquid crystal system suitable for switching between a configuration allowing the second radiation R2 to pass through the system to exit the emitter 40 and a configuration preventing the second radiation R2 from exiting the emitter 40.

[0194] In particular, the light source is, for example, common to all emitters 40. Alternatively, each emitter 40 has a light source separate from the other light sources.

[0195] It should also be noted that embodiments in which the polarization direction DP forms a non-zero angle with the axis of the polarizer 20 are also possible. This can, in particular, allow for a better balance between the different radiations R1A, R1B, R1C at the output of the polarizer 20.

[0196] In general, for example, the polarizer 20 is intended to be positioned during a polarizer positioning step in a manufacturing process for the electronic device 10. During this step, a light intensity of at least one radiation R1A, R1B, or R1C is measured, and the polarizer 20 is positioned, specifically rotated around an axis parallel to the normal direction N, according to the measured light intensity. This ensures that the axis of the polarizer 20 is effectively oriented parallel to the polarization direction DP, even if this polarization direction DP is not exactly the one expected due to an inaccuracy during the manufacturing of the converters 45.

[0197] Furthermore, embodiments in which at least one converter 45 generates linearly polarized R1A, R1B or R1C radiation without the converter 45 having a set of P particles are also conceivable.

[0198] Furthermore, it turns out that even without the quarter-wave plate, linear polarization of the R1A and R1B radiations is advantageous, notably because it improves the perceived intensity of these R1A and R1B radiations for a user of the optoelectronic device, while also reducing the relative intensity of the R1C radiation. This allows for modification of the relative balance of these intensities, particularly in the context of white balance.

[0199] It should be noted that, although the emitting elements 15C have been described above as not having a converter 45, embodiments in which each emitting element 15C has its own converter to convert the second radiation R2 into the first radiation R1C are also conceivable.

[0200] In this case, the second radiation R2 differs from the first radiation R1C, for example at least in that the wavelength range of the first radiation R1C is distinct from the wavelength range of the second radiation R2. In particular, the second radiation R2 is ultraviolet radiation.

[0201] It should be noted that distinct ranges are likely to exhibit non-zero overlap.

[0202] The first R1C radiation, for example, exhibits elliptical polarization.

[0203] When each 15C emitting element has a 45 converter, it is possible to obtain a better balance of the colors emitted by the different 15A, 15B, 15C emitting elements.

[0204] Alternatively, the first radiation R1C emitted by the polarizer of the emitting element 15C has linear polarization along a direction parallel to the axis of the polarizer 20. This can allow for better emission efficiency of the first radiation R1C, since it is not attenuated by the polarizer 20.

[0205] A second example of an optoelectronic device 10 will now be described. The elements identical to the first example are not described again. Only the differences are highlighted.

[0206] The optoelectronic device 10 includes a plurality of polarizers 20. In particular, the optoelectronic device includes a polarizer 20 for each emitting element 15A or 15B, and optionally for each emitting element 15C.

[0207] Each polarizer 20 is configured to be crossed by the first radiation R1A, R1B or R1C of the emitting element 15A, 15B or 15C associated with the polarizer 20. In particular, the emitting element 15A, 15B or 15C associated with the polarizer 20 is interposed in the normal direction N between the polarizer 20 considered and the substrate 12.

[0208] The axis of each polarizer 20 is parallel to the DP polarization direction of the corresponding emitting element 15A, 15B, 15C.

[0209] The DP polarization direction of each 15A emitter element is different from the DP polarization direction of each 15B emitter element and / or each 15C emitter element. Furthermore, the DP polarization direction of each 15B emitter element is different from the DP polarization direction of each 15C emitter element.

[0210] In particular, the angle between the DP polarization direction of each emitting element 15A and the DP polarization direction of each emitting element 15B or 15C is, for example, equal to 90°, within 5 degrees. However, this angle is subject to variation.

[0211] An angle between the DP polarization direction of each emitting element 15B and the DP polarization direction of each emitting element 15C is, for example, equal to 90°, within 5 degrees. However, this angle is subject to variation.

[0212] The P particles of each emitting element 15A, 15B, 15C are configured so that the corresponding first radiation R1A, R1B, R1C is linearly polarized along the polarization direction DP of the polarizer 20 associated with the emitting element 15A, 15B, 15C considered.

[0213] The second example makes it possible in particular to limit crosstalk between neighboring emitting elements 15A, 15B, 15C, since the first radiation R1A, R1B, R1C emitted by an emitting element 15A, 15B, 15C is attenuated by the polarizers 20 associated with the other emitting elements 15A, 15B, 15C. The resolution of the optoelectronic device 10 is therefore improved.

[0214] It should be noted that, when the quarter-wave plate 48 is interposed between the converter 45 and the polarizer 20, the polarization direction DP is, for example, perpendicular to the axis of the polarizer 20. In particular, the polarization direction DP is parallel to the second direction D2. GLOSSARY DOPING

[0215] Doping is defined as the presence, in a material, of impurities that provide free charge carriers. Impurities are, for example, atoms of an element that is not naturally present in the material.

[0216] When impurities increase the volume density of holes in the material, compared to undoped material, the doping is of the p type. For example, a gallium nitride layer, GaN, is p-doped by adding magnesium (Mg) atoms.

[0217] When impurities increase the volume density of free electrons in the material, compared to the undoped material, the doping is of the n type. For example, a layer of gallium nitride, GaN, is n-doped by adding silicon (Si) atoms. LED STRUCTURE

[0218] An LED structure is a semiconductor structure comprising several semiconductor zones forming a PN junction and configured to emit light when an electric current flows through the different semiconductor zones.

[0219] A two-dimensional structure comprising an n-doped layer, a p-doped layer, and at least one emitting layer is an example of an LED structure. In this case, each emitting layer is interposed, along the normal direction D, between the n-doped layer and the p-doped layer.

[0220] In one embodiment, each emitting layer has a band gap value strictly less than the band gap value of the n-doped layer and strictly less than the band gap value of the p-doped layer. For example, the n-doped layer and the p-doped layer are GaN layers, and each emitting layer is an InGaN layer.

[0221] The emitting layer is, for example, undoped. In other embodiments, the emitting layer is doped.

[0222] A quantum well is a specific example of an emitting layer with a band gap value lower than the band gap values ​​of n- and p-doped layers. QUANTUM WELL

[0223] A quantum well is a structure in which quantum confinement occurs, in one direction, for at least one type of charge carrier. The effects of quantum confinement occur when the dimension of the structure along this direction becomes comparable to or smaller than the de Broglie wavelength of the carriers, which are usually electrons and / or holes, leading to energy levels called "energy sub-bands".

[0224] In such a quantum well, carriers can only exhibit discrete energy values ​​but are generally able to move within a plane perpendicular to the direction in which confinement occurs. The energy values ​​available to the carriers, also called "energy levels," increase as the dimensions of the quantum well decrease along the direction in which confinement occurs.

[0225] In quantum mechanics, the "de Broglie wavelength" is the wavelength of a particle when the particle is considered as a wave. The de Broglie wavelength of electrons is also called the "electronic wavelength." The de Broglie wavelength of a charge carrier depends on the material of which the quantum well is made.

[0226] An emitting layer whose thickness is strictly less than the product of the electronic wavelength of the electrons in the semiconductor material of which the emitting layer is made and five is an example of a quantum well.

[0227] Another example of a quantum well is an emitting layer whose thickness is strictly less than the product of the de Broglie wavelength of excitons in the semiconductor material from which the emitting layer is made and five. An exciton is a quasiparticle consisting of an electron and a hole.

[0228] In particular, a quantum well often has a thickness between 1 nm and 200 nm. SEMICONDUCTIVE MATERIAL

[0229] The expression "band gap value" should be understood as the value of the band gap between the valence band and the conduction band of the material.

[0230] The band gap value is, for example, measured in electron volts (eV).

[0231] The valence band is defined as, among the energy bands that are allowed for electrons in the material, the band that has the highest energy while being completely filled at a temperature less than or equal to 20 Kelvin (K).

[0232] A first energy level is defined for each valence band. The first energy level is the highest energy level in the valence band.

[0233] The conduction band is defined as, among the energy bands that are allowed for electrons in the material, the band that has the lowest energy while not being completely filled at a temperature less than or equal to 20 K.

[0234] A second energy level is defined for each conduction band. The second energy level is the highest energy level of the conduction band.

[0235] Thus, each band gap value is measured between the first energy level and the second energy level of the material.

[0236] A semiconductor material is a material with a band gap value strictly greater than zero and less than or equal to 6.5 eV.

[0237] A direct bandgap semiconductor is an example of a semiconductor material. A material is considered to have a "direct bandgap" when the minimum of the conduction band and the maximum of the valence band correspond to the same charge carrier momentum. A material is considered to have an "indirect bandgap" when the minimum of the conduction band and the maximum of the valence band correspond to different charge carrier momentum values.

[0238] Each semiconductor material can be chosen, for example, from the set of III-V semiconductors, including element III nitrides, II-VI semiconductors, or IV-IV semiconductors.

[0239] III-V semiconductors include InAs, GaAs, AlAs and their alloys, InP, GaP, AIP and their alloys, and nitrides of element III.

[0240] II-VI semiconductors include CdTe, HgTe, CdSe, HgSe, and their alloys.

[0241] IV-IV semiconductors include Si, Ge and their alloys. THREE-DIMENSIONAL STRUCTURE

[0242] A three-dimensional structure is a structure that extends along a principal direction. The three-dimensional structure has a length measured along the principal direction. The three-dimensional structure also has a maximum lateral dimension measured along a lateral direction perpendicular to the principal direction, the lateral direction being the direction perpendicular to the principal direction along which the dimension of the structure is greatest.

[0243] The maximum lateral dimension is, for example, less than or equal to 10 micrometers (µm), and the length is greater than or equal to the maximum lateral dimension. Advantageously, the maximum lateral dimension is less than or equal to 2.5 µm.

[0244] The maximum lateral dimension is, in particular, greater than or equal to 10 nm.

[0245] In specific embodiments, the length is greater than or equal to twice the maximum lateral dimension, for example it is greater than or equal to five times the maximum lateral dimension.

[0246] The principal direction is, for example, the normal direction D. In this case, the length of the three-dimensional structure is called "height" and the maximum dimension of the three-dimensional structure, in a plane perpendicular to the normal direction D, is less than or equal to 10 µm.

[0247] The maximum dimension of the three-dimensional structure, in a plane perpendicular to the normal direction D, is often called "diameter" regardless of the shape of the cross-section of the three-dimensional structure.

[0248] For example, every three-dimensional structure is a microwire. A microwire is a cylindrical three-dimensional structure.

[0249] In one specific embodiment, the microwire is a cylinder extending along the normal direction D. For example, the microwire is a cylinder with a circular base. In this case, the diameter of the base of the cylinder is less than or equal to half the length of the microwire.

[0250] A microwire whose maximum lateral dimension is less than 1 µm is called a "nanowire".

[0251] A pyramid extending along the normal direction D from substrate 12 constitutes another example of a three-dimensional structure.

[0252] A cone extending along the normal direction D is another example of a three-dimensional structure.

[0253] A truncated cone or a truncated pyramid extending along the normal direction D constitutes yet another example of a three-dimensional structure. POLARIZATION

[0254] The polarization of radiation is a property of that radiation relating to the time phase difference between the components of the electric field of each wave composing that radiation along two directions perpendicular to each other and perpendicular to the direction of propagation of that radiation.

[0255] When the two components are in phase temporally, the polarization is said to be "rectilinear". This is reflected by the existence of a direction, called the polarization direction, to which the electric field vector of the wave is parallel at every instant.

[0256] When the two components have a time phase difference other than zero, the polarization is said to be "elliptic". In the particular case where the two components have the same amplitude and are phase-shifted by 90 degrees (°), the polarization is then said to be "circular". QUANTUM BOX

[0257] A quantum dot is a structure in which quantum confinement occurs in three spatial dimensions.

[0258] To give an order of magnitude, a particle P with a maximum dimension between 1 nm and 1 µm, and made of a semiconductor conversion material, constitutes an example of a quantum dot.

Claims

1. An optoelectronic device (10) comprising at least a first emitting element (15A)and a polariser (20), each first emitting element (15A) being configured to emit a first radiation (R1A) having a first range of wavelengths, the polariser (20) being configured to be traversed at least partially by the first radiation (R1A), each first emitting element (15A) comprising an emitter (40) and a converter (45) the emitter (40) being configured to emit a second radiation (R2) having a second range of wavelengths, the second range being distinct from the first range, the converter (45) being configured to at least partially absorb the second radiation (R2) and to emit the first radiation (R1A) in response, the polariser (20) having an axis, each converter (45) being interposed between the corresponding radiation emitter (40) and the polariser (20), characterised in that each converter (45) being configured so that the first radiation (R1A) is rectilinearly polarised along a polarisation direction (DP), characterized in that: - the second radiation (R2) has an elliptical polarisation, - each first emitting element (15A) comprises a quarter-waveplate (48) having a slow axis forming an angle of 45 degrees with the axis of the polariser (20), - the quarter-waveplate (48) being either interposed between the emitter (40) and the converter (45).

2. The optoelectronic device according to claim 1, wherein the polarisation direction (DP) is parallel to the axis of the polariser (20) when the quarter-waveplate (48) is interposed between the emitter (40) and the converter (45).

3. The optoelectronic device according to claim 4, wherein each first emitting element (15A) comprises a quarter-waveplate (48) interposed between the converter (45) and the polariser (20), the quarter-waveplate (48) having a slow axis forming an angle of 45 degrees with the axis of the polariser (20).

4. The optoelectronic device according to any one of claims 1 to 3, wherein the polariser (20) is configured to be traversed by each first radiation (R1A) in a normal direction (N) perpendicular to the axis of the polariser (20), each converter (45) comprising a set of particles (P) having a first dimension in a first direction (D1) parallel to the polarisation direction (DP) and a second dimension in a second direction (D2) perpendicular to the polarisation direction (DP) and to the normal direction (N), a ratio between, in the numerator, the first dimension, and in the denominator, the second dimension, being greater than or equal to two.

5. The optoelectronic device according to claim 6, wherein each first or second dimension is between 1 nanometer and 1,000 nanometers.

6. The optoelectronic device according to any according to claims 1 to 5, wherein each emitter (40) comprises a light-emitting diode (47).

7. The optoelectronic device according to according to any one of claims 1 to 6, wherein each emitter (40) comprises a liquid crystal.

8. The optoelectronic device according to any one of claims 1 to 7, further comprising at least one second emitting element (15C), each second emitting element (15C) being configured to emit a third radiation (R1C, R2) having a third wavelength range different from the first range, the polariser (20) being configured to be traversed at least partially by the third radiation (R1C, R2).

9. The optoelectronic device according to claim 8, wherein the third radiation (R1C, R2) is identical to the second radiation (R2), each second emitting element (15C) comprising a radiation emitter (40), the second emitting element (15C) being without a converter (45).

10. The optoelectronic device according to any one of claims 1 to 9, comprising a plurality of emitting elements (15A, 15B, 15C), the optoelectronic device (10) further comprising at least one barrier (70) interposed between each emitting element (15A, 15B, 15C) and each other emitting element (15A, 15B, 15C), the barrier (70) being configured to prevent each radiation (R1A, R1B, R1C, R2) from passing through the barrier (70).

11. The optoelectronic device according to any one of claims 1 to 10, comprising a plurality of polarisers (20), each polariser (20) being associated with a corresponding emitting element (15A, 15B, 15C), the polariser (20) being configured to be traversed at least partially by the first radiation (R1A, R1B) emitted by the corresponding emitting element (15A, 15B), the polarisation direction (DP) of at least one emitting element (15A, 15B) being different from the polarisation direction (DP) of at least one other emitting element (15A, 15B), the polarisation direction (DP) of each emitting element (15A, 15B) associated with a polariser (20) being parallel to the axis of the corresponding polariser.

12. The optoelectronic device according to any one of claims 1 to 11, comprising a plurality of emitting elements (15A, 15B), wherein the polarisation direction (DP) of at least one emitting element (15A, 15B) is different from the polarisation direction (DP) of at least one other emitting element (15A, 15B), the electronic device comprising a polariser (20) configured to be traversed at least partially by the first radiation (R1A, R1B) emitted by each of the two emitting elements (15A, 15B) in question.

13. The optoelectronic device according to claim 11 or 12, wherein an angular difference between the polarisation directions (DP) of at least two emitting elements (15A, 15B) is between 85 degrees and 95 degrees.