Optoelectronic devices with light-emitting diodes having enhanced light extraction

Abstract

To provide an opto-electronic device with a light-emitting diode formed by a micro wire or a nanowire of a semiconductor.SOLUTION: An opto-electronic device 5 comprises: a support 10 having a surface 12; a light-emitting diode DEL that is loaded on the surface and that has a wire and a cone-shaped or truncated cone-shaped semiconductor element 16; and a sealing block 25 that is provided for each light-emitting diode and that covers the light-emitting diode by permitting at least partial transmission of radiation emitted by the light-emitting diode. The maximum thickness of the sealing block falls within the range of 1-30 μm. A cavity 37 exists between the sealing blocks for covering the adjacent light-emitting diodes. The opto-electronic device has a conductive layer 30 for covering the sealing block. A refraction index of the sealing block for covering at least one of the light-emitting diodes falls within the range of 1.3-1.6.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure generally relates to optoelectronic devices based on semiconductor materials and methods for manufacturing such optoelectronic devices. More specifically, the present invention relates to optoelectronic devices comprising a light-emitting diode formed by a ternary element, particularly a semiconductor micro-wire or nano-wire.

Background Art

[0002] With an optoelectronic device comprising a light-emitting diode, the optoelectronic device is understood to be a device adapted to convert an electrical signal into electromagnetic radiation, particularly a device for the emission of electromagnetic radiation, particularly light. As an example of a ternary element adapted to form a light-emitting diode, there is a micro-wire or nano-wire having a semiconductor material based on a compound mainly containing at least one group III element and one group V element, hereinafter referred to as a group III-V compound (for example, gallium nitride GaN).

Summary of the Invention

Problems to be Solved by the Invention

[0003] The light extraction efficiency (LEE) of an optoelectronic device is generally defined by the ratio of the number of photons exiting the optoelectronic device to the number of photons emitted by the light-emitting diode. It is desirable for the extraction efficiency of the optoelectronic device to be as high as possible.

[0004] A disadvantage of existing optoelectronic devices is that some of the photons emitted within each light-emitting diode do not exit the light-emitting diode.

[0005] Accordingly, one object of an embodiment is to at least partially address the disadvantages of the light-emitting diodes described above, particularly optoelectronic devices comprising micro-wires or nano-wires, and methods for manufacturing such optoelectronic devices.

[0006] A further object of an embodiment is to increase the extraction efficiency of the optoelectronic device.

[0007] A further object of the embodiment is to reduce the proportion of light that does not emerge from each light-emitting diode.

[0008] A further object of the embodiment is to reduce the proportion of the light emitted by the light-emitting diodes that is absorbed / captured by adjacent light-emitting diodes.

Means for Solving the Problems

[0009] One embodiment is an optoelectronic device, a support having a surface, a light-emitting diode placed on the surface and having a semiconductor element in the form of a wire, a cone, or a frustum of a cone, a sealing block provided for each light-emitting diode or group of light-emitting diodes, covering the light-emitting diode or group of light-emitting diodes through at least a portion of the radiation emitted by the light-emitting diode, and comprising wherein a maximum thickness of the sealing block is in the range of 1 μm to 30 μm, and there is a gap between the sealing blocks covering adjacent light-emitting diodes or adjacent groups of light-emitting diodes, the optoelectronic device further comprising a conductive layer covering the sealing block and in contact with each light-emitting diode, and providing an optoelectronic device characterized in that a refractive index of the sealing block covering at least one of the light-emitting diodes or one of the group of light-emitting diodes is in the range of 1.3 to 1.6.

[0010] A further embodiment is an optoelectronic device, a support having a surface, a light-emitting diode placed on the surface and having a semiconductor element in the form of a wire, a cone, or a frustum of a cone, a sealing block provided for each light-emitting diode or group of light-emitting diodes, covering the light-emitting diode or group of light-emitting diodes through at least a portion of the radiation emitted by the light-emitting diode, comprises, and the maximum thickness of the encapsulation block is in the range of 1 μm to 30 μm, and there are voids between the encapsulation blocks covering adjacent light-emitting diodes or adjacent groups of light-emitting diodes, the optoelectronic device further comprises a conductive layer covering the encapsulation block and in contact with each light-emitting diode, the optoelectronic device comprises, on at least one of the encapsulation blocks, a conformal dielectric layer covering the encapsulation block and at least partially passing the radiation emitted by the light-emitting diode, provided is an optoelectronic device, wherein the refractive index of the encapsulation block is in the range of 1.8 to 2.2, the thickness of the dielectric layer is in the range of 200 nm to 5 μm, and the refractive index of the dielectric layer is in the range of 1.3 to 1.6.

[0011] According to an embodiment, the dielectric layer is disposed between the conductive layer and the encapsulation block, or the conductive layer is disposed between the dielectric layer and the encapsulation block.

[0012] According to an embodiment, each semiconductor element is a group III-V compound.

[0013] According to an embodiment, each semiconductor element contains gallium nitride.

[0014] According to an embodiment, the average diameter of each semiconductor element is in the range of 200 nm to 2 μm, and the average diameter of each encapsulation block is in the range of 3 μm to 30 μm.

[0015] According to an embodiment, the optoelectronic device further comprises a phosphorescent layer covering the encapsulation block on at least one light-emitting diode.

[0016] According to an embodiment, the optoelectronic device further comprises a lens covering the encapsulation block, and there are voids between the lenses.

[0017] According to an embodiment, the optoelectronic device further comprises an angular filter covering the lens.

[0018] According to an embodiment, the angular filter does not at least partially pass visible light and has a layer traversed by the aperture.

[0019] A further embodiment provides a method of manufacturing an optoelectronic device comprising a support having a surface and a light-emitting diode mounted on the surface and having a semiconductor element in the form of a wire, cone or frustum of a cone. In the method, for each light-emitting diode or group of light-emitting diodes, a sealing block is formed that at least partially passes the radiation emitted by the light-emitting diode and covers the light-emitting diode or the group of light-emitting diodes, a conductive layer is formed in contact with each light-emitting diode covering the sealing block, the maximum thickness of the sealing block is in the range of 1 μm to 30 μm, there is a gap between the sealing blocks covering adjacent light-emitting diodes or adjacent groups of light-emitting diodes, and the refractive index of the sealing block covering at least one of the light-emitting diodes or one of the group of light-emitting diodes is in the range of 1.3 to 1.6.

[0020] A further embodiment is a method of manufacturing an optoelectronic device comprising a support having a surface and a light-emitting diode disposed on the surface and having a semiconductor element in the form of a wire, cone or frustum of a cone, wherein for each said light-emitting diode or group of light-emitting diodes, a sealing block is formed that covers the light-emitting diode or group of light-emitting diodes at least partially through the radiation emitted by the light-emitting diode, a conductive layer is formed covering the sealing block and in contact with each light-emitting diode, the maximum thickness of the sealing block being in the range of 1 μm to 30 μm, and there being a gap between the sealing blocks covering adjacent light-emitting diodes or adjacent groups of light-emitting diodes. The optoelectronic device comprises, in at least one of the sealing blocks, a conformal dielectric layer covering the sealing block and allowing at least part of the radiation emitted by the light-emitting diode to pass through, the refractive index of the sealing block being in the range of 1.8 to 2.2, the thickness of the dielectric layer being in the range of 200 nm to 5 μm, and the refractive index of the dielectric layer being in the range of 1.3 to 1.6.

[0021] According to an embodiment, in the method, a lens is formed covering the sealing block.

[0022] According to an embodiment, in the method, an integral structure having lenses each having a recess is formed, the integral structure is fixed to the support, and the sealing block is inserted into the recess.

Brief Description of the Drawings

[0023] The foregoing and other features and advantages are described in detail in the following specific embodiments given by way of non-limiting examples of the invention with reference to the accompanying drawings.

[0024]

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Embodiments for Carrying Out the Invention

[0025] Similar features are indicated by similar reference numerals in various drawings. In particular, structural and / or functional features common to various embodiments may have the same reference numerals and may have the same structural characteristics, dimensional characteristics, and material characteristics. For clarity, only operations and elements useful for understanding the embodiments described herein are shown and described in detail. In particular, means for applying a bias to the light-emitting diode of the optoelectronic device are known and not described.

[0026] In the following disclosure, unless otherwise indicated, when referring to absolute positions such as "front", "rear", "top", "bottom", "left", "right", etc., or words limiting relative positions such as "above", "below", "high", "low", etc., or words limiting directions such as "horizontal", "vertical", etc., this language refers to the orientation of the drawing or the optoelectronic device in its normal use position. Further, the expressions "a compound mainly formed from a material" or "a compound based on a material" are understood to mean that the compound has a proportion of 95% or more of the said material, and preferably this proportion is greater than 99%. The expressions "about", "substantially", "essentially" and "degree" represent within a range of 10% of the corresponding value, preferably within a range of 5%, unless otherwise specified. In the following disclosure, a "conductive layer" is understood to mean a layer having electrical conductivity, and an "insulating layer" is understood to mean a layer that electrically insulates.

[0027] The present disclosure relates to an optoelectronic device comprising a three-dimensional element, such as a wire, a cone or a frustum of a cone, in particular an element in the form of a micro-wire or a nano-wire.

[0028] The terms "micro-wire" or "nano-wire" represent a three-dimensional structure that is elongated in a preferential direction, and such a three-dimensional structure has at least two dimensions referred to as small dimensions within the range of 5 nm to 2.5 μm, preferably 50 nm to 2.5 μm, and a third dimension referred to as a large dimension that is at least 1 times, preferably at least 5 times, more preferably at least 10 times the small dimension. In certain embodiments, the small dimension can be substantially 1.5 μm or less, preferably within the range of 100 nm to 1.5 μm, more preferably within the range of 100 nm to 800 nm. In certain embodiments, the height of each micro-wire or nano-wire can be 500 nm or more, preferably within the range of 1 μm to 50 μm.

[0029] In the following disclosure, the term "wire" is used to represent "micro-wire or nano-wire". Preferably, the average line of the wire passing through the centroid of the cross-section in a plane perpendicular to the preferential direction of the wire is substantially straight and is hereinafter referred to as the "axis" of the wire.

[0030] FIG. 1 is a partial cross-sectional schematic view showing an embodiment of an optoelectronic device 5 including a light-emitting diode, and one light-emitting diode is shown.

[0031] FIG. 1 shows, from bottom to top, - a conductive support 10 having a bottom surface 11 and a top surface 12 (the top surface 12 is preferably flat at least at the position of the light-emitting diode), - a light-emitting diode DEL having, respectively, a wire 16 having side walls 18, a bottom end wall 19, and a top end wall 20, and a shell 22 having a stack of semiconductor layers that at least partially covers the side walls 18 and completely covers the bottom end wall 19 (one light-emitting diode is schematically shown in FIG. 1), - a conductive layer 24 provided for each light-emitting diode DEL, forming a first electrode, covering the shell 22 and in contact with the shell 22, the conductive layer 24 being placed between a portion of the shell 22 covering the bottom end wall 19 of the wire 16 and the support 10 and in contact with the support 10, - an insulating encapsulation block 25 provided for each light-emitting diode DEL, placed on the support 10, completely surrounding the light-emitting diode DEL, and in contact with the first electrode 24 along the entire side wall of the light-emitting diode DEL, the encapsulation block 25 having a top surface 26 and side walls 27, - an insulating layer 14 extending across the top surface 12 of the support 10 around the encapsulation block 25, - an insulating layer 28 provided for each light-emitting diode DEL, extending across the top surface 26 of the encapsulation block 25 and a part of the top end wall 20 of the wire 16 (the wire 16 has a protrusion 29 extending through the insulating layer 28 at the top end wall 20), - a conductive layer 30 forming a second electrode, extending across the associated encapsulation block 25, the associated insulating layer 28, and the insulating layer 14 between the encapsulation blocks 25 for each light-emitting diode, and in contact with the protrusion 29 of each light-emitting diode DEL, and - an insulating layer 32 covering the conductive layer 30, particularly covering the entire top surface 26 and the entire side walls 27 of the encapsulation block 25 shows a structure having

[0032] According to a further embodiment, the insulating layer 32 does not exist. According to a further embodiment, the insulating layer 32 is disposed between the conductive layer 30 and the sealing block 25.

[0033] In this embodiment, the light-emitting diodes DEL are connected in parallel to form a set of light-emitting diodes. As a variant, the electrodes 24 and 30 may be arranged to connect the light-emitting diodes differently.

[0034] According to an embodiment, the insulating layer 32 is in contact with the air 34. The front surface 36 of the optoelectronic device 5 is the surface that the observer sees. In particular, when the insulating layer 32 does not exist, it is the surface exposed to the air 34 of the sealing block 25, or when the insulating layer 32 exists, it is the surface exposed to the air 34 of the insulating layer 32. In particular, a gap 37 is provided between each pair of adjacent light-emitting diodes.

[0035] According to an embodiment, the material constituting the sealing block 25 has a refractive index, also referred to as a refractive index, that is strictly lower than the refractive index of the material constituting the wire 16 and strictly higher than the refractive index of the material constituting the insulating layer 32 with respect to the wavelength of the radiation emitted by the light-emitting diode DEL. The refractive index is a dimensionless number that characterizes the optical properties of a medium, particularly absorption and diffusion. The refractive index is equal to the real part of the complex optical index. The refractive index can be determined, for example, by a polarization analysis method. When the following disclosure refers to the refractive index, unless otherwise indicated, the refractive index is the refractive index with respect to the wavelength of the radiation emitted by the light-emitting diode DEL. According to an embodiment, the refractive index of the material constituting the insulating layer 32 is strictly lower than the refractive index of the material constituting the sealing block 25 and strictly higher than the refractive index of air.

[0036] The support 10 can correspond to a one-piece structure or can have a base covered by a conductive layer. The upper surface 12 is conductive and is formed, for example, of a metal such as aluminum, silver, copper, or zinc. The support 10 can have various conductive regions that are electrically insulated from each other. By this means, various light-emitting diodes can be individually addressed. According to an embodiment, the upper surface 12 can be reflective. Thus, the support 10 can have specular reflection. According to a further embodiment, the support 10 can have Lambertian reflection. To obtain a surface with Lambertian reflection, as one possibility, irregularities are formed on the conductive surface. For example, when the upper surface 12 corresponds to the surface of a conductive layer placed on the base, the upper surface 12 of the metal layer can be textured before depositing the metal layer so that it shows irregularities when deposited.

[0037] The wire 16 is at least partially formed from at least one semiconductor material. The wire 16 can be at least partially formed from a semiconductor material mainly containing a group III-V compound, for example, a group III-N compound. Examples of group III chemical elements include gallium (Ga), indium (In), or aluminum (Al). Examples of group III-N compounds include GaN, AlN, InN, InGaN, AlGaN, or AlInGaN. Further elements of group V, such as phosphorus or arsenic, can be further used. Generally speaking, the elements within the group III-V compound can be combined in various molar fractions. The wire 16 can contain a dopant. For example, regarding group III-V compounds, the dopant can be a P-type group II dopant such as magnesium (Mg), zinc (Zn), cadmium (Cd), and mercury (Hg), a P-type group IV dopant such as carbon (C), and an N-type group IV dopant such as silicon (Si), germanium (Ge), selenium (Se), sulfur (S), terbium (Tb), and tin (Sn), and can be selected from the group containing them.

[0038] The cross-section of wire 16 can have various shapes, for example, it can be elliptical, circular or polygonal, particularly triangular, rectangular, square or hexagonal. Thus, when the term "diameter" of the cross-section of the wire or the cross-section of the layer deposited on this wire is mentioned in this specification, this term is understood as a variable associated with the surface area of the desired structure in this cross-section, corresponding to the diameter of a disk having the same surface area as the cross-section of the wire, for example. The height of each wire 16 can be in the range of 250 nm to 50 μm. Each wire 16 can have an elongated semiconductor structure along an axis substantially perpendicular to the upper surface 12. Each wire 16 can have a general cylindrical shape. The axes of two adjacent wires 16 can be spaced 0.5 μm to 10 μm apart, preferably 1.5 μm to 6 μm apart. For example, the wires 16 can be regularly distributed, particularly according to an array of hexagons or squares.

[0039] The shell 22 can have - an active layer that at least partially covers the entire sidewall 18 and the lower end wall 19 of the associated wire 16, - an intermediate layer of a conductivity type opposite to that of the wire 16 covering the active layer, and - a connection layer covering the intermediate layer and covered by the electrode layer 24 and can have a laminate of a plurality of layers particularly including.

[0040] The active layer is the layer from which most of the radiation by the light-emitting diode DEL is emitted. According to an embodiment, the active layer can have confinement means such as a single quantum well or multiple quantum wells. The active layer is composed, for example, by alternately forming GaN layers with a thickness of 5 to 20 nm (for example, 8 nm) and InGaN layers with a thickness of 1 to 10 nm (for example, 2.5 nm). The GaN layers can be doped, for example, doped N-type or P-type. According to a further embodiment, the active layer can have, for example, one layer of InGaN with a thickness greater than 10 nm.

[0041] For example, the intermediate layer doped with P-type can correspond to a semiconductor layer or a stack of semiconductor layers, enabling a p-n junction or a pin junction, and the active layer is provided between the P-type intermediate layer of the p-n junction or pin junction and the N-type wire 16. The connection layer can correspond to a semiconductor layer or a stack of semiconductor layers, enabling the formation of an ohmic contact between the intermediate layer and the electrode 24. For example, the connection layer can be doped at a very high concentration with a conductivity type opposite to that of the wire 16 up to the modification of one or more semiconductor layers, for example, 10 20 atoms / cm 3 or more and can be doped with P-type. The stack of semiconductor layers can be formed from a ternary alloy, such as aluminum gallium nitride (AlGaN) or aluminum indium nitride (AlInN), to reliably and sufficiently disperse the electric carriers in the active layer and can have an electron blocking layer in contact with the active layer and the intermediate layer.

[0042] The electrodes 24 and 30 are each adapted to apply a bias to the active layer of the light-emitting diode DEL and to pass the electromagnetic radiation emitted by the light-emitting diode DEL. The material forming each electrode 24, 30 can be a transparent conductive material, such as indium tin oxide (i.e., ITO), pure zinc oxide, zinc oxide doped with aluminum, zinc oxide doped with gallium, graphene, or silver nanowires. For example, the thickness of each electrode layer 24, 30 is in the range of 5 nm to 200 nm, preferably 30 nm to 100 nm.

[0043] Each insulating layer 14, 28, 32 is a dielectric material, such as silicon oxide (SiO2), silicon nitride (Si x N y , where x is approximately 3 and y is approximately 4, for example, Si3N4), silicon oxynitride (especially SiO x N yIt can be formed of, for example, Si₂ON₂), aluminum oxide (Al₂O₃), hafnium oxide (HfO₂), or diamond, which has the general formula. For example, the thickness of each of the insulating layers 14 and 28 is in the range of 5 nm to 500 nm, for example, approximately 30 nm. Further, the insulating layer 32 can be formed of an organic material, such as an organic polymer or an inorganic polymer, such as silicon. For example, when the insulating layer 32 is present, the thickness of the insulating layer 32 is in the range of 200 nm to 5 μm, for example, approximately 1 μm.

[0044] The encapsulation block 25 can be formed of an organic material or an inorganic material that at least partially passes the radiation emitted by the light-emitting diode DEL. The maximum thickness of the encapsulation block 25 measured perpendicular to the upper surface 12 is preferably in the range of 1 μm to 30 μm. The width of the encapsulation block 25 can correspond to the diameter of a circle circumscribing the encapsulation block in plan view. According to an embodiment, the width of the encapsulation block 25 is in the range of 3 μm to 30 μm. According to an embodiment, the upper surface 26 is flat and parallel to the upper surface 12. According to an embodiment, the side wall 18 is perpendicular to the upper surface 12. As a modification, the side wall 18 can be inclined with respect to the upper surface 12.

[0045] The encapsulation block 25 can be formed from at least partially transparent organic materials. The encapsulation block 25 can include a matrix of at least partially transparent organic or inorganic materials in which particles of a dielectric material are optionally dispersed. The refractive index of the dielectric material constituting the particles is strictly greater than the refractive index of the material constituting the matrix. According to an embodiment, the encapsulation block 25 includes a matrix formed from silicone, also referred to as polysiloxane, or a matrix formed from an epoxide polymer, and further includes particles of a dielectric material dispersed within the matrix. The particles are composed of any type of material capable of having a suitable refractive index to obtain relatively spherical nanoparticles. For example, the particles can be composed of titanium oxide (TiO2), zirconium oxide (ZrO2), zinc sulfide (ZnS), lead sulfide (PbS), or amorphous silicon (Si). It has been found that the average diameter of the particles is the diameter of a sphere having the same volume. The average diameter of the particles of the dielectric material is in the range of 2 nm to 250 nm. The volume concentration of the particles with respect to the total weight of the encapsulation block 25 is in the range of 1% to 50%. According to a further embodiment, the encapsulation block 25 can be composed of one of the materials described in relation to the insulating layers 14, 28, 32.

[0046] In the case where the insulating layer 32 is absent, the encapsulation block 25 has a refractive index in the range of 1.3 to 1.6. In the case where the insulating layer 32 is present, the encapsulation block 25 has a refractive index in the range of 1.8 to 2.2, and the insulating layer 32 has a refractive index in the range of 1.3 to 1.6.

[0047] By means of the optoelectronic device according to the above-described embodiment, it is advantageous that the overall extraction efficiency of the optoelectronic device 5 can be increased, that is, the light emitted from the optoelectronic device 5 through the front surface 36 can be increased. In order for an observer viewing the optoelectronic device 5 to perceive it, the light needs to exit the encapsulation block 25 from the front surface 36. In order to increase the extraction efficiency of the optoelectronic device 5, a surface treatment known as texturing can be performed on the front surface 36 to form a high-low pattern on the front surface 36.

[0048] Simulations of the optoelectronic device 5 shown in FIG. 1 were performed. In these simulations, the outer diameter of the encapsulation block 25 covered by the electrode 30 was 5 μm, the support 10 was formed of aluminum, the electrode 24 was formed of TCO, the electrode 30 was formed of TCO, the wire 16 and the shell 22 were formed of GaN, and had a height of 5 μm and an outer shape of 1.25 μm. When the insulating layer 32 was present, the refractive index of the insulating layer 32 was selected to be 1.45.

[0049] FIG. 2 shows a transition curve of the light extraction efficiency LEE of the optoelectronic device 5 shown in FIG. 1 according to the refractive index n of the encapsulation block 25. The simulations indicated by diamonds were obtained without the insulating layer 32 considering that the support 10 formed of aluminum forms a mirror of specular reflection. The simulations indicated by circles were obtained without the insulating layer 32 considering that the support 10 has Lambertian reflection. The simulations indicated by squares were obtained with the insulating layer 32 considering that the support 10 formed of aluminum forms a mirror of specular reflection. The simulations indicated by triangles were obtained with the insulating layer 32 considering that the support 10 has Lambertian reflection.

[0050] FIG. 3 is a partial cross-sectional schematic view showing a further embodiment of an optoelectronic device 40 with micro- or nanowires. The optoelectronic device 40 comprises all the elements of the optoelectronic device 5 shown in FIG. 1 and further comprises a luminescent layer 42 covering the encapsulation block 25 with respect to at least some light-emitting diodes DEL. The luminescent layer 42 can further serve the role of the insulating layer 32 described above. Accordingly, the refractive index range of the luminescent layer 42 is the same as the range described above with respect to the insulating layer 32. The optoelectronic device 40 can further comprise a transparent layer 43 covering the luminescent layer 42 and a filter 44 covering the layer 43 configured to block the transmission of radiation in a given wavelength region. The filter 44 can correspond to a colored layer or a laminate of layers having various refractive indices forming a Bragg filter. The luminescent layer 42 can be a conformal layer. By means of the filter 44, it is possible to adjust the wavelength region of the radiation emerging from the luminescent layer 42. The refractive index of the layer 43 is as close to 1 as possible, preferably lower than the refractive index of the luminescent layer 42, preferably lower than 1.5, so as to reduce or eliminate the reflection of the light rays emerging from the luminescent layer 42 at the filter 44. The layer 43 is formed, for example, of MgF2, a polymer, such as an acrylate, or corresponds to a film of air.

[0051] The luminescent layer 42 can have a luminescent group, and the luminescent group is adapted to emit light at a wavelength different from the wavelength of the light emitted by the associated light-emitting diode DEL when excited by the light emitted by the associated light-emitting diode DEL. The thickness of the luminescent layer 42 can be in the range of 4 μm to 40 μm.

[0052] According to an embodiment, the luminescent layer 42 contains particles of at least one luminescent material. Examples of luminescent materials include yttrium aluminum garnet (YAG) activated by trivalent cerium ions, also known as YAG:Ce or YAG:Ce3+. The average size of the particles of conventional luminescent materials is generally greater than 5 μm.

[0053] According to an embodiment, each luminescent layer 42 includes a matrix in which nanoscale single crystal particles of a semiconductor material, hereinafter also referred to as semiconductor nanocrystals or nanoluminescent particles, are dispersed. The internal quantum efficiency QYint of the luminescent material is equal to the ratio of the number of photons emitted to the number of photons absorbed by the luminescent substance. The internal quantum efficiency QYint of the semiconductor nanocrystals is higher than 5%, preferably higher than 10%, more preferably higher than 20%.

[0054] According to an embodiment, the average size of the nanocrystals is in the range of 0.5 nm to 1000 nm, preferably 0.5 nm to 500 nm, more preferably 1 nm to 100 nm, particularly 2 nm to 30 nm. At sizes smaller than 50 nm, the light conversion characteristics of the semiconductor nanocrystals are basically determined according to the quantum confinement phenomenon. Therefore, the semiconductor nanocrystals correspond to quantum dots (in the case of three-dimensional confinement) and quantum wells (in the case of two-dimensional confinement).

[0055] According to an embodiment, the semiconductor material of the semiconductor nanocrystals is selected from the group consisting of cadmium selenide (CdSe), indium phosphide (InP), cadmium sulfide (CdS), zinc sulfide (ZnS), zinc selenide (ZnSe), cadmium telluride (CdTe), zinc telluride (ZnTe), cadmium oxide (CdO), zinc cadmium oxide (ZnCdO), cadmium zinc sulfide (CdZnS), cadmium zinc selenide (CdZnSe), silver indium sulfide (AgInS2), perovskites of the type PbScX3 (where X is a halogen atom, particularly iodine (I), bromine (Br) or chlorine (Cl)), and mixtures of at least two of these compounds. According to an embodiment, the semiconductor material of the semiconductor nanocrystals is selected from the materials described in the publication of Physica Status Solidi (RRL) - Rapid Research Letters Volume 8, No. 4, p. 349 - 352, April 2014 by Blevenec et al.

[0056] According to an embodiment, the size of the semiconductor nanocrystals is selected according to the desired wavelength of the radiation emitted by the semiconductor nanocrystals. For example, CdSe nanocrystals with an average size of about 3.6 nm are adapted to convert blue light into red light, and CdSe nanocrystals with an average size of about 1.3 nm are adapted to convert blue light into green light. According to a further embodiment, the composition of the semiconductor nanocrystals is selected according to the desired wavelength of the radiation emitted by the semiconductor nanocrystals.

[0057] The matrix is formed of a material that at least partially passes the radiation emitted by the light-emitting diode DEL and the radiation emitted by the luminescent particles. The matrix is formed, for example, of silica. The matrix is formed, for example, of any at least partially transparent polymer, in particular silicone, epoxy or polylactic acid (PLA). The matrix can be formed of an at least partially transparent polymer used with a three-dimensional printer, for example PLA. According to an embodiment, the matrix contains 2 to 90% by weight, preferably 10 to 60% by weight, of nanocrystals, for example approximately 30% by weight of nanocrystals. The matrix can further contain, for example, scattering particles in the range of 100 nm to 300 nm in diameter, in particular TiO2 particles.

[0058] Regarding the optoelectronic device 40 shown in FIG. 3, a simulation was performed using the above-described simulation parameters for obtaining the curve shown in FIG. 2.

[0059] Figure 4 shows a transition curve of the pixel optical efficiency (POE) of the optoelectronic device 40 shown in Figure 3 according to the thickness E42 of the luminescent layer 42. The pixel optical efficiency corresponds to the ratio of the optical power radiated towards free space (including conversion losses) to the optical power generated by the light-emitting diode. The simulations shown as diamonds were obtained when the support 10 corresponded to an opaque and non-glossy material between the light-emitting diodes, i.e., a material having substantially Lambertian reflection. The simulations shown as circles were obtained when the support 10 corresponded to a mirror between the light-emitting diodes, i.e., having substantially specular reflection. The curves shown as unfilled circles or diamonds were obtained when the refractive index of the layer 43 was equal to 1.5, and the curves shown as filled circles or diamonds were obtained when the refractive index of the layer 43 was equal to 1. The closer the refractive index of the insulating layer 43 is to 1, the further the pixel optical efficiency POE increases. It can be further seen that as the thickness of the luminescent layer 42 increases, the contribution of the change in the refractive index of the insulating layer 43 to the POE decreases. It can be further seen that when the thickness of the luminescent layer 42 is greater than approximately 15 μm, the change in the thickness of the luminescent layer 42 has little effect on the POE.

[0060] Figure 5 is a partial cross-sectional schematic view showing a further embodiment of an optoelectronic device 50 provided with micro-wires or nano-wires. The optoelectronic device 50 further includes, for each light-emitting diode DEL, a conductive pad 52 disposed between the optoelectronic device 50 and the support 10, the insulating layer 14 covering the side edges of the conductive pad 52, the shell 22 and the electrode 30 not covering the lower end wall 19 of the wire 16 but covering the upper end wall 20 of the wire 16, the insulating layer 28 being disposed between the conductive pad 52 and the electrode layer 30, and the protrusion 29 connecting the wire 16 to the conductive pad 52. Except for these points, the optoelectronic device 50 includes all the elements of the optoelectronic device 40 shown in Figure 3.

[0061] Figure 6 is a partial cross-sectional schematic view showing a further embodiment of the optoelectronic device 55 with micro or nanowires. The optoelectronic device 55 comprises all the elements of the optoelectronic device 5 shown in Figure 1 and further comprises a lens 56 that completely covers the encapsulation block 25 for each light-emitting diode DEL. In particular, the lens 56 covers the upper surface and the side walls of the encapsulation block 25. According to an embodiment, the lens 56 has an outer surface 58 in contact with the air 34, and the outer surface 58 has at least partially a substantially parabolic shape in a cross-section including the axis of the wire 16. A gap 37 is present and is provided between two lenses 56 covering a pair of adjacent light-emitting diodes DEL.

[0062] The lens 56 can be formed from an organic or inorganic material, and in particular can be formed from the materials described above to form a matrix of the encapsulation block 25 and / or the luminescent layer 42. The lens 56 can enhance the directivity of the light emitted by the optoelectronic device 55. The thickness Zmax of the lens 56 corresponds to the maximum distance between the electrode layer 30 and the outer surface 58. The width Ymax of the lens 56 corresponds to the maximum distance of the lens 56 measured parallel to the upper surface 12 of the support 10. According to an embodiment, the thickness Zmax is in the range of 8 μm to 50 μm. According to an embodiment, the width Ymax is in the range of 8 μm to 50 μm. The refractive index of the lens 56 is preferably in the range of 1.4 to 1.5.

[0063] According to an embodiment, the support 10 reflects the radiation emitted by the light-emitting diode DEL, and the side walls of the lens 56 in the lower part of the lens 56 are surrounded by a layer that reflects the radiation emitted by the light-emitting diode DEL.

[0064] Regarding the optoelectronic device 55 shown in Figure 6, a simulation was performed using the above-described simulation parameters to obtain the curve shown in Figure 2. The lens 56 was formed from a material having a refractive index of 1.45. In the simulation, the maximum width Ymax of the lens 56 was equal to the maximum thickness Zmax of the lens 56.

[0065] FIG. 7 shows the transition curves C1, C2, and C3 of the energy intensity of the radiation emitted in the given direction by the optoelectronic device 55 shown in FIG. 6 according to the inclination (angle) in a given direction with respect to the upper surface 12 of the support 10 when the maximum thickness Zmax of the lens 56 is 6 μm, 12 μm, and 18 μm, respectively. As is apparent from FIG. 7, as the maximum thickness Zmax of the lens 56 increases, the energy intensity at a small incident angle, that is, the energy intensity regarding the radiation emitted substantially perpendicular to the upper surface 12 of the support 10 increases.

[0066] FIG. 8 shows the transition curve of the optical power P emitted by the optoelectronic device 55 shown in FIG. 6 with a radiation cone having a half angle of 20° at the apex with respect to the axis perpendicular to the upper surface 12 of the support 10 according to the maximum thickness Zmax of the lens 56. The simulation indicated by the large black-filled circle was obtained using a lens 56 whose outer surface 58 corresponds to a parabola. For comparison, the two simulations indicated by the large unfilled circles were obtained using a lens having a pyramid shape. As is apparent from FIG. 8, as the maximum thickness Zmax of the lens 56 increases, the optical power of the radiation cone increases. For comparison, the straight line P1 indicated by the small unfilled circle shows the optical power P emitted by the radiation cone defined above without the lens 56, and the straight line P2 indicated by the small filled circle shows the optical power P emitted by the Lambert emitter with the radiation cone defined above.

[0067] FIG. 9 is a partial cross-sectional schematic view showing a further embodiment of the optoelectronic device 60 provided with a micro wire or a nano wire. The optoelectronic device 60 includes all the elements of the optoelectronic device 40 shown in FIG. 3 and further includes the lens 56 of the optoelectronic device 55 shown in FIG. 6. In this embodiment, the lens 56 covers the sealing block 25, and the luminescent layer 42 is disposed between the sealing block 25 and the lens 56.

[0068] Figure 10 is a partial cross-sectional schematic view showing a further embodiment of the optoelectronic device 65 with micro-wires or nano-wires. The optoelectronic device 65 comprises all the elements of the optoelectronic device 55 shown in Figure 6, and further comprises an angle filter 66 covering the light-emitting diode DEL, and three light-emitting diodes DEL are shown. The angle filter 66 is configured to block the light rays emitted by the light-emitting diodes DEL whose incident angle with respect to a reference direction, for example, the direction perpendicular to the upper surface 12 of the support 10, is within a first incident angle range, and the light rays of the peripheral light outside the optoelectronic device 65, and is configured to allow the light rays whose direction is within at least a second incident angle range different from the first incident angle range to pass through. In this embodiment, the angle filter 66 has a layer 68 that does not allow visible light to pass through and preferably absorbs visible light and has a through-opening 69. The through-opening 69 can be formed to be perpendicularly aligned with the light-emitting diode DEL according to the reference direction.

[0069] As shown in Figure 10, each light-emitting diode DEL is preferably covered with a lens 56. The angle filter 66 is held away from the support 10 by a spacer (not shown), and a film of air 34 is provided between the angle filter 66 and the lens 56. Since a considerable portion of the radiation emerging from the lens 56 has a small incident angle with respect to the reference direction, most of this radiation passes through the angle filter 66 without being blocked. Conversely, most of the radiation due to peripheral light is blocked by the angle filter 66. Therefore, the undesirable reflection of peripheral light on the reflective elements of the optoelectronic device 65, such as metal tracks, can be reduced. Therefore, the contrast of the optoelectronic device 65 can be further enhanced.

[0070] Figures 11 to 20 are partial cross-sectional schematic views showing the structures obtained in successive steps of an embodiment of a method for manufacturing the optoelectronic device 50 shown in Figure 5. This method has the following steps.

[0071] 1) Formation of the light-emitting diode DEL (Figure 11) A light-emitting diode DEL can be formed on a substrate 70 covered by a nucleation layer 72, also known as a seed layer, and an electrical insulation layer 74 covering the nucleation layer 72, the electrical insulation layer 74 having a through-opening 76 that exposes a part of the nucleation layer 72 at a desired position where the light-emitting diode DEL is to be formed. The seed layer 72 is a layer that stimulates the growth of wires. The seed layer 72, the wires 16, the shell 22, and the electrode layer 30 can be deposited by metalorganic chemical vapor deposition (MOCVD), also known as chemical vapor deposition (CVD) or metalorganic vapor phase epitaxy (MOVPE). However, methods such as molecular beam epitaxy (MBE), gas-source MBE (GSMBE), metalorganic MBE (MOMBE), plasma-assisted MBE (PAMBE), atomic layer epitaxy (ALE), hydride vapor phase epitaxy (HVPE), or methods such as atomic layer deposition (ALD) can be used. Furthermore, methods such as vapor deposition or reactive sputtering can be used. A more detailed method for manufacturing a light-emitting diode is described in U.S. Patent No. 9,537,044. A sealing layer 78 of the material constituting the sealing block 25 is deposited over the entire structure, for example, by spin deposition, jet printing, or silk screening. When the sealing layer 78 is an oxide, the sealing layer 78 can be deposited by CVD. A part of the electrode layer 30 is exposed on the surface of the sealing layer 78.

[0072] 2) Fixing the structure obtained in the above-described process to the handle 79, removing the substrate 70 and the nucleation layer 72, and partially cutting the structure obtained on the side of the insulation layer 74 for defining the sealing block 25 and the insulation layer 28 (FIG. 12) The fixing to the handle 79 can be performed by molecular bonding or using an intermediate bonding material. The removal of the substrate 70 can be performed by chemical mechanical polishing (CMP). The cutting enabling the definition of the sealing block 25 and the insulation layer 28 can be performed by etching or die cutting.

[0073] 3) Fixing the light-emitting diode of the structure obtained in the above-described process to the support 10 (FIG. 13) The fixing can be carried out by means of a "flip chip" type of connection. According to a further embodiment, the fixing can be carried out by means of a direct bonding, also referred to as a molecular bonding of the light-emitting diode to the conductive pad 52 provided on the support 10. As shown in FIG. 13, only a specific light-emitting diode of the structure shown in FIG. 12 is fixed to the support 10. FIG. 14 shows the result obtained when all the light-emitting diodes are fixed at the desired positions on the support 10.

[0074] 4) Formation of the insulating layer 14 (FIG. 15) The insulating layer 14 can be formed by conformally depositing an insulating layer over the entire structure shown in FIG. 14 and removing a part of this conformal layer to form the insulating layer 14.

[0075] 5) Formation of the electrode layer 30, for example by conformal deposition (FIG. 16)

[0076] 6) Possible formation of an insulating layer 32 covering the electrode layer 30 for a light-emitting diode DEL without the luminescent layer 42 (FIG. 17)

[0077] 7) Formation of the luminescent layer 42 for other light-emitting diodes DEL, for example by direct printing of the material constituting the luminescent layer 42 at the desired positions, such as inkjet printing, aerosol printing, microstamping, photolithography, silk screen, flexographic printing, spray coating or deposition of drops (FIG. 18)

[0078] 8) Formation of the insulating layer 43, for example by conformal deposition (FIG. 19)

[0079] 9) Formation of the filter 44 (FIG. 20)

[0080] In the case of an optoelectronic device provided with a lens 56 covering the light-emitting diode, the lens 56 can be formed by depositing a layer of the material constituting the lens over the light-emitting diode and etching this layer or forming this layer.

[0081] Figs. 21 to 22 are partial cross-sectional schematic views showing structures obtained in successive steps of an embodiment of a method for manufacturing a photoelectronic device corresponding to a modified example of the photoelectronic device 60 shown in Fig. 9. In this embodiment, the lens 56 is pre-formed separately from the structure provided with the light-emitting diode. In Fig. 21, the lens 56 forms an integral structure 82 obtained, for example, by molding. Each lens 56 has a recess 84 configured to receive the light-emitting diode DEL. The filter 44 can be formed in a specific recess. Thereafter, the integral structure 82 is fixed to the support 10 using, for example, a bonding material 86 (Fig. 22). In this embodiment, when the integral structure 82 is fixed to the support 10, the size of the recess 84 is larger than the size of the light-emitting diode DEL such that a gap remains between each lens 56 and the phosphor layer 42 forming the aforementioned layer 43.

[0082] Figs. 23 to 25 are partial cross-sectional schematic views showing structures obtained in successive steps of an embodiment of a method for manufacturing the photoelectronic device 5 shown in Fig. 1. This method has the following steps.

[0083] 1)' Formation of the light-emitting diode DEL in the same manner as the method described above in step 1) in relation to Fig. 11

[0084] 2)' Partial cutting of the obtained structure on the side of the insulating layer 74 to define a part 88 of the sealing block 25, the insulating layer 28, and the nucleation layer 72 (Fig. 23) The cutting can be performed by etching or cutting out.

[0085] 3)' Fixing of the light-emitting diode of the structure obtained in the above step to the support 10 (Fig. 24) The fixing can be performed as described above in step 3) in relation to Fig. 13.

[0086] 4)' Selective release of the substrate 70 from the light-emitting diode DEL fixed to the support 10 and removal of a part 88 of the nucleation layer

[0087] The subsequent steps of this method may correspond to the steps described above in relation to FIGS. 14 to 22.

[0088] Various embodiments and modifications have been described. Those skilled in the art will understand that certain features of these embodiments can be combined, and other modifications will be readily envisioned by those skilled in the art. In particular, the structure of the light-emitting diode DEL of the optoelectronic device 50 shown in FIG. 5 can be implemented together with the optoelectronic device 5 shown in FIG. 1, the optoelectronic device 55 shown in FIG. 6, the optoelectronic device 60 shown in FIG. 9, and the optoelectronic device 65 shown in FIG. 10. Further, in the embodiments already disclosed, each encapsulation block 25 is shown to cover one light-emitting diode DEL, but it is clear that each encapsulation block 25 can cover a group of light-emitting diodes, for example, 2 to 100 light-emitting diodes. The encapsulation block can cover each of the group of light-emitting diodes along the entire sidewall 18 of the light-emitting diode.

[0089] Finally, the actual implementation of the embodiments and modifications described herein is within the scope of the skills of those skilled in the art based on the functional representations given above.

[0090] This patent application claims the priority of French Patent Application No. 18 / 71254, which is considered an essential part of this disclosure.

Claims

1. A light-emitting diode, a sealing block covering the light-emitting diode through at least a part of the radiation emitted by the light-emitting diode, a conductive layer covering the sealing block and in contact with the light-emitting diode, a transparent layer covering the conductive layer and having a refractive index lower than 1.5 and a photoelectronic device comprising the same.

2. The photoelectronic device according to claim 1, further comprising an insulating layer disposed between the conductive layer and the transparent layer and allowing at least a part of the radiation emitted by the light-emitting diode to pass therethrough.

3. The photoelectronic device according to claim 1, further comprising a phosphorescent layer disposed between the conductive layer and the transparent layer and allowing at least a part of the radiation emitted by the light-emitting diode to pass therethrough.

4. The photoelectronic device according to claim 3, wherein the refractive index of the transparent layer is lower than the refractive index of the phosphorescent layer.

5. The photoelectronic device according to claim 2, wherein the refractive index of the insulating layer is in the range of 1.3 to 1.

6.

6. The transparent layer is MgF 2 The optoelectronic device according to any one of claims 1 to 5, which is formed of a material selected from the group including polymers such as acrylate.

7. The photoelectronic device according to any one of claims 1 to 6, wherein the transparent layer is formed by conformal deposition.

8. The photoelectronic device according to any one of claims 1 to 5, wherein the transparent layer is an air film.

9. The photoelectronic device according to claim 3, wherein the thickness of the phosphorescent layer is in the range of 4 μm to 40 μm.

10. The photoelectronic device according to claim 2, wherein the thickness of the insulating layer is in the range of 200 nm to 5 μm.

11. The photoelectronic device according to claim 2 or 5, wherein the insulating layer is formed of a dielectric material selected from the group consisting of silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, hafnium oxide and diamond.

12. The photoelectronic device according to any one of claims 3, 4 and 9, further comprising a filter configured to block the transmission of radiation in a given wavelength range and covering the transparent layer.

13. The photoelectronic device according to any one of claims 1 to 12, further comprising a lens covering the transparent layer.

14. The photoelectronic device according to any one of claims 1 to 13, wherein the light-emitting diode has a semiconductor element in the form of a wire, a cone or a frustum of a cone.

15. The light-emitting diode is placed on the surface of a support, The encapsulation block is placed on the support, and the optoelectronic device according to any one of claims 1 to 14.

16. A first light-emitting diode, and a first encapsulation block that covers the first light-emitting diode at least partially through the radiation emitted by the first light-emitting diode, a first conductive layer that covers the first encapsulation block and is in contact with the first light-emitting diode, a first transparent layer that covers the first conductive layer and has a refractive index lower than 1.5, an insulating layer that is disposed between the first conductive layer and the first transparent layer and allows at least partial passage of the radiation emitted by the first light-emitting diode, a second light-emitting diode, and a second encapsulation block that covers the second light-emitting diode at least partially through the radiation emitted by the second light-emitting diode, a second conductive layer that covers the second encapsulation block and is in contact with the second light-emitting diode, a second transparent layer that covers the second conductive layer and has a refractive index lower than 1.5, a phosphorescent layer that is disposed between the second conductive layer and the second transparent layer and allows at least partial passage of the radiation emitted by the second light-emitting diode The optoelectronic device according to claim 1, comprising.

17. A method for manufacturing an optoelectronic device including a light-emitting diode, comprising: forming an encapsulation block that covers the light-emitting diode at least partially through the radiation emitted by the light-emitting diode, forming a conductive layer that covers the encapsulation block and is in contact with the light-emitting diode, forming a transparent layer that covers the conductive layer and has a refractive index lower than 1.

5.

18. The method according to claim 17, wherein an insulating layer is disposed between the conductive layer and the transparent layer, covers the conductive layer, and allows at least partial passage of the radiation emitted by the light-emitting diode.

19. The method according to claim 17, wherein a phosphorescent layer is disposed between the conductive layer and the transparent layer, covers the conductive layer, and allows at least partial passage of the radiation emitted by the light-emitting diode.

20. The method according to claim 19, wherein a filter configured to block transmission of radiation in a given wavelength range is formed covering the transparent layer.

21. The method according to any one of claims 17 to 20, wherein a lens covering the transparent layer is formed.

22. The optoelectronic device further comprises a support having a surface, and the light-emitting diode is placed on the surface, the method according to any one of claims 17 to 21. **Claim 23** The light-emitting diode has a semiconductor element in the form of a wire, a cone or a frustum of a cone, the method according to any one of claims 17 to 22.

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