Conversion element, method for producing a conversion element, and optoelectronic device

Abstract

A conversion element is specified. According to one embodiment, the conversion element (1) comprises a first segment (2) comprising a first phosphor (21), wherein the first segment (2) is configured to convert electromagnetic radiation of a first wavelength range into electromagnetic radiation of a second wavelength range, and a second segment (3) comprising a second phosphor (31), wherein the second segment (3) is configured to convert electromagnetic radiation of the first wavelength range into electromagnetic radiation of a third wavelength range, and wherein the first segment (2) laterally surrounds the second segment (3) in a main extension plane of the conversion element (1). Furthermore, a method for producing a conversion element and an optoelectronic device, in particular comprising a micro-LED, are specified.

Description

[0001] Description

[0002] CONVERSION ELEMENT, METHOD FOR PRODUCING A CONVERSION ELEMENT, AND OPTOELECTRONIC DEVICE

[0003] A conversion element, a method for producing a conversion element, and an optoelectronic device are specified.

[0004] It is an object to provide a conversion element with improved efficiency. Additionally, it is an object to provide a simple method for producing a conversion element with improved efficiency. Furthermore, it is an object to provide an optoelectronic device with improved efficiency.

[0005] A conversion element is specified.

[0006] According to at least one embodiment, the conversion element comprises a first segment comprising or consisting of a first phosphor. The first segment is configured to convert electromagnetic radiation of a first wavelength range into electromagnetic radiation of a second wavelength range. In particular, the second wavelength range comprises longer wavelengths than the first wavelength range. For example, an ability of the first segment to convert electromagnetic radiation is attributed to the first phosphor converting electromagnetic radiation of the first wavelength range into electromagnetic radiation of the second wavelength range. For instance, the second wavelength range is in the yellow spectral range.

[0007] In particular, the first phosphor is a Ce3+-activated garnet. For example, the first phosphor comprises the formula (REx-xCex) 3 (Alx-yA'y) 5O12, where 0 < x < 0.1 and 0 < y < 1, RE is at least one of Y, Lu, Tb, and Gd, and A' is at least one of Sc and Ga .

[0008] According to at least one embodiment , the conversion element comprises a second segment comprising or consisting of a second phosphor . The second segment is configured to convert electromagnetic radiation of the first wavelength range into electromagnetic radiation of a third wavelength range . In particular, the third wavelength range comprises longer wavelengths than the first wavelength range . For example , the third wavelength range comprises di f ferent wavelengths than the second wavelength range . For instance , the third wavelength range comprises longer wavelengths than the second wavelength range . For example , an ability of the second segment to convert electromagnetic radiation is attributed to the second phosphor converting electromagnetic radiation of the first wavelength range into electromagnetic radiation of the third wavelength range . For instance , the third wavelength range is in the red spectral range .

[0009] In particular, the second phosphor is an Eu2+-activated nitride-silicate phosphor . For example , the second phosphor comprises the formula (AEi-xEUx) 2A12Si2N6, where 0 < x < 0 . 1 and AE is at least one of Sr and Ca .

[0010] According to at least one embodiment , the first segment laterally surrounds the second segment in a main extension plane of the conversion element , in particular completely . In particular, the main extension plane extends along two lateral extension directions , such as along a length and a width, of the conversion element . The main extension plane extends , within the bounds of manufacturing tolerances , parallel to or along a top face and / or a bottom face of the conversion element . Perpendicular to the main extension plane , in a vertical direction, the conversion element has a thickness . The thickness of the conversion element is small compared with the extent of the conversion element in the lateral directions . For example , when the conversion element is placed in a radiation beam of a semiconductor chip having a certain emitting area, the main extension plane of the conversion element is parallel to that emitting area and the thickness of the conversion element is perpendicular to that emitting area .

[0011] In particular, side surfaces of the second segment perpendicular to the main extension plane of the conversion element are covered, in particular completely, with the first segment . For example , the second segment is arranged centrally within the first segment . In other words , the second segment is arranged in a center of the conversion element . In particular, the first segment is in direct mechanical and optical contact to the second segment . For example , the first segment and the second segment have an interface . For instance , the interface is perpendicular to the main extension plane of the conversion element .

[0012] According to at least one embodiment , the conversion element comprises a first segment comprising a first phosphor, wherein the first segment is configured to convert electromagnetic radiation of the first wavelength range into electromagnetic radiation of a second wavelength range , and a second segment comprising a second phosphor, wherein the second segment is configured to convert electromagnetic radiation of the first wavelength range into electromagnetic radiation of a third wavelength range , and wherein the first segment laterally surrounds the second segment in a main extension plane of the conversion element .

[0013] It is an idea of the present application to provide a conversion element having two segments comprising di f ferent phosphors in a lateral configuration . The lateral configuration reduces radiative losses in conversion elements where one phosphor in one segment is capable of absorbing electromagnetic radiation emitted from the other phosphor in the other segment . The lateral configuration minimi zes the probability that electromagnetic radiation from one segment interacts with the other segment .

[0014] In particular, the lateral configuration reduces reabsorption losses compared to conversion elements comprising two phosphors mixed in one conversion layer for phosphors having an overlap between the excitation spectrum of one phosphor and the emission spectra of the other phosphor . The spatial separation of the two phosphors in the two segments minimi zes the interactions of the converted electromagnetic radiation and the phosphors .

[0015] Furthermore , the lateral configuration reduces re-absorption losses compared to conversion elements having two layers comprising di f ferent phosphors in a vertical configuration, i . e . in a direction perpendicular to the main extension plane of the conversion element . Since electromagnetic radiation emitted from the phosphors in both segments or layers is isotropic, most of the electromagnetic radiation is emitted from either segment or layer either upwards or downwards , i . e . vertically or perpendicular to the main extension plane of the conversion element . A much smaller portion of the electromagnetic radiation is emitted laterally, i . e . parallel to the main extension plane of the conversion element . Thus , in the lateral configuration, less electromagnetic radiation from one segment is able to interact with the phosphor from another segment .

[0016] According to at least one embodiment , side surfaces of the second segment parallel to the main extension plane of the conversion element are free , in particular completely free , of the first segment . This can advantageously minimi ze the probability of electromagnetic radiation from the first segment interacting with the second segment and thus reduce re-absorption losses .

[0017] According to at least one embodiment , a thickness of the conversion element is between and including 100 pm and 200 pm, in particular between and including 150 pm and 200 pm . Here and in the following, the thickness of the conversion element is the vertical extension of the conversion element , i . e . the extension perpendicular to the main extension plane of the conversion element . A conversion element having a thickness between and including 100 pm and 200 pm can advantageously be used for partial conversion applications and for full conversion applications . A conversion element having a thickness between and including 150 pm and 200 pm can advantageously be used for full conversion applications .

[0018] According to at least one embodiment , the conversion element has the form of a platelet . In particular, the platelet comprises two main surfaces parallel to the main extension plane of the conversion element . For example , the platelet has the form of a cylinder . In this instance , the circular side surfaces can form the main surfaces . Alternatively, the platelet can have the form of a cuboid . In this instance , the main surfaces can have a rectangular shape or a square shape .

[0019] According to at least one embodiment , an area of an interface of the first segment and the second segment is smaller than an area of a main surface of the conversion element parallel to the main extension plane of the conversion element . In particular, the area of the interface is a shared surface area of the first segment and the second segment , for example the complete shared surface area of the first segment and the second segment . For instance , the area of the interface depends on the shape and the si ze of the second segment and the thickness of the conversion element . In particular, the smaller the second segment and the thinner the conversion element , the smaller the area of the interface . For example , the bigger the second segment and the thicker the conversion element , the bigger the area of the interface . It should be noted that the area of the interface is highly dependent on the speci fic application as each application has a desired color target that requires speci fic dimensions of the first segment and the second segment in order to provide a suf ficient amount of the first phosphor and the second phosphor . Thus , while a minimi zed area of the interface is desired in order to reduce re-absorption events , the area of the interface is physically limited by the overall dimensions of the conversion element . However, a lateral configuration can advantageously minimi ze the interface between the first segment and the second segment in the conversion element , in particular compared to a vertical configuration .

[0020] According to at least one embodiment , the first segment is a ceramic layer of the first phosphor . In other words , the first phosphor is the only phosphor present in the first segment . This means that the first segment is free of a further phosphor . In particular, the ceramic layer of the first phosphor is a low-scattering ceramic . Here and in the following, a low-scattering ceramic is a ceramic having a porosity of at most 0 . 05 % . In this instance , porosity is defined as the volume taken up by pores divided by the volume of the ceramic layer . With a ceramic first segment , a high thermal stability and a minimal light scattering can advantageously be reali zed .

[0021] According to at least one embodiment , the second segment is a ceramic layer of the second phosphor . In other words , the second phosphor is the only phosphor present in the second segment . This means that the second segment is free of a further phosphor . In particular, the ceramic layer of the second phosphor is a low-scattering ceramic . With a ceramic second segment , a high thermal stability and a minimal light scattering can advantageously be reali zed .

[0022] According to at least one embodiment , the second segment comprises the second phosphor in a matrix material . In particular, the matrix material is transparent . The second phosphor is present , for example , in the form of particles . In particular, the second phosphor is homogeneously distributed in the matrix material . Alternatively, the second phosphor comprises a gradient in the matrix material . That is , on a first side of the second segment the second phosphor has a greater concentration than on a second side of the second segment . For example , a refractive index of the matrix material is adapted to the second phosphor such that the refractive index of the matrix material complements the second phosphor to maximi ze light output . With a second segment comprising the second phosphor and a matrix material , a color flexibility of the conversion element and low temperature processing can advantageously be realized.

[0023] According to at least one embodiment, the matrix material comprises polysiloxane, silicone, or glass. In particular, the silicone is an optical silicone.

[0024] In particular, the polysiloxane comprises the formula [RSiO3 / 2 ] x [FbSiO]y[R3SiOi / 2 ] z, where R is any combination of methyl and / or phenyl, x + y + z = 1, and x, y, and z indicate the relative proportion of the three types of siloxane groups, T-units, D-units, and M-units, respectively. For example, the above formula is the formula of the polysiloxane in cured form. For instance, 0 < x < 1, 0 < y < 0.3, and z = 0. In this instance, the polysiloxane is particularly suited for high-temperature applications.

[0025] According to at least one embodiment, the second segment further comprises a third phosphor. In particular, the third phosphor is configured to convert electromagnetic radiation of the first wavelength range into electromagnetic radiation of the second wavelength range or the third wavelength range or a fourth wavelength range. The second segment can comprise further phosphors in addition to the second phosphor and the third phosphor. For example, the third phosphor is distributed in the matrix material together with the second phosphor. By providing a mixture of a second phosphor and a third phosphor in the second segment, applications having a specific color rendering index (CRI) can advantageously be realized.

[0026] According to at least one embodiment, the second segment further comprises filler particles. In particular, the filler particles are mixed in the matrix material . For example , a concentration of the filler particles is between and including 0 vol% and 45 vol% , in particular more than 0 vol% and at most 45 vol% . In particular, the filler particles comprise a si ze of at most 10 pm . For example , the si ze of the filler particles is a mixture of sub-micron to 10 pm particles in any proportion . The filler particles can be silica particles .

[0027] The filler particles can advantageously help tune the coef ficient of thermal expansion ( GTE ) . For example , the GTE of a matrix material of polysiloxane in the second segment can be above 100 ppm / deg, whereas the GTE of the surrounding first segment of a YAG : Ce ceramic can be below 10 ppm / deg . This mismatch can lead to delamination between the layers . Adding filler particles , in particular small silica particles , in a relatively high-volume fraction can help lower the overall thermal expansion of the second segment . This can provide a better match between the two segments . The filler particles can also provide some mechanical strength and / or toughness to the second segment . The filler particles can also be used to adj ust refractive index or scattering behavior .

[0028] According to at least one embodiment , the second segment has the form of a cylinder . The cylinder is defined by a radius and a height . In particular, the curved surface area of the cylinder forms the interface of the second segment and the first segment . In this instance , the height of the cylinder corresponds to the thickness of the conversion element . In other words , the circular side surfaces of the cylinder can be arranged parallel to the main extension plane of the conversion element . The circular side surfaces of the cylinder can be free of the first segment . With a second segment having the form of cylinder, a minimal area of the interface between the first segment and the second segment can advantageously be reali zed and, thus , re-absorption losses can further be reduced .

[0029] According to at least one embodiment , a radius of the second segment is smaller than hal f of the smallest extension of the conversion element in the main extension plane of the conversion element . In particular, a ratio of the radius of the second segment and a smallest edge length of the conversion element is less than 0 . 5 . By choosing the radius of the second segment in such a way, the second segment is completely surrounded by the first segment in a lateral direction and, thus , the stability of the conversion element can advantageously be increased . Within this limit , the radius of the second segment can be used as a design parameter to adj ust the color output of the conversion element and of any optoelectronic devices comprising the conversion element to a desired speci fication .

[0030] According to at least one embodiment , the radius of the second segment is between and including 400 pm and 500 pm, for example 440 pm .

[0031] According to at least one embodiment , the conversion element has the form of a cuboid and the second segment has the form of a cylinder . In particular, the main surfaces of the conversion element can have a rectangular shape or a square shape .

[0032] According to at least one embodiment , the conversion element has the form of a cuboid having main surfaces with a rectangular shape and the second segment has the form of a cylinder or the form of a prism with an ellipse as its base .

[0033] According to at least one embodiment , the conversion element comprises at least a further segment . In particular, the conversion element comprises a third segment . The third segment can be laterally surrounded by the second segment or laterally arranged between the first segment and the second segment . Alternatively, the third segment can laterally surround the first segment . The third segment can comprise a phosphor di f ferent from the first phosphor and the second phosphor .

[0034] Furthermore , a method for producing a conversion element is speci fied . In particular, the conversion element described herein is produced by the method for producing a conversion element . Thus , embodiments , features , and advantages described in combination with the conversion element also apply to the method for producing a conversion element and vice versa .

[0035] According to at least one embodiment , the method comprises providing a first segment comprising a first phosphor . For example , the first segment comprises or consists of a ceramic of the first phosphor .

[0036] According to at least one embodiment , the first segment comprises a recess , wherein the recess extends through the first segment perpendicular to a main extension plane of the first segment . In particular, the recess extends completely through the first segment . For example , the recess has a regular shape . For instance , the recess has the form of a cylinder, a prism with an ellipse as its base , or a cuboid . In particular, the recess is arranged centrally within the first segment .

[0037] According to at least one embodiment , the method comprises providing a second segment comprising a second phosphor in the recess . In particular, the second segment is provided in such a way that it fills the recess , for example completely . The second segment can be a ceramic of the second phosphor or comprise the second phosphor in a matrix material .

[0038] According to at least one embodiment , the method for producing a conversion element comprises providing a first segment comprising a first phosphor, wherein the first segment comprises a recess , wherein the recess extends through the first segment perpendicular to a main extension plane of the first segment , and providing a second segment comprising a second phosphor in the recess .

[0039] In particular, the method steps of providing a first segment with the recess and providing the second segment in the recess are performed sequentially or simultaneously .

[0040] In particular, the method for producing a conversion element is a method for producing a plurality of conversion element . In this instance , a plurality of first segments with recesses is provided and a second segment is provided in each recess .

[0041] With such a method, a conversion element having a lateral configuration of the first phosphor and the second phosphor can advantageously be produced simply and cost-ef f iciently .

[0042] According to at least one embodiment , providing the first segment comprises providing a first green-state tape comprising the first phosphor, forming the recess in the first green-state tape , and sintering the first green-state tape to form the first segment . In particular, the first green-state tape is provided by combining pre-ceramic powders of the first phosphor with a binder and forming a flat sheet or a flat tape using, for example , tape casting . The first green-state tape can further comprise other additives such as flux materials . Flux materials can aid in the sintering process to help keep the porosity below 0 . 05 % .

[0043] In particular, the recess is formed by punching or laser dicing . In particular, sintering the first green-state tape is performed by burning out the binder and / or the other additives and densi fying the remaining material through high- temperature treatment . In particular, multiple recesses are formed in the first green-state tape . The first green-state tape having multiple recesses can subsequently be singulated into a plurality of individual first green-state tapes only comprising one recess each . The singulation can be performed by dicing or punching . With these method steps , a ceramic first segment having a high thermal stability and a minimal light scattering can advantageously be reali zed .

[0044] According to at least one embodiment , providing the second segment comprises providing a second green-state tape comprising the second phosphor, forming a cutout from the second green-state tape comprising the form of the recess , and sintering the second green-state tape to form the second segment . In particular, the second green-state tape is provided by combining pre-ceramic powders of the second phosphor with a binder and forming a flat sheet or a flat tape using, for example , tape casting . The second green-state tape can further comprise other additives such as flux materials . In particular, the cutout comprising the form of the recess is formed by punching or laser dicing . In particular, sintering the second green-state tape is performed by burning out the binder and / or the other additives and densi fying the remaining material through high- temperature treatment . For example , sintering the second green-state tape is performed simultaneously to sintering the first green-state tape . In particular, the cutout of the second green-state tape is inserted into the recess of the first green-state tape prior to sintering . With these method steps , a ceramic second segment having a high thermal stability and a minimal light scattering can advantageously be reali zed .

[0045] According to at least one embodiment , providing the second segment comprises adding the second phosphor and a matrix precursor to the recess , and curing the matrix precursor to form the second segment . In particular, the second phosphor and the matrix precursor are added to the recess after sintering the first green-state tape comprising the recess . For example , the second phosphor can be mixed with the matrix precursor to form a slurry . The slurry can then be deposited in the recess . The slurry can further comprise a third phosphor and / or filler particles . In particular, curing the matrix precursor includes forming the matrix material from the matrix precursor . For example , curing the matrix precursor forms a solid body of the slurry . With these method steps , a second segment comprising the second phosphor and a matrix material and thus a color flexibility of the conversion element and low temperature processing can advantageously be reali zed . According to at least one embodiment , providing the first green-state tape and / or providing the second green-state tape comprises laminating together a plurality of green-state layers or green-state tapes .

[0046] Furthermore , an optoelectronic device is speci fied . In particular, the optoelectronic device comprises the conversion element described herein . Thus , embodiments , features , and advantages described in combination with the conversion element and the method for producing a conversion element also apply to the optoelectronic device and vice versa .

[0047] According to an embodiment , the optoelectronic device comprises a semiconductor chip configured to emit electromagnetic radiation of a first wavelength range . In other words , the semiconductor chip is configured to emit a primary radiation . In particular, the primary radiation comprises wavelengths in the ultraviolet to blue spectral range , for example of 450 nm .

[0048] According to at least one embodiment , the optoelectronic device comprises a conversion element described herein configured to convert at least a part of the electromagnetic radiation of the first wavelength range into electromagnetic radiation of a second wavelength range and into electromagnetic radiation of a third wavelength range . In other words , the conversion element converts the primary radiation into secondary radiations of di f ferent wavelength ranges . For example , the first wavelength range is at least partially di f ferent from the second wavelength range and from the third wavelength range . For instance , the second wavelength range comprises wavelengths having a higher energy compared to the wavelengths in the third wavelength range . In particular, an ability of the conversion element to convert electromagnetic radiation is attributed to the first phosphor converting electromagnetic radiation of the first wavelength range into electromagnetic radiation of the second wavelength range and to the second phosphor converting electromagnetic radiation of the first wavelength range into electromagnetic radiation of the third wavelength range .

[0049] In particular, the conversion element is configured to fully convert the electromagnetic radiation of the first wavelength range . In other words , no electromagnetic radiation of the first wavelength range is transmitted through the conversion element . "None" in this context means that so little electromagnetic radiation of the first wavelength range is transmitted that it no longer perceptibly influences the electromagnetic radiation emitted by the optoelectronic device . For example , at most 10 % , in particular at most 5 % and preferably at most 1 % of the electromagnetic radiation of the first wavelength range is transmitted by the conversion element . The optoelectronic device then only emits the electromagnetic radiation generated by the phosphors present in the conversion element , for example the electromagnetic radiation emitted by the first phosphor and the second phosphor . In other words , full conversion of the primary radiation into secondary radiation takes place . The conversion element thus completely converts the primary radiation into secondary radiation . For example , the optoelectronic device emits amber light , in particular amber light without a blue component . In particular, the thickness of the conversion element is between and including 150 pm and 200 pm for full conversion applications . In particular, the conversion element is configured to partially convert the electromagnetic radiation of the first wavelength range . The unconverted portion of the electromagnetic radiation of the first wavelength range is transmitted through the conversion element . In this case , the optoelectronic device emits a mixed light composed of the electromagnetic radiation of the first wavelength range and the electromagnetic radiation generated by the phosphors present in the conversion element , for example the electromagnetic radiation emitted by the first phosphor and the second phosphor . In particular, the thickness of the conversion element is between and including 100 pm and 200 pm for partial conversion applications .

[0050] According to at least one embodiment , the optoelectronic device comprises a semiconductor chip configured to emit electromagnetic radiation of a first wavelength range , and a conversion element described herein configured to convert at least a part of the electromagnetic radiation of the first wavelength range into electromagnetic radiation of a second wavelength range and into electromagnetic radiation of a third wavelength range .

[0051] Advantageously, the optoelectronic device described herein has an improved ef ficiency due to the lateral configuration of the first phosphor and the second phosphor in the conversion element . In this way, the conversion element can have an improved performance compared to conversion elements comprising the first phosphor and the second phosphor mixed in one layer or a vertical configuration of the first phosphor and a second phosphor . Furthermore , the optoelectronic device described herein has an increased light output and an increased brightness due to reduced losses , in particular due to reduced conversion losses .

[0052] According to at least one embodiment , the semiconductor chip is a micro-LED . Here and in the following, LED is an abbreviation for the term " light-emitting diode" . Micro-LEDs may have a width, a length, a thickness and / or a diameter smaller than or equal to 100 micrometers , in particular smaller than or equal to 70 micrometers , for example smaller than or equal to 50 micrometers . In particular, micro-LEDs , for example rectangular micro-LEDs , have an edge length, for instance in plan view of layers of a layer stack, of a luminous surface smaller than or equal to 70 micrometers , for example smaller than or equal to 50 micrometers . For example , the micro-LED is a light-emitting diode , wherein a growth substrate is removed, such that a thickness of the micro-LED is , for instance , between and including 1 . 5 micrometers and 10 micrometers . For example , the micro-LED is provided on a wafer having releasable retaining structures . The micro-LED can be detached from the wafer in a non-destructive manner .

[0053] According to at least one embodiment , the optoelectronic device is used in lighting applications , in particular in high color rendering index ( CRI ) application, warm-white lighting applications , or automotive applications , for example in automotive signaling, in proj ection applications or in stage lighting .

[0054] Advantageous embodiments and developments of the conversion element , the method for producing a conversion element , and the optoelectronic device will become apparent from the exemplary embodiments described below in conj unction with the figures . In the figures :

[0055] Figures 1A to 1C, 2 , and 3A each show a schematic illustration of a conversion element according to di f ferent exemplary embodiments ,

[0056] Figure 3B shows a comparative example of a conversion element ,

[0057] Figure 4 shows a contour plot of the area of an interface of the first segment and the second segment of conversion elements according to di f ferent exemplary embodiments ,

[0058] Figures 5A to 5G and 6A to 6G show schematic illustrations of methods for producing a conversion element according to di f ferent exemplary embodiments ,

[0059] Figure 7 shows a schematic illustration of an optoelectronic device according to an exemplary embodiment , and

[0060] Figure 8 shows power flow budgets of an optoelectronic device according to an exemplary embodiment and a comparative example .

[0061] In the exemplary embodiments and figures , similar or similarly acting constituent parts are provided with the same reference signs . The elements illustrated in the figures and their si ze relationships among one another should not be regarded as true to scale . Rather, individual elements may be represented with an exaggerated si ze for the sake of better representability and / or for the sake of better understanding . Figure 1A shows an exemplary embodiment of a conversion element 1 in a top view, figure IB shows the exemplary embodiment of the conversion element 1 in a bottom view, and figure 1C shows the exemplary embodiment of the conversion element 1 in a cross-sectional side view .

[0062] The conversion element 1 of the exemplary embodiment of figures 1A to 1C comprises a first segment 2 and a second segment 3 . The first segment 2 comprises a first phosphor 21 . In the exemplary embodiment of figures 1A to 1C, the first segment is a ceramic, in particular a low-scattering ceramic, of the first phosphor 21 . For example , the first phosphor 21 is a Ce3+-activated garnet . For instance , the first phosphor comprises the formula (REi-xCex) 3 (Alx-yA'y) 5O12 , where 0 < x < 0 . 1 and 0 < y < 1 , RE is at least one of Y, Lu, Tb, and Gd, and A' is at least one of Sc and Ga . The first segment 2 is configured to convert electromagnetic radiation of a first wavelength range into electromagnetic radiation of a second wavelength range . For example , the first segment 2 is configured to convert blue radiation into yellow radiation .

[0063] The first segment 2 laterally surrounds the second segment 3 in a main extension plane of the conversion element 1 . The first segment 2 only covers the side surfaces of the second segment 3 that are perpendicular to a main extension plane of the conversion element 1 . The side surfaces 32 , 33 of the second segment 3 parallel to the main extension plane of the conversion element 1 are free of the first segment 2 . The side surface 32 can also be referred to as a top surface and the side surface 33 can be referred to as a bottom surface of the second segment 3 . The conversion element 1 of the exemplary embodiment of figures 1A to 1C has the shape of a cuboid with square main surfaces 11 , 12 parallel to the main extension plane of the conversion element 1 . A thickness x of the conversion element 1 is between and including 150 pm to 200 pm . The second segment 3 has the shape of a cylinder, wherein the circular side surfaces 32 , 33 are parallel to the main extension plane of the conversion element 1 . The radius of the second segment 3 is smaller than hal f the smallest edge length of the main surfaces 11 , 12 of the conversion element 1 . The edge lengths of the main surfaces 11 , 12 are formed by the lateral extension of the side surfaces 22 , 23 of the first segment 2 . For example , the radius r of the second segment 3 is between and including 400 pm and 500 pm such as 440 pm . In this instance , the edge length of the main surfaces 11 , 12 are between and including more than 400 pm and 500 pm, respectively, for example more than 880 pm .

[0064] The second segment 3 comprises a second phosphor 31 . For example , the second phosphor 31 is an Eu2+-activated nitridesilicate phosphor . For instance , the second phosphor comprises the formula (AEi-xEUx) 2A12Si2N6, where 0 < x < 0 . 1 and AE is at least one of Sr and Ca . The second segment 3 is configured to convert electromagnetic radiation of the first wavelength range into electromagnetic radiation of a third wavelength range . For example , the second segment is configured to convert blue radiation into red radiation .

[0065] In the exemplary embodiment of figures 1A to 1C, the second phosphor 31 is dispersed in a matrix material 34 . For example , the matrix material comprises polysiloxane , silicone , or glass . In particular, the matrix material comprises a polysiloxane comprising the formula [RSiO3 / 2 ] x [FbSiO]y[R3SiOi / 2 ] z, where R is any combination of methyl and / or phenyl , x + y + z = 1 , and x, y, and z indicate the relative proportion of the three types of siloxane groups , T-units , D-units , and M-units respectively . For instance , 0 < x < 1 , 0 < y < 0 . 3 , and z = 0 .

[0066] The second segment 3 can further comprise a third phosphor dispersed in the matrix material 34 . For example , the third phosphor can be configured to convert blue radiation into yellow radiation or into red radiation .

[0067] Further, the second segment 3 can comprise filler particles in a concentration between and including 0 vol% and 45 vol% dispersed in the matrix material 34 . For example , the filler particles are silica particles . The si ze of the silica particles can be a mixture of sub-micron to 10 pm particles in any proportion .

[0068] The conversion element 1 of the exemplary embodiment of figure 2 corresponds essentially to the conversion element 1 of the exemplary embodiment shown in figure 1 . In contrast , the second segment 3 of the exemplary embodiment of figure 2 is a ceramic, in particular a low-scattering ceramic, of the second phosphor 31 .

[0069] Figure 3A shows a perspective view of a conversion element 1 as shown in figures 1A to 1C and 2 . The interface 4 of the first segment 2 and the second segment 3 comprises , in particular consists of , the curved surface area of the cylinder-shaped second segment 3 .

[0070] Figure 3B shows a perspective view of a comparative example of a conversion element 100 comprising a first layer 200 comprising a first phosphor and a second layer 300 comprising a second phosphor in a vertical arrangement. The interface 400 of the first layer 200 and the second layer 300 comprises, in particular consists of, the area of the main surface of the conversion element 100.

[0071] The interface 4 between the first segment 2 and the second segment 3 as well as the interface 400 between the first layer 200 and the second layer 300 can be used as an indication for the likelihood of a re-absorption event to occur. For a conversion element that has overall lateral dimensions of 1.0 mm x 1.0 mm, the area of the interface 400 of the conversion element 100 is 1.0 mm2(see figure 3B) . In contrast, the area of the interface 4 of the conversion element 1 (see figure 3A) is much less for the configurations of relevance.

[0072] Figure 4 shows a contour plot of the area A of the interface 4 of the first segment 2 and the second segment 3 of a conversion element 1 described herein. Figure 4 demonstrates the difference between the two areas of the interfaces 4, 400 shown in figure 3A and 3B for varying sizes of the conversion elements 1, 100. In this instance, in all cases, the edge lengths of the conversion elements 1, 100 are 1.0 mm x 1.0 mm. Therefore, the area of the interface 400 for the conversion element 100 is always 1.0 mm2. For the conversion element 1, the area A of the interface 4 changes as a function of cylinder radius r and thickness x of the conversion element 1. For the thicknesses x and cylinder radii r shown in figure 4, the area a of the interface 4 is always less than 1.0 mm2. The conversion element 1 according to the exemplary embodiments of figures 1A to 1C can be produced by the method for producing a conversion element 1 as described in conj unction with figures 5A to 5G . Figures 5A and 5C to 5G show top views and figure 5B shows a side view .

[0073] In the method step shown in figure 5A, a first green-state tape 6 comprising a first phosphor 21 is provided . For example , the first phosphor 21 is combined with a binder and optionally other additives such as flux materials and together formed into flat sheets or tapes using, for example , tape casting . Optionally, a plurality of sheets or tapes can be laminated together to form a laminate 61 ( figure 5B ) .

[0074] In the method step shown in figure 5C, a plurality of recesses 5 is formed in the first green-state tape 6 , for example by dicing or punching . In particular, cutouts 62 are diced or punched from the first green-state tape 6 .

[0075] In the method step shown in figure 5D, a tool 8 , for example a punching tool or a dicing tool , is placed on the first green-state tape 6 . Individual first green-state tapes 6 each comprising one recess 5 are formed, for example by punching or dicing ( figure 5E ) . Subsequently, the binder and the optional additives are burned out and the remaining material is densi fied by sintering, for example through a high temperature treatment , to form a ceramic first segment 2 of the first phosphor 21 comprising a recess 5 ( figure 5F) .

[0076] In the method step shown in figure 5G, a second segment 3 is provided in the recess 5 . A second phosphor 31 is mixed with a matrix precursor such as a polysiloxane precursor and optional filler particles and an optional third phosphor to make a slurry . The slurry is deposited in the recess 5 of the first segment 2 . Subsequently, the matrix precursor is cured to form the matrix material 34 . Thus , the second segment 3 comprising the second phosphor 31 and the matrix material 34 is formed in the recess of the ceramic first segment 2 .

[0077] The conversion element 1 according to the exemplary embodiments of figure 2 can be produced by the method for producing a conversion element 1 as described in conj unction with figures 6A to 6G . Figures 6A and 6C to 6G show top views and figure 6B shows a side view .

[0078] In the method step shown in figure 6A, a first green-state tape 6 comprising a first phosphor 21 and a second greenstate tape 7 comprising a second phosphor 31 are provided . For example , the first phosphor 21 or the second phosphor 31 , respectively, is combined with a binder and optionally other additives such as flux materials and together formed into flat sheets or tapes using, for example , tape casting . Optionally, a plurality of sheets or tapes can be laminated together to form laminates 61 , 71 ( figure 6B ) .

[0079] In the method step shown in figure 6C, a plurality of recesses 5 is formed in the first green-state tape 6 and in the second green-state tape 7 , for example by dicing or punching . In particular, cutouts 62 and cutouts 72 are diced or punched from the first green-state tape 6 and the second green-state tape 7 , respectively . The recesses 5 of the first green-state tape 6 and the second green-state tape 7 have the same shape . As a consequence , cutouts 62 and cutouts 72 also have the same shape . In the method step shown in figure 6D, a tool 8 , for example a punching tool or a dicing tool , is placed on the first green-state tape 6 . Individual first green-state tapes 6 each comprising one recess 5 are formed, for example by punching or dicing ( figure 6E ) . Subsequently, a cutout 72 from the second green-state tape 7 is deposited in the recess 5 of the individual first green states tape 6 ( figure 6F) . Subsequently, the binder and the optional additives are burned out and the remaining material is densi fied by sintering, for example through a high temperature treatment , to form a ceramic second segment 3 of the second phosphor 31 laterally surrounded by a ceramic first segment 2 of the first phosphor 21 ( figure 6G) .

[0080] The optoelectronic device 10 of the exemplary embodiment of figure 7 comprises a semiconductor chip 20 configured to emit electromagnetic radiation of a first wavelength range . The semiconductor chip 20 can be a micro-LED . For example , the first wavelength range is in the blue spectral range , for instance 450 nm .

[0081] A conversion element 1 as described herein is arranged on a radiation exit surface of the semiconductor chip 20 . The conversion element 1 can be arranged directly on the radiation exit surface or in a distance to the radiation exit surface . The conversion element 1 can be in the form of a platelet . In particular, the platelet is glued directly to the semiconductor chip 20 , for example via a silicone glue . The conversion element 1 converts at least a part of the electromagnetic radiation of the first wavelength range into electromagnetic radiation of a second wavelength range and electromagnetic radiation of a third wavelength range . Table 1 shows the data of an optoelectronic device comprising a conversion layer having a mixture of two phoshors (mixed conversion layer) and of an optoelectronic device 10 described herein comprising a conversion element 1 described herein. Both optoelectronic devices comprise a semiconductor chip 20 emitting a first wavelength range in the blue spectral range with known reflective properties of the chip mirror and absorbing properties of non-emitting exposed surfaces. In both cases, the targeted color point was (Cx,Cy) = (0.563, 0.429) . Phosphor amounts and converter dimensions were chosen to match that color point in both cases. On the basis of light output, the conversion element 1 offers a 3.6 % improvement. On the basis of brightness in lumens, this improvement is 1.2 %.

[0082] Table 1

[0083] The design intent of reduced re-absorption can be evaluated with a budget plot of power flow to the loss channels LI, L2, L3, shown in Figure 8 for both the optoelectronic device comprising the mixed conversion layer (data 8-1) and the optoelectronic device 10 described herein (data 8-2) . The power P in W is shown for the light output W, the conversion loss channel LI, the chip surface loss channel L2, and the mirror loss channel L3. Figure 8 shows that the most significant contributor to higher brightness is the lower conversion loss ( LI ) for the optoelectronic device 10 described herein . This is a direct consequence of how the conversion element 1 success fully reduces that amount of reabsorbed light through the lateral configuration of the first segment 2 and the second segment 3 and a reduced area of the interface 4 . The conversion element 1 that obtained this brightness has dimensions 1150 x 1150 x 170 pm . The radius of the cylindrical second segment 2 is 440 pm .

[0084] The features and exemplary embodiments described in connection with the figures can be combined with each other according to further exemplary embodiments , even i f not all combinations are explicitly described . Furthermore , the exemplary embodiments described in connection with the figures may have alternative or additional features as described in the general part .

[0085] The invention is not restricted to the exemplary embodiments by the description on the basis of said exemplary embodiments . Rather, the invention encompasses any new feature and also any combination of features , which in particular comprises any combination of features in the patent claims and any combination of features in the exemplary embodiments , even i f this feature or this combination itsel f is not explicitly speci fied in the patent claims or exemplary embodiments .

[0086] This patent application claims the priority of US provisional patent application 63 / 562 , 494 , the disclosure content of which is hereby incorporated by reference . References

[0087] 1 conversion element

[0088] 11 main surface

[0089] 12 main surface

[0090] 2 first segment

[0091] 21 first phosphor

[0092] 22 side surface

[0093] 23 side surface

[0094] 3 second segment

[0095] 31 second phosphor

[0096] 32 side surface

[0097] 33 side surface

[0098] 34 matrix material

[0099] 4 interface

[0100] 5 recess

[0101] 6 first green-state tape

[0102] 61 laminate

[0103] 62 cutout

[0104] 7 second green state tape

[0105] 71 laminate

[0106] 72 cutout

[0107] 8 tool

[0108] 20 semiconductor chip

[0109] 100 conversion element

[0110] 200 first layer

[0111] 300 second layer

[0112] 400 interface x thickness r radius A4area of the interface

[0113] W light output

[0114] LI conversion loss channel

[0115] L2 chip surface loss channel L3 mirror loss channel

[0116] 8- 1 data

[0117] 8-2 data

Claims

Claims1. A conversion element (1) comprising- a first segment (2) comprising a first phosphor (21) , wherein the first segment (2) is configured to convert electromagnetic radiation of a first wavelength range into electromagnetic radiation of a second wavelength range, and- a second segment (3) comprising a second phosphor (31) , wherein the second segment (3) is configured to convert electromagnetic radiation of the first wavelength range into electromagnetic radiation of a third wavelength range, and wherein the first segment (2) laterally surrounds the second segment (3) in a main extension plane of the conversion element ( 1 ) .

2. The conversion element (1) according to the preceding claim, wherein side surfaces (32, 33) of the second segment (3) parallel to the main extension plane of the conversion element (1) are free of the first segment (2) .

3. The conversion element (1) according to at least one of the preceding claims, wherein a thickness (x) of conversion element (1) is between and including 100 pm and 200 pm.

4. The conversion element (1) according to at least one of the preceding claims, wherein the conversion element (1) has the form of a platelet .

5. The conversion element (1) according to at least one of the preceding claims, wherein an area of an interface (4) of the first segment (2) and the second segment (3) is smaller than an area of a main surface (11) of the conversion element (1) parallel to the main extension plane of the conversion element (1) .

6. The conversion element (1) according to at least one of the preceding claims, wherein the first segment (2) is a ceramic layer of the first phosphor (21) .

7. The conversion element (1) according to at least one of the preceding claims, wherein the second segment (3) is a ceramic layer of the second phosphor (31) .

8. The conversion element (1) according to at least one of the claims 1 to 6, wherein the second segment (3) comprises the second phosphor (31) in a matrix material (34) .

9. The conversion element (1) according to the preceding claim, wherein the matrix material (34) comprises polysiloxane, silicone, or glass.

10. The conversion element (1) according to at least one of the claims 8 or 9, wherein the second segment (3) further comprises a third phosphor .

11. The conversion element (1) according to at least one of the claims 8 to 10, wherein the second segment (3) further comprises filler particles .

12. The conversion element (1) according to at least one of the preceding claims, wherein the second segment (3) has the form of a cylinder, and wherein a radius of the second segment is smaller than half of the smallest extension of the conversion element (1) in the main extension plane of the conversion element (1) .

13. The conversion element (1) according to the preceding claim, wherein the radius of the second segment (3) is between and including 400 pm and 500 pm.

14. A method for producing a conversion element (1) comprising- providing a first segment (2) comprising a first phosphor (21) , wherein the first segment (2) comprises a recess (6) , wherein the recess (6) extends through the first segment (2) perpendicular to a main extension plane of the first segment(2) ,- providing a second segment (3) comprising a second phosphor (31) in the recess (6) .

15. The method according to the preceding claim, wherein providing the first segment (2) comprises- providing a first green-state tape (7) comprising the first phosphor (21) ,- forming the recess (6) in the first green-state tape (7) , and- sintering the first green-state tape (7) to form the first segment ( 2 ) .

16. The method according to at least one of the claims 14 or 15, wherein providing the second segment (3) comprises- providing a second green-state tape (8) comprising the second phosphor (31) ,- forming a cutout (82) from the second green-state tape (8) comprising the form of the recess (6) , and- sintering the second green-state tape (8) to form the second segment (3) .

17. The method according to at least one of the claims 14 or 15, wherein providing the second segment (3) comprises- adding the second phosphor (31) and a matrix precursor to the recess (6) , and- curing the matrix precursor to form the second segment (3) .

18. Optoelectronic device (10) comprising- a semiconductor chip (20) configured to emit electromagnetic radiation of a first wavelength range; a conversion element (1) according to at least one of the claims 1 to 13 configured to convert at least a part of the electromagnetic radiation of the first wavelength range into electromagnetic radiation of a second wavelength range and into electromagnetic radiation of a third wavelength range.