Method of integrating functional tuning materials with micro devices and structures thereof

The disclosure is related to creating different functional micro devices by integrating functional tuning materials and creating an encapsulation capsule to protect these materials. Various embodiments of the present disclosure also related to improve light extraction efficiencies of micro devices by mounting micro devices at a proximity of a corner of a pixel active area and arranging QD films with optical layers in a micro device structure.

TECHNICAL FIELD

The present invention relates to an integration of color conversion layers into a display substrate. More particularly, the present invention relates to provide an encapsulation capsule to protect the color conversion layers from environmental agents. The present invention also relates to methods and structures to improve light extraction efficiencies of micro devices by mounting micro devices at a proximity of a corner of a pixel active area covered by color conversion layers.

BACKGROUND

System performance can be enhanced by integrating different micro devices into a system substrate. The challenge is that different micro devices can have different performance and also use different material systems. These material systems are in general sensitive to environmental agents (e.g., oxygen or water). Therefore, it is desirable to provide protection to these materials to enhance system performance.

SUMMARY OF THE INVENTION

Accordingly, the present invention relates to a pixel structure comprising: a light source to generate light; a light conversion layer to convert the light to a desired color; and a light distribution structure to distribute the light from the light source onto the conversion layer.

In one embodiment, other layers can be also integrated between the light distributor layer and light source. Also, other layers can be integrated after the light conversion (e.g., quantum dot (QD)) layers.

In another embodiment, to avoid high stress points in the light conversion layer caused by high intensity light, an attenuator or blocking structure is used to reduce or block the light intensity from a direct line of sight between the light source and the light conversion (e.g., QD) layer.

In one embodiment, the light distributor is comprised of a light guide.

In another embodiment, the light distributor is comprised of reflective layers and a planarization layer.

In another embodiment, the light attenuator structure is also used as the light source electrode.

In another embodiment, the light attenuator structure is part of the light distributor structure reflective layers.

In an embodiment, the reflective layer is used as part of the light source contact.

In an embodiment, the light distribution structure comprises a thick transparent layer on top of the light source.

Another aspect of this invention is creating an encapsulation capsule to protect color conversion materials.

According to one embodiment, there is provided an optoelectronic device comprising a plurality of semiconductor layers formed on a substrate that form a top surface and a bottom surface, wherein the plurality of semiconductor layers have isolated areas that form at least one side surface, one or more cover layers form a space around the isolated areas optically coupled to the at least one side surface; and functional tuning materials disposed in the space formed by the one or more cover layers.

According to one embodiment, a pixel structure for a display may be provided. The pixel structure may comprising a substrate, a light source (e.g., a micro device) mounted at the proximity of a corner of a pixel active area or pixel active side to generate light, a color conversion layer and/or color filters may be formed on the micro device to convert the light to a desired color and a top reflector mounted on the color conversion layer and extended over the top of the area of the micro device to reflect the light back toward and through the color conversion layer. The pixel active area is where the light generation or light conversion happens. The pixel active area can be the same as the pixel area.

According to other embodiments, a LED device structure may be provided. The structure may comprise optical layers coupling the LED lights into the structure and reflect the light created by QD layers towards the optical layers.

DETAILED DESCRIPTION

While the present teachings are described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments. On the contrary, the present teachings encompass various alternatives and equivalents, as will be appreciated by those of skill in the art.

Embodiments in the present disclosure are related to the integration of a color conversion layer (e.g., QDs) into an optical substrate system, typically used in color displays. The optical substrate may comprise one or more: micro light emitting diodes (LEDs), organic LEDs, sensors, solid state devices, integrated circuits, microelectromechanical systems (MEMS), and other electronic components. The receiving substrate may be, but is not limited to, a printed circuit board (PCB), a thin-film transistor (TFT) backplane, an integrated circuit substrate, or, in one case of optical micro devices, such as LEDs, a component of a display, for example a driving circuitry backplane.

In this disclosure, the structure is described using microLED and color conversion layers. However, a similar structure can be used with other micro devices and other functional tuning materials.

The shape of the light sources used in the embodiments are for illustration purposes and may have different shapes and sizes. The light source devices may have one or more pads on the side that will contact the receiver substrate. The pads may be mechanical, electrical or a combination of both. The one or more pads may be connected to a common electrode or to a row/column of electrodes. The electrodes may be transparent or opaque. The light sources may have different layers. The light sources may be made of different materials, such as organic, inorganic, or a combination thereof.

FIG. 1illustrates a pixel structure10in accordance with an embodiment of the present invention including a substrate11with three subpixels defined by light sources12-1,12-2, and12-3mounted thereon with color conversion layers14-1,14-2,14-3(e.g., QD layers) mounted thereover. One of the light sources12-1,12-2, or12-3may have no color conversion layer. For example, if a blue light source is used, the blue subpixel may not include a color conversion layer. Here, other layers may be used on top of the color conversion layers14-1,14-2, and14-3, such as encapsulation, a color filter, or electrodes for a touch interface. The following description may use one subpixel12-1,12-2, or12-3to explain the invention, but the invention may be easily extended to a plurality of subpixels (e.g.,2to5) and a plurality of pixels for an entire display.

FIGS. 2A to 2Cillustrate exemplary embodiments of the display substrate11that includes the light sources12-1and12-2, and respective light distribution structures16-1and16-2to distribute the light before reaching the respective color conversion layers14-1and14-2. The light distribution structures may comprise transparent polymer materials, such as: methyl methacrylate styrene (MS) resins with low density, low moisture absorption, and good moldability; methyl methacrylate butadiene styrene (MBS) resins with a good balance of transparency, strength and fluidity; and transparent acrylonitrile butadiene styrene (ABS) resins. However, other high refractive index (e.g., >1.5) transparent polymer materials may be used, ideally matching the index of the micro device material.

There may be pixel circuits (not shown) on the substrate11, which may include TFTs. There may also be a planarization layer between the pixel circuits and the light sources12-1and12-2. An electrode or electrodes may connect the pixel circuits to the light source12-1and12-2. In one embodiment,FIG. 2A, the light is distributed and directed away from the substrate11to the location of the color conversion layers14-1and14-2. In another embodiment, FIG.2B, the light is directed toward and through the substrate11, which comprises a material transparent to the particular wavelengths of the light. In this case, the light conversion layer14-1may be located on the substrate11, with the light distribution structure16-1on the light conversion layer14-1, and between the light source12-1and the light conversion layers14-1. The light conversion layer (or layers)14-1may be located on the other side of the substrate11opposite the light sources12-1. There may also be a planarization layer before the light distribution structures16-1.

With reference toFIG. 7, the method to manufacture the pixel circuit comprises: step702, making at least one group of micro devices12-1and12-2on a donor substrate11according to a system substrate pattern; step704, covering the light output (input) surface of the micro devices12-1and12-2with the color conversion layers14-1and14-2and/or color filters; and step706, transferring at least one of the micro devices12-1and12-2in a group to a system substrate.

The light distribution structure16-1may be a thick transparent layer, as hereinabove described. In one example, the layer may be more than 3 μm. In another example, the side of the transparent layer may be blocked by an opaque or reflective layer(s)18for each pixel or subpixel. In another example, there may be a reflective layer19behind or on top of the light source12-1.

With reference toFIG. 2C, the sides of the light distribution structure16-1may be formed (e.g., etched) at an internal acute angle to the substrate11to form a frusto-pyramidal or frusto-conical structure. The acute angle may be between 30° and 60°, but preferably between 40° and 50°, to let light be directed outwardly from the light source12-1at 180°. Similarly, the color conversion layer14-1would cover the angled sides and the top of the light distribution structure16-1.

However, the thickness of the light distribution structure16-1may be too large, if the ratio of pixel area to light source area is too big. To eliminate the need for a thick light distribution structure16-1,FIGS. 3A and 3Billustrate embodiments including a light distribution structure34with a light attenuator38mounted thereon for reducing the hot spot effect. The light attenuator38reduces the light intensity from a direct line of sight from a light source32. In the illustrated embodiment, the attenuator38may be comprised of a material opaque to the wavelength of the light thereby blocking direct light from the light source from hitting the light conversion layer36. The attenuator structure38may act as the contact or electrode of the light source32. The light attenuator38may include at least one of a semi-transparent, opaque, and a reflective layer. The attenuator38may also be an optical structure that redirects the light. The light attenuator38may be a part of the light distribution layer34. The light attenuator structure38may be directly on top of the light source32or there may be other layers between the light source32and the light attenuator structure38. There may be layers (e.g., of the light distribution structure34) between the light attenuator structure38and the light conversion layer36. The attenuator38may be directly on or connected to the light conversion layer36. Also, the light conversion layer36may cover the whole or part of the area over the light attenuator structure38.FIG. 3Billustrates an alternate embodiment, in which the light source32directs the light through the substrate30, which is transparent to wavelengths in the light, whereby the light conversion layer36may be mounted directly on or over the substrate30, with the light distribution layer34and the attenuator38mounted between the light conversion layer36and the light source32.

With reference toFIG. 8, the method to manufacture the pixel circuit comprises: step802, making at least one group of micro devices32on a donor substrate30according to a system substrate pattern; step804, covering or blocking undesired light paths from the micro devices32with opaque or reflective materials (e.g., light attenuator38); step806, covering the light output (input) surface of the micro devices32with the color conversion layers36and/or color filters; and step808, transferring at least one of the micro devices32in a group to a system substrate.

There are several ways to implement the attenuator structure38and/or the light distribution structure34.FIGS. 4A and 4Billustrate embodiments in which the light is guided to the sides from a light source42and either a top layer44-3(FIG. 4A) or bottom layer44-4(FIG. 4B) of a light distribution structure44-1enables the light to pass through. A reflector (or a blocking layer)44-2extending along the sides of the light distribution structure44-1is used to reflect the light back through the light distribution structure44-1. The reflector44-2may be at an acute angle to the substrate40to reflect the light out through the top layer44-3or bottom layer44-4of the light distribution structure44-1. The light passes through the top layer44-3(FIG. 4A) or the bottom layer44-4(FIG. 4B) and then passes through the light conversion layer46-1. An attenuator structure48mounted on or over the light source42is used to reduce hot spots caused by direct line of sight transmission of light from the light source42. The attenuator structure48may also comprise a connection electrode for the light source42. There can be layers before46-2and after46-3the light conversion layer46-1. These layers can have different functionalities.FIG. 4Billustrates an alternate embodiment, in which the light source42directs the light through the substrate40, which is transparent to wavelengths in the light, whereby the light conversion layer46-1may be mounted directly on or over the substrate40, with the light distribution layer44-1and/or the attenuator48mounted between the light conversion layer46-1and the light source42.

With reference toFIG. 9, the method to manufacture the pixel circuit comprises: step902, making at least one group of micro devices42on a donor substrate40according to a system substrate pattern; step904, covering or blocking undesired light paths from the micro devices42with opaque or reflective materials (e.g., light attenuator48); step906, covering the light output (input) surface of the micro devices42with the color conversion layers46-1and/or color filters; step908, depositing layers46-2and46-3before and/or after the color conversion layers46-1for encapsulation and/or heat dissipation; and step910, transferring at least one of the micro devices42in a group to a system substrate.

Another configuration for a light distribution and a light attenuator structure is demonstrated inFIGS. 5A to 5F. InFIGS. 5A and 5B, a subpixel51includes a base reflector layer54-3mounted on a substrate50with a light source52mounted thereon. A light distribution layer54-1is disposed over the light source52and the base reflector layer54-3. The light distribution layer54-1includes sides formed (e.g., etched) at an acute angle (e.g., 30°-60°), ideally 40°-50°, to the substrate50to form a frusto-pyramidal or frusto-conical shape. The angled sides of the light distribution layer54-1are then covered (e.g., coated) with angled side reflectors54-2at the same angle to the substrate50. An attenuator58is mounted on or over the light source52to prevent a direct line of sight from the light source52to a light conversion layer56-1disposed over the light distribution layer54-1. Additional layers56-2and56-3may also be provided. The base reflector54-3and the angled side reflectors54-2redirect the light from the light source52, perhaps multiple times, back through the light conversion layer56-1and then finally out through the light conversion layer56-1. The attenuator layer58may also act as a reflecting layer and reflect the light from the light source52toward the base reflector54-3. The combination of reflectors54-3,54-2, and58reduces the hot spot problem (i.e., the high light intensity at a direct line of sight from the light source52to the light conversion layer56-1) and distributes the light across the pixel51.FIG. 5Billustrates an embodiment in which the light distribution layer54-1is mounted (e.g., coated) over the entire base reflector54-3with the angled side reflectors54-2extending down to the substrate50, in contrast toFIG. 5B, in which the base reflector54-3extends the entire width of the pixel51, whereby the angled side reflectors54-2extend proximate to the base reflector54-3.

FIGS. 5C and 5Dare substantially identical toFIGS. 5A and 5B, except that the attenuator58is mounted directly on the light source52, and acts as a contact layer therefor. The contact58may be electrical or just mechanical. The contact58may be connected to some other structure (e.g., electrical traces or mechanical structure) through a via. The contact58may also be connected to the angled side reflectors54-2through a patterned trace or through a common electrode. The contact58may also be connected to a common electrode. In this case, the common electrode can be deposited on top of the attenuator58after a possible dielectric layer with an opening at the attenuator58. The common electrode may be either patterned into rows or columns or a single layer that connects an array of the pixels51C or51D in the display. The base reflector layer54-3may be extended beyond the angled side reflector layer54-2, as hereinbefore discussed. In the case where the base reflector layer54-3is not extended beyond the angled side layer54-2, the angled side layer54-2may cover the whole pixel structure51, as demonstrated inFIGS. 5B and 5D.

With reference toFIG. 10A, the method to manufacture the pixel circuit comprises: step1002, making at least one group of micro devices52on a donor substrate50according to a system substrate pattern; step1004, covering or blocking undesired light paths from the micro devices52with opaque or reflective materials (e.g., light attenuator58); step1006, covering the light output (input) surface of the micro devices52with the color conversion layers56-1and/or color filters, wherein the color conversion layers may include a dielectric layer for passivation; step1008, depositing layers56-2and56-3before and/or after the color conversion layers56-1for encapsulation and/or heat dissipation; and step1010, transferring at least one of the micro devices52in a group to a system substrate.

In the embodiment illustrated inFIGS. 5E and 5F, the light distribution layer54-1is substantially the same as inFIGS. 5A to 5D, but the light conversion layer56-1is mounted (e.g., coated) proximate to the substrate50, whereby the light is directed from the light source52through the substrate50, which is transparent to wavelengths in the light. The attenuator58is positioned on or above the light conversion layer56-1between the light source52and the light conversion layer56-1. A cover reflector54-4(e.g., a reflective coating) is disposed over the entire light distribution layer54-1, including the angled sides, to reflect the light back toward and through the color conversion layer56-1, and the substrate50. There may be layers before56-2and after56-3the light conversion layer56-1. InFIG. 5F, at least a portion of the cover reflector54-4may contact the light source52directly, and act as a contact for the light source52.

With reference toFIG. 10B, the method to manufacture the pixel circuit comprises: step1002, making at least one group of micro devices52on a donor substrate50according to a system substrate pattern; step1004, covering or blocking undesired light paths from the micro devices52with opaque or reflective materials (e.g., light attenuator58); step1006, covering the light output (input) surface of the micro devices52with the color conversion layers56-1and/or color filters, wherein one of the color conversion layers or the light attenuator58may include a conductive layer acting as an electrode for the micro device52; step1008, depositing layers56-2and56-3before and/or after the color conversion layers56-1for encapsulation and/or heat dissipation; and step1010, transferring at least one of the micro devices52in a group to a system substrate.

FIGS. 6A and 6Billustrate another embodiment of a subpixel structure61that includes a light distribution structure64with diverging sides in the direction of light transmission formed at an obtuse internal angle to a substrate60(acute external angle). A base reflector layer64-2, provided on the bottom and angled side surfaces of the light distribution layer64, also at the same angle as the sides of the light distribution structure64, reflects the light from a light source62away from the substrate60and up through a light conversion layer66-1. A light attenuator68mounted over the light source62(e.g., on a top surface of the light distribution layer64) eliminates hot spot effects on the light conversion layer66-1. The embodiment illustrated inFIG. 6Bis substantially the same as the one inFIG. 6A, except that the light attenuator structure68extends into contact with the light source62, and thereby may act as a contact for the light source62to an external source of electricity.

In all the structures, the conversion layer66-1may be deposited over a bank structure66-2, in which a generally organic or dielectric layer is deposited. The bank structure layer66-2may be patterned to open the layer in the area where light conversion layer66-1will be deposited.

With reference toFIGS. 11ato 11c, the transfer process is illustrated, in which a donor substrate1102initially includes three micro devices1104. Each of the micro devices1104includes an electrode1106, which may be transparent, but ideally comprises an opaque or reflective material providing a light attenuator function. The middle micro device1104includes (e.g., is coated with) a first color conversion or filter layer1108to convert the emitted light from the micro device1104into a different color. The left micro device1104includes (e.g., is coated with) a second color conversion or filter layer1110to convert the light emitting from the micro device1104into a third color. Together, the three micro devices1104may comprise the three different colors (i.e., red, green, and blue) required to form a pixel for a display device.

In a first embodiment, the three micro devices1104are transferred to a cartridge substrate and provided with a second electrode1116mounted on the opposite end of the micro device1104as the electrode1106. The second electrode1116may be comprised of an opaque or reflective material to redirect any light from the micro device1104back through any light distribution material, around any light attenuator structure, and through any color conversion layer1108or1110. Each of the micro devices1104are then mounted on pads1114on a receiver substrate1112(FIG. 11b), with the second electrode1116in electrical contact with the pad1114.

Alternatively, as illustrated inFIG. 11c, the three micro devices1104may be directly transferred to the receiver substrate1112with the electrode1106in contact with the pads1114. In this embodiment, the receiver substrate1112and the pads1114may be transparent to the light emitted from the micro devices1104and any subsequent conversion.

Encapsulating Functional Tuning Materials

One method to improve system performance is to integrate different micro devices into a system substrate. The challenge is that different micro devices can have different performance and also use different material systems. The embodiments described below are related to creating different functional micro devices (e.g., red, green, blue LED, or a sensor from a single blue LED) by integrating functional tuning materials (e.g., a color conversion layer). As functional tuning materials are in general sensitive to environmental agents (e.g., oxygen or water), encapsulation

FIG. 12Ashows a micro device1200embedded in functional tuning/alteration/modifying materials1210. The functional tuning/alternation materials are referred to as color conversion layers as an example in the rest of the description. In addition, the embodiment exemplarily illustrated one micro device1200, but the invention is not limited thereto. The number of micro devices1200may be changed.

Here, a plurality of semiconductor layers is formed/transferred into a substrate forming a top surface1200-1and a bottom surface1200-2. The plurality of the semiconductor layers are isolated in different areas forming microdevices (a micro device1200is shown as an example) with at least one side surface1200-3(or1200-4). Here, the micro device1200can have at least one contact (via)1202,1204on one side of the device (or just on one side). The contacts1202,1204connect the device1200to pads1206and1208. The micro device1200may have a stack of different layers such as active layers sandwiched between charge blocking layers and doping layers. A space formed around the micro device1200created by at least one cover layer which is optically coupled to the at least one side surface1200-3(or1200-4). There is a housing structure formed around the device consisting of cover walls1212,1214,1216, and1218. The top and bottom cover walls (layers)1212and1214extend beyond the top and bottom surface of the micro device1200. The functional tuning materials (e.g. color conversion materials)1210are inside the housing structure. The cover walls1212,1214,1216, and1218can be encapsulation layers to protect the color conversion materials from oxygen and moisture. The color conversion materials can be phosphor or quantum dots. In addition, the cover walls can include optical enhancement layers with some optical property to enhance the light coupling into the color conversion materials. In one case, the cover wall1212or1216can be reflective layers to reflect the light into the color conversion materials. In another case, the cover wall1212or1216are designed to only reflect small wavelengths (e.g., smaller than 450 nm) while allowing longer wavelength to go through. This allows the converted light to pass through the wall. In another case, the wall1214enhances the light extraction from the micro device1200into color conversion material1210. In one example, the wall1218is reflective to reflect back the lights. In another case, the wall1218is transparent to allow at least some wavelength to pass through.

With reference toFIG. 12B, the cover wall1212or1216can have two parts: a reflective part1220and a transparent part. The reflective layer1220is extended on top (or can be extended to the bottom) side of the device1200. In one case, the transparent part can also be transparent only to a portion of the wavelength to block the micro device light that goes out directly without being converted.

In another case shown inFIG. 12C, color filter layers1222can be deposited on at least one of the walls to further prevent some of the wavelength from leaving the structure/device1200or enter the color conversion material1210from the outside.

FIG. 13Ashows a cross-sectional view of a micro device1300with contacts1302and1304on either the top or bottom side of the micro device. A pad1306can couple to the device1300through at least one of the contacts (e.g., the contact1302at the top side). In one case, a layer1312that can be a dielectric layer covers the part of the device surface that is not covered by the contact1302. There can be sidewall layers1314around the micro device which may have different functions such as a passivation layer, optical enhancement layer, or encapsulation layer. Here, a buffer layer or sacrificial layers1332may be provided between the micro device1300and a substrate1330.

FIG. 13Bshows a cross-sectional view where encapsulation walls1312A and1312B are formed around the micro device1300. The encapsulation layer1312A can be the same as sidewall layers1314. These sidewall layers1314can be deposited by different means such as printing, evaporation, sputtering or more. The sidewall layers can be patterned by traditional photolithography, liftoff, or printing.

FIG. 13Cshows a cross-sectional view of the color conversion materials are formed on top of the encapsulation walls1312A and1312B. The color conversion layers1310can cover the side of the device1300not facing the substrate1330.

FIG. 13Dshows a cross-sectional view of the micro device structure where the cover walls1316and1318are formed to enclose the color conversion material between the cover walls1318,1312, and1316.

FIG. 13Eshows another cross-sectional view wherein a plurality of other walls can also be mounted on the micro device. The plurality of other layers may have a stack of different layers with different functionalities. In one case, the walls can include a reflective (e.g., total or selective) layer1312C and encapsulation layers1312B.

In another embodiment, the color conversion layer can be on a top or bottom surface of the micro device1300. In one example as shown inFIG. 13F, if there is a contact on the same surface, the contact1304height will be increased to extend beyond the color conversion layer on that surface. It is possible to add walls1320to cover the side of the contact1304and the said surface of the micro device1300.

FIG. 14Ashows another embodiment wherein the contact1404A on one of the surfaces may be connected to a contact1302area on the opposite side of the device1300through a trace1404B. The trace can be separated from the device by a dielectric layer. The trace needs to be coupled with the color conversion layers, and transparent in some areas to allow the light to pass through it. In another case, the trace covers only part of the side of the micro device so that the light can pass through other areas. For better encapsulation, the wall layers1312A and1312B used for encapsulation are formed after the trace1404B.

In another embodiment, the color conversion layers can be on a top or bottom surface of the micro device1300. In one example as shown inFIG. 14B, if there is a contact on the same surface, the contact1404A is transferred to another contact1404C on the other area with trace1404B. Here, a wall can cover the contact1404A, trace1404B, and the surface of the micro device for an optical or encapsulation function.

In the above embodiment, the cover walls on the top and bottom surface and the one on the side can be extensions of each other to offer better protection. In another case, the cover wall (layer) used on the side can extend over the bottom or top cover walls (layers).

In summary, the above embodiments provide many ways to encapsulate color conversion layers around the micro devices.

Improved Light Extraction Efficiencies

Further, various embodiments may be provided to improve light extraction efficiencies of micro devices by mounting micro devices at a proximity of a corner of a pixel active area.

According to one embodiment, a pixel structure for a display may be provided. The pixel structure may comprising a substrate, a light source (e.g., a micro device) mounted at the proximity of a corner of a pixel active area or pixel active side to generate light, a color conversion layer and/or color filters may be formed on the micro device to convert the light to a desired color and a top reflector mounted on the color conversion layer and extended over the top of the area of the micro device to reflect the light back toward and through the color conversion layer. The pixel active area is where the light generation or light conversion happens. The pixel active area can be the same as the pixel area.

In another case, a wall can surround part or all of the pixel area. A reflective layer covering the wall while the same or a different reflector layer is covering part of the micro device facing away from the pixel area to reflect the light toward the pixel area. The color conversion layer and/or color filter is formed on part or all of the pixel area.

In one aspect, the top reflector may act as a conductive electrode for coupling the micro device to a signal source such as a voltage or current source. In another embodiment, the reflective layer(s) can be also touch sensor electrodes.

In one embodiment, other layers may be used on top of color conversion layers such as encapsulation layers, color filters, or electrodes for a touch interface.

In another embodiment, a bottom reflector may be disposed between the micro device (pixel area) and the substrate for reflecting the light back from the micro device. This electrode can be another micro device electrode or a touch electrode.

In one case, the top reflector may be patterned to block escape the light from the pixel area.

In another case, if the bottom reflector is a metal, the bottom reflector may act as an electrode. In one embodiment, the bottom reflector may be patterned to open an area to let light be directed outwardly from the micro device.

FIG. 15Ashows a pixel structure with color conversion layer on top of a micro device in accordance with an embodiment of the present invention. A pixel structure1502comprising a substrate, a micro device1510may be mounted at the proximity of a corner of the pixel active area or pixel active side to generate light. The light output surface of the micro device1510may be covered by color conversion layers and/or color filters1504. The color conversion layers may comprise e.g. phosphor or quantum dots (QD). Here, other layers such as encapsulation layers, color filters, or electrodes may be used on top of the color conversion layers. A reflector/reflective layer1508may be mounted on the color conversion layers and extended over the top of the area of the micro device to reflect the light back toward and through the color conversion layer. The reflector1508may be patterned to block escaping the light out from the pixel area. Being micro device mounted at the proximity of a corner, this pixel structure can offer better light extraction, higher fill factor and better performance.

In one embodiment, a wall(s)1506can surround part or all of the pixel area. A reflective layer covering the wall while the same or a different reflector layer is covering part of the micro device facing away from the pixel area to reflect the light toward the pixel area. The color conversion layer and/or color filter is formed on part or all of the pixel area.

In one embodiment, pixel driving backplane can be integrated on top of the sample. In another case, the pixel driving backplane can be integrated before the color conversion layer.

Black matrix can be used on the surface facing away from the light to reduce the reflectivity of the surface for enhancing the contrast.

FIG. 15Bshows a cross sectional view of pixel structure including a micro device and color conversion layers corresponding toFIG. 15A. Here, a display substrate may be provided. The substrate1524may be an optical substrate that may comprises micro LED or a receiving substrate. The receiving substrate may be, but is not limited to, a printed circuit board (PCB), a thin-film transistor (TFT) backplane, an integrated circuit substrate, or, in one case of optical micro devices, such as LEDs, a component of a display, for example a driving circuitry backplane. A bottom reflector1526may be disposed over the substrate used to reflect light back from the micro device. The micro device may be mounted at the proximity of a corner of the pixel area or pixel side to generate light. In one embodiment, an optional dielectric layer1528may be deposited over the bottom reflector1526to separate the bottom reflector from the micro device.

In one case, if the bottom reflector is a metal, the bottom reflector may act as an electrode to connect the pixel circuit to the micro device. In other embodiments, an optical stage1530may be provided on the side of the micro device with some optical property to enhance the light coupling into the color conversion materials.

The color conversion layers1532may be mounted on the micro device to convert the light to a desired color. A top reflector1522may also be disposed over the color conversion layers to reflect light back from the color conversion layer and may be patterned to open an area1540to let light be directed outwardly from the micro device.

In one embodiment, pixel driving backplane can be integrated on top of the sample. In another case, the pixel driving backplane can be integrated before the color conversion layer.

Black matrix can be used on the surface facing away from the light to reduce the reflectivity of the surface for enhancing the contrast.

FIG. 15Cshows another cross sectional view of pixel structure. Here, the top reflector1522-C may be fully disposed on and over on one side of the micro device1520and color conversion layers1532and the bottom reflector1526-C may be patterned to open an area to let light be directed outwardly from the micro device.

FIG. 15Dshows another cross sectional view of pixel structure. Here, the top reflector1522-D may be deposited over the micro device1520before disposition of the color conversion layers1540-D. The top reflector1522-D may be partially patterned and disposed to cover a part of the micro device. An additional plurality of walls/layers1542may be provided. These additional walls/layers1542may comprises a dielectric layer, a polymer, a stack of metals or another reflector.

FIG. 16Ashows a configuration of a plurality of pixel structures having a common electrode either as one of micro device electrode or a touch sensor in accordance with an embodiment of the present invention. Here, for an example, four different pixel structure may be used wherein respective micro device (e.g.,1602-1,1602-2,1602-3and1602-4) is mounted on the proximity of a corner of each pixel structure. The pixel structures mounted in such a way that light output surface of each micro device is facing each other. The light output surface of each micro device may be covered by respective color conversion layers and/or color filters (e.g.,1604-1,1604-2,1604-3and1604-4). The top reflector mounted on color conversion layer of each pixel structure may act as an electrode and may also act as a common electrode1606for each pixel structure to connect to the micro device.

In one case, the reflective layer(s) can be also touch sensor electrodes. The micro devices can be located in different corners of the pixels (or sub pixels). In this embodiment, the micro devices in one pixel for different sub pixels are located closer to each other.

FIG. 16Bshows another configuration of a plurality of pixel structures having a common electrode in accordance with an embodiment of the present invention. In this case, the micro devices in subpixels related to one pixel can be further away from each other as demonstrated inFIG. 16B. The top reflector can cover part of the micro device specially if it only covering the micro device.

FIG. 16Cshows another configuration of a plurality of pixel structures having a common electrode in accordance with an embodiment of the present invention. In this case, the top reflector or an extra reflector covering QD layers can extend over the micro device.

In summary, the above embodiments provide many ways to mount micro devices at a proximity of a corner of a pixel active area to improve light extraction efficiencies of micro devices.

Optical Layer Integration with Micro Device Substrate

Furthermore, this disclosure is related to integration of optical layer(s) in a micro device structure. The micro device structure may comprise micro light emitting diodes (LEDs), organic LEDs, sensors, solid state devices, integrated circuits, MEMS, and/or other electronic components.

In one embodiment, the micro device may comprise at least one color conversion layers. In one embodiment, color conversion layers may include phosphor or quantum dots (QD). In another embodiment, the micro device may comprise one or more optical layers.

In yet another embodiment, a first optical layer may couple micro device light into the micro device structure and reflect the light created by a first color conversion layer towards a second optical layer.

In another embodiment, the second optical layer may couple remaining light from the LED and light generated by the first color conversion layer into a second color conversion layer. It may prevent the light from the second color conversion layer to go back to the first color conversion layer.

In one embodiment, the first color conversion layer may generate a higher wavelength light e.g, red and the second color conversion layer may generate a mid range wavelength light e.g, green.

In one case, color conversion layers may be color conversion layers embedded in a film (e.g. polymers). In another case, color conversion layers may be a continuous layer (e.g. mono layer) covered by passivation layer.

In another embodiment, the first color conversion layer may generate mid range wavelength (e.g. green) and the second color conversion layer may generate longer wavelengths (e.g. red).

In this case, the light generated by the first color conversion layer may also be converted by the second color conversion layer into longer wavelength light. Therefore, the second color conversion layer concentration may be controlled to only convert predefined percentage of the first color conversion layer light into the second color conversion layer light.

In yet another embodiment, the light entity of the first color conversion layer or a second color conversion layer light may also be modulated by adding a third optical film on top of the structure (for this structure, the first color conversion layer or a second color conversion layer can be mixed in one film as well). For example, for area where more red is needed, an optical film can be added on the top to reflect a percentage the light (either as selective by wavelength or general) back into the QD films. In such case, the mid wavelength (e.g. green) will be absorbed more by the QD films and generate more longer wavelength light (e.g. red). Various embodiments in accordance with the present structures and processes provided are described below in detail.

FIG. 17shows an arrangement of color conversion films/color filters in a micro device structure, according to one embodiment of the invention. Here, a color conversion layer is used to convert the blue light of three subpixels to combine green and red color. The color filter is for each sub pixel to only allow the corresponding light out. To save power, one sub pixel has no color filter1702. In this case, if a pixel required a combination of red and green color, the sub pixel with no color filter can be used to generate all or part of the combined color. Furthermore, one sub pixel has no color conversion and therefore generate blue color only.

FIG. 18Ashows an arrangement of QD films with optical layers in a micro device structure, in accordance with an embodiment of the present invention. Here, the micro device1820may comprise one or more optical layers. A first optical layer1802may couple micro device1820light into the micro device structure and reflect the light created by a first color conversion layer1802towards a second optical layer1804. The second optical layer1804may couple remaining light from the LED and light generated by the first color conversion layer1808into a second color conversion layer1810. It may prevent the light from the second color conversion layer1810to go back to the first color conversion layer1808.

In one embodiment, the first color conversion layer1808may generate a higher wavelength light e.g, red and the second color conversion layer1810may generate a mid-range wavelength light e.g, green. In one case, color conversion layers may be color conversion layers embedded in a film (e.g. polymers). In another case, color conversion layers may be a continuous layer (e.g. mono layer) covered by passivation layer. In another embodiment, the first color conversion layer1808may generate mid-range wavelength (e.g. green) and the second color conversion layer1810may generate longer wavelengths (e.g. red).

In this case, the light generated by the first color conversion layer1808may also be converted by the second color conversion layer1810into longer wavelength light. Therefore, the second color conversion layer concentration may be controlled to only convert predefined percentage of the first color conversion layer light into the second color conversion layer light.

In yet another embodiment, the light entity of the first color conversion layer or a second color conversion layer light may also be modulated by adding a third optical film1806on top of the structure (for this structure, the first color conversion layer or a second color conversion layer can be mixed in one film as well). For example, for area that more red is needed, an optical film can be added on the top to reflect a percentage the light (either as selective by wavelength or general) back into the QD films. In such case, the mid wavelength (e.g. green) will be absorbed more by the QD films and generate more longer wavelength light (e.g. red).

FIG. 18Bshows an arrangement of optical layers in a micro device structure, in accordance with an embodiment of the present invention. Here, the sub pixel with no optical layer31840creates more of higher wavelength (green) color, while the sub pixel with optical layer31820creates more lower wavelength (red) color.

According to one embodiment, an optoelectronic device is provided. The optoelectronic device comprises a plurality of semiconductor layers formed on a substrate to form a top surface and a bottom surface, wherein the plurality of semiconductor layers have isolated areas that form at least one side surface; one or more cover layers form a space around the isolated areas optically coupled to the at least one side surface; and functional tuning materials are disposed in the space formed by the one or more cover layers.

According to another embodiment, the one or more cover layers comprises one or more of: a passivation layer, a dielectric layer, an optical enhancement layer, an encapsulation layer, a reflective layer, and a color filter layer, and functional tuning materials comprises color conversion materials.

According to some embodiments, the functional tuning materials are further disposed on one of: the top surface or the bottom surface of the optoelectronic device.

According to further embodiments, the at least one contact is disposed on at least one of: the top surface or the bottom surface of the optoelectronic device and a pad is coupled to the optoelectronic device through the at least one contact.

According to another embodiment, the height of the at least one contact is extendable beyond the functional tuning materials disposed on a same side of the at least one contact and wherein the at least one contact on one of: the top surface or the bottom surface of the optoelectronic device is connected to a least another contact on another surface of the optoelectronic device through a trace. The trace is separated from the optoelectronic device by a dielectric layer.

According to some embodiments, the encapsulation layer protects the color conversion materials from oxygen and moisture, the optical enhancement layer reflects the light into the color conversion materials, the reflective layer enhances the light coupling into the color conversion materials, and the reflective layer is extended on one of: the top surface or the bottom surface of the optoelectronic device. The reflective layer comprises a reflective part and a transparent part.

According to other embodiments, the plurality of cover layers is deposited by one of: printing, evaporation, or sputtering and patterned by one of: photolithography, liftoff, or printing.

According to further embodiments, the one or more cover layers encircling the functional tuning materials between the at least one side surface and the one or more cover layers.

According to one embodiment, a display may be provided. The display may comprising: a substrate, at least one pixel structure disposed on or over the substrate, each pixel structure including at least one micro device mounted in proximity of a corner of the pixel structure, at least one color conversion layer mounted on the at least one micro device; and a top reflector mounted on the color conversion layer extended over the top of the area of the micro device.

According to another embodiment, the display may further comprise at least a wall surrounding a part or a whole of the pixel structure, a reflective layer covering the wall to reflect back the light towards the pixel structure. The top reflector is a conductive electrode for coupling the micro device to a signal source and the reflective layer is a touch sensor electrode.

According to yet another embodiment, the display may further comprise a bottom reflector disposed between the micro device and the substrate for reflecting the light back from the micro device. The bottom reflector is used as an electrode. The top reflector is patterned to open an area to let light be directed outwardly from the pixel area. The bottom reflector is patterned to open an area to let light be directed outwardly from the micro device. The wall comprises a dielectric layer, a polymer, a stack of metals or another reflector.

According to one embodiment, a plurality of optical layers may be coupled with the micro device. The optical layers are disposed in between color conversion layers.

In summary, the disclosure is related to creating different functional micro devices by integrating functional tuning materials and creating an encapsulation capsule to protect these materials. Various embodiments of the present disclosure also related to improve light extraction efficiencies of micro devices by mounting micro devices at a proximity of a corner of a pixel active area and arranging QD films with optical layers in a micro device structure.