Multicolor light-emitting stacks and related manufacturing method

Abstract

Methods of stacking multicolor light-emitting diodes (LEDs) and / or quantum dots, methods of fabricating multicolor light-emitting stacks, and related articles and systems are generally described.

Description

[0001] MULTICOLOR LIGHT-EMITTING STACKS AND RELATED MANUFACTURING METHOD

[0002] RELATED APPLICATIONS

[0003] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 63 / 654,714, filed May 31, 2024, and entitled “MULTICOLOR LIGHTEMITTING STACKS AND RELATED METHODS,” which is incorporated herein by reference in its entirety for all purposes.

[0004] TECHNICAL FIELD

[0005] Methods of stacking multicolor light-emitting diodes (LEDs) and / or quantum dots, methods of fabricating multicolor light-emitting stacks, and related articles and systems are generally described.

[0006] SUMMARY

[0007] Generally described herein are methods of stacking multicolor LEDs and / or quantum dots, methods of fabricating multicolor light-emitting stacks, and related articles and systems. The subject matter of the present disclosure involves, in some cases, interrelated products, alternative solutions to a particular problem, and / or a plurality of different uses of one or more systems and / or articles.

[0008] According to certain embodiments, a multicolor LED structure is described. In some embodiments, the multicolor LED structure comprises: a substrate; a quantum dot layer disposed over the substrate, wherein the quantum dot layer is configured to emit light at a first wavelength; a first LED layer disposed over the quantum dot layer such that the quantum dot layer is between the substrate and the first LED layer, wherein the first LED layer is configured to emit light at a second wavelength different from the first wavelength; and a second LED layer disposed over the first LED layer such that the first LED layer is between the quantum dot layer and the second LED layer, wherein the second LED layer is configured to emit light at a third wavelength different from the first wavelength and the second wavelength.

[0009] In some embodiments, a method of fabricating a multicolor LED structure is described. In certain embodiments, the method comprises: forming a quantum dot layer over a substrate, wherein the quantum dot layer is configured to emit light at a first wavelength; forming a first LED layer over a release layer comprising a two-dimensional (2D) material disposed over a growth substrate, wherein the first LED layer is configured to emit light at a second wavelength; removing the first LED layer from the release layer; disposing the first LED layer over the quantum dot layer; forming a second LED layer, wherein the second LED layer is configured to emit light at a third wavelength; and disposing the second LED layer over the first LED layer.

[0010] Other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments of the disclosure when considered in conjunction with the accompanying figures. In cases where the present specification and a document incorporated by reference include conflicting and / or inconsistent disclosure, the present specification shall control.

[0011] BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Non-limiting embodiments of the present disclosure will be described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale unless otherwise indicated. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the disclosure shown where illustration is not necessary to allow those of ordinary skill in the art to understand the disclosure. In the figures:

[0013] FIG. 1 shows a process flow schematic diagram representing a method of forming a LED layer over a release layer comprising a 2D material disposed over a growth substrate, in accordance with certain embodiments.

[0014] FIG. 2 shows a process flow schematic diagram representing a method of removing a LED layer from a release layer, in accordance with certain embodiments.

[0015] FIG. 3 shows a process flow schematic diagram representing a method of transferring a LED layer to a substrate, in accordance with certain embodiments.

[0016] FIG. 4 shows a process flow schematic diagram representing a method of transferring a LED layer to a quantum dot layer over a substrate, in accordance with certain embodiments.

[0017] FIG. 5 shows a process flow schematic diagram representing a method of transferring a LED layer to a polymer layer over a quantum dot layer over a substrate, in accordance with certain embodiments.

[0018] FIGS. 6A-6B show a process flow schematic diagram representing a method of stacking a plurality of LEDs and fabricating a multicolor LED stack, in accordance with certain embodiments.

[0019] FIG. 7A shows a schematic diagram representing a method of interconnecting LEDs after stacking the LEDs, in accordance with certain embodiments. FIG. 7B shows a process flow schematic diagram representing a method of interconnecting LEDs while stacking the LEDs, in accordance with certain embodiments.

[0020] FIGS. 8A-8B show cross-sectional schematic diagrams of a multicolor LED stack, in accordance with certain embodiments.

[0021] FIG. 8C shows a cross-sectional schematic diagram of a multicolor LED stack configured such that light is emitted out of the multicolor LED stack through the substrate, in accordance with certain embodiments.

[0022] FIG. 9A shows a cross-sectional schematic diagram of a multicolor LED stack comprising a reflector layer, in accordance with certain embodiments.

[0023] FIG. 9B shows a cross-sectional schematic diagram of a multicolor LED stack comprising a reflector layer, a first reflector material, and a second reflector material, in accordance with certain embodiments.

[0024] FIG. 10 shows a process flow schematic diagram representing a method of forming a LED layer over a release layer comprising a 2D material disposed over a growth substrate and removing the LED layer from the release layer, in accordance with certain embodiments.

[0025] FIG. 11 shows a process flow schematic diagram representing a method of fabricating a full color LED stack, in accordance with certain embodiments.

[0026] FIG. 12 shows a process flow schematic diagram representing a method of fabricating a full color LED stack with accompanying photographs representing color realization, in accordance with certain embodiments.

[0027] FIG. 13 shows a cross-sectional schematic diagram of a full color LED stack with driving circuits, in accordance with certain embodiments.

[0028] FIG. 14 shows schematic diagrams comparing conventional red, green, and blue (RGB) LEDs with a full color LED stack, in accordance with certain embodiments.

[0029] FIG. 15 shows a schematic diagram of a quantum dot (QD) / LED device, in accordance with certain embodiments.

[0030] FIG. 16 shows photographs of a QD / LED device, in accordance with certain embodiments.

[0031] DETAILED DESCRIPTION

[0032] Methods of stacking multicolor LEDs and / or quantum dots, methods of fabricating multicolor light-emitting stacks, and related articles and systems are generally described. In some embodiments, for example, a method of stacking multicolor LEDs is described. As used herein, the term “multicolor LEDs” refers to a plurality of LEDs (i.e., at least two LEDs), each LED configured to emit light at a distinct wavelength corresponding to light in the ultraviolet (UV) and / or visible electromagnetic spectrum. In certain embodiments, a method of fabricating multicolor LED stacks is described. For example, in some embodiments, a method of fabricating a full color LED stack is described. As used herein, the term “full color LED stack” refers to a stack comprising a plurality of LEDs (i.e., at least two LEDs), the stack being configured to emit light at a first wavelength corresponding to red light, a second wavelength corresponding to green light, and a third wavelength corresponding to blue light (e.g., a RGB LED stack). In some embodiments, a multicolor LED structure (e.g., in the form of a stack, such as a full color LED stack) is described. In certain embodiments, the multicolor LED structure is part of a multicolor LED display (e.g., a full color LED display), such as a multicolor LED transparent display (e.g., a full color LED transparent display).

[0033] The term “visible spectrum” is used herein to describe electromagnetic radiation having a wavelength of from 380 nm to 750 nm. As used herein, “red light” refers to electromagnetic radiation having a wavelength of from 620 nm to 750 nm. “Blue light,” as used herein, refers to electromagnetic radiation having a wavelength of from 450 nm to less than 495 nm. As used herein, “green light” refers to electromagnetic radiation having a wavelength of from 495 nm to 570 nm.

[0034] “UV light” (or, equivalently, “ultraviolet light”), as used herein, refers to electromagnetic radiation having a wavelength of from 100 nm to below 380 nm.

[0035] According to certain embodiments, the multicolor LED stack comprises one or more quantum dot layers that are configured to emit light at a wavelength corresponding to light in the UV and / or visible electromagnetic spectrum. In certain embodiments, for example, the multicolor LED stack comprises a quantum dot layer that is configured to emit light at a wavelength corresponding to red light. In certain embodiments, the multicolor LED stack comprises a quantum dot layer disposed over a substrate, and one or more LED layers disposed over the quantum dot layer. In some embodiments, a full color LED stack comprises: (i) a quantum dot layer configured to emit light at a wavelength corresponding to red light; (ii) a first LED layer disposed over the quantum dot layer and configured to emit light at a wavelength corresponding to ultraviolet (UV) light and / or blue light; and (iii) a second LED layer disposed over the first LED layer and configured to emit light at a wavelength corresponding to green light. According to some embodiments, the full color LED stack is advantageously capable of producing virtually any color of visible light using the three primary additive colors of visible light (e.g., red light, green light, and blue light). The multicolor LED stacks described herein advantageously address drawbacks in conventional LED displays. For example, in certain embodiments, the multicolor LED stack employs vertical stacking of multicolor LEDs (and / or quantum dots) for advanced display and lighting applications, which increases the pixel density (e.g., pixel per inch) and / or color accuracy as compared to conventional (e.g., non-stacked) displays. In accordance with certain embodiments, the quantum dot layer is advantageously thin and has an advantageously small facial surface area such that the overall size (e.g., thickness and facial surface area) of the multicolor LED stack is reduced as compared to conventional non-stacked displays. In some embodiments, incorporating a quantum dot layer in the multicolor LED stack increases the overall quantum efficiency of the multicolor LED stack as compared to, for example, a multicolor LED stack that is otherwise equivalent but does not include the quantum dot layer.

[0036] In accordance with certain embodiments, the multicolor LED stack provides a vertically integrated architecture with multiple stacked layers that reduce the overall size of the device as compared to, for example, conventional non-stacked multicolor devices having a planar arrangement with layers positioned in an array. For example, such conventional devices incorporate side-by-side placement of red, green, and blue subpixels in each pixel for full color realization. In contrast, the total facial surface area of the multicolor LED stack described herein is advantageously minimized without increasing the lateral dimensions orthogonal to a thickness of the stack (e.g., length and width). Accordingly, the compact design is particularly advantageous in applications where pixel density, form factor, and / or substrate functionalization area are limited (e.g., microdisplays, wearable devices, augmented reality systems, microsensors, etc.).

[0037] According to certain embodiments, a method of stacking multicolor LEDs (e.g., to fabricate a multicolor LED stack) is described herein in reference to FIGS. 1-7B. Various methods of forming and stacking LEDs are described in U.S. Patent Application Serial No. 16 / 156,250, filed October 10, 2018, patented as U.S. Patent No. 10,517,155 on December 24, 2019, and entitled “Methods and Apparatus for Vertically Stacked Multicolor Light-Emitting Diode (LED) Display”, which is incorporated herein by reference in its entirety for all purposes.

[0038] In some embodiments, a method comprises forming a first LED layer over a release layer comprising a 2D material disposed over a growth substrate. FIG. 1 shows a process flow schematic diagram representing a method of forming a LED layer over a release layer comprising a 2D material disposed over a growth substrate, in accordance with certain embodiments. In some embodiments, referring to FIG. 1, a growth substrate is provided. The growth substrate may comprise any of a variety of suitable materials. In some embodiments, for example, the growth substrate comprises silicon (Si), silicon dioxide (SiC ), silicon carbide (SiC), sapphire (AI2O3), gallium arsenide (GaAs), gallium nitride (GaN), indium gallium nitride (InGaN), zinc oxide (ZnO), zinc selenide (ZnSe), and / or combinations thereof. Other growth substrate materials are also possible.

[0039] Referring to FIG. 1, a 2D material is formed over the growth substrate, in accordance with certain embodiments. In some embodiments, the 2D material is grown (e.g., epitaxially grown) over the growth substrate. In other embodiments, the 2D material is grown (e.g., epitaxially grown) on a separate substrate and subsequently transferred to the growth substrate. The 2D material may comprise any of a variety of suitable materials. In some embodiments, for example, the 2D material comprises hexagonal boron nitride (hBN), graphene, amorphous graphene, molybdenum diselenide (MoSe2), molybdenum disulfide (M0S2), tungsten diselenide (WSe2), tungsten disulfide (WS2), tin selenide (SnSe), tin diselenide (SnSe2), tin disulfide (SnSe2), indium selenide (InSe), a 2D perovskite, a 2D inorganic compound comprising one or more atomically thin layers of transition metal carbides, nitrides, and / or carbonitrides (e.g., a MXene), and / or combinations thereof. Other 2D materials are also possible.

[0040] In some embodiments, the 2D material disposed over the growth substrate is a release layer (e.g., for releasing a semiconductor material, such as a LED layer, as described herein in greater detail). Referring to FIG. 1, a LED layer (e.g., a first LED layer) is formed over the release layer comprising the 2D material disposed over the growth substrate, in accordance with some embodiments. In certain embodiments, forming the first LED layer comprises epitaxially growing the first LED layer over the release layer. In some embodiments, the first LED layer is formed over the release layer by remote epitaxy, molecular-beam epitaxy (MBE), chemical vapor deposition (CVD), metal-organic chemical vapor deposition (MOCVD), and / or pulsed laser deposition (PLD). Other methods of forming the first LED layer are also possible. Suitable semiconductor materials for the LED layer are described herein in greater detail.

[0041] FIG. 2 shows a process flow schematic diagram representing a method of removing (e.g., exfoliating) a LED layer from a release layer, in accordance with certain embodiments. In some embodiments, as shown in FIG. 2, the first LED layer disposed over the release layer comprising the 2D material disposed over the growth substrate is provided (e.g., as described herein in greater detail with respect to FIG. 1).

[0042] According to some embodiments, referring to FIG. 2, a stressor is disposed (e.g., deposited) over the first LED layer. The stressor may comprise any of a variety of suitable materials. For example, in some embodiments, the stressor comprises a metal. Suitable metals include, but are not limited to, nickel (Ni), aluminum (Al), and / or combinations thereof. As shown in FIG. 2, a tape layer is disposed (e.g., deposited) over the stressor, in accordance with certain embodiments. The tape layer may comprise any of a variety of suitable materials. In some embodiments, for example, the tape layer comprises thermal release tape (TRT), polydimethylsiloxane (PDMS), and / or UV tape. Other tape materials are also possible.

[0043] In some embodiments, referring to FIG. 2, the tape layer disposed over the stressor disposed over the first LED layer is used to remove (e.g., exfoliate) the first LED layer from the release layer (e.g., with mechanical strength). In certain embodiments, the LED layer is removed from the release layer due to relatively weak bonding between the 2D material and the LED layer.

[0044] In some embodiments, although not shown in FIG. 2, a LED layer is removed from a release layer without using a stressor. In some such embodiments, a tape layer is disposed over the LED layer and used to remove (e.g., exfoliate) the LED layer from the release layer.

[0045] The epitaxial growth of a LED layer over a release layer and the removal (e.g., release) of the LED layer from the release layer as described herein with respect to FIGS. 1-2 may provide an LED layer having an advantageously low threading dislocation density (e.g., less than or equal to 1 x 107cm'2). LED layers having a low threading dislocation density may have more uniform optical properties as compared to LED layers having a higher threading dislocation density, in accordance with certain embodiments.

[0046] FIG. 10 shows a process flow schematic diagram representing a method of forming a LED layer over a release layer comprising a 2D material disposed over a growth substrate and removing the LED layer from the release layer, in accordance with certain embodiments. In some embodiments, the 2D material comprises a monolayer of 2D material. In other embodiments, the 2D material comprises at least two layers of a 2D material. For example, in some embodiments, the 2D material comprises a bilayer of 2D material (e.g., as shown in FIG. 10), a trilayer of 2D material, etc.

[0047] Referring to FIG. 10, an electrode (such as a transparent conductive electrode (TCE)) may be disposed over a LED layer formed over the release layer comprising the 2D material disposed over the growth substrate, in accordance with certain embodiments. The electrode (e.g., TCE) may comprise any of a variety of suitable materials. In some embodiments, for example, the electrode (e.g., TCE) comprises a metal (e.g., nickel and / or gold), indium tin oxide (ITO), zinc oxide (ZnO), AhOa-dopcd ZnO (ATO), or the like. Combinations of materials are also possible.

[0048] In some embodiments, as shown in FIG. 10, the stressor is disposed over the electrode (e.g., TCE), and the tape layer (e.g., TRT) is disposed over the stressor. In certain embodiments, the tape layer disposed over the stressor disposed over the electrode disposed over the first LED layer is used to remove (e.g., exfoliate) the electrode and the first LED layer from the release layer (e.g., with mechanical strength due to relatively weak bonding between the 2D material and the first LED layer). In other embodiments, although not shown in FIG. 10, an electrode and a first LED layer are removed from a release layer without using a stressor. In some embodiments, for example, a tape layer is disposed over the electrode and the LED layer and used to remove (e.g., exfoliate) the electrode and the LED layer from the release layer.

[0049] FIG. 3 shows a process flow schematic diagram representing a method of transferring a LED layer to a substrate, in accordance with certain embodiments. As shown in FIG. 3, a substrate is provided, in accordance with some embodiments. In certain embodiments, the substrate is a backplane of a LED stack. In some embodiments, the substrate comprises electronics (e.g., one or more transistors and / or circuits). Suitable substrate materials are described herein in greater detail.

[0050] According to certain embodiments, referring to FIG. 3, a polymer layer is disposed (e.g., deposited) over the substrate. In some embodiments, the polymer layer is spin coated over the substrate. In certain embodiments, the polymer layer disposed over the substrate is annealed (e.g., to evaporate one or more solvents and / or enhance adhesion between the polymer layer and the substrate). The polymer layer may comprise any of a variety of suitable materials. For example, in certain embodiments, the polymer layer comprises a polyimide (PI) (e.g., as shown in FIG. 3). In some embodiments, the polymer comprises an epoxy, a SU-8 series polymer, ethylene-vinyl acetate (EVA), polyvinyl chloride (PVC), a thermoplastic elastomer (TPE), and / or a polyester. Other polymers are also possible. Combinations of polymers are also possible.

[0051] In some embodiments, although not shown in FIG. 3, a reflector layer is disposed between the polymer layer and the substrate. The reflector layer is described herein in greater detail.

[0052] According to some embodiments, as shown in FIG. 3, the tape layer disposed over the stressor disposed over the first LED layer used to remove (e.g., exfoliate) the first LED layer from the release layer (e.g., as described herein in greater detail with respect to FIG. 2) is transferred to the polymer layer disposed over the substrate.

[0053] Referring to FIG. 3, the tape layer is released from the stressor, in accordance with certain embodiments. In some embodiments, the tape layer (e.g., TRT), the stressor, the first LED layer, the polymer layer, and the substrate are annealed to release the tape layer (e.g., TRT). In certain embodiments, annealing the first LED layer, the polymer layer, and the substrate enhances adhesion between the first LED layer, the polymer layer, and / or the substrate.

[0054] As shown in FIG. 3, the stressor is removed from the first LED layer, in accordance with some embodiments. In certain embodiments, the stressor is removed from the first LED layer by etching (e.g., chemical etching). In certain embodiments, referring to FIG. 3, removing the stressor provides a first LED layer disposed over a polymer layer disposed over a substrate.

[0055] FIG. 4 shows a process flow schematic diagram representing a method of transferring a LED layer to a quantum dot layer over a substrate, in accordance with certain embodiments. In some embodiments, as described herein in greater detail, the LED stack comprises one or more quantum dot layers. According to certain embodiments, as shown in FIG. 4, a method of stacking multicolor LEDs (e.g., to fabricate a multicolor LED stack) comprises providing a substrate (e.g., a backplane of a LED stack) and forming a quantum dot layer over the substrate. In some embodiments, the quantum dot layer is formed over the substrate by spin coating. In some embodiments, as shown in FIG. 4, the quantum dot (QD) layer is configured to emit light at a wavelength corresponding to red light (e.g., a red quantum dot layer).

[0056] In some embodiments, although not shown in FIG. 4, a reflector layer is disposed between the quantum dot layer and the substrate. The reflector layer is described herein in greater detail.

[0057] In some embodiments, a method of stacking multicolor LEDs (e.g., to fabricate a multicolor LED stack) comprises disposing the first LED layer over the quantum dot layer. As shown in FIG. 4, the tape layer disposed over the stressor disposed over the first LED layer used to remove (e.g., exfoliate) the first LED layer from the release layer (e.g., as described herein in greater detail with respect to FIG. 2) is transferred to the quantum dot layer disposed over the substrate, in accordance with certain embodiments.

[0058] Referring to FIG. 4, the tape layer is released from the stressor, in accordance with certain embodiments. In some embodiments, the tape layer (e.g., TRT), the stressor, the first LED layer, the quantum dot layer, and the substrate are annealed to release the tape layer (e.g., TRT). In certain embodiments, annealing the first LED layer, the quantum dot layer, and the substrate enhances adhesion between the first LED layer, the quantum dot layer, and / or the substrate.

[0059] As shown in FIG. 4, the stressor is removed from the first LED layer, in accordance with some embodiments. In some embodiments, the stressor is removed from the first LED layer by etching (e.g., chemical etching). In certain embodiments, referring to FIG. 4, removing the stressor provides a first LED layer disposed over a quantum dot layer disposed over a substrate. FIG. 5 shows a process flow schematic diagram representing a method of transferring a LED layer to a polymer layer over a quantum dot layer over a substrate, in accordance with certain embodiments. According to some embodiments, as shown in FIG. 5, a substrate (e.g., a backplane of a LED stack) is provided, a quantum dot layer (e.g., a red quantum dot layer) is formed over the substrate, and a polymer (e.g., polyimide) layer is formed over the quantum dot layer.

[0060] In some embodiments, although not shown in FIG. 5, a reflector layer is disposed between the quantum dot layer and the substrate, and / or a reflector layer is disposed between the polymer layer and the quantum dot layer. The reflector layer is described herein in greater detail.

[0061] According to some embodiments, as shown in FIG. 5, the tape layer disposed over the stressor disposed over the first LED layer used to remove (e.g., exfoliate) the first LED layer from the release layer (e.g., as described herein in greater detail with respect to FIG. 2) is transferred to the polymer layer disposed over the quantum dot layer disposed over the substrate.

[0062] Referring to FIG. 5, the tape layer is released from the stressor, in accordance with certain embodiments. In some embodiments, the tape layer (e.g., TRT), the stressor, the first LED layer, the polymer layer, the quantum dot layer, and the substrate are annealed to release the tape layer (e.g., TRT). In certain embodiments, annealing the first LED layer, the polymer layer, the quantum dot layer, and the substrate enhances adhesion between the first LED layer, the polymer layer, the quantum dot layer, and / or the substrate.

[0063] As shown in FIG. 5, the stressor is removed from the first LED layer, in accordance with some embodiments. In some embodiments, the stressor is removed from the first LED layer by etching (e.g., chemical etching). In certain embodiments, referring to FIG. 5, removing the stressor provides a first LED layer disposed over a polymer layer disposed over a quantum dot layer disposed over a substrate.

[0064] FIGS. 6A-6B show a process flow schematic diagram representing a method of stacking a plurality of LEDs and fabricating a multicolor LED stack, in accordance with certain embodiments. As shown in FIG. 6A, a first LED layer disposed over a polymer layer disposed over a substrate is provided (e.g., as described herein in greater detail with respect to FIG. 3). According to some embodiments, although not shown in FIG. 6A, a first LED layer disposed over a quantum dot layer disposed over a substrate is provided (e.g., as described herein in greater detail with respect to FIG. 4), or a first LED layer disposed over a polymer layer disposed over quantum dot layer disposed over a substrate is provided (e.g., as described herein in greater detail with respect to FIG. 5). Referring to FIG. 6A, the first LED layer is modified such that the first LED layer comprises a first LED device layer comprising one or more electrodes and / or circuitry that facilitate interconnection of the first LED layer to one or more circuits, in accordance with certain embodiments. In some embodiments, the first LED layer is modified by etching (e.g., chemical etching). In certain embodiments, as shown in FIG. 6A, a polymer is disposed (e.g., deposited) over the first LED layer. For example, in some embodiments, the first LED layer is etched and spin coated with a polymer (e.g., polyimide, as shown in FIG. 6A). The polymer may, in some embodiments, comprise one or more UV light absorbing materials, visible light absorbing materials, and / or transparent materials. The polymer may comprise any of the materials described herein with respect to the polymer layer of FIG. 3, in accordance with certain embodiments.

[0065] In some embodiments, the method comprises forming a second LED layer. In some embodiments, forming the second LED layer comprises repeating the process flow diagram described herein in greater detail with respect to FIG. 1. According to some embodiments, the second LED layer is formed over the release layer comprising the 2D material disposed over the growth substrate (i.e., the same release layer comprising the 2D material disposed over the growth substrate used to form the first LED layer). In other embodiments, the release layer used to form the first LED layer is a first release layer comprising a first 2D material disposed over a first growth substrate, and the second LED layer is formed over a second release layer comprising a second 2D material disposed over a second growth substrate.

[0066] In certain embodiments, forming the second LED layer comprises epitaxially growing the second LED layer. In some embodiments, the second LED layer is formed over the release layer by remote epitaxy, MBE, CVD, MOCVD, and / or PLD.

[0067] According to some embodiments, a method comprises removing the second LED layer from the release layer. In some embodiments, removing the second LED layer from the release layer comprises repeating the process flow diagram described herein in greater detail with respect to FIG. 2 (or with respect to FIG. 10).

[0068] In some embodiments, the method comprises disposing the second LED layer over the first LED layer. Referring, for example, to FIG. 6A, the tape layer disposed over the stressor disposed over the second LED layer used to remove (e.g., exfoliate) the second LED layer from the release layer is transferred to first LED layer. In some embodiments, the tape layer is released from the stressor (e.g., by annealing the tape layer, the stressor, the second LED layer, the first LED layer, the polymer layer, and the substrate). In some embodiments, the second LED layer, the first LED layer, the polymer layer, and the substrate are annealed to enhance adhesion between the second LED layer, the first LED layer, the polymer layer, and / or the substrate. In certain embodiments, the stressor is removed from the second LED layer (e.g., by etching).

[0069] In some embodiments, although not shown in FIG. 6A, the second LED layer is disposed over the first LED layer disposed over a quantum dot layer disposed over the substrate, or the second LED layer is disposed over the first LED layer disposed over a polymer layer disposed over a quantum dot layer disposed over the substrate.

[0070] In some embodiments, the method comprises forming a third LED layer. In some embodiments, forming the third LED layer comprises repeating the process flow diagram described herein in greater detail with respect to FIG. 1. According to some embodiments, the third LED layer is formed over the release layer comprising the 2D material disposed over the growth substrate (i.e., the same release layer comprising the 2D material disposed over the growth substrate used to form the first LED layer and / or the second LED layer). In other embodiments, the release layer used to form the first LED layer is a first release layer comprising a first 2D material disposed over a first growth substrate, the release layer used to form the second LED layer is a second release layer comprising a second 2D material disposed over a second growth substrate, and the third LED layer is formed over a third release layer comprising a third 2D material disposed over a third growth substrate.

[0071] In certain embodiments, forming the third LED layer comprises epitaxially growing the third LED layer. In some embodiments, the third LED layer is formed over the release layer by remote epitaxy, MBE, CVD, MOCVD, and / or PLD.

[0072] According to some embodiments, a method comprises removing the third LED layer from the release layer. In some embodiments, removing the third LED layer from the release layer comprises repeating the process flow diagram described herein in greater detail with respect to FIG. 2 (or with respect to FIG. 10).

[0073] In some embodiments, the method comprises disposing the third LED layer over the second LED layer. In some embodiments, the tape layer disposed over the stressor disposed over the third LED layer used to remove (e.g., exfoliate) the third LED layer from the release layer is transferred to the second LED layer. In some embodiments, the tape layer is released from the stressor (e.g., by annealing the tape layer, the stressor, the third LED layer, the second LED layer, the first LED layer, the polymer layer, and the substrate). In some embodiments, the third LED layer, the second LED layer, the first LED layer, the polymer layer, and the substrate are annealed to enhance adhesion between the third LED layer, the second LED layer, the first LED layer, the polymer layer, and / or the substrate. In certain embodiments, the stressor is removed from the third LED layer (e.g. by etching).

[0074] In some embodiments, although not shown in FIG. 6A, the third LED layer is disposed over the second LED layer disposed over the first LED layer disposed over a quantum dot layer disposed over the substrate, or the third LED layer is disposed over the second LED layer disposed over the first LED layer disposed over a polymer layer disposed over a quantum dot layer disposed over the substrate.

[0075] According to some embodiments, referring to FIG. 6B, the second LED layer is modified such that the second LED layer comprises a second LED device layer comprising one or more electrodes and / or circuitry that facilitate interconnection of the second LED layer to one or more circuits, and / or the third LED layer is modified such that the third LED layer comprises a third LED device layer comprising one or more electrodes and / or circuitry that facilitate interconnection of the third LED layer to one or more circuits. In some embodiments, the second LED layer and / or the third LED layer are modified by etching (e.g., chemical etching). In certain embodiments, as shown in FIG. 6B, a polymer is disposed (e.g., deposited) over the second LED layer and the third LED layer. For example, in some embodiments, the second LED layer and / or the third LED layer are etched and spin coated with a polymer (e.g., polyimide, as shown in FIG. 6B). The polymer may, in some embodiments, comprise one or more UV light absorbing materials, visible light absorbing materials, and / or transparent materials. In accordance with certain embodiments, the polymer comprises any of the materials described herein with respect to the polymer layer of FIG. 3.

[0076] According to some embodiments, the second LED layer is modified such that the second LED layer comprises a second LED device layer before disposing the third LED layer over the second LED layer.

[0077] In some embodiments, referring to FIG. 6B, the first LED layer, the second LED layer, and the third LED layer are interconnected to the substrate (e.g., to one or more circuits on the substrate). FIG. 7A shows a schematic diagram representing a method of interconnecting LEDs to a substrate after stacking the LEDs (e.g., after stacking the first LED layer, the second LED layer, and the third LED layer), in accordance with certain embodiments. FIG. 7B shows a process flow schematic diagram representing a method of interconnecting LEDs to a substrate while stacking the LEDs (e.g. while stacking the first LED layer, the second LED layer, and the third LED layer), in accordance with certain embodiments.

[0078] In some embodiments, as shown in FIG. 6B, a first reflector material and a second reflector material are disposed over the substrate such that the first reflector material and the second reflector material extend perpendicular, within 10° (or within 8°, within 6°, within 4°, within 2°, or within 1°), to a face of the substrate over which the first LED layer, the second LED layer, and the third LED layer are located.

[0079] FIG. 11 shows a process flow schematic diagram representing a method of fabricating a full color LED stack, in accordance with certain embodiments. FIG. 12 shows a process flow schematic diagram representing a method of fabricating a full color LED stack with accompanying photographs representing color realization, in accordance with certain embodiments.

[0080] According to certain embodiments, a multicolor LED stack (e.g. a full color LED stack) is described. FIGS. 8A-8B show cross-sectional schematic diagrams of multicolor LED stack 102, in accordance with certain embodiments. In certain embodiments, the multicolor LED stack is part of a multicolor LED display (e.g., a full color LED display), such as a multicolor LED transparent display (e.g., a full color LED transparent display).

[0081] In some embodiments, the multicolor LED stack comprises a quantum dot layer. For example, referring to FIGS. 8A-8B, multicolor LED stack 102 comprises quantum dot layer 104. In certain embodiments, quantum dot layer 104 is disposed over substrate 106.

[0082] According to some embodiments, the quantum dot layer comprises a semiconductor. For example, in certain embodiments, the quantum dot layer comprises a Ill-nitride material (e.g., GaN, InGaN, GaAs, InGaAs, etc.). In certain embodiments, the quantum dot layer comprises cadmium selenide (CdSe), indium phosphide (InP), cadmium telluride (CdTe), copper indium disulfide (CuInS2), lead selenide (PbSe), lead sulfide (PbS), silicon, carbon, and / or a perovskite. Other materials for the quantum dot layer are also possible. Combinations of materials for the quantum dot layer are also possible. In some embodiments, the quantum dot layer comprises InGaAs.

[0083] In some embodiments, the quantum dot layer is configured to emit light at a first wavelength. For example, in some embodiments, the first wavelength is a wavelength corresponding to red light. In certain embodiments, the first wavelength is greater than or equal to 620 nm, greater than or equal to 625 nm, greater than or equal to 650 nm, greater than or equal to 675 nm, greater than or equal to 700 nm, or greater than or equal to 725 nm. In some embodiments, the first wavelength is less than or equal to 750 nm, less than or equal to 725 nm, less than or equal to 700 nm, less than or equal to 675 nm, less than or equal to 650 nm, less than or equal to 630 nm, or less than or equal to 625 nm. Combinations of the above recited ranges are possible (e.g., the first wavelength is greater than or equal to 620 nm and less than or equal to 750 nm). Other ranges are also possible. According to certain embodiments, the quantum dot layer is configured to emit light at the first wavelength when activated by light emitted by one or more LED layers. In some embodiments, for example, as described herein in greater detail, quantum dot layer 104 is configured to emit light at the first wavelength when activated by light at a second wavelength emitted by first LED layer 108, wherein the second wavelength is different from the first wavelength.

[0084] According to some embodiments, the light at the first wavelength emitted by the quantum dot layer is reflected by a reflector layer and / or one or more reflector materials such that the light at the first wavelength is emitted out of the multicolor LED stack through a surface of the multicolor LED stack that is opposite the substrate. In certain embodiments, for example, as described herein in greater detail, the light at the first wavelength emitted by quantum dot layer 104 is reflected by reflector layer 116, first reflector material 118a, and / or second reflector material 118b such that the light at the first wavelength is emitted out of multicolor LED stack 102 though surface 120 of multicolor LED stack 102 that is opposite substrate 106.

[0085] The quantum dot layer may have any of a variety of suitable thicknesses. For example, referring to FIG. 8B, quantum dot layer 104 has thickness 802a. In some embodiments, for example, the quantum dot layer has a thickness greater than or equal to 1 micrometer, greater than or equal to 2 micrometers, greater than or equal to 3 micrometers, greater than or equal to 4 micrometers, greater than or equal to 5 micrometers, greater than or equal to 6 micrometers, greater than or equal to 7 micrometers, greater than or equal to 8 micrometers, or greater than or equal to 9 micrometers. In certain embodiments, the quantum dot layer has a thickness less than or equal to 10 micrometers, less than or equal to 9 micrometers, less than or equal to 8 micrometers, less than or equal to 7 micrometers, less than or equal to 6 micrometers, less than or equal to 5 micrometers, less than or equal to 4 micrometers, less than or equal to 3 micrometers, or less than or equal to 2 micrometers. Combinations of the above recited ranges are possible (e.g., the quantum dot layer has a thickness greater than or equal to 1 micrometer and less than or equal to 10 micrometers). Other ranges are also possible. In certain embodiments, the quantum dot layer is advantageously thin. In certain embodiments, the quantum dot layer is a micro-quantum dot layer.

[0086] According to certain embodiments, the quantum dot layer has a facial surface area defined by two lateral dimensions that are orthogonal to the thickness of the quantum dot layer and perpendicular to each other (e.g., length and width). The quantum dot layer may have any of a variety of suitable facial surface areas. In some embodiments, for example, the facial surface area of the quantum dot layer is greater than or equal to 1 micrometers2, greater than or equal to 10 micrometers2, greater than or equal to 100 micrometers2, greater than or equal to 1000 micrometers2, greater than or equal to 0.01 millimeters2, greater than or equal to 0.1 millimeters2, greater than or equal to 1 millimeter2, greater than or equal to 10 millimeters2, or greater than or equal to 1 centimeter2. In certain embodiments, the facial surface area of the quantum dot layer is less than or equal to 10 centimeters2, less than or equal to 1 centimeter2, less than or equal to 10 millimeters2, less than or equal to 1 millimeter2, less than or equal to 0.1 millimeters2, less than or equal to 0.01 millimeters2, less than or equal to 1000 micrometers2, less than or equal to 100 micrometers2, or less than or equal to 10 micrometers2. Combinations of the above recited ranges are possible (e.g., the facial surface area of the quantum dot layer is greater than or equal to 1 micrometer2and less than or equal to 10 centimeters2). Other ranges are also possible.

[0087] According to certain embodiments, the multicolor LED stack comprises a first LED layer. For example, referring to FIGS. 8A-8B, multicolor LED stack 102 comprises first LED layer 108. In some embodiments, first LED layer 108 is disposed over quantum dot layer 104 such that quantum dot layer 104 is between substrate 106 and first LED layer 108.

[0088] According to some embodiments, the first LED layer comprises a semiconductor. For example, in certain embodiments, the first LED layer comprises a Ill-nitride material (e.g., GaN, InGaN, GaAs, InGaAs, AlGaN, AIN, etc.). Other materials for the first LED layer are also possible. In some embodiments, the first LED layer comprises GaN and / or InGaN.

[0089] In some embodiments, the first LED layer is configured to emit light at a second wavelength. In certain embodiments, the second wavelength is different from the first wavelength. For example, in certain embodiments, the second wavelength is a wavelength corresponding to UV light (e.g., greater than or equal to 100 nm and less than 380 nm) and / or blue light (e.g., greater than or equal to 450 nm and less than 495 nm). In some embodiments, the second wavelength is greater than or equal to 100 nm, greater than or equal to 150 nm, greater than or equal to 200 nm, greater than or equal to 250 nm, greater than or equal to 300 nm, greater than or equal to 350 nm, greater than or equal to 400 nm, greater than or equal to 450 nm, or greater than or equal to 485 nm. In some embodiments, the second wavelength is less than 495 nm, less than or equal to 485 nm, less than or equal to 450 nm, less than or equal to 400 nm, less than or equal to 350 nm, less than or equal to 300 nm, less than or equal to 250 nm, less than or equal to 200 nm, or less than or equal to 150 nm. Combinations of the above recited ranges are possible (e.g., the second wavelength is greater than or equal to 100 nm and less than 495 nm). Other ranges are also possible. According to some embodiments, the second wavelength is a wavelength corresponding to UV light. In certain embodiments, for example, the second wavelength is greater than or equal to 100 nm, greater than or equal to 150 nm, greater than or equal to 200 nm, greater than or equal to 250 nm, greater than or equal to 300 nm, or greater than or equal to 350 nm. In certain embodiments, the second wavelength is less than or equal to 380 nm, less than or equal to 350 nm, less than or equal to 300 nm, less than or equal to 250 nm, less than or equal to 200 nm, or less than or equal to 150 nm. Combinations of the above recited ranges are possible (e.g., the second wavelength is greater than or equal to 100 nm and less than or equal to 380 nm). Other ranges are also possible.

[0090] In certain embodiments, the second wavelength is a wavelength corresponding to blue light. In some embodiments, for example, the second wavelength is greater than or equal to 450 nm, greater than or equal to 460 nm, greater than or equal to 470 nm, greater than or equal to 480 nm, or greater than or equal to 490 nm. In certain embodiments, the second wavelength is less than or equal to 495 nm, less than or equal to 490 nm, less than or equal to 480 nm, less than or equal to 470 nm, or less than or equal to 460 nm. Combinations of the above recited ranges are possible (e.g., the second wavelength is greater than or equal to 450 nm and less than or equal to 495 nm). Other ranges are also possible.

[0091] According to certain embodiments, the light at the second wavelength emitted by the first LED layer is configured to activate the quantum dot layer. In some embodiments, for example, as described herein in greater detail, the light at the second wavelength emitted by first LED layer 108 is configured to activate quantum dot layer 104 such that quantum dot layer 104 emits light at the first wavelength, wherein the second wavelength is different from the first wavelength.

[0092] In some embodiments, the first LED layer comprises an UV light absorbing material and / or one or more distributed Bragg reflectors (DBRs). In certain embodiments, as described herein in greater detail, the UV light absorbing material is polymer 114a and / or the one or more DBRs are disposed in polymer 114a. According to certain embodiments, the second wavelength is a wavelength corresponding to UV light, and the UV light absorbing material and / or the one or more DBRs prevent the light at the second wavelength from activating other LED layers (e.g., the second LED layer and / or the third LED layer).

[0093] The first LED layer may have any of a variety of suitable thicknesses. For example, referring to FIG. 8B, first LED layer 108 has thickness 802b. In some embodiments, for example, the first LED layer has a thickness greater than or equal to 0.5 micrometers. In some embodiments, the first LED layer has a thickness greater than or equal to 0.5 micrometers, greater than or equal to 1 micrometer, greater than or equal to 2 micrometers, greater than or equal to 5 micrometers, greater than or equal to 10 micrometers, greater than or equal to 50 micrometers, greater than or equal to 100 micrometers, greater than or equal to 500 micrometers, greater than or equal to 1 millimeter, greater than or equal to 2 millimeters, greater than or equal to 5 millimeters, greater than or equal to 1 centimeter, or greater. In certain embodiments, the first LED layer has a thickness less than or equal to 10 centimeters, less than or equal to 1 centimeter, less than or equal to 5 millimeters, less than or equal to 2 millimeters, less than or equal to 1 millimeter, less than or equal to 500 micrometers, less than or equal to 100 micrometers, less than or equal to 50 micrometers, less than or equal to 10 micrometers, less than or equal to 5 micrometers, less than or equal to 2 micrometers, or less than or equal to 1 micrometer. Combinations of the above recited ranges are possible (e.g., the first LED layer has a thickness greater than or equal to 0.5 micrometers and less than or equal to 10 centimeters). Other ranges are also possible. In certain embodiments, the first LED layer is advantageously thin. In certain embodiments, the first LED layer is a micro-LED layer.

[0094] In certain embodiments, the multicolor LED stack comprises a second LED layer. For example, referring to FIGS. 8A-8B, multicolor LED stack 102 comprises second LED layer 110. In some embodiments, second LED layer 110 is disposed over first LED layer 108 such that first LED layer 108 is between quantum dot layer 104 and second LED layer 110.

[0095] According to some embodiments, the second LED layer comprises a semiconductor. The second LED layer can comprise, in some embodiments, a III-V material. For example, in certain embodiments, the second LED layer comprises a Ill-nitride material (e.g., GaN, InGaN, GaAs, InGaAs, etc.). In some embodiments, the second LED layer comprises a III-phosphide material (e.g., GaP, GalnP, etc.). Other materials for the second LED layer are also possible. In some embodiments, the second LED layer comprises InGaN.

[0096] According to some embodiments, the second LED layer is configured to emit light at a third wavelength. In some embodiments, the third wavelength is different from the first wavelength and the second wavelength. For example, in certain embodiments, the third wavelength is a wavelength corresponding to green light. In some embodiments, the third wavelength is greater than or equal to 495 nm, greater than or equal to 500 nm, greater than or equal to 510 nm, greater than or equal to 520 nm, greater than or equal to 530 nm, greater than or equal to 540 nm, greater than or equal to 550 nm, greater than or equal to 560 nm, or greater than or equal to 565 nm. In some embodiments, the third wavelength is less than or equal to 570 nm, less than or equal to 565 nm, less than or equal to 560 nm, less than or equal to 550 nm, less than or equal to 540 nm, less than or equal to 530 nm, less than or equal to 520 nm, less than or equal to 510 nm, or less than or equal to 500 nm. Combinations of the above recited ranges are possible (e.g., the third wavelength is greater than or equal to 495 nm and less than or equal to 570 nm). Other ranges are also possible.

[0097] According to some embodiments, the light at the third wavelength emitted by the second LED layer is reflected by a reflector layer and / or one or more reflector materials such that the light at the third wavelength is emitted out of the multicolor LED stack through a surface of the multicolor LED stack that is opposite the substrate. In certain embodiments, for example, as described herein in greater detail, the light at the third wavelength emitted by second LED layer 110 is reflected by reflector layer 116, first reflector material 118a, and / or second reflector material 118b such that the light at the third wavelength is emitted out of multicolor LED stack 102 through surface 120 of multicolor LED stack 102 that is opposite substrate 106.

[0098] According to certain embodiments, the second LED layer comprises a visible light absorbing material and / or one or more DBRs. In some embodiments, as described herein in greater detail, the visible light absorbing material is polymer 114b and / or the one or more DBRs are disposed in polymer 114b. According to some embodiments, the visible light absorbing material is a blue light absorbing material that prevents light at a wavelength corresponding to blue light (e.g., the light at the fourth wavelength emitted by the third LED layer) from activating other LED layers (e.g., the second LED layer and / or the first LED layer).

[0099] The second LED layer may have any of a variety of suitable thicknesses. For example, referring to FIG. 8B, second LED layer 110 has thickness 802c. In some embodiments, for example, the second LED layer has a thickness greater than or equal to 0.5 micrometers. In certain embodiments, the second LED layer has a thickness greater than or equal to 0.5 micrometers, greater than or equal to 1 micrometer, greater than or equal to 2 micrometers, greater than or equal to 5 micrometers, greater than or equal to 10 micrometers, greater than or equal to 50 micrometers, greater than or equal to 100 micrometers, greater than or equal to 500 micrometers, greater than or equal to 1 millimeter, greater than or equal to 2 millimeters, greater than or equal to 5 millimeters, greater than or equal to 1 centimeter, or greater. In certain embodiments, the second LED layer has a thickness less than or equal to 10 centimeters, less than or equal to 1 centimeter, less than or equal to 5 millimeters, less than or equal to 2 millimeters, less than or equal to 1 millimeter, less than or equal to 500 micrometers, less than or equal to 100 micrometers, less than or equal to 50 micrometers, less than or equal to 10 micrometers, less than or equal to 5 micrometers, less than or equal to 2 micrometers, or less than or equal to 1 micrometer. Combinations of the above recited ranges are possible (e.g., the second LED layer has a thickness greater than or equal to 0.5 micrometers and less than or equal to 10 centimeters). Other ranges are also possible. In certain embodiments, the second LED layer is advantageously thin. In certain embodiments, the second LED layer is a micro-LED layer.

[0100] According to certain embodiments, the multicolor stack comprises a third LED layer. Referring to FIGS. 8A-8B, for example, multicolor LED stack 102 comprises third LED layer 112. In some embodiments, third LED layer 112 is disposed over second LED layer 110 such that second LED layer 110 is between first LED layer 108 and third LED layer 112.

[0101] According to some embodiments, the third LED layer comprises a semiconductor. For example, in certain embodiments, the third LED layer comprises a Ill-nitride material (e.g., GaN, InGaN, GaAs, InGaAs, etc.). Other materials for the third LED layer are also possible. In some embodiments, the third LED layer comprises GaN and / or InGaN.

[0102] In certain embodiments, the third LED layer is configured to emit light at a fourth wavelength. In some embodiments, the fourth wavelength is different from the first wavelength, the second wavelength, and the third wavelength. For example, in some embodiments, the fourth wavelength is a wavelength corresponding to blue light. In some embodiments, the fourth wavelength is greater than or equal to 450 nm, greater than or equal to 460 nm, greater than or equal to 470 nm, greater than or equal to 480 nm, or greater than or equal to 485 nm. In certain embodiments, the fourth wavelength is less than 495 nm, less than or equal to 485 nm, less than or equal to 480 nm, less than or equal to 470 nm, or less than or equal to 460 nm. Combinations of the above recited ranges are possible (e.g., the fourth wavelength is greater than or equal to 450 nm and less than 495 nm). Other ranges are also possible.

[0103] According to some embodiments, the light at the fourth wavelength emitted by the third LED layer is reflected by a reflector layer and / or one or more reflector materials such that the light at the fourth wavelength is emitted out of the multicolor LED stack through a surface of the multicolor LED stack that is opposite the substrate. In certain embodiments, for example, as described herein in greater detail, the light at the fourth wavelength emitted by third LED layer 112 is reflected by reflector layer 116, first reflector material 118a, and / or second reflector material 118b such that the light at the fourth wavelength is emitted out of multicolor LED stack 102 through surface 120 of multicolor LED stack 102 that is opposite substrate 106.

[0104] According to some embodiments, the third LED layer comprises a transparent material. In certain embodiments, as described herein in greater detail, the transparent material is polymer 114c.

[0105] The third LED layer may have any of a variety of suitable thicknesses. For example, referring to FIG. 8B, third LED layer 112 has thickness 802d. In some embodiments, for example, the third LED layer has a thickness greater than or equal to 0.5 micrometers. In certain embodiments, the third LED layer has a thickness greater than or equal to 0.5 micrometers, greater than or equal to 1 micrometer, greater than or equal to 2 micrometers, greater than or equal to 5 micrometers, greater than or equal to 10 micrometers, greater than or equal to 50 micrometers, greater than or equal to 100 micrometers, greater than or equal to 500 micrometers, greater than or equal to 1 millimeter, greater than or equal to 2 millimeters, greater than or equal to 5 millimeters, greater than or equal to 1 centimeter, or greater. In certain embodiments, the third LED layer has a thickness less than or equal to 10 centimeters, less than or equal to 1 centimeter, less than or equal to 5 millimeters, less than or equal to 2 millimeters, less than or equal to 1 millimeter, less than or equal to 500 micrometers, less than or equal to 100 micrometers, less than or equal to 50 micrometers, less than or equal to 10 micrometers, less than or equal to 5 micrometers, less than or equal to 2 micrometers, or less than or equal to 1 micrometer. Combinations of the above recited ranges are possible (e.g., the third LED layer has a thickness greater than or equal to 0.5 micrometers and less than or equal to 10 centimeters). Other ranges are also possible. In certain embodiments, the third LED layer is advantageously thin. In certain embodiments, the third LED layer is a micro-LED layer.

[0106] As described herein, multicolor LED stack 102 comprises substrate 106 (e.g., a backplane of a LED stack), in accordance with certain embodiments. In some embodiments, the substrate is substantially transparent to (e.g., it transmits at least 50%, at least 75%, at least 90%, at least 95%, at least 98%, at least 99%, or at least 99.9% of) the light at the first wavelength, the light at the second wavelength, the light at the third wavelength, and / or the light at the fourth wavelength. In certain embodiments, for example, the substrate comprises sapphire, quartz, glass (e.g., soda-lime glass, aluminosilicate glass, borosilicate glass, flexible glass), polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA or acrylic), polyimide (PI), and / or combinations thereof. Other substrate materials are also possible.

[0107] According to some embodiments, one or more of first LED layer 108, second LED layer 110, and / or third LED layer 112 further comprises a polymer (e.g., polymer 114a, 114b, and 114c, respectively). The polymer may, in some embodiments, comprise one or more UV absorbing materials and / or visible light absorbing materials. For example, the polymer may, in some embodiments, absorb at least 50%, at least 75%, at least 90%, at least 95%, at least 98%, at least 99%, or at least 99.9% of the light at the first wavelength, the light at the second wavelength, the light at the third wavelength, and / or the light at the fourth wavelength. In certain embodiments, the polymer comprises a polyimide. Other polymers are also possible, including, for example, any of the polymers described herein with respect to the polymer layer of FIG. 3.

[0108] According to some embodiments, the polymer may comprise a transparent material. In some embodiments, for example, the polymer transmits at least 50%, at least 75%, at least 90%, at least 95%, at least 98%, at least 99%, or at least 99.9% of the light at the first wavelength, the light at the second wavelength, the light at the third wavelength, and / or the light at the fourth wavelength.

[0109] In some embodiments, one or more of first LED layer 108, second LED layer 110, and / or third LED layer 112 further comprises one or more DBRs. According to some embodiments, the one or more DBRs are disposed in polymer 114 (e.g., in polymer 114a, 114b, and / or 114c).

[0110] According to some embodiments, although not shown in FIGS. 8A-8B, the multicolor LED stack comprises one or more polymer layers. In certain embodiments, for example, the multicolor LED stack comprises a polymer layer disposed over the substrate such that the polymer layer is between the substrate and quantum dot layer. In some embodiments, the multicolor LED stack comprises a polymer layer disposed over the quantum dot layer such that the polymer layer is between the quantum dot layer and the first LED layer. In certain embodiments, the multicolor LED stack comprises a polymer layer disposed over the first LED layer such that the polymer layer is between the first LED layer and the second LED layer. In some embodiments, the multicolor LED stack comprises a polymer layer disposed over the second LED layer such that the polymer layer is between the second LED layer and the third LED layer. In certain embodiments, the multicolor LED stack comprises a polymer layer disposed over the third LED layer (e.g., a protective encapsulation layer). According to certain embodiments, the one or more polymer layers comprise any of the polymers described herein with respect to the polymer layer of FIG. 3.

[0111] In some embodiments, the multicolor LED stack comprises a reflector layer. Referring to FIGS. 8A-8B, for example, multicolor LED stack 102 comprises reflector layer 116. According to certain embodiments, reflector layer 116 is disposed over substrate 106 such that reflector layer 116 is between substrate 106 and quantum dot layer 104. In certain embodiments, reflector layer 116 is configured to reflect UV and / or visible light (e.g., emitted by quantum dot layer 104, first LED layer 108, second LED layer 110, and / or third LED layer 112). In some embodiments, the reflector layer described herein can reflect at least 50%, at least 75%, at least 90%, at least 95%, at least 98%, at least 99%, or at least 99.9% of the light at the first wavelength, the light at the second wavelength, the light at the third wavelength, and / or the light at the fourth wavelength that is incident on the reflector layer. In some embodiments, reflector layer 116 is configured to dissipate heat generated from quantum dot layer 104, first LED layer 108, second LED layer 110, and / or third LED layer 112.

[0112] The reflector layer may comprise any of a variety of suitable materials. In some embodiments, for example, the reflector layer comprises a metal, such as aluminum and / or silver. Other metals are also possible.

[0113] According to some embodiments, the multicolor LED stack comprises one or more reflector materials. For example, referring to FIGS. 8A-8B, multicolor LED stack 102 comprises first reflector material 118a and second reflector material 118b. In some embodiments, first reflector material 118a and second reflector material 118b are disposed over substrate 106. In certain embodiments, first reflector material 118a and second reflector material 118b extend perpendicular, within 10° (or within 8°, within 6°, within 4°, within 2°, or within 1°), to a face of substrate 106 over which quantum dot layer 104 is located. In some embodiments, quantum dot layer 104, first LED layer 108, second LED layer 110, and / or third LED layer 112 are disposed between first reflector material 118a and the second reflector material 118b. In certain embodiments, first reflector material 118a and / or second reflector material 118b are configured to reflect UV and / or visible light (e.g., emitted by quantum dot layer 104, first LED layer 108, second LED layer 110, and / or third LED layer 112). In some embodiments, the reflector materials described herein can reflect at least 50%, at least 75%, at least 90%, at least 95%, at least 98%, at least 99%, or at least 99.9% of the light at the first wavelength, the light at the second wavelength, the light at the third wavelength, and / or the light at the fourth wavelength that is incident on the reflector materials.

[0114] In some embodiments, first reflector material 118a and / or second reflector material 118b are configured to dissipate heat generated from quantum dot layer 104, first LED layer 108, second LED layer 110, and / or third LED layer 112.

[0115] The first reflector material and / or the second reflector material may comprise any of a variety of suitable materials. In some embodiments, for example, the first reflector material and / or the second reflector material comprise a metal, such as aluminum and / or silver. Other metals are also possible.

[0116] According to some embodiments, referring to FIG. 8A, the light at the second wavelength (i.e., emitted by first LED layer 108) may activate quantum dot layer 104. In some embodiments, the light at the second wavelength is blocked by a UV absorbing material (e.g., polymer 114a) and / or one or more DBRs (e.g., in polymer 114a) such that the light at the second wavelength is not emitted in a direction towards and / or does not activate other LED layers (i.e., second LED layer 110 and / or third LED layer 112). In FIG. 8A, the light at the second wavelength is represented by solid arrows. In certain embodiments, quantum dot layer 104 emits light at the first wavelength (e.g., upon activation by the light at the second wavelength). In some embodiments, the light at the first wavelength does not activate other LED layers (i.e., first LED layer 108, second LED layer 110, and / or third LED layer 112) because the light at the first wavelength has the lowest energy and / or is emitted in the +z direction by first reflector material 118a and second reflector material 118b. In FIG. 8A, the light at the first wavelength is represented by round dotted arrows. In some embodiments, the light at the third wavelength (i.e., emitted by second LED layer 110) is emitted in all directions but reflected in the +z direction by first reflector material 118a and second reflector material 118b. In FIG. 8A, the light at the third wavelength is represented by square dotted arrows. In certain embodiments, the light at the fourth wavelength (i.e., emitted by third LED layer 112) emitted in the -z direction is blocked by a light absorbing material (e.g., polymer 114b) and / or one or more DBRs (e.g., in polymer 114b) so that it does not active the other LED layers (i.e., first LED layer 108 and / or second LED layer 110). In some embodiments, the light at the fourth wavelength is reflected in the +z direction by first reflector material 118a and second reflector material 118b. In FIG. 8A, the light at the fourth wavelength is represented by dashed arrows.

[0117] According to some embodiments, light emitted by the quantum dot layer and / or one or more LED layers is emitted out of the multicolor LED stack through a surface of the multicolor LED stack that is opposite the substrate. For example, referring to FIG. 8A, light at the first wavelength emitted by quantum dot layer 104, light at the third wavelength emitted by second LED layer 110, and light at the fourth wavelength emitted by third LED layer 112 is emitted out of multicolor LED stack 102 through surface 120 of multicolor LED stack 102 that is opposite substrate 106.

[0118] In some embodiments, the multicolor LED stack is configured such that light emitted by the quantum dot layer and / or one or more LED layers is emitted out of the multicolor LED stack through the substrate. According to certain embodiments, for example, the quantum dot layer, the LED layers, the reflector layer, the reflector materials, and / or the substrate are configured and positioned such that light emitted by the quantum dot layer and / or one or more LED layers is emitted out of the multicolor LED stack through the substrate. In some embodiments, the reflector layer is disposed over the third LED layer and configured to reflect UV and / or visible light (e.g., emitted by the quantum dot layer, the first LED layer, the second LED layer, and / or the third LED layer) towards the substrate. In certain embodiments, the substrate comprises a substantially transparent material that allows light emitted by the quantum dot layer and / or the one or more LED layers to be transmitted through the substrate and out of the multicolor LED stack. In some embodiments, for example, the substrate comprises sapphire and / or glass (e.g., soda-lime glass, aluminosilicate glass, borosilicate glass, flexible glass), as described herein in greater detail.

[0119] FIG. 8C shows a cross-sectional schematic diagram of multicolor LED stack 102’ configured such that light is emitted out of multicolor LED stack 102’ through substrate 106, in accordance with certain embodiments. In some embodiments, referring to FIG. 8C, reflector layer 116 is disposed over third LED layer 112 and configured to reflect light at the first wavelength emitted by quantum dot layer 104 (represented in FIG. 8C by round dotted arrows), light at the third wavelength emitted by second LED layer 110 (represented in FIG. 8C by square dotted arrows), and light at the fourth wavelength emitted by third LED layer 112 (represented in FIG. 8C by dashed arrows) towards substrate 106. In some embodiments, substrate 106 comprises a substantially transparent material (e.g., sapphire and / or glass) that allows light at the first wavelength emitted by quantum dot layer 104, light at the third wavelength emitted by second LED layer 110, and light at the fourth wavelength emitted by third LED layer 112 to be transmitted through the substrate and out of multicolor LED stack 102’. Although not shown in FIG. 8C, the reflector materials (e.g., first reflector material 118a and / or second reflector material 118b) may be configured to reflect UV and / or visible light (e.g., emitted by the quantum dot layer, the first LED layer, the second LED layer, and / or the third LED layer) such that light is emitted out of the multicolor stack through the substrate, in accordance with certain embodiments.

[0120] FIGS. 9A shows a cross-sectional schematic diagram of a multicolor LED stack comprising a reflector layer, in accordance with certain embodiments. FIG. 9B shows a cross- sectional schematic diagram of a multicolor LED stack comprising a reflector layer, a first reflector material, and a second reflector material, in accordance with certain embodiments.

[0121] The multicolor LED stack may have any of a variety of suitable thicknesses. For example, referring to FIG. 8B, multicolor LED stack 102 has thickness 802e. In certain embodiments, the multicolor LED stack has a thickness greater than or equal to 2.5 micrometers, greater than or equal to 5 micrometers, greater than or equal to 10 micrometers, greater than or equal to 50 micrometers, greater than or equal to 100 micrometers, greater than or equal to 500 micrometers, greater than or equal to 1 millimeter, greater than or equal to 2 millimeters, greater than or equal to 5 millimeters, greater than or equal to 1 centimeter, greater than or equal to 2 centimeters, greater than or equal to 5 centimeters, greater than or equal to 10 centimeters, greater than or equal to 20 centimeters, greater than or equal to 30 centimeters, or greater than or equal to 40 centimeters. In certain embodiments, the multicolor LED stack has a thickness less than or equal to 50 centimeters, less than or equal to 40 centimeters, less than or equal to 30 centimeters, less than or equal to 20 centimeters, less than or equal to 10 centimeters, less than or equal to 4 centimeters, less than or equal to 2 centimeters, less than or equal to 1 centimeters, less than or equal to 5 millimeters, less than or equal to 2 millimeters, less than or equal to 1 millimeter, less than or equal to 500 micrometers, less than or equal to 100 micrometers, less than or equal to 50 micrometers, less than or equal to 10 micrometers, or less than or equal to 5 micrometers. Combinations of the above recited ranges are possible (e.g., the multicolor LED stack has a thickness greater than or equal to 2.5 micrometers and less than or equal to 50 centimeters). Other ranges are also possible. In certain embodiments, the multicolor LED stack is advantageously thin.

[0122] According to certain embodiments, the multicolor LED stack has a facial surface area defined by two lateral dimensions that are orthogonal to the thickness of the multicolor LED stack and perpendicular to each other (e.g., length and width). The multicolor LED stack may have any of a variety of suitable facial surface areas. In some embodiments, for example, the facial surface area of the multicolor LED stack is greater than or equal to 1 micrometers2, greater than or equal to 10 micrometers2, greater than or equal to 100 micrometers2, greater than or equal to 1000 micrometers2, greater than or equal to 0.01 millimeters2, greater than or equal to 0.1 millimeters2, greater than or equal to 1 millimeter2, greater than or equal to 10 millimeters2, or greater than or equal to 1 centimeter2. In certain embodiments, the facial surface area of the multicolor LED stack is less than or equal to 10 centimeters2, less than or equal to 1 centimeter2, less than or equal to 10 millimeters2, less than or equal to 1 millimeter2, less than or equal to 0.1 millimeters2, less than or equal to 0.01 millimeters2, less than or equal to 1000 micrometers2, less than or equal to 100 micrometers2, or less than or equal to 10 micrometers2. Combinations of the above recited ranges are possible (e.g., the facial surface area of the multicolor LED stack is greater than or equal to 1 micrometer2and less than or equal to 10 centimeters2). Other ranges are also possible.

[0123] FIG. 13 shows a cross-sectional schematic diagram of a full color LED stack with driving circuits, in accordance with certain embodiments. As shown in FIG. 13, the substrate may comprise one or more driving circuits disposed on the substrate, and the first LED layer, second LED layer, and / or third LED layer may be interconnected to the one or more driving circuits disposed on the substrate. In certain embodiments, referring to FIG. 13, the full color LED stack comprises a reflector layer disposed on a substrate, a quantum dot layer disposed on the reflector layer, a first LED layer disposed on the quantum dot layer, a second LED layer disposed on the first LED layer, and a third LED layer disposed on the second LED layer. In some embodiments, the quantum dot layer is configured to emit light at a first wavelength corresponding to red light, the first LED layer is configured to emit light at a second wavelength corresponding to UV light, the second LED layer is configured to emit light at third wavelength corresponding to green light, and the third LED layer is configured to emit light at a fourth wavelength corresponding to blue light. In some embodiments, the full color LED stack comprises one or more reflector materials disposed on the substrate.

[0124] FIG. 14 shows schematic diagrams comparing conventional RGB LEDs with a full color LED stack, in accordance with certain embodiments. According to some embodiments, the full color LED stack can advantageously achieve a transparent display since only one quarter of the area is blocked by the stack when compared to conventional (e.g., non-stacked) RGB LEDs. In some embodiments, an ultra-high pixel per inch (PPI) display can be achieved with reduced pixel size and compact subpixel density using the full color LED stack. For example, conventional RGB LED displays include three to four subpixels in each pixel for full color operation. In comparison, by stacking the RGB in a vertical manner, such as in the full color LED stack, each pixel takes one subpixel area with three subpixels in vertical array.

[0125] FIG. 15 shows a schematic diagram of a QD / LED device, in accordance with certain embodiments. FIG. 16 shows photographs of a QD / LED device, in accordance with certain embodiments. As shown in FIG. 16, both blue and red lights are emitted without a color filter. However, only red lights are emitted with the color filter since the color filter absorbs the blue light.

[0126] U.S. Provisional Patent Application No. 63 / 654,714, filed May 31, 2024, and entitled “MULTICOLOR LIGHT-EMITTING STACKS AND RELATED METHODS,” is incorporated herein by reference in its entirety for all purposes.

[0127] While several embodiments of the present invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and / or structures for performing the functions and / or obtaining the results and / or one or more of the advantages described herein, and each of such variations and / or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and / or configurations will depend upon the specific application or applications for which the teachings of the present invention is / are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The present invention is directed to each individual feature, system, article, material, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, and / or methods, if such features, systems, articles, materials, and / or methods are not mutually inconsistent, is included within the scope of the present invention.

[0128] The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”

[0129] The phrase “and / or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Other elements may optionally be present other than the elements specifically identified by the “and / or” clause, whether related or unrelated to those elements specifically identified unless clearly indicated to the contrary. Thus, as a non-limiting example, a reference to “A and / or B,” when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A without B (optionally including elements other than B); in another embodiment, to B without A (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

[0130] As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and / or” as defined above. For example, when separating items in a list, “or” or “and / or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of’ or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0131] As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and / or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

[0132] As used herein, “wt%” is an abbreviation of weight percentage. As used herein, “at%” is an abbreviation of atomic percentage.

[0133] Some embodiments may be embodied as a method, of which various examples have been described. The acts performed as part of the methods may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include different (e.g., more or less) acts than those that are described, and / or that may involve performing some acts simultaneously, even though the acts are shown as being performed sequentially in the embodiments specifically described above.

[0134] Use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.

[0135] In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

Claims

CLAIMSWhat is claimed is:

1. A multicolor light-emitting diode (LED) structure, comprising: a substrate; a quantum dot layer disposed over the substrate, wherein the quantum dot layer is configured to emit light at a first wavelength; a first LED layer disposed over the quantum dot layer such that the quantum dot layer is between the substrate and the first LED layer, wherein the first LED layer is configured to emit light at a second wavelength different from the first wavelength; and a second LED layer disposed over the first LED layer such that the first LED layer is between the quantum dot layer and the second LED layer, wherein the second LED layer is configured to emit light at a third wavelength different from the first wavelength and the second wavelength.

2. The structure of claim 1, wherein the substrate is substantially transparent to the light at the first wavelength, the light at the second wavelength, and / or the light at the third wavelength.

3. The structure of any one of claims 1-2, wherein the first wavelength is a wavelength corresponding to red light.

4. The structure of any one of claims 1-3, wherein the second wavelength is a wavelength corresponding to ultraviolet light and / or blue light.

5. The structure of claim 4, wherein the second wavelength is a wavelength corresponding to ultraviolet light, and wherein the first LED layer further comprises an ultraviolet light absorbing material and / or a distributed Bragg reflector.

6. The structure of any one of claims 1-5, wherein the third wavelength is a wavelength corresponding to green light.

7. The structure of any one of claims 1-6, further comprising a third LED layer disposed over the second LED layer such that the second LED layer is between the first LED layer and the third LED layer, wherein the third LED layer is configured to emit light at a fourth wavelength different from the first wavelength, the second wavelength, and the third wavelength.

8. The structure of claim 7, wherein the fourth wavelength is a wavelength corresponding to blue light.

9. The structure of any one of claims 7-8, wherein the substrate is substantially transparent to the light at the fourth wavelength.

10. The structure of any one of claims 1-9, further comprising a polymer layer disposed over the substrate such that the polymer layer is between the substrate and quantum dot layer.

11. The structure of any one of claims 1-10, further comprising a reflector layer disposed over the substrate such that the reflector layer is between the substrate and the quantum dot layer.

12. The structure of any one of claims 7-11, further comprising a first reflector material and a second reflector material disposed over the substrate such that: the first reflector material and the second reflector material extend perpendicular, within 10°, to a face of the substrate over which the quantum dot layer is located; and the quantum dot layer, the first LED layer, the second LED layer, and / or third LED layer are disposed between the first reflector material and the second reflector material.

13. A method of fabricating a multicolor light-emitting diode (LED) structure, forming a quantum dot layer over a substrate, wherein the quantum dot layer is configured to emit light at a first wavelength;forming a first LED layer over a release layer comprising a two-dimensional (2D) material disposed over a growth substrate, wherein the first LED layer is configured to emit light at a second wavelength; removing the first LED layer from the release layer; disposing the first LED layer over the quantum dot layer; forming a second LED layer, wherein the second LED layer is configured to emit light at a third wavelength; and disposing the second LED layer over the first LED layer.

14. The method of claim 13, wherein forming the first LED layer comprises epitaxially growing the first LED layer over the release layer.

15. The method of any one of claims 13-14, wherein the release layer is a first release layer comprising a first 2D material disposed over a first growth substrate, and wherein the second LED layer is formed over a second release layer comprising a second 2D material disposed over a second growth substrate.

16. The method of any one of claims 13-14, wherein the second LED layer is formed over the release layer comprising the 2D material disposed over the growth substrate.

17. The method of any one of claims 13-16, wherein forming the second LED layer comprises epitaxially growing the second LED layer.

18. The method of any one of claims 13-17, further comprising: forming a third LED layer, wherein the third LED layer is configured to emit light at a fourth wavelength; and disposing the third LED layer over the second LED layer.

19. The method of claim 18, wherein the third LED layer is formed over a third release layer comprising a third 2D material disposed over a third growth substrate.

20. The method of claim 18, wherein the third LED layer is formed over the release layer comprising the 2D material disposed over the growth substrate.

21. The method of any one of claims 18-20, wherein forming the third LED layer comprises epitaxially growing the third LED layer.

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