Silicon-based OLED microdisplay

Abstract

The application discloses a silicon-based OLED micro display screen, white light is emitted by an OLED organic material layer under electric driving, intelligent judgment is carried out according to display content, and the optimal working mode is automatically selected, when high saturation pure color needs to be displayed, the pure color transparent mode is switched to, at this time, the super surface optical separation layer keeps the transparent characteristic, and the white light is directly transmitted to the color film unit of the corresponding color, when mixed color needs to be displayed, the color separation mode is started, the incident white light is separated into red, green and blue three primary color lights according to the visible spectrum, and is accurately guided to the corresponding RGB color film unit according to a preset optical path, finally, each color light accurately separated and guided is output through the corresponding color film, and finally, a high-brightness, low-power full-color picture is synthesized. That is, a super surface optical separation layer is additionally arranged between the white light OLED light-emitting layer and the color filter, and display optical utilization efficiency is greatly improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to a silicon-based OLED microdisplay. Background Technology

[0002] The rapid development of near-eye display devices such as virtual reality (VR) and augmented reality (AR) has placed extremely high demands on the performance of microdisplays. Silicon-based OLED microdisplays are considered an ideal solution due to their integration of the high contrast and fast response speed of OLEDs with the high integration and small size of silicon-based circuits. However, this technology still faces fundamental challenges in achieving high-pixel-density full-color displays.

[0003] Currently, the mainstream solution for achieving full-color display in silicon-based OLEDs is a combination of white OLED and color filters, namely W+CF. This technical approach stems from the physical limitations of the fine metal mask (FMM) evaporation process: when the pixel size is less than 10 micrometers, the FMM, due to gravity and thermal expansion deformation, cannot achieve precise alignment and evaporation of the RGB materials, making it difficult to fabricate independently emitting RGB pixels. In contrast, color filters, as photoresist materials, can be micro-patterned using mature semiconductor photolithography processes, thus circumventing the manufacturing difficulties of FMMs. Therefore, the industry adopts the W+CF solution, which involves first fabricating a white OLED and then generating colors using a filter.

[0004] However, the W+CF scheme has a serious drawback: its optical utilization rate is extremely low. Based on an "absorption-filtering" mechanism, the filter transmits the target color light while absorbing most of the non-target light. The red filter absorbs approximately 67% of the light energy, the green filter about 60%, and the blue filter about 80%, resulting in an overall system optical utilization rate of only 20%–30%, with over 70% of the light energy dissipated as heat. Therefore, how to fundamentally improve the optical utilization rate of the W+CF scheme while remaining compatible with silicon-based OLED processes has become a core technical challenge urgently needing to be solved in this field. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a silicon-based OLED microdisplay.

[0006] The embodiments of this application disclose the following technical solutions:

[0007] A silicon-based OLED microdisplay includes: a silicon-based CMOS backplane layer, an OLED functional layer, a metasurface optical separation layer, and a color filter layer;

[0008] The OLED functional layer is disposed on the silicon-based CMOS backplane layer and is used to generate white light under electric drive.

[0009] The metasurface optical separation layer is disposed on the light emission path of the OLED functional layer. The metasurface optical separation layer includes a phase change material layer and an electrode structure for applying an electrical excitation signal to the phase change material layer.

[0010] The color filter layer is disposed on the light-emitting side of the metasurface optical separation layer;

[0011] The electrode structure is used to apply an electrical excitation signal to the phase change material layer, control the phase change material layer to reversibly switch between an amorphous state and a crystalline state, and change the optical control function of the metasurface optical separation layer. When the phase change material layer is in an amorphous state, the metasurface optical separation layer exhibits transparent characteristics to the white light emitted by the OLED functional layer, forming a pure color transparent mode that allows white light to pass directly through the corresponding color filter output. When the phase change material layer is in a crystalline state, the metasurface optical separation layer separates the white light into red, green, and blue light and guides them to the corresponding red, green, and blue filter units in the color filter layer, forming a mixed color separation mode.

[0012] In one possible implementation, the electrode structure is used to apply an electrical excitation signal to the phase change material layer based on a mode control signal, the mode control signal being determined based on the image content to be displayed; when the mode control signal indicates that the displayed content is a highly saturated pure color, a first electrical pulse is applied to put the phase change material layer in an amorphous state; when the mode control signal indicates that the displayed content is a mixed color, a second electrical pulse is applied to put the phase change material layer in a crystalline state.

[0013] In one possible implementation, the phase change material layer is made of GST alloy with different composition ratios, the thickness of the phase change material layer is 100 nm, and the initial state is treated to be amorphous by a specific annealing process.

[0014] In one possible implementation, the metasurface optical separation layer further includes a substrate layer, a nanostructure layer, and a protective layer; the substrate layer is disposed between the light emission path of the electrode structure and the OLED functional layer; the nanostructure layer is sandwiched between the phase change material layer and the substrate layer; the protective layer is wrapped around the outside of the phase change material layer, is made of insulating material, and is etched with through holes to achieve connection with the electrode structure.

[0015] In one possible implementation, the nanostructure layer is composed of periodically arranged subwavelength nanounits; the structural morphology of the nanounits is selected from at least one of cylinders, square prisms, elliptical cylinders, circular holes, square holes, elliptical holes, triangles, hexagons, and free topological shapes.

[0016] In one possible implementation, the electrode structure includes a bottom electrode and a top electrode; the bottom electrode is patterned by photolithography to form a pixel-level electrode structure; the top electrode is made of a transparent conductive material and is patterned by photolithography to form an electrode structure corresponding to the position of the bottom electrode; the phase change material layer is sandwiched between the bottom electrode and the top electrode.

[0017] In one possible implementation, a reflective electrode layer is also included; the reflective electrode layer is disposed between the silicon-based CMOS backplane layer and the OLED functional layer, and is made of a high-reflectivity metal material to reflect the light emitted by the OLED functional layer to reduce light energy loss.

[0018] In one possible implementation, a transparent electrode layer is also included; the transparent electrode layer is disposed on the side of the OLED functional layer away from the reflective electrode layer, is made of a transparent conductive material, and is used to transmit driving current to the OLED functional layer.

[0019] In one possible implementation, a planarization layer is also included; the planarization layer is disposed between the transparent electrode layer and the metasurface optical separation layer, and is made of an insulating transparent material to eliminate the unevenness on the surface of the transparent electrode layer, thereby providing a flat substrate for the fabrication of the metasurface optical separation layer.

[0020] In one possible implementation, a spacer layer is further included; the spacer layer is disposed between the metasurface optical separation layer and the color filter layer, and is used to control the spacing between the metasurface optical separation layer and the color filter layer.

[0021] In one possible implementation, a protective layer and an encapsulation layer are also included; the protective layer and encapsulation layer are disposed on the side of the color filter layer away from the metasurface optical separation layer and are made of an insulating sealing material.

[0022] Compared with the prior art, this application has the following beneficial effects:

[0023] By introducing a purely inorganic, controllable metasurface optical separation layer, this application addresses the problem of low optical utilization (only 20-30%) in traditional W+CF solutions due to their absorption-filtering mechanism. The light extraction mechanism is adjusted to a separation-guidance active control mode: when the phase change material layer is in a crystalline state under electronic control, the metasurface actively separates white light into RGB colors and precisely guides them to the corresponding filter units, thus avoiding the loss of approximately 70% of non-target color light absorbed in traditional solutions. By integrating the metasurface structure between the OLED functional layer and the color filter layer, this application fundamentally solves the core defect of low optical utilization in the W+CF solution while maintaining its small pixel size advantage, enabling silicon-based OLED microdisplays to achieve high luminous efficiency, high brightness, and good mass production capabilities. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1(a) is a schematic diagram of the light output principle of the traditional W+CF scheme;

[0026] Figure 1(b) is a schematic diagram of the light emission principle provided in this application;

[0027] Figure 2 This is a schematic diagram of the silicon-based OLED microdisplay structure provided in the embodiments of this application;

[0028] Figure 3 This is a schematic diagram of the interface structure of a silicon-based OLED device provided in an embodiment of this application;

[0029] Figure 4 This is a schematic diagram of a method process provided in an embodiment of this application;

[0030] Figure 5 Schematic diagrams of various metasurface structures provided in the embodiments of this application;

[0031] Figure 6 This is a schematic diagram of a metasurface micro / nano structure pillar array provided in an embodiment of this application. Detailed Implementation

[0032] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0033] To facilitate understanding of the technical solutions provided in the embodiments of this application, the technical terms involved in the embodiments of this application will be explained below.

[0034] Silicon-based OLED microdisplays refer to miniature display devices that directly fabricate organic light-emitting diode (OLED) devices on a single-crystal silicon CMOS driving backplane. These devices employ a top-emitting structure, typically with individual pixel sizes <10µm and pixel densities exceeding 2000 PPI, and are widely used in near-eye display devices such as VR / AR.

[0035] The white OLED + color filter (W+CF) solution is currently the mainstream technology for achieving full-color display in silicon-based OLEDs. This involves first fabricating a white-light-emitting OLED device, and then using red, green, and blue color filters to achieve RGB three-color display. This solution avoids the technical challenge of fabricating individual pixels smaller than 30µm using fine metal masks (FMMs), but it suffers from low optical utilization.

[0036] Metasurface micro / nano structure unit: The core innovative structure of this application refers to the subwavelength optical modulation structure disposed between the OLED light-emitting layer and the color filter. This structure is composed of periodically arranged nanounits, each with a size smaller than the wavelength of light, enabling precise control of the propagation direction of light of different wavelengths, and achieving the separation and directional propagation of white light.

[0037] Controllable metasurface structure: The core technical feature of the embodiments of this application refers to an electrically controllable optical metasurface structure composed entirely of inorganic materials. This structure achieves dynamic control of optical properties through the electrically controlled switching of GST phase change materials, enabling both spectral separation (color mixing mode) and transparent transmission (pure color mode).

[0038] GST phase change materials: refers to The alloy material exhibits reversible amorphous-crystalline state transition characteristics. Under electrical pulse drive, it can rapidly switch between an amorphous state (low refractive index, n≈4.0) and a crystalline state (high refractive index, n≈7.0) in nanoseconds, adapting to the high refresh rate requirements of displays.

[0039] Spectral separation and guidance function: This refers to the function of the metasurface structure to extract the red, green, and blue light from white light and guide them to the corresponding color filters. Unlike the "absorption-filtering" mechanism of traditional color filter films, the embodiments of this application adopt a "separation-guiding" mechanism, which significantly improves the optical utilization rate within the microdisplay screen.

[0040] Optical utilization rate: refers to the ratio of the final output light intensity of the display device to the light intensity generated by the OLED device. Traditional W+CF schemes have an optical utilization rate of only about 20-30% due to the spectral selective absorption of the color filter; the embodiments of this application can increase it to over 90%.

[0041] Subwavelength optical manipulation refers to the technique of precisely controlling the phase, amplitude, polarization, and other characteristics of light on a scale smaller than the wavelength of light. In the embodiments of this application, the size of the metasurface unit is typically in the range of 100-500 nm, which is smaller than the wavelength of visible light.

[0042] To facilitate understanding of the technical solutions provided in the embodiments of this application, the background technology involved in the embodiments of this application will be described below.

[0043] As mentioned earlier, existing technologies employ microlens arrays and optical microcavities to improve optical efficiency, but both have significant limitations. While microlens arrays can improve light extraction efficiency by 25-30%, they cannot solve the fundamental problem of approximately 70% light absorption in color filters themselves. Furthermore, their manufacturing process requires sub-micron level alignment precision and necessitates complex processes such as thermal reflow, leading to increased costs and difficulties in yield control. Although optical microcavity technology can enhance light extraction efficiency by 30-50%, its cavity length control needs to reach the nanometer level, and different color pixels require differentiated designs. This results in extremely small process tolerances and low yields, failing to overcome the overall efficiency bottleneck of the W+CF solution.

[0044] To address the aforementioned issues, this application introduces a purely inorganic controllable metasurface structure, fundamentally altering the current light extraction mechanism of silicon-based OLEDs. Figure 1(a) illustrates the light extraction principle of the traditional W+CF scheme, while Figure 1(b) illustrates the light extraction principle provided in this application. In the traditional W+CF scheme, the OLED organic material layer emits white light → the white light is filtered and absorbed by the corresponding color filter above the RGB pixels (70% loss of non-target color light) → the RGB pixels output the corresponding target color → multiple sub-pixels synthesize a full-color image. In this invention, the OLED organic material layer emits white light → intelligent display mode determination → pure color transparent mode / color mixing separation mode → the metasurface structure separates the visible spectrum and guides it to the corresponding RGB color film in a preset direction (loss <5%, due to the inherent absorption characteristics of the material, 100% transmission is impossible) → the corresponding RGB filter outputs the corresponding color → RGB synthesizes a full-color image.

[0045] This technology increases the optical utilization rate of silicon-based OLED microdisplays from 20-30% in traditional W+CF solutions to over 90%, approaching the theoretical limit and achieving highly efficient use of light energy. Under the same white OLED driving conditions, it increases screen brightness by 3-5 times, significantly enhancing display effects and meeting the stringent high-brightness display requirements of high-end VR products. Alternatively, it reduces OLED driving power consumption by 60-80% while achieving the same display brightness, effectively improving device battery life and simplifying thermal management design. By reducing OLED driving current and operating temperature, it significantly extends the lifespan of organic light-emitting materials, improving product reliability and long-term stability. It provides a solution fully compatible with existing silicon-based OLED manufacturing processes, enabling industrial application without modifying existing production lines and equipment, greatly reducing the barriers and costs of technology upgrades. Adjustable metasurface structure parameters provide excellent design flexibility, allowing for the development of silicon-based OLED microdisplay products with different specifications and application requirements.

[0046] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0047] The following embodiment illustrates the function and connection relationships of key structures in the silicon-based OLED microdisplay provided in this application. It should be noted that the metasurface optical separation layer and controllable metasurface structure in this application are different expressions of the metasurface optical separation layer. A preferred embodiment of this layer is "purely inorganic" and "controllable." See [link to documentation] Figure 2 ,Should Figure 2 This is a schematic diagram of the silicon-based OLED microdisplay structure provided in an embodiment of this application. Based on the traditional silicon-based OLED device structure, this embodiment adds a metasurface optical separation layer between the white OLED emitting layer and the color filter, thereby significantly improving the display's optical utilization efficiency.

[0048] The silicon-based CMOS backplane layer is the foundation and control system of the entire display device. This layer uses a single-crystal silicon substrate and integrates millions to tens of millions of thin-film transistors using standard CMOS processes to form an active matrix driving circuit. Each transistor precisely controls the switching and grayscale of its corresponding pixel, providing precise current drive for the OLED functional layer above. More importantly, this backplane layer also integrates electrode driving circuitry that controls the metasurface structure, capable of generating the necessary electrical excitation signals based on the displayed content, making it the master controller for intelligent optical modulation.

[0049] The OLED functional layer, disposed above the silicon-based CMOS backplane layer, serves as the light source for the display and employs a top-emitting white light structure. It consists of multiple layers of organic thin-film materials, including a hole injection layer, a hole transport layer, an emissive layer, an electron transport layer, and an electron injection layer. When a driving voltage is applied to the silicon-based backplane, electrons and holes are injected from the cathode and anode, respectively, and recombine in the emissive layer to generate white light. This white light spectrum covers the 400-700nm visible light range, providing a unified light source for subsequent color generation and avoiding the technological challenges of separately depositing RGB pixels in traditional methods.

[0050] The metasurface optical separation layer is disposed on the light emission path of the OLED functional layer. The metasurface optical separation layer includes a phase change material layer and an electrode structure for applying an electrical excitation signal to the phase change material layer; it functions as an intelligent light routing layer. This layer adopts an all-inorganic material system, mainly comprising the phase change material layer and the electrode structure. Preferably, the phase change material layer... The (GST) material is unique in that it can rapidly and reversibly switch between an amorphous and crystalline state under electrical excitation, with the two states exhibiting significantly different refractive indices. The electrode structure consists of a TiN electrode at the bottom and a transparent ITO electrode at the top, used to apply precisely controlled electrical pulses to the phase change material layer. The entire metasurface structure is composed of periodically arranged subwavelength nanounits; through careful design of the unit geometry and arrangement, precise control of the light wavefront is achieved.

[0051] The color filter layer is disposed on the light-emitting side of the metasurface optical separation layer; located at the end of the optical path, it is responsible for the final color purification. Unlike traditional solutions that perform the main filtering function, in this embodiment, its role is transformed into a color refiner. This layer is composed of red, green, and blue filter units arranged in a specific pattern (such as stripes, mosaics, etc.), with each filter unit corresponding to a display pixel. Since the metasurface layer has already completed the main spectral separation and guidance work, the filter only needs to perform minor color correction, which greatly improves the light transmittance, from 20-30% in traditional solutions to over 90%.

[0052] The display features two intelligent operating modes. In pure color transparent mode, the phase change material is in an amorphous state, and the metasurface exhibits transparent properties, allowing white light to be directly transmitted to the filter unit of the target color, achieving the most efficient monochrome display. In color mixing and separation mode, the phase change material transforms into a crystalline state, and the metasurface is activated to perform spectral separation, precisely separating the red, green, and blue components of the incident white light and guiding them to their respective filter units, achieving full-color display while maintaining extremely high optical utilization. The intelligent switching between the two modes is controlled in real time by a control circuit integrated into the silicon-based backplane based on the displayed content, achieving an optimal balance between energy efficiency and display quality.

[0053] For further details regarding other structures, connections, and specific constructions in silicon-based OLED microdisplays, please refer to [link to relevant documentation]. Figure 3 ,Should Figure 3 This is a schematic diagram of the interface structure of a silicon-based OLED device provided in an embodiment of this application. The hierarchical structure of the silicon-based OLED device, from bottom to top, includes:

[0054] Silicon-based CMOS backplane layer: A single-crystal silicon substrate with an integrated pixel driving circuit, approximately 500µm thick.

[0055] Reflective electrode layer: High reflectivity metal electrode (such as aluminum or silver alloy), with a thickness of approximately 100 nm.

[0056] OLED functional layers include a hole injection layer, a hole transport layer, an electron-hole recombination light-emitting layer, an electron transport layer, and an electron injection layer, with a total thickness of approximately 150nm.

[0057] Transparent electrode layer: Transparent conductive material (such as ITO, silver nanowires), with a thickness of about 50nm.

[0058] Planarization layer: Ensures a flat substrate for metasurface fabrication, with a thickness of approximately 200 nm.

[0059] Pure inorganic controllable metasurface optical separation layer: The core innovative structure of this application embodiment includes a substrate layer: Bottom electrode: TiN, GST phase change layer: Nanostructure layer: The top electrode is ITO, which is transparent and conductive.

[0060] Spacer layer: A transparent dielectric layer that controls the distance between the metasurface and the filter.

[0061] Color filter layer: Traditional RGB three-color filter.

[0062] Protective and encapsulation layers: Device protection and sealing structures.

[0063] The core structure of the purely inorganic controllable metasurface layer is further explained below:

[0064] Regarding the material system and functional layering, this metasurface layer is a novel optical element integrated from multiple functional thin films. Its substrate layer employs a transparent and low-refractive-index material. Its main function is to provide a flat, insulating fabrication platform for the entire structure, and its refractive index of approximately 1.46 helps to create the necessary refractive index contrast. The core phase transition control material is GST-225, i.e. Alloys are key to achieving dynamic optical manipulation. They act like an "optical switch," with their refractive index changing dramatically between crystalline (ordered) and amorphous (disordered) states. The scattering units used for filling these alloys employ high-refractive-index alloys. Its refractive index of approximately 2.5 is similar to that of low refractive indices. The combination of the substrate and GST enables effective localization and manipulation of the optical field, achieving precise modulation of the light wavefront through Mie resonance or geometric phase effects. The electrode system, consisting of a TiN bottom electrode and an ITO transparent top electrode, is responsible for efficiently and uniformly applying the electrical excitation signal to the GST phase transition layer to drive its rapid phase transition. Finally, a layer... An insulating protective layer covers the structure to isolate it from the external environment and ensure the physical and chemical stability of the device during fabrication and use.

[0065] Regarding the preset subwavelength structural parameters, the metasurface is designed to operate at the subwavelength scale to achieve efficient control of visible light. Its overall thickness is preset to 1000 nm, making it a compact two-dimensional planar optical device. The period of the nanounits is designed between 300-500 nm, which is smaller than most visible light wavelengths, ensuring that the metasurface can effectively phase-cut light, rather than simply diffract it. The size of each nanostructure is in the range of 100-200 nm, and its precise geometry (e.g., cylinder, prismatic, etc.) is the basis for generating specific optical responses. The thickness of the GST phase transition layer is controlled at 100 nm, which is the optimal balance point for achieving efficient electro-induced phase transition and significant optical modulation depth. The 50-80% fill factor (i.e., the proportion of nanostructures to the unit area) is optimized to achieve the best refractive index contrast and optical performance.

[0066] In its amorphous state, GST has a refractive index n of approximately 4.0–4.2. At this state, the metasurface structure has a weak ability to modulate light, exhibiting a "closed" or transparent state. Applying an electrical pulse of approximately 5.5V transforms it into a crystalline state, significantly increasing the refractive index to 6.8–7.2. At this point, the metasurface is activated, producing strong light scattering and phase modulation. This phase transition process is extremely rapid; crystallization takes approximately 200 nanoseconds, while the amorphization (reset) process takes only about 30 nanoseconds. This nanosecond-level switching speed fully meets the requirements of high frame rate displays, ensuring zero latency in the display during mode switching.

[0067] From a data flow perspective, the core process of the embodiments of this application can be found in [reference needed]. Figure 4 , Figure 4 This application provides a method flowchart illustrating the control logic for dynamically switching optical modes based on display content, as detailed below:

[0068] First, video data input, specifically RGB display data (8 bits per color as an example), is used as input. This is the raw image signal to be displayed, providing the data basis for subsequent mode determination. Second, color saturation and dominant color are calculated (working mode discrimination). This involves analyzing the input RGB video data to calculate the color saturation (to determine the vibrancy of colors) and dominant color (the color type with the highest proportion in the image), thereby determining the appropriate working mode (solid color transparency mode or mixed color separation mode).

[0069] Third, mode switching control (pure color transparency or mixed color separation), which triggers mode switching control based on the judgment results of "color saturation and dominant color" to select the corresponding optical mode: For the pure color display branch: when the image is monochrome or low-saturation pure color content, the GST phase change material layer is controlled to switch to the amorphous state. At this time, the pure inorganic controllable metasurface optical separation layer exhibits transparent characteristics, and light is directly output through the corresponding filter, achieving efficient pure color display (without spectral separation loss). For the mixed color display branch: when the image is high-saturation mixed color content, the GST phase change material layer is controlled to switch to the crystalline state, activating the metasurface's spectral separation function. White light is separated into red, green, and blue light, which are then directed to the corresponding filter units in the color filter layer and finally output through the corresponding filter, achieving high-quality mixed color display.

[0070] Through a closed-loop logic of data-driven, pattern-discrimination, and optical control, intelligent adaptation to different display content is achieved, which not only ensures the high efficiency of pure color display, but also meets the high color saturation requirements of mixed color display, thus breaking through the optical utilization bottleneck of traditional silicon-based OLED microdisplays from a mechanism perspective.

[0071] This application also provides a complete fabrication process for a silicon-based OLED microdisplay with ultra-high optical utilization. The key steps are analyzed in detail below:

[0072] The first stage is the fabrication of white OLED devices. The goal of this stage is to build a high-efficiency white light source on a silicon-based CMOS backplane.

[0073] First, a high-reflectivity anode (such as a silver alloy) is formed on a silicon substrate with the completed driving circuitry using a sputtering process. This layer also serves as a mirror for the optical microcavity. Subsequently, under ultra-high vacuum conditions, organic functional thin films such as a hole injection layer, a hole transport layer, a white light emitting layer, and an electron transport layer are sequentially deposited using a fine evaporation technique, with a total thickness of approximately 150 nm, ultimately forming a white light emitting structure that can cover the 400-700 nm visible spectrum.

[0074] Next, a transparent cathode (such as ITO) is deposited to complete the top-emission OLED device structure. To ensure the flatness of the substrate for subsequent metasurface structure fabrication, a planarization layer needs to be prepared on top of the cathode. This step is crucial for ensuring the precision of the metasurface nanostructure.

[0075] The OLED device must be able to achieve an initial brightness of 20,000 nits under driving conditions to provide sufficient light source for the final high-brightness display output.

[0076] The second stage involves the fabrication of metasurface structures, aiming to build an electrically controllable smart optical layer on top of the OLED.

[0077] Step 2.1: Substrate preparation

[0078] By spin coating on the surface of the OLED planarization layer The precursor, utilizing the inherent high uniformity of the spin coating process, allows for film thickness uniformity control within ±2%, which is crucial for ensuring the consistent optical properties of the subsequent nanostructures. The subsequent heat treatment curing process not only removes the solvent but also... The film is densified to form a transparent substrate layer with stable mechanical properties and a smooth surface.

[0079] Step 2.2: Bottom Electrode Fabrication

[0080] A 30nm thick TiN film prepared by magnetron sputtering exhibits excellent conductivity, high-temperature stability, and perfect compatibility with semiconductor processes. Photolithographic patterning defines the TiN film as a pixel-level bottom electrode, enabling precise electrical control of the metasurface down to each individual pixel, laying the foundation for localized, independent phase transition modulation. Final plasma cleaning ensures a contamination-free electrode surface, guaranteeing good contact with the upper film layer.

[0081] Step 2.3: Preparation of GST phase change layer

[0082] A 100 nm thick layer was deposited by RF magnetron sputtering in an inert Ar atmosphere. The thin film ensures the accuracy and uniformity of its composition. A specific annealing process after deposition is a key step. Its purpose is not to crystallize the film, but to release internal stress and stabilize its amorphous structure, thereby ensuring that the GST layer of all pixel units is in a consistent and stable initial state (high-resistivity state).

[0083] Step 2.4: Preparation of protective layer

[0084] The design aims to protect the sensitive GST layer and enable vertical interconnects. A 20nm thick layer was grown using a low-temperature atomic layer deposition process at 150°C. The insulating layer, produced using a low-temperature process, avoids thermal damage to the underlying GST and OLED devices. The layer effectively prevents the GST material from being oxidized or physically damaged in subsequent processes. The subsequent via etching precisely exposes the underlying bottom electrode, creating conditions for forming an electrical connection with the top electrode later.

[0085] Step 2.5: Nanostructure Preparation

[0086] First, an electron beam resist is spin-coated. Then, electron beam lithography is used to define the desired subwavelength nanopattern (100-500nm) with its ultra-high resolution (up to the nanometer level). Finally, a patterned mask is obtained through development.

[0087] By leveraging the anisotropic properties of reactive ion etching, the pattern on the resist is precisely transferred downwards, etched onto the substrate layer. Nanotemplates.

[0088] Utilizing the excellent step coverage capability of atomic layer deposition (ALD) technology, a 300 nm thick layer was conformally deposited within a nanotemplate. This forms high-refractive-index nano-scattering units.

[0089] Finally, chemical mechanical polishing is used to remove excess material from the surface. This restores the surface to a globally flat state, leaving only the areas embedded in the template. Nanostructures provide a smooth surface for top electrode fabrication.

[0090] Step 2.6: Top Electrode Fabrication

[0091] A 50 nm thick ITO transparent top electrode was fabricated by magnetron sputtering, with its sheet resistance controlled below 20 ohms per square, ensuring that the electrical excitation signal could be applied uniformly and with low loss to the entire pixel area. The high transmittance of ITO in the visible light band guaranteed the light extraction efficiency. Finally, photolithographic patterning enabled the top and bottom electrodes to form a complete driving circuit, achieving effective control of the phase change layer.

[0092] The third stage is the preparation of the spacer layer.

[0093] Select Alternatively, specific transparent organic materials can be used to form uniform thin films through processes such as chemical vapor deposition or spin coating. The core requirements for this material are high transmittance in the visible light band and good adhesion to the upper and lower layers.

[0094] The thickness of the spacer layer is not arbitrary, but a critical parameter determined through rigorous optical simulation and design. Its thickness directly affects the optical interference and coupling effects between the light waves emitted from the metasurface and the filter. By precisely controlling this thickness, specific wavelengths of light (such as red light) separated and guided by the metasurface can achieve optimal wavefront phase when reaching the corresponding color filter, thereby maximizing the transmission through the filter while suppressing stray light, ultimately achieving global optimization of light energy utilization efficiency.

[0095] After depositing the spacer layer, it can be subjected to surface treatments such as plasma treatment or coating with adhesion promoters. This aims to improve the free energy and wettability of the spacer layer surface, ensuring that the subsequently fabricated color filters can bond firmly to it, preventing interface delamination, and guaranteeing the long-term reliability of the device under thermal cycling or mechanical stress.

[0096] The fourth stage is the integration of color filters.

[0097] First, a red negative photoresist is spin-coated. Exposure causes the areas where the red filter needs to be retained to crosslink and cure. Then, development removes the photoresist from the unexposed areas, forming a red pixel array. Subsequently, this coating, exposure, and development process is repeated to sequentially prepare green and blue filter arrays. Negative photoresist is preferred because it typically offers better color purity and chemical resistance.

[0098] The alignment accuracy is precisely controlled to ±0.5μm. A high-precision photolithography machine must be used during the fabrication of each color filter to ensure precise alignment between its pattern and the underlying metasurface's nanostructure and pixel electrodes. This ±0.5μm alignment accuracy requirement ensures that red, green, and blue light, precisely guided to predetermined positions by the metasurface, can be accurately received by the corresponding filter units. Any large alignment deviation will cause the guided light to illuminate the wrong filter, resulting in color mixing, decreased brightness, and reduced contrast.

[0099] After all functional layers are fabricated, overall encapsulation is essential. This typically involves depositing or bonding a dense thin-film encapsulation layer over the filter or sealing it with a glass cover. The fundamental purpose is to create a highly airtight protective barrier, completely blocking moisture and oxygen from the environment. Because some functional layers in OLED organic materials and metasurfaces are extremely sensitive to the environment, they will rapidly fail once exposed to water and oxygen. Therefore, robust encapsulation is the ultimate guarantee for ensuring the long lifespan and reliability required for commercial applications.

[0100] In one possible implementation, the metasurface structure employs... / Component system. That is, using silicon nitride ( As a high-refractive-index nanostructure material, it is compatible with silicon dioxide (SiO2). The substrate and surface work together to construct the metasurface. Its most significant advantage lies in its superior optical performance: and Both materials exhibit extremely high transparency across the entire visible light spectrum, with negligible optical absorption loss, providing an ideal material basis for achieving maximum optical utilization. Furthermore, both are core dielectric materials in standard semiconductor processes, with mature deposition, etching, and patterning techniques. They possess natural and excellent process compatibility with existing silicon-based OLED manufacturing processes, minimizing the difficulty and risk of industrial integration. However, this approach also has certain limitations, primarily its relatively limited refractive index contrast. n≈2.0, (where n≈1.46).

[0101] One possible implementation involves an organic / inorganic metasurface hybrid system. Specially designed high-performance organic polymers or organic-inorganic hybrid materials are used as the core functional materials and integrated with inorganic electrodes and a substrate. Its core advantage lies in the unparalleled molecular designability of organic materials. Through precise molecular structure control, key optical parameters such as refractive index and dispersion can be "customized" within a certain range, thereby achieving more refined optical control. Furthermore, most organic materials can be processed using low-temperature solution methods such as spin coating and inkjet printing, with preparation temperatures significantly lower than traditional inorganic thin-film processes. This greatly reduces the thermal budget and potential damage to the heat-sensitive underlying OLED devices, providing greater flexibility for the structural design and integration of the entire device.

[0102] In one possible implementation, the metasurface structure can be a columnar array structure, composed of periodically arranged cylinders, square cylinders, or elliptical cylinders. Its fabrication is relatively simple, and the related modeling, simulation, and processes are well-established. With fewer design parameters, only the diameter / side length and period need to be optimized, resulting in a lighter computational and optimization burden. This represents an efficient and robust engineering approach for achieving the functionality of the embodiments described in this application.

[0103] In one possible implementation, the metasurface structure can be a hole array structure. In contrast to columnar structures, this structure involves etching periodic circular, square, or other shaped holes into a single, uniformly shaped thin film with a high refractive index (such as polycrystalline silicon or α-Si). This structure requires less material and can be simpler to fabricate; for example, it may only require depositing a single thin film and performing a single patterning etching. This reduces raw material costs and improves manufacturing efficiency, offering economic advantages, especially in large-area production.

[0104] In one possible implementation, the metasurface structure can be a free-form structure. Its morphology is not limited to regular geometry, but rather, through reverse design methods such as machine learning, genetic algorithms, or topology optimization, the algorithm automatically determines the optimal complex shape within a given design space. This approach can overcome the limitations of human intuition and traditional shapes, theoretically achieving the highest upper limits of optical performance, such as wider operating bandwidth, higher efficiency, and lower crosstalk.

[0105] See Figure 5 , Figure 5 Schematic diagrams of various metasurface structures provided in the embodiments of this application. Multiple single-column designs are shown, including top shapes (e.g., square, with cross-grooves, patterned structures, etc.) and overall three-dimensional structures. Key parameters include Weq (equivalent unit size), H (column height), and P (base size). Custom combinations can be simulated according to actual needs, such as adjusting unit shape and size parameters. See also... Figure 6 , Figure 6 This is a schematic diagram of a metasurface micro / nano structure pillar array provided in an embodiment of this application. It is composed of metasurface micro / nano single pillars of various shapes (such as pillars of different heights and top shapes) arranged periodically or non-periodically to form a dense three-dimensional array structure.

[0106] In one possible implementation, the basic material composition of metasurface structures has broad adaptability. Besides typical... In addition to the (GST-225) alloy, this material system also includes, but is not limited to, other proportions of GeSbTe series phase change materials, such as GST-124 with different phase change properties. ), GST-326 ( These materials, by adjusting the elemental ratios of germanium, antimony, and tellurium, allow for precise control of key parameters such as phase transition temperature, crystallization rate, and optical constants. Furthermore, to further optimize material performance, nitrogen doping and carbon doping can be used to modify GST materials. Nitrogen doping significantly improves the thermal stability and amorphous resistivity of phase change materials, while carbon doping effectively inhibits grain growth and enhances the cycle durability of the material. These modification measures all contribute to improving the operational reliability and lifespan of metasurface devices.

[0107] In one possible implementation, the spectral separation and guidance control methods exhibit diverse technical paths. Besides the aforementioned direct phase transition control via electrical pulses, various physical mechanisms can be employed, including but not limited to resistance heating phase transition control, photoinduced phase transition control, thermally induced phase transition control, and magnetic field-assisted phase transition control. Resistance heating control induces phase transitions through the Joule heating effect, suitable for scenarios with less stringent timing requirements; photoinduced phase transition control utilizes laser pulses to achieve non-contact, rapid, localized phase transitions, enabling high spatial resolution modulation; thermally induced phase transition control achieves thermal field modulation through integrated micro-heating elements, offering the advantage of simple actuation; and magnetic field-assisted phase transition control, by combining the effects of thermal and magnetic fields, is expected to lower the phase transition energy threshold and improve phase transition uniformity. This diversity of control methods provides flexible options for metasurface manipulation in different application scenarios.

[0108] In one possible implementation, metasurface structures exhibit a rich variety of geometric forms. Besides typical cylindrical, square, and elliptical cylinders, they also include perforated structures such as circular, square, and elliptical holes, as well as polygonal geometries like triangles and hexagons. These regular structures achieve phase modulation of light waves through electromagnetic resonance. Furthermore, metasurface structures can also employ free-form structures generated using advanced algorithms such as machine learning and topology optimization. These irregular structures can overcome the limitations of traditional symmetrical structures, achieving more complex optical field manipulation functions. In addition, gradient-varying structures can achieve the special function of wavefront shaping through continuous changes in unit parameters, while topology-optimized structures use mathematical methods to find the optimal material distribution that satisfies specific optical properties. This diversity of structural forms provides a broad design space for the continuous optimization of metasurface optical properties and the development of innovative functions.

[0109] Based on the technical features of this application, its significant technical effects can be derived, as detailed below:

[0110] This application embodiment introduces a GST-based... The metasurface structure, made of pure inorganic materials, revolutionizes the light emission mechanism with a "separation-guiding" approach. In its crystalline state, this structure precisely separates the RGB components of white light according to wavelength and guides them to the corresponding color filters, avoiding absorption losses of non-target colors. In its amorphous state, it remains transparent, allowing light to pass through directly. This revolutionary physical mechanism fundamentally solves the problem of light energy waste, thereby increasing optical utilization from less than one-third of traditional solutions to over 90%. Consequently, under the same OLED driving conditions, screen brightness can be increased by 3-5 times.

[0111] The dual-mode adaptive switching mechanism proposed in this application allows the system to operate at its highest performance (color mixing and separation mode) without always being in this mode. When displaying highly saturated pure colors, the system switches to pure color transparent mode, where light energy is output directly with almost no loss, eliminating the need for high-brightness driving of the OLED. This on-demand intelligent mechanism significantly reduces the average driving current required by the OLED and the overall system power consumption (60-80%) while achieving the same display brightness. The reduced power consumption directly decreases device heat generation, and the reduced driving current also significantly slows down the aging rate of the OLED's organic materials, thereby greatly extending the lifespan of the display.

[0112] Applying GST phase change materials to optical modulation, the significant refractive index change between its amorphous and crystalline states (n≈4.0 to n≈7.0) provides ample modulation for efficient optical function switching. More importantly, GST's phase transition switching time is on the nanosecond scale (200ns for crystallization, 30ns for amorphization), which is much faster than the display frame time (e.g., 8.3ms for a 120Hz refresh rate). Therefore, the switching of metasurface operating modes can be completed rapidly within the blanking period between frames, with zero latency to the displayed content, seamlessly adapting to the display requirements of 240Hz and even higher refresh rates, ensuring smooth and high-quality dynamic images.

[0113] This application embodiment ensures that all materials (GST, , The fabrication processes (TiN, ITO) and manufacturing techniques (sputtering, ALD, electron beam lithography, RIE) are fully compatible with existing silicon-based OLED semiconductor production lines. This means that there is no need to develop entirely new production lines or make major modifications to existing equipment; it can be directly integrated on a mature manufacturing platform. This high degree of process compatibility greatly reduces the barriers, risks, and costs of industrialization, while ensuring high yields and consistency in large-scale production.

[0114] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems or apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0115] It should be understood that in this application, "at least one" refers to one or more items, and "more" refers to two or more items. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one" of a, b, or c can represent: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, and c can be single or multiple.

[0116] It should be understood that the terms center, longitudinal, transverse, up, down, front, back, left, right, vertical, horizontal, top, bottom, inside, outside, etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0117] It should be noted that, unless otherwise explicitly specified and limited, the terms installation, connection, and linking should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0118] It should also be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the statement "comprising a..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0119] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0120] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A silicon-based OLED microdisplay, characterized in that, include: Silicon-based CMOS backplane layer, OLED functional layer, metasurface optical separation layer and color filter layer; The OLED functional layer is disposed on the silicon-based CMOS backplane layer and is used to generate white light under electric drive. The metasurface optical separation layer is disposed on the light emission path of the OLED functional layer. The metasurface optical separation layer includes a phase change material layer and an electrode structure for applying an electrical excitation signal to the phase change material layer. The color filter layer is disposed on the light-emitting side of the metasurface optical separation layer; The silicon-based CMOS backplane layer integrates a control circuit, which receives input RGB display data, analyzes the RGB display data, and calculates the color saturation and dominant color of the image. Based on the analysis results of the color saturation and dominant color, the display mode is determined. When the image is determined to be monochrome or low-saturation pure color content, a mode control signal is generated to indicate the use of pure color transparency mode; when the image is determined to be high-saturation mixed color content, a mode control signal is generated to indicate the use of mixed color separation mode. The electrode structure is used to apply an electrical excitation signal to the phase change material layer, control the phase change material layer to reversibly switch between an amorphous state and a crystalline state, and change the optical control function of the metasurface optical separation layer. The electrode structure responds to the mode control signal and applies an electrical pulse excitation to the phase change material layer. When the mode control signal indicates that the display content is a high-saturation pure color, a first electrical pulse is applied to make the phase change material layer amorphous. The metasurface optical separation layer exhibits transparent characteristics to the white light emitted by the OLED functional layer, forming a pure color transparent mode, allowing white light to be directly output through the corresponding color filter. When the mode control signal indicates that the displayed content is mixed colors, a second electrical pulse is applied to make the phase change material layer crystalline, the metasurface optical separation layer is activated, the white light is separated into red, green and blue light and guided to the corresponding red, green and blue filter units in the color filter layer, thus forming a mixed color separation mode.

2. The silicon-based OLED microdisplay according to claim 1, characterized in that, The electrode structure is used to apply an electrical excitation signal to the phase change material layer based on a mode control signal, wherein the mode control signal is determined based on the content of the image to be displayed; when the mode control signal indicates that the displayed content is a high-saturation pure color, a first electrical pulse is applied to make the phase change material layer in an amorphous state. When the mode control signal indicates that the displayed content is mixed colors, a second electrical pulse is applied to make the phase change material layer crystalline.

3. The silicon-based OLED microdisplay according to claim 1, characterized in that, The phase change material layer is made of GST alloy with different composition ratios, and the thickness of the phase change material layer is 100nm. The initial state is treated to be amorphous by a specific annealing process.

4. The silicon-based OLED microdisplay according to claim 1, characterized in that, The metasurface optical separation layer further includes a substrate layer, a nanostructure layer, and a protective layer; the substrate layer is disposed between the light emission path of the electrode structure and the OLED functional layer; the nanostructure layer is sandwiched between the phase change material layer and the substrate layer; the protective layer is wrapped around the outside of the phase change material layer, is made of insulating material, and is etched with through holes to achieve connection with the electrode structure.

5. The silicon-based OLED microdisplay according to claim 4, characterized in that, The nanostructure layer is composed of periodically arranged subwavelength nanounits; the structural morphology of the nanounits is selected from at least one of cylinders, square cylinders, elliptical cylinders, circular holes, square holes, elliptical holes, triangles, hexagons and free topological shapes.

6. The silicon-based OLED microdisplay according to claim 1, characterized in that, The electrode structure includes a bottom electrode and a top electrode; the bottom electrode is patterned by photolithography to form a pixel-level electrode structure; the top electrode is made of a transparent conductive material and is patterned by photolithography to form an electrode structure corresponding to the position of the bottom electrode; the phase change material layer is sandwiched between the bottom electrode and the top electrode.

7. The silicon-based OLED microdisplay according to claim 1, characterized in that, It also includes a reflective electrode layer; the reflective electrode layer is disposed between the silicon-based CMOS backplane layer and the OLED functional layer, and is made of a high-reflectivity metal material, used to reflect the light emitted by the OLED functional layer to reduce light energy loss.

8. The silicon-based OLED microdisplay according to claim 7, characterized in that, It also includes a transparent electrode layer; the transparent electrode layer is disposed on the side of the OLED functional layer away from the reflective electrode layer, is made of a transparent conductive material, and is used to transmit driving current to the OLED functional layer.

9. The silicon-based OLED microdisplay according to claim 8, characterized in that, It also includes a planarization layer; the planarization layer is disposed between the transparent electrode layer and the metasurface optical separation layer, and is made of an insulating transparent material, used to eliminate the unevenness on the surface of the transparent electrode layer and provide a flat substrate for the preparation of the metasurface optical separation layer.

10. The silicon-based OLED microdisplay according to claim 1, characterized in that, It also includes a spacer layer; the spacer layer is disposed between the metasurface optical separation layer and the color filter layer, and is used to control the spacing between the metasurface optical separation layer and the color filter layer.

11. The silicon-based OLED microdisplay according to claim 1, characterized in that, It also includes a protective layer and an encapsulation layer; the protective layer and encapsulation layer are disposed on the side of the color filter layer away from the metasurface optical separation layer, and are made of insulating and sealing material.

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