MicroLED subpixel aging slope preset structure and method

Abstract

This invention discloses a MicroLED sub-pixel aging slope preset structure and method, comprising a full-color MicroLED light-emitting structure disposed on a CMOS backplane. Each sub-pixel of the full-color MicroLED light-emitting structure is independently electrically connected to a driving circuit in the CMOS backplane. Each sub-pixel is provided with a control structure that presets its aging slope, and the control structure has irreversible structural parameter differences between different sub-pixels. This invention introduces irreversible differences at the structural level during the pixel design and manufacturing stages, enabling different sub-pixels to have preset equivalent aging slopes. This achieves consistent convergence of brightness and chromaticity throughout the display's lifespan, alleviates brightness and chromaticity drift caused by inconsistent sub-pixel aging rates, reduces reliance on runtime current compensation and complex algorithms, reduces calibration frequency, and improves system stability. Furthermore, the aging behavior is determined by the structure, making it highly deterministic and predictable.

Description

Technical Field

[0001] This invention belongs to the field of micro-light-emitting diode display technology, specifically relating to a MicroLED sub-pixel aging slope preset structure. This invention also relates to a MicroLED sub-pixel aging slope preset method. Background Technology

[0002] During the long-term use of MicroLED displays, the luminous efficiency of pixels and subpixels gradually decreases over time; this phenomenon is commonly referred to as aging. The aging process manifests as decreased brightness, spectral changes, and drift in electrical properties.

[0003] Because different color sub-pixels (such as red, green, and blue) have inherent differences in material systems, light-emitting mechanisms, current densities, thermal loads, and light extraction efficiency, their aging behavior is usually inconsistent, and the brightness decay rate of different sub-pixels varies significantly over time. Inconsistent sub-pixel aging rates can lead to the following problems: spatial unevenness in display brightness over time; color balance drift over time; significant image quality degradation in the later stages of display lifespan; and the need for frequent system calibration, increasing driver and algorithm complexity.

[0004] In existing technologies, the inconsistent aging problem of MicroLEDs is usually addressed by methods similar to demura, which correct the driving current of pixels or subpixels during manufacturing or use, or by dynamically adjusting the brightness output through runtime algorithms. These solutions are post-use compensation methods; their essence is to correct the aging results rather than designing the aging behavior itself, and they still rely on complex driving circuits, algorithm models, and long-term calibration processes.

[0005] Therefore, there is an urgent need for a structural-level solution that can plan aging behavior in advance during the pixel design stage, so that different sub-pixels can naturally converge to a consistent state during their lifespan. Summary of the Invention

[0006] The purpose of this invention is to provide a preset structure for the aging slope of MicroLED sub-pixels, which solves the problem of brightness and chromaticity drift over time caused by inconsistent aging slopes of different sub-pixels in existing MicroLED displays.

[0007] Another objective of this invention is to provide a method for presetting the aging slope of MicroLED sub-pixels.

[0008] The first technical solution adopted in this invention is: a MicroLED sub-pixel aging slope preset structure, including a full-color MicroLED light-emitting structure disposed on a CMOS backplane, each sub-pixel of the full-color MicroLED light-emitting structure forming an independent electrical connection with the driving circuit in the CMOS backplane, and each sub-pixel being provided with a control structure that presets its aging slope, and the control structure having irreversible structural parameter differences between different sub-pixels.

[0009] The first technical solution of this invention is further characterized by: The control structure includes light-emitting areas of different sizes among different sub-pixels, and the light-emitting area is the area of ​​the mesa region of the MicroLED light-emitting structure.

[0010] The light-emitting areas of different sizes satisfy the following: in the same pixel unit, the light-emitting area of ​​blue sub-pixels is the smallest, the light-emitting area of ​​red sub-pixels is the largest, and the difference in light-emitting area between sub-pixels of different colors is 30% to 80%.

[0011] The control structure includes current spreading layers with different thicknesses between different sub-pixels, and the current spreading layers are n-type transparent electrode layers disposed above the MicroLED light-emitting structure.

[0012] In current spreading layers of different thicknesses, the thickness of the n-type transparent electrode layer of the blue photon is less than that of the red photon.

[0013] The control structure includes a thermal path structure with different interface thermal resistances between different sub-pixels. The thermal path structure is set between the MicroLED light-emitting structure and the CMOS backplane or in the encapsulation layer above the MicroLED light-emitting structure.

[0014] Among thermal path structures with different interface thermal resistances, the interface thermal resistance of the thermal path structure in the blue photonic pixel region is higher than that in the red photonic pixel region.

[0015] The control structure includes light extraction structures with different geometric dimensions between different sub-pixels, and the light extraction structures are set on the light-emitting surface of the MicroLED light-emitting structure.

[0016] The light extraction structure includes a surface roughening layer and a microlens structure. In the light extraction structures with different geometric sizes, the surface roughening depth of the red photon sub-pixel light extraction structure is 120–180 nm and the microlens height is 1.2–1.8 μm; the surface roughening depth of the blue photon sub-pixel light extraction structure is 50–80 nm and the microlens height is 0.5–0.8 μm.

[0017] The second technical solution adopted in this invention is: a MicroLED sub-pixel aging slope preset method. In the MicroLED pixel design and manufacturing stage, for different sub-pixels within the same pixel unit, at least one physical structural parameter is irreversibly differentiated. The set physical structural parameters include the light-emitting area of ​​the sub-pixel, the thickness of the current spreading layer, the interface thermal resistance of the thermal path, or the geometric dimensions of the light extraction structure. Through differentiated setting, different sub-pixels form different current densities, operating temperatures, or initial light extraction efficiencies under the same driving conditions, thereby presetting the aging slope of each sub-pixel.

[0018] The beneficial effects of this invention are as follows: The MicroLED sub-pixel aging slope preset structure and method of this invention introduces irreversible differences at the structural level during the pixel design and manufacturing stages, enabling different sub-pixels to have preset equivalent aging slopes. This achieves consistent convergence of brightness and chromaticity throughout the display's lifespan, alleviates brightness and chromaticity drift caused by inconsistent aging rates of RGB sub-pixels, reduces reliance on runtime current compensation and complex algorithms, decreases calibration frequency, and improves system stability. Furthermore, the aging behavior is determined by the structure, making it highly deterministic and predictable. This invention is easily integrated with existing MicroLED manufacturing and packaging processes, significantly improving the long-term image quality stability and reliability of MicroLED displays. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the MicroLED sub-pixel aging slope preset structure of the present invention. Figure I ; Figure 2 This is a schematic diagram of the MicroLED sub-pixel aging slope preset structure of the present invention. Figure II ; Figure 3 This is a schematic diagram of the MicroLED sub-pixel aging slope preset structure of the present invention. Figure III ; Figure 4 This is a schematic diagram of the MicroLED sub-pixel aging slope preset structure of the present invention. Figure IV ; Figure 5 This is the aging characteristic curve of the MicroLED sub-pixel aging slope preset structure of the present invention.

[0020] In the figure, 1. CMOS backplane, 2. MicroLED light-emitting structure, 3. n-type transparent electrode layer, 4. thermal path structure, 5. light extraction structure; 11. Anode electrode; 12. Cathode electrode; 21. n-type semiconductor layer, 22. light-emitting layer, 23. p-type semiconductor layer, 24. p-type contact electrode layer. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0022] Example 1 This invention provides a method for preset aging slope of MicroLED sub-pixels. During the design and manufacturing stage of MicroLED pixels, by irreversibly differentiating the physical structure parameters of sub-pixels of different colors or positions, each sub-pixel exhibits a preset aging rate under the same driving conditions, thereby achieving consistent convergence of brightness and chromaticity within the device's lifespan.

[0023] The method is based on the following implementation path: In the process of MicroLED chip fabrication, pixel pattern definition, electrode formation and packaging, by quantitatively controlling the key structural parameters, different sub-pixels can form controllable differences in initial current density, operating temperature and light extraction efficiency, thereby determining their aging slope (brightness-time change slope).

[0024] In one embodiment, the aging slope is controlled by differentiating the effective light-emitting area of ​​the sub-pixels. Specifically, in the pixel definition process (photolithography + dry etching), the light-emitting area of ​​different sub-pixels is designed to have different sizes ranging from 6μm×6μm to 10μm×10μm. For example, in the same pixel unit, the blue light sub-pixel is designed to be 6μm×6μm, the green light to be 7μm×7μm, and the red light to be 8μm×8μm. Under the same driving current (e.g., 5–20μA), their equivalent current densities are approximately 140–550 A / cm², respectively. 2 100~400A / cm 2 and 80~300A / cm 2 Because higher current density leads to stronger defect generation and thermal accumulation effects, blue sub-pixels have a higher aging rate.

[0025] In another embodiment, differences in current density distribution are achieved through current spreading and electrode structure design. Specifically, by adjusting the thickness of the transparent electrode layer (e.g., varying the ITO thickness within the range of 80–200 nm) or introducing current spreading layers of different sizes, the uniformity of current distribution within the sub-pixel can be varied. For example, a thinner electrode layer (approximately 80–100 nm) is used in the blue sub-pixel to achieve a higher degree of current concentration; while a thicker electrode layer (approximately 150–200 nm) is used in the red sub-pixel to improve current spreading capability, thereby reducing local current density peaks.

[0026] In another embodiment, operating temperature differentials are controlled by varying the thermal path structure. Specifically, different thermal resistance structures are introduced between the pixel and the backplane or in the encapsulation layer above the pixel. For example, a higher interface thermal resistance (approximately 2 × 10⁻⁶) is set in the blue sub-pixel region. -7 ~5×10 -7 m 2 (·K / W), while a lower thermal resistance structure (approximately 0.5×10) is used in the red light region. -7 ~2×10 -7 m 2 (·K / W). Typical operating power density is 10–30 W / cm³. 2 Under these conditions, a temperature difference of approximately 3°C to 8°C can be formed, thereby further amplifying the difference in aging rates.

[0027] In another embodiment, the relationship between initial brightness and long-term degradation is controlled by differences in the light extraction structure. Specifically, microstructures of different sizes or morphologies are introduced into the light-emitting surface of the sub-pixels. For example, the diameter of the microlens varies in the range of 3–8 μm, or the surface roughening depth varies in the range of 50–200 nm, so that the initial light extraction efficiency of different sub-pixels differs by approximately 10%–30%. This difference is compensated for in the initial stage, but it affects the long-term aging curve.

[0028] In terms of manufacturing process, the above-mentioned structural differences are achieved through standard MicroLED processes, including: photolithography to define pixel size (CD control accuracy ±0.2μm), ICP etching to form the mesa structure, ITO sputtering deposition (power 100-250W, thickness control accuracy ±10nm), and spin coating or ALD deposition of the encapsulation layer. All differences are completed during the manufacturing stage, forming irreversible structural features.

[0029] Regarding the aging mechanism, the current density of different sub-pixels ( J ), operating temperature ( T The aging rate and defect evolution rate satisfy an empirical relationship: α ∝ J m ·exp( E a / kT ), where ∝ is the proportional sign, m The current acceleration index, m ≈1~2; E a To activate energy; k This represents the Boltzmann constant. Through the aforementioned structural differences, the aging rate of different sub-pixels is adjusted. α The value is preset within the target range, such as blue light. α ≈0.5% / 100h, green lightα ≈0.3% / 100h, red light α ≈0.2% / 100h.

[0030] Based on accelerated aging test (current density 30-80 A / cm²) 2 During a test period of 500 to 1000 hours (temperature 60℃~100℃), it was observed that the RGB brightness decay difference was about 20% to 35% when the method was not used; after using the structural difference preset method, the brightness difference at the end of the life (e.g., 10,000 hours equivalent) was reduced to about 5% to 10%.

[0031] In practical applications, this method can be used in conjunction with initial current correction. Specifically, during the display module manufacturing process, demura or one-time current correction is used to control the initial brightness error of different sub-pixels within the range of ±2% to ±5%. During subsequent use, the aging trajectory of each sub-pixel is determined by its structural differences, thereby causing the brightness-time curve to gradually converge within the target lifespan range.

[0032] By employing the differentiated design methods described above, which have clear structural parameters, material systems, and process paths, pre-engineering control of sub-pixel aging behavior is achieved, thereby improving the long-term consistency and stability of full-color MicroLED displays without the need for complex runtime compensation.

[0033] Example 2 This invention provides a MicroLED sub-pixel aging slope preset structure, including a CMOS backplane 1. A pixel driving circuit is integrated on the CMOS backplane 1, and an anode electrode 11 and a cathode electrode 12 are formed for electrical connection. A MicroLED light-emitting structure 2 is disposed above the CMOS backplane 1. The MicroLED light-emitting structure 2 includes an n-type semiconductor layer 21, a light-emitting layer 22, and a p-type semiconductor layer 23 stacked sequentially. The p-type semiconductor layer 23 is electrically connected to the anode electrode 11 through a p-type contact electrode layer 24, thereby realizing the electrical connection between the MicroLED pixel and the CMOS backplane driving circuit. An n-type transparent electrode layer 3 is formed on the n-type semiconductor layer 21. The n-type transparent electrode layer 3 extends laterally above the cathode electrode 12 in the CMOS backplane 1 and is electrically connected to it through a filler metal electrode, used to realize the lateral expansion of the current inside the pixel and as part of the light emission interface.

[0034] Multiple sub-pixel structures 2a, 2b, and 2c are set within the same pixel unit. Each sub-pixel corresponds to a different color or different functional light-emitting unit and is independently electrically connected to the driving circuit in the CMOS backplane 1. Based on the above overall structure, the physical structural parameters of different sub-pixels are irreversibly differentiated, so that each sub-pixel forms different current densities, operating temperatures, and light extraction efficiencies under the same driving conditions, thereby achieving the preset aging rate.

[0035] Specifically, such as Figure 1 As shown, in one embodiment, current density differential control is achieved by differentiating the effective light-emitting area of ​​the sub-pixels. The MicroLED light-emitting structure 2 forms mesa regions of different sizes during pixel definition. The light-emitting areas of different sub-pixels 2a, 2b, and 2c are set within the range of 6μm×6μm to 10μm×10μm, so that under the same driving current conditions, each sub-pixel forms a different equivalent current density distribution, thereby having a differential impact on its defect evolution rate and aging behavior.

[0036] like Figure 2 As shown, in another embodiment, by differentiating the structural parameters of the n-type transparent electrode layer 3, the current spreading capability of different sub-pixels is made different. Specifically, transparent electrode layers 3a, 3b, and 3c with different thicknesses or different resistance characteristics are set in different sub-pixel regions, so that the uniformity of current distribution inside the pixel changes, thereby further controlling the local current density peak and its corresponding aging rate.

[0037] like Figure 3 As shown, in a further embodiment, by introducing different thermal path structures 4 between the MicroLED light-emitting structure 2 and the CMOS backplane 1 or in the packaging area above the MicroLED, different sub-pixel regions have different interface thermal resistances 4a, 4b, and 4c, thereby forming different steady-state or transient operating temperatures under the same operating conditions. The thermal path structure 4 forms a thermal conduction connection with the MicroLED light-emitting structure 2 and the CMOS backplane 1, and participates in the conduction and diffusion process of pixel heat.

[0038] In addition, such as Figure 4 As shown, a light extraction structure 5 can also be set above the n-type transparent electrode layer 3. The light extraction structure 5 has different geometric dimensions or morphological parameters 5a, 5b, and 5c in different sub-pixel regions, so that different sub-pixels have different light extraction efficiencies in the initial stage and modulate their light attenuation behavior during long-term operation.

[0039] The aforementioned differences in luminescent area, current spread, thermal path, and light extraction structure affect the current path, heat conduction path, and light emission path of the MicroLED pixel, respectively. These differences, along with the CMOS backplane 1, its electrode structure, and the MicroLED luminescent structure 2, form an integrated structure, causing different sub-pixels to exhibit different current densities J, operating temperatures T, and light extraction efficiencies under the same driving conditions, thus ensuring their aging rate meets the requirements. α ∝ J m ·exp( E a / kT ) relationship.

[0040] By pre-setting the aforementioned structural parameters during the device design and manufacturing stages, the aging slope of different sub-pixels can be pre-defined within a target range, thereby ensuring that during the use of the display device, such as... Figure 5 As shown, the brightness-time variation curves of each sub-pixel gradually converge, achieving natural convergence of brightness and chromaticity. This significantly improves the long-term consistency and stability of full-color MicroLED displays without requiring complex runtime current compensation or algorithm correction.

[0041] Example 3 By differentiating the effective light-emitting area of ​​sub-pixels, the aging slope of MicroLED RGB sub-pixels can be preset and controlled. In this embodiment, during the pixel definition process, the mesa size of different color sub-pixels is quantitatively set through photolithography and etching processes, thereby forming different equivalent current densities under the same driving current conditions, and thus regulating their aging rate.

[0042] Specifically, within the same pixel unit, red, green, and blue sub-pixels employ different luminous area designs. Taking a MicroLED array with a pixel pitch of 4–8 μm as an example, the mesa size of the blue sub-pixel is designed to be approximately 5.5 μm × 5.5 μm (effective luminous area approximately 30 μm). 2 The green photonic pixels are approximately 6.5μm × 6.5μm (approximately 42μm). 2 The red photon sub-pixel is approximately 7.5μm × 7.5μm (approximately 56μm). 2 The area difference between each sub-pixel is approximately 30% to 80%.

[0043] Regarding driving conditions, a uniform constant current driving method is adopted, with the driving current for each sub-pixel set to 10–20 μA. Under these conditions, the corresponding equivalent current densities are approximately 330–660 A / cm² for blue sub-pixels. 2 Green photonic pixels 240–480 A / cm 2Red photon sub-pixels 180–360 A / cm 2 This results in a current density distribution with the highest blue light and the lowest red light.

[0044] The aforementioned mesa structure is achieved using standard MicroLED processes: first, different sub-pixel patterns are defined using photolithography (CD control accuracy ±0.2μm); then, ICP dry etching is used to form the mesa (etching depth approximately 0.5–1.5μm); and sidewall passivation (such as ALDAl2O3, thickness 10–30nm) is used to reduce sidewall recombination. This differentiated dimension remains fixed after manufacturing and does not participate in subsequent dynamic adjustments.

[0045] In terms of aging mechanism, since current density is closely related to carrier injection and thermal effects, it has a significant impact on defect generation and quantum efficiency decay. Under the same ambient temperature (e.g., 60℃) and continuous operating conditions, blue sub-pixels exhibit a faster brightness decay rate due to their higher current density, while red sub-pixels have a relatively slower aging rate due to their lower current density.

[0046] Accelerated aging test (current density 40-80 A / cm²) was conducted. 2 Under equivalent conditions (test duration 500–1000 hours), the brightness decay slopes of different sub-pixels were measured to be approximately: blue light 0.45%–0.60% / 100h, green light 0.30%–0.40% / 100h, and red light 0.20%–0.30% / 100h. Compared to the control sample without area difference design (RGB aging difference approximately 25%–35%), the brightness difference of RGB sub-pixels at the equivalent 10,000-hour lifetime point in this embodiment was reduced to approximately 6%–10%.

[0047] Furthermore, in the initial stage, a one-time current correction (demura) is used to correct the initial brightness differences (approximately 10%–25%) caused by different areas to within ±3%–±5%. During subsequent use, since the aging slope has been preset, the brightness of different sub-pixels gradually converges over time, thereby achieving long-term brightness and color consistency.

[0048] Through the structural design and process implementation based on the difference in light-emitting area, the aging behavior of sub-pixels can be pre-controlled without dynamic compensation during operation, thereby significantly improving the long-term stability and consistency of full-color MicroLED display devices.

[0049] Example 4 By differentiating the thermal path structure of sub-pixels, the aging slope of sub-pixels can be preset and controlled. Specifically, structural units with different thermal resistances or thermal conductivity are introduced in the interface area between the MicroLED light-emitting structure and the backplane, as well as in the light-emitting side encapsulation area, so that different sub-pixels can form different steady-state operating temperatures under the same driving conditions.

[0050] In terms of specific structural implementation, different thermal resistance paths are constructed in the blue, green, and red sub-pixel regions. Differential thermal resistance is achieved at the bottom of the pixel (the interface between the MicroLED and the backplane) by adjusting the bonding layer material and thickness. For example, the blue sub-pixel region uses an interface layer with low thermal conductivity (such as SiO2 or a low thermal conductivity polymer) with a thickness of 200–500 nm, corresponding to an interface thermal resistance of approximately 2 × 10⁻⁶. -7 ~5×10 -7 m 2 • K / W; The green photonic pixel region uses a medium thermal conductivity material (such as Al2O3) with a thickness of 100–300 nm, corresponding to an interfacial thermal resistance of approximately 1 × 10⁻⁶. -7 ~3×10 -7 m 2 • K / W; The red photonic pixel region uses a material with high thermal conductivity (such as AlN or a highly dense oxide layer) with a thickness of 50–150 nm, corresponding to an interfacial thermal resistance of approximately 0.5 × 10⁻⁶. -7 ~2×10 -7 m 2 ·K / W.

[0051] In the light-emitting side encapsulation region, the heat diffusion path is further adjusted by setting encapsulation layers with different thermal conductivity. For example, an encapsulation layer with low thermal conductivity (k≈0.5~1W / m·K, thickness 2~4μm) is set above the blue sub-pixel, while an inorganic encapsulation layer with high thermal conductivity (k≈3~8W / m·K, thickness 1~3μm) is used in the red light region, thereby further creating a difference in the heat path in the vertical direction.

[0052] The above structure is achieved through standard processes: the interface layer is deposited by ALD or sputtering (thickness control accuracy ±10nm), the encapsulation layer is formed by spin coating or PECVD (thickness control accuracy ±0.2μm), and the differentiated structure of the RGB sub-pixel region is defined by photolithography partitioning process.

[0053] Under typical operating conditions (current density 20–50 A / cm²) 2 The corresponding power density is approximately 10–30 W / cm². 2 The steady-state temperature differences of different sub-pixels were obtained through finite element thermal simulation: the blue light sub-pixel is about 85℃~95℃, the green light is about 75℃~85℃, and the red light is about 65℃~75℃, with a temperature difference of about 5℃~20℃ between them.

[0054] According to the empirical model of MicroLED aging, the aging rate and temperature satisfy an exponential relationship (…). α ∝exp( E a / kT ), E a (≈0.6~0.8eV). Within the above temperature range, the aging rate of blue sub-pixels can be increased by about 1.5 to 2.5 times compared with red light, thereby enabling the preset aging slope of different sub-pixels.

[0055] In accelerated aging tests (temperature 85℃, current density 40A / cm²), 2 In samples without thermal path difference design (test time 500h), the difference in RGB three-color brightness attenuation is about 25% to 35%; after adopting this implementation method, the difference in three-color brightness attenuation is reduced to about 8% to 12%, and tends to be consistent under the condition of equivalent service life (>10,000h).

[0056] Furthermore, infrared thermal imaging verification showed that the temperature distribution between different sub-pixels after adopting this structure met the design expectations, the temperature difference was stable and controllable, and no obvious local hot spots or thermal runaway phenomena were introduced.

[0057] Through the above-mentioned structural design based on thermal path differences, the operating temperature and aging rate of sub-pixels can be pre-set during the manufacturing stage, so that they form a predetermined brightness decay trajectory during long-term use, thereby reducing the dependence on dynamic current compensation in the later stage and improving the long-term stability and consistency of the display system.

[0058] Example 5 By designing differentiated light extraction structures for sub-pixels, the aging slope can be preset based on differences in optical light extraction efficiency. Specifically, light extraction structures with different parameters are constructed on the light-emitting surface of MicroLED sub-pixels, so that each sub-pixel has different light extraction efficiencies in the initial stage. This results in different current and thermal loads under uniform brightness correction conditions, thereby achieving preset control of the aging rate.

[0059] In terms of specific structure, a micro-nano composite light extraction structure is formed on the light-emitting surface of the MicroLED, including a combination of a surface roughening layer and a microlens structure. Surface roughening is achieved by ICP dry etching, with Cl2 / BCl3 as the etching gas, a power of 200-400W, and an etching time of 30-90s, forming a microstructure with a roughening depth of 50-200nm and a feature size of 100-500nm; the microlens are formed by photoresist reflow or nanoimprinting, with a diameter of 3-8μm and a height of 0.5-2μm.

[0060] For different color sub-pixels, taking into account the characteristic that red light has a relatively fast aging rate (typically about -0.4% / ℃ corresponding to a long-term aging rate of about 0.4% to 0.6% / 100h), a reverse compensation design is performed on the light extraction structure: An enhanced light extraction structure is employed in the red photon pixel region, with a coarsening depth of 120–180 nm and a microlens height of 1.2–1.8 μm, thereby improving its light extraction efficiency to approximately 65%–75%. A medium-light extraction structure is used in the green photonic pixel region, with a coarsening depth of 80–120 nm and a microlens height of 0.8–1.2 μm, corresponding to an extraction efficiency of approximately 55%–65%. A weak light extraction structure is used in the blue photon sub-pixel region, with a coarsening depth of 50–80 nm and a microlens height of 0.5–0.8 μm, corresponding to an extraction efficiency of approximately 45%–55%.

[0061] Through the aforementioned differentiated design, under the same driving current conditions, the initial brightness of different sub-pixels varies by approximately 15% to 30%. In practical applications, demura or one-time current correction is used to unify the brightness of RGB sub-pixels to the target value.

[0062] After brightness is unified, the driving current required to achieve the same brightness is reduced by about 15% to 30% due to the higher light extraction efficiency of red sub-pixels, and the equivalent current density is reduced by about 20% to 35%; while the driving current required for blue sub-pixels is increased by about 10% to 25% due to the lower light extraction efficiency.

[0063] According to the MicroLED aging model (aging rate α∝J^m, m≈1~2), this difference in current density can reduce the aging rate of red sub-pixels by about 25%~50%, thereby compensating for their inherently faster aging trend; at the same time, the aging rate of blue sub-pixels is moderately increased, making the aging trajectories of the three colors more consistent.

[0064] In addition, the improved light extraction efficiency also reduces the ratio of photon back absorption and non-radiative recombination in red photonic pixels, thereby reducing the local temperature rise by about 2°C to 6°C and further reducing the thermally accelerated aging effect.

[0065] Based on the simulation results of optical-electrical-thermal coupling, within the above structural parameter range, the following aging slope matching can be achieved: red light approximately 0.25%~0.35% / 100h, green light approximately 0.25%~0.30% / 100h, and blue light approximately 0.25%~0.35% / 100h, so that the aging rate of the three color sub-pixels tends to be consistent.

[0066] In experimental verification, the current density was 20–50 A / cm². 2An 800-hour accelerated aging test was conducted at an ambient temperature of 60℃. The results showed that without this structure, the RGB brightness difference increased to about 25% to 35%. After adopting this differentiated light extraction structure, the final brightness difference was reduced to about 6% to 10%, and the overall color shift was reduced by about 40% to 60%.

[0067] The aforementioned light extraction structure is achieved through standard MicroLED processes, including ICP roughening etching, photolithography to define microlenses, and thermal reflow or imprinting. The structural parameters are determined once during the manufacturing stage and cannot be changed during use, thereby ensuring the determinism and predictability of the aging slope.

[0068] By implementing a reverse compensation design targeting the faster aging characteristics of red photonic pixels, an aging slope preset based on light extraction efficiency is achieved, enabling the brightness and chromaticity of full-color MicroLED pixels to gradually converge during long-term use, thereby improving display consistency and lifespan stability.

[0069] Example 6 This method combines a pre-set aging slope based on pixel structure differences with an initial current correction approach and applies it to full-color MicroLED display modules. After manufacturing, the initial brightness of different sub-pixels is aligned through a one-time or low-frequency current correction. During subsequent use, the aging behavior of each sub-pixel is mainly determined by its pre-set structural differences, thereby achieving long-term consistency convergence of brightness and color.

[0070] Specifically, in the MicroLED pixel design stage, considering the relatively fast aging rate of red sub-pixels (typical aging rate of about 0.4% to 0.6% / 100h, higher than that of blue light (about 0.3% to 0.5% / 100h) and green light (about 0.2% to 0.4% / 100h), the structural parameters of red sub-pixels are pre-compensated to give them relatively low working stress or high initial brightness margin in the initial stage.

[0071] In one specific implementation, the emission area and current density are differentiated and controlled. The red sub-pixel is designed with a larger emission area (e.g., 8μm×8μm~10μm×10μm), the blue sub-pixel with 6μm×6μm~7μm×7μm, and the green sub-pixel with 7μm×7μm~8μm×8μm. Under the same driving current (e.g., 10~30μA), the equivalent current density of the red sub-pixel is reduced to approximately 80~200A / cm². 2 The blue sub-pixels remain at approximately 150–400 A / cm. 2 This structurally slows down the red light aging rate.

[0072] In another implementation, the local current congestion effect in red light is reduced through electrode and current spreading layer design. For example, a thicker transparent electrode layer (ITO thickness 150-200nm) is used for red sub-pixels, while a thinner electrode layer (80-120nm) is used for blue sub-pixels, making the current distribution in the red light region more uniform and reducing local hot spots.

[0073] After completing the aforementioned structural design differences, initial current calibration is performed during the module's factory manufacturing phase. Specifically, using demura or current lookup table (LUT) calibration methods, the driving current of each sub-pixel is adjusted once at an ambient temperature of 25°C to control the initial brightness error within the range of ±2% to ±5%. This calibration process typically involves fine-tuning the driving current within the range of 5 to 30 μA, with a preferred calibration step accuracy of 0.1 to 0.5 μA.

[0074] After calibration, each sub-pixel enters normal operation under the same target brightness. Since the red sub-pixel is designed with lower current density and lower thermal stress, its actual aging rate is reduced from the original approximately 0.5% / 100h to approximately 0.3%~0.4% / 100h, thus approaching or matching the aging rate of the blue and green sub-pixels.

[0075] Based on accelerated aging test (driving current density 30-60 A / cm²) 2 During a 500-hour test period (at an ambient temperature of 60℃~85℃), it was observed that without this method, the brightness attenuation difference of RGB subpixels was approximately 20%~30%; after adopting this structural difference + initial correction method, the attenuation difference was reduced to approximately 8%~12%. Extrapolating to an equivalent lifetime of 10,000 hours, the brightness difference of the three colors was controlled within the range of approximately 5%~10%.

[0076] Furthermore, since the initial calibration is only performed once at the factory stage or at low frequencies (e.g., every 500 to 1000 hours) and does not participate in real-time dynamic compensation, the system does not require a complex real-time feedback control algorithm, reducing the complexity of the drive circuit by about 20% to 30%, while avoiding additional power consumption and noise problems caused by frequent current regulation.

[0077] By combining the above-mentioned implementation method of pre-setting structural differences with initial current correction, the problem of rapid red light aging is effectively suppressed without relying on dynamic compensation during operation, so that the full-color MicroLED display can maintain good brightness and color consistency throughout its entire service life.

Claims

1. A MicroLED sub-pixel aging slope preset structure, characterized in that, The system includes a full-color MicroLED light-emitting structure (2) disposed on a CMOS backplane (1). Each sub-pixel of the full-color MicroLED light-emitting structure (2) is independently electrically connected to the driving circuit in the CMOS backplane (1). Each sub-pixel is provided with a control structure that presets its aging slope. The control structure has irreversible structural parameter differences between different sub-pixels.

2. The MicroLED sub-pixel aging slope preset structure as described in claim 1, characterized in that, The control structure includes light-emitting areas of different sizes among different sub-pixels, and the light-emitting area is the mesa region area of ​​the MicroLED light-emitting structure (2).

3. The MicroLED sub-pixel aging slope preset structure as described in claim 2, characterized in that, The different sizes of light-emitting areas satisfy the following: in the same pixel unit, the light-emitting area of ​​the blue sub-pixel is the smallest, the light-emitting area of ​​the red sub-pixel is the largest, and the difference in light-emitting area between sub-pixels of different colors is 30% to 80%.

4. The MicroLED sub-pixel aging slope preset structure as described in claim 1, characterized in that, The control structure includes current spreading layers with different thicknesses between different sub-pixels, and the current spreading layer is an n-type transparent electrode layer (3) disposed above the MicroLED light-emitting structure (2).

5. The MicroLED sub-pixel aging slope preset structure as described in claim 4, characterized in that, Among the current spreading layers of different thicknesses, the thickness of the n-type transparent electrode layer (3) of the blue photonic sub-pixel is less than the thickness of the n-type transparent electrode layer (3) of the red photonic sub-pixel.

6. The MicroLED sub-pixel aging slope preset structure as described in claim 1, characterized in that, The control structure includes a thermal path structure (4) with different interface thermal resistance between different sub-pixels. The thermal path structure (4) is disposed between the MicroLED light-emitting structure (2) and the CMOS backplane (1) or in the encapsulation layer above the MicroLED light-emitting structure (2).

7. The MicroLED sub-pixel aging slope preset structure as described in claim 6, characterized in that, In the thermal path structures (4) with different interface thermal resistances, the interface thermal resistance of the thermal path structure in the blue sub-pixel region is higher than that in the red sub-pixel region.

8. The MicroLED sub-pixel aging slope preset structure as described in claim 1, characterized in that, The control structure includes light extraction structures (5) with different geometric dimensions between different sub-pixels, and the light extraction structures (5) are disposed on the light-emitting surface of the MicroLED light-emitting structure (2).

9. The MicroLED sub-pixel aging slope preset structure as described in claim 8, characterized in that, The light extraction structure (5) includes a surface roughening layer and a microlens structure. In the light extraction structures (5) with different geometric sizes, the surface roughening depth of the red photon sub-pixel light extraction structure is 120-180 nm and the microlens height is 1.2-1.8 μm; the surface roughening depth of the blue photon sub-pixel light extraction structure is 50-80 nm and the microlens height is 0.5-0.8 μm.

10. A method for presetting the aging slope of a MicroLED sub-pixel, characterized in that, In the MicroLED pixel design and manufacturing stage, for different sub-pixels within the same pixel unit, at least one physical structural parameter is irreversibly differentiated. The differentiated physical structural parameters include the light-emitting area of ​​the sub-pixel, the thickness of the current spreading layer, the interface thermal resistance of the thermal path, or the geometric dimensions of the light extraction structure. Through differentiated settings, different sub-pixels can form different current densities, operating temperatures, or initial light extraction efficiencies under the same driving conditions, thereby presetting the aging slope of each sub-pixel.

Images