A work function tunable microdisplay structure and its fabrication process

Abstract

This invention discloses a work function-tunable microdisplay structure, comprising a silicon substrate, a driving circuit substrate 2, and an anode. The driving circuit substrate is fabricated within the silicon substrate, and the anode is fabricated on the silicon substrate above the driving circuit substrate. The anode includes an R-pixel anode, a G-pixel anode, and a B-pixel anode. Each of the R-pixel anode, G-pixel anode, and B-pixel anode includes: an adhesive layer, a reflective layer, a diffusion barrier layer, and a work function adjustment layer. Electrons or holes are injected into the work function adjustment layers of the three RGB pixel anodes to improve the anode carrier mobility. Simultaneously, the work function (4.5-8 eV) and refractive index of the RGB anodes are independently adjusted to match different RGB light-emitting material requirements, adjust the microcavity effect, and achieve independent adjustment of the RGB pixel spectrum. This improves efficiency and color gamut, solving the problems of unadjustable RGB pixel light emission, low efficiency, and low color gamut in traditional Micro OLED white light + CF solutions. This invention also discloses a fabrication process for the work function-tunable microdisplay structure.

Description

Technical Field

[0001] This invention belongs to the field of microdisplay technology, specifically relating to a work function adjustable microdisplay structure and its fabrication process. Background Technology

[0002] With the development of the near-eye display market, including virtual reality (VR), augmented reality (AR), and mixed reality (MR), microdisplay technology is also advancing, including Micro OLED, Micro LED, high-resolution LCD, liquid crystal on silicon (LCOS), and digital light processing (DLP). Compared with other microdisplay technologies, organic light-emitting diode microdisplays (Micro OLED) are highly competitive in the near-eye display field due to their advantages such as high resolution, high color gamut, high contrast, high refresh rate, low power consumption, low heat generation, simple structure, small size, and good portability.

[0003] Currently, due to limitations in evaporation masks and processes, Micro OLEDs primarily use an open-mask evaporation method for white OLEDs, followed by colorization using color filters (CF). If the anode uses the same material or structure, the emission spectra of the three RGB pixels will be the same, such as... Figure 3 As shown, the RGB pixel spectrum cannot be independently adjusted, and the other two colors of light must be filtered out, resulting in poor light utilization efficiency and a low color gamut. The driving voltage of an OLED depends on the injection barriers at the anode and cathode, as well as the mobility of positively charged carriers in the device. The hole injection barrier is determined by the energy difference between the work function of the anode and the HOMO level of the organic functional material; the electron injection barrier is determined by the energy difference between the work function of the cathode and the LUMO level of the organic functional material. If the work functions do not match, it will lead to high driving voltage, high heat generation, and easy device aging. OLED anode materials require good conductivity, a high work function, matching the HOMO energy level of the hole injection material, good chemical and morphological stability, and good light transmittance in the visible light region. The most commonly used material is ITO, with a work function of 4.5–4.8 eV. It cannot match well with the HOMO of organic materials, resulting in a large hole injection barrier. Therefore, a hole injection layer is needed to reduce the barrier. WOLEDs with open masks use the same material for RGB, making it impossible to distinguish between RGB and achieve independent control of RGB. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a work function-tunable microdisplay structure and its fabrication process. By developing separate ion implantation processes for the three RGB pixels, electrons or holes are implanted into the anode work function adjustment layer of the RGB sub-pixels to improve the anode carrier mobility. Simultaneously, the RGB anode work function (4.5-8 eV) and refractive index are independently adjusted to match different RGB light-emitting material requirements, adjust the microcavity effect, and achieve independent spectral adjustment of RGB pixels, thereby improving efficiency and color gamut.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: a microdisplay structure with adjustable work function, comprising a silicon substrate, a driving circuit substrate, and an anode. The driving circuit substrate is fabricated in the silicon substrate, and the anode is fabricated on the silicon substrate above the driving circuit substrate. The anode includes an R-pixel anode, a G-pixel anode, and a B-pixel anode. Each of the R-pixel anode, G-pixel anode, and B-pixel anode includes: an adhesive layer, a reflective layer, a diffusion barrier layer, and a work function adjustment layer. Electrons or holes are implanted into the work function adjustment layers of the three RGB pixel anodes, respectively.

[0006] Furthermore, in the R pixel anode, the work function adjustment layer injects electrons or holes with an energy of 100-200 keV and a dose of 1E15-1E20; in the G pixel anode, the work function adjustment layer injects electrons or holes with an energy of 50-150 keV and a dose of 1E12-1E18; in the B pixel anode, the work function adjustment layer injects electrons or holes with an energy of 80-100 keV and a dose of 1E14-1E15; the injected electrons can be selected from phosphorus, arsenic, or antimony, and the injected holes can be selected from boron, gallium, or indium.

[0007] Furthermore, the adhesive layer, reflective layer, diffusion barrier layer, and work function adjustment layer are sequentially arranged from bottom to top. The thickness of the adhesive layer is 10-1000 Å, and the material used is Ti, Ta, TiN, or TaN; the thickness of the reflective layer is 500-5000 Å, and the material used is Al or Ag high-reflectivity material; the thickness of the diffusion barrier layer is 10-200 Å, and the material used is Ti, Ta, TiN, or TaN; the thickness of the work function adjustment layer is 100-5000 Å, and the material used is ITO, ITO, IGZO, IZO, ZnO, or AZO.

[0008] Furthermore, the microdisplay structure also includes a pixel definition layer. Pixel definition layers are provided at both ends of the anode, and pixel definition layers are provided between the R pixel anode and the G pixel anode, and between the G pixel anode and the B pixel anode. The pixel definition layer has a T-shaped structure. The bottom of the pixel definition layer is flush with the bottom of the anode and is in contact with the silicon substrate. The top of the pixel definition layer is higher than the top of the anode.

[0009] Furthermore, the microdisplay structure also includes an organic light-emitting layer, a cathode, and an encapsulation layer. The organic light-emitting layer and the cathode are disposed above the pixel definition layer and the R pixel anode, G pixel anode, and B pixel anode. The encapsulation layer is disposed above the organic light-emitting layer and the cathode. The bottom of the encapsulation layer has a groove for wrapping the protrusions of the organic light-emitting layer and the cathode. The bottom of the encapsulation layer and the top of the organic light-emitting layer and the cathode are interlocked.

[0010] Furthermore, the microdisplay structure also includes a CF layer and a protective layer. CF layers are respectively disposed on the encapsulation layer at positions corresponding to the R pixel anode, G pixel anode, and B pixel anode. Protective layers are disposed on the encapsulation layer and the CF layer. The bottom of the protective layer (8) and the CF layer are interlocked.

[0011] Based on the above-mentioned work function tunable microdisplay structure, the present invention also relates to a fabrication process for a work function tunable microdisplay structure, the fabrication process comprising the following steps:

[0012] Step 1: Fabricate the driving circuit wafer, and fabricate the circuit required to drive the OLED on the silicon substrate;

[0013] Step 2: Anodic deposition using a four-layer structure, from bottom to top: 1. Bonding layer (10-1000 Å), selectable from Ti, Ta, TiN, or TaN; 2. Reflective layer (500-5000 Å), selectable from Al or Ag high-reflectivity materials; 3. Diffusion barrier layer (10-200 Å), selectable from Ti, Ta, TiN, or TaN; 4. Work function adjustment layer (100-5000 Å), selectable from ITO, ITO, IGZO, IZO, ZnO, or AZO.

[0014] Step 3: Use a mask to block the areas where the R, G, and B pixels are located, and then perform anodizing.

[0015] Step 4: Anodic etching and resist removal to form R-pixel anode, G-pixel anode, and B-pixel anode;

[0016] Step 5: R-pixel photolithography, using a mask to block the G-pixel anode and B-pixel anode, and performing photolithography on the R-pixel anode;

[0017] Step 6: R-pixel ion implantation. Electrons (phosphorus, arsenic, antimony) or holes (boron, gallium, indium) are implanted into the work function adjustment layer in the R-pixel anode using an ion implantation process. The implantation conditions are: energy 100-200 keV, dose 1E15-1E20, and adjustment of the R-pixel anode work function (4.5-8 eV) and refractive index.

[0018] Step 7: Remove the photoresist. Use wet or dry processes to remove the photoresist and remove the mask on the G pixel anode and B pixel anode.

[0019] Step 8: G-pixel photolithography, using a mask to block the R-pixel and B-pixel anodes, and performing photolithography on the G-pixel anode;

[0020] Step 9: G-pixel ion implantation. Electrons (phosphorus, arsenic, antimony) or holes (boron, gallium, indium) are implanted into the work function adjustment layer in the G-pixel anode using an ion implantation process. The implantation conditions are: energy 50-150 keV, dose 1E12-1E18, and adjustment of the G-pixel anode work function (4.5-8 eV) and refractive index.

[0021] Step 10: Remove the photoresist. Use a wet or dry process to remove the photoresist and remove the mask on the anode of the R and B pixels.

[0022] Step 11: B-pixel photolithography, using a mask to block the R and G pixels, and performing photolithography on the B-pixel anode;

[0023] Step 12: B-pixel ion implantation. Electrons (phosphorus, arsenic, antimony) or holes (boron, gallium, indium) are implanted into the work function adjustment layer in the B-pixel anode using an ion implantation process. The implantation conditions are: energy 10-100 keV, dose 1E5-1E15, and adjustment of the B-pixel anode work function (4.5-8 eV) and refractive index.

[0024] Step 13: Photoresist removal and annealing. Remove the photoresist using wet or dry processes to remove the mask on the R and G pixels; annealing to activate the ions implanted into the work function adjustment layer.

[0025] Step 14: Pixel definition layer fabrication. Organic or inorganic materials can be selected. Organic materials include polyimide photoresist, which is prepared using pixel definition layer coating, exposure, development, and high-temperature curing processes. Inorganic materials include silicon oxide, silicon nitride, silicon oxynitride, etc., which are prepared through pixel definition layer deposition, photolithography, etching, and lift-off processes.

[0026] Step 15: Evaporation / Encapsulation, evaporation of organic layers such as hole injection layer, hole transport layer, light-emitting layer, electron transport layer, and electron injection layer, and cathode, thin film deposition of oxide, silicon nitride, silicon oxynitride, aluminum oxide, etc. to complete encapsulation;

[0027] Step 16: Prepare the CF layer and protective layer by means of coating, exposure, development and curing processes.

[0028] Furthermore, step 6: R-pixel ion implantation:

[0029] 1) When using Ir(piq)3 as the red light material, Ir(piq)3 has the highest occupied molecular orbital HOMO = 5.1 eV and the lowest unoccupied molecular orbital LUMO = 3.1 eV. The implantation material can be BF3, B2H6, arsenic, antimony, gallium or indium. The implantation conditions are: energy 100-200 keV, dose 1E15-1E20.

[0030] 2) When DCJTB is used as the red light material, the highest occupied molecular orbital HOMO of DCJTB is 5.4 eV and the lowest unoccupied molecular orbital LUMO is 3.2 eV, which is higher than Ir(piq)3. The implantation material can be BF3, B2H6, arsenic, antimony, gallium or indium. The implantation conditions are: 150-200 keV, dose 1E18-1E20.

[0031] Furthermore, step 9: G-pixel ion implantation:

[0032] 1) When Alq3 is used as the green light material, the highest occupied molecular orbital HOMO of Alq3 is 5.62 eV and the lowest unoccupied molecular orbital LUMO is 2.85 eV. The implantation material is selected from phosphorus, arsenic or gallium. The implantation conditions are: energy 50-150 keV, dose 1E12-1E18.

[0033] 2) When using Ir(piq)2(acac) as the green light material, the highest occupied molecular orbital HOMO of Ir(piq)2(acac) is 5.0 eV and the lowest unoccupied orbital LUMO is 3.0 eV, which is lower than Alq3. The implantation material can be phosphorus, arsenic or gallium. The implantation conditions are: energy 50-100 keV, dose 1E12-1E15.

[0034] Furthermore, in step 12: B-pixel ion implantation:

[0035] 1) When using AND and FirPic as blue light materials, the highest occupied molecular orbital (HOMO) of AND is 5.8 eV and the lowest unoccupied molecular orbital (LUMO) is 2.6 eV; the highest occupied molecular orbital (HOMO) of FirPic is 5.8 eV and the LUMO is 3.1 eV; the implantation material can be boron or phosphorus, and the implantation conditions are: energy 10-100 keV, dose 1E5-1E15;

[0036] 2) When using Fir6 as the blue light material, Fir6 has the highest occupied molecular orbital HOMO = 6.10 eV and the lowest unoccupied molecular orbital LUMO = 3.10 eV, which is higher than ADN and FirPic. The implantation material can be boron, phosphorus or gallium. The implantation conditions are: energy 80-100 keV, dose 1E14-1E15.

[0037] The advantages of using the technical solution of this invention are:

[0038] 1. This invention develops a separate ion implantation process for RGB three pixels, which separately implants electrons or holes into the anode work function adjustment layer of the RGB sub-pixels to improve the anode carrier mobility. At the same time, it independently adjusts the RGB anode work function (4.5-8eV) and refractive index to match the requirements of different RGB light-emitting materials, adjusts the microcavity effect, and realizes independent adjustment of the RGB pixel spectrum, thereby improving efficiency and color gamut. This solves the problems of the traditional Micro OLED white light + CF solution, which has the problem of RGB pixel light output being unable to be adjusted, resulting in low efficiency and low color gamut.

[0039] 2. Depending on the requirements of different RGB light-emitting materials, two or three anodes with different work functions can be selected. Ions (phosphorus, arsenic, antimony, etc.) or holes (boron, gallium, indium) are implanted into the work function adjustment layer to adjust the work function and refractive index. The additional implanted electrons and holes also improve carrier mobility, increasing efficiency. Simultaneously, the RGB spectrum is independently adjusted to meet the different needs of different RGB pixels. The improved RGB spectrum is as follows: R pixels enhance red light and weaken blue and green light; G pixels enhance green light and weaken red and blue light; B pixels enhance blue light and weaken red and green light. Attached Figure Description

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0041] Figure 1 This is a flowchart illustrating the fabrication process of the work function-tunable microdisplay structure of the present invention.

[0042] Figure 2 This is a schematic diagram of the work function adjustable microdisplay structure of the present invention;

[0043] Figure 3 This is a normal Micro OLED RGB spectrum.

[0044] Figure 4 The simulated spectrum of R pixels after work function adjustment;

[0045] Figure 5 The simulated spectrum of G pixels after work function adjustment;

[0046] Figure 6 This is the simulated spectrum of pixel B after work function adjustment. Detailed Implementation

[0047] In this invention, it should be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "planar direction," and "circumferential" 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 invention 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 limiting the invention.

[0048] OLED anodes consist of a high work function layer to improve hole injection efficiency and a high reflectivity layer to improve top-emitting device efficiency, typically using a multilayered metal structure. The high work function layer requires: 1. good conductivity; 2. a high work function to match the HOMO energy level of the hole injection material; 3. good chemical and morphological stability; and 4. good light transmittance in the visible light region. Commonly used high work function materials include metal oxides such as ITO (indium tin oxide) and IZO (indium zinc oxide). The high reflectivity layer generally uses metals such as silver or aluminum.

[0049] However, WOLED RGB fabricated with open mask uses the same material, making it impossible to distinguish between RGB and achieve independent control of RGB. If the work function of the RGB anodes can be adjusted separately, the driving voltage of the three RGB pixels can be independently controlled, thereby adjusting the RGB spectrum separately and improving device performance.

[0050] This invention develops a separate ion implantation process for RGB three pixels. Electrons or holes are implanted into the anode work function adjustment layer of each RGB sub-pixel to improve anode carrier mobility. Simultaneously, the work function (4.5-8 eV) and refractive index of the RGB anodes are independently adjusted to match the requirements of different RGB luminescent materials. This adjusts the microcavity effect, enabling independent spectral adjustment of RGB pixels, improving efficiency and color gamut. This solves the problems of traditional Micro OLED white light + CF solutions, such as the inability to adjust RGB pixel light output, low efficiency, and low color gamut. Depending on the requirements of different RGB luminescent materials, two or three anodes with different work functions can be selected. Electrons (phosphorus, arsenic, antimony, etc.) or holes (boron, gallium, indium) are implanted into the work function adjustment layer to adjust the work function and refractive index. The additional injected electrons and holes also improve carrier mobility, increasing efficiency. Simultaneously, the RGB spectrum is independently adjusted to meet the different needs of different RGB pixels. The improved RGB spectrum is shown in the figure: R pixels enhance red light and weaken blue and green light; G pixels enhance green light and weaken red and blue light; B pixels enhance blue light and weaken red and green light.

[0051] The specific implementation method is as follows:

[0052] like Figures 1 to 6 As shown, a microdisplay structure with tunable work function includes a silicon substrate 1, a driving circuit substrate 2, and an anode. The driving circuit substrate 2 is fabricated within the silicon substrate 1, and the anode is fabricated on the silicon substrate 1 above the driving circuit substrate 2. The anode includes an R-pixel anode 3, a G-pixel anode 4, and a B-pixel anode 5. Each of the R-pixel anode, G-pixel anode, and B-pixel anode includes an adhesive layer, a reflective layer, a diffusion barrier layer, and a work function adjustment layer. Electrons or holes are injected into the work function adjustment layers of the three RGB pixel anodes, respectively. By injecting electrons or holes into the work function adjustment layers of the RGB sub-pixel anodes, the anode carrier mobility is improved. Simultaneously, the work function (4.5-8 eV) and refractive index of the RGB anodes are independently adjusted to match the requirements of different RGB light-emitting materials, adjust the microcavity effect, and achieve independent adjustment of the RGB pixel spectrum. This improves efficiency, enhances the color gamut, and solves the problems of unadjustable RGB pixel light emission, low efficiency, and low color gamut in traditional MicroOLED white light + CF solutions.

[0053] In the R-pixel anode, the work function adjustment layer injects electrons or holes with an energy of 100-200 keV and a dose of 1E15-1E20. In the G-pixel anode, the work function adjustment layer injects electrons or holes with an energy of 50-150 keV and a dose of 1E12-1E18. In the B-pixel anode, the work function adjustment layer injects electrons or holes with an energy of 80-100 keV and a dose of 1E14-1E15. The electrons injected into the work function adjustment layer can be selected from phosphorus, arsenic, antimony, etc., and the injected holes can be selected from boron, gallium, indium, etc.

[0054] An adhesive layer, a reflective layer, a diffusion barrier layer, and a work function adjustment layer 11 are arranged sequentially from bottom to top. The thickness of the adhesive layer is 10-1000 Å, and the material used is Ti, Ta, TiN, or TaN. The thickness of the reflective layer is 500-5000 Å, and the material used is Al or Ag high-reflectivity material. The thickness of the diffusion barrier layer is 10-200 Å, and the material used is Ti, Ta, TiN, or TaN. The thickness of the work function adjustment layer is 100-5000 Å, and the material used is ITO, ITO, IGZO, IZO, ZnO, or AZO.

[0055] The microdisplay structure also includes a pixel definition layer 6. Pixel definition layers 6 are provided at both ends of the anode, and are provided between the R pixel anode and the G pixel anode, and between the G pixel anode and the B pixel anode. The pixel definition layer 6 has a T-shaped structure. The bottom of the pixel definition layer 6 is flush with the bottom of the anode and is in contact with the silicon substrate 1. The top of the pixel definition layer 6 is higher than the top of the anode.

[0056] The microdisplay structure also includes an organic light-emitting layer and a cathode 7 and an encapsulation layer 8. The organic light-emitting layer and cathode 7 are disposed above the pixel definition layer 6 and the R pixel anode 3, G pixel anode 4, and B pixel anode 5. The encapsulation layer 8 is disposed above the organic light-emitting layer and cathode 7. The bottom of the encapsulation layer 8 is provided with a groove for wrapping the protrusions of the organic light-emitting layer and cathode 7. The bottom of the encapsulation layer 8 and the top of the organic light-emitting layer and cathode 7 are interlocked.

[0057] The microdisplay structure also includes a CF layer 9 and a protective layer 10. The CF layer 9 is disposed on the encapsulation layer 8 at positions corresponding to the R pixel anode 3, G pixel anode 4, and B pixel anode 5, respectively. The protective layer 10 is disposed on the encapsulation layer 8 and the CF layer 9, and the bottom of the protective layer 10 and the CF layer 9 are interlocked.

[0058] Based on the above-described work function tunable microdisplay structure, this invention also relates to a fabrication process for the work function tunable microdisplay structure.

[0059] The preparation process includes the following steps:

[0060] Step 1: Fabricate the driving circuit wafer, and fabricate the circuit required to drive the OLED on the silicon substrate;

[0061] Step 2: Anodic deposition, typically using a four-layer structure, from bottom to top: 1. Bonding layer (10-1000 Å), options include Ti, Ta, TiN, or TaN; 2. Reflective layer (500-5000 Å), options include highly reflective materials such as Al or Ag; 3. Diffusion barrier layer (10-200 Å), options include Ti, Ta, TiN, or TaN; 4. Work function adjustment layer (100-5000 Å), requiring good conductivity, high work function, energy level matching with the HOMO of the hole injection material, good chemical and morphological stability, and good light transmittance in the visible light region. Options include ITO (indium tin oxide), ITO (indium tin oxide), IGZO (indium gallium zinc oxide), IZO (indium zinc oxide), ZnO (zirconia), and AZO (zinc aluminum oxide). Two or three layers can also be used, with the bonding layer and diffusion barrier layer not mandatory; for example, the commonly used structure is Ti / Al / Ti / ITO.

[0062] Step 3: Use a mask to block the areas where the R, G, and B pixels are located, and then perform anodizing.

[0063] Step 4: Anodic etching and resist removal to form R-pixel anode, G-pixel anode, and B-pixel anode;

[0064] Step 5: R-pixel photolithography, using a mask to block the G-pixel anode and B-pixel anode, and performing photolithography on the R-pixel anode;

[0065] Depending on the different light-emitting materials and device requirements of RGB, two or three different work function / refractive index anode structures can be selected. With two different work function / refractive index anode structures, RB, RG, or GB share one structure, while another pixel uses a different structure. With three different work function / refractive index anode structures, RGB uses different anode structures. The fabrication order is not limited; RGB, RBG, GBR, GRB, BGR, and BRG are all acceptable. This invention uses three different work functions and the RGB sequence as an example for detailed explanation.

[0066] Step 6: R-pixel ion implantation. Electrons (phosphorus, arsenic, antimony, etc.) or holes (boron, gallium, indium) are implanted into the work function adjustment layer using an ion implantation process. This adjusts the anode work function (4.5-8 eV) and refractive index. Electrons can adjust conductivity and refractive index, while holes adjust work function and refractive index. Based on the actual materials and device characteristics used, as well as the device's microcavity effect, appropriate implantation materials and processes are selected. Implantation materials can be electrons (phosphorus, arsenic, antimony, etc.) or holes (boron, gallium, indium, etc.). Implantation conditions: energy 100-200 keV, dose 1E15-1E20.

[0067] 1) When using Ir(piq)3 (tris(1-phenyl-isoquinoline)iridium(III)) as the red light material, Ir(piq)3 has the highest occupied molecular orbital HOMO = 5.1 eV and the lowest unoccupied orbital LUMO = 3.1 eV, resulting in the longest red light wavelength. The microcavity requires a large cavity size and a large refractive index, so materials with larger molecular weights can be selected. The injection energy and dose can be larger. For example, the injection materials can be BF3, B2H6, arsenic, antimony, gallium, or indium, etc. The injection conditions are: energy 100-200 keV, dose 1E15-1E20;

[0068] 2) When using DCJTB (4-(dicyanvinyl)-2-tert-butyl-6-(1,1,7,7-tetramethylguronidinyl-4-vinyl)-4H-pyran) as the red light material, DCJTB has a highest occupied molecular orbital (HOMO) of 5.4 eV and a lowest unoccupied molecular orbital (LUMO) of 3.2 eV, which is higher than Ir(piq)3. Implantation materials can include BF3, B2H6, arsenic, antimony, gallium, or indium, etc. Implantation conditions are: energy 150-200 keV, dose 1E18-1E20. The final determination will depend on the actual materials and device characteristics used, as well as the device's microcavity effects, and includes, but is not limited to, examples.

[0069] Step 7: Remove the photoresist. Use wet or dry processes to remove the photoresist and remove the mask on the G pixel anode and B pixel anode.

[0070] Step 8: G-pixel photolithography, using a mask to block the R-pixel and B-pixel anodes, and performing photolithography on the G-pixel anode;

[0071] Step 9: G-pixel ion implantation. Electrons or holes are implanted into the work function adjustment layer in the G-pixel anode using an ion implantation process. Based on the actual materials and device characteristics used, as well as the device's microcavity effect, appropriate implantation materials and implantation processes are selected. Implantation materials can be electrons (phosphorus, arsenic, antimony, etc.) or holes (boron, gallium, indium, etc.). Implantation conditions are: energy 50-150 keV, dose 1E12-1E18, and adjustment of the G-pixel anode work function (4.5-8 eV) and refractive index.

[0072] 1) When using Alq3 (8-hydroxyquinoline aluminum) HOMO = 5.62 eV, LUMO = 2.85 eV, or Ir(ppy)3 (tris(2-phenylpyridine)iridium) HOMO = 5.6 eV, LUMO = 3.0 eV as green light materials, the wavelength of green light is shorter than that of red light but longer than that of blue light. The microcavity needs to have a moderate cavity length and a moderate refractive index. Materials with a moderate molecular weight can be selected, and the injection energy and dose can be moderate, such as phosphorus, arsenic, or gallium, with an energy of 50-150 keV and a dose of 1E12-1E18.

[0073] 2) When using Ir(piq)2(acac)(bis(1-phenyl-isoquinoline)(acetylacetone)iridium(III)) as the green light material, the HOMO is 5.0 eV and the LUMO is 3.0 eV, which is lower than Alq3. Phosphorus, arsenic, or gallium can be selected, with energies of 50-100 keV and doses of 1E12-1E15. The final determination will depend on the actual material and device characteristics used, as well as the device's microcavity effects, including but not limited to examples.

[0074] Step 10: Remove the photoresist. Use a wet or dry process to remove the photoresist and remove the mask on the anode of the R and B pixels.

[0075] Step 11: B-pixel photolithography, using a mask to block the R and G pixels, and performing photolithography on the B-pixel anode;

[0076] Step 12: B-pixel ion implantation. Electrons or holes are implanted into the work function adjustment layer of the B-pixel anode using an ion implantation process. Based on the actual materials and device characteristics used, as well as the device microcavity effect, a suitable implantation material and implantation process are selected. The implantation material can be electrons (phosphorus, arsenic, antimony, etc.) or holes (boron, gallium, indium, etc.). The implantation conditions are: energy 10-100 keV, dose 1E5-1E15, and adjustment of the B-pixel anode work function (4.5-8 eV) and refractive index.

[0077] 1) When using ADN (9,10-bis(2-naphthyl)anthracene) as the blue light material, HOMO = 5.8 eV, LUMO = 2.6 eV, and FIrPic (bis(4,6-difluorophenylpyridine-N,C2)pyridinecarboxyiridium) as the blue light material, HOMO = 5.8 eV, LUMO = 3.1 eV, the blue light wavelength is the shortest. The microcavity needs to have a small cavity length and a small refractive index. Materials with smaller molecular weights can be selected, and the injection energy and dose are smaller, such as boron or phosphorus, with energy of 10-100 keV and dose of 1E5-1E15.

[0078] 2) The blue light material used is FIr6 (bis(4,6-difluorophenylpyridine)-tetra(1-pyrazolyl)boronic acid iridium) with a HOMO of 6.10 eV and a LUMO of 3.10 eV, which is higher than that of ADN and FIrPic. Boron, phosphorus, or gallium can be selected, with energies of 80-100 keV and doses of 1E14-1E15. The final determination will depend on the actual materials and device characteristics used, as well as the device's microcavity effects, and includes, but is not limited to, examples.

[0079] Step 13: Photoresist removal and annealing. Remove the photoresist using wet or dry processes to remove the mask on the R and G pixels; annealing to activate the ions implanted into the work function adjustment layer.

[0080] Step 14: Pixel definition layer fabrication. Organic or inorganic materials can be selected. Organic materials include polyimide photoresist, which is prepared using pixel definition layer coating, exposure, development, and high-temperature curing processes. Inorganic materials include silicon oxide, silicon nitride, silicon oxynitride, etc., which are prepared through pixel definition layer deposition, photolithography, etching, and lift-off processes.

[0081] Step 15: Evaporation / Encapsulation, evaporation of organic layers such as hole injection layer, hole transport layer, light-emitting layer, electron transport layer, and electron injection layer, and cathode, thin film deposition of oxide, silicon nitride, silicon oxynitride, aluminum oxide, etc. to complete encapsulation;

[0082] Step 16: Prepare the CF layer through a process of coating, exposure, development, and curing;

[0083] Step 17: Prepare a transparent protective layer.

[0084] Work function: The minimum energy required to move an electron from the interior of a solid to its surface. Generally, the work function refers to that of metals. Non-metallic solids rarely use the definition of work function; instead, they are expressed using contact potentials, typically HOMO and LUMO. In this invention, organic materials are used, so HOMO and LUMO are used to express the work function.

[0085] HOMO and LUMO generally refer to the highest occupied molecular orbital and the lowest unoccupied molecular orbital in organic materials. The energy difference between HOMO and LUMO is called the "band gap," and this energy difference is called the HOMO-LUMO energy level. It can sometimes be used to measure how easily a molecule can be excited: the smaller the band gap, the easier it is for the molecule to be excited.

[0086] Organic materials with different HOMO-LUMO properties are best paired with metals with different work functions to achieve efficiency and lifetime matching. If organic materials with different HOMO-LUMO properties use metals with the same work function, some materials will be less efficient and some will be more efficient, making it difficult to achieve lifetime matching.

[0087] This invention develops a process for separate ion implantation of RGB three pixels. By implanting electrons or holes into the anode work function adjustment layer of the RGB sub-pixels, the anode carrier mobility is improved. At the same time, the RGB anode work function (4.5-8eV) and refractive index are independently adjusted to match the requirements of different RGB light-emitting materials and adjust the microcavity effect. This enables independent adjustment of the RGB pixel spectrum, improves efficiency, and enhances the color gamut. It solves the problems of the traditional Micro OLED white light + CF solution, which suffers from the inability to adjust the light output of RGB pixels, low efficiency, and low color gamut.

[0088] Depending on the requirements of different RGB light-emitting materials, two or three anodes with different work functions can be selected. Ion implantation of electrons (phosphorus, arsenic, antimony, etc.) or holes (boron, gallium, indium) into the work function adjustment layer modulates the work function and refractive index. The additional injected electrons and holes also improve carrier mobility, increasing efficiency. Simultaneously, the RGB spectrum is independently adjusted to meet the different needs of various RGB pixels. The improved RGB spectrum is shown below. Figure 4 , 5 6. R pixels enhance red light and weaken blue and green light; G pixels enhance green light and weaken red and blue light; B pixels enhance blue light and weaken red and green light.

[0089] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the technical solution of the present invention, or the direct application of the concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A work function adjustable microdisplay structure, characterized in that: The assembly includes a silicon substrate (1), a driving circuit substrate (2), and an anode. The driving circuit substrate (2) is fabricated in the silicon substrate (1), and the anode is fabricated on the silicon substrate (1) above the driving circuit substrate (2). The anode includes an R-pixel anode (3), a G-pixel anode (4), and a B-pixel anode (5). Each of the R-pixel anode, G-pixel anode, and B-pixel anode includes: an adhesive layer, a reflective layer, a diffusion barrier layer, and a work function adjustment layer. Electrons or holes are implanted into the work function adjustment layers of the three RGB pixel anodes, respectively. In the R-pixel anode, the work function adjustment layer injects electrons or holes with an energy of 100-200 keV and a dose of 1E15-1E20. In the G-pixel anode, the work function adjustment layer injects electrons or holes with an energy of 50-150 keV and a dose of 1E12-1E18. In the B-pixel anode, the work function adjustment layer injects electrons or holes with an energy of 10-100 keV and a dose of 1E12-1E18. The dose of holes is 1E5-1E15; the adhesive layer, reflective layer, diffusion blocking layer, and work function adjustment layer are arranged sequentially from bottom to top. The thickness of the adhesive layer is 10-1000 Å, and the material used is Ti, Ta, TiN, or TaN; the thickness of the reflective layer is 500-5000 Å, and the material used is Al or Ag high-reflectivity material; the thickness of the diffusion blocking layer is 10-200 Å, and the material used is Ti, Ta, TiN, or TaN; the thickness of the work function adjustment layer is 100-5000 Å, and the material used is... The microdisplay structure also includes a pixel definition layer (6), which is set at both ends of the anode, and between the R pixel anode and the G pixel anode and between the G pixel anode and the B pixel anode. The pixel definition layer (6) is a T-shaped structure. The bottom of the pixel definition layer (6) is flush with the bottom of the anode and is in contact with the silicon substrate (1). The top of the pixel definition layer (6) is higher than the top of the anode. By developing RGB three-pixel ion implantation, electrons or holes are implanted into the RGB sub-pixel anode work function adjustment layer to improve the anode carrier mobility. At the same time, the RGB anode work function and refractive index are independently adjusted to match different RGB light-emitting materials and adjust the microcavity effect to achieve independent adjustment of the RGB pixel spectrum. The ion implantation electron material is phosphorus, arsenic or antimony. The ion implantation hole material is boron, gallium or indium.

2. The work function adjustable microdisplay structure as described in claim 1, characterized in that: The microdisplay structure also includes an organic light-emitting layer and a cathode (7) and an encapsulation layer (8). The organic light-emitting layer and cathode (7) are disposed above the pixel definition layer (6) and the R pixel anode (3), G pixel anode (4), and B pixel anode (5). The encapsulation layer (8) is disposed above the organic light-emitting layer and cathode (7). The bottom of the encapsulation layer (8) is provided with a groove for wrapping the protrusions of the organic light-emitting layer and cathode (7). The bottom of the encapsulation layer (8) and the top of the organic light-emitting layer and cathode (7) are interlocked.

3. The work function adjustable microdisplay structure as described in claim 2, characterized in that: The microdisplay structure also includes a CF layer (9) and a protective layer (10). The CF layer (9) is disposed on the encapsulation layer (8) at the positions corresponding to the R pixel anode (3), G pixel anode (4), and B pixel anode (5). The protective layer (10) is disposed on the encapsulation layer (8) and the CF layer (9). The bottom of the protective layer (10) and the CF layer (9) are interlocked.

4. A fabrication process for a work function-tunable microdisplay structure, characterized in that: Based on the work function-tunable microdisplay structure as described in any one of claims 1 to 3, the fabrication process includes the following steps: Step 1: Fabricate the driving circuit wafer, and fabricate the circuit required to drive the OLED on the silicon substrate; Step 2: Anodic deposition using a four-layer structure, from bottom to top: binder layer, reflective layer, diffusion barrier layer, and work function adjustment layer; the binder layer thickness is 10-1000 Å, and the material used is Ti, Ta, TiN, or TaN; the reflective layer thickness is 500-5000 Å, and the material used is Al or Ag high-reflectivity material; the diffusion barrier layer thickness is 10-200 Å, and the material used is Ti, Ta, TiN, or TaN; the work function adjustment layer thickness is 100-5000 Å, and the material used is ITO, ITO, IGZO, IZO, ZnO, or AZO. Step 3: Use a mask to block the areas where R, G, and B pixels are located, and then perform anodizing. Step 4: Anodic etching and resist removal to form R-pixel anode, G-pixel anode, and B-pixel anode; Step 5: R-pixel photolithography, using a mask to block the G-pixel anode and B-pixel anode, and performing photolithography on the R-pixel anode; Step 6: R-pixel ion implantation. Electrons or holes are implanted into the work function adjustment layer of the R-pixel anode using an ion implantation process. The implantation conditions are: energy 100-200 keV, dose 1E15-1E20, and the R-pixel anode work function and refractive index are adjusted. The R-pixel anode work function is 4.5-8 eV, and the electrons are phosphorus, arsenic, or antimony, while the holes are boron, gallium, or indium. Step 7: Remove the photoresist. Use wet or dry processes to remove the photoresist and remove the mask on the G pixel anode and B pixel anode. Step 8: G-pixel photolithography, using a mask to block the R-pixel and B-pixel anodes, and performing photolithography on the G-pixel anode; Step 9: G-pixel ion implantation. Electrons or holes are implanted into the work function adjustment layer in the G-pixel anode using an ion implantation process. The implantation conditions are: energy 50-150 keV, dose 1E12-1E18, and the work function and refractive index of the G-pixel anode are adjusted. Electrons are phosphorus, arsenic, or antimony, and holes are boron, gallium, or indium. The work function of the G-pixel anode is adjusted to 4.5-8 eV. Step 10: Remove the photoresist. Use a wet or dry process to remove the photoresist and remove the mask on the anode of the R and B pixels. Step 11: B-pixel photolithography, using a mask to block the R and G pixels, and performing photolithography on the B-pixel anode; Step 12: B-pixel ion implantation. Electrons or holes are implanted into the work function adjustment layer in the B-pixel anode using an ion implantation process. The implantation conditions are: energy 10-100 keV, dose 1E5-1E15, and the work function and refractive index of the B-pixel anode are adjusted. Electrons are phosphorus, arsenic, or antimony, and holes are boron, gallium, or indium. The work function of the B-pixel anode is adjusted to 4.5-8 eV. Step 13: Photoresist removal and annealing. Remove the photoresist using wet or dry processes to remove the mask on the R and G pixels; annealing to activate the ions implanted into the work function adjustment layer. Step 14: Prepare the pixel definition layer; Step 15: Evaporation / Encapsulation, evaporation of organic layers such as hole injection layer, hole transport layer, light-emitting layer, electron transport layer, and electron injection layer, and cathode, thin film deposition of oxide, silicon nitride, silicon oxynitride, aluminum oxide, etc. to complete encapsulation; Step 16: Prepare the CF layer and protective layer.

5. The fabrication process of a work function tunable microdisplay structure as described in claim 4, characterized in that: Step 6: R-pixel ion implantation: 1) When using Ir3 as the red light material, Ir3 has the highest occupied molecular orbital HOMO=5.1 eV and the lowest unoccupied orbital LUMO=3.1 eV. The implantation material can be BF3, B2H6, arsenic, antimony, gallium or indium. The implantation conditions are: energy 100-200 keV, dose 1E15-1E20. 2) When DCJTB is used as the red light material, the highest occupied molecular orbital HOMO of DCJTB is 5.4 eV and the lowest unoccupied molecular orbital LUMO is 3.2 eV, which is higher than Ir3. The implantation material can be BF3, B2H6, arsenic, antimony, gallium or indium. The implantation conditions are: 150-200 keV, dose 1E18-1E20.

6. The fabrication process of a work function tunable microdisplay structure as described in claim 4, characterized in that: Step 9: G-pixel ion implantation: 1) When Alq3 is used as the green light material, the highest occupied molecular orbital HOMO of Alq3 is 5.62 eV and the lowest unoccupied orbital LUMO is 2.85 eV. The implantation material is selected from phosphorus, arsenic or gallium. The implantation conditions are: energy 50-150 keV, dose 1E12-1E18. 2) When using Ir2acac as the green light material, the highest occupied molecular orbital (HOMO) of Ir2acac is 5.0 eV and the lowest unoccupied molecular orbital (LUMO) is 3.0 eV, which is lower than Alq3. The implantation material can be phosphorus, arsenic or gallium. The implantation conditions are: energy 50-100 keV and dose 1E12-1E15.

7. The fabrication process of a work function tunable microdisplay structure as described in claim 4, characterized in that: Step 12: B-pixel ion implantation: 1) When using AND and FirPic as blue light materials, the highest occupied molecular orbital (HOMO) of AND is 5.8 eV and the lowest unoccupied molecular orbital (LUMO) is 2.6 eV; the highest occupied molecular orbital (HOMO) of FirPic is 5.8 eV and the LUMO is 3.1 eV; the implantation material can be boron or phosphorus, and the implantation conditions are: energy 10-100 keV, dose 1E5-1E15; 2) When using Fir6 as the blue light material, Fir6 has a highest occupied molecular orbital HOMO=6.10 eV and a lowest unoccupied orbital LUMO=3.10 eV, which is higher than ADN and FirPic. The implantation material can be boron, phosphorus or gallium. The implantation conditions are: energy 80-100 keV, dose 1E14-1E15.

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