Improved organic light emitting diode (OLED) displays, devices, systems, and methods

Abstract

Apparatus and methods for enhancing images on an organic light emitting diode (OLED) display are described. A DIED device is formed with a first light emitting OLED stack, a charge generation layer (CGL), a second light emitting OLED stack, and a color filter. An OLED display pixel includes three sub-pixels, with each sub-pixel fabricated with a separate anode and color filter. A dielectric barrier is disposed between the separate anodes and around the perimeter of each separate anode of the three sub-pixels. In operation, when current flows to a desired one of the three sub-pixels, the lateral current flow through the CGL to adjacent sub-pixels is impeded, resulting in light generated by the desired sub-pixel 'and' reduced adverse light generation at the sub-pixels adjacent to the desired sub-pixel. The OLED device can include a microlens. The microlens collimates the light, thereby reducing the aperture of the emitted light.

Description

[0001] Related Applications

[0002] This application claims priority to U.S. Provisional Patent Application Serial No. 62 / 847,856, filed May 14, 2019, entitled “OLED LIGHT ENHANCEMENT,” and this application claims priority to U.S. Provisional Patent Application Serial No. 62 / 911,905, filed October 7, 2019, entitled “BACKPLANE FOR ORGANIC LIGHT EMITTING DIODE (OLED) DISPLAYS, APPARATUSES, SYSTEMS, AND METHODS.”

[0003] U.S. Provisional Patent Application Serial No. 62 / 847,856 is hereby incorporated by reference. U.S. Provisional Patent Application Serial No. 62 / 911,905 is hereby incorporated by reference. BACKGROUND 1. TECHNICAL FIELD

[0005] The present invention relates generally to displays, and more particularly to high brightness organic light emitting diode (OLED) displays and color purity in OLED displays. 2. BACKGROUND

[0007] OLED display technology is advancing rapidly. In particular, the development of efficient OLED materials and high-throughput OLED deposition equipment has enabled the large-scale commercialization of OLED displays. OLED devices have an organic semiconductor layer between two electrodes (an anode and a cathode). The electrodes are typically made of inorganic materials. Holes and electrons are injected from the anode and cathode, respectively, into the organic layer. When the electrons and holes recombine in the active organic layer, a photon is emitted.

[0008] A subset of OLED displays are micro-OLED displays, which typically have a diagonal size less than 1 inch. Micro-OLED displays typically have backplane integrated circuits fabricated on a single crystalline silicon (Si) substrate. Due to the high performance of Si transistors, the pixel size for making small high-resolution displays can be very small, typically equal to or less than 15 micrometers (pm). The backplane circuitry includes a pixel array, row / column drivers, video input, video processing, and programmable control.

[0009] Due to the small pixel size, full color micro OLED displays are typically made using a white light emitting OLED structure and color filters on top of it. Each pixel is composed of red (R), green (G), and blue (B) sub-pixels. Each sub-pixel has its own separate anode, but all sub-pixels share a common semi-transparent cathode. Ultra-high resolution displays up to 2560 x 2560 pixels have been demonstrated using this OLED configuration.

[0010] Micro OLED displays are considered a leading display candidate for next generation wearable products, such as virtual reality (VR) applications, augmented reality (AR) applications, and mixed reality (MR) applications, due to their small size and high resolution, low power consumption, and high video frame rate. One key performance challenge for micro OLEDs in these applications is high brightness operation with acceptable lifetime. Most applications require display brightness in excess of 1000 nits, and in some cases 5000-10,000 nits. While advances in OLED materials have significantly improved OLED brightness, it is very challenging to achieve such high brightness. This is problematic.

[0011] Attempts to increase OLED display brightness have resulted in multi-stack OLED structures, such as a tandem OLED structure 102, an example of which is schematically shown in Figure 1 However, the white light emitting tandem OLED design applied to micro displays has a major drawback. Since the sub-pixel anodes 110, 112, 114, etc. share a common cathode 116, current flowing from one anode to the common cathode 116 can laterally diffuse to adjacent pixels, especially along the highly conductive charge generation layer (CGL) 108 between the two diodes 104 and 106. The lateral current manifests as "cross-talk" or light leakage, indicated at 122 / 124 and / or 126 / 128, which can result in reduced image sharpness, and more seriously, reduced color purity. For example, the red sub-pixel 120 can be contaminated with some blue 128 and green 124, resulting in poor red color purity. This problem can degrade the color gamut of the display so significantly that tandem OLED micro displays are unacceptable for most applications. This is problematic.

[0012] Micro OLED display brightness is also affected by the fact that light output from an OLED emissive element is Lambertian in nature, meaning it is emitted over a wide range of output angles, typically greater than plus or minus fifty (50) degrees. As a result, some light is not efficiently collected by the optical elements used in wearable products, resulting in inadequate performance. This is problematic. BRIEF DESCRIPTION OF DRAWINGS

[0013] The application can best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:

[0014] Figure 1 A cross section of an existing dual stack tandem OLED display is illustrated.

[0015] Figures 2A-2D Various cross sections corresponding to process steps during the creation of a sub-pixel anode are illustrated in accordance with embodiments of the application.

[0016] Figure 3A A medium barrier in accordance with embodiments of the application is illustrated in cross section.

[0017] Figure 3B An enlarged view of a portion of the medium barrier of Figure 3A in accordance with embodiments of the application is illustrated in cross section.

[0018] Figure 4A Another medium barrier in accordance with embodiments of the application is illustrated in cross section.

[0019] Figure 4B An enlarged view of a portion of the medium barrier of Figure 4A in accordance with embodiments of the application is illustrated in cross section.

[0020] Figure 5 A process for improving the image presented on an OLED display by micro-structuring is illustrated in accordance with embodiments of the application.

[0021] Figure 6 Micro-lens fabrication for a sub-pixel in an OLED display is illustrated in cross section in accordance with embodiments of the application.

[0022] Figure 7 Micro-lens fabrication for a sub-pixel in a single stack OLED display is illustrated in cross section in accordance with embodiments of the application.

[0023] Figure 8 A process for improving the collimation of light from an OLED display is illustrated in accordance with embodiments of the application.

[0024] Figure 9 Combining micro-lenses for a sub-pixel in an OLED display with Figure 3A and Figure 3B a medium barrier as described in in accordance with embodiments of the application is illustrated in cross section.

[0025] Figure 10combinations of the micro-lenses for sub-pixels with the Figure 4A and Figure 4B media barriers described in

[0026] Figure 11 processes for improving the image quality and brightness of OLED displays according to embodiments of the application. DETAILED DESCRIPTION

[0027] In the following detailed description of embodiments of the application, reference is made to the accompanying drawings, in which like references indicate like elements, and in which the particular embodiments of the application are shown by way of illustration. The embodiments are described in sufficient detail to enable those skilled in the art to practice the application, and the descriptions herein are not intended to limit the scope of the application. In other instances, well-known circuits, structures and techniques have not been shown in detail in order not to obscure the understanding of this description. Thus, the following detailed description is not intended to limit the scope of the application, as claimed, and the scope of the embodiments of the application solely by the appended claims.

[0028] Devices, methods and systems are described for providing high brightness OLED displays that produce both excellent color purity as well as clear images and wide color gamut. As used in the description of embodiments, displays and micro-displays will be given broad meaning and can be used interchangeably. Note that embodiments of the application are applicable to displays of all sizes, including micro-displays of 1.5 inches or less as measured across the diagonal of the display to large flat panel displays of many feet as measured across the diagonal of the display. Thus, embodiments of the application are applicable to displays of any size. Also, as used in the description of embodiments, it will be understood that the pixels of an OLED display can be made up of multiple sub-pixels, where each sub-pixel is used to contribute a separate light color to the pixel. Note that the terms "pixel", "display pixel", "display element" or "OLED device" are used synonymously and all of these terms (i.e., "pixel", "display pixel", "display element" or "OLED device") will be distinguished from "sub-pixel". Additionally, for clarity in the illustrations, one or more OLED pixels will be described in the later figures, however it will be understood that such description extends to the entire display having many display pixels configured in a row and many rows that are configured to provide a display having a general number of m rows and n columns of OLED display elements on which an image is provided to a user.

[0029] Figures 2A-2D various cross-sections corresponding to process steps during the creation of a sub-pixel anode according to embodiments of the application. Reference is made to Figures 2A-2DIn various embodiments, micro OLED displays are fabricated using silicon (Si) semiconductor fabrication techniques for the display backplane. When Si fabrication techniques are used for the backplane, it is often desirable to use anode materials that are commonly used in Si integrated circuit processing. In various embodiments, an anode is made with a thin layer of titanium nitride (TiN) on top of aluminum (Al). TiN has a high work function (-4.6 eV) similar to indium tin oxide (ITO) (-4.5 eV), thus facilitating hole injection. If the TiN film is made thin enough, such as 3 nanometers (nm), the reflectivity of TiN / Al can be very high, approaching ninety percent (90%), thus providing high emission efficiency. OLED devices using TiN / Al anodes are implemented to have good performance in terms of low OLED diode voltage and high OLED current efficiency.

[0030] In one or more embodiments, a method for forming a TiN anode, such as illustrated in any of the figures herein, includes:

[0031] 1. A backplane integrated circuit is fabricated on Si using typical complementary metal oxide semiconductor (CMOS) processing to drive the OLED display. This can consist of six metal processing (not including anode metal), a representative example of which is illustrated at 226.

[0032] 2. On top of the processed wafer, anode metal processing is performed. A thick dielectric layer 202, such as silicon dioxide (SiO2), is deposited over the top metal layer and planarized by a chemical mechanical polishing (CMP) step. "Via" holes 206 are etched in the dielectric layer 202 and filled with metal, such as tungsten.

[0033] 3. In various embodiments, a metal stack consisting of TiN / Al / TiN / Ti (indicated at 218, 216, 214, 212) or TiN / Al / Ti is deposited on top of SiO2 as the anode metal layer. A representative metal stack for the anode is shown at 210. The top TiN thickness is in the range of 2-5 nm. The Al thickness is in the range of 30-60 nm. The bottom TiN / Ti or titanium (Ti) layer is an adhesion layer to the oxide below the anode metal layer. The bottom TiN thickness is in the range of 5-10 nm, and the Ti thickness is in the range of 1-10 nm.

[0034] 4. The metal stack is then patterned into individual anodes for red (R), green (G), and blue (B) sub-pixels 220 by photolithography and etching.

[0035] In various embodiments, the existing problems of OLED displays, such as but not limited to: emission efficiency, cross-talk between sub-pixels, color gamut reduction, lack of image sharpness, etc., are eliminated by creating a barrier between OLED sub-pixels along with a multi-stack OLED structure. For example, a tandem OLED structure consists of two OLED diodes connected in series, where the luminous efficiency as measured in candela per ampere current (Cd / A) can theoretically be doubled compared to a single junction OLED diode. In a double stack tandem OLED structure, a highly conductive "charge generation layer" (CGL) is typically inserted between the two OLED diodes to minimize the voltage drop between the two diodes as current flows from one diode to the other. Ideally, the voltage of a double stack tandem OLED should be only twice that of a single junction OLED. This CGL layer is important to avoid excessive voltage across the tandem OLED device to minimize OLED power consumption.

[0036] Figure 3A A media barrier according to an embodiment of the present application is generally illustrated in cross-section at 300. Figure 3B A detailed view of a portion of Figure 3A is illustrated at 350. Reference is made to Figure 3A and Figure 3B together, to illustrate the resulting cross-section in an OLED device resulting from the method of creating a "barrier" between sub-pixels to reduce or prevent lateral current flow in a tandem or double stack OLED device. The double stack OLED device is made with a first light emitting OLED stack 310, a charge generation layer 312, and a second light emitting OLED stack 314. As illustrated in Figure 3A / 3B, a media "barrier" is formed between the anode of each sub-pixel. This structure is formed by media layer deposition followed by masked etching to expose the anode metal. The thickness of the media (indicated by h DB at 352) is chosen such that it is substantially greater than the thickness of the lower OLED stack 310 (indicated by h S at 354). h DBThe thickness of the CGL layer 312 ranges from 1000 Angstroms (A) to 5000 A, with a preferred range of 1500 A and 3000 A. The CGL layer 312, which is on top of the lower OLED stack 310, will become severely "non-planar" over the "barriers" 308a, 308b, 308c, 308d, etc. As a result, the CGL layer 312 can have a greatly reduced thickness (as indicated at 358 / 360 over the "barrier" 308b) relative to the CGL thickness at 356, and can become even discontinuous in these areas. These variations in the CGL layer 312 result in reduced electrical conductance and reduced lateral current. The reduced conductance and reduced lateral current reduce and / or eliminate cross-talk between sub-pixels (indicated by 332, 336, and 340 in the OLED structure); thereby, image sharpness is improved and proper color gamut is maintained. Both of these contribute to creating high quality images on the OLED display.

[0037] In various embodiments, the method for creating Figure 3A The method illustrated in the cross-section in FIG. 3 proceeds as follows:

[0038] 1. In various embodiments, a backplane integrated circuit (indicated at 226) is fabricated to drive the OLED display elements using typical CMOS processing. This can consist of a six-fold metal processing (not including the anode metal).

[0039] 2. On top of the processed wafer, an anode metal processing is performed. A thick dielectric layer 202 (such as SiO2) is deposited over the top metal layer and planarized by a chemical mechanical polishing (CMP) step. Vias 206 are etched in the dielectric layer 202 and filled with metal (such as tungsten).

[0040] 3. Individual anodes are fabricated for each sub-pixel by metal deposition and etching. In one or more embodiments, when the display is based on a red, blue, green (RBG) color map and one pixel is implemented with individual sub-pixels, then each sub-pixel is used to contribute a specific color (i.e., red, blue, or green) to a given pixel. Thus, the anode metal layer 210 can be a stack consisting of TiN / Al / TiN / Ti or TiN / Al / Ti and is deposited over the SiO2indicated at 202 (see, e.g., "CMOS Analog Circuit Design", by J. J. B. Y. Tsividis, Oxford University Press, 1997). The anode metal layer is etched between the sub-pixels by photolithography and dry etching to produce individual sub-pixel anodes 302, 304, 306, etc. Figure 2A

[0041] 4. A dielectric layer consisting of SiO2is deposited over the entire surface. The thickness of the dielectric layer ranges from 100 nm to 500 nm, preferably from 200 nm to 300 nm.

[0042] ​5. In various embodiments, a photo process is used to define openings above the anodes, and then etching is performed to remove the medium to expose the anode metal. The etching can be done by dry etching, wet etching, or a combination of dry and wet etching. This process results in medium barriers 308b between sub-pixel anodes 302 and 304, and medium barriers 308c between sub-pixel anodes 304 and 306, among others. The similar structure is repeated for the entire row of pixels. Figure 3A / 3B only illustrates one segment of which. Also, the similar structure is repeated for the multiple rows of pixels using OLED pixels to create an m row by n column display. Note that each pixel uses its own three sub-pixels to produce the desired color.

[0043] As used in the description of embodiments, two light emitting OLED stacks 310 and 314 are used with a CGL layer 312 disposed between 310 and 314. Embodiments taught herein are readily used with existing OLED stacks and CGL layers. For illustration only and by no way implying limitation, a non-limiting example of an OLED stack is one made with multiple layers including: a hole injection layer, a hole transport layer, an emission layer with a host dopant, an electron transport layer. OLED stack 310 can emit primarily in one color such as red or two colors such as red and green. OLED stack 314 can emit primarily in another color such as blue or two colors such as green and blue. The overall emission from the two OLED stacks 310 and 314 emits in a broad spectrum similar to white. For illustration only and by no way implying limitation, a non-limiting example of a CGL layer is one made with an n-doped organic material and a p-doped organic material such as Li: tris(8-hydroxyquinoline) aluminum (III) (Alq3) / FeCl3: 4,4'-N,N'-bis[N-(l-naphthyl)-N-phenylamino]biphenyl (NPB) and 4,7-diphenyl-l,10-phenanthroline (BPhen): Rb2CO3 / NPB: ReO3.

[0044] In various embodiments, more than two OLED stacks are used, for example, three light emitting OLED stacks are connected in series via two CGL layers. In this case, each OLED stack can emit primarily in one wavelength such as red, green, and blue. Alternatively, one OLED stack can emit primarily in two wavelengths such as red and green, and two stacks can emit primarily in the blue wavelength.

[0045] In various embodiments, for OLED displays, contact to the cathode 316 is made by a cathode ring contact located at the ambient of the display (not shown). During emission, electrons are transported to the pixel area via the cathode layer. Due to the large relief of the device structure (which is created by the dielectric barriers), a thin metal cathode layer made of silver (Ag) or silver / magnesium (Ag / Mg) can not be continuous across high dielectric barriers 308a, 308b, 308c, 308d, etc. On the other hand, a thicker cathode made of a transparent conductive material such as indium tin oxide (ITO) can form a continuous layer, but its electrical conductivity can not be high enough to introduce substantial voltage drop at the center of the display if the diagonal size of the display is larger than 0.5 inch. Lower effective voltage at the center of the display will reduce the display brightness in that area, and the uniformity across the display area will be worse. This problem can be overcome using a cathode 316 consisting of a combination of a thin layer of metal (Ag or Ag / Mg) and a thicker layer of transparent oxide (ITO or InZnO). In various embodiments, layer 317 is needed to protect the OLED layers from moisture penetration, as these OLED layers are very susceptible to water damage. Layer 317 can include a dielectric layer such as silicon nitride or zirconium oxide deposited by atomic layer deposition or chemical vapor deposition, and it can also include additional organic layers. On top of 317, color filters 330, 334, and 338 are fabricated. As described above, OLED stacks 310 and 314 emit white light.

[0046] Color filters 330, 334, and 338 filter the white light and emit their specific color light, respectively. In a non-limiting example provided in one or more embodiments for illustration only, a typical color filter is made by using photo patterning on a photosensitive colored material. The material is typically a negative photoresist mixed with special color pigments (such as R, G, B). In addition, a transparent material without pigments is also used as an underlayer material to improve adhesion and / or as a cover layer material to protect the color filter layer. The process of color filter can include the following steps:

[0047] 1. Spin on a transparent photosensitive material, pre-bake, expose to UV light to convert the material to a stable layer, and perform a post-bake. Typical post-bake temperature is 100°C.

[0048] 2. Spin on a photosensitive material with blue pigments, pre-bake, use a photomask for the blue sub-pixel pattern to expose the material, develop with a solvent to remove the unexposed material, UV post-cure, and post-bake.

[0049] 3. Spin on a photosensitive material with blue pigments, pre-bake, use a photomask for the green sub-pixel pattern to expose the material, develop with a solvent to remove the unexposed material, UV post-cure, and post-bake.

[0050] 4. Spin on photosensitive material with blue pigment, pre-bake, use photomask for red sub-pixel pattern to expose material, develop with solvent to remove unexposed material, UV post-cure and post-bake.

[0051] 5. Spin on transparent photosensitive material, pre-bake, expose with UV light to convert material to stable layer, and post-bake.

[0052] For a display created with red, green, blue (RGB) color scheme, in one embodiment, color filter 330 filters white light emitted by the OLED to provide an output of visible blue light; color filter 334 filters white light emitted by the OLED to provide an output of visible red light; and color filter 338 filters white light emitted by the OLED to provide an output of green light. Each of the color sub-pixels 332, 336, and 340 provides its respective color light contribution to the given display pixel of which it is a part. In operation, a user observes the output of the display pixel and perceives the overall color of the display pixel. The media barrier provides accurate color generation at the display pixel level by initially providing the accurate R, G, and B contributions from the sub-pixels to the OLED display pixel. In operation, when current flows to the desired sub-pixel of the three sub-pixels of any display element, the transverse current flow through the charge generation layer (CGL) to the adjacent sub-pixels is impeded, thereby causing light to be generated by the desired sub-pixel and reducing the adverse light generation at the sub-pixel adjacent to the desired sub-pixel. The described structure results in the OLED display accurately reproducing the desired color.

[0053] Figure 4A Another media barrier according to an embodiment of the present application is generally illustrated in cross-section at 400. Figure 4B A detailed view of a portion of Figure 4A is illustrated at 450. Reference is made to Figure 4A and Figure 4B , which illustrate the resulting cross-section in an OLED device resulting from the method of establishing a "barrier" between sub-pixels to reduce or prevent transverse current flow in a dual stack OLED device. The dual stack OLED device is made with a first white light emitting OLED stack 410, a charge generation layer 412, and a second white light emitting OLED stack 414. As shown in Figure 4A / 4B, a media "barrier" is formed between the anode of each sub-pixel. This structure is formed by media layer deposition, followed by masked etching to expose the anode metal. The thickness of the media (indicated by h DB at 452) is chosen so that it is greater than the thickness of the lower OLED stack 410 (indicated by h S(This is an expression). Therefore, h DB Greater than h S The CGL 412, located on top of the lower OLED stack 410, becomes significantly "non-planar" above the "barriers" 408a / 409a, 408b / 409b, 408c / 409c, 408d / 409d, etc. As a result, the CGL 412 can have a significantly reduced thickness relative to the CGL thickness 456 above the anode 302 (as indicated at 458 / 460 above the "barriers" 408b / 409b) and become discontinuous in these areas. These changes in the CGL 412 lead to reduced conductivity and decreased lateral current to adjacent subpixels. The reduced conductivity and decreased lateral current reduce and / or eliminate crosstalk between subpixels (indicated by 432, 436, and 440 in the OLED structure); thereby improving image sharpness and maintaining proper color gamut. Both of these contribute to creating high-quality images on OLED displays.

[0054] In various embodiments, for creating Figures 4A-4B The method for the cross-section shown in the figure is as follows:

[0055] 1. Note that, Figures 4A-4B The shape of the barrier and Figures 3A-3B The difference in the shape of the barrier is that, Figures 4A-4B The barrier in the middle is wider at the top, resembling a "mushroom" shape. (As in...) Figure 4B As illustrated at point 450, the width w of the upper barrier 409b db2 The width w of the lower part of the barrier 408b db1 Width. Therefore, w db2 Greater than w db1 .

[0056] 2. The dielectric layer of the barrier is formed by depositing SiO2 on top, followed by SiN. The thickness of SiO2 ranges from 100 nm to 500 nm, and the thickness of SiN ranges from 10 nm to 100 nm.

[0057] 3. After the SiO2 / SiN dielectric layer is etched (usually by dry etching), a subsequent wet etching is performed using oxide etching chemicals (such as buffered hydrogen fluoride (BHF) or diluted HF) to “undercut” the oxide while the top SiN layer remains largely undetched, resulting in a shape with a wider upper region and a narrower lower region.

[0058] 4. Such "mushroom" shaped barriers (i.e., 408a / 409a, 408b / 409b, 408c / 409c, 408d / 409d, etc.) are very effective in reducing the thickness of the CGL 458 / 460 over the dielectric barrier and thereby render the CGL discontinuous, such as in regions 458, 460 and wherever else the CGL traverses over the dielectric barrier between adjacent sub-pixel anodes.

[0059] In various embodiments, for an OLED display, contact to the cathode 416 is made by a cathode ring contact located at the display's (not shown) external environment. During emission, electrons should be transported to the pixel area via the cathode layer. Due to the large relief of the device structure (which is created by the dielectric barriers), a thin metal cathode layer made of silver (Ag) or silver / magnesium (Ag / Mg) can be discontinuous across high barriers (e.g., 408a / 409a, 408b / 409b, 408c / 409c, 408d / 409d, etc.). On the other hand, a thicker cathode made of a transparent conductive material such as ITO can form a continuous layer, but its electrical conductance can not be high enough, which can introduce a substantial voltage drop at the center of the display if the display's diagonal size is larger than 0.5 inch. Lower effective voltage at the center of the display will reduce the display brightness in that area, and the uniformity across the display area will be worse. This problem can be overcome using a cathode consisting of a combination of a thin layer of metal (Ag or Ag / Mg) and a thicker layer of transparent oxide (ITO or InZnO).

[0060] The layers over the cathode 416 follow the order and method described above in connection with Figure 3A and Figure 3B For example, in various embodiments, a passivation layer 417 and color filters 430, 434, and 438 are fabricated over the cathode 416. As described above, the first OLED stack 410 and the second OLED stack 414 are white light emitting structures. The color filters 430, 434, and 438 filter the white light and emit their specific color of light, respectively. As described above in connection with Figure 3A and Figure 3BAs described, typical color filters are fabricated at 430, 434, 438. For a display created with a red, green, blue (RGB) color map, in one embodiment, color filter 430 filters white light emitted by the OLED to provide an output of visible blue light; color filter 434 filters white light emitted by the OLED to provide an output of visible red light; and color filter 438 filters white light emitted by the OLED to provide an output of green light. Each of color sub-pixels 432, 436, and 440 provides its respective color light contribution to the given display pixel of which it is a part. In operation, a user observes the output of the display pixel and perceives the overall color of the display pixel. The media barrier provides accurate color generation at the display pixel level by initially providing the accurate R, G, and B contributions from the sub-pixels to the OLED display pixel. In operation, when current flows to the desired sub-pixel of the three sub-pixels of any display element, the transverse current flow through the charge generation layer (CGL) to the adjacent sub-pixels is impeded, thereby causing light to be generated by the desired sub-pixel and reducing adverse light generation at the sub-pixels adjacent to the desired sub-pixel. The described structure results in accurate color reproduction by the OLED display.

[0061] Figure 5 A process for improving the image presented on an OLED display by microstructure fabrication in accordance with an embodiment of the present application is generally illustrated at 500. Referring to Figure 5 , the process begins at block 502. At block 504, OLED sub-pixels are fabricated. Fabrication of the sub-pixels of an OLED display is described herein in connection with various figures, such as but not limited to, Figures 2A-4B , in various embodiments, silicon processing techniques are used to fabricate the OLED sub-pixels. At block 506, a media barrier is created between the sub-pixels. Creation of a media barrier between the sub-pixels is described herein in connection with various figures, such as but not limited to, Figures 3A-4B . At block 508, the process ends.

[0062] Light emitted from the OLED stack and output from the color filter typically has a wide output angle of greater than plus or minus fifty (50) degrees. Above each color filter, a microlens refractive element is added by microfabrication so that the light output can be increased and "collimated" into a narrower angle. The efficiency of light collimation depends on the light coupling efficiency between the color filter (CF) and the microlens interface and the shape of the microlens.

[0063] Figure 6 Micro-lens fabrication for sub-pixels in an OLED display in accordance with an embodiment of the present application is generally illustrated in cross-section at 600. Referring to Figure 6In various embodiments, microlens fabrication can be accomplished with either a thermal flow or a re-etching method. In the thermal flow method, the lens substrate has a photoresist function. The lens material includes an acrylic resin and a photoinitiator to make it photosensitive. After the lens substrate is patterned into a shape with sharp sidewalls (as indicated at 604), it is transformed into a lens shape by post-curing at a high temperature. It is desirable that the post-curing temperature is below 120°C, preferably below 100°C. For illustration purposes only, an example of a lens shape that has been post-cured is qualitatively illustrated at 606. The lens substrate is fabricated on the surface 602 by photolithography and development, which is similar to the color filter process described above.

[0064] Alternatively, a re-etching method can be used to fabricate the lens over the color filter. In various embodiments, with the re-etching method, the lens substrate does not have a photoresist function, and therefore, a higher refractive index material can be used for the lens. The fabrication process proceeds as follows:

[0065] 1. The lens material is first coated onto the surface of the OLED microstructure 602 over the color filter;

[0066] 2. The photoresist material is coated onto the lens material and formed into a square pattern by exposure and development. A thermal flow process is used to round the pattern.

[0067] Thereafter, a dry etching technique is used to etch the lens material under the photoresist. By purposefully adjusting the etching rates of the photoresist and the lens material, the lens shape 606 is formed in the microlens.

[0068] According to the technical description above, a microlens array is fabricated for a micro display with m rows and n columns. Such a display is illustrated generally by the pixels 1,1 to the pixels m,n represented at 610. In various embodiments, the OLED display is fabricated with a general number of m rows and n columns. Note that m and n can have the same value, or can have different values. Thus, the display can be fabricated with m and or n values that are less than 2560, equal to 2560, or greater than 2560.

[0069] Figure 7 Microlens fabrication for a sub-pixel in a single stack OLED display according to an embodiment of the application is illustrated generally in cross-section at 700. Reference is made to Figure 7Micro-lenses 702, 704, 706, etc. are fabricated on top of color filters 330, 334, 338, etc. in the OLED display. As previously mentioned, for clarity of illustration in this description of embodiments, one pixel with its three sub-pixels is used. The OLED device includes white light emitting OLED single stack 310 fabricated on sub-pixel anodes 302, 304, 306, etc. A common cathode is indicated at 316.

[0070] To achieve maximum light output from the OLED display, a vacuum cavity or a cavity filled with an inert gas is used above micro-lenses 702, 704, 706, etc. Such a cavity is indicated at 708. In various embodiments, cavity 708 can be filled with an inert gas or a vacuum can be created. Alternatively, a material with a higher refractive index (approximately 1.6 or higher) can be used to fabricate the micro-lenses and a resin with a lower refractive index (approximately 1.5 or lower) can be used to fill the gap between the micro-lenses and the cover 710. Cover 710 is made of a transparent material such as, but not limited to, glass. In operation, light emitted from sub-pixels 712, 714, 716, etc. is collimated by the structure above the color filters (various combinations of micro-lenses and gap filling materials in various embodiments) to increase the OLED display brightness.

[0071] Figure 8 A process to improve light collimation from an OLED display according to embodiments of the present application is illustrated generally at 800. Referring to Figure 8 , the process starts at block 802. At block 804, an OLED device is created. In various embodiments, a single stack white light emitting OLED or a series stack of white light emitting OLED layers can be used to fabricate the OLED device. Note that micro-lens fabrication can be applied to either OLED microstructures including a dielectric barrier Figures 3A-4B ) as well as OLED microstructures not including a dielectric barrier. At block 806, a micro-lens array is created on top of the OLED device fabricated at block 804. When the OLED device is in the "ON" state, collimation of the light output of the OLED display increases the display brightness to the user. At block 810, the process stops.

[0072] Figure 9 At 900, in cross-section, a combination of a micro-lens for a sub-pixel in an OLED display according to embodiments of the present application is illustrated generally with Figure 3A and Figure 3B a dielectric barrier described in Figure 9 . Referring to Figure 3A and Figure 3BThe OLED microstructures described herein are combined. The resulting OLED structure combines the benefits of increased color purity through the application of a dielectric barrier and increased display intensity through increased collimation of the output light. This provides an OLED display that produces clear, color-pure, and bright images.

[0073] Figure 10 The microlens for subpixels in an OLED display, according to an embodiment of the present invention, is illustrated in a cross-section at position 1000. Figure 4A and Figure 4B The media barriers described herein are combined. (Refer to...) Figure 10 The microlens manufacturing described above and Figure 4A and Figure 4B The OLED microstructures described herein are combined. The resulting OLED structure combines the benefits of increased color purity through the application of a dielectric barrier and increased display intensity through increased collimation of the output light. This provides an OLED display that produces clear, color-pure, and bright images.

[0074] Figure 11 A process for improving image quality and brightness from an OLED display according to an embodiment of the present invention is illustrated in general at 1100. (Reference) Figure 11 The process begins at block 1102. At block 1104, OLED sub-pixels are fabricated. This document incorporates various figures (such as, but not limited to,...) Figures 2A-4B This describes the fabrication of subpixels in an OLED display. In various embodiments, silicon fabrication techniques are used to fabricate the OLED subpixels. At block 1106, a dielectric barrier is created between the subpixels. In various embodiments, the figures (such as, but not limited to, [figures]) are incorporated herein by reference. Figures 3A-4B This describes the creation of dielectric barriers between sub-pixels. The OLED fabrication steps include OLED layer deposition, cathode layer formation, passivation, and color filter steps.

[0075] At block 1108, a microlens array is created on the OLED device, which is the processing subject in blocks 1104 and 1106. The process ends at block 1110. When the OLED device is in the "ON" state, the collimation of the light output from the OLED display increases, thereby improving the brightness of the display for the user. Figure 11 The process provides OLED displays that produce clear, pure, and bright images.

[0076] In various embodiments, the components of the OLED system described in the previous figures and the OLED system are implemented in an integrated circuit device, which can include an integrated circuit package including integrated circuits. In some embodiments, the components of the system and the system are implemented in a single integrated circuit die. In other embodiments, the components of the system and the system are implemented in more than one integrated circuit die of an integrated circuit device, which can include a multi-chip package including integrated circuits.

[0077] For the purpose of discussion and understanding of embodiments of the present application, it will be appreciated that those skilled in the art use a variety of terms to describe techniques and methods. Moreover, in the description, for the purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present application. It will be apparent, however, to one ordinarily skilled in the art that embodiments of the present application can be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring embodiments of the present application. Embodiments are described in sufficient detail to enable one of ordinary skill in the art to practice the present application, and it will be appreciated that other embodiments can be utilized and that logical, mechanical, electrical, and other changes can be made without departing from the scope of embodiments of the present application.

[0078] Accordingly, embodiments of the present application can be used to provide high brightness OLED displays. Embodiments of the present application also serve to improve image sharpness and maintain color gamut. Some non-limiting examples of OLED systems in which embodiments of the present application are used are, but are not limited to: mobile phones, large screen displays, use in near-to-eye (NTE) displays or head-mounted computing devices. Other embodiments of the present application are readily implemented in generally configured wearable or head-mountable devices, such as, but not limited to: wearable products such as virtual reality (VR), augmented reality (AR), mixed reality (MR); wristbands, watches, glasses, goggles, face shields, headbands, headgear, etc., or the like. As used in the present description of embodiments, wearable encompasses head-mountable, wrist-mountable, neck-mountable, and thus any wearable form can be applied to a user.

[0079] While the present application has been described with respect to several embodiments, those skilled in the art will recognize that the present application is not limited to the embodiments described, but can be practiced with modification and alteration within the spirit and scope of the appended claims. Accordingly, the description is to be regarded as illustrative instead of limiting.

Claims

1. An organic light emitting diode display apparatus comprising: an organic light emitting diode device formed with a first organic light emitting diode stack, a charge generation layer, a second organic light emitting diode stack, and a color filter, the organic light emitting diode device further comprising: three sub-pixels, each sub-pixel having a separate anode, the three sub-pixels sharing a common cathode, the common cathode further comprising: a first layer, the first layer being a thin layer made of metal; and a second layer, the second layer being a thick layer made of transparent oxide, the common cathode having a lower surface proximate to the separate anodes, an upper surface distal to the separate anodes, the separate anodes having a perimeter; and a dielectric barrier disposed between the separate anodes and around the perimeter of each separate anode of the three sub-pixels, the dielectric barrier extending above the separate anodes of the three sub-pixels into both the first organic light emitting diode stack and the second organic light emitting diode stack, the dielectric barrier having a maximum height above the separate anodes that is less than a minimum height of a majority of the lower surface of the common cathode located above the separate anodes, thereby causing the charge generation layer to have a contoured shape such that, in operation, when current flows to a desired sub-pixel of the three sub-pixels, a lateral current is impeded from flowing through the charge generation layer to an adjacent sub-pixel, thereby causing light to be generated by the desired sub-pixel and reducing adverse light generation at the sub-pixel adjacent to the desired sub-pixel.

2. The organic light emitting diode display apparatus of claim 1, wherein the color filter provides a different color filter to each of the three sub-pixels.

3. The organic light emitting diode display apparatus of claim 2, wherein the colors of the different color filters are red, blue, and green.

4. The organic light emitting diode display apparatus of claim 2, further comprising: a plurality of organic light emitting diode devices disposed in a row and column arrangement, thereby providing at least 2560 rows and 2560 organic light emitting diode devices in each row.

5. The organic light emitting diode display apparatus of claim 3, wherein the apparatus is a micro display.

6. The organic light emitting diode display apparatus of claim 1, further comprising: three micro lenses, each micro lens of the three micro lenses positioned over a different sub-pixel of the organic light emitting diode device, the micro lenses collimating emitted light in operation when light is emitted from the sub-pixels.

7. The organic light emitting diode display apparatus of claim 6, further comprising: a cover layer disposed over the micro lenses to form a gap.

8. The organic light emitting diode display apparatus of claim 7, wherein the gap is either filled with an inert gas or a vacuum is created in the gap.

9. The organic light emitting diode display apparatus of claim 6, further comprising: a cover layer; and ​ A filler material disposed between the microlenses and the cover layer, wherein the filler material has a refractive index less than a refractive index of the cover layer.

10. The organic light emitting diode display apparatus of claim 1, wherein the charge generation layer is thinned near the dielectric barrier.

11. The organic light emitting diode display apparatus of claim 10, wherein the dielectric barrier has sides that are significantly non-parallel.

12. The organic light emitting diode display apparatus of claim 1, wherein the charge generation layer is discontinuous near the dielectric barrier.

13. The organic light emitting diode display apparatus of claim 12, wherein the dielectric barrier is made of two different materials, a first material extending upward from the individual anodes and defining a first region characterized by a first width, a second material affixed to the first material, the second material extending upward and defining a second region characterized by a second width, the two different materials being processed such that the second width is wider than the first width.

14. The organic light emitting diode display apparatus of claim 13, wherein the first material is made of silicon dioxide SiO2 and the second material is made of silicon mononitride SiN.

15. An organic light emitting diode pixel microstructure, comprising: a plurality of pixel elements, each of the plurality of pixel elements further comprising: three sub-pixels; each of the three sub-pixels further comprising, in vertical stack over a substrate, in the following order: an anode; a first organic light emitting diode stack; a charge generation layer; a second organic light emitting diode stack; a cathode having a lower surface proximate the anode and an upper surface distal the anode; and a dielectric barrier disposed between the anodes and around a perimeter of each anode, the dielectric barrier extending over the anodes into both the first organic light emitting diode stack and the second organic light emitting diode stack, a maximum height of the dielectric barrier over the anodes being less than a minimum height of a majority of the lower surface of the cathode located over the anodes, thereby causing the charge generation layer to have a contoured shape such that, in operation, when current flows to a desired one of the three sub-pixels, a lateral current flow through the charge generation layer to an adjacent sub-pixel is impeded, resulting in light being generated by the desired sub-pixel and reducing adverse light generation at the sub-pixel adjacent the desired sub-pixel.

16. The organic light emitting diode pixel microstructure of claim 15, wherein the charge generation layer is thinned near the dielectric barrier.

17. The organic light emitting diode pixel microstructure of claim 15, wherein the charge generation layer is discontinuous near the dielectric barrier.

18. The organic light emitting diode pixel microstructure of claim 15, further comprising: a color filter disposed over each anode, wherein the color filter passes light having a color selected from the group consisting of red, blue, and green.

19. The organic light emitting diode pixel microstructure of claim 18, further comprising: a microlens disposed above the color filter, in operation the microlens collimates light in a direction substantially perpendicular to the plane of the microlens, thereby reducing the aperture of the emitted light.

20. A method for reducing undesired light generation on adjacent sub-pixels in an organic light emitting diode microstructure, comprising: creating a dielectric barrier in the organic light emitting diode microstructure, the dielectric barrier being created between each individual anode and around the perimeter of each individual anode; and creating a relief pattern in: a first organic light emitting diode stack; a charge generation layer of the organic light emitting diode microstructure; and a second organic light emitting diode stack, a cathode having a lower surface and an upper surface, the dielectric barrier extending above each individual anode into both the first organic light emitting diode stack and the second organic light emitting diode stack, the maximum height of the dielectric barrier above each individual anode being less than the minimum height of the majority of the lower surface of the cathode located above each individual anode, thereby causing the charge generation layer to have a relief shape such that, in operation, when current flows to a desired sub-pixel, the flow of lateral current through the charge generation layer to adjacent sub-pixels is impeded, resulting in light being generated by the desired sub-pixel and reducing the undesired light generation at sub-pixels adjacent to the desired sub-pixel.

21. The method of claim 20, wherein the charge generation layer is thinned near the dielectric barrier.

22. The method of claim 20, wherein the charge generation layer is discontinuous near the dielectric barrier.

23. The method of claim 20, further comprising: adding a color filter above each individual anode, wherein the color filter passes light having a color selected from the group consisting of red, blue, and green.

24. The method of claim 20, further comprising: forming a microlens above each individual anode, in operation each microlens collimates light in a direction substantially perpendicular to the plane of the microlens, thereby reducing the aperture of the emitted light.

25. The method of claim 24, wherein the forming comprises heating and reflowing a lens material to form the microlens.

26. The method of claim 24, wherein the forming comprises etching a lens material to form the microlens.

27. An organic light emitting diode display device, comprising: an organic light emitting diode device formed with a first organic light emitting diode stack, a charge generation layer, a second organic light emitting diode stack, and a color filter, the organic light emitting diode device further comprising: three sub-pixels, each sub-pixel having an individual anode and the individual anode having a perimeter; a common cathode, the common cathode having a lower surface proximate the individual anodes and an upper surface distal the individual anodes; a dielectric barrier disposed between the individual anodes and around a perimeter of each individual anode of the three sub-pixels, the dielectric barrier extending over the individual anodes of the three sub-pixels into both the first organic light emitting diode stack and the second organic light emitting diode stack, the maximum height of the dielectric barrier over the individual anodes being less than the minimum height of the majority of the lower surface of the common cathode located over the individual anodes, thereby causing the charge generation layer to have a contoured shape; and a microlens having a plane and configured over each sub-pixel, in operation, each microlens collimating light in a direction perpendicular to the plane, thereby minimizing stray light and impeding a lateral current flow through the charge generation layer to adjacent sub-pixels when a current flows to a desired sub-pixel of the three sub-pixels, such that light is generated by the desired sub-pixel and adverse light generation at sub-pixels adjacent to the desired sub-pixel is reduced.

28. The organic light emitting diode display apparatus of claim 27, further comprising: a cover disposed over the microlenses and creating a gap between the microlenses and a lower side of the cover.

29. The organic light emitting diode display apparatus of claim 28, wherein the gap contains an inert gas.

30. The organic light emitting diode display apparatus of claim 28, wherein a vacuum is created in the gap.

31. The organic light emitting diode display apparatus of claim 28, wherein the gap is filled with a resin, and a refractive index of the microlens material is greater than a refractive index of the resin.

32. The organic light emitting diode display apparatus of claim 27, wherein the charge generation layer is thinned near the dielectric barrier.

33. The organic light emitting diode display apparatus of claim 32, wherein the dielectric barrier has substantially vertical sides.

34. The organic light emitting diode display apparatus of claim 27, wherein the charge generation layer is discontinuous near the dielectric barrier.

35. The organic light emitting diode display apparatus of claim 34, wherein the dielectric barrier is made of two different materials, a first material extending upwardly from the individual anodes and defining a first region characterized by a first width, a second material affixed to the first material, the second material extending upwardly and defining a second region characterized by a second width, the two different materials being processed such that the second width is wider than the first width.

36. The organic light emitting diode display apparatus of claim 35, wherein the first material is made of silicon dioxide SiO2 and the second material is made of silicon mononitride SiN.

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