Organic light emitting diode display with patterned anode and optical cavity

Abstract

The invention relates to an organic light emitting diode display with a patterned anode and an optical cavity. A pixel in an organic light emitting diode (OLED) display may be a microcavity OLED pixel having an optical cavity. The optical cavity may be defined by a partially transparent cathode layer and a reflective anode structure. The anodes of the pixels may include both the reflective anode structure and a supplemental anode that is transparent and used to adjust the thickness of the optical cavity of each pixel. An organic light emitting diode layer may be formed over the pixels and may have a uniform thickness in each pixel in the display. The pixel may have a conductive spacer between the transparent anode portion and the reflective anode portion without an intermediate dielectric layer. The conductive spacer may be formed from a material compatible with the two anode portions, such as titanium nitride. The transparent anode portion may have a varying thickness to control a thickness of the optical cavity of the pixel.

Description

[0001] This application is a divisional application of the invention patent application with the application number 202010846180.0, the application date of August 20, 2020, and the title of "Organic Light Emitting Diode Display with Patterned Anode and Optical Cavity".

[0002] This patent application claims the priority of U.S. Non - Provisional Patent Application No. 16 / 888,451 filed on May 29, 2020 and U.S. Provisional Patent Application No. 62 / 891,142 filed on August 23, 2019, and these patent applications are hereby incorporated by reference in their entireties. BACKGROUND OF THE INVENTION

[0003] The present disclosure generally relates to electronic devices, and more particularly to electronic devices having a display.

[0004] Electronic devices typically include a display. For example, an electronic device may have an organic light - emitting diode (OLED) display based on organic light - emitting diode pixels. In this type of display, each pixel includes a light - emitting diode and a thin - film transistor that controls the application of a signal to the light - emitting diode to generate light. The light - emitting diode may include an OLED layer positioned between an anode and a cathode. To emit light from a given pixel in an organic light - emitting diode display, a voltage may be applied to the anode of the given pixel.

[0005] Some OLED pixels may include microcavity OLED pixels, where the OLED layer is covered by a partially transparent layer to form an optical cavity. The thickness of the optical cavity can be adjusted so that light of a selected wavelength is emitted efficiently. However, if not carefully designed, this type of OLED pixel may have non - uniform thickness, may have an aperture ratio smaller than desired, and / or may require a complex manufacturing process.

[0006] It is in this context that the embodiments herein are produced. SUMMARY OF THE INVENTION

[0007] The present disclosure discloses an electronic device that may have a display such as an organic light - emitting diode display. The organic light - emitting diode (OLED) display may have an array of organic light - emitting diode pixels, each of which has an OLED layer interposed between a cathode and an anode.

[0008] Pixels in the OLED display may be microcavity OLED pixels having an optical cavity. The optical cavity may be defined by a partially transparent cathode layer and a reflective anode structure. The anode of the pixel may include a supplementary anode that is transparent and is used to adjust the thickness of the optical cavity of each pixel.

[0009] A white organic light-emitting diode layer may be formed over the pixels and may have a uniform thickness in each pixel of the display. The thickness of an optical cavity of each pixel is controlled using the thickness of a transparent anode stack including a supplementary anode and an additional spacer layer. The blue pixels, green pixels, and red pixels may have successively thicker optical cavities.

[0010] The blue pixels may have a conductive spacer between the transparent anode portion and the reflective anode portion. The conductive spacer may be formed of a material compatible with the two anode portions such as titanium nitride. No other dielectric layer may be formed between the anode portions of the blue pixels. This means that the blue pixels do not require vias, thereby increasing the aperture ratio of the blue pixels.

[0011] In some arrangements, the transparent anode portion may have a varying thickness to control the thickness of the optical cavity of the pixel. For example, the transparent anode portion of the red pixels may be thicker than the transparent anode portion of the green or blue pixels. In such an arrangement, the dielectric layer under the transparent anode portion of the red pixels may be thinner, making it easier to form a through-hole through the dielectric layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic diagram of an exemplary electronic device having a display according to one embodiment.

[0013] Figure 2 is a schematic diagram of an exemplary display according to one embodiment.

[0014] Figure 3 is a diagram of an exemplary display pixel circuit according to one embodiment.

[0015] Figure 4 is a cross-sectional side view of an exemplary display having microcavity organic light-emitting diode pixels, the microcavity organic light-emitting diode pixels including at least one pixel having no through-hole between the anode portions.

[0016] Figure 5 is a cross-sectional side view of an exemplary display having microcavity organic light-emitting diode pixels, the microcavity organic light-emitting diode pixels having anode portions of different thicknesses.

[0017] Figure 6 is a cross-sectional side view of an exemplary display having microcavity organic light-emitting diode pixels, the microcavity organic light-emitting diode pixels including pixels of three colors having no through-hole between the anode portions. DETAILED DESCRIPTION

[0018] Figure 1An exemplary electronic device of a type that may have a display is shown. The electronic device 10 may be a computing device such as a laptop computer, a computer monitor including an embedded computer, a tablet computer, a cellular phone, a media player, or other handheld or portable electronic device, a smaller device (such as a wristwatch device, a pendant device, a headset or earpiece device, a device embedded in glasses or other device worn on the user's head, or other wearable or micro device), a display, a computer monitor including an embedded computer, a computer monitor without an embedded computer, a gaming device, a navigation device, an embedded system (such as a system in which an electronic device having a display is installed in a kiosk or an automobile), or other electronic device. The electronic device 10 may have the shape of a pair of glasses (e.g., a support frame), may form a housing having a helmet shape, or may have other configurations for assisting in mounting and fixing components of one or more displays on the user's head or near the eyes.

[0019] As Figure 1 shown, the electronic device 10 may include control circuitry 16 for supporting the operation of the device 10. The control circuitry 16 may include a memory such as a hard disk drive memory, a non-volatile memory (e.g., a flash memory configured to form a solid state drive or other electrically programmable read-only memory), a volatile memory (e.g., a static random access memory or a dynamic random access memory), and the like. Processing circuitry in the control circuitry 16 may be used to control the operation of the device 10. The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application specific integrated circuits, and the like.

[0020] Input-output circuitry in the device 10 such as the input-output device 12 may be used to allow data to be provided to the device 10 and to allow data to be provided from the device 10 to an external device. The input-output device 12 may include buttons, joysticks, rollers, touchpads, keypads, keyboards, microphones, speakers, audio generators, vibrators, cameras, sensors, light emitting diodes and other status indicators, data ports, and the like. A user may control the operation of the device 10 by supplying commands through input resources of the input-output device 12 and may receive status information and other outputs from the device 10 using output resources of the input-output device 12.

[0021] The input-output device 12 may include one or more displays, such as display 14. The display 14 may be a touch screen display including a touch sensor for collecting touch input from a user, or the display 14 may be insensitive to touch. The touch sensor of the display 14 may be based on an array of capacitive touch sensor electrodes, an acoustic touch sensor structure, a resistive touch component, a force-based touch sensor structure, a light-based touch sensor, or other suitable touch sensor arrangements. The touch sensor for the display 14 may be formed by electrodes formed on a common display substrate having display pixels of the display 14, or may be formed by a separate touch sensor panel overlapping the pixels of the display 14. If desired, the display 14 may be insensitive to touch (i.e., the touch sensor may be omitted). The display 14 in the electronic device 10 may be a head-up display that can be viewed without the user having to move away from a typical viewing point, or may be a head-mounted display incorporated into a device worn on the user's head. If desired, the display 14 may also be a holographic display for displaying holograms.

[0022] The control circuit 16 may be used to run software on the device 10, such as operating system code and application programs. During operation of the device 10, the software running on the control circuit 16 may display images on the display 14.

[0023] Figure 2 is an illustration of an exemplary display 14. As Figure 2 shown, the display 14 may include layers, such as a base layer 26. The base layer, such as layer 26, may be formed of a rectangular planar material layer or a material layer having other shapes (e.g., circular or other shapes having one or more curved edges and / or straight edges). The base layer of the display 14 may include a glass layer, a polymer layer, a silicon layer, a composite film including polymer materials and inorganic materials, a metal foil, etc.

[0024] The display 14 may have an array of pixels 22 for displaying images for a user, such as pixel array 28. The pixels 22 in the array 28 may be arranged in rows and columns. The edges of the array 28 may be straight or curved (i.e., each row and / or each column of the pixels 22 in the array 28 may have the same length or may have different lengths). Any suitable number of rows and columns may be present in the array 28 (e.g., ten or more, one hundred or more, or one thousand or more, etc.). The display 14 may include pixels 22 of different colors. For example, the display 14 may include red pixels, green pixels, and blue pixels. Pixels of other colors, such as cyan, magenta, and yellow, may also be used.

[0025] The display driver circuit 20 can be used to control the operation of the pixels 28. The display driver circuit 20 can be formed by an integrated circuit, a thin film transistor circuit, and / or other suitable circuits. Figure 2 An exemplary display driver circuit 20 includes a display driver circuit 20A and additional display driver circuits such as a gate driver circuit 20B. The gate driver circuit 20B can be formed along one or more edges of the display 14. For example, the gate driver circuit 20B can be arranged along the left and right sides of the display 14, as Figure 2 shown.

[0026] As Figure 2 shown, the display driver circuit 20A (e.g., one or more display driver integrated circuits, thin film transistor circuits, etc.) can include communication circuitry for communicating with the system control circuit via a signal path 24. The path 24 can be formed by traces on a flexible printed circuit or other cables. The control circuit can be located on one or more printed circuits in the electronic device 10. During operation, the control circuit (e.g., Figure 1 the control circuit 16) can provide image data to a display driver integrated circuit in a circuit such as circuit 20 for causing an image to be displayed on the display 14. Figure 2 The display driver circuit 20A of

[0027] is located at the top of the display 14. This is merely illustrative. The display driver circuit 20A can be located at both the top and bottom of the display 14, or located in other parts of the device 10.

[0027] To display an image on the pixels 22, the display driver circuit 20A can supply corresponding image data to the data lines D while sending control signals to a supporting display driver circuit such as the gate driver circuit 20B via a signal path 30. With Figure 2 an exemplary arrangement, the data lines D extend vertically through the display 14 and are associated with respective columns of the pixels 22.

[0028] The gate driver circuit 20B (sometimes referred to as a gate line driver circuit or a horizontal control signal circuit) can be implemented using one or more integrated circuits and / or can be implemented using thin film transistor circuits on a substrate 26. The horizontal control lines G (sometimes referred to as gate lines, scan lines, emission control lines, etc.) extend horizontally through the display 14. Each gate line G is associated with a respective row of the pixels 22. If desired, there can be multiple horizontal control lines such as gate lines G associated with each row of the pixels. Separate control signal paths and / or global signal paths in the display 14 can also be used to issue other signals (e.g., power signals, etc.).

[0029] The gate driver circuit 20B can assert a control signal on the gate line G in the display 14. For example, the gate driver circuit 20B can receive a clock signal and other control signals from the circuit 20A on the path 30, and in response to the received signals, sequentially assert the gate line signals on the gate lines G starting from the gate line signals G in the first row of the pixels 22 in the array 28. When each gate line is asserted, data from the data line D can be loaded into the corresponding row of the pixels. In this way, control circuits such as the display driver circuits 20A and 20B can provide signals for the pixels 22 to indicate that the pixels 22 display a desired image on the display 14. Each pixel 22 can have a light-emitting diode and circuitry (e.g., thin-film circuitry on the substrate 26) that responds to the control signals and data signals from the display driver circuit 20.

[0030] The gate driver circuit 20B can include gate driver circuit blocks, such as gate driver row blocks. Each gate driver row block can include circuitry such as output buffers and other output driver circuits, register circuitry (e.g., registers that can be chained together to form a shift register), and signal lines, power lines, and other interconnects. Each gate driver row block can provide one or more gate signals to one or more corresponding gate lines in the corresponding pixel row of the pixel array in the active area of the display 14.

[0031] A schematic diagram of an exemplary pixel circuit of the type that can be used for each pixel 22 in the array 28 is shown in Figure 3 As Figure 3 shown, the display pixel 22 can include a light-emitting diode 38. A positive power supply voltage ELVDD can be provided to the positive power supply terminal 34, and a ground power supply voltage ELVSS can be provided to the ground power supply terminal 36. The diode 38 has an anode (terminal AN) and a cathode (terminal CD). The state of the driving transistor 32 controls the amount of current flowing through the diode 38, and thus controls the amount of emitted light 40 from the display pixel 22. Since the cathode CD of the diode 38 is coupled to the ground terminal 36, the cathode terminal CD of the diode 38 can sometimes be referred to as the ground terminal of the diode 38.

[0032] To ensure that transistor 38 remains in a desired state between successive data frames, display pixel 22 may include a storage capacitor, such as storage capacitor Cst. The voltage on storage capacitor Cst is applied to the gate of transistor 32 at node A to control transistor 32. One or more switching transistors, such as switching transistor 33, may be used to load data into storage capacitor Cst. When switching transistor 33 is off, data line D is isolated from storage capacitor Cst, and the gate voltage at terminal A is equal to the data value stored in storage capacitor Cst (i.e., the data value from the previous frame of display data being displayed on display 14). When the gate line G (sometimes referred to as a scan line) in the row associated with display pixel 22 is asserted, switching transistor 33 will be turned on and the new data signal on data line D will be loaded into storage capacitor Cst. The new signal on capacitor Cst is applied to the gate of transistor 32 at node A, thereby adjusting the state of transistor 32 and adjusting the corresponding amount of light 40 emitted by light emitting diode 38. If desired, the circuitry for controlling the operation of the light emitting diodes (e.g., transistors, capacitors, etc. in a display pixel circuit such as a display pixel circuit of Figure 3 the kind) in display 14 may be formed using other configurations (e.g., configurations including circuitry for compensating for threshold voltage variations in driving transistor 32, etc.). The display pixel may include additional switching transistors, emission transistors in series with the driving transistor, etc. Capacitor Cst may be located at other desired locations within the pixel (e.g., between the source and gate of the driving transistor). Figure 3 The display pixel circuit of

[0033] Figure 4 is a cross-sectional side view of an exemplary display having organic light emitting diode display pixels. As shown, display 14 may include a substrate 26. Substrate 26 may be formed of glass, plastic, polymer, silicon, or any other desired material. Substrate 26 may include thin film transistor circuitry for applying control signals to the pixels and may thus sometimes be referred to as a thin film transistor substrate. Figure 4 Red pixel 22-R, blue pixel 22-B, and green pixel 22-G are shown.

[0034] Anodes 42 such as anodes 42-R, 42-G, and 42-B may be formed on substrate 26. Anodes 42-R, 42-G, and 42-B may be formed of a conductive material and may be covered by OLED layer 45 and cathode 54. OLED layer 45 may include one or more layers for forming an organic light emitting diode. For example, layer 45 may include one or more of a hole injection layer (HIL), a hole transport layer (HTL), an electron blocking layer (EBL), an emission layer (EML), an electron transport layer (ETL), and an electron injection layer (EIL). OLED layer 45 may be formed of a combination of a white OLED layer (e.g., an OLED layer configured to emit white light), red, green, blue, and / or yellow OLED layers, etc. Cathode 54 may be a conductive layer formed on OLED layer 45. Cathode layer 54 may form a common cathode terminal for all the diodes in display 14 (see, e.g., Figure 3 for the cathode terminal CD). Each anode in display 14 may be independently controlled such that each diode in display 14 may be independently controlled. This allows each pixel 22 to produce an independently controlled amount of light.

[0035] In some OLED displays, cathode 54 is fully (or almost fully) transparent and anode 42 may be in direct contact with OLED layer 45. However, Figure 4 displays use an optical cavity to improve efficiency and color purity in the display. Using an optical cavity as in Figure 4 allows a uniform white OLED layer 45 to provide red, green, and blue light from red pixel 22-R, green pixel 22-G, and blue pixel 22-B, respectively. The optical cavity may be formed by reflective layers formed on either side of the OLED layer within the display. By adjusting the thickness of the optical cavity including the OLED layer, each pixel may be optimized to have high emission at a desired wavelength. To form this type of optical cavity, Figure 4 display 14 in

[0036] The cathode layer 54 may be formed of a partially transparent conductive material. In an illustrative example, the cathode layer 54 may be formed of a combination of magnesium (Mg) and silver (Ag). The cathode layer 54 may be formed of any other desired conductive material or combination of conductive materials. The cathode 54 may transmit less than 90% of the light, less than 80% of the light, less than 70% of the light, less than 60% of the light, less than 50% of the light, more than 40% of the light, more than 50% of the light, more than 60% of the light, between 40% and 80% of the light, between 45% and 60% of the light, between 60% and 70% of the light, between 50% and 75% of the light, etc. The cathode 54 may reflect more than 10% of the light, more than 20% of the light, more than 30% of the light, more than 40% of the light, more than 50% of the light, more than 60% of the light, less than 50% of the light, less than 60% of the light, between 20% and 60% of the light, between 40% and 55% of the light, between 30% and 40% of the light, between 25% and 50% of the light, etc.

[0037] The cathode layer 54 may define the first boundary of the optical cavity. The other boundary of the optical cavity may be set by the anode 42 (sometimes referred to as the anode portion 42). The anodes 42-R, 42-G, and 42-B may be formed of a highly reflective material such as aluminum, silver, or any other desired conductive material. Each anode 42 may reflect more than 70% of the light, more than 80% of the light, more than 90% of the light, more than 95% of the light, more than 99% of the light, etc.

[0038] Additional layers may be formed over the anode 42 between the anode and the OLED layer 45. However, these additional layers may be transparent and thus do not disrupt the optical cavity. Since the additional layers are transparent, the boundaries of the optical cavity are still determined by the reflective anode 42 and the cathode 54. The presence of additional transparent layers between the anode 42 and the cathode 54 may result in an increase in the distance between the reflective anode 42 and the cathode 54 (since the OLED thickness is uniform). Figure 4 A manner in which the pixel 22-R has an optical cavity with a thickness of 48-R between the anode 42-R and the cathode 54 is shown. The pixel 22-G has an optical cavity with a thickness of 48-G between the anode 42-G and the cathode 54. The pixel 22-B has an optical cavity with a thickness of 48-B between the anode 42-B and the cathode 54.

[0039] Adjust the thickness of each optical cavity to optimize the emission of the desired light color for that pixel. For a given optical cavity thickness, light of a given wavelength will resonate due to multiple reflections from the walls of the optical cavity (e.g., cathode 54 and anode 42). The increased emission at a given wavelength caused by resonance within the optical cavity may be referred to as the microcavity effect. Pixels optimized to induce this effect (such as Figure 4 the pixels in

[0040] Pixel 22-R has an optical cavity thickness 48-R that maximizes the emission of red light. Pixel 22-G has an optical cavity thickness 48-G that maximizes the emission of green light. Pixel 22-B has an optical cavity thickness 48-B that maximizes the emission of blue light. The wavelength of blue light is shorter than that of green light, and the wavelength of green light is shorter than that of red light. Generally speaking, the thickness of the optical cavity can be proportional to the wavelength of the type of light to be emitted. Thus, thickness 48-B is less than thickness 48-G, and thickness 48-G is less than thickness 48-R. This example is merely illustrative and may not apply to all display designs, as other factors such as the nodes of the cavity may affect the optical cavity.

[0041] Therefore, the thickness of each optical cavity is adjusted to optimize the emission of light. However, changing the thickness of each optical cavity during the manufacturing process can be difficult. To reduce the complexity and cost of manufacturing a microcavity OLED display, an additional anode portion 44 may be included in each pixel. As Figure 4 shown, the red pixel 22-R has an additional anode portion 44-R, the green pixel 22-G has an additional anode portion 44-G, and the blue pixel 22-B has an additional anode portion 44-B. These additional anode portions 44 (sometimes referred to as supplementary anodes 44, anodes 44, etc.) may be formed of a transparent conductive material. The additional anode portion may be formed of indium tin oxide (ITO) or any other desired transparent conductive material. Since the additional anodes are transparent, they can be used to adjust the optical cavity thickness 48 of the pixel without disrupting the optical cavity between anode 42 and cathode 54.

[0042] A pixel definition layer 66 may be formed between each pixel. The pixel definition layer may be formed of a non-conductive material and may be interposed between adjacent anodes of the display. The pixel definition layer may be formed of a non-conductive material (opaque or transparent) and may have openings formed therein for the anodes, thereby defining the area of each pixel.

[0043] An additional layer may be included between the anode portion 44 and the anode portion 42 in each pixel. As Figure 4As shown, a first dielectric layer 50 and a second dielectric layer 52 (sometimes referred to as spacers 50 and 52) are included in the display 14. The dielectric layer 52 has a portion formed above the anode 42-R in the red pixel 22-R. The dielectric layer 50 has a first portion formed above the anode 42-R in the red pixel 22-R and a second portion formed above the anode 42-G in the green pixel 22-G. The first portion of the dielectric layer 50 is interposed between the dielectric layer 52 and the supplementary anode 44-R. The second portion of the dielectric layer 50 is interposed between the anode 42-G and the supplementary anode 44-G.

[0044] The dielectric layers 50 and 52 and the supplementary anode 44 can all be transparent or substantially transparent. This allows these layers to be used as spacers, and the thicknesses of these spacers can be selected to adjust the thickness of the optical cavity of each pixel. The dielectric layers 50 and 52 and the supplementary anode 44 can transmit more than 90% of the incident light, more than 95% of the incident light, more than 99% of the incident light, more than 99.9% of the incident light, etc. The dielectric layers 50 and 52 can be formed of silicon dioxide, silicon oxynitride, another desired oxide material, silicon nitride, or any other desired transparent material.

[0045] The dielectric layers 50 and 52 can be used as spacer structures that allow adjustment of the cavity thickness 48 of each pixel. For ease of manufacturing, it is desirable that a white OLED layer 45 with a uniform thickness is formed on top of each supplementary anode 44. In this way, the OLED layer 45 can be formed in a single deposition step, rather than being patterned with OLED materials having different thicknesses and / or different colors for each pixel. As Figure 4 shown, the OLED thickness 56-R of the pixel 22-R, the OLED thickness 56-G of the pixel 22-G, and the OLED thickness 56-B of the pixel 22-B are substantially the same (e.g., within 5% of each other).

[0046] Without the spacer layers 50 and 52, the supplementary anode 44, and the conductive spacer 68, an OLED layer with a uniform thickness would result in the same optical cavity thickness for each pixel. As Figure 4 shown, including dielectric spacers and supplementary anodes allows adjustment of the optical cavity thickness for a desired color.

[0047] The supplementary anode 44 can be electrically connected to the anode 42. As Figure 4 shown, a via 60 can be formed that extends through the dielectric layers 50 and 52 to electrically connect the anode portion 44-R to the anode portion 42-R. In Figure 4 this case, the via 60 includes a conductive portion 62 and a conductive lining 64. Another via with the same structure (e.g., having a conductive portion and a conductive lining) is also formed through the dielectric layer 50 to electrically connect the supplementary anode 44-G to the anode 42-G.

[0048] Unlike pixels 22-R and 22-G, pixel 22-B may not include a via hole. Instead, a conductive layer 68 may be interposed between anode portions 42-B and 44-B. The conductive layer 68 may electrically connect anode portion 42-B and anode portion 44-B and may be in direct contact with anode portion 42-B and anode portion 44-B. A conductive layer 68 (sometimes referred to as a conductive spacer 68) may be included to avoid incompatibility between anode portion 44-B and anode portion 42-B. The conductive layer 68 may also facilitate better electrical contact between anode portion 44 and anode portion 42. For example, the transparent anode portion 44-B may be formed of a material that corrodes when in direct contact with the material of the reflective anode portion 42-B. For example, the transparent anode portion 44-B may be formed of ITO, while the reflective anode portion 42-B may be formed of aluminum. In this example, the conductive spacer 68 may be interposed between the anode portions to prevent corrosion.

[0049] The conductive layer 68 may be formed of titanium nitride (TiN) or another desired conductive material. The conductive layer 68 may be thin enough to be approximately transparent. For example, the conductive layer 68 may have a thickness of less than 10 nanometers, less than 5 nanometers, less than 3 nanometers, between 2 nanometers and 5 nanometers, between 1 nanometer and 6 nanometers, between 2 nanometers and 3 nanometers, between 1 nanometer and 3 nanometers, etc. The conductive layer 68 may transmit more than 80% of the incident light, more than 90% of the incident light, more than 95% of the incident light, more than 99% of the incident light, more than 99.9% of the incident light, etc.

[0050] In Figure 4 , no dielectric spacer is formed between anode portion 42-B and anode portion 44-B. Forming the supplementary anode portion 44-B directly above the anode portion 42-B together with the intermediate conductive layer 68 eliminates the need to include a dielectric layer in the anode stack of pixel 22-B. This is beneficial because the dielectric spacer in the anode stack of the blue pixel must be very thin, thus presenting manufacturing difficulties.

[0051] Additionally, forming the supplementary anode portion 44-B directly above the anode portion 42-B without an intermediate dielectric layer allows the via hole 60 (e.g., through the dielectric layer) to be omitted in pixel 22-B. Omitting the via hole in the blue pixel 22-B allows the aperture ratio of the blue pixel to be increased. The aperture of a pixel is the area from which light is emitted from the pixel. In Figure 4 the shown display, the aperture of each pixel is defined by the pixel defining layer 66 (e.g., this aperture corresponds to the area not covered by the opaque pixel defining layer). The aperture ratio refers to the ratio of the aperture (e.g., the light-emitting area) of a pixel to the non-light-emitting area of the pixel. Generally speaking, it is desirable to have a larger aperture ratio because a larger aperture ratio corresponds to higher display efficiency and improved display performance.

[0052] AsFigure 4 As shown, the vias 60 in pixels 22-R and 22-G are non-light-emitting regions and are thus covered by the pixel definition layer 66. The presence of the vias 60 reduces the aperture ratio of the pixels. Thus, omitting the vias 60 in Figure 4 the blue pixels increases the aperture ratio of the blue pixels 22-B.

[0053] In some cases, the anode portions 42-B and 44-B can be formed of materials that are compatible when in direct contact. For example, the anode portion 42-B can be formed of silver, while the anode portion 44-B can be formed of ITO. In this example, the conductive layer 68 can be omitted, and the anode portion 42-B can be formed to be in direct contact with the anode portion 44-B.

[0054] The conductive portion 62 of each via 60 can optionally be formed of the same material as the supplemental anode portion 44. For example, if the supplemental anode 44-R of pixel 22-R is formed of indium tin oxide, then the conductive portion 62 of the via 60 in pixel 22-R can also be formed of indium tin oxide. However, as discussed in connection with the conductive spacer 68, indium tin oxide cannot be placed in direct contact with the aluminum anode portion 42-R to prevent corrosion. Thus, a conductive lining 64 can be interposed between the conductive via portion 62 and the anode portion 42-R. The conductive lining 64 can be formed of the same material as the conductive layer 68 (e.g., titanium nitride). In fact, the conductive lining 64 can be formed during the same deposition step as the conductive layer 68 during the manufacture of the display. Similar to the way the conductive layer 68 can be omitted from the display based on material compatibility, if the conductive via portion 62 is compatible with the anode portion 42, the conductive lining 64 can be omitted.

[0055] Each layer in the display 14 can have any desired thickness. In some arrangements, the supplemental anode portions 44-R, 44-G, and 44-B can have the same thickness. Each supplemental anode portion can have a thickness of less than 100 nanometers, less than 50 nanometers, less than 30 nanometers, less than 20 nanometers, less than 15 nanometers, less than 10 nanometers, greater than 5 nanometers, between 5 nanometers and 50 nanometers, between 5 nanometers and 100 nanometers, etc. Similarly, each of the dielectric layers 50 and 52 can have any desired thickness (e.g., less than 100 nanometers, less than 50 nanometers, less than 30 nanometers, less than 20 nanometers, less than 15 nanometers, less than 10 nanometers, greater than 5 nanometers, between 5 nanometers and 50 nanometers, between 5 nanometers and 100 nanometers, etc.).

[0056] The supplementary anode and the underlying layer between the supplementary anode and the anode may be referred to as the anode stack. For example, pixel 22-R has an anode stack including supplementary anode 44-R, dielectric layer 50 (sometimes referred to as oxide layer 50), and dielectric layer 52 (sometimes referred to as oxide layer 52). The total thickness 70-R of the anode stack is adjusted to determine the total optical cavity thickness 48-R. Pixel 22-G has an anode stack including supplementary anode 44-G and dielectric layer 50. The total thickness 70-G of the anode stack is adjusted to determine the total optical cavity thickness 48-G. Pixel 22-B has an anode stack including supplementary anode 44-B and (optional) conductive spacer 68. The total thickness 70-B of the anode stack is adjusted to determine the total optical cavity thickness 48-B. In one arrangement, the thickness 70-R of the anode stack of the red pixel 22-R may be between 100 nanometers and 200 nanometers, the thickness 70-G of the anode stack of the green pixel 22-G may be between 70 nanometers and 100 nanometers, and the thickness 70-B of the anode stack of the blue pixel 22-B may be between 10 nanometers and 30 nanometers. These thickness values are merely illustrative. Each anode stack may have any desired thickness (e.g., greater than 200 nanometers, between 100 nanometers and 150 nanometers, between 50 nanometers and 125 nanometers, less than 100 nanometers, less than 50 nanometers, less than 25 nanometers, less than 20 nanometers, etc.).

[0057] Figure 4 The display has the above advantages, namely, the through holes in pixel 22-B are omitted to increase the aperture ratio. Additionally, the number of deposited layers is minimized to reduce manufacturing complexity and cost. Dielectric layer 52, dielectric layer 50, the conductive layer for liner 64 and layer 68, and the conductive layer for supplementary anode 44 may be deposited with a generally uniform thickness across the display, thereby reducing the need for additional patterning steps.

[0058] wherein a white OLED layer 65 is deposited uniformly for pixels 22-R, 22-G, and 22-B Figure 4 The example is merely illustrative. In some designs, each pixel may have a corresponding OLED layer of that color. For example, red pixel 22-R may have a red OLED layer (e.g., an OLED layer emitting red light), green pixel 22-G may have a green OLED layer (e.g., an OLED layer emitting green light), and blue pixel 22-B may have a blue OLED layer (e.g., an OLED layer emitting blue light). This type of arrangement may increase efficiency at the cost of increased manufacturing complexity.

[0059] Figure 5 is similar to Figure 4 The cross-sectional side view of a display with microcavity OLED pixels of a display similar to Figure 4 andFigure 5 duplicate description. In Figure 5 , each pixel includes a transparent supplementary anode 44 similar to that in Figure 4 . However, in Figure 5 , the thickness of the supplementary anode is different. For example, the supplementary anode 44-R may have a different (e.g., greater) thickness than the supplementary anodes 44-G and 44-B. This allows reducing the combined thickness of the dielectric layers 50 and 52 in the pixel 22-R while achieving the same anode stack height 70-R.

[0060] Reducing the thickness of the dielectric layers 50 and 52 may be beneficial because it results in shorter vias 60 in the pixel 22-R. Extending the vias 60 through thick dielectric layers can pose challenges. Fabricating vias that are both thin and deep may increase the manufacturing cost, may increase the manufacturing complexity, and may cause reliability issues. The vias can be made wider to more easily fabricate the same depth, but this sacrifices the aperture ratio of the pixel.

[0061] By reducing the Figure 5 thickness of the dielectric layers 50 and 52, the vias can be shorter and thus easier to fabricate without sacrificing the aperture ratio. Additionally, the dielectric layers 50 and 52 in the pixels 22-R and 22-G have the same thickness. Therefore, the vias 60 in the pixel 22-R have the same depth as the vias 60 in the pixel 22-G. Thus, the vias of the pixels 22-R and 22-G can be fabricated in the same processing step, thereby reducing the manufacturing cost and complexity.

[0062] By adjusting the supplementary anode thickness, the desired anode stack thickness 70 and optical cavity thickness 48 can remain unaffected even when reducing the thickness of the dielectric layer.

[0063] In Figure 5 , the blue pixel 22-B has a supplementary anode 44-B separated from the anode 42-B by a portion of the dielectric layer 50. The blue pixel has a via 60 that extends through the dielectric layer to electrically connect the anode portion 44-B to the anode portion 42-B. This type of arrangement allows the dielectric layer 50 to have the same thickness in the pixels 22-R, 22-G, and 22-B. The thickness of the dielectric layer 50 can be selected mainly based on the adjustment of the anode stack of the pixel 22-B. Then, the thicknesses of the dielectric layer 52 and the supplementary anode 44 can be used to adjust the total thickness of the anode stacks of the pixels 22-R and 22-G.

[0064] If desired, the color filter elements can optionally be formed in Figure 4 and Figure 5above the pixels of the display. For example, a red color filter element may be formed above each red pixel 22-R, a green color filter element may be formed above each green pixel 22-G, and a blue color filter element may be formed above each blue pixel 22-B. If desired, the display may not include color filter elements.

[0065] Additionally, in Figure 4 and Figure 5 an example is shown in which a continuous OLED layer 45 is formed over the entire display. This example is merely illustrative. It should be understood that if desired, a pixel definition layer 66 and / or other structures may be used to create discontinuities in one or more of the OLED layers. Creating discontinuities in the OLED layers may prevent light leakage between pixels.

[0066] It should be understood that if desired, the Figure 4 and Figure 5 arrangements may be combined. For example, Figure 5 the display of Figure 5 may have a conductive layer 68 and no vias interposed between anode portions 42-B and 44-B, rather than having a dielectric layer that includes vias (e.g., Figure 4 the pixel 22-B in

[0067] In the example of Figure 4 the conductive spacer 68 is depicted as being formed only in the anode stack of the blue pixel 42-B. This example is merely illustrative. If desired, the red and / or green pixels may also include conductive spacers between the respective anode portions 42 and supplementary anode portions 44. Generally, any subset of the red, green, and blue pixels may include conductive spacers between the anode portions (and dielectric spacers may be omitted between the anode portions).

[0068] Figure 6 is a cross-sectional side view of an illustrative display in which the red, blue, and green pixels all have conductive spacers between the respective anode portions. For simplicity, the repetitive descriptions applicable to Figure 6 as well as one or more of the previous figures will not be repeated herein. In Figure 6 each pixel includes a transparent supplementary anode 44 similar to that in Figure 4 . However, in Figure 6In [the structure], the thicknesses of the supplementary anodes are different. For example, the supplementary anode 44-R may have a thickness different from (e.g., greater than) that of the supplementary anodes 44-G and 44-B. The supplementary anode 44-G may have a thickness different from (e.g., greater than) that of the supplementary anode 44-B. Using supplementary anodes 44 with varying thicknesses allows for optimizing the total optical cavity thickness 48 for each pixel type (e.g., pixel 22-R has an optical cavity thickness 48-R that maximizes the emission of red light, pixel 22-G has an optical cavity thickness 48-G that maximizes the emission of green light, and pixel 22-B has an optical cavity thickness 48-B that maximizes the emission of blue light), while allowing the OLED thicknesses 56-R, 56-G, and 56-B to remain substantially the same.

[0069] In Figure 6 [the structure], for each pixel, there is no intermediate dielectric layer between the transparent supplementary anode portion 44 and the anode portion 42. Instead, a conductive layer 68 may be interposed between the anode portions 42 and 44. As shown, the conductive layer 68-R is interposed between the anode portion 44-R and the anode portion 42-R, the conductive layer 68-G is interposed between the anode portion 44-G and the anode portion 42-G, and the conductive layer 68-B is interposed between the anode portion 44-B and the anode portion 42-B. The conductive layer 68 can electrically connect the corresponding anode portions 42 and 44 and can be in direct contact with the anode portions 42 and 44. The conductive layers 68-R, 68-G, and 68-B (sometimes referred to as conductive spacers) may be included to avoid incompatibility between the anode portions 44 and 42. The conductive layer 68 can also facilitate better electrical contact between the anode portions 44 and 42. For example, the transparent anode portion 44 may be formed of a material that corrodes when in direct contact with the material of the reflective anode portion 42 (e.g., the transparent anode portion 44 may be formed of ITO, while the reflective anode portion 42 may be formed of aluminum). In this example, the conductive spacer 68 can be interposed between the anode portions to prevent corrosion.

[0070] Each of the conductive layers 68-R, 68-G, and 68-B can be formed of titanium nitride (TiN) or another desired conductive material. Each of the conductive layers 68-R, 68-G, and 68-B can be thin enough to be approximately transparent (e.g., can have a thickness less than 10 nanometers, less than 5 nanometers, less than 3 nanometers, between 2 nanometers and 5 nanometers, between 1 nanometer and 6 nanometers, between 2 nanometers and 3 nanometers, between 1 nanometer and 3 nanometers, etc.). Each of the conductive layers 68-R, 68-G, and 68-B can transmit more than 80% of the incident light, more than 90% of the incident light, more than 95% of the incident light, more than 99% of the incident light, more than 99.9% of the incident light, etc. If desired, the conductive layers 68-R, 68-G, and 68-B can have a uniform thickness (as Figure 6) or may have different thicknesses.

[0071] Figure 6 An arrangement of the type shown has the following advantages: The deposition step of the Figure 4 and Figure 5 intermediate dielectric layer is omitted. Additionally, no conductive vias through the intermediate dielectric layer are required, thus allowing an increase in the pixel aperture ratio relative to when vias are needed. If the conductive material used to form the anode portions 42 and 44 is suitable for direct contact, the conductive spacer 68 may be omitted (e.g., omitted from any one of the red, green, and blue pixels). A via-less pixel design (e.g., all three pixels as in Figure 6 where there is no intermediate dielectric layer) can be used for all three pixel color types (as in Figure 6 ), one pixel color type (as in Figure 4 ), or any two pixel color types.

[0072] According to one embodiment, a display is provided that includes: a first pixel formed by a first anode, a cathode, and an organic light-emitting diode layer, the first anode including a first portion and a second portion, the second portion being electrically connected to the first portion and having a first thickness, and the first pixel having an optical cavity defined by a first distance between the first portion and the cathode; and a second pixel formed by a second anode, the cathode, and the organic light-emitting diode layer, the second anode including a third portion and a fourth portion, the fourth portion being electrically connected to the third portion and having a second thickness different from the first thickness, the second pixel having an optical cavity defined by a second distance between the third portion and the cathode, and the second distance being different from the first distance.

[0073] According to another embodiment, the organic light-emitting diode layer has a given thickness over the second portion of the first anode, and the organic light-emitting diode layer has the given thickness over the fourth portion of the second anode.

[0074] According to another embodiment, the first pixel includes a first dielectric layer and a second dielectric layer interposed between the first portion and the second portion of the first anode.

[0075] According to another embodiment, the first pixel includes a first via extending through the first dielectric layer and the second dielectric layer to electrically connect the first portion and the second portion of the first anode.

[0076] According to another embodiment, the second pixel includes the first dielectric layer and the second dielectric layer, and the first dielectric layer and the second dielectric layer are interposed between the third portion and the fourth portion of the second anode.

[0077] According to another embodiment, the second pixel includes a second via hole extending through the first dielectric layer and the second dielectric layer to electrically connect the third portion and the fourth portion of the second anode.

[0078] According to another embodiment, the first thickness is greater than the second thickness.

[0079] According to another embodiment, the first dielectric layer has a third thickness in the first pixel and a fourth thickness the same as the third thickness in the second pixel, and the second dielectric layer has a fifth thickness in the first pixel and a sixth thickness the same as the fifth thickness in the second pixel.

[0080] According to another embodiment, the display includes a third pixel formed by a third anode, the cathode, and the organic light-emitting diode layer. The third anode includes a fifth portion and a sixth portion. The sixth portion is electrically connected to the fifth portion and has a seventh thickness different from the first thickness. The third pixel has an optical cavity defined by a third distance between the fifth portion and the cathode, and the third distance is different from the first distance and the second distance.

[0081] According to another embodiment, the third pixel includes the first dielectric layer. The first dielectric layer is interposed between the fifth portion and the sixth portion of the third anode. The first dielectric layer has an eighth thickness the same as the third thickness and the fourth thickness in the third pixel. The first distance is greater than the second distance, the second distance is greater than the third distance. The organic light-emitting diode layer is a white organic light-emitting diode layer. The first pixel is a red pixel, the second pixel is a green pixel, and the third pixel is a blue pixel.

[0082] According to another embodiment, the display includes a third pixel formed by a third anode, the cathode, and the organic light-emitting diode layer. The third anode includes a fifth portion and a sixth portion. The sixth portion is electrically connected to the fifth portion and has a third thickness different from the first thickness and the second thickness. The third pixel has an optical cavity defined by a third distance between the fifth portion and the cathode, and the third distance is different from the first distance and the second distance.

[0083] According to another embodiment, the first pixel includes a first conductive layer interposed between the first part and the second part and in direct contact with the first part and the second part, the second pixel further includes a second conductive layer interposed between the third part and the fourth part and in direct contact with the third part and the fourth part, and the third pixel further includes a third conductive layer interposed between the fifth part and the sixth part and in direct contact with the fifth part and the sixth part.

[0084] According to one embodiment, a display is provided, the display including pixels, the pixels including: an anode including a first part formed of a first material and a second part formed of a second material different from the first material; a cathode; an organic light-emitting diode layer interposed between the second part of the anode and the cathode; and a conductive spacer formed of a third material different from the first material and the second material, the conductive spacer interposed between the first part and the second part of the anode and electrically connecting the first part and the second part of the anode, and the pixel having an optical cavity defined by a distance between the first part of the anode and the cathode.

[0085] According to another embodiment, the pixel is a first pixel, the anode is a first anode, and the display includes a second pixel, the second pixel including: a second anode including a third part and a fourth part; the cathode; the organic light-emitting diode layer interposed between the fourth part of the second anode and the cathode; and at least one dielectric layer interposed between the third part and the fourth part of the second anode.

[0086] According to another embodiment, the at least one dielectric layer includes a first dielectric layer, and the first dielectric layer is the only dielectric layer interposed between the third part and the fourth part of the second anode.

[0087] According to another embodiment, the display includes a third pixel, the third pixel including: a third anode including a fifth part and a sixth part; the cathode; the organic light-emitting diode layer interposed between the sixth part of the third anode and the cathode; and two dielectric layers interposed between the fifth part and the sixth part of the third anode.

[0088] According to another embodiment, the second pixel includes a first via hole extending through the first dielectric layer to couple the third portion of the second anode to the fourth portion of the second anode, the third pixel includes a second via hole extending through the two dielectric layers to couple the fifth portion of the third anode to the sixth portion of the third anode, and the first pixel does not include any dielectric layer between the first portion of the first anode and the second portion of the first anode.

[0089] According to another embodiment, the optical cavity is a first optical cavity and the distance is a first distance, the second pixel has a second optical cavity defined by a second distance between the third portion of the second anode and the cathode, the third pixel has a third optical cavity defined by a third distance between the fifth portion of the third anode and the cathode, the first distance is less than the second distance, and the second distance is less than the third distance.

[0090] According to one embodiment, a display is provided that includes a first pixel and a second pixel having a common cathode formed over an organic light emitting diode layer, wherein each of the first pixel and the second pixel includes: a first anode portion; a second anode portion contacting the organic light emitting diode layer, the organic light emitting diode layer having a thickness over the second anode portion of the first pixel and the organic light emitting diode layer having the thickness over the second anode portion of the second pixel; and at least one dielectric layer interposed between the first anode portion and the second anode portion, wherein the second anode portion of the first pixel and the second anode portion of the second pixel have different thicknesses.

[0091] According to another embodiment, the first anode portion of each of the first pixel and the second pixel is reflective and the second anode portion of each of the first pixel and the second pixel is transparent.

[0092] The foregoing is merely illustrative, and various modifications can be made by those skilled in the art without departing from the scope and essence of the embodiments. The foregoing embodiments can be implemented independently or in any combination.

Claims

1. A display including pixels, wherein the pixels include: An anode including a first portion and a second portion; At least one dielectric layer interposed between the first portion and the second portion; A cathode; And An organic light-emitting diode layer between the anode and the cathode, wherein the second portion is electrically connected to the first portion, and wherein the pixel has an optical cavity defined by the distance between the first portion and the cathode.

2. The display according to claim 1, wherein the pixel further includes: A via hole extending through the at least one dielectric layer to electrically connect the first portion and the second portion of the anode.

3. The display according to claim 2, wherein the pixel is a red pixel, the anode is a first anode, and the via hole is a first via hole, wherein the display includes green pixels and blue pixels, wherein the green pixels include a second anode and a second via hole, the second anode includes a third portion and a fourth portion, the second via hole electrically connects the third portion and the fourth portion of the second anode, and wherein the blue pixels include a third anode and a third via hole, the third anode includes a fifth portion and a sixth portion, the third via hole electrically connects the fifth portion and the sixth portion of the third anode.

4. A display including pixels, wherein the pixels include: An anode including a first portion and a second portion, wherein the first portion is more reflective than the second portion; A cathode; And An organic light-emitting diode layer between the anode and the cathode, wherein the second portion is electrically connected to the first portion, and wherein the pixel has an optical cavity defined by the distance between the first portion and the cathode.

5. The display according to claim 4, wherein the cathode is partially transparent and transmits less than 60% of light.

6. The display according to claim 4, wherein the second portion transmits more than 90% of light.

7. The display according to claim 6, wherein the first portion reflects more than 80% of light.

8. A display, including: Red, green, and blue pixels having a common cathode formed over an organic light-emitting diode layer, wherein each of the red, green, and blue pixels includes: A first anode portion; A second anode portion in contact with the organic light-emitting diode layer; At least one dielectric layer interposed between the first anode portion and the second anode portion; and A via hole extending through the at least one dielectric layer to electrically connect the first anode portion and the second anode portion.

9. The display according to claim 8, wherein the first anode portion of each of the red, green, and blue pixels is reflective, and wherein the second anode portion of each of the red, green, and blue pixels is transparent.

10. A display, including: A first pixel formed by a first anode, a cathode, and an organic light-emitting diode layer, wherein the first anode includes a first portion and a second portion, wherein the second portion is electrically connected to the first portion, and wherein the first pixel has an optical cavity defined by a first distance between the first portion and the cathode; A second pixel formed by a second anode, the cathode, and the organic light-emitting diode layer, wherein the second anode includes a third portion and a fourth portion, wherein the fourth portion is electrically connected to the third portion, wherein the second pixel has an optical cavity defined by a second distance between the third portion and the cathode, and wherein the second distance is different from the first distance; And A third pixel formed by a third anode, the cathode, and the organic light-emitting diode layer, wherein the third anode includes a fifth portion and a sixth portion, wherein the sixth portion is electrically connected to the fifth portion, wherein the third pixel has an optical cavity defined by a third distance between the fifth portion and the cathode, and wherein the third distance is different from the second distance.

11. The display according to claim 10, wherein the second portion has a first thickness, wherein the fourth portion has a second thickness different from the first thickness, and wherein the sixth portion has a third thickness different from the second thickness.

12. The display according to claim 11, wherein the first thickness is greater than the second thickness, and wherein the first distance is greater than the second distance.

13. The display according to claim 10, wherein the first pixel further includes a first conductive layer interposed between the first portion and the second portion and in direct contact with the first portion and the second portion.

14. The display according to claim 13, wherein the second pixel further includes a second conductive layer interposed between the third portion and the fourth portion and in direct contact with the third portion and the fourth portion, and wherein the third pixel further includes a third conductive layer interposed between the fifth portion and the sixth portion and in direct contact with the fifth portion and the sixth portion.

15. A display, comprising: Pixels, the pixels including: An anode, the anode including a first portion and a second portion; A cathode; An organic light-emitting diode layer, the organic light-emitting diode layer interposed between the second portion of the anode and the cathode; and A conductive spacer, wherein the conductive spacer is interposed between the first portion and the second portion of the anode and electrically connects the first portion and the second portion of the anode, and wherein the pixel has an optical cavity defined by a distance between the first portion of the anode and the cathode.

16. The display according to claim 15, wherein at least one of the first portion or the second portion is formed of a first material, and wherein the conductive spacer is formed of a second material different from the first material.

17. The display according to claim 15, wherein the first portion has a first reflectivity, and wherein the second portion has a second reflectivity different from the first reflectivity.

18. The display according to claim 15, the display further comprising: Additional pixels, the additional pixels comprising: An additional anode, the additional anode comprising a third portion and a fourth portion, wherein the organic light emitting diode layer is interposed between the fourth portion of the additional anode and the cathode; and An additional conductive spacer, wherein the additional conductive spacer is interposed between the third portion and the fourth portion of the additional anode and electrically connects the third portion and the fourth portion, and wherein the additional pixel has an additional optical cavity defined by an additional distance between the third portion of the additional anode and the cathode.

19. A display, comprising: Red, green, and blue pixels having a common cathode formed over an organic light emitting diode layer, wherein each of the red, green, and blue pixels comprises: A first anode portion; A second anode portion that contacts the organic light emitting diode layer; and A conductive layer interposed between the first anode portion and the second anode portion.

20. The display according to claim 19, wherein the first anode portion of each of the red, green, and blue pixels is reflective, and wherein the second anode portion of each of the red, green, and blue pixels is transparent.

Images