Split OLED with ESD protection

Abstract

A split bottom-emitting OLED device including an array of OLED segments disposed on a common transparent substrate, each segment forming an emissive area separated by a non-emissive gap, each OLED segment defined by a transparent bottom electrode segment, a light-emitting organic layer, and a top electrode, and in at least one OLED segment, between the bottom electrode and the substrate, a transparent insulating layer proximate the bottom electrode segment and a transparent conductive layer proximate the substrate.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS Reference is made to co-filed and commonly assigned PCT application PCT / US22 / 029409, entitled "SEGMENTED OLED," entitled "Segmented OLED," which claims the benefit of U.S. Provisional Patent Application No. 63 / 192,942, filed on May 25, 2021, with Attorney Docket No. OLWK-0024-PCT. [Background technology]

[0002] Electrostatic discharge (ESD) is the sudden and momentary flow of electrical current between two electrically charged objects. ESD can cause significant adverse effects in industry, including failure of electronic components. Electronic components can be permanently damaged when subjected to high voltages. For OLED devices, sensitivity to ESD can vary depending on the type of organic material used to emit light, with some materials and formulations being more sensitive than others. Highly sensitive electronic components must be protected during and after manufacturing, during shipping / handling, during device assembly, and in the finished device. ESD is often especially problematic when the device is in the "off" or non-operating state.

[0003] Some common methods of providing ESD protection to OLED devices include ESD protection as part of the driving circuitry (see, for example, U.S. Pat. No. 6,233,639), adding peripheral conductive structures (see, for example, U.S. Pat. No. 6,233,639), adding separate ESD protection circuitry (see, for example, U.S. Pat. No. 6,233,639), and using capacitors or transistors outside the light-emitting area (see, for example, U.S. Pat. No. 6,233,639). Such methods may or may not be useful when the device is in the "off" state. Due to the dielectric nature of electronic components and assemblies, it is not possible to completely prevent static electricity from building up during handling of the device. An efficient method of preventing ESD is to use materials that are not highly conductive but that slowly conduct or dissipate static electricity. Such dissipative materials are generally available in a range of 10 12They have a resistance of less than an ohm-meter. Such materials can conduct electricity, but they do so very slowly, so that built-up static charge can dissipate without a sudden discharge that could damage the internal structures of electronic devices.

[0004] Not all electronic devices are equally sensitive to ESD damage. It may depend on the application or environment involved. For example, electronic components assembled in a sealed module under controlled conditions may not be susceptible to ESD damage, but the same electronic components may be sensitive if handled manually. Furthermore, there are levels of ESD and some electronic components may be robust to low levels of ESD but sensitive to higher levels. In some applications (i.e. automotive), devices may be exposed to ESD in the range of 8kV or less. However, ESD voltages can be up to 30kV.

[0005] One way to prevent or suppress ESD is to incorporate capacitors into the device. See, for example, Non-Patent Document 1. Typically, capacitors are integrated with or placed near ESD sensitive components to absorb and then equalize or dissipate unwanted voltage spikes.

[0006] OLEDs consist of two area electrodes separated by a resistive organic layer and are a type of capacitor. Like other capacitors, their specific capacitance depends on the overlap area of ​​the two electrodes, the distance between the electrodes, the resistivity of the organic layer, and the type of material used, among other factors.

[0007] Ideally, the intrinsic capacitance of an OLED would be high enough to dissipate ESD without damaging the OLED or its associated circuitry. However, the intrinsic capacitance depends on the area size of the OLED, among other factors, so for large OLED devices (e.g., typically 25 cm 2OLEDs for typical lighting applications (e.g., OLEDs with areas greater than 1000 nm) may have a sufficiently high intrinsic capacitance to be relatively insensitive to ESD damage. ESD protection may not be necessary. Very small OLED devices (e.g., typically up to about 200-300 μm) may have a high enough intrinsic capacitance to be relatively insensitive to ESD damage. 2 The individual pixels of active and passive matrix OLED displays (having an area of ​​100 nm) have a relatively small intrinsic capacitance and can be very sensitive to ESD damage. However, because OLED displays already use complex control and drive circuitry, it is relatively simple to add external ESD protection as part of the circuitry.

[0008] OLED devices between these size extremes can be sensitive to ESD damage because their intrinsic capacitance is not large enough to effectively dissipate ESD, and they often have simple (usually off-substrate) control circuitry where adding ESD protection circuitry is problematic from the standpoint of cost and ease of manufacture. 2 OLEDs under 0.5cm 2 Sub-80 OLEDs are particularly susceptible to ESD damage without expensive or complex external protection mechanisms.

[0009] For some applications, multiple independently controlled individual OLED devices in this intermediate size range can be mounted on a single substrate to provide a "tiled" device, in which each individual OLED light source is prefabricated separately, entirely including its own substrate (except for the electrical connections), and then mounted side-by-side or in an array. "Tiled" devices can be expensive for manufacturers due to the complex assembly required.

[0010] In other applications, multiple independently controlled individual OLED devices may be fabricated directly on a single common substrate to provide a "split" OLED device. In particular, split OLEDs are fabricated directly on the same substrate, with each individual OLED segment fabricated completely side-by-side or in an array. There are non-emissive gaps or spaces between the individual segments. Such split OLED light sources can have manufacturing and cost advantages, since many layers can be shared between all the individual units, eliminating the need to handle and package separate OLED panels.

[0011] Segmented OLED devices can provide either variable general illumination (i.e., by powering individual segments according to the overall amount of light desired) or as low-resolution communication devices (i.e., by powering the segments in a pattern). However, in split OLED devices, the individual OLED segments are much larger than the OLED pixels of high-resolution displays. The OLED segments must be at least 0.025 cm 2 A minimum size of 0.05 cm is preferred. 2 This is by design, but because larger OLEDs produce more light in applications that don't require high resolution. Additionally, while the OLED pixels in a display require complex on-board drive circuitry to operate at high frequencies, split OLED devices operate at lower frequencies and can therefore use simpler off-board drive circuitry, thus reducing manufacturing cost and complexity.

[0012] Split OLED devices are particularly suited for automotive exterior lighting applications (e.g., tail lights) because, unlike LED devices, they do not require additional reflectors, light guides, or additional optical components to produce a homogenous surface light. See, for example, Non-Patent Document 2, Non-Patent Document 3, Non-Patent Document 4, Non-Patent Document 5, Non-Patent Document 6.

[0013] Applications such as automotive taillights often require some degree of side visibility in addition to being directly visible from behind, so taillight assemblies often have complex designs that include a mix of curved and relatively flat surfaces. Split OLED devices can be fabricated on flexible substrates, simplifying the design considerations for non-planar taillight assemblies. However, automotive taillight assemblies are a critical component of the overall appearance of the vehicle and must provide a sophisticated and consistent design and appearance.

[0014] Generally, OLED devices are formed on a substrate and can be either top-emitting (light emission from the surface opposite the substrate) or bottom-emitting (light emission through a transparent substrate). To create individually controlled OLED segments, at least one electrode must be divided into segments, i.e., the electrode of one OLED segment is electrically isolated from the corresponding electrode of a different OLED segment. In this way, light emission from each OLED segment can be individually controlled by a single unique electrical power feed (also called a bus line, bus bar, metal trace, conductive trace, lead, or current trace) to the electrode segment.

[0015] It is desirable to form the power leads directly on the substrate before applying the organic OLED layers. This is because each segment has at least one power lead and therefore must be patterned individually. One cost-effective way to fabricate the power leads is to use photolithography processes and techniques that can create very fine patterns of conductive structures. However, photolithography is generally not compatible for use on the organic OLED layers. Fine metal masking processes and techniques can be used to form power lines on top of the organic OLED layers, but they are more expensive and prone to defects during manufacturing. Also, the conductive structures created by masking processes are significantly larger than those that can be created by photolithography.

[0016] For bottom-emitting OLEDs with bottom split electrodes, it is desirable to place the individual power feeds connecting to each electrode segment at the same (horizontal) level as the electrode segments or below (between the electrode segments and the substrate). However, whatever location is chosen, there are trade-offs. The power feeds could be placed laterally adjacent to the electrode segments (separated by insulating material to maintain non-contact), but this can undesirably increase the space between the electrode segments (due to the number of individual power feeds required) and is prone to shorting between the power feed of one electrode segment and the power feed of a second electrode segment. The power feeds could be placed below the electrode segments, but must be electrically isolated from the electrode segments above them to avoid shorting. This can complicate manufacturing by requiring additional layers. Also, if the power feed is in the light emission path, it may be undesirable because it may be visible.

[0017] While both top- and bottom-emitting OLEDs are suitable for automotive applications, bottom-emitting OLEDs are preferred for at least two reasons. First, exterior applications require robust encapsulation. This is more difficult to achieve with the transparent encapsulant required for top-emitting OLEDs, especially for flexible OLEDs. Bottom-emitting OLEDs allow the use of very robust encapsulants, since the encapsulant on the non-emitting side does not need to be transparent. Second, OLEDs are installed in limited spaces, so heat build-up can be an issue. Bottom-emitting OLEDs allow the placement of a heat sink on the backside. With top-emitting OLEDs, the heat sink is located on the opposite side of the substrate, which reduces thermal conductivity and reduces cooling efficiency.

[0018] However, at least some of the OLED segments of a split device may be small enough to be sensitive to ESD damage, and because such small OLED segments may have only a simple direct electrical connection to off-substrate control circuitry, a need exists to provide low-cost, easy-to-manufacture ESD protection. Because ESD protection is needed even when the OLED device is not in operation or powered ("off") and not connected to other components, it is desirable for it to be passive on the substrate (i.e., not requiring a power source).

[0019] Non-Patent Document 7 describes a top-emitting split OLED device in which electrostatic protection is provided by a passive capacitor on the substrate of a continuous, opaque conductive layer (made of Cr / Al / Cr and opaque) as one electrode, an insulating layer (made of Al2O3 or ZrO2), and an anode segment (composition not disclosed) as the counter electrode. The continuous conductive layer located under all electrode segments is not connected to anything. The conductive layer is made of a conductive metal, which is not suitable for a bottom-emitting device. In addition, the opaque conductive layer is under all electrode segments. Such an arrangement may also be susceptible to manufacturing defects, especially short circuits between electrode segments due to pinholes in the insulating layer. This document does not disclose the location of the power feed, which is an important consideration.

[0020] Patent document 5 describes a bottom-emitting OLED display in which the driving circuit of each pixel includes a storage capacitor with a transparent anode / insulating layer / transparent conductive layer structure located in the light emission path. In this document, it is explained that the transparent conductive layer is patterned as a wiring line or patterned only under the anode. However, if the transparent conductive layer (the lower electrode of the capacitor) was part of the wiring line, the transparent conductive layer could not be connected to other pixels of the display because the transparent capacitor is part of the driving circuit of that pixel, and such a device would not be operable. Patent document 6 also describes a bottom-emitting OLED display in which the driving circuit of each pixel includes a storage capacitor with a transparent anode / insulating layer / transparent conductive layer structure. In this document, it is stated that the transparent storage capacitor also has a "retention capacitance", and if the "retention capacitance" is larger than the storage capacitance required for the operation of the OLED, the write voltage to the storage capacitor can be stabilized. Other documents describing bottom-emitting OLED displays in which the driving circuitry of each pixel includes a storage capacitor with a transparent anode / insulating layer / transparent conductive layer structure located in the light-emitting path include: U.S. Pat. No. 5,393,433; U.S. Pat. No. 5,493,663; U.S. Pat. No. 5,523,366; U.S. Pat. No. 5,611,633; U.S. Pat. No. 5,711,523; and U.S. Pat. No. 5,711,523. However, in all the above documents, the transparent capacitor is part of the driving circuitry and is the same size as the pixel, so it may not increase the overall capacitance enough to prevent ESD damage.

[0021] US Pat. No. 5,993,336 and US Pat. No. 5,993,363 describe split OLEDs with conductive tracks that extend through the device and contact the hole injection track. US Pat. No. 5,993,336 also describes the use of conductive tracks that vary in thickness (height) or width from the outer segment to the inner segment to address the IR drop issue. A similar concept of conductive layers with thickness variations to address IR drop is disclosed in US Pat. No. 5,993,336.

[0022] US Pat. No. 5,399,433 describes a segmented OLED with conductive tracks arranged between the segments.

[0023] US Pat. No. 5,399,633 describes an OLED with conductive tracks, in which the OLED electrodes and the conductive tracks are all transparent. [Prior art documents] [Patent documents]

[0024] [Patent Document 1] U.S. Patent No. 10692957B2 [Patent Document 2] U.S. Patent No. 7944140B2 [Patent Document 3] U.S. Patent No. 9246121B2 [Patent Document 4] U.S. Patent No. 6,046,547A [Patent Document 5] U.S. Patent No. 8,445,910 [Patent Document 6] U.S. Patent No. 10825883B2 [Patent Document 7] U.S. Patent No. 10446633B2 [Patent Document 8] Chinese Patent No. 109244107B Specification [Patent Document 9] U.S. Patent No. 9601553B2 [Patent Document 10] US Patent No. 20150214249A1 [Patent Document 11] U.S. Patent No. 9385171B2 [Patent Document 12] Chinese Patent No. 109166895B Specification [Patent Document 13] Chinese Patent No. 109119440B Specification [Patent Document 14] U.S. Patent No. 8,102,476 B2 [Patent Document 15] U.S. Patent No. 8,941,143 [Patent Document 16] U.S. Pat. No. 9,487,878 [Patent Document 17] U.S. Patent No. 9,159,945 [Patent Document 18] U.S. Pat. No. 10,068,958 [Patent Document 19] U.S. Patent No. 9,627,643 [Non-patent literature]

[0025] [Non-Patent Document 1] https: / / www.vishay.com / docs / 45257 / vishayautomlccsesdprotect.pdf [Non-Patent Document 2] M. Kruppa et al, Information Display 4 / 19, p.14-18(2019) [Non-Patent Document 3] H. Bechert et al, “Flexible and highly segmented OLED for automotive applications”, Proc. SPIE10687, Organic Electronics and Photonics: Fundamentals and Devices, 106870Q(21 May 2018) [Non-Patent Document 4] M.Kondakova et al,8-1:Invited Paper:Development of High-Temperature Stable Red OLEDs for Automotive Lighting.SID Symposium Digest of Technical Papers,51:83-85(2020) [Non-Patent Document 5] C.May, “Flexible OLED lighting and signage for automotive application,”2021 28th International Workshop on Active-Matrix Flatpanel Displays and Devices(AM-FPD),2021,pp.42-45 [Non-Patent Document 6] DQChowdhury et al, “Application of OLED for Automotive Lighting,”2019 26th International Workshop on Active-Matrix Flatpanel Displays and Devices(AM-FPD),2019,pp.1-3 [Non-Patent Document 7] H.Bechert et.al, “Thin-Film Electrostatic Discharge Protection for Highly Segmented OLEDs in Automotive Applications”, Adv.Mater.Technol.,4,1800696(2019), along with an analogous communication in Adv.Mater.Technol. Summary of the Invention [Problem to be solved by the invention]

[0026] Bottom-emitting split OLED devices having at least one small OLED segment need to be protected from ESD damage, and protection needs to be provided even when the device is not operating. [Means for solving the problem]

[0027] A split bottom-emitting OLED device comprising an array of OLED segments disposed on a common transparent substrate, the array comprising each OLED segment forming an emissive area separated by a non-emissive gap, each OLED segment being defined by a transparent bottom electrode segment, a light-emitting organic layer, and a top electrode, wherein in at least one OLED segment, between the bottom electrode segment and the substrate, there is a transparent insulating layer proximate to the bottom electrode segment and a transparent conductive layer proximate to the substrate, the overlapping area of ​​the bottom electrode and the conductive layer forming an associated passive capacitor structure, the bottom electrode of the OLED segment being the top electrode of the passive capacitor structure, the insulating layer being the dielectric of the passive capacitor structure, and the conductive layer being the bottom electrode of the passive capacitor structure.

[0028] In the above OLED devices, the conductive layer is patterned. The conductive layer can be patterned into two or more sections that are electrically isolated from one another.

[0029] In any of the above OLED devices, the overlap area of ​​the conductive layer section(s) and the bottom electrode segment in at least one OLED segment increases the total capacitance of the OLED segment by at least 0.2 nanofarads (nF).In any of the above OLED devices, the overlap area of ​​the conductive layer section(s) and the bottom electrode segment in at least one OLED segment is 30% or more of the area of ​​the bottom electrode segment.

[0030] In any of the above OLED devices, in addition to the OLED segments having an associated passive capacitor structure, the bottom electrode segment of at least one distinct OLED segment in the array has no overlap with the conductive layer section, such that the at least one distinct OLED segment does not have an associated passive capacitor structure. The size of the at least one distinct OLED segment without a passive capacitor structure is less than 1.0 cm. 2 It could be more than that.

[0031] In any of the above OLED devices, the bottom electrode of each OLED segment in the array is electrically connected to a dedicated power feed that controls light emission, the power feed being disposed laterally between the bottom electrode segments and electrically isolated from the other power feeds and from any independent electrode segments.

[0032] In any of the above OLED devices, the bottom electrode segments of each OLED segment in the array are electrically connected to a single power feed that controls light emission, the power feed being disposed laterally between the conductive layer sections and electrically isolated from the other power feeds and the conductive layer sections, and electrically isolated from the bottom electrode segments of any individual OLED segments by the insulating layer. A dedicated power feed may be connected to a corresponding bottom electrode segment through a via in the insulating layer. In any of these OLED devices, at least one of the power feeds is positioned to pass under at least one bottom electrode segment in the light-emitting area of ​​the individual OLED segment.

[0033] In any of the above OLED devices, there are a plurality of power feeds beneath the bottom electrode segment of at least one independent OLED segment, the overlap between all of the power feeds and the bottom electrode of the independent OLED segment forming an associated passive capacitor structure, the bottom electrode segment being the top electrode of the passive capacitor structure, the insulating layer being the dielectric of the passive capacitor structure, and the plurality of power feeds collectively being the bottom electrode of the passive capacitor structure. In at least one independent OLED segment, the overlap area of ​​the plurality of power feeds of the associated passive capacitor structure with the bottom electrode segment increases the total capacitance of the independent OLED segment by at least 0.2 nF, or the total overlap area of ​​the combined power feeds of the associated passive capacitor structure of the independent OLED segment with the overlying bottom electrode is 30% or more of the area of ​​the bottom electrode segment. Effect of the Invention

[0034] The bottom-emitting split OLED device described provides a transparent passive capacitor structure on the substrate located in the light-emitting path of the OLED segment that has sufficient capacitance to provide protection against electrostatic discharge in combination with the intrinsic capacitance of the associated OLED segment. This not only provides ESD protection in the unpowered state, but also maximizes the total light-emitting area of ​​the device by locating the passive capacitor structure directly under the split electrode. [Brief description of the drawings]

[0035] [Figure 1A] FIG. 1 is a top view of a split OLED device 100 of the present invention having five segments with a conductive layer that is the bottom electrode of a passive capacitance located under all of the OLED segments. The power feeds are disposed laterally of the electrode segments. [Figure 1B] 1 is a cross-sectional view of a segmented OLED device 100. FIG. [Figure 1C] 1 is a circuit diagram of a split OLED device 100. FIG. [Figure 2A] 2 is a top view of a split OLED device 200 of the present invention having five segments with a conductive layer that is the bottom electrode of a passive capacitance located under some of the OLED segments. The power feeds are disposed laterally of the electrode segments. [Figure 2B] 2 is a cross-sectional view of a segmented OLED device 200. FIG. [Figure 3A] FIG. 3 is a top view of a split OLED device 300 of the present invention having five segments with a conductive layer that is the bottom electrode of a passive capacitance and overlaps a portion of the OLED segments. The power feeds are disposed laterally of the electrode segments. [Figure 3B] FIG. 3 is a cross-sectional view of a segmented OLED device 300. [Figure 4A] FIG. 4 is a top view of a split OLED device 400 of this invention having five segments with a conductive layer that is the bottom electrode of a passive capacitance and that is disposed under a portion of the OLED segment along with a power feed. [Figure 4B] 4 is a cross-sectional view of a split OLED device 400. FIG. [Figure 5A] FIG. 5 is a top view of a split OLED device 500 of the present invention having seven segments with a conductive layer that is the bottom electrode of a passive capacitance and is disposed under a portion of the OLED segment with a power feed, a portion of the power feed passing under the split electrode without electrical contact. [Figure 5B] 5 is a cross-sectional view of a segmented OLED device 500. FIG. [Figure 6A] FIG. 6 is a partial top view along one side of a split OLED device 600 in which multiple power feeds pass under the split electrodes without electrical contact. [Figure 6B] 6 is a partial cross-sectional view of a split OLED device 600. FIG. [Figure 7] FIG. 10 is a cross-sectional schematic diagram of a two-stack OLED formulation 1000. [Figure 8] This is a test circuit for measuring ESD sensitivity.

[0036] The figures are not to scale. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] For purposes of this disclosure, the terms "over" or "above" mean that the relevant structure is located above another structure, i.e., opposite the substrate. "Top" or "upper" refers to the side or surface furthest from the substrate, and "lower", "lowest", "lower", "under" or "bottom" refers to the side or surface closest to the substrate. Unless otherwise noted, "over" should be interpreted as either the two structures may be in direct contact or there may be an intermediate layer between them. "Layer" should be understood to mean that a layer has two sides or surfaces (top and bottom), that there may be multiple layers, and is not limited to a single layer. "LEL" always refers to a single light-emitting layer. "Unit" generally refers to at least one layer that can be considered to act as one single light source, and a unit may equate to a single LEL, may include one LEL associated with other non-emissive layers, or may have multiple LELs with or without additional layers. A light-emitting unit is a group of one or more LELs separated from another light-emitting unit by a charge-generating layer (CGL). Therefore, if an OLED device does not have a CGL, there is only one light-emitting unit, even if it can have multiple LELs. Such a device is often called a "one-stack" device. If an OLED device has two light-emitting units separated by a CGL, it can be called a "two-stack" device. A stacked OLED can have multiple units or a combination of units and LELs that together make up the total light emission.

[0038] R or "red" indicates a layer or unit that emits primarily red light (>600 nm, preferably in the range 620-660 nm), G indicates a layer or unit that emits primarily green light (500-600 nm, preferably in the range 540-565 nm), and B indicates a layer or unit that emits primarily blue light (<500 nm, preferably in the range 440-485 nm). It is important to note that R, G, and B layers may emit some light outside the ranges indicated, but the amount is always less than the primary colors. Y (yellow) indicates that the layer or unit emits a large amount of both R and G light, and a significantly smaller amount of B light. Unless otherwise noted, wavelengths are expressed in vacuum, not in situ.

[0039] The OLED light emitting elements of the present invention may be a single LEL, a one-stack OLED, a two-stack OLED, or three or more OLED stacks and may emit a single color or multiple colors. If a monochromatic light output is desired or if the color temperature of the light output needs to be adjusted or changed, color filters may be used to remove unwanted wavelengths.

[0040] An OLED light-emitting LEL or unit can produce a single "color" of light (i.e., a mixture of two primary colors, such as R, G, B, Y, or cyan, or W). An individual OLED light-emitting unit may have a single light-emitting layer or may have multiple light-emitting layers (either directly adjacent to each other or separated from each other by intermediate layers). An individual light-emitting unit may also include various types of non-emissive layers known in the art, such as hole-transporting layers, electron-transporting layers, blocking layers, etc., to facilitate light emission and provide desired effects such as managing charge transfer across the light-emitting unit. A single color of light can be produced in an OLED unit by a single layer with one or more emitters of the same color, or by multiple layers each with the same or different emitters whose primary emission falls within the same color. The single color provided by the OLED unit may be a combination of two primary colors, in particular a yellow-emitting OLED unit that produces a combination of R and G light. In this case, yellow counts as a single color.

[0041] Stacked OLED devices can produce light of a single color or more than one color (multimodal). For example, multimodal OLEDs produce white light with roughly equal amounts of R, G, and B light. Generally, the CIE x , CIE y corresponds to a value of approximately 0.33,0.33. White light can generally be produced in an OLED by having three separate R, G, B emitting layers, two separate emitting layers such as blue and yellow, or even a single white emitting layer, even though it does not contain equal amounts of R, G, B light. Red-emitting OLEDs are generally classified as having a red emitting layer, which is the CIE x , CIE y The value of is about 0.6 to 0.7, and 0.2 to 0.35. The OLED of the present invention may utilize the microcavity effect to increase the emission of light of the desired color.

[0042] In certain applications, such as automotive tail lights used to signal braking, stopping, turning, and other functions, the light output of the OLED used must be selected to meet all government regulations and SAE or industry standards applicable to that application, particularly in terms of color and brightness. Additionally, the size and dimensions of the split OLED device must be selected to conform to all appropriate government regulations and industry standards applicable to the particular application. In such tail light applications, the preferred emission color is red.

[0043] A split OLED device, consisting of multiple individual OLED segments on a common substrate, can have any shape as desired. The split OLED device can be entirely flat or planar, have multiple planar surfaces angled relative to one another, entirely curved, or a mixture of planar, angled, and curved surfaces. The split OLED device is often mounted in a housing or part of a module, along with the necessary external power connections and control elements to provide signals or power to the individual segments. The housing or module will usually have a transparent portion that transmits the light of the OLED device and protects it from the outside environment. The housing or module may also have an internal reflector or light guide to direct the light emission as desired. The entire housing or module containing the split OLED device can be hermetically sealed.

[0044] In a split OLED device, each individual OLED segment desirably has uniform emission across the active area of ​​the segment, is not subdivided, and is powered by a single source (power feed) and signal. Split OLED devices with individually controlled segments arranged in an array may be used for lighting purposes, where all segments are activated simultaneously to provide uniform emission (except for gaps between segments). The emission of all segments may be constant, dimmed all at once, brightened all at once, or blinking. Alternatively, split OLED devices may have each segment activated individually and independently in some pattern. This pattern may encompass some segments being fully lit, some segments being at intermediate brightness levels, and some segments being off. The pattern may be constant over a period of time, or may vary such that individual segments are turned on and off in some time-based or location-based sequence. Because split OLED devices are not high-resolution displays, and are typically intended to be viewed from a significant distance, the individual OLED segments may be activated in a similar manner to the individual pixels (typically emitting areas of 0.1 mm) of a high-resolution display. 2Preferably, the total light-emitting area is 500 cm 2 For the small split OLED devices below, the individual OLED segments are at least 0.025 cm 2 , preferably at least 0.05 cm 2 It is desirable for the total light-emitting area to be 500 cm 2 For larger split devices, the individual OLED segments are at least 0.05 cm 2 , more preferably at least 0.5 cm 2 The light emitting area should be 100 mm.

[0045] The individual OLED segments can be of any shape or area as desired. In general, the segments form a packed array to minimize the non-emitting space between the individual segments. Desirably, the array is a regular array so that the spacing between the segments is uniform, providing a smooth appearance. The array can take any overall form in terms of shape, and does not have to be square or rectangular, but can be circular, elliptical, triangular, or polygonal. In some designs, some areas of the array are regular with uniform spacing between each other, and another part of the array is irregular. For example, in a square array, the outside of the array can have smaller square segments arranged in a uniform pattern, while the inner area has one larger star-shaped segment right in the middle, surrounded by a larger non-emitting area. Similarly, the shape of the individual OLED segments in the array is not limited, but can be square, rectangular, circular, elliptical, triangular, or polygonal, or even irregular as desired.

[0046] Furthermore, the OLED segments in the array need not all be the same shape, but may have a mixture of shapes, such as interlocking triangles and hexagons. Preferred are packed arrays of only triangles, only parallelograms, or a mixture of triangles and hexagons or triangles and trapezoids. The areas of the individual segments need not all be the same, and the array may be comprised of a mixture of large and small segments. The individual segments in the array need not all emit the same color (although each individual segment emits a single color), and segments emitting different colors may be arranged in a particular pattern in the array. Desirably, the array of segments is asymmetric, i.e., includes segments of different sizes, and more desirably, the array includes segments of different sizes and shapes.

[0047] 1A is an overhead view of a split OLED device 100. There are five different OLED segments 1', 2', 3', 4' and 5', as defined by transparent electrode segments 1, 2, 3, 4 and 5. In this example, OLED segment 5' is 1 cm 2 The area of ​​segments 1' to 4' is greater than 1 cm 2OLED segments 1'-5' are arranged in an asymmetric array on a transparent substrate 10, with the outer edges of the array representing the light-emitting area of ​​the split OLED device 100. On top of the transparent substrate 10 is a uniform transparent conductive layer 20 and a uniform transparent insulating layer 30. Both 20 and 30 are unpatterned. On top of the insulating layer 30 are power feed 15 electrically connected to electrode segment 1, power feed 25 connected to electrode segment 2, power feed 35 connected to electrode segment 3, power feed 45 connected to electrode segment 4, and power feed 55 connected to electrode segment 5, all occupying the same lateral plane. Between the electrode segments and between adjacent power feeds or between adjacent electrode segments and power feeds is an electrically insulating pixel defining layer (PDL) 40. Because the power feeds may not be as thick as the electrode segments, a PDL 40 may also be deposited on top of the power feeds to planarize the top surface of the PDL / electrode segment layer. There should be no electrical contact between any of these electrode segments and the power feeds, except for the contacts between the electrode segments and their designated power feeds. On the surface of the PDL 40 / electrode segments 1-5 is a top electrode 60, common to the light-emitting organic layer 50 (not shown in this view). On top of the electrode 60 is an encapsulation layer 70. One end of each power feed as well as the top electrode 60 extends outside the encapsulation 70 to form a contact pad for individual connection to control circuitry for the split OLED device 100. Between the OLED segments (and within the light-emitting area of ​​the array) are non-emitting gaps or spaces 80, which typically correspond to the location of the PDL 40.

[0048] FIG. 1B shows a cross-section of split OLED device 100 along line Z-Z' in FIG. 1A. Visible in this view are light-emitting organic layer 50, a continuous top electrode 60 that is common to all OLED electrode segments 1-5 and extends beyond encapsulant 70 on one side to form an external contact pad for connection to control circuitry. Arrows indicate the direction of light emission from individual OLED segments 1'-5'. In this embodiment, power feeds 15, 25, 35, 45 and 55 are shown as being thinner than the electrode segments, and their top surfaces are covered by PDL 40 to form a flat top surface across the electrode segments and the PDLs located between the electrode segments. Between electrode segments (e.g., between 3 and 5), PDL 40 provides a non-emitting gap 80.

[0049] The OLED structures of OLED segments 1'-5' (bottom electrode segments (1-5) / organic layer (50) / common top electrode (60)) are each capacitor structures with an associated intrinsic capacitance. The intrinsic capacitance (C OLED ) depends on the size of the bottom electrode segments, among other factors, since the top electrode 60 is common to all. OLED refers only to the light-emitting OLED portion of the OLED segment (top electrode to bottom electrode).

[0050] In the split OLED device 100, the substrate side of the electrode segments 1-5 has an insulating layer 30 and a conductive layer 20, which are all continuous and uniform on the top surface of the transparent substrate 10. This allows for the formation of a multi-planar capacitor structure within a single OLED segment, where there is a top OLED capacitor structure consisting of a top electrode / organic layer (dielectric) / bottom electrode segment, and a bottom passive capacitor structure consisting of a bottom electrode segment / insulating layer (dielectric) / conductive layer. It is important to note that even though the conductive layer 20 is not directly electrically connected to any portion of the OLED structure above it, it can still function as the bottom electrode of the passive capacitor structure since the conductive layer is common to other OLED segments. In the split OLED device 100, the capacitance (C PASSIVE ) depends on, among other factors, the size of the bottom electrode segment of the OLED since the conductive layer 20 is common to all. In this embodiment, the vertical overlap of the bottom electrode segment with the conductive layer is 100% of the electrode segment.

[0051] In the split OLED device 100, five passive capacitor structures are formed, one for each OLED segment 1'-5' whose conductive layer overlaps with the individual electrode segments 1-5. These five passive capacitor structures are connected in parallel with each other, share the same conductive layer 20 (bottom electrode) and insulating layer 30 (dielectric), and differ only by the different OLED electrode segments. Even though the common conductive layer 20 is shared between the different OLED segments, the passive capacitor structure of any one OLED segment follows the overlap between the bottom electrode of the OLED and only the portion of the conductive layer directly under that bottom electrode. In the OLED segments of the present invention, the OLED (as a capacitor structure) and the passive capacitor structure are directly related to each other since both structures share the bottom electrode of the OLED. The conductive layer 20 (which is the bottom electrode of the passive capacitor structure) is not directly connected to any circuit.

[0052] 1C is a circuit diagram of a split OLED device 100 in which the OLED segments are connected to a control circuit 95 via power feeds 15, 25, 35, 45 and 55. In operation, the control circuit can independently activate the OLED segments 1'-5' as desired. In the unpowered state, each of the five OLED segments 1'-5' has a single capacitor portion with an individual intrinsic capacitance C O1’ ~C O5’ and a capacitor portion having an individual capacitance C P1’ ~C P5’ The bottom electrode segment (i.e., 1 in OLED segment 1') serves as both the bottom electrode of the OLED structure and the top electrode of the passive capacitor structure. The bottom electrode of the passive capacitor structure is conductive layer 20, which is common to the passive capacitor structures of the other OLED segments. Within an individual OLED segment, the OLED structure and the associated passive capacitor structure are connected in series, and the capacitance of that OLED segment as a multiplanar capacitor is C OLED * C PASSIVE / (C OLED +C PASSIVE )

[0053] However, the lower electrode (conductive layer 20) of the passive capacitor structure of one OLED segment is common to the passive capacitor structures of other OLED segments, so that the C PASSIVE is connected in parallel with all other OLED segments that share the same conductive layer. Therefore, the C PASSIVE is also the capacitance of the passive capacitor structure of the individual OLED segment plus the sum of all the capacitances of the other OLED segments.

[0054] Static charge on a device such as OLED device 100 can be generated and subsequently discharged via several paths. Charge can come from the top or from below the device. Charge from above encounters top electrode 60. Charge from below passes through substrate 10 and encounters conductive layer 20. In either case, top electrode 60 or conductive layer 20 distributes the electrostatic charge over a significant area, making discharge across multiple segments of OLED device 100 (i.e., across a parallel array of multiplanar capacitors as described above) less likely to damage the device.

[0055] A more problematic path for static charging and discharging is when an individual bottom electrode becomes charged. This can originate elsewhere in the device and be carried by a power feed (e.g., 15) to the corresponding bottom electrode segment (e.g., 1). The danger with this path is that a static charge on a single bottom electrode segment can likely be discharged, without mitigation factors, through a single OLED segment, or at most a few adjacent OLED segments, potentially damaging those OLED segments. Thus, for the purposes of this invention, the static charge is assumed to originate entirely on the bottom electrode segment, and the capacitance of the corresponding OLED segment is determined by the capacitance available to the bottom electrode, i.e., across the capacitance of the OLED structure of 1' (C OLED ), and across the capacitance provided by the passive capacitor structure including the bottom electrode 1, the conductive layer 20, and the intervening dielectric layer (C PASSIVE ), where the conductive layer 20 is common to the passive capacitor structures of the other OLED segments, so C P1’ In Figure 1C, this is connected in series with a parallel array of other capacitances, and then C P1’ OLED segments 2' through 5' are shown connected in series.

[0056] In general, for an array of n OLED segments (assuming equal size), the overall total capacitance (C T ) is the capacitance (C OLED ) and the capacitance of a passive capacitor structure in series with the capacitance of the other n-1 OLED segments arranged in parallel (C PASSIVE ) and each of the n-1 OLED segments has a C OLED and C. PASSIVE and are connected in series. The total effective capacitance (C T ) is calculated using the following formula: C T =C OLED +C PASSIVE ×[(n-1)·C OLED / (C PASSIVE +n·C OLED )] It should be noted that as the number of segments becomes large, the added capacitance due to the passive capacitor structure can be approximated by the value added to a single OLED segment. C T ~C OLED +C PASSIVE (When n is large) For arrays of unequal sized OLEDs, the capacitances are summed individually, but if n is large enough, they can still be approximated by the sum over one average OLED segment.

[0057] Since the size of the OLED segments is selected primarily to meet the light emitting objectives and requirements of the device, the inherent capacitance may be insufficient to protect against ESD damage, and this capacitance can be increased in the array by adding passive capacitor structures between the OLED segments to form an array of OLED segments, with at least some of the OLED segments each associated with a passive capacitor structure. The addition of the passive capacitor structures increases the total capacitance, which reduces susceptibility to ESD damage. Because the total capacitance of the OLED segments has been increased by the addition of the passive capacitor structure(s), electrostatic charges can be better dissipated, which can mitigate damage to the organic layers of the overlying OLED structure.

[0058] In particular, the passive capacitor structure(s) should increase the total capacitance of the OLED segment compared to the same OLED segment without the passive capacitor structure. This additional capacitance should be sufficient to provide the desired level of protection against ESD damage. The susceptibility of an OLED to ESD damage is determined by V LIM This depends on the voltage limit at which damage to the OLED is expected. LIM is an OLED formulation specific property, can vary significantly between different OLED formulations, and is independent of the size of the OLED. LIM can be experimentally determined. Increasing the capacitance of the entire OLED segment reduces the voltage the OLED sees from an electrostatic discharge, so the voltage seen by the OLED is V LIM Therefore, when added to the intrinsic capacitance of the OLED portion of the segment, the total capacitance provided by the passive capacitor structure(s) is kept below V LIM It is desirable to increase the total capacitance of the OLED segments so that it remains below

[0059] The area (size) of an individual OLED segment is important in determining its susceptibility to ESD damage. Typically, an emitting area of ​​1.0 cm 2 These larger segments have enough inherent capacitance to dissipate ESD without damage. 2 Below, especially 0.5 cm 2 The following OLED segments may be more susceptible to ESD damage because they do not have as high an intrinsic capacitance. Thus, in a split OLED device having segments of different sizes, it may not be necessary to provide additional ESD protection for the larger segments by adding associated passive capacitor structures. For example, OLED segment 5' of split OLED device 100 may have a large ESD capacitance due to its size (>1 cm 2 ), ESD protection may not be necessary, but segments 1'-4' still require protection. Additionally, the presence of passive capacitor structures with the monolithic common conductor layer as the bottom electrode can degrade the response time (frequency) of the OLED. Patterning the conductive layer into smaller sections can minimize this degradation.

[0060] This protective arrangement is illustrated in FIGS. 2A and 2B, which are top and cross-sectional views, respectively, for an OLED device 200 similar to split OLED device 100, but where the passive capacitor structures are not present under all of the electrode segments. In particular, rather than being continuously present under all of the OLED segments, conductive layer 20 is patterned to be present under OLED segments 1'-4' but not under 5'. Instead, another insulating layer 31 is added under electrode segment 5. Insulating layer 31 is also transparent and may be the same as or different from insulating layer 30. In this way, the total capacitance of the smaller OLED segments 1'-4' is increased in a similar manner as described for split OLED device 100, while the capacitance of the larger OLED segment 5' is relatively unaffected. In this embodiment, the vertical overlap of bottom electrode segments 1-4 and conductive layer 20 in OLED segments 1'-4' is 100%.

[0061] In split OLED device 100 and split OLED device 200, a third capacitor structure is also formed between the power leads that are laterally separated from the bottom electrode segments to which the power feeds are not connected. For example, power feed 25 is laterally separated from bottom electrode segment 1 by PDL 40. Because power feed 25 is not connected to electrode segment 1 (power feed 25 is connected to electrode segment 2), this forms a passive capacitor structure. The power feed carries current during operation of the OLED device, but is not powered when the device is not operating (when ESD protection is required), allowing it to passively dissipate ESD. However, because both the power feed and the bottom electrode are thin, the overlapping area between the side of the power feed and the side of the bottom electrode segment is relatively small, resulting in a small capacitance, making its contribution to the total capacitance in this case negligible.

[0062] In both split OLED device 100 and split OLED device 200, the relative area of ​​overlap (if present) between the bottom electrode segments and the underlying conductive layer 20 forming the passive capacitor structure is 100%. That is, the conductive layer 20 providing the passive capacitor structure is equal to or larger in area than the corresponding electrode segment. The relative area of ​​the conductive layer 20 forming the passive capacitor structure can be less than 100% of the corresponding bottom electrode segment, since it is only necessary to increase the total capacitance to a level sufficient to provide ESD protection. Even though the capacitance will be less than if the relative overlap area were 100%, the total capacitance, when added to the intrinsic capacitance of the OLED, may be sufficient to prevent ESD damage.

[0063] This is illustrated in Figures 3A and 3B, which are top and cross-sectional views, respectively, of a split OLED device 300 similar to split OLED device 200, but in which the electrode segments have less than 100% overlap area with the conductive layers forming the second passive capacitor. In particular, conductive layer 20 is patterned to have a 50% overlap area (90) with each of bottom electrode segments 1-4, i.e., conductive layer 20, which forms the lower electrode of the passive capacitor structure, overlaps only about 50% with each of the overlying electrode segments 1-4, which form the upper electrode of the passive capacitor structure.

[0064] The amount of overlap between the conductive layer and the bottom electrode segment is related to the capacitance that the passive capacitor provides. Ideally, the overlap area between the conductive layer and the electrode segments forming the passive capacitor structure should be at least 30% or more to provide a significant amount of capacitance. That is, the area of ​​the conductive layer that overlaps with the electrode segment (which is the top electrode of the second capacitor structure) or the total area of ​​all conductive layer sections present is at least 30% of the area of ​​the electrode segment. More preferably, the overlap area is at least 50% or more, and most preferably at least 70% or more.

[0065] In some examples of split OLED devices, it may not be desirable to place the power feeds between and laterally away from the electrode segments. Such an arrangement may be prone to shorting due to manufacturing defects. Furthermore, depending on the layout, overall size, and number of OLED segments, it may not be possible to fit all the necessary power leads (at least one per OLED segment) within the available distance between the OLED segments (non-emitting gaps). Some power feeds may be too wide (to minimize IR drop along their length) and may not fit within the available gap distance. In such cases, the power feeds may be placed below the plane of the electrode segments and above the transparent substrate.

[0066] 4A shows a top view of a split OLED device 400 in which the power feeds are located between the plane of the electrode segments and the transparent substrate, but are not coplanar with the electrode segments. In particular, power feeds 15, 25, 35, 45, 55 are disposed on transparent substrate 10 in the same lateral plane as the conductive layers. In this example, the conductive layers are patterned into two separate conductive layers 22 and 24. Power feed 15 is separated from electrical contact with conductive layer 22 by insulating layer 31 in the form of a slot in 22. Power feeds 25 and 45 are located in the space between 22 and 24, and are separated from electrical contact by insulating layer 31. Power feeds 35 and 55 are separated from electrical contact with conductive layer 24 by insulating layer 31 in the form of a slot in 24 (which may be the same as or different from insulating layer 30). In no case are the power feeds in electrical contact with any portion of the conductive layers. The power feeds contact the appropriate electrode segments through vias that pass through insulating layers 30 and / or 31 .

[0067] 4B shows a cross section of split OLED device 400 along line Z-Z'. In split OLED device 400, power feeds 25 and 45 are located directly beneath the non-emissive spaces between the electrode segments and are therefore not in the light-emitting path. Power feeds 15, 35, 55 are connected to electrode segments 1, 3, and 5 through vias 32 in insulating layer 30 (vias for power feeds 25, 45 not shown).

[0068] However, this is not always possible because there may not be enough space in the non-emitting space 80 for the number of power feeds required. In this case, it is necessary to place at least some of the power feeds below the electrode segments in the same plane as the conductive layer. An insulating layer 30 is located on the top surface of the conductive layer and between any power feeds and the bottom surface of the electrode segments, and prevents electrical contact between the power feeds and any electrode segments that the power feeds do not control.

[0069] Because it is not always possible to route all of the power feeds under the non-emissive gaps between electrode segments, it may be necessary to route at least a portion of the power feeds under (and electrically insulate) one or more of the bottom electrodes of an OLED segment, even if they are located in the emission path. This situation is illustrated in Figure 5A, which is a top view of a split OLED device 500, which is a heterogeneous array of seven individual OLED segments.

[0070] Split OLED device 500 has two columns of three OLED segments each, one column 1'-3' (defined by corresponding bottom electrode segments 1-3) and one column 5'-7' (defined by corresponding bottom electrode segments 5-7). The two columns are separated by one larger segment 4' (defined by corresponding bottom electrode segment 4). Above transparent substrate 10 are power feeds (15, 25, 35, 45, 55, 65, 75) for each corresponding electrode segment (1-7), all located between the three sections (22, 24, 26) of the conductive layer. The power feeds are electrically insulated from each other and from the conductive layer sections 22, 24, 26 by insulating layer 31. Not shown in FIG. 5A (but visible in FIG. 5B) are insulating layer 30 over power feed / conductive layer sections 22, 24, 26 / insulating layer 31, followed by electrode segments 1-7 separated laterally by PDL 40, as well as light emitting organic layer 50, common top electrode 60, and encapsulant 70.

[0071] In split OLED device 500, there are different passive capacitor structures formed by the overlap of electrode segments 1 and 5 with conductive layer section 22, the overlap of electrode segments 2 and 6 with conductive layer section 24, and the overlap of electrode segments 3 and 7 with conductive layer section 26. These passive capacitor structures are connected in parallel between the bottom electrode segments and the conductive layer sections. These passive capacitor structures increase the total capacitance of OLED segments 1'-3' and 5'-7', and therefore provide ESD protection. However, OLED segment 4' has three different second capacitor structures where common electrode segment 4 overlaps with individual conductive layer sections 22, 24, and 26. In this case, the total capacitance of OLED segment 4' is the intrinsic capacitance of the OLED plus the sum of the three capacitances of the passive capacitor structures formed between 4 and 22, between 4 and 24, and between 4 and 26.

[0072] In split OLED device 500, the external contact pads for the power feeds are all located on the same side of the substrate. This arrangement is highly desirable for ease of device manufacture and installation. However, some of the power feeds must then be underneath bottom electrode segment 4 in order to contact bottom electrode segments 5-7 on the other side of the device. This can be seen in the cross section of split OLED device 500 taken along line Z-Z' shown in FIG. 5B. In this embodiment, power feeds 55, 65 and 75 are all underneath bottom electrode segment 4 and are electrically isolated from 4 by insulating layers 30 and 31. All of these power feeds are in the path of light emission from OLED segment 4' and may be visible in some circumstances.

[0073] In the OLED segment 4' of the split OLED device 500, there are additional passive capacitor structures formed between the power feeds 55, 65 and 75 (which are conductive) and the overlying electrode segment 4 when the device is not operating or when no power is applied to those particular power feeds. This is because there is no electrical connection between those power feeds (which feed the other electrode segments) and the overlying electrode segment 4, independent of the power feeds. During operation of the split OLED device, some of these power feeds may be powered, and therefore do not function as passive capacitor structures at that time. However, such an arrangement can still increase the total capacitance of the OLED segment, since ESD protection is required when the device is not operating.

[0074] In the illustrative example of split OLED device 500, there are only three power feeds (which are relatively thin in width because there is only an array of seven OLED segments, and therefore IR drop is not a concern) located below electrode segment 4, and therefore the additional passive capacitance provided by the capacitor structures formed between power feeds 55, 65, and 75 and bottom electrode segment 4 is small, since each of the corresponding passive capacitor structures is small. In this example, the overlap area of ​​power feeds 55, 65, 75 with electrode segment 4 is much less than 25% of the area of ​​the electrode segment. Therefore, the additional capacitance provided by these passive capacitor structures is negligibly small in this example.

[0075] However, a split OLED device may have many individual segments, e.g., 100-1000 segments. Since each segment has its own individual power feed, there may be many power feeds with external contact pads located along one side of the substrate. Furthermore, for such large device sizes, the power feeds may need to span long distances, so the width (and overall conductivity) of the power feeds may need to be large to prevent IR drop. In such cases, the OLED segments at or near the side of the array where the contact pads are located may have many power feeds for other segments located below the electrode segment. A total overlap area of ​​the electrode segment and all of the power feeds located below it of at least 30%, more preferably at least 50%, and most preferably at least 70% or more of the area of ​​the individual electrode segments may be sufficient to provide adequate ESD protection when the device is not in operation.

[0076] 6A is a top view of a substructure of a large split OLED device 600, with power feeds 601-615 all passing under a single free-standing electrode segment 1 without any electrical contact. This results in multiple overlap areas 90 between each of the power feeds 601-615 and the electrode segment 1 above all of these power feeds. Because the power feeds 601-615 are not electrically connected to the electrode segment 1, this creates multiple passive capacitor structures in the overlap areas 90. The power feeds 601-615 extend outside the encapsulant 70 to form external contact pads along the same edge of the device 600. The power feeds in this example do not all have the same width, with 601, 604, 607, 610, and 613 all being wider than the others. These wider power feeds are for connecting to electrode segments relatively far from the ends, and the wider widths help minimize IR drop.

[0077] In this case, when the device is not in operation, the overlap of each power feed (which acts as a bottom electrode of the passive capacitor structure) with the electrode segment above it (which acts as a common top electrode of the passive capacitor structure) forms multiple passive capacitor structures, with each power feed connected to a separate OLED segment. Because the OLED segments of the array are all connected in parallel, the passive capacitance to an OLED segment is the sum of the capacitance due to the total overlap of all the underlying power feeds with the overlying (common) electrode segment, plus the capacitance of the separate independent OLED segments, whose power feed(s) also form passive capacitor structures in a manner similar to that described for split OLED device 100.

[0078] In this example, the total area of ​​all passive capacitor structures formed by the overlapping areas of power feeds 601-615 and electrode segment 1 is greater than 50% of the area of ​​the electrode segment, so the total capacitance of this OLED segment (intrinsic OLED capacitance plus the sum of all passive capacitances due to the power feeds and electrode segments forming passive capacitor structures, plus the capacitance of other independent OLED segments that have the same power feed underneath them) provides enhanced protection from ESD damage whenever the device is not operating or when a particular power feed is not powered.

[0079] FIG. 6B shows a cross section of partial OLED device structure 600 along line Z-Z' in FIG. 6A. In this example, a separate conductive layer (i.e., 20 in the other figures) is not necessary because the sum of the capacitances formed by the power feeds and the multiple passive capacitor structures (indicated by arrows) formed by the independent electrode segments thereon, together with the OLED's intrinsic capacitance, is sufficient to provide ESD protection for this particular OLED segment. In effect, there is no need for a separate conductive layer section since there are enough power feeds to act together as bottom electrodes of passive capacitor structures sufficient to protect the independent OLED segments located above when the device is not in operation. Power feeds 601-615 may be disposed directly on transparent substrate 10. Insulating layer 30, which serves as a shared dielectric layer for the passive capacitor structures, is located between and above the power feeds, so that there is no electrical contact between the power feeds or between the power feeds and electrode segment 1. Organic layer 50, top electrode 60, and encapsulant 70 complete OLED segment 1' defined by electrode segment 1.

[0080] Because capacitance increases with the addition of parallel passive capacitor structures (in this embodiment formed between the power feed and the bottom electrode segments of the independent OLED segments) that share a common bottom electrode, the power feed, which functions as the bottom electrode of the passive capacitor structure, also preferably passes under the bottom electrodes of multiple independent OLED segments, more preferably under at least five independent segments, and most preferably under ten or more independent OLED segments. The use of a power feed as a passive capacitor structure for some OLED segments in an array can also be used in combination with the use of a common conductive layer for other OLED segments.

[0081] The transparent substrate 10 can be glass (including flexible glass) or a polymeric material. It is generally flat with a uniform thickness. The top surface of the substrate is the one that faces the OLED. The substrate will be part of the overall encapsulation of the OLED and therefore must be sufficiently impermeable to air and water for the OLED to have a desired lifetime. The substrate can be rigid or flexible. The substrate can have various types of undercoat layers (i.e., planarization layers, light management layers, etc.), which can be patterned or unpatterned, and can be located on either the top or bottom surface. Rigid or flexible glass is preferred.

[0082] The conductive layer 20 serves as the lower electrode of a passive capacitor structure separated by an insulating layer from the bottom electrode segment of the OLED segment (which serves as the upper passive capacitor electrode). There is no direct electrical contact between the upper and lower capacitor electrodes. The passive capacitor structure is not electrically connected to any part of the control circuitry of the particular OLED segment that would increase the overall capacitance. The mere presence of the passive capacitor structure may provide a sump or reservoir for holding the ESD voltage. In particular, the passive capacitor structure does not participate in any operation of the associated OLED segment, including functioning as a storage capacitor used to store power for the OLED segment to emit light. Desirably, the passive capacitor structure is electrically isolated (not directly electrically connected to any other circuitry) and serves merely to aid in the dissipation of the ESD charge through the participation of the capacitance of the entire array. In some cases, the conductive layer may be connected to ground to allow for faster dissipation, or may be isolated from the power supply of the OLED segment and connected to an independent voltage source, or even connected to the common top electrode of the OLED array.

[0083] The conductive layer 20 is preferably as transparent as possible since it is in the light emission path of the OLED segments. The conductive layer may be made of a thin metal layer such as silver or copper, a conductive metal oxide such as ITO, AZO, IZO, GZO, ZnO, TiN, SnO2, an organic material such as PEDOT:PSS, CNT (carbon nanotubes), graphene, or conductive particles such as silver, nickel, copper suspended in a polymeric binder (conductive ink), or any combination of these materials. The conductive layer may incorporate auxiliary structures such as metal grid lines to improve conductivity. The conductive layer may be composed of multiple layers. Desirably, the conductive layer is a conductive metal oxide, in particular ITO or AZO.

[0084] Ideally, the conductive layer has a thickness of 5 to 500 nm, preferably 10 to 250 nm, and most preferably 20 to 150 nm.

[0085] Conductive layer 20 may be unpatterned and deposited as a single continuous uniform layer across the surface of the substrate. However, in other embodiments, conductive layer 20 may be patterned. For example, conductive layer 20 may be patterned such that it is a continuous, uniform layer that only underlies the light emitting areas of the array. Alternatively, conductive layer 20 may be patterned such that it is not uniform but includes features such as slots, cutouts along edges, internal openings, etc., as a single continuous layer.

[0086] The conductive layer 20 may also be patterned in sections such that there is one section that is a continuous layer only under some of the electrode segments but not under all of the electrode segments. In such cases, the conductive layer is patterned into two or more sections that are electrically isolated from each other. For example, the conductive layer may be patterned such that individual sections are only located directly under each electrode segment. Alternatively, a single conductive layer section may be located under two or more electrode segments, or a single electrode segment may be located over two or more different conductive layer segments. The different sections of the conductive layer may be laterally separated by non-conductive or insulating materials. There may be OLED segments in the array that do not have a conductive layer under the bottom electrode segment on the OLED structure. In such instances, there is no overlap.

[0087] Since not all OLED segments may require additional ESD protection, it may be desirable for the conductive layer to overlap fewer than all OLED electrode segments. In particular, at least one OLED segment in the array may not have an associated passive capacitor structure. In an associated passive capacitor structure, the bottom electrode of the OLED structure also serves as the top electrode of a passive capacitor structure in the same OLED segment. Since the additional capacitance required for ESD protection of an individual OLED segment depends on having an additional parallel OLED segment with a passive conductive structure, it may be desirable for the conductive layer to overlap at least two OLED electrode segments. In particular, in some embodiments, it is desirable for the conductive layer to overlap the electrode segments of at least two OLED segments, but less than all OLED segments, such that at least one OLED segment does not have a passive capacitor structure. In some embodiments, it is desirable for at least 20%, more preferably at least 50%, of all OLED segments to have an associated passive capacitor structure.

[0088] Conductive layer 20 can be patterned using photolithographic techniques, deposited using a mask, or uniformly deposited and then the unwanted portions removed (ie, by laser ablation).

[0089] In embodiments where the power feeds for the individual OLED segments are located below the electrode segments to which they are not electrically connected (i.e., independent OLED segments), the power feeds can form a passive capacitor structure with the overlying unconnected (independent) electrode segments whenever the OLED device is not in operation (i.e., not connected to a power source) or whenever no current or voltage is applied through the power feeds (i.e., the OLED segments are in the "off" state). In this manner, the power feeds can serve the same purpose and function in the same manner as the conductive layer 20 with respect to ESD protection in these embodiments. However, it is necessary that the sum of the capacitances from the multiple passive capacitor structures formed between all the power feeds and the electrode segments provide sufficient passive capacitance such that when added to the inherent OLED capacitance, the total capacitance provides sufficient ESD protection. It should be noted that when the power feed is electrically connected to the split electrode above it, the resulting structure is not a capacitor.

[0090] There should be only one power feed per electrode segment, and each power feed is electrically isolated from the other power feeds and independent electrode segments by non-conductive or insulating materials. "Independent" means an electrode segment (or corresponding OLED segment) that is not connected to a particular power feed and is electrically isolated from that power feed. Thus, each OLED segment in the array has a single dedicated power feed to which it is electrically connected, and all other OLED segments are independent from that power feed. In some cases, a power feed may be split into two or more sub-power feeds, which are connected to the same electrode segment at different locations. In some cases, two or more separate but commonly operating power feeds (considered equivalent to a single power feed) may be connected to a single segment. For example, a driver with a maximum output of 10mA may be connected to a 20cm 2 to obtain the desired light output at the segment. 2 If 10cm is required, this segment requires two power feeds (one from each driver, or one from each of the two channels of a multi-channel driver). 2 A segment may be driven by a single driver, but the corresponding power feed may be split into two paths if necessary to accommodate other power feeds in the device. Such an arrangement may help to distribute power more evenly over the segments or reduce IR drop. In some cases, however, the same power feed may be used for more than one segment. Segments that share a common power feed cannot be activated individually, but are commonly illuminated and considered equivalent to a single segment.

[0091] On the outside of the encapsulant are external contact areas (also called contact pads) that are electrically connected to each of the power feeds inside the encapsulant. The figures show the extensions of the power feeds outside the encapsulant forming the contact areas, but it is possible to selectively remove the encapsulant over the power feeds to make electrical contact through the encapsulant. A controlled power source is then electrically connected (i.e., by soldering or ACF) to these contact areas to provide power as required to the power feeds and split electrodes within the encapsulant. By providing the appropriate amount of power to the contact areas for the appropriate period of time, the OLED segments will emit light at the desired brightness for that period of time. The power provided to the external contact pads is determined by a controller or driver. It is highly preferred that the contact pads for each power feed are all located along one side or edge of the substrate.

[0092] The location and distribution of the individual power feeds across the surface of the substrate depends on the design of the OLED segment array. Some power feeds may be located along the non-emitting areas (i.e., in the gaps between segments and / or along the outer edges of the device), while other power feeds are located under the electrode segments and in the optical path. Depending on the design, some segments may not have a power feed located between or under the segments, while other segments may have multiple power feeds between or under the segments.

[0093] It is important that the IR drop along the power feed is equivalent for all OLED segments, regardless of their distance from the external power source or the size of the OLED segment (larger segments require more power to operate than smaller segments). However, the IR drop can be minimized by adjusting the width (parallel to the substrate) or height (above the substrate) of the power feed. Thus, in such cases, not all power feeds have the same width and height dimensions, which may vary according to their length as well. Furthermore, not all of the power feeds have the same structure. For example, shorter power feeds may be made of a conductive metal oxide, while longer power feeds may have an auxiliary electrode or be metallic, such as a thin layer of Ag.

[0094] If the power feed is not located in the light emission path, the power feed may be opaque or transparent as desired. If the power feed is located in the light emission path, the power feed should be as transparent as possible. The power feed may be constructed of any conductive material that can be patterned. For example, the power feed may be made from metals such as silver or copper, conductive metal oxides such as ITO, AZO, IZO, GZO, ZnO, TiN, SnO2, organic materials such as PEDOT:PSS, CNT (carbon nanotubes), graphene, or conductive particles such as silver, nickel, copper suspended in a polymeric binder (conductive ink), or any combination of these materials. Inherently opaque conductive materials (i.e., silver) may be in the form of nanowires or meshes, so that there may be openings in the structure of the power feed that allow some light through, or may be thin enough so that it is not opaque. Ideally, the power feed should have a resistivity of less than 25 ohms / square, and preferably less than 15 ohms / square.

[0095] The power feed is preferably constructed from a conductive metal oxide, with ITO being particularly preferred. However, ITO is known to have a limited degree of lateral electrical conduction. If desired, a power feed formed from a conductive metal oxide may have an auxiliary electrode (e.g., an overcoat or sublayer of a conductive metal such as metallic silver or aluminum, or a conductive metal mesh) that helps minimize IR drop along some or all of its length.

[0096] In general, the conductive material of which the conductive layer or power feed is constructed may have a relatively high refractive index, while the surrounding material may have a different, often substantially lower, refractive index. This refractive index difference at the interface between the conductive material and an adjacent material may lead to a visible difference in light emission or reduced light emission due to internal light refraction. By matching the refractive index between the conductive layer or power feed and other materials in direct contact (or, at least, minimizing the mismatch), or by incorporating an index-reducing material into the split OLED device, where the refractive index of the index-reducing material is of a more similar magnitude to the refractive index of the conductive layer or power feed, the visible difference in light emission due to the presence of a mismatched material in the light path can be eliminated or at least reduced. Ideally, the reflectance difference (D) between the area of ​​the transparent substrate where the conductive layer or power feed is located and the area of ​​the transparent substrate where the gap between the power feeds is located is 0.01 μm. R ) is less than 5%. To achieve this, the refractive index R I and the refractive index R of any material in direct contact with the conductive material. I Ratio to (High R I / low R I It is preferred that R ) is in the range of 1.00 to 1.06. The inclusion of the index-reducing material makes the light emission from each segment of the device appear more uniform. It is important that the index-reducing material and layers are electrically non-conductive. I Note that it does not matter which material is high and which is low, only the difference in is important.

[0097] To form passive capacitor structures having either the conductive layer 20 or the power feed as the bottom electrode and to prevent shorting with the electrode segments above it, the top surfaces of these conductive structures are covered with a non-conductive dielectric material that separates them from the electrode segments. The dielectric material of the passive capacitor structures can be an insulating layer 30, which can be patterned or unpatterned as required. The insulating layer 30 can also be present outside of the overlap area between the conductive structure that serves as the bottom passive capacitor structure electrode and the electrode segment that serves as the top electrode of the passive capacitor structure. In some embodiments, a section of an auxiliary insulating layer 31 may be present. For example, the insulating layer 31 may be used to fill and electrically isolate the spaces between the conductive layer 20, the power feed and the conductive layer, different sections of the power feed, or for planarization. The insulating layer 31 may or may not be composed of the same material(s) as the insulating layer 30.

[0098] The capacitance of the passive capacitor structure formed by the conductive layer 20 or power feed, insulating layer 30 (and 31, if present), and electrode segments depends on the composition and thickness of the dielectric insulating layer 30 (and 31, if present), and the amount of overlap between the capacitor electrodes. Thus, the thickness and composition of the insulating layer 30 (and 31, if present) must be selected depending on the overlap so that the passive capacitance, when added to the intrinsic capacitance of that particular OLED segment, is sufficient to provide ESD protection.

[0099] Preferably, the insulating layer 30 or 31 is transparent and non-light scattering. The insulating material desirably has an electrical resistance of 1 megohm (MΩ) or more, more preferably 2 megohm or more. Since the insulating layer is in the light emission path, the insulating material desirably has a refractive index ratio with the conductive material of the passive capacitor structure electrodes in the range of 1.00 to 1.06. The insulating layer may be polymeric, but is preferably inorganic. Suitable inorganic insulating layers or materials include SiO2, SiN, SiON, Al2O3, TiO2, etc., and mixtures thereof. The vertical distance should be greater than 0.05 microns to prevent short circuits and less than 10 microns to maintain a thin device, ideally in the range of 0.1 to 1.0 microns.

[0100] When the power feed is located in a lateral space between the electrode segments, electrical contact between the power feed and the electrode segment is typically made to the side of the electrode segment. When the power feed is located below the electrode segment, electrical connection between the power feed and the overlying split electrode is made through a via, which is a hole or passage in the insulating material (i.e., insulating layer 30 or 31) separating them. The via passes from the top of the power feed to the bottom or side of the split electrode. Ideally, the via connects to the split electrode at a location that corresponds to the non-emitting area of ​​the split OLED. The via may be formed by patterning the overlying insulating material to leave at least a portion of the top surface of the power feed exposed or uncovered. Alternatively, the via may be formed by uniformly depositing the overlying insulating material on the power feed and removing material over the desired portion of the power feed to expose the top surface.

[0101] The vias are filled with a conductive material. When a split electrode is deposited on top of the material, some of the material of the split electrode can fill the via and make the connection. Alternatively, the vias may be filled with a conductive material first, and then the split electrode is deposited on top of the filled via / insulating material. In some cases, it may be necessary to treat the power feed before depositing the insulating layer, or the filled via before depositing the split electrode, with a material that promotes electrical conductivity through the connection.

[0102] The length and area of ​​the via is not critical, but should be sufficient to supply the necessary power to the split electrodes. The via may be of any shape along the top surface of the power feed. In particular, the via may extend along the length of the power feed. There may be multiple vias between the power feed and the electrode segments.

[0103] There is an array of individual electrode segments that sit on a common substrate with other intervening layers. "Common" means that all of the OLED segments in the array share the same substrate and are fabricated together on that substrate as an array. On all sides (except those along the outer edges of the device or at the corners), there are non-emissive lateral gaps between the individual segments that separate them.

[0104] In split OLED devices, the bottom electrode segment is transparent. The transparent electrode segment should transmit as much light as possible, preferably with at least 70% or, more preferably, at least 80% transmittance. However, in some applications (i.e., microcavity devices), the transparent bottom electrode may only need to be semi-transparent and partially reflective. The bottom transparent electrode may be made of any conductive material, but is preferably a thin layer of a metal oxide such as ITO or AZO, or a metal such as Ag. In some cases, there may be an auxiliary electrode that helps distribute the charge more evenly across the area of ​​the transparent electrode. Ideally, the electrode segment should have a resistivity of less than 25 ohms / square, preferably in the range of 10-23 ohms / square.

[0105] In some embodiments, a pixel definition layer (PDL) is present to separate a portion of one OLED segment from another OLED segment or along the perimeter of the array. The PDL can be used to separate the electrode segments from electrical contact, define the outer edge of the array, and confine the organic layer to a single OLED segment. In some cases, the PDL can be used to partially cover the electrode segments to prevent light emission in the PDL area (e.g., in areas where vias are located along the edges of the electrode segments). In other cases where there is no PDL layer in the gap between the electrode segments, there may still be a PDL located along the perimeter of the array. The PDL is preferably insulating (non-conductive).

[0106] In some embodiments, the PDL in the gap between the bottom electrode segments has approximately the same thickness as the electrode segments. This creates a relatively flat surface for depositing the top layer. In other embodiments, the PDL is thicker than the electrode segments, so that a portion of the PDL extends beyond the top surface of the electrode segments, either into the gap or along the outer edge of the array. In some cases, the extended portion of the PDL will also cover a portion of the top surface of the electrode surface. In such cases, the PDL may cause undesirable light piping or light guiding. To reduce light piping, an absorbing dye may be added to the PDL. Alternatively, the PDL layer material may be opaque or black.

[0107] Suitable PDL materials may be polymeric or inorganic. Examples of suitable polymeric PDLs include acrylic polymers and polyimide polymers. Some examples of suitable inorganic PDLs include SiO2, SiN, and SiON. Ideally, the thickness of the PDL layer should be 5 microns or less, and preferably in the range of 0.2 to 3.0 microns.

[0108] Figure 7 shows a typical configuration of the OLED layer types for light emission in an example OLED 1000. There will be one or more light-emitting layers with multiple auxiliary layers that help facilitate and control the transfer of charge between the electrodes when light is emitted. In this particular example, the bottom electrode segment is the anode and the top electrode is the cathode.

[0109] Above the transparent electrode segments 514, there may be an optional hole injection layer (HIL, layer 501). The purpose of the HIL is to manage the transport of holes from the anode to the organic layers. Suitable hole injection materials are well known and commonly used. These layers may be mixtures of such materials and may include dopants to modify their properties. They are non-emissive and therefore do not include emissive materials. Generally there is only one HIL. The selection of the appropriate material is not critical and any may be selected based on its performance. One example of a suitable HIL material is HAT-CN.

[0110] On top of the HIL (layer 501) is disposed a hole transport layer (HTL, layer 502). The purpose of the HTL is to manage the transport of holes from the HIL to the emissive layer above. Suitable hole transport materials are well known and commonly used. These layers may be mixtures of such materials and may contain dopants to modify their properties. They are non-emissive and therefore do not contain emissive materials. There may be multiple HTLs. The selection of the appropriate material is not critical and any may be selected based on its performance. One example of a suitable HTL is NPB.

[0111] Above the HTL (layer 502) is an optional exciton blocking layer (EBL, layer 503). The emissive layer optionally emits light via the formation of excitons that have a lifetime sufficient to diffuse away from their formation site. The purpose of the EBL is to confine the excitons to the LEL to maximize light emission. Suitable exciton blocking materials are well known and commonly used. These layers may be mixtures of such materials and may include dopants to modify their properties. No emissive materials are included, as they are non-emissive. There may be multiple EBLs. The selection of the appropriate material is not critical and any may be selected based on its performance. One example of a suitable EBL is mCP.

[0112] A first light-emitting layer or unit (LEL1, layer 504) is disposed on top of the EBL (layer 503). The light-emitting layer (LEL), which is a single layer, generally comprises one or more non-emissive host compounds and one or more light-emitting dopants. Suitable host materials and fluorescent, phosphorescent and TADF light-emitting dopants for use in the light-emitting layer or unit are well known and commonly used. Light-emitting units as defined above may also be used for emission. The selection of suitable materials is not critical and any may be selected based on its performance and emission properties.

[0113] Above LEL1 (layer 504) is an optional hole blocking layer (HBL, layer 505). Emitting layers emit light by the formation of excitons, which in some cases may not form fast enough before holes migrate towards the cathode. The purpose of the HBL is to confine holes to the LEL to maximize light emission. Suitable hole blocking materials are well known and commonly used. These layers may be mixtures of such materials and may include dopants to modify their properties. They are non-emissive and therefore do not include emissive materials. There may be multiple HBLs. The selection of the appropriate material is not critical and any may be selected based on its performance. One example of a suitable HBL is SF3-TRZ.

[0114] A charge generation layer (CGL, layer 506) is disposed on top of the HBL (layer 505). The CGL (sometimes called a connector layer or intermediate layer) is located between the individual OLED light-emitting units and typically consists of multiple layers. This is because the CGL is structured so that when a voltage is applied, electrons and holes are generated and injected into the adjacent organic light-emitting layer. Thus, the use of a CGL may potentially convert one injected electron into multiple photons, resulting in higher brightness. In particular, a CGL is preferably disposed between each light-emitting unit in the stack. However, there is no need for adjacent CGLs on both sides of a light-generating unit. The top and bottom OLED light-generating units in the stack will generally only have one adjacent CGL. It is not usually necessary to use a CGL between the light-emitting unit and either the top or bottom electrode, but a CGL can be used if desired.

[0115] Many different types of CGLs have been proposed and may be used in an OLED stack. See, for example, US Pat. No. 7,728,517 and US Patent Application Publication No. 2007 / 0046189. To form a CGL, an np semiconductor heterojunction located at the interface of the n-type and p-type layers is typically required for charge generation. Thus, the CGL will have two or more layers. For example, n-doped organic layer / transparent conductive layer, n-doped organic layer / insulating material, n-doped organic material layer / metal oxide layer, and n-doped organic material layer / p-doped organic material layer have all been reported. A preferred metal oxide for the CGL is MoO3. In some instances, the n- and p-layers may be separated by a thin intermediate layer. Often, the CGL is arranged with the n-layer close to the anode and the p-layer close to the cathode.

[0116] One desirable formulation of a CGL has three layers: an electron-transporting material doped with an n-dopant (e.g., Li), a thin intermediate layer of the same (but undoped) electron-transporting material, and a hole-transporting material doped with a p-dopant. Another desirable formulation of a CGL has the same type of doped ETL with an intermediate layer of a different electron-transporting material and an electron-deficient hole-injecting material such as HAT-CN. Another desirable formulation of a CGL has an undoped ETL layer, a layer of Li or Ca, an intermediate layer of the same or different electron-transporting material and an electron-deficient hole-injecting material, or a hole-transporting material doped with a p-dopant.

[0117] Suitable electron transport materials, hole injection or transport materials, and n-dopants and p-dopants suitable for use in CGLs are well known and commonly used. The materials may be organic or inorganic. The selection of the appropriate material is not critical and any may be selected based on its performance. The thickness of the CGL should desirably be in the range of 200-450 Å, although in some instances, with thinner CGLs, it may be in the range of 100-200 Å. Often, the CGL will have an ETL or HBL on the anode side and an HTL or EBL on the cathode side to improve charge transport and to help separate the charge generating dopant (if present) from the LEL in the light emitting unit. There may be multiple such layers and they may be doped or undoped as desired.

[0118] Disposed on top of the CGL (layer 506) is a second light-emitting layer or unit (LEL2, layer 507), which represents the second stack of the OLED device. In FIG. 7, the two LELs (layers 504 and 507) are separated by the CGL (layer 506), and thus the OLED stack of FIG. 7 is a "two-stack" (or double-stack) OLED. One or more HTLs (doped or undoped) may be present between the CGL (layer 506) and LEL2 (layer 507). LEL2 may emit the same color as LEL1 or a different color.

[0119] At least one HBL (layer 508), similar to that described as layer 505, is disposed above LEL2 (layer 507).

[0120] Above the HBL (layer 508) is disposed an electron transport layer (ETL, layer 509). The purpose of the ETL is to manage the transport of electrons from the EIL to the emissive layer below. Suitable electron transport materials are well known and commonly used. These layers may be mixtures of such materials and may include dopants to modify their properties. They are non-emissive and therefore do not include emissive materials. There may be multiple ETLs. The selection of the appropriate material is not critical and any may be selected based on its performance. One example of a suitable ETL is TPBI.

[0121] Above the ETL (layer 509) is an optional electron injection layer (EIL, layer 510). The purpose of the EIL is to manage the transport of electrons from the cathode to the organic layers. Suitable electron injection materials are well known and commonly used. These layers may be mixtures of such materials and may contain dopants to modify their properties. They are non-emissive and therefore do not contain any emissive material. Generally there is only one EIL. The selection of the appropriate material is not critical and any may be selected based on its performance. One example of a suitable EIL material is LiF.

[0122] Above the light emitting organic layers (50, layers 501-510 in FIG. 7) is a top electrode 60, which in FIG. 7 is the cathode. The top electrode 60 is preferably composed of a thick layer of a metal or metal alloy, such as Al, Ag, Mg / Al, Mg / Ag, etc. The top electrode can be deposited by any known technique. The top electrode may be patterned in the non-emitting areas, but is typically deposited uniformly over the emitting areas. A contact area (contact pad) is needed outside the encapsulant for an external power source, which is electrically connected to the top electrode inside the encapsulant. Some examples of suitable materials for the top electrode are Al, Al / Mg, Ag / Mg, Ag.

[0123] There may be an optional protective or spacing layer (layer 511 in Figure 7) over the top electrode to prevent damage during encapsulation. These may be small molecule organic, polymeric, or inorganic materials. Organic materials are preferred.

[0124] An encapsulant 70 is deposited or placed over the reflective cathode and optional protective layer (if present). At a minimum, the encapsulant should completely cover the light emitting area on the top and sides and is in direct contact with the substrate. The encapsulant should be impermeable to air and water. The encapsulant may be transparent or opaque. The encapsulant must not be electrically conductive. The encapsulant may be formed in situ or added as a separate preformed sheet with provisions for sealing the side edges.

[0125] One example of in situ formation is thin film encapsulation. Thin film encapsulation involves depositing multiple layers of alternating inorganic materials and polymer layers until the desired degree of protection is achieved. Formulations and methods for forming thin film encapsulation are well known and any may be used as desired.

[0126] Alternatively, sealing may be provided using a preformed sheet or cover slip that is applied over at least the sealing area and the encapsulation area. The preformed sheet may be rigid or flexible. The preformed sheet may be made of glass (including flexible glass), metal, or an organic / inorganic barrier layer. It is desirable for the preformed sheet to have a thermal expansion coefficient close to that of the substrate to achieve a stronger connection. The preformed encapsulation sheet may need to be applied over the sealing area using an air- or water-resistant adhesive, such as silicone or epoxy adhesive, or by thermal means, such as ultrasonic welding or glass frit welding, in which case an additional sealant, such as solder or glass frit, may be required. The side and bottom edges of the cover slip may be specially designed to better fit into the sealing area or promote a better seal. The cover slip and sealing area may be designed together to be partially fitted or locked into place before the seal is formed. Additionally, the cover slip may be pretreated to promote better adhesion to the sealing area.

[0127] In some applications, an increased degree of encapsulation is required. This can be achieved by providing an additional metal foil encapsulant (layer 513) that is attached over encapsulant 70 by a pressure sensitive adhesive (layer 512). The use of metal foil not only provides a robust encapsulation, but also acts as a heat sink to prevent excessive heating that would be detrimental to the OLED device.

[0128] In many applications, a single stack OLED device can provide sufficient light emission for the intended purpose. Some applications require more brightness than a single OLED stack can provide. In such cases, two or more stacks (as shown in FIG. 7) are required. Generally, adding another OLED stack (i.e., two units instead of one) doubles the brightness but also requires twice the power. A three-stack OLED provides three times the brightness but requires three times the power, and so on. In the split OLED device of the present invention, as many stacks as necessary can be added to obtain the desired brightness, the only limitation being the increase in voltage required to drive the device. Desirably, there are at least two stacks in the split OLED device, and there are as many as six stacks.

[0129] Another way to increase the brightness of OLEDs, especially if monochromatic emission is desired, is to incorporate the microcavity effect. To create a microcavity, one electrode is made reflective and the other semi-transmissive, causing the light to reflect internally. The distance between the two electrodes causes interference, eliminating or reducing some wavelengths of light and enhancing others. The microcavity effect can be used in the OLED segment of the device.

[0130] All OLED segments are capable of white or multimodal emission, and color filters can be used to produce the emission color desired by each particular segment. The various individual LELs or units within a split OLED device are not limited to providing the same color, although some applications require monochromatic emission. For example, many automotive taillight applications require all LELs or units to produce red light. Note that while the different LELs or units may all emit the same color light, they do not all need to have identical emission spectra, and some may have a different percentage of certain wavelengths than others (i.e., one unit produces a spectrum rich in short red wavelengths, while another unit produces more of the longer red wavelengths).

[0131] One method for fabricating a bottom-emitting split OLED device having an array of OLED segments, where at least one OLED segment constitutes a passive capacitor structure to increase the total capacitance, comprises, in order, the steps of: 1) depositing a layer of transparent conductive material on a transparent substrate, the conductive material forming a bottom electrode of a passive capacitor structure; 2) depositing a transparent, electrically insulating material over the conductive layer, the insulating material forming the dielectric of the passive capacitor structure; 3) patterning the transparent electrode segments and conductive power feeds on the insulating material such that each electrode segment has one power feed and such that at least one overlying electrode segment overlaps at least a portion of the underlying conductive layer, the overlap of the conductive layer and electrode segments separated by the insulating material of step 2 forming a passive capacitor structure; 4) depositing pixel defining material in the lateral spaces between the electrode segments, between the power feeds, and between the electrode segments and the power feeds of other electrode segments; 5) depositing a light emitting organic layer on top of the electrode segments; 6) depositing a common top electrode on the organic layer to complete an OLED segment including a bottom electrode segment, an organic layer and a top electrode; 7) Forming an encapsulant over the array of OLED segments.

[0132] Another method for fabricating a bottom-emitting split OLED device having an array of OLED segments, where at least one OLED segment constitutes a passive capacitor structure for increasing the total capacitance, comprises, in order, the steps of: 1) patterning a conductive transparent material and a conductive power feed on a transparent substrate, such that the power feed is not in contact with the conductive material, and filling a lateral space between the conductive material and the power feed with an electrically insulating material, at least a portion of the conductive material forming a bottom electrode of a passive capacitor structure; 2) depositing a transparent, electrically insulating material over the conductive layer and the power feed, the insulating material forming a dielectric of a passive capacitor structure; 3) forming vias in the insulating layer above the power feed; 4) patterning transparent electrode segments on the insulating material such that per OLED segment there is one electrode segment connected to one power feed through a via, at least one overlying electrode segment overlapping at least a portion of the underlying conductive layer, such that the overlap of the conductive layer and the electrode segment forms a passive capacitor structure with the insulating material of step 2; 5) depositing a pixel defining layer in the lateral spaces between the electrode segments; 6) depositing a light emitting organic layer on at least the top surface of the electrode segments; 7) depositing a common top electrode on the organic layer to complete an OLED segment including a bottom electrode segment, an organic layer, and a top electrode; 8) Forming an encapsulant over the array of OLED segments. Some useful variations of the above method include the following. - patterning the conductive layer so that it is common to all electrode segments; - patterning a conductive layer to overlap at least two electrode segments; -Patterning the conductive layer to overlap fewer than all of the electrode segments, such that some OLED segments do not have a passive capacitor structure.

[0133] Another method for fabricating a bottom-emitting split OLED device having an array of OLED segments, where at least one OLED segment constitutes a passive capacitor structure for increasing the total capacitance, comprises, in order, the steps of: 1) patterning conductive power feeds on a transparent substrate and filling the lateral spaces between the power feeds with an electrically insulating material, at least a portion of the power feeds serving as a conductive layer forming a bottom electrode of a passive capacitor structure; 2) depositing a transparent, electrically insulating material over the power feed, the insulating material forming the dielectric of a passive capacitor structure; 3) forming vias in the insulating layer above the power feed; 4) patterning transparent electrode segments on the insulating material such that there is one electrode segment connected to one power feed through a via for each OLED segment, such that a bottom electrode segment of one OLED segment overlaps at least a portion of a section of an underlying conductive layer connected to another OLED segment, the overlap of the conductive layer connected to another OLED segment and the bottom electrode segment of one OLED segment together with the insulating material of step 2 forming a passive capacitor structure; 5) depositing a pixel defining layer in the lateral spaces between the electrode segments; 6) depositing a light emitting organic layer on at least the top surface of the electrode segments; 7) depositing a common top electrode on the organic layer to complete an OLED segment including a bottom electrode segment, an organic layer and a top electrode; 8) Forming an encapsulant over the array of OLED segments. Some useful variations of the above method include the following. - Patterning the conductive layer to overlap fewer than all of the electrode segments, such that some OLED segments do not have a passive capacitor structure. - The area of ​​the OLED segment with the passive capacitor is 1 cm 2 is less than. - The area of ​​the OLED segment with the passive capacitor is at least 0.05 cm 2 It is. The overlap area between the conductive layer section(s) and the bottom electrode segment increases the total capacitance of the OLED segment by at least 0.2 nF. The overlapping area between the electrode segment and the conductive layer is at least 30% of the electrode segment.

[0134] Some desirable physical and performance characteristics of a bottom-emitting split OLED device include the following: Brightness: 2,000~20,000cd / m 2 , Number of OLED segments: >200 (can be of mixed sizes and shapes), Active area: 25cm 2 That's all, Segment size: <1cm 2 , most preferably <0.5 cm 2 , 2000cd / m 2 Current density: 13mA / cm 2 (2 stacks), 4.3mA / cm 2 (6 stacks), 5000cd / m 2 Current density: 32mA / cm 2 (2 stacks), 9mA / cm 2 (6 stacks), 10000cd / m 2 Current density: 25mA / cm 2 (6 stacks), 20000cd / m 2 Current density: 50mA / cm 2 (6 stacks), Non-emitting gap: <1mm, preferably <700μm, most preferably <200μm; All electrical contact areas (bottom and top electrodes) outside the encapsulant are located along only one edge of the device.

[0135] The above description describes several different embodiments. Individual features from any of the embodiments can be combined without restriction, except where mutually exclusive.

[0136] In the above description, reference is made to the accompanying drawings, which form a part hereof, and in which are shown by way of illustration specific embodiments that may be practiced. These embodiments have been described in detail to enable one skilled in the art to practice the invention, and it should be understood that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the scope of the invention. Thus, the description of any exemplary embodiment should not be construed in a limiting sense. While the invention has been described for purposes of illustration, it should be understood that such details are for that purpose only and that modifications may be made by those skilled in the art without departing from the spirit and scope of the invention.

[0137] Modeling and Experimental Results ESD reliability testing for split OLED devices used in automotive applications is divided into various categories or models that correspond to scenarios to which the device may be exposed. A more challenging scenario for OLED devices is the ESD Human Body Model (HBM), which represents when charge from an operator is transferred to the device, usually through the fingers. HBM ESD reliability testing is specified by the JEDEC-JS-001-2017 test standard.

[0138] In Figure 8, a 0.1 nF capacitor (C HBM ) is a test circuit that is powered by a dual polarity high voltage power supply to a standard voltage level (V HBM ), and when switch S2 is closed, the 1.5 kΩ resistor (R HBM ) into the test OLED device. HBM The standard's classification levels are shown in Table 1, and the level selected determines the amount of charge the device is exposed to during testing. [Table 1]

[0139] When a charge is transferred to the OLED, a voltage (V OLED ) is formed, and the more charge transferred, the higher the voltage. VOLED The HBM test parameters and OLED capacitance (C OLED ) and performing a simple charge balance as follows, where Q is the charge in coulombs: Q final =Q initial (1a) V OLED ×(C OLED +C HBM )=C HBM ×V HBM (1b) V OLED =(C HBM ×V HBM ) / (C OLED +C HBM )(1c) V OLED is a characteristic of the organic stack and is typically determined experimentally at a certain voltage limit (V LIM ) under the test conditions, no degradation or damage occurs to the OLED. LIM If the voltage is expected to reach 10 V, additional elements such as passive capacitor structures can be incorporated into the design to mitigate the voltage to which the OLED is exposed.

[0140] As shown in Tables 2a and 2b, V HBM Under test conditions of 2 kV and 8 kV, the OLED segment area and the number of automotive red organic stacks were changed to obtain V from Equation 1. OLED In this experiment, the capacitance per unit area of ​​the two-stack red OLED device for automotive use was calculated to be 21.7 nF / cm 2 and a similar six-stack device has a capacitance of 6.8nF / cm 2 All the examples were simple bottom-emitting OLEDs, and none included passive capacitor structures. [Table 2]

[0141] Calculated V OLED V of the organic stack LIMAbove 0.38 cm, ESD damage to the device is likely and additional protection is required. 2 All two-stack automotive red OLED segments are rated at 2kV V HBM Passed ESD test, but 0.17cm 2 It was experimentally determined that many of the segments in LIM The data suggests that V LIM suggests around 40V and conservatively 120V for 2-stack and 6-stack OLEDs, respectively.

[0142] If you add capacitance protection, the required C PASSIVE can be calculated as follows: Q final =Q initial (2a) V LIM ×(C OLED +C PASSIVE +C HBM )=C HBM ×V HBM (2b) C PASSIVE =(C HBM ×V HBM ) / V LIM -C OLED -C HBM (2c)

[0143] V of each OLED segment LIM depends on the OLED formation, so V LIM Assuming the range of C from Eq. 2c, PASSIVE It is useful to calculate the V (if present) for 2kV and 8kV HBM For different segment areas of 2 stacks and 6 stacks in V LIM C required over the range PASSIVE are shown in Tables 3a to 3b and Tables 4a to 4b, respectively. PASSIVEThe negative values ​​of suggest that no ESD protection is necessary for these particular OLED segments and are included here only to illustrate how close certain scenarios are to damaging the device. [Table 3]

[0144] For the two-stack OLED device above, V HBM is 2kV (V LIM If the voltage is 40V, it is 0.38cm. 2 and 0.25 cm 2 It is estimated that no additional capacitance is needed for a segment size of 0.17 cm, but the latter of the two areas is close to the limit. 2 , 0.10cm 2 , 0.05cm 2 The segments have C of 1.21 nF, 2.73 nF, and 3.82 nF per segment, respectively. PASSIVE is required. V LIM The higher the value, the less C required. PASSIVE Of course, V of 8kV will decrease. HBM For two-stack OLEDs, ESD protection is required for most of the conditions considered (Table 3b). [Table 4]

[0145] 6-stack OLED V HBM When is 2 kV (Table 4a), V LIM 0.38cm for 120V or more 2 and 0.25 cm 2 The OLED segment of PASSIVE is not necessary, but the latter is close to the limit. Under these conditions, 0.17 cm for 6 stacks is 2 , 0.10cm 2 , 0.05cm 2 The OLED segments have C of 0.41 nF, 0.89 nF, and 1.23 nF per segment, respectively. PASSIVE is calculated to be 0.25cm. 2In the segment, V LIM For a 80V, C of 0.71nF per segment PASSIVE is required. V LIM The higher the value, the higher the C required for the OLED segment. PASSIVE Of course, V of 8kV will decrease. HBM For the 6-stack OLED segments, all the segment sizes and V LIM Conditions under which ESD protection is required (Table 4b).

[0146] In this experiment, the 6-stack OLED formulation exhibited a relatively low specific capacitance (C OLED =6.8nF / cm 2 This OLED represents a practical OLED formulation with an estimated V LIM It is clear that smaller OLED segments with lower specific capacitance will experience higher voltages due to ESD exposure. For example, a 0.05 cm OLED segment with a 6-stack 2 The segment is V HBM = 456V at 2kV, and V HBM = 8 kV (see Table 2b). This is the V LIM ESD damage, 0.05 cm for 6 stack segments 2 To avoid the voltage that the segments experience, V LIM Assuming that V is 120V, HBM = 2kV, the minimum amount of capacitance that needs to be provided from the passive capacitor structure is approximately 1.23nF (see Table 4a). Similarly, 2 has an intrinsic capacitance of V LIM For two-stack formulations with V less than 60V, HBM = 2kV, the minimum amount of capacitance that needs to be provided by the passive capacitor structure is 1.32nF (see Table 3a).

[0147] Based on the above, adding the passive capacitor structure(s) of the OLED segment, V LIMTo keep I below a threshold, it is desirable to increase the total capacitance compared to the OLED segment without the passive capacitor structure. Since the capacitance of the passive capacitor structure(s) is directly dependent on the overlap between the common conductive layer and the bottom electrode of the OLED segment, it is desirable for the overlap to increase the total capacitance of the OLED segment by at least 0.2 nF, more desirably by at least 0.4 nF, or most desirably by at least 1.0 nF. [Explanation of symbols]

[0148] Z-Z' cross section / orientation line, 1'-7' OLED segments, 1-7 bottom split electrodes of corresponding OLED segments, 15 power feed for split electrode 1, 25 power feed for split electrode 2, 35 power feed for split electrode 3, 45 power feed for split electrode 4, 55 power feed for split electrode 5, 65 power feed for split electrode 6, 75 power feed for split electrode 7, 10 common transparent substrate, 20 conductive layer, 22, 24, 26 conductive layer section, 30, 31 insulating layer, 32 via, 40 pixel defining layer between split electrodes, 50 light emitting organic layer, 60 top electrode, 70 encapsulant, 80 non-emitting gap between OLED segments, 90 overlap between conductive layer and bottom electrode segment, 95 control circuitry, 100-400 split OLED device having 5 OLED segments, 500 split OLED device having 7 OLED segments, 600 Segmented OLED device having multiple conductive layer sections, 601-615 conductive layer sections, 1000 OLED device, 501 HIL, 502 HTL, 503 EBL, 504 LEL1, 505 HBL, 506 CGL, 507 LEL2, 508 HBL, 509 ETL, 510 EIL, 511 optional protective layer, 512 pressure sensitive adhesive, 513 metal foil encapsulant / heat sink, 514 bottom electrode segment, C HBM Test circuit capacitor, C OLED The capacitance of the associated OLED structure in the OLED segment, C O1 '~C O5' Capacitance of the OLED structure in OLED segments 1' to 5', C PASSIVE The capacitance of the associated passive capacitor structure in one OLED segment, C P1 '~C P5 ' Capacitance of the passive capacitance structure, R HBM Test circuit resistor, S1 first switch, S2 second switch, V HBM Standard voltage level, V OLED OLED voltage.

Claims

1. A split bottom-emitting OLED device comprising an array of OLED segments disposed on a common transparent substrate, the array forming emissive areas with each OLED segment separated by a non-emissive gap, each OLED segment being defined by a transparent bottom electrode segment, a light-emitting organic layer, and a top electrode; 1. An OLED device comprising: in at least one OLED segment, between the bottom electrode segment and the substrate, a transparent insulating layer proximate the bottom electrode segment and a transparent conductive layer proximate the substrate, an overlapping area of ​​the bottom electrode and the conductive layer forming an associated passive capacitor structure, the bottom electrode of the OLED segment being the top electrode of the passive capacitor structure, the insulating layer being the dielectric of the passive capacitor structure, and the conductive layer being the bottom electrode of the passive capacitor structure.

2. 10. The OLED device of claim 1 wherein the conductive layer is patterned.

3. 3. The OLED device of claim 2 wherein the conductive layer is patterned into two or more sections that are electrically isolated from one another.

4. 4. The OLED device of claim 2 or 3, wherein in at least one OLED segment, an overlap area between the section(s) of the conductive layer and the bottom electrode segment increases a total capacitance of the OLED segment by at least 0.2 nF.

5. 4. The OLED device of claim 2 or 3, wherein in at least one OLED segment, an overlap area between the conductive layer section(s) and the bottom electrode segment is equal to or greater than 30% of an area of ​​the bottom electrode segment.

6. 4. The OLED device of claim 3 , wherein in addition to those OLED segments having associated passive capacitor structures, a bottom electrode segment of at least one different OLED segment in the array has no overlap with a conductive layer section, such that the at least one different OLED segment does not have an associated passive capacitor structure.

7. The size of the at least one different OLED segment without the passive capacitor structure is 1.0 cm ２ 7. The OLED device according to claim 6,

8. 13. The OLED device of claim 1, wherein the bottom electrode of each OLED segment in the array is electrically connected to a dedicated power feed that controls light emission, the power feed being disposed laterally between the bottom electrode segments and electrically isolated from other power feeds and from any independent electrode segments.

9. 4. The OLED device of claim 3, wherein the bottom electrode segments of each OLED segment in the array are electrically connected to a single power feed that controls light emission, the power feed being disposed laterally between sections of the conductive layer and electrically isolated from other power feeds and sections of the conductive layer, and electrically isolated from the bottom electrode segments of any individual OLED segments by the insulating layer.

10. 10. The OLED device of claim 9, further comprising at least one power feed disposed to pass under at least one bottom electrode segment in a light emitting area of ​​the individual OLED segment.

11. 11. The OLED device of claim 10, wherein any dedicated power feeds disposed to pass under at least one bottom electrode segment in the light emitting area of ​​an independent OLED segment are connected to their corresponding bottom electrode segment through vias in the insulating layer.

12. 12. The OLED device of claim 11, wherein there are a plurality of power feeds beneath the bottom electrode segment of the independent OLED segment, the overlap between all of the power feeds and the bottom electrode of the independent OLED segment forming an associated passive capacitor structure, the bottom electrode segment being the top electrode of the passive capacitor structure, the insulating layer being the dielectric of the passive capacitor structure, and the plurality of power feeds collectively being the bottom electrode of the passive capacitor structure.

13. 13. The OLED device of claim 12, wherein in at least one independent OLED segment, the overlap area of ​​the plurality of power feeds of the associated passive capacitor and the bottom electrode segment increases the total capacitance of the independent OLED segment by at least 0.2 nF.

14. 14. The OLED device of claim 13, wherein a total overlap between the combined area of ​​the power feeds of the associated passive capacitors of the independent OLED segments and the overlying bottom electrode is greater than or equal to 30% of the area of ​​the bottom electrode segment.

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