Split OLED with electrostatic discharge 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 concurrently 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 May 25, 2021, with Attorney Docket No. OLWK-0024-PCT and Attorney Docket No. OLWK-0024-USP. [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 the failure of electronic components, which 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. Sensitive electronic components must be protected during and after manufacturing, during shipping / handling, during device assembly, and in the finished device. ESD is often particularly problematic when the device is in the "off" or non-operating state.

[0003] Some common methods for providing ESD protection to OLED devices include ESD protection as part of the driving circuitry (see, for example, U.S. Patent No. 6,244,999), adding peripheral conductive structures (see, for example, U.S. Patent No. 6,244,999), adding separate ESD protection circuits (see, for example, U.S. Patent No. 6,244,999), and using capacitors or transistors outside the light-emitting area (see, for example, U.S. Patent No. 6,244,999). 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 for preventing ESD is to use materials that are not highly conductive but that slowly conduct or dissipate static electricity. Such dissipative materials are generally 10 12They have a resistance of less than an ohm-meter. Such materials can conduct electricity, but they do so very slowly, so that accumulated static charge can dissipate without a sudden discharge that could damage the internal structure of an electronic device.

[0004] Not all electronic devices are equally sensitive to ESD damage; it can depend on the application or environment involved. For example, electronic components assembled in a sealed module under controlled conditions may be less susceptible to ESD damage, but the same electronic components may be sensitive if handled manually. Furthermore, ESD has levels; 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 devices. 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 specific capacitance of an OLED would be high enough to dissipate ESD without damaging the OLED or its associated circuitry. However, the specific capacitance depends on, among other factors, the area size of the OLED, so for large OLED devices (e.g., typically 25 cm²), 2OLEDs for general lighting applications (e.g., OLEDs with areas greater than 100µm) may have 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 200-300µm) 2 The individual pixels in active-matrix and passive-matrix OLED displays (which have an area of ​​1000 Å) 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 easy 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 circuits where adding ESD protection circuitry is problematic from the standpoint of cost and ease of manufacture. 2 OLEDs under 0.5cm, especially 2 OLEDs below this threshold 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 pre-fabricated separately, including its own substrate (except for 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. Specifically, a split OLED is one in which each individual OLED segment is fabricated directly on the same substrate, completely side-by-side or in an array. Non-emissive gaps or spaces exist between the individual segments. Such split OLED light sources can offer manufacturing and cost advantages because many layers can be shared among all the individual units, eliminating the need to handle and package individual OLED panels.

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

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

[0013] Applications such as automotive taillights often require some degree of side visibility in addition to direct visibility from the rear, so taillight assemblies often have complex designs that mix 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 offer 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, which must be individually patterned. One cost-effective way to fabricate the power leads is to use photolithography processes and techniques, which can create very fine patterns of conductive structures. However, photolithography is generally not compatible for use on organic OLED layers. Fine metal masking processes and techniques can be used to form power lines on top of the organic OLED layers, but this is costly and prone to defects during manufacturing. Additionally, the conductive structures created by masking processes are significantly larger than those that can be created by photolithography.

[0016] In bottom-emitting OLEDs with split bottom 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, any location presents tradeoffs. While the power feeds can be placed laterally adjacent to the electrode segments (separated by insulating material to maintain non-contact), this can undesirably increase the spacing between the electrode segments (due to the number of individual power feeds required) and can easily lead to short circuits between the power feed of one electrode segment and the power feed of a second electrode segment. While the power feeds can be placed below the electrode segments, they must be electrically isolated from the electrode segments above them to avoid short circuits. This can complicate manufacturing by requiring an additional layer. Furthermore, if the power feed is in the light emission path, it may be visible, which is undesirable.

[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, which is more difficult to achieve with the transparent encapsulant required for top-emitting OLEDs, especially for flexible OLEDs. Bottom-emitting OLEDs allow for the use of a very robust encapsulant, since the encapsulant on the non-emitting side does not need to be transparent. Second, OLEDs are installed in limited spaces, so heat buildup can be an issue. Bottom-emitting OLEDs allow for 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, reducing thermal conductivity and reducing cooling efficiency.

[0018] However, at least some OLED segments in a split device may be small enough to be sensitive to ESD damage, and because such small OLED segments may have only simple direct electrical connections 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 is not 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 segmented OLED device in which electrostatic protection is provided by a passive capacitor on the substrate: a continuous, opaque conductive layer (composed of Cr / Al / Cr and opaque) as one electrode, an insulating layer (composed 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. Because the conductive layer is composed of a conductive metal, it is not suitable for bottom-emitting devices. Furthermore, the opaque conductive layer is located under all electrode segments. This arrangement may also be susceptible to manufacturing defects, particularly pinholes in the insulating layer that can cause short circuits between electrode segments. This document does not disclose the location of the power feed, an important consideration.

[0020] Patent Document 5 describes a bottom-emission OLED display in which the drive circuit for each pixel includes a storage capacitor with a transparent anode / insulating layer / transparent conductive layer structure located in the light-emitting path. This document explains that the transparent conductive layer is patterned as a wiring line or patterned only below the anode. However, if the transparent conductive layer (the lower electrode of the capacitor) were part of the wiring line, the transparent capacitor would be part of the drive circuit for that pixel, and therefore the transparent conductive layer could not be connected to other pixels in the display, rendering such a device inoperable. Patent Document 6 also describes a bottom-emission OLED display in which the drive circuit for each pixel includes a storage capacitor with a transparent anode / insulating layer / transparent conductive layer structure. This document explains that the transparent storage capacitor also has a "retention capacitance," and that if the "retention capacitance" is larger than the storage capacitance required for OLED operation, it can stabilize the write voltage to the storage capacitor. Other documents describing bottom-emitting OLED displays in which the drive 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 the following: U.S. Patent No. 5,623,299; ... and U.S. Patent No. 5,623,299. However, in all of the above documents, the transparent capacitor is part of the drive circuitry and is the same size as the pixel, which may not increase the overall capacitance sufficiently to prevent ESD damage.

[0021] Patent documents 15 and 16 describe segmented OLEDs with conductive tracks extending through the device and contacting hole injection tracks. Patent document 16 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 issue of IR drop. A similar concept of a conductive layer with a varying thickness to address IR drop is disclosed in Patent document 17.

[0022] US Pat. No. 5,699,499 describes a segmented OLED with conductive tracks arranged between the segments.

[0023] US Pat. No. 5,699,499 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. 10,692,957 B2 [Patent Document 2] U.S. Patent No. 7,944,140 B2 [Patent Document 3] U.S. Patent No. 9,246,121 B2 [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. 10,825,883 B2 [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] U.S. Patent No. 20150214249A1 [Patent Document 11] U.S. Patent No. 9,385,171 B2 [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. Patent No. 9,487,878 [Patent Document 17] U.S. Patent No. 9,159,945 [Patent Document 18] U.S. Patent 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, each OLED segment forming a light-emitting 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, 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 each other.

[0029] In any of the above OLED devices, the overlap area between 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 between 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 segment having an associated passive capacitor structure, the bottom electrode segment of at least one different OLED segment in the array has no overlap with the conductive layer section, such that the at least one different OLED segment does not have an associated passive capacitor structure. The size of the at least one different 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 positioned 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 segment of each OLED segment in the array is 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 other power feeds and conductive layer sections, and from the bottom electrode segment of any individual OLED segment by an 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, at least one independent OLED segment has a plurality of power feeds beneath its bottom electrode 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. For at least one independent OLED segment, the overlap area of ​​the plurality of power feeds and the bottom electrode segment of the associated passive capacitor structure increases the total capacitance of the independent OLED segment by at least 0.2 nF, or the total overlap area of ​​the 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. [Effects of the Invention]

[0034] The described bottom-emitting split OLED device 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 an unpowered state, but also maximizes the total light-emitting area of ​​the device by locating the passive capacitor structure directly below the split electrode. [Brief explanation of the drawings]

[0035] [Figure 1A] 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 underneath all of the OLED segments. Power feeds are located 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 underneath some of the OLED segments. Power feeds are located 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 segmented 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. Power feeds are located laterally of the electrode segments. [Figure 3B] 3 is a cross-sectional view of a segmented OLED device 300. FIG. [Figure 4A] 4 is a top view of a split OLED device 400 of the present invention having five segments with a conductive layer that is the bottom electrode of a passive capacitance and that is positioned under a portion of the OLED segments along with a power feed. [Figure 4B] 4 is a cross-sectional view of a segmented 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 segments along with a power feed, with 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] 6 is a partial top view along one side of a segmented OLED device 600 in which multiple power feeds pass under the segmented electrodes without electrical contact. [Figure 6B] 6 is a partial cross-sectional view of a segmented 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 susceptibility.

[0036] The diagram is not to scale. DETAILED DESCRIPTION OF THE INVENTION

[0037] For purposes of this disclosure, the terms "over" or "above" mean that the relevant structure is located above another structure, i.e., on the side opposite the substrate. "Top" or "upper" refers to the side or surface farthest from the substrate, while "lower," "bottom," "lower," "under," or "bottom" refers to the side or surface closest to the substrate. Unless otherwise specified, "over" should be interpreted to mean that two structures may be in direct contact or that there may be an intermediate layer between them. It should be understood that a "layer" has two sides or surfaces (top and bottom), that multiple layers may be present, and is not limited to a single layer. "LEL" always refers to a single light-emitting layer. A "unit" generally refers to at least one layer that can be considered to act as a single light source; a unit may be equivalent 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 may 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 may be called a "two-stack" device. A stacked OLED may 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 620-660 nm range), G indicates a layer or unit that emits primarily green light (500-600 nm, preferably in the 540-565 nm range), and B indicates a layer or unit that emits primarily blue light (<500 nm, preferably in the 440-485 nm range). It is important to note that R, G, and B layers may emit some light outside the indicated ranges, but the amount is always less than the primary colors. Y (yellow) indicates that the layer or unit emits significant amounts of both R and G light, and significantly less 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 a three or more OLED stack, 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 filter out 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 can have a single light-emitting layer or multiple light-emitting layers (directly adjacent to each other or separated from each other by interlayers). Individual light-emitting units can also include various types of non-emissive layers known in the art, such as hole-transporting layers, electron-transporting layers, and blocking layers, 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 an OLED unit can also be a combination of two primary colors, particularly a yellow-emitting OLED unit that produces light that is a combination of R and G. 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. White light, even if it does not contain equal amounts of R, G, and B light, can generally be produced in an OLED by having three separate R, G, and B light-emitting layers, two separate light-emitting layers such as blue and yellow, or even a single white light-emitting layer. Red-emitting OLEDs are generally classified as 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 a desired color.

[0042] In certain applications, such as automotive taillights used to signal braking, stopping, turning, and other functions, the light output of the OLEDs used must be selected to meet all applicable government regulations and SAE or industry standards, particularly in terms of color and brightness. Additionally, the size and dimensions of the split OLED devices must be selected to comply with all applicable government regulations and industry standards. For such taillight applications, the preferred emission color is red.

[0043] Segmented OLED devices, consisting of multiple individual OLED segments on a common substrate, can have any desired shape. They can be entirely flat or planar, have multiple planar surfaces angled relative to one another, entirely curved, or a mixture of flat, angled, and curved surfaces. Segmented OLED devices are often mounted in a housing or module, along with any necessary external power connections and control elements to provide signals or power to the individual segments. The housing or module will typically have a transparent portion that transmits light from the OLED device and protects it from the external 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 segmented 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 can be used for lighting purposes, with all segments activated simultaneously to provide uniform emission (except for gaps between segments). The emission of all segments can be constant, dimmed all at once, brightened all at once, or flashing. Alternatively, split OLED devices can have each segment activated individually and independently in some pattern. This pattern can include some segments fully lit, some segments at intermediate brightness levels, and some segments off. The pattern can be constant over a period of time, or it can vary, with individual segments 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 considerable distance, individual OLED segments are often as small as individual pixels (typically emitting areas of 0.1 mm) in high-resolution displays. 2(much smaller than 500cm). Preferably, the total emitting area is 500cm. 2 For the following small split OLED devices, the individual OLED segments are at least 0.025 cm 2 , preferably at least 0.05 cm 2 It is desirable that the total light-emitting area is 500cm. 2 For larger segmented devices, the individual OLED segments must be at least 0.05 cm 2 , more preferably at least 0.5 cm 2 The light emitting area should be 1.0 mm.

[0045] The individual OLED segments can be of any shape or area as desired. Generally, the segments form a packed array to minimize non-emissive space between the individual segments. Desirably, the array is regular so that the spacing between the segments is uniform, providing a smooth appearance. The array can have any overall shape and need not be square or rectangular, but can also be circular, elliptical, triangular, or polygonal. In some designs, some areas of the array are regular with uniform spacing between them, while other parts of the array are irregular. For example, in a square array, the outer area of ​​the array can have smaller square segments arranged in a uniform pattern, while the inner area has a single, larger, star-shaped segment in the exact center surrounded by a larger non-emissive area. Similarly, the shape of the individual OLED segments in the array is not limited, but can be square, rectangular, circular, elliptical, triangular, polygonal, or even irregular as desired.

[0046] Furthermore, the OLED segments in the array need not all be the same shape, but can have a mixture of shapes, such as interlocking triangles and hexagons. Packed arrays of all triangles, all parallelograms, or a mixture of triangles and hexagons or triangles and trapezoids are preferred. The individual segments do not all need to have the same area, and the array can 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 can be arranged in a specific pattern within the array. Preferably, the array of segments is asymmetric, i.e., includes segments of different sizes, and more preferably, the array includes segments of different sizes and shapes.

[0047] 1A is an overhead view of a segmented 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 2The OLED 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 segmented OLED device 100. Atop the transparent substrate 10 is a uniform transparent conductive layer 20 and a uniform transparent insulating layer 30. Both 20 and 30 are unpatterned. Above the insulating layer 30 are power feeds 15 electrically connected to electrode segment 1, 25 connected to electrode segment 2, 35 connected to electrode segment 3, 45 connected to electrode segment 4, and 55 connected to electrode segment 5, all of which occupy the same lateral plane. Between the electrode segments, and between adjacent power feeds or 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 contact points between the electrode segment and its designated power feed. On the surface of PDL 40 / electrode segments 1-5 is a top electrode 60, common to light-emitting organic layer 50 (not shown in this view). Over electrode 60 is an encapsulation layer 70. One end of each power feed and top electrode 60 extends outside encapsulation 70 to form a contact pad for individual connection to control circuitry for segmented OLED device 100. Between the OLED segments (and within the light-emitting area of ​​the array) are non-emissive gaps or spaces 80, which typically correspond to the location of PDL 40.

[0048] Figure 1B shows a cross-section of the segmented OLED device 100 along line Z-Z' in Figure 1A. Visible in this view are the light-emitting organic layer 50 and the continuous top electrode 60, which is common to all OLED electrode segments 1-5 and extends beyond the encapsulant 70 on one side to form an external contact pad for connection to control circuitry. Arrows indicate the direction of light emission from the 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 a PDL 40, forming a flat top surface across the electrode segments and the PDLs located between them. Between the electrode segments (e.g., between 3 and 5), the PDL 40 provides a non-emissive 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, among other factors, on the size of the bottom electrode segments, since the top electrode 60 is common to all. C OLED relates 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 includes an insulating layer 30 and a conductive layer 20, both of which are continuous and uniform on the top surface of the transparent substrate 10. This allows for the formation of a multiplanar 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 overlying OLED structure, it can still function as the bottom electrode of the passive capacitor structure because 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 between the bottom electrode segment and 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 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 different OLED segments, the passive capacitor structure of any one OLED segment follows the overlap between only the OLED's bottom electrode and the portion of the conductive layer directly below 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 because both structures share the OLED's bottom electrode. The conductive layer 20 (which is the bottom electrode of the passive capacitor structure) is not directly connected to any circuitry.

[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 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’ OLED structure having separate capacitor sections with individual capacitances 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 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 structure of another OLED segment, 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 through several paths. Charge can come from above or 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 static charge on a single bottom electrode segment is likely to be discharged, without mitigation, through a single OLED segment, or at most a few adjacent OLED segments, potentially damaging those OLED segments. Therefore, for 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 at 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 C P1’ In Figure 1C, this is connected in series with a parallel array of other capacitances, and then C P1’ OLED segments 2' to 5' 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 the passive capacitor structure (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 increases, 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 OLEDs of different sizes, 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] Because the size of an OLED segment is selected primarily to meet the device's light-emitting objectives and requirements, its inherent capacitance may be insufficient to protect against ESD damage; this capacitance can be increased within 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 associated with each passive capacitor structure. The addition of these passive capacitor structures increases the total capacitance, which reduces susceptibility to ESD damage. Because the total capacitance of the OLED segment is increased by adding passive capacitor structure(s), electrostatic charge can be better dissipated, thereby mitigating damage to the overlying organic layers of the 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 is 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 experiences from electrostatic discharge, so the voltage experienced by the OLED can be reduced by 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 100 kJ / s.

[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 0.5cm 2 The following OLED segments may be more susceptible to ESD damage because their inherent capacitance is not as high. Therefore, in a split OLED device with 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 be larger than its size (>1 cm). 2 ), ESD protection may not be necessary, but segments 1'-4' still require protection. Furthermore, 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 Figures 2A and 2B, which show a top view and a cross-sectional view, respectively, of an OLED device 200 similar to split OLED device 100, except that the passive capacitor structure is 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 manner similar to that 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 feed is 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 unpowered 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 that forms the passive capacitor structure is 100%. That is, the conductive layer 20 that provides the passive capacitor structure is equal to or larger in area than the corresponding electrode segment. The relative area of ​​the conductive layer 20 that forms 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%, when added to the intrinsic capacitance of the OLED, the overall capacitance may be sufficient to prevent ESD damage.

[0063] 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 with the conductive layer 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; that is, conductive layer 20, which forms the bottom electrode of the passive capacitor structure, overlaps only about 50% with each of the overlying electrode segments 1-4, which form the top 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 provided by the passive capacitor. Ideally, the overlap area between the conductive layer and the electrode segment 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 overlapping with the electrode segment (which is the top electrode of the second capacitor structure), or the total area of ​​all present conductive layer sections, 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 be undesirable to place power feeds between and laterally away from the electrode segments. Such placement 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 gap). Some power feeds may be too wide (to minimize IR drop along their length) to 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] FIG. 4A shows a top view of a segmented 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, and 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 below the non-emissive space between the electrode segments and are therefore not in the light-emitting path. Power feeds 15, 35, and 55 are connected to electrode segments 1, 3, and 5 through vias 32 in insulating layer 30 (vias for power feeds 25 and 45 are not shown).

[0068] However, this is not always possible because there may not be enough space in the non-emitting space 80 for the required number of power feeds. 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 underside of the electrode segments, preventing 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 feed under (and electrically isolate) one or more of the bottom electrodes of an OLED segment, even if they are located in the emissive path. This situation is illustrated in Figure 5A, which is a top view of a segmented OLED device 500, which is a heterogeneous array of seven individual OLED segments.

[0070] Segmented 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). On top of transparent substrate 10 are power feeds (15, 25, 35, 45, 55, 65, 75) for each corresponding electrode segment (1-7), all of which are located between three sections of the conductive layer (22, 24, 26). The power feeds are electrically insulated from each other and from conductive layer sections 22, 24, 26 by insulating layer 31. Not shown in FIG. 5A (but visible in FIG. 5B) is 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] Segmented OLED device 500 has 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', thereby providing ESD protection. However, OLED segment 4' has three different secondary 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 capacitances of the three 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 fabrication and installation. However, some of the power feeds must then be located directly underneath bottom electrode segment 4 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' in Figure 5B. In this embodiment, power feeds 55, 65, and 75 are all located 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 OLED segment 4' of split OLED device 500, there is an additional passive capacitor structure formed between 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 these power feeds (which feed 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, because ESD protection is required when the device is not operating, such an arrangement can still increase the total capacitance of the OLED segment.

[0074] In the illustrative example of split OLED device 500, there are only three power feeds (which are relatively thin in width due to the array of only 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 because each of the corresponding passive capacitor structures is small. In this example, the overlap area between power feeds 55, 65, and 75 and 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 segmented OLED device may have many individual segments, e.g., 100 to 1000 segments. Because 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, with such large device sizes, the power feeds may need to span long distances, necessitating increased power feed width (and overall conductivity) to prevent IR drop. In such cases, OLED segments on or near the side of the array where the contact pads are located may have many power feeds for other segments located underneath the electrode segment. A total overlap area of ​​an electrode segment and all underlying power feeds of at least 30%, more preferably at least 50%, and most preferably at least 70% 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 shows a top view of a substructure of a large split OLED device 600, with power feeds 601-615 all passing under a single, independent electrode segment 1 without making electrical contact. This creates 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; 601, 604, 607, 610, and 613 are all wider than the others. These wider power feeds connect to electrode segments relatively far from the edges, and the wider widths help minimize IR drop.

[0077] In this case, when the device is not operating, the overlap of each power feed (which acts as the bottom electrode of the passive capacitor structure) with the electrode segment above it (which acts as the common top electrode of the passive capacitor structure) forms multiple passive capacitor structures, with each power feed connected to a different OLED segment. Because the OLED segments of the array are all connected in parallel, the passive capacitance to an OLED segment is the total overlap capacitance of all underlying power feeds with the overlying (common) electrode segment, plus the sum of the capacitances of the other 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 formation of passive capacitor structures by the power feeds and electrode segments, plus the capacitance of other independent OLED segments with the same power feed underneath) 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 other figures) is not required 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 above them, combined with the OLED's inherent capacitance, is sufficient to provide ESD protection for this particular OLED segment. In effect, there are enough power feeds to act together as the bottom electrodes of passive capacitor structures sufficient to protect the overlying independent OLED segments when the device is not in operation, so a separate conductive layer section is not required. Power feeds 601-615 can be disposed directly on transparent substrate 10. An insulating layer 30, which functions as a shared dielectric layer for the passive capacitor structures, is located between and above the power feeds, so 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 individual 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 individual OLED segments, more preferably under at least five individual segments, and most preferably under ten or more individual 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 and has a uniform thickness. The top surface of the substrate faces the OLED. Because the substrate is part of the overall encapsulation of the OLED, it must be sufficiently impermeable to air and water to ensure the OLED has a desired lifetime. The substrate can be rigid or flexible. The substrate can have various types of underlayers (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 functions as the lower electrode of a passive capacitor structure, separated by an insulating layer from the bottom electrode segment of the OLED segment (which functions 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 for a particular OLED segment, which would increase the overall capacitance. The passive capacitor structure's mere presence can provide a sump or reservoir for holding ESD voltages. In particular, the passive capacitor structure does not participate in the 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 merely serves to aid in the dissipation of ESD charges through the contribution of the capacitance of the entire array. In some cases, the conductive layer may be connected to ground to allow faster dissipation, or it may be isolated from the power supply for 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 because it is in the light-emitting path of the OLED segments. The conductive layer can be made of a thin metal layer such as silver or copper; a conductive metal oxide such as ITO, AZO, IZO, GZO, ZnO, TiN, or SnO2; an organic material such as PEDOT:PSS, CNT (carbon nanotubes), or graphene; or conductive particles such as silver, nickel, or copper suspended in a polymer binder (conductive ink), or any combination of these materials. The conductive layer may incorporate auxiliary structures such as metal gridlines to improve conductivity. The conductive layer may be composed of multiple layers. Preferably, the conductive layer is a conductive metal oxide, particularly ITO or AZO.

[0084] Ideally, the thickness of the conductive layer is 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 entire 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 located only beneath 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 the edges, or internal openings, resulting in a single, continuous layer.

[0086] The conductive layer 20 may also be patterned in sections, with one section being a continuous layer that underlies only some but not 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 so that individual sections are located only directly beneath 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 above two or more different conductive layer segments. The different sections of the conductive layer may be laterally separated by non-conductive or insulating material. There may also be OLED segments in the array that do not have a conductive layer beneath the bottom electrode segment of the OLED structure. In such instances, there is no overlap.

[0087] Because 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 which case the bottom electrode of the OLED structure also serves as the top electrode of a passive capacitor structure within the same OLED segment. Because 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, so 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 in which power feeds for individual OLED segments are located below 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 feed (i.e., the OLED segments are in the "off" state). In this way, the power feeds can serve the same purpose and function as conductive layer 20 with respect to ESD protection in these embodiments. However, it is necessary that the total capacitance from the multiple passive capacitor structures formed between all power feeds and electrode segments provide sufficient passive capacitance so that, when added to the intrinsic OLED capacitance, the total capacitance provides sufficient ESD protection. It should be noted that if a power feed is electrically connected to the segmented 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 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 specific 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 10 mA may be connected to a 20 cm 2 to obtain the desired light output at the segment. 2 If required, this segment requires two power feeds (one from each driver, or one from each of the two channels of a multi-channel driver). Alternatively, 2 Although each segment can be driven by a single driver, the corresponding power feed can be split into two paths if necessary to accommodate other power feeds within the device. Such an arrangement can help distribute power more evenly across the segments or reduce IR drop. However, in some cases, the same power feed can be used for two or more segments. Segments that share a common power feed cannot be activated individually; they emit light together and are considered equivalent to a single segment.

[0091] The exterior of the encapsulant has external contact areas (also called contact pads) that electrically connect to each power feed inside the encapsulant. While the illustration shows the power feed extensions outside the encapsulant forming the contact areas, it is also 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 to these contact areas (i.e., by soldering or ACF) to provide power as needed to the power feeds and segment electrodes within the encapsulant. By providing the appropriate amount of power to the contact areas for the appropriate duration, the OLED segments emit light at the desired brightness for that duration. The power supplied to the external contact pads is determined by a controller or driver. It is highly preferred that all of the contact pads for each power feed be located along one side or edge of the substrate.

[0092] The location and distribution of 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 non-emissive areas (i.e., gaps between segments and / or the outer edges of the device), while other power feeds are located below the electrode segments and in the optical path. Depending on the design, some segments may have no power feeds located between or below them, while other segments may have multiple power feeds between or below them.

[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 their size (larger segments require more power to operate than smaller segments). However, IR drop can be minimized by adjusting the width (parallel to the substrate) or height (above the substrate) of the power feed. Therefore, in such cases, not all power feeds have the same width and height dimensions, which can also vary depending on their length. Furthermore, not all 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 made of a metal such as a thin layer of Ag.

[0094] If the power feed is not located within the light path, it may be opaque or transparent as needed. If it is located within the light path, it should be as transparent as possible. The power feed may be constructed from 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, or SnO2; organic materials such as PEDOT:PSS, CNTs (carbon nanotubes), or graphene; or conductive particles such as silver, nickel, or copper suspended in a polymer binder (conductive ink), or any combination of these materials. Intrinsically opaque conductive materials (i.e., silver) may be in the form of nanowires or meshes, so that the power feed structure has openings that allow some light to pass through, or may be thin enough to not be opaque. Ideally, the power feed should have a resistivity of less than 25 ohms / square, 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] Generally, the conductive material of which the conductive layer or power feed is composed 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 can lead to a visible difference in light emission or a reduction in 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 a split OLED device whose refractive index is more similar in magnitude to that 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 0.05. 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 ) is preferably in the range of 1.00 to 1.06. The inclusion of the refractive index-lowering material makes the light emission from each segment of the device appear more uniform. It is important that the refractive index-lowering material and layer are electrically non-conductive. R I Note that only the difference in is important, not which material is high and which is low.

[0097] To form passive capacitor structures having either the conductive layer 20 or the power feed as the bottom electrode and 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 structure can be an insulating layer 30, which can be patterned or unpatterned as needed. The insulating layer 30 can also be present outside the overlap area between the conductive structure that functions as the bottom passive capacitor structure electrode and the electrode segment that functions as the top electrode of the passive capacitor structure. In some embodiments, a section of an auxiliary insulating layer 31 can be present. For example, the insulating layer 31 can be used to fill and electrically isolate the conductive layer 20, the power feed, and the conductive layer, or to provide planarization between different sections of the power feed. 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 conductive layer 20 or power feed, insulating layer 30 (and 31, if present), and electrode segments depends on the composition and thickness of dielectric insulating layer 30 (and 31, if present), and the amount of overlap between the capacitor electrodes. Thus, the thickness and composition of 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] The insulating layer 30 or 31 is preferably transparent and non-light-scattering. The insulating material should have an electrical resistance of 1 megohm (MΩ) or greater, more preferably 2 megohms or greater. Because the insulating layer is in the light-emitting path, the insulating material should have a refractive index ratio in the range of 1.00 to 1.06 with respect to the conductive material of the passive capacitor structure electrodes. 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 a power feed is located in the lateral space between electrode segments, electrical contact between the power feed and the electrode segment is typically made on the side of the electrode segment. When a power feed is located below an electrode segment, electrical connection between the power feed and the overlying segmented electrode is made through a via, which is a hole or passageway in the insulating material (i.e., insulating layer 30 or 31) separating them. The via runs from the top of the power feed to the bottom or side of the segmented electrode. Ideally, the via connects to the segmented electrode at a location corresponding to the non-emitting area of ​​the segmented OLED. The via can be formed by patterning the overlying insulating material to leave at least a portion of the power feed's top surface exposed or uncovered. Alternatively, the via can be formed by uniformly depositing the overlying insulating material on the power feed and then 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 from 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 conductivity through the connection.

[0102] The length and area of ​​the vias are not critical but should be sufficient to supply the required power to the segmented electrodes. The vias can be of any shape along the top surface of the power feed. In particular, the vias can extend along the length of the power feed. There can also 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 OLED segments in the array share the same substrate and are fabricated together on that substrate as an array. On all sides (except those located along the outer edge 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 at least 70%, or more preferably at least 80%. However, for some applications (i.e., microcavity devices), the transparent bottom electrode only needs to be semi-transparent and partially reflective. The bottom transparent electrode can be made of any conductive material, but a thin layer of a metal oxide such as ITO or AZO, or a metal such as Ag, is preferred. Optionally, an auxiliary electrode may be present to help distribute charge more uniformly 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-defining layer (PDL) is present to separate a portion of one OLED segment from another OLED segment or along the periphery of the array. The PDL can be used to separate 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 gaps between electrode segments, a PDL located along the periphery of the array may still be present. 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 upper 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 also covers a portion of the top surface of the electrode surface. In such cases, the PDL can 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, preferably in the range of 0.2 to 3.0 microns.

[0108] Figure 7 shows a typical configuration of the light-emitting OLED layer types 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] An optional hole injection layer (HIL, layer 501) may be present above the transparent electrode segment 514. 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 contain dopants to modify their properties. They are non-emissive and therefore do not contain 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. An example of a suitable HIL material is HAT-CN.

[0110] Disposed above the HIL (layer 501) is 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. An example of a suitable HTL is NPB.

[0111] An optional exciton-blocking layer (EBL, layer 503) is disposed above the HTL (layer 502). The light-emitting layer may emit 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 contain dopants to modify their properties. They are non-emissive and therefore do not contain emissive materials. Multiple EBLs may be present. 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 emissive dopants. Suitable host materials and fluorescent, phosphorescent, and TADF emissive dopants for use in the light-emitting layer or unit are well known and commonly used. Light-emitting units as defined above can also be used for emission. The selection of appropriate materials is not critical and any may be selected based on their performance and emission characteristics.

[0113] An optional hole-blocking layer (HBL, layer 505) is disposed above the LEL1 (layer 504). Light-emitting layers emit light through the formation of excitons, which in some cases may not form quickly enough before holes migrate toward the cathode. The purpose of the HBL is to confine holes to the LEL, maximizing light emission. Suitable hole-blocking materials are well known and commonly used. These layers may be mixtures of such materials or may contain dopants to modify their properties. Because they are non-emissive, they do not contain any emissive materials. Multiple HBLs may be present. 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 individual OLED light-emitting units and typically consists of multiple layers. This is because the CGL generates electrons and holes when a voltage is applied, which are then injected into the adjacent organic light-emitting layer. Therefore, the use of a CGL can potentially convert one injected electron into multiple photons, resulting in higher brightness. In particular, a CGL is preferably disposed between each light-generating unit in the stack. However, it is not necessary to have adjacent CGLs on both sides of the light-generating unit. The top and bottom OLED light-generating units in the stack typically have only one adjacent CGL. While it is not typically necessary to use a CGL between the light-emitting unit and either the top or bottom electrode, a CGL can be used if desired.

[0115] Many different types of CGLs have been proposed and may be used in OLED stacks. See, for example, U.S. Patent No. 7,728,517 and U.S. Patent Application Publication No. 2007 / 0046189. To form a CGL, an np semiconductor heterojunction located at the interface between the n-type and p-type layers is typically required for charge generation. Therefore, the CGL may 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 CGLs is MoO3. In some instances, the n- and p-layers may be separated by a thin interlayer. Often, the CGL is arranged so that the n-layer is closest to the anode and the p-layer is closest to the cathode.

[0116] One desirable CGL formulation has three layers: an electron-transporting material doped with an n-dopant (e.g., Li), a thin interlayer of the same (but undoped) electron-transporting material, and a hole-transporting material doped with a p-dopant. Another desirable CGL formulation has the same type of doped ETL with an interlayer of a different electron-transporting material and an electron-deficient hole-injecting material such as HAT-CN. Another desirable CGL formulation has an undoped ETL layer, a layer of Li or Ca, an interlayer 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-transporting materials, hole-injecting or transporting 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 an appropriate material is not critical and may be based on its performance. The thickness of the CGL should desirably be in the range of 200 to 450 Å, although in some instances, thinner CGLs may be in the range of 100 to 200 Å. Often, the CGL has 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), representing the second stack of the OLED device. In Figure 7, the two LELs (layers 504 and 507) are separated by the CGL (layer 506); thus, the OLED stack of Figure 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] Above LEL2 (layer 507) is disposed at least one HBL (layer 508) similar to that described as layer 505.

[0120] Disposed above the HBL (layer 508) is an electron transport layer (ETL, layer 509). The purpose of the ETL is to manage the transport of electrons from the HBL 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 contain dopants to modify their properties. They are non-emissive and therefore do not contain 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] An optional electron injection layer (EIL, layer 510) is disposed above the ETL (layer 509). 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 layer (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, or Mg / Ag. The top electrode can be deposited by any known technique. The top electrode may be patterned in the non-emissive areas, but is typically deposited uniformly over the emissive areas. For external power, a contact area (contact pad) outside the encapsulant is required, electrically connecting to the top electrode within the encapsulant. Some examples of suitable materials for the top electrode are Al, Al / Mg, Ag / Mg, and Ag.

[0123] An optional protective or spacing layer (layer 511 in Figure 7) may be present 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 be in direct contact with the substrate. The encapsulant should be impermeable to air and water. The encapsulant may be transparent or opaque. The encapsulant should 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] An example of in-situ formation is thin film encapsulation, which involves depositing multiple layers of alternating inorganic and polymeric materials 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 achieved using a preformed sheet or cover slip affixed 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 affixed 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, which may require an additional sealant, such as solder or glass frit. The side and bottom edges of the cover slip may be specially designed to better fit the sealing area or promote a better seal. The cover slip and sealing area may be designed together so that they partially snap or lock 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, a greater degree of sealing is required, which 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 seal, but also acts as a heat sink to prevent excessive heating that would be detrimental to the OLED device.

[0128] For 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 Figure 7) are required. Generally, adding another OLED stack (i.e., two units instead of one) doubles the brightness but also doubles the power requirements. A three-stack OLED provides three times the brightness but requires three times the power, and so on. In the split OLED devices of the present invention, as many stacks as necessary to achieve the desired brightness can be added, the only limitation being the increase in voltage required to drive the device. Desirably, split OLED devices have at least two stacks, and as many as six stacks.

[0129] Another way to increase the brightness of OLEDs, especially when monochromatic emission is desired, is to incorporate the microcavity effect. To create a microcavity, one electrode is made reflective and the other is made semi-transparent, causing 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 can emit white or multimodal light, and color filters can be used to create the desired emission color for each specific segment. The various individual LELs or units within a segmented 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 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 proportion of certain wavelengths than others (i.e., some units produce a spectrum rich in short red wavelengths, while others produce a spectrum rich in 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: 1) depositing a layer of transparent conductive material on a transparent substrate, the conductive material forming the 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 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 comprises a passive capacitor structure for increasing the total capacitance, comprises, in order: 1) patterning a conductive transparent material and a conductive power feed on a transparent substrate, such that the power feed does not contact 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 which forms 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 the dielectric of the passive capacitor structure; 3) forming a via in the insulating layer above the power feed; 4) patterning transparent electrode segments on the insulating material such that there is one electrode segment per OLED segment connected to one power feed through a via, and at least one overlying electrode segment overlaps 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 the conductive layer to overlap at least two electrode segments; - Patterning the conductive layer to overlap fewer than all of the electrode segments, so 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 comprises a passive capacitor structure for increasing the total capacitance, comprises, in order: 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 the 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 the passive capacitor structure; 3) forming a via 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, the bottom electrode segment of one OLED segment overlapping at least a portion of a section of the 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, so 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 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 bottom-emitting split OLED devices include the following: Brightness: 2,000~20,000cd / m 2 , Number of OLED segments: >200 (can be a mixture of 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: <1 mm, preferably <700 μm, most preferably <200 μm; 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, and individual features from any of the embodiments can be combined without restriction, except where mutually exclusive.

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

[0137] Modeling and Experimental Results ESD reliability testing for split OLED devices used in automotive applications falls into various categories or models that correspond to scenarios the device may be exposed to. 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, typically 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 supplied 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 the test. [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 is the HBM test parameter 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 property of the organic stack and 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 100 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 calculate 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 is 6.8nF / cm 2 All of the examples were simple bottom-emitting OLEDs, and none included passive capacitor structures. [Table 2]

[0141] Calculated V OLED is the 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 It passed the ESD test, but it is 0.17cm 2 It was experimentally determined that many of the segments in this stack did not pass. LIM The data suggests that V is between 24 and 53V. LIM suggests that the voltages are around 40V and conservatively 120V for 2-stack and 6-stack OLEDs, respectively.

[0142] If capacitance protection is added, 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 required from Equation 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 a range PASSIVE are shown in Tables 3a to 3b and Tables 4a to 4b, respectively. PASSIVENegative values ​​of suggest that ESD protection is not 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 is 40V), then 0.38cm 2 and 0.25 cm 2 It is estimated that no additional capacitance is needed for a segment size of 0.17cm, but the latter of the two areas is close to the limit. 2 , 0.10cm 2 , 0.05cm 2 The segments have C values ​​of 1.21nF, 2.73nF, and 3.82nF per segment, respectively. PASSIVE V LIM The higher the value, the less C required. PASSIVE Naturally, V of 8kV will decrease. HBM For two-stack OLEDs, ESD protection is required under 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 The latter is not necessary, but the latter is close to the limit. Under these conditions, the 0.17cm of 6 stacks 2 , 0.10cm 2 , 0.05cm 2 The OLED segments have C values ​​of 0.41nF, 0.89nF, and 1.23nF per segment, respectively. PASSIVE It is calculated that 0.25cm is required. 2In the segment, V LIM For a 80V, C of 0.71nF per segment PASSIVE V LIM Higher values ​​require less C PASSIVE Naturally, V of 8kV will decrease. HBM For the six-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 = 8kV (see Table 2b). This is the V LIM ESD damage of 0.05cm for 6 stack segments is far greater than 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 by 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 maintain I below a threshold, it is desirable to increase the total capacitance compared to the OLED segment without the passive capacitor structure. Because 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 / direction 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 circuit, 100-400 split OLED device with 5 OLED segments, 500 split OLED device with 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 Capacitance of the associated OLED structure within 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, wherein each OLED segment forms a light-emitting 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; 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 segment and the conductive layer forming an associated passive capacitor structure; the bottom electrode segment of the OLED segment being the top electrode of the passive capacitor structure; the insulating layer being the dielectric of the passive capacitor structure; the conductive layer being the bottom electrode of the passive capacitor structure; and the conductive layer being connected to the conductive layer of another of the passive capacitor structures and not connected to any circuitry other than the conductive layer of another of the passive capacitor structures.

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, the overlap area between the section(s) of the conductive layer and the bottom electrode segment increases the total capacitance of the OLED segment by at least 0.2 nF.

5. 4. The OLED device of claim 2, wherein in at least one OLED segment, an overlap area between the section(s) of the conductive layer 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 the passive capacitor structure, the bottom electrode segment of at least one different OLED segment in the array does not have an overlap with the section of the conductive layer, such that the at least one different OLED segment does not have the passive capacitor structure associated with it.

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 of claim 6, wherein

8. 10. The OLED device of claim 1, wherein the bottom electrode segment 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 segment 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 of the bottom electrode segments in the 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 of the bottom electrode segments 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 segments of the independent OLED segments, the overlap between all of the power feeds and the bottom electrode segments of the independent OLED segments forming the passive capacitor structure, the bottom electrode segments being the top electrodes 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 electrodes of the passive capacitor structure.

13. 13. The OLED device of claim 12, wherein in at least one independent OLED segment, the overlap area between the plurality of power feeds of the passive capacitor structure 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 passive capacitor structures of the independent OLED segments and the overlying bottom electrode segment is equal to or greater than 30% of the area of ​​the bottom electrode segment.

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