Patent Publication Number: US-11665933-B2

Title: Power and data routing structures for organic light-emitting diode displays

Description:
This application is a continuation of U.S. patent application Ser. No. 17/321,243, filed May 14, 2021, which is a continuation of U.S. patent application Ser. No. 16/797,408, filed Feb. 21, 2020, now U.S. Pat. No. 11,257,883, which is a continuation of U.S. patent application Ser. No. 16/364,447, filed Mar. 26, 2019, now U.S. Pat. No. 10,629,664, which is a continuation of U.S. patent application Ser. No. 15/922,727, filed Mar. 15, 2018, now U.S. Pat. No. 10,312,309, which is a continuation of International Application PCT/US2017/014161, with an international filing date of Jan. 19, 2017, which claims priority to U.S. Provisional Patent Application No. 62/281,602, filed Jan. 21, 2016, and U.S. Provisional Patent Application No. 62/300,617, filed Feb. 26, 2016, which are hereby incorporated by reference herein in their entireties. 
    
    
     BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with organic light-emitting diode displays. 
     Electronic devices often include displays. For example, an electronic device may have an organic light-emitting diode display based on organic-light-emitting diode pixels. Each pixel may have a pixel circuit that includes a respective light-emitting diode. Thin-film transistor circuitry in the pixel circuit may be used to control the application of current to the light-emitting diode in that pixel. The thin-film transistor circuitry may include a drive transistor. The drive transistor and the light-emitting diode in a pixel circuit may be coupled in series between a positive power supply and a ground power supply. 
     Signals in organic-light-emitting diode displays such as power supply signals may be subject to undesired voltage drops due to resistive losses in the conductive paths that are used to distribute these signals. If care is not taken, these voltage drops can interfere with satisfactory operation of an organic light-emitting diode display. Challenges may also arise in distributing power and data signals in displays having layouts in which signal routing space is limited. 
     It would therefore be desirable to be able to provide improve ways to distribute signals such as power supply and data signals on a display such as an organic light-emitting diode display. 
     SUMMARY 
     An organic light-emitting diode display may have thin-film transistor circuitry formed on a substrate. The display and substrate may have rounded corners. A pixel definition layer may be formed on the thin-film transistor circuitry. Openings in the pixel definition layer may be provided with emissive material overlapping respective anodes for organic light-emitting diodes. 
     A cathode layer may cover the array of pixels. A ground power supply path may be used to distribute a ground voltage to the cathode layer. The ground power supply path may be formed from a metal layer that is shorted to the cathode layer using portions of a metal layer that forms the anodes for the diodes, may be formed from a mesh shaped metal pattern, may have L-shaped path segments, may include laser-deposited metal on the cathode layer, and may have other structures that facilitate distribution of the ground power supply. Mesh-shaped metal patterns (e.g., a metal power supply mesh path), metal patterns with L-shaped path segments, and other structures may also be used to facilitate distribution of positive power supply voltages. These power supply path structures may accommodate displays and substrates with rounded corners. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram of an illustrative electronic device having a display in accordance with an embodiment. 
         FIG.  2    is a diagram of an illustrative organic light-emitting diode pixel circuit in accordance with an embodiment. 
         FIG.  3    is a diagram of an illustrative organic light-emitting diode display in accordance with an embodiment. 
         FIG.  4    is a cross-sectional side view of a portion of an active area of an illustrative organic light-emitting diode display in accordance with an embodiment. 
         FIG.  5    is cross-sectional side view of a portion of an inactive border area of an illustrative organic light-emitting diode display in accordance with an embodiment. 
         FIG.  6    is a diagram showing an illustrative mesh pattern that may be used for a ground power supply path in a display in accordance with an embodiment. 
         FIG.  7    is a diagram showing how the ground power supply path of  FIG.  6    may be used in a display with rounded corners in accordance with an embodiment. 
         FIGS.  8 ,  9 , and  10    show illustrative power supply path layouts for a display with a flexible tail portion in accordance with an embodiment. 
         FIG.  11    is a top view of a corner portion of a display with positive and ground power supply path structures in accordance with an embodiment. 
         FIGS.  12  and  13    are cross-sectional side views of portions of the display of  FIG.  11    in accordance with an embodiment. 
         FIG.  14    is a top view of a corner portion of a display with positive and ground signal routing structures in accordance with another embodiment. 
         FIGS.  15 ,  16 , and  17    are cross-sectional side views of portions of the display of  FIG.  14    in accordance with an embodiment. 
         FIG.  18    is a diagram of an illustrative display having power supply paths formed from metal lines, mesh-shaped structures (e.g., a metal power supply mesh path), and strip-shaped paths in accordance with an embodiment. 
         FIG.  19    is a diagram showing how a display may have data lines with staircase-shaped portions to accommodate rounded display corners in accordance with an embodiment. 
         FIG.  20    is a cross-sectional side view of layers in an illustrative organic light-emitting diode display in accordance with an embodiment. 
         FIG.  21    is a top view of an illustrative display with a mesh of laser-deposited signal lines to reduce power supply voltage drops in accordance with an embodiment. 
         FIG.  22    is a cross-sectional side view of a portion of the display of  FIG.  21    in accordance with an embodiment. 
         FIGS.  23  and  24    are cross-sectional side views of a portion of the display of  FIG.  21    during fabrication in accordance with an embodiment. 
         FIGS.  25 ,  26 ,  27 , and  28    are top views of illustrative patterns that may be used for paths such as laser-deposited signal lines in a display such as the display of  FIG.  21    in accordance with an embodiment. 
         FIG.  29    is a diagram of illustrative gate driver circuitry formed from thin-film transistor circuitry on a display substrate in accordance with an embodiment. 
         FIG.  30    is a diagram of an illustrative display showing how gate driver row blocks may be laterally offset and rotated to accommodate display substrates with curved edges in accordance with an embodiment. 
         FIG.  31    is a diagram of an illustrative display showing how data line extensions that overlap an active area of a display may be used to route signals from diagonal data line segments to vertical portions of data lines in accordance with an embodiment. 
         FIG.  32    is a diagram showing how display driver circuitry such as gate driver row blocks may have different shapes in different rows to accommodate curved display substrate edges in accordance with an embodiment. 
         FIG.  33    is a diagram of illustrative display testing multiplexer circuitry of the type that may be formed from a portion of the thin-film transistor circuitry on a display substrate in accordance with an embodiment. 
         FIG.  34    is a diagram of an illustrative display showing how test signals may be routed between test pads at a lower edge of the display to testing multiplexer circuitry along an upper edge of the display in accordance with an embodiment. 
         FIG.  35    is a diagram of an illustrative display showing how testing multiplexer circuitry and test pads may be located along a portion of a display substrate tail on a lower edge of the display in accordance with an embodiment. 
         FIGS.  36  and  37    are diagrams of illustrative displays in which testing circuitry is arranged to accommodate a curved display substrate edge in accordance with embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative electronic device of the type that may be provided with an organic light-emitting diode display is shown in  FIG.  1   . Electronic device  10  may be a computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a display, a computer display that contains an embedded computer, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, or other electronic equipment. 
     As shown in  FIG.  1   , electronic device  10  may have control circuitry  16 . Control circuitry  16  may include storage and processing circuitry for supporting the operation of device  10 . The storage and processing circuitry may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitry  16  may be used to control the operation of device  10 . The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application specific integrated circuits, etc. 
     Input-output circuitry in device  10  such as input-output devices  12  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  12  may include buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, sensors, light-emitting diodes and other status indicators, data ports, etc. A user can control the operation of device  10  by supplying commands through input-output devices  12  and may receive status information and other output from device  10  using the output resources of input-output devices  12 . 
     Input-output devices  12  may include one or more displays such as display  14 . Display  14  may be a touch screen display that includes a touch sensor for gathering touch input from a user or display  14  may be insensitive to touch. A touch sensor for display  14  may be based on an array of capacitive touch sensor electrodes, acoustic touch sensor structures, resistive touch components, force-based touch sensor structures, a light-based touch sensor, or other suitable touch sensor arrangements. A touch sensor for display  14  may be formed from electrodes formed on a common display substrate with the pixels of display  14  or may be formed from a separate touch sensor panel that overlaps the pixels of display  14 . If desired, display  14  may be insensitive to touch (i.e., the touch sensor may be omitted). 
     Control circuitry  16  may be used to run software on device  10  such as operating system code and applications. During operation of device  10 , the software running on control circuitry  16  may display images on display  14 . 
     Display  14  may be an organic light-emitting diode display. In an organic light-emitting diode display, each pixel contains a respective organic light-emitting diode. A schematic diagram of an illustrative organic light-emitting diode pixel is shown in  FIG.  2   . As shown in  FIG.  2   , display pixel  22  may include light-emitting diode  38 . A positive power supply voltage ELVDD may be supplied to positive power supply terminal  34  and a ground power supply voltage ELVSS may be supplied to ground power supply terminal  36 . Diode  38  has an anode (terminal AN) and a cathode (terminal CD). The state of drive transistor  32  controls the amount of current flowing through diode  38  and therefore the amount of emitted light  40  from display pixel  22 . Cathode CD of diode  38  is coupled to ground terminal  36 , so cathode terminal CD of diode  38  may sometimes be referred to as the ground terminal for diode  38 . 
     To ensure that transistor  32  is held in a desired state between successive frames of data, display pixel  22  may include a storage capacitor such as storage capacitor Cst. A first terminal of storage capacitor Cst may be coupled to the gate of transistor  32  at node A and a second terminal of storage capacitor Cst may be coupled to anode AN of diode  38  at node B. The voltage on storage capacitor Cst is applied to the gate of transistor  32  at node A to control transistor  32 . Data can be loaded into storage capacitor Cst using one or more switching transistors such as switching transistor  30 . When switching transistor  30  is off, data line D is isolated from storage capacitor Cst and the gate voltage on node A is equal to the data value stored in storage capacitor Cst (i.e., the data value from the previous frame of display data being displayed on display  14 ). When gate line G (sometimes referred to as a scan line) in the row associated with display pixel  22  is asserted, switching transistor  30  will be turned on and a new data signal on data line D will be loaded into storage capacitor Cst. The new signal on capacitor Cst is applied to the gate of transistor  32  at node A, thereby adjusting the state of transistor  32  and adjusting the corresponding amount of light  40  that is emitted by light-emitting diode  38 . 
     If desired, the circuitry for controlling the operation of light-emitting diodes for pixels  22  in display  14  (e.g., transistors, capacitors, etc. in display pixel circuits such as the display pixel circuit of  FIG.  2   ) may be formed using configurations other than the configuration of  FIG.  2    (e.g., configurations that include circuitry for compensating for threshold voltage variations in drive transistor  32 , configurations in which an emission enable transistor is coupled in series with drive transistor  32 , configurations with multiple switching transistors controlled by multiple respective scan lines, configurations with multiple capacitors, etc.). The circuitry of pixel  22  of  FIG.  2    is merely illustrative. 
     As shown in  FIG.  3   , display  14  may include layers such as substrate layer  24 . Substrate  24  and, if desired, other layers in display  14 , may be formed from layers of material such as glass layers, polymer layers (e.g., flexible sheets of polyimide or other flexible polymers), etc. Substrate  24  may be planar and/or may have one or more curved portions. Substrate  24  may have a rectangular shape with left and right vertical edges and upper and lower horizontal edges or may have a non-rectangular shape. In configurations in which substrate  24  has a rectangular shape with four corners, the corners may, if desired, be rounded. Display substrate  24  may, if desired, have a tail portion such as tail  24 T. 
     Display  14  may have an array of pixels  22 . Pixels  22  form an active area AA of display  14  that displays images for a user. Inactive border portions of display  14  such as inactive areas IA along one or more of the edges of substrate  24  do not contain pixels  22  and do not display images for the user (i.e., inactive area IA is free of pixels  22 ). 
     Each pixel  22  may have a light-emitting diode such as organic light-emitting diode  38  of  FIG.  2    and associated thin-film transistor circuitry (e.g., the pixel circuit of  FIG.  2    or other suitable pixel circuitry). The array of pixels  22  may be formed from rows and columns of pixel structures (e.g., pixels formed from structures on display layers such as substrate  24 ). There may be any suitable number of rows and columns in the array of pixels  22  (e.g., ten or more, one hundred or more, or one thousand or more). Display  14  may include pixels  22  of different colors. As an example, display  14  may include red pixels that emit red light, green pixels that emit green light, and blue pixels that emit blue light. Configurations for display  14  that include pixels of other colors may be used, if desired. The use of a pixel arrangement with red, green, and blue pixels is merely illustrative. 
     As shown in the example of  FIG.  3   , display substrate  24  may have a tail portion such as tail  24 T that has a narrower width than the portion of substrate  24  that contains active area AA. This arrangement helps accommodate tail  24 T within the housing of device  10 . Tail  24 T may, if desired, be bent under the rest of display  14  when display  14  is mounted within an electronic device housing. 
     Display driver circuitry  20  for display  14  may be mounted on a printed circuit board that is coupled to tail portion  24 T or may be mounted on tail portion  24 T. Signal paths such as signal path  26  may couple display driver circuitry  20  to control circuitry  16 . Circuitry  20  may include one or more display driver integrated circuits and/or thin-film transistor circuitry. During operation, the control circuitry of device  10  (e.g., control circuitry  16  of  FIG.  1   ) may supply circuitry such as display driver circuitry  20  with information on images to be displayed on display  14 . To display the images on display pixels  22 , display driver circuitry  20  may supply corresponding image data to data lines D while issuing clock signals and other control signals to supporting display driver circuitry such as gate driver circuitry  18 . Gate driver circuitry  18  may produce gate line signals (sometimes referred to as scan signals, emission enable signals, etc.) or other control signals for pixels  22 . The gate line signals may be conveyed to pixels  22  using lines such as gate lines G. There may be one or more gate lines per row o pixels  22 . Gate driver circuitry  18  may include integrated circuits and/or thin-film transistor circuitry and may be located along the edges of display  14  (e.g., along the left and/or right edges of display  14  as shown in  FIG.  3   ) or elsewhere in display  14  (e.g., as part of circuitry  20  on tail  24 T, along the lower edge of display  14 , etc.). The configuration of  FIG.  3    is merely illustrative. 
     Display driver circuitry  20  may supply data signals onto a plurality of corresponding data lines D. With the illustrative arrangement of  FIG.  3   , data lines D run vertically through display  14 . Data lines D are associated with respective columns of pixels  22 . 
     With the illustrative configuration of  FIG.  3   , gate lines G (sometimes referred to as scan lines, emission lines, etc.) run horizontally through display  14 . Each gate line G is associated with a respective row of display pixels  22 . If desired, there may be multiple horizontal control lines such as gate lines G associated with each row of pixels  22 . Gate driver circuitry  18  may assert gate line signals on the gate lines G in display  14 . For example, gate driver circuitry  18  may receive clock signals and other control signals from display driver circuitry  20  and may, in response to the received signals, assert a gate signal on gate lines G in sequence, starting with the gate line signal G in the first row of display pixels  22 . As each gate line is asserted, data from data lines D is loaded into the corresponding row of display pixels. In this way, control circuitry in device  10  such as display driver circuitry  20  may provide pixels  22  with signals that direct pixels  22  to generate light for displaying a desired image on display  14 . 
     The circuitry of pixels  22  and, if desired, display driver circuitry such as circuitry  18  and/or  20  may be formed using thin-film transistor circuitry. Thin-film transistors in display  14  may, in general, be formed using any suitable type of thin-film transistor technology (e.g., silicon transistors such as polysilicon thin-film transistors, semiconducting-oxide transistors such as indium gallium zinc oxide transistors, etc.). 
     Conductive paths (e.g., one or more signal lines, blanket conductive films, and other patterned conductive structures) may be provided in display  14  to route data signals D and power signals such as positive power supply signal ELVDD and ground power supply signal ELVSS to pixels  22 . As shown in  FIG.  3   , these signals may be provided to pixels  22  in active area AA using signal routing paths that receive signals D, ELVDD, and ELVSS from tail portion  24 T of display  14 . 
     A cross-sectional side view of a portion of active area AA of display  14  showing an illustrative configuration that may be used for forming pixels  22  is shown in  FIG.  4   . As shown in  FIG.  4   , display  14  may have a substrate such as substrate  24 . Thin-film transistors, capacitors, and other thin-film transistor circuitry  50  (e.g., pixel circuitry such as the illustrative pixel circuitry of  FIG.  2   ) may be formed on substrate  24 . Pixel  22  may include organic light-emitting diode  38 . Anode AN of diode  38  may be formed from metal layer  58  (sometimes referred to as an anode metal layer). Each diode  38  may have a cathode CD from conductive cathode structures such as cathode layer  60 . Layer  60  may be, for example, a thin layer of metal such as a layer of magnesium silver with a thickness of 10-18 nm, more than 8 nm, less than 25 nm, etc. Layer  60  may cover all of pixels  22  in active area AA of display  14  and may have portions that extend into inactive area IA display  14  (e.g., so that layer  60  is coupled to ground power supply paths that supply layer  60  with ground power supply voltage ELVSS). 
     Each diode  38  has an organic light-emitting emissive layer (sometimes referred to as emissive material or an emissive layer structure) such as emissive layer  56 . Emissive layer  56  is an electroluminescent organic layer that emits light  40  in response to applied current through diode  38 . In a color display, emissive layers  56  in the array of pixels in the display include red emissive layers for emitting red light in red pixels, green emissive layers for emitting green light in green pixels, and blue emissive layers for emitting blue light in blue pixels. In addition to the emissive organic layer in each diode  38 , each diode  38  may include additional layers for enhancing diode performance such as an electron injection layer, an electron transport layer, a hole transport layer, and a hole injection layer. Layers such as these may be formed from organic materials (e.g., materials on the upper and lower surfaces of electroluminescent material in layer  56 ). 
     Layer  52  (sometimes referred to as a pixel definition layer) has an array of openings containing respective portions of the emissive material of layer  56 . An anode AN is formed at the bottom of each of these openings and is overlapped by emissive layer  56 . The shape of the diode opening in pixel definition layer  52  therefore defines the shape of the light-emitting area for diode  38 . 
     Pixel definition layer  52  may be formed from a photoimageable material that is photolithographically patterned (e.g., dielectric material that can be processed to form photolithographically defined openings such as photoimageable polyimide, photoimageable polyacrylate, etc.), may be formed from material that is deposited through a shadow mask, or may be formed from material that is otherwise patterned onto substrate  24 . The walls of the diode openings in pixel definition layer may, if desired, be sloped, as shown by sloped sidewalls  64  in  FIG.  4   . 
     Thin-film circuitry  50  may contain transistor such as illustrative transistor  32 . Thin-film transistor circuitry such as illustrative thin-film transistor  32  of  FIG.  4    may have active areas (channel regions) formed from a patterned layer of semiconductor such as layer  70 . Layer  70  may be formed from a semiconductor layer such as a layer of polysilicon or a layer of a semiconducting-oxide material (e.g. indium gallium zinc oxide). Source-drain terminals  72  may contact opposing ends of semiconductor layer  70 . Gate  76  may be formed from a patterned layer of gate metal or other conductive layer and may overlap semiconductor  70 . Gate insulator  78  may be interposed between gate  76  and semiconductor layer  70 . A buffer layer such as dielectric layer  84  may be formed on substrate  24  under shield  74 . A dielectric layer such as dielectric layer  82  may cover shield  74 . Dielectric layer  80  may be formed between gate  76  and source-drain terminals  72 . Layers such as layers  84 ,  82 ,  78 , and  80  may be formed from dielectrics such as silicon oxide, silicon nitride, other inorganic dielectric materials, or other dielectrics. Additional layers of dielectric such as organic planarization layers PLN 1  and PLN 2  may be included in thin-film transistor structures such as the structures of transistor  32  and may help planarize display  14 . 
     Display  14  may have multiple layers of conductive material embedded in the dielectric layers of display  14  such as metal layers for routing signals through pixels  22 . Shield layer  74  may be formed from a first metal layer (as an example). Gate layer  76  may be formed from a second metal layer. Source-drain terminals such as terminals  72  and other structures such as signal lines  86  may be formed from portions of a third metal layer such as metal layer  89 . Metal layer  89  may be formed on dielectric layer  80  and may be covered with planarization dielectric layer PLN 1 . A fourth layer of metal such as metal layer  91  may be used in forming diode via portion  88  and signal lines  90 . In active area AA, a fifth layer of metal such as anode metal layer  58  may form anodes AN of diodes  38 . The fifth metal layer in each pixel may have a portion such as via portion  58 P that is coupled to via portion  88 , thereby coupling one of the source-drain terminals of transistor  32  to anode AN of diode  38 . A sixth layer of metal (e.g., a blanket film) such as cathode metal layer  60  may be used in forming cathode CD for light-emitting diode  38 . Anode layer  58  may be interposed between metal layer  91  and cathode layer  60 . Layers such as layer  58 ,  91 ,  89 ,  76 , and  74  may be embedded within the dielectric layers of display  14  that are supported on substrate  24 . If desired, fewer metal layers may be provided in display  14  or display  14  may have more metal layers. The configuration of  FIG.  4    is merely illustrative. 
     It is desirable to minimize ohmic losses (sometimes referred to as IR losses) when distributing power signals to pixels  22  to ensure that display  14  operates efficiently and produces images with even brightness across display  14 . Ohmic losses may be minimized by incorporating low-resistance signal pathways into through display  14 . 
     Some of the layers of display  14  such as cathode layer  60  may be thin. Cathode layer  60  may be formed from a metal such as magnesium silver. To ensure that cathode CD is sufficiently thin to be transparent, the thickness of layer  60  may be about 10-18 nm (or other suitable thickness). In this type of configuration, the sheet resistance of layer  60  may be relatively large (e.g., about 10 ohm/square). To reduce the sheet resistance of the cathode and thereby allow ground power supply voltage ELVSS to be distributed to the cathode terminals of diodes  38  in pixels  22  with minimal IR losses, display  14  may be provided with supplemental conductive paths. Such paths may also help display  14  of  FIG.  4    (or displays with other types of thin-film stackups) accommodate display geometries with geometries that constrain signal distribution (e.g., displays with rounded corners, etc.). 
     With one illustrative configuration, portions of metal layer  91  may be used in forming signal paths such as signal paths  90  that serve as a supplemental ELVSS path (i.e., a signal path that can operate in parallel with the ELVSS path formed by cathode layer  60 ) and thereby help to minimize voltage drops and IR losses when operating display  14 . Metal layer  91  may be shorted to cathode layer  60  along one or more of the edges of display  14  (e.g., along the left, right, and bottom edges, along two or more edges, three or more edges, etc.) and may provide a low resistance path between a source of signal ELVSS on tail  24 T and respective edges of cathode layer  60  (i.e., there may be less resistance experienced when distributing a signal to the edge of layer  60  through signal lines in layer  91  than when distributing a signal to this portion of layer  60  through the thin metal of layer  60  itself). Reducing IR losses as power is supplied to layer  60  helps reduce power losses when driving diodes  38  in active area AA. The use of a portion of layer  91  to form part of the ground power supply path for distributing ELVSS in display  14  may also make it possible to reduce the width of inactive area IA. 
       FIG.  5    is a cross-sectional side view of a portion of inactive area IA of display  14  showing how a supplemental ELVSS power distribution path (path  90 ) may be shorted to cathode layer  60  through a portion of the same metal layer (metal layer  58 ) that is used in forming anodes AN in active area AA. As shown in  FIG.  5   , cathode layer  60  may be coupled to anode metal layer  58  through an opening in pixel definition layer  52 . Anode metal layer  58  may, in turn, be shorted to a portion of metal layer  91  that forms supplemental path  90  through an opening in planarization layer PLN 2 . Peripheral signal lines in inactive area IA such as signal lines  86  (e.g., signals lines associated with gate line signals, signals for gate driver circuitry  18 , and/or other signals for display  14 ) may be formed from portion of metal layer  89  under path  90 . Dielectric layer  92  may cover portions of lines  86 , if desired. Lines  86  may be formed on dielectric layer  80  or other dielectric, which may, in turn, be formed on thin-film circuitry and substrate structures  94  (see, substrate  24  and the dielectric and metal layers of circuitry  50  of  FIG.  4   ). With the arrangement of  FIG.  5   , ELVSS path  90  may be stacked on top of other signal lines such as lines  86 , which allows the width of inactive area IA to be minimized. 
       FIG.  6    is a top view of display  14  showing how ELVSS path  90  may be have a mesh shape with openings to accommodate anodes AN. ELVSS path  90  may be shorted to cathode  60  along edges  96  of display  14 , using shorting paths of the type shown in  FIG.  5    and may, if desired, be shorted to cathode  60  using vias in active area AA. When supplemental ground power supply paths such as the mesh-shaped path (metal power supply mesh path)  90  of  FIG.  6    are included in display  14 , the sheet resistance of the ground path for ground power supply signal ELVSS may be reduced (e.g., to less than 0.1 ohm/square or other suitable value). If desired, supplemental ground paths  90  for signal ELVSS may have non-mesh shapes (e.g., paths  90  may include vertical lines, horizontal lines, L-shaped segments, combinations of horizontal and vertical lines, sparse meshes, dense meshes, combinations of mesh structures and non-mesh structures, or other suitable shapes). The mesh shape for path  90  of  FIG.  6    is merely illustrative. 
     As illustrated in  FIG.  7   , display  14  may have features such as rounded corners that limit the amount of space available for signal paths. In this type of situation, strips of metal for path  90  may extend along edges  96  and may be shorted to cathode layer  60 . At corners  98 , there may not be sufficient room to form peripheral strips of metal layer  91 . Nevertheless, due to the presence of the mesh-shaped portions of metal layer  91  (i.e., the mesh shaped portions of path  90 ), there will be a low resistance path for ELVSS (e.g., a path that shorts the strip of metal associated with path  90  on the lower edges  96  of display  14  to the strips of metal associated with path  90  on the left and right edges of display  14 , etc.). If desired, ELVDD paths in display  14  may be provided with mesh-shaped metal traces (e.g., portions of the metal traces that are used in forming gate metal layer  76 , signal lines  86 , source drain layer  91 , anode metal layer  58 , and/or cathode metal layer  60  may be used in forming a low-resistance mesh-shaped positive power supply distribution path for ELVDD such as a path having a shape of the type shown by the ELVSS traces of  FIG.  6   ). For example, a mesh such as the mesh shaped portions of path  90  (a metal power supply mesh path) may be used as an ELVDD path. 
       FIGS.  8 ,  9 , and  10    show illustrative patterns for forming ELVSS and ELVDD distribution lines from tail portion  24 T to the lower edge  96  of display  14 . With arrangements such as these in which power lines ELVDD and ELVSS are routed along the center of tail  24 T, power routing may be performed away from dimension-constrained portions of display  14  such as corners  98 . 
       FIGS.  11 ,  12 ,  13 ,  14 ,  15 ,  16 , and  17    show illustrative arrangements for distributing positive power supply voltage ELVDD and ground power supply voltage ELVSS at corners  98  of display  14 . As shown in  FIG.  11   , lower edge  96  of display  14  may be provided with horizontal ELVSS distribution path  100 H (e.g., a strip of metal that runs along the lower edge of display  14 ) and vertical edges  96  of display  14  may be provided with vertical ELVSS distribution paths (e.g., strips of metal that run along the left and right edges of display  14 ) such as path  100 V. 
     Paths  100 H and  100 V may be formed from metal layer  89 . There may be a gap between paths  100 H and  100 V at corners  98  of display  14  (e.g., display  14  and substrate  24  may have rounded corners that limit the space available for power supply distribution at corners  98 ). Using L-shaped paths formed from portions of metal layer  91  at corners  98  and other conductive paths, path  100 H may be shorted to each path  100 V. For example, metal layer  91  may have a portion such as portion  90 - 1  that is shorted to path  100 H, connections  90 - 3  that short metal layer  91  to metal layer  89  in path  100 V, and L-shaped segments  90 - 2  that short portion  90 - 1  to respective connection points  90 - 3 . Positive power supply (ELVDD) path  102 H (e.g., a positive power supply strip-shaped path formed from a strip of metal that runs parallel to one of the strips of metal that form the ELVSS paths along the edges of display  14 ) may be shorted directly to some vertical ELVDD distribution paths such as vertical lines  104 - 1  (formed in layer  89 ). Other vertical ELVDD distribution paths such as vertical lines  104 - 2  are disconnected from path  102 H at corners  98  due to the rounded shape of display  14  at corners  98 , but can be reconnected to path  102 H using L-shaped path portions such as path  90 - 5  that are coupled between contacts on path  102 H (see, e.g., contact  90 - 4 ) and contacts  90 - 6  that short metal layer  91  of L-shaped paths  90 - 5  to metal layer  89  of vertical lines  104 . L-shaped paths may be used in distributing ELVSS, L-shaped paths may be used in distributing ELVDD (e.g., in configurations in which a mesh-shaped ELVDD path is used in display  14 , configurations in which metal strips such as paths  100 H and  100 V are used as part of an ELVDD path, and/or in other configurations). 
       FIGS.  12  and  13    are cross-sectional side views of display  14  of  FIG.  11    taken along lines A′-A and B′-B, respectively. As shown in  FIGS.  12  and  13   , planarization layer material (e.g., planarization layer PLN 1 ) may separate the metal layer  91  of segments  90 - 2  and segments  90 - 5  from metal lines in layer  89 . 
     In the illustrative arrangement of  FIG.  14   , path  100 H and path  102 H have been formed from two layers of metal ( 89  and  91 ). The cross-sectional side views of  FIGS.  15 ,  16   , and  17  (corresponding to cross-sectionals taken along A-A′, B-B′, and C-C′ of  FIG.  14   , respectively) show how planarization layer PLN 1  may be used to separate upper metal layer  91  in segments  90 - 2  and  90 - 5  from underlying metal lines. If desired, the paths formed from segments  90 - 2  and/or segments  90 - 5  may be implemented using mesh-shaped paths, as shown in  FIG.  18   . 
     Data line distribution paths near corners  98  may be constrained for space due to the shape of corners  98 . Data lines D may be accommodated at corners  98  by using a ladder shape (staircase shape) for data lines D at corners  98 , as shown by staircase-shaped data line portions D′ of data lines D in  FIG.  19   . At the transition between the main portion of substrate  24  and tail portion  24 T of substrate  24 , data lines portions D″ may extend diagonally. 
       FIG.  20    is a cross-sectional side view of a portion of display  14  with pixels  22  of multiple colors (see, e.g., red pixel  22 R, green pixel  22 G, and blue pixel  22 B). In this illustrative configuration of display  14 , each pixel has an anode AN formed from layer  58 , a hole injection layer (HIL) that is formed from a blanket film, first hole transport layer HTL 1  (a partially common layer), second hole transport layer HTL 2  (a blanket film common to all pixels), emissive material EML, a common electron transport layer (ETL), a cathode CD including blanket cathode layer  60 , and a capping layer CPL (e.g., a tuning layer of about 70 nm in thickness or other suitable thickness). 
       FIG.  21    is a top view of an active area of display  14  in an illustrative configuration in which display  14  has pixels such as pixels  22 R,  22 G, and  22 B of  FIG.  20   . As shown in  FIG.  21   , blanket cathode metal layer  60  may overlap all of the pixels in the active area of display  14 . Layer  60  may be formed from a metal such as magnesium silver or other suitable metal and may be sufficiently thin (e.g., 10-18 nm, more than 8 nm, less than 25 nm, etc.) to be transparent to light  40  emitted by diodes  38  in the pixels. Layer  60  may be used to distribute ground power supply voltage ELVSS to cathodes CD of diodes  38 . Due to the relatively small thickness of layer  60 , layer  60  may have a relatively high sheet resistance (e.g., about 10 ohm/square). To reduce the sheet resistance of the cathode layer in the arrangement of  FIG.  21   , supplemental cathode paths such as metal lines  128  (e.g., vertical and/or horizontal lines) may be incorporated into the cathode. Lines  128  may be deposited using any suitable metal deposition technique. For example, lines  128  may be deposited using a laser deposition system in which metal for lines  128  is ablated from a target and redeposited onto the exposed surface of cathode layer  60  in a vacuum chamber. 
       FIG.  22    is a cross-sectional side view of display  14  taken along line  120  and viewed in direction  122 . As shown in  FIG.  22   , light-emitting diode  38  may have an anode AN and cathode CD. Cathode CD may be formed from a portion of blanket cathode metal layer  60 . Supplemental lines  128  (e.g., horizontal and/or vertical supplemental lines that form a mesh pattern or other suitable pattern) may be formed on layer  60  and shorted to layer  60  and may therefore reduce the sheet resistance of the cathode path being used to distribute ground power supply voltage ELVSS to light-emitting diodes  28 . With one illustrative arrangement, the thickness D 1  of layer  60  is about 10-18 nm (e.g., more than 8 nm, less than 25 nm, etc.) and the thickness D 2  of line  128  is 10 times greater than D 1  (e.g., D 2  may be 5 times D 1  or more, may be 20 times D 1  or less, etc.). 
       FIGS.  23  and  24    show how a laser deposition system may be used to deposit metal lines  128  onto metal layer  60 . As shown in  FIG.  23   , a target such as target  130  may be placed adjacent to the surface of display  14  after cathode metal layer  60  has been deposited over the surface of display  14 . Target  130  may include a transparent substrate (e.g., glass) such as transparent substrate  134 , a layer of heat absorbing material such as layer  136 , and a layer of high conductivity material such as layer  138 . Heat absorbing layer  136  may be formed from low-reflectivity metals (e.g., molybdenum, tungsten, etc.) or other suitable materials that absorb laser beam  140  when laser beam  140  is emitted by laser  132 . Laser beam  140  may include ultraviolet light, visible light, and/or infrared light and may be have a diameter of 1-1.2 microns, more than 1 micron, less than 5 microns, or other suitable size. Beam  140  may be a pulsed laser beam (e.g., a beam having a pulse width of 1 fs to 100 ps or more than 100 ps) to facilitate heating of the illuminated portion of heat absorbing layer  136 . Layer  138  may be formed from a highly conductive metal such aluminum, zinc, magnesium, silver, etc. Configurations in which more than two layers of metal or only a single layer of metal are formed on substrate  134  may also be used. 
     As shown in  FIG.  24   , when laser  132  applies laser light  140  to target  130 , portions  138 ′ and  136 ′ of layers  138  and  136  are heated and portions  138 ′ and  136 ′ are ablated or otherwise removed from target  130  and redeposited on adjacent portions of layer  60  in display  14 . The deposited metal of portions  138 ′ and  136 ′ forms conductive line  128  to help reduce the sheet resistance of the conductive structure (i.e., the cathode layer) that is used in distributing ground voltage ELVSS to diodes  38 . 
       FIGS.  25 ,  26 ,  27 , and  28    are top views of display  14  showing illustrative patterns that may be used for supplemental cathode lines  128  (e.g., laser-deposited metal lines). Lines  128  may have a uniform vertical or horizontal layout (see, e.g., illustrative vertical lines  128  of  FIG.  25   ), may have a non-uniform vertical or horizontal layout (see, e.g., illustrative vertical lines  128  of  FIG.  25   ), or may have uniform ( FIG.  27   ) or non-uniform ( FIG.  28   ) mesh shapes. Other patterns or combinations of these patterns may be used in forming lines  128  if desired and may be used in combination with cathode structures formed from metal layer  91  (e.g., paths  90  of  FIG.  6   ). The configurations of  FIGS.  25 ,  26 ,  27 , and  28    are merely illustrative. 
       FIG.  29    is a diagram showing how gate driver circuitry  18  may have regions of circuitry for driving horizontal control signals (gate signals) onto horizontal gate lines G of display  14 . As shown in  FIG.  29   , for example, gate driver circuitry  18  may have blocks of gate driver circuitry such as gate driver row blocks  150  that are interconnected using paths  158 . Each gate driver row block  150  may include circuitry such as output buffers and other output driver circuitry  152 , register circuits  154  (e.g., registers that can be chained together by paths  158  to form a shift register), and paths  156  (e.g., signal lines, power lines, and other interconnects). Each gate driver row block  150  may supply one or more gate signals to one or more respective gate lines in a corresponding row of the pixels of the array of pixels in the active area of display  14 . 
       FIG.  30    shows how gate driver row blocks  150  may be laterally offset (e.g., by providing blocks  150  with varying horizontal offsets DX along a dimension parallel to the horizontal axis along which gate lines G run) and/or may be rotated into different angular orientations (e.g., by rotating blocks  150  so that they have angular orientations with varying angular offsets DA) to accommodate curved edge  98  of display substrate  24 . Gate driver circuitry with laterally varying gate driver row block positions and/or angularly varying gate driver row block orientations may include a unique lateral position and/or angular orientation for each block  150  or may use a set of two or more different lateral positions and/or angular orientations to enhance the ability of gate driver circuitry  18  to accommodate curved display substrate edges. Control signals (e.g., clocks signals and other timing signals) may be supplied to gate driver circuitry using gate driver circuitry control lines such as lines  18 L that extend along tail portion  24 T of substrate  24 . 
     As shown in  FIG.  31   , data lines D may have L-shaped data line extensions such as extension  170  that help distribute data signals to vertical data lines D that are located at curved corner  98  of display substrate  24  without consuming excessive inactive border area. Extensions  170  may be formed in the active area of display  14 . As shown in  FIG.  31   , for example, data lines D on tail  24 L may include diagonal data line segments such as segments  164  and  166 . Segments  164  and  166  may be formed from the same layer of metal or may be patterned from two or more different metal layers. As an example, alternate diagonal segments such as segments  164  and  166  may be formed from respective first and second gate metal layers to enhance packing density. Data line portions  164  and  166  may be coupled to vertical data line portions such as lines D that are formed in a metal layer such as second source-drain metal layer  91  using vias  162 . Pixels  22  may include vias such as illustrative via  160  to connect data lines formed from metal layer  91  (i.e., D (metal layer  91 ) of  FIG.  31   ) to internal paths in pixels  22  formed from metal layer  89  (i.e., source and drains for transistors in pixels  22 ). Power lines formed from metal layer  89  may be interleaved with data lines D (metal layer  91 ). L-shaped extensions  170  may be formed from metal layer  91  and may overlap the corner of the active area of display  14 , so as not to intrude into the inactive area along the edge of the substrate of display  14 . 
       FIG.  32    is a diagram showing how display driver circuitry such as gate driver row blocks  150  may have different shapes in different rows to accommodate curved display substrate edges such as the curved portion of substrate  24  at corner  98 . As shown in  FIG.  32   , blocks  150  may, for example, be rectangular blocks of assorted shapes with varying aspect ratios (i.e., the vertical dimension divided by the horizontal dimension of each block  150  may potentially differ). As an example, some of blocks  150  may have relatively small aspect ratios (see, e.g., the block having small height A 1  and large width B 1 ) whereas other blocks  150  may have relatively large aspect ratios (see, e.g., the block having moderate height A 2  and moderate width B 2 ). Circuitry  152 ,  154 , and  158  in blocks  150  can be arranged to accommodate custom footprints (outlines when viewed from above) for each block  150  or for each set of blocks  150 . In general, any suitable type of customization of blocks  150  may be implemented around curved display edges such as corner  98  (e.g., shape customization, lateral offset customization, angular orientation customization, size customization, circuit component customization, etc.). Blocks  150  may each be customized or sets of blocks may be customized to accommodate the curved display substrate edge. 
     Testing circuitry may be implemented on display  14 . For example, testing multiplexer circuitry such as testing multiplexer circuitry  176  of  FIG.  33    may be provided along the upper or lower edge of display  14 . Circuitry  176  may be used to route a relatively small number of test signals onto a relatively large number of data lines to facilitate pixel testing during manufacturing. During testing, switches SW may be selectively operated to provide test data to data lines D in display  14 . For example, switches SW of circuitry  176  may be opened and closed to route test data for red data lines D(R) such as TESTDATARED to red data lines D(R), to route test data for green data lines D(G) such as TESTDATAGREEN to green data lines D(G), and to route test data for blue data lines D(B) such as TESTDATABLUE) to blue data lines D(B). Lines D(R) may be used to route data to red pixels, lines D(G) may be associated with green pixels, and lines D(B) may be coupled to the blue pixels of display  14 . 
     Test data may by supplied to display  14  from tester that is coupled to test pads on substrate  24  and/or from circuitry attached to substrate  24 . External tester schemes may be used when it is desired to perform testing before attaching a display driver integrated circuit to substrate  24 . Test lines may route signals (e.g., TESTDATARED, TESTDATAGREEN, TESTDATABLUE and three corresponding multiplexer control signals for the red, green, and blue switches in switches SW) between the test pads and testing circuitry such as circuitry  176 . Circuitry  176  may be controlled by an external test circuit or other controller so that data lines of different colors can receive test data in desired patterns. This allows pixels  22  of different colors in display  14  to be independently tested. When testing is complete, switches SW can be left permanently opened so that the data lines D in display  14  are not shorted together and can be used normally to route data signals to pixels  22 . 
       FIG.  34    is a diagram of an illustrative display with testing circuitry. As shown in  FIG.  34   , testing multiplexer circuitry  176  and test pads  174  may be located on opposing edges of display  14 . For example, test pads  174  may be located on tail portion  24 L of substrate  24  at the lower edge of display  14  and testing multiplexer circuitry  176  may be located along the upper edge of display  14 . Test signal lines  172  may be used to route test signals between test pads  174  on the lower edge of display  14  to testing multiplexer circuitry  176  along the upper edge of display  14 . 
     As shown in the illustrative configuration of  FIG.  35   , testing multiplexing circuitry  176  may be located along the lower edge of tail portion  24 T of substrate  24  adjacent to pads  174 . Following testing, testing multiplexing circuitry  176  and pads  174  may be removed from tail  24 T (e.g., by cutting off circuitry  176  and pads  174  using a cut formed in tail  24 T along cut line  180  of  FIG.  35   ). 
       FIGS.  36  and  37    show how multiplexer testing circuitry  176  may be accommodated along a curved portion of display  14 . In the illustrative arrangement of  FIG.  36   , circuitry  176  is formed within a curved and tapered region along the curved edge of the active area of display  14  between blocks  150  of gate driver circuitry  18  and data lines D.  FIG.  37    shows an illustrative configuration in which regions of testing multiplexer circuitry  176  such as testing multiplexer circuit blocks  176 B are interspersed with regions of gate driver circuitry  18  such as gate driver row blocks  150 . By placing blocks  176 B between respective pairs of blocks  150 , gate driver circuitry  18  and testing multiplexer circuitry  176  may be efficiently packed along the edge of the active area. This helps minimize the width of the inactive area along the edge of substrate  24  in which display driver circuitry  18  and testing multiplexer circuitry  176  are formed. Testing multiplexer circuit blocks  176 B may have varying location-dependent shapes (e.g., different sizes, aspect ratios, etc.), angular orientations, and/or lateral positions along a dimension parallel to gate lines G, as described in connection with gate driver circuitry  18  of  FIG.  30    to help enhance the layout of the circuitry in the inactive area of display  14 . Other arrangements in which regions of texting multiplexer circuitry  176  are located between regions of gate driver circuitry  18  or are otherwise arranged to help accommodate curved display substrate edges may be used, if desired. The configuration of  FIG.  37    is illustrative. 
     In accordance with an embodiment, an organic light-emitting diode display having an active area with an array of pixels is provided that includes a substrate, thin-film transistor circuitry on the substrate that includes dielectric layers, a pixel definition layer on the thin-film transistor circuitry, the pixel definition layer has openings each of which contains an organic emissive layer for an organic light-emitting diode and each of which is associated with a respective one of the pixels, and a cathode layer that covers the array of pixels, and a metal ground power supply path embedded within dielectric layers in the active area, the metal ground power supply path carries a ground power supply voltage to the cathode layer. 
     In accordance with another embodiment, the metal ground power supply path is formed from a first portion of a metal layer and a second portion of the metal layer forms via structures that contact source-drain terminals of transistors in the thin-film transistor circuitry. 
     In accordance with another embodiment, the metal ground power supply path or positive power supply path has a mesh shape. 
     In accordance with another embodiment, the active area has rounded corners and the metal ground power supply path or positive power supply path forms a mesh with rounded corners. 
     In accordance with another embodiment, the metal ground power supply path or positive power supply path includes L-shaped portions. 
     In accordance with another embodiment, the organic light-emitting diode display includes first and second patterned metal layers embedded in the dielectric layers, the metal ground power supply path includes metal segments formed from the second patterned metal layer and the first patterned metal layer includes strips of metal that carry the ground power supply voltage. 
     In accordance with another embodiment, the display has edges and the strips of metal run along at least some of the edges. 
     In accordance with another embodiment, the first patterned metal layer includes a positive power supply strip of metal that runs parallel to one of the strips of metal that carry the ground power supply voltage. 
     In accordance with another embodiment, the metal segments include L-shaped portions and at least some of the L-shaped portions cross over the positive power supply strip of metal. 
     In accordance with another embodiment, the organic light-emitting diode display includes positive power supply distribution paths that extend to the pixels across the active area from the positive power supply strip of metal. 
     In accordance with another embodiment, the active area has rounded corners and the L-shaped portions are located at the rounded corners. 
     In accordance with another embodiment, source-drain terminals for transistors in the thin-film transistor circuitry are formed from a first metal layer embedded in the dielectric layers and the metal ground power supply path is formed from a second metal layer embedded in the dielectric layers. 
     In accordance with another embodiment, anodes for the organic light-emitting diodes are formed from a third metal layer that is embedded in the dielectric layers and that is interposed between the second metal layer and the cathode layer. 
     In accordance with another embodiment, a portion of the third metal layer shorts the metal ground power supply path formed from the second metal layer to the cathode layer. 
     In accordance with another embodiment, the metal ground power supply path includes laser-deposited metal lines. 
     In accordance with another embodiment, the organic light-emitting diode layer includes data lines that supply data to the pixels, the data lines include staircase-shaped portions. 
     In accordance with an embodiment, an organic light-emitting diode display having an array of pixels is provided that includes a substrate, a layer of thin-film transistor circuitry on the substrate, a pixel definition layer on the layer of thin-film transistor circuitry, the pixel definition layer has openings each of which contains an organic emissive layer for an organic light-emitting diode and each of which is associated with a respective one of the pixels, a cathode layer that covers the array of pixels and that distributes a ground power supply voltage to the organic light-emitting diode in each of the openings, and a patterned metal mesh that is shorted to the cathode layer and that helps distribute the ground power supply voltage. 
     In accordance with another embodiment, the patterned metal mesh includes laser-deposited metal lines on the cathode layer. 
     In accordance with another embodiment, the cathode layer is formed from a first layer of metal, the patterned metal mesh is formed from a second layer of metal, and anodes for the organic light-emitting diodes are formed from a third layer of metal that is interposed between the first and second layers of metal. 
     In accordance with another embodiment, the organic light-emitting diode display includes laser-deposited metal lines on the cathode layer. 
     In accordance with another embodiment, the substrate has rounded corners. 
     In accordance with another embodiment, the organic light-emitting diode display includes data lines that distribute data signals to the pixels, the data lines include portions with staircase shapes. 
     In accordance with an embodiment, an organic light-emitting diode display having an array of pixels is provided that includes a substrate, a layer of thin-film transistor circuitry having dielectric layers on the substrate, a pixel definition layer on the layer of thin-film transistor circuitry, the pixel definition layer has openings each of which contains an organic emissive layer for an organic light-emitting diode and each of which is associated with a respective one of the pixels, and a cathode layer that covers the array of pixels, the cathode layer receives a ground power supply voltage and distributes the ground power supply voltage to the organic emissive layers in the openings, a first metal layer embedded in the dielectric layers that forms source-drain terminals for thin-film transistors in the layer of thin-film transistor circuitry, a second metal layer embedded in the dielectric layers that is patterned to carry the ground power supply voltage to the cathode layer, and a third metal layer that has a first portion that is patterned to form anodes for the organic light-emitting diodes and a second portion that shorts the second metal layer to the cathode layer. 
     In accordance with another embodiment, the substrate has curved edges. 
     In accordance with another embodiment, the organic light-emitting diode display includes data lines that convey data to the array of pixels, gate lines that extend perpendicular to the data lines, and gate driver circuitry formed from the thin-film transistor circuitry, the gate driver circuitry has gate driver row blocks that are each coupled to at least a respective one of the gate lines. 
     In accordance with another embodiment, the gate driver row blocks include gate driver row blocks of different aspect ratios. 
     In accordance with another embodiment, the organic light-emitting diode display includes testing multiplexer circuitry including blocks of testing multiplexer circuitry between respective pairs of the gate driver row blocks. 
     In accordance with an embodiment, an organic light-emitting diode display is provided that includes thin-film transistor circuitry, a substrate having an active area with an array of pixels formed from a portion of the thin-film transistor circuitry and having an inactive area that is free of pixels and that runs along an edge of the active area adjacent to an edge of the substrate, data lines that supply data to the array of pixels, gate lines that run perpendicular to the data lines and that supply control signals to the array of pixels, and gate driver circuitry in the inactive area this is formed from a portion of the thin-film transistor circuitry, the gate driver circuitry runs along a curved portion of the edge of the substrate. 
     In accordance with another embodiment, the gate driver circuitry has a plurality of gate driver row blocks each of which is coupled to at least one of the gate lines in a respective row of pixels in the array of pixels. 
     In accordance with another embodiment, the gate driver row blocks include first and second gate driver row blocks with different shapes in respective first and second rows of the pixels. 
     In accordance with another embodiment, the gate driver row blocks include first and second gate driver row blocks with different angular orientations in respective first and second rows of the pixels. 
     In accordance with another embodiment, the gate driver row blocks include gate driver row blocks in different rows of the pixels that are offset by different amounts along a dimension running parallel to the gate lines so that the gate driver row blocks accommodate the curved portion of the edge of the substrate. 
     In accordance with another embodiment, the organic light-emitting diode display includes testing multiplexer circuitry that is coupled to the data lines. 
     In accordance with another embodiment, the testing multiplexer circuitry runs along at least part of the curved portion of the edge of the substrate. 
     In accordance with another embodiment, the testing multiplexer circuitry includes regions of testing circuitry between the gate driver row blocks. 
     In accordance with another embodiment, the data lines include L-shaped data line portions. 
     In accordance with another embodiment, the data lines have data line portions extending perpendicular to the gate lines and some of the data lines each have a diagonal portion and an L-shaped extension coupling the diagonal portion to a respective one of the data line portions extending perpendicular to the gate lines. 
     In accordance with an embodiment, an organic light-emitting diode display is provided that includes thin-film transistor circuitry, a substrate having an active area with an array of pixels formed from a portion of the thin-film transistor circuitry and having an inactive area that is free of pixels and that runs along an edge of the active area adjacent to an edge of the substrate, gate driver circuitry formed from a portion of the thin-film transistor circuitry in the inactive area, gate lines that supply control signals to the array of pixels from the gate driver circuitry, and data lines that supply data to the array of pixels, the data lines have data line portions extending perpendicular to the gate lines and some of the data lines each have a diagonal portion and an L-shaped extension coupling the diagonal portion to a respective one of the data line portions extending perpendicular to the gate lines. 
     In accordance with another embodiment, the edge of the substrate has a curved portion, the organic light-emitting diode display includes power supply lines having L-shaped segments that overlap the active area. 
     In accordance with another embodiment, the gate driver circuitry includes a plurality of gate driver row blocks each of which supplies at least one of the control signals to a respective one of the gate lines, the gate driver row blocks include gate driver row blocks with different shapes along the curved portion. 
     In accordance with another embodiment, the gate driver circuitry includes a plurality of gate driver row blocks each of which supplies at least one of the control signals to a respective one of the gate lines, the gate driver row blocks include gate driver row blocks with different angular orientations along the curved portion. 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.