Patent Publication Number: US-2022231106-A1

Title: Display panels and display devices

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 16/886,089, filed May 28, 2020, which claims priority to and the benefit of Korean Patent Application No. 10-2019-0154514 filed in the Korean Intellectual Property Office on Nov. 27, 2019, the entire contents of each of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     Display panels and display devices are disclosed. 
     2. Description of the Related Art 
     In a display panel, a plurality of subpixels are arranged in a matrix to display an image. In this case, a plurality of transistors for driving an active matrix are required for each subpixel. However, since the plurality of transistors are disposed on a substrate and occupy separate predetermined areas, the display area, that is, the aperture ratio, may be reduced. 
     SUMMARY 
     Some example embodiments provide a display panel capable of securing a high aperture ratio and displaying an improved display quality. 
     Some example embodiments provide a display device including the display panel. 
     According to some example embodiments, a display panel may include a substrate, a switching transistor on the substrate, and a light-emitting transistor. The switching transistor may include a first gate electrode, a first source electrode, a first active layer, and a first drain electrode. The light-emitting transistor may include a second gate electrode, a second source electrode, a second active layer, a light-emitting layer, and a second drain electrode. The second gate electrode may be the first drain electrode of the switching transistor. The switching transistor, the second source electrode, the second active layer, the light-emitting layer, and the second drain electrode may be stacked in a direction that is perpendicular to a surface of the substrate. 
     A channel length direction of the light-emitting transistor may be parallel to a gate voltage application direction of the light-emitting transistor. 
     The first source electrode, the first active layer, and the first drain electrode may be stacked vertically with respect to the first gate electrode. 
     A channel length direction of the switching transistor may be parallel to a gate voltage application direction of the switching transistor. 
     The first active layer may be overlapped with the second active layer in the direction perpendicular to the surface of the substrate. 
     The first gate electrode, the first source electrode, the first active layer, the first drain electrode, the second source electrode, the second active layer, the light-emitting layer, and the second drain electrode may be overlapped with each other in the direction perpendicular to the surface of the substrate. 
     The display panel may further include a first gate insulating layer between the first gate electrode and the first source electrode, and a second gate insulating layer between the first drain electrode and the second source electrode. 
     The display panel may further include a pixel definition layer on the second gate insulating layer, the pixel definition layer having an opening, and the second active layer and the light-emitting layer being in the opening. 
     A shape of the second active layer may be a same shape as a shape of the light-emitting layer. 
     A region in which the second source electrode, the light-emitting layer, and the second drain electrode are overlapped with each other in the direction perpendicular to the surface of the substrate may be defined as an emission region. The emission region may be overlapped with the switching transistor in the direction perpendicular to the surface of the substrate. 
     A current direction of the second source electrode, the light-emitting layer, and the second drain electrode may be parallel to a channel length direction of the switching transistor. 
     An area of the first drain electrode may be equal to or greater than an area of the light-emitting layer. 
     The light-emitting layer may include an organic light-emitting material, a quantum dot, a perovskite, or a combination thereof. 
     An aperture ratio of the display panel may be greater than or equal to about 70%. 
     According to some example embodiments, a display panel may include a plurality of subpixels. Each subpixel of the plurality of subpixels may include a switching transistor, and a light-emitting transistor stacked with the switching transistor. A channel length direction of the light-emitting transistor may be parallel to a gate voltage application direction of the light-emitting transistor. 
     The switching transistor may be a gate of the light-emitting transistor. 
     A channel length direction of the switching transistor may be parallel to a gate voltage application direction of the switching transistor. 
     The switching transistor and the light-emitting transistor may be on a substrate. The switching transistor may include a first gate electrode, a first source electrode, a first active layer, and a first drain electrode, and the light-emitting transistor may include a second gate electrode, a second source electrode, a second active layer, a light-emitting layer, and a second drain electrode, the second gate electrode being the first drain electrode of the switching transistor. The first active layer may be overlapped with the second active layer in a direction perpendicular to a surface of the substrate. 
     The first gate electrode, the first source electrode, the first active layer, the first drain electrode, the second source electrode, the second active layer, the light-emitting layer, and the second drain electrode may be overlapped with each other in the direction perpendicular to the surface of the substrate. 
     A current direction of the second source electrode, the light-emitting layer, and the second drain electrode may be parallel to a channel length direction of the switching transistor. 
     A ratio of an area of the light-emitting layer of a subpixel of the plurality of subpixels to an area of the subpixel is greater than or equal to about 70%. 
     A display device may include the display panel. 
     The display device may include an organic light-emitting diode (OLED) display, a quantum dot light-emitting diode, or a perovskite light-emitting diode. 
     A display device may include the display panel. 
     The display device may include an organic light-emitting diode (OLED) display, a quantum dot light-emitting diode, or a perovskite light-emitting diode. 
     According to some example embodiments, a display panel may include a switching transistor and a light-emitting transistor. The switching transistor may include a first gate electrode, a first source electrode, a first active layer, and a first drain electrode. The light-emitting transistor may include a second gate electrode, a second source electrode, a second active layer, a light-emitting layer, and a second drain electrode, the second gate electrode being the first drain electrode of the switching transistor. The switching transistor, the second source electrode, the second active layer, the light-emitting layer, and the second drain electrode may be stacked in a direction perpendicular to a surface of the light-emitting layer. 
     The display panel may include a substrate, wherein the switching transistor and the light-emitting transistor are on the substrate such that the switching transistor is between the light-emitting transistor and the substrate. 
     A channel length direction of the light-emitting transistor may be parallel to a gate voltage application direction of the light-emitting transistor. 
     The first source electrode, the first active layer, and the first drain electrode may be stacked vertically with respect to the first gate electrode. 
     A channel length direction of the switching transistor may be parallel to a gate voltage application direction of the switching transistor. 
     The first active layer may be overlapped with the second active layer in the direction perpendicular to the surface of the light-emitting layer. 
     The display panel may further include a first gate insulating layer between the first gate electrode and the first source electrode, and a second gate insulating layer between the first drain electrode and the second source electrode. 
     The display panel may further include a pixel definition layer on the second gate insulating layer, the pixel definition layer having an opening. The second active layer and the light-emitting layer may be in the opening. 
     A display device may include the display panel. 
     An electronic device may include the display device. 
     The display quality may be improved by securing a high aperture ratio. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view illustrating an example of an arrangement of subpixels of a display panel according to some example embodiments, 
         FIG. 2  is a layout view illustrating an example of one subpixel of the display panel of  FIG. 1 , 
         FIG. 3  is a cross-sectional view of the subpixel of the display panel of  FIG. 2  taken along cross-sectional view line III-III′, 
         FIGS. 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, and 24  are layout views illustrating an example of a method of manufacturing the display panels of  FIGS. 1 to 3 , 
         FIGS. 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, and 25  are cross-sectional views illustrating an example of a method of manufacturing the display panels of  FIGS. 1 to 3 , 
         FIG. 26  is a cross-sectional view illustrating another example of one subpixel of a display panel according to some example embodiments, 
         FIG. 27  is a layout view illustrating another example of one subpixel of a display panel according to some example embodiments, 
         FIG. 28  is a cross-sectional view of the subpixel of the display panel of  FIG. 27  taken along cross-sectional view line XXVII-XXVII′, 
         FIG. 29A  is a schematic diagram of an electronic device according to some example embodiments, and 
         FIG. 29B  is a perspective view of the electronic device of  FIG. 29A  according to some example embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Example embodiments will hereinafter be described in detail, and may be easily performed by a person having an ordinary skill in the related art. However, this disclosure may be embodied in many different forms and is not to be construed as limited to the example embodiments set forth herein. 
     In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. 
     It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it may be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. 
     Hereinafter, “combination” includes a mixture and two or more stacked structures. 
     Hereinafter, a display panel according to some example embodiments is described with reference to the drawings. 
       FIG. 1  is a schematic view illustrating an example of an arrangement of subpixels of a display panel according to some example embodiments. 
     Referring to  FIG. 1 , the display panel  200  may include a plurality of subpixels (PX), and the plurality of subpixels (PX) may have a matrix array repeatedly arranged along rows and/or columns. The display panel  200  may include a unit subpixel group (A) that is repeatedly arranged, and the plurality of subpixels (PX) in the unit subpixel group (A) include 3×1, 2×2, 3×3, or 4×4 arrangements, but is not limited thereto. The arrangement of the subpixels (PX) may be, for example, a Bayer matrix, a PenTile matrix, and/or a diamond matrix, but is not limited thereto. Each subpixel (PX) may display red (R), green (G), blue (B), or white (W), and for example, the unit pixel group (A) may have an arrangement such as RGB, RGBG, RGBW, but is not limited thereto. Although all of the subpixels (PX) have the same size in the drawing, the present disclosure is not limited thereto, and one or more subpixels (PX) in the unit pixel group (A) may be larger or smaller than other subpixels (PX). Although all of the subpixels (PX) have the same shape in the drawing, the present disclosure is not limited thereto, and one or more subpixels (PX) in the unit pixel group (A) may have a different shape from other subpixels (PX). 
       FIG. 2  is a layout view illustrating an example of one subpixel of the display panel of  FIG. 1 , and  FIG. 3  is a cross-sectional view of the subpixel of the display panel of  FIG. 2  taken along cross-sectional view line III-III′. 
     Referring to  FIGS. 2 and 3 , the display panel  200  according to some example embodiments includes a substrate  110 , a plurality of signal lines  121 ,  171 , and  172 , a switching transistor  100 ST, and a light-emitting transistor  100 LET. As shown in  FIGS. 1-3 , the display panel  200  may include a plurality of subpixels (PX), where each subpixel (PX) includes a switching transistor  100 ST and a light-emitting transistor  100 LET stacked with (e.g., above or beneath) the switching transistor  100 ST. 
     The substrate  110  may be, for example, a glass substrate; an inorganic substrate such as a silicon wafer; or an organic substrate made of an organic material such as polycarbonate, polymethylmethacrylate, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyamide, polyamideimide, polyethersulfone, or a combination thereof. It will be understood that, in some example embodiments, the substrate  110  may be absent from the display panel  200 , such that the display panel  200  may include the plurality of subpixels (PX) having a switching transistor  100 ST and a light-emitting transistor  100 LET stacked therewith, and without any substrate  110 . 
     A plurality of signal lines  121 ,  171 , and  172  include gate lines  121  for transmitting a gate signal (or a scan signal), data lines  171  for transmitting a data signal, and driving voltage lines  172  for transmitting a driving voltage. The gate lines  121  may extend in a row direction, and the neighboring gate lines  121  may be disposed in parallel to each other. It will be understood that extending in the row direction may include extending substantially in the row direction, which includes extending in a direction that is in the row direction within manufacturing tolerances and/or material tolerances. The data lines  171  and the driving voltage lines  172  may extend in the column direction, and the neighboring data lines  171  and the neighboring driving voltage lines  172  may be arranged in parallel to each other. It will be understood that extending in the column direction may include extending substantially in the column direction, which includes extending in a direction that is in the column direction within manufacturing tolerances and/or material tolerances. As shown in at least  FIG. 2 , each subpixel (PX) may be a region defined by the gate lines  121 , the data lines  171 , and the driving voltage lines  172 , or may be disposed in the defined region. 
     The switching transistor  100 ST may be electrically connected to the gate lines  121  and the data lines  171 , and includes the first gate electrode  124 S, the first source electrode  173 S, the first active layer  154 S, and the first drain electrode  175 S. As shown in  FIG. 3 , the first source electrode  173 S, the first active layer  154 S, and the first drain electrode  175 S may be stacked vertically with respect to the first gate electrode  124 S. 
     The first gate electrode  124 S may be electrically connected to the gate lines  121  and may be, for example, a pattern protruding from the gate lines  121 . The first gate electrode  124 S may be formed with a relatively large area, and may occupy most of the area of the subpixel (PX). Accordingly, the display panel  200  may not include a separate storage capacitor. 
     The first gate electrode  124 S may be made of a low resistance conductor, for example a metal such as aluminum silver, gold, copper, magnesium, nickel, molybdenum or an alloy thereof; a conductive oxide such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc tin oxide (ZTO), aluminum tin oxide (AITO), and aluminum zinc oxide (AZO); a conductive organic material; and/or a carbon conductor such as graphene and carbon nanostructures. For example, the first gate electrode  124 S may be a transparent electrode or an opaque electrode. The transparent electrode may have a transmittance of greater than or equal to about 80% and may include a thin metal thin film or the aforementioned conductive oxide, conductive organic material, and/or carbon conductor. The opaque electrode may, for example, have a transmittance of less than about 10% or a reflectance of greater than or equal to about 5% and may include, for example, a metal. 
     When the terms “about” or “substantially” are used in this specification in connection with a numerical value, it is intended that the associated numerical value include a tolerance of ±10% around the stated numerical value. When ranges are specified, the range includes all values therebetween such as increments of 0.1%. 
     The first source electrode  173 S may be electrically connected to the data lines  171 . For example, the first source electrode  173 S may be in contact with the protruding portion  171   a  of the data lines  171 . The first source electrode  173 S may be formed with a relatively large area, and for example, may occupy most of the area of the subpixel (PX). For example, the first source electrode  173 S may be overlapped with the first gate electrode  124 S in a direction perpendicular to the surface  110 S of the substrate  110 . 
     The first source electrode  173 S may be made of a low resistance conductor, for example, the aforementioned metal, conductive oxide, conductive organic material, and/or carbon conductor. The first source electrode  173 S may be, for example, a transparent electrode or an opaque electrode. 
     For example, the first source electrode  173 S may have a porous structure, a grid structure, a mesh structure, or a continuous linear structure. Accordingly, as illustrated in  FIGS. 2 and 3 , a gate voltage applied to the first gate electrode  124 S may be effectively transferred to the first active layer  154 S through the first source electrode  173 S, in a structure in which the first source electrode  173 S is disposed between the first gate electrode  124 S and the first active layer  154 S. 
     The first drain electrode  175 S may face the first source electrode  173 S, and for example, the first source electrode  173 S and the first drain electrode  175 S may face each other along a direction perpendicular to the surface  110 S of the substrate  110 . The first drain electrode  175 S may be formed with a relatively large area, and may occupy most of the area of the subpixel (PX). For example, and as shown in  FIGS. 2-3 , an area of the first drain electrode  175 S (e.g., surface area of surface  175 Sa) may be equal to or larger (e.g., greater) than the area of the light-emitting layer  161  (e.g., surface area of surface  161   a ) which will be described later. The first drain electrode  175 S may be made of a low resistance conductor, for example, the aforementioned metal, conductive oxide, conductive organic material, and/or carbon conductor. The first drain electrode  175 S may be, for example, a transparent electrode or an opaque electrode. 
     The first active layer  154 S may be disposed between the first source electrode  173 S and the first drain electrode  175 S, and may be electrically connected to the first source electrode  173 S and the first drain electrode  175 S, respectively. The first active layer  154 S may be overlapped with the first gate electrode  124 S in a direction perpendicular to the surface  110 S of the substrate  110 . The first active layer  154 S may include, for example, an inorganic semiconductor such as amorphous silicon and/or crystalline silicon; an organic semiconductor such as a low molecular weight compound and/or a polymeric compound; or an oxide semiconductor, but is not limited thereto. For example, the first active layer  154 S may include an organic semiconductor, and for example, may include a polycyclic condensed aromatic compound. For example, the first active layer  154 S may include a deposited or soluble organic semiconductor. 
     For example, the first source electrode  173 S, the first active layer  154 S, and the first drain electrode  175 S are stacked in a direction perpendicular to the first gate electrode  124 S. Accordingly, the channel length direction of the switching transistor  100 ST from the first source electrode  173 S to the first drain electrode  175 S may be perpendicular to the surface  110 S of the substrate  110 . Such a vertical channel (e.g., the channel length direction) may be parallel to a gate voltage application direction from the first gate electrode  124 S to the first active layer  154 S (e.g., a gate voltage application direction of the switching transistor  100 ST). It will be understood that extending in parallel to a given direction may include extending substantially in parallel to the direction, which includes extending in a direction that is parallel to the given direction within manufacturing tolerances and/or material tolerances. Herein, since the channel length of the switching transistor  100 ST may correspond to a thickness of the first active layer  154 S, a short channel of less than or equal to about 5 μm, less than or equal to about 3 μm, less than or equal to about 2 μm, or less than or equal to about 1 μm may be implemented and thus current density of the switching transistor  100 ST may be effectively increased. 
     A first gate insulating layer  140   p  may be formed between the first gate electrode  124 S and the first source electrode  173 S. The first gate insulating layer  140   p  may include an organic, inorganic, or organic/inorganic insulating material, and may include, for example, an inorganic insulating material such as silicon oxide, silicon nitride, and silicon oxynitride; an organic insulating material such as polyimide; or organic/inorganic insulating materials such as polyorganosiloxane and polyorganosilazane. In some example embodiments, the first gate insulating layer  140   p  is absent from the display panel  200 . 
     The light-emitting transistor  100 LET may be a gate-controlled light-emitting diode and may be a combination of a driving transistor and a light-emitting diode. In some example embodiments, including the example embodiments shown in  FIGS. 2-3 , the switching transistor  100 ST may be a gate of the light-emitting transistor  100 LET. For example, the first drain electrode  175 S of the switching transistor  100 ST may be a second gate electrode of the light-emitting transistor  100 LET. Accordingly, when the switching transistor  100 ST is operated, a gate voltage may be applied to the light-emitting transistor  100 LET. 
     The second gate insulating layer  140   q  may be formed between the switching transistor  100 ST and the light-emitting transistor  100 LET. The second gate insulating layer  140   q  may include an organic, inorganic, or organic/inorganic insulating material, and may include, for example, an inorganic insulating material such as silicon oxide, silicon nitride, and silicon oxynitride; an organic insulating material such as polyimide; or organic/inorganic insulating materials such as polyorganosiloxane and polyorganosilazane. In some example embodiments, the second gate insulating layer  140   q  is absent from the display panel  200 . 
     The light-emitting transistor  100 LET is stacked with the switching transistor  100 ST with the second gate insulating layer  140   q  therebetween, and the light-emitting transistor  100 LET and the switching transistor  100 ST are overlapped with each other in a direction perpendicular to the surface  110 S of the substrate  110  within region R 1 . 
     As described above, the switching transistor  100 ST may be used as a gate (a second gate electrode) of the light-emitting transistor  100 LET. The light-emitting transistor  100 LET includes the second source electrode  173 D, the second active layer  154 D, the light-emitting layer  161 , the auxiliary layers  162  and  163 , and a second drain electrode  175 D. 
     The second source electrode  173 D is electrically connected to the driving voltage line  172 . For example, the second source electrode  173 D may be electrically connected to the driving voltage line  172  through a contact hole  148  in a second gate insulating layer  140   q.  For example, the second source electrode  173 D may be in contact with the protruding portion  172   a  of the driving voltage line  172 . The second source electrode  173 D may be formed with a relatively large area, for example, an area covering most of the area of the subpixel (PX) and the contact hole  148 . For example, the second source electrode  173 D may be overlapped with the switching transistor  100 S in a direction perpendicular to the surface  110 S of the substrate  110 . 
     The second source electrode  173 D may be made of a low resistance conductor, for example, the aforementioned metal, conductive oxide, conductive organic material, and/or carbon conductor. The second source electrode  173 D may be, for example, a transparent electrode or an opaque electrode. For example, the second source electrode  173 D may have a porous structure, a grid structure, a mesh structure, or a continuous linear structure. Accordingly, as shown in  FIGS. 2 and 3 , a gate voltage applied to the first drain electrode  175 S of the switching transistor  100 ST may be effectively transferred to the second active layer  154 D, in a structure in which the second source electrode  173 D is disposed between the switching transistor  100 ST and the second active layer  154 D. 
     The second drain electrode  175 D may face the second source electrode  173 D, and for example, the second source electrode  173 D and the second drain electrode  175 D may face each other in a direction perpendicular to the surface  110 S of the substrate  110 . The second drain electrode  175 D may be a common electrode, and for example, may be formed on a whole surface of the display panel  200 . The second drain electrode  175 D may be made of a low resistance conductor, and may be made of, for example, the aforementioned metal, conductive oxide, conductive organic material, and/or carbon conductor. The second drain electrode  175 D may be, for example, a transparent electrode or an opaque electrode. 
     The second active layer  154 D may be disposed between the second source electrode  173 D and the second drain electrode  175 D, and may be electrically connected to the second source electrode  173 D and the second drain electrode  175 D, respectively. The second active layer  154 D may be overlapped with the switching transistor  100 ST in a direction perpendicular to the surface  110 S of the substrate  110 . The second active layer  154 D and the first active layer  154 S may be overlapped with each other in a direction perpendicular to the surface  110 S of the substrate  110 , and may have the same planar shape. It will be understood that elements having the same shape may include elements having substantially the same shape, which includes having the same shape within manufacturing tolerances and/or material tolerances. The second active layer  154 D may include, for example, an inorganic semiconductor such as amorphous silicon and/or crystalline silicon; an organic semiconductor such as a low molecular weight compound and/or a polymeric compound; or an oxide semiconductor, but is not limited thereto. For example, the second active layer  154 D may include an organic semiconductor, and for example, may include a polycyclic condensed aromatic compound. For example, the second active layer  154 D may include a deposited or soluble organic semiconductor. 
     The light-emitting layer  161  may be disposed between the second source electrode  173 D and the second drain electrode  175 D, and electrically connected to the second source electrode  173 D and the second drain electrode  175 D, respectively. The light-emitting layer  161  may include a light-emitting organic material, a light-emitting inorganic material, a light-emitting organic/inorganic material, or a combination thereof. For example, the light-emitting layer  161  may include an organic light-emitting material, a quantum dot, a perovskite, or a combination thereof, but is not limited thereto. 
     The organic light-emitting material may include, for example, perylene or a derivative thereof, rubrene or a derivative thereof, 4-(dicyanomethylene)-2-methyl-6-[p-(dimethylamino)styryl]-4H-pyran or a derivative thereof, cumarin or a derivative thereof, carbazole or a derivative thereof, an organometallic compound including Pt, Os, Ti, Zr, Hf, Eu, Tb, Tm, Rh, Ru, Re, Be, Mg, Al, Ca, Mn, Co, Cu, Zn, Ga, Ge, Pd, Ag and/or Au, or a combination thereof, but is not limited thereto. 
     The quantum dot may include, for example, a Group II-VI semiconductor compound, a Group III-V semiconductor compound, a Group IV-VI semiconductor compound, a Group IV semiconductor element or compound, a Group semiconductor compound, a Group I-II-IV-VI semiconductor compound, a Group V semiconductor compound, or a combination thereof. The Group II-VI semiconductor compound may be for example a binary element of CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS, or a combination thereof; a ternary element of CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS, or a combination thereof; a quaternary element of ZnSeSTe, HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, or a combination thereof; or a combination thereof, but is not limited thereto. The Group III-V semiconductor compound may be for example a binary element of GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, or a combination thereof; a ternary element of GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, or a combination thereof; a quaternary element of GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, or a combination thereof; or a combination thereof, but is not limited thereto. The Group IV-VI semiconductor compound may be for example a binary element of SnS, SnSe, SnTe, PbS, PbSe, PbTe, or a combination thereof; a ternary element of SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, or a combination thereof; a quaternary element of SnPbSSe, SnPbSeTe, SnPbSTe, or a combination thereof; or a combination thereof, but is not limited thereto. The Group IV semiconductor element or compound may be for example a singular element semiconductor of Si, Ge, or a combination thereof; a binary element semiconductor of SiC, SiGe, or a combination thereof; or a combination thereof, but is not limited thereto. The Group semiconductor compound may be for example selected from CulnSe 2 , CulnS 2 , CulnGaSe, CuInGaS, or a combination thereof, but is not limited thereto. The Group I-II-IV-VI semiconductor compound may be for example CuZnSnSe, CuZnSnS, or a combination thereof, but is not limited thereto. The Group II-III-V semiconductor compound may include for example InZnP, but is not limited thereto. 
     The perovskite may include, for example, CH 3 NH 3 PbBr 3 , CH 3 NH 3 PbI 3 , CH 3 NH 3 SnBr 3 , CH 3 NH 3 SnI 3 , CH 3 NH 3 Sn 1−x Pb x Br 3 , CH 3 NH 3 Sn 1−x Pb x I 3 , HC(NH 2 ) 2 PbI 3 , HC(NH 2 ) 2 SnI 3 , (C 4 H 9 NH 3 ) 2 PbBr 4 , (C 6 H 5 CH 2 NH 3 ) 2 PbBr 4 , (C 6 H 5 CH 2 NH 3 ) 2 Pbl 4 , (C 6 H 5 C 2 H 4 NH 3 ) 2 PbBr 4 , (C 6 H 13 NH 3 ) 2 (CH 3 NH 3 ) n−1 Pb n I 3n+1 , or a combination thereof, but is not limited thereto. 
     The auxiliary layers  162  and  163  may be disposed on the lower and upper surfaces of the light-emitting layer  161 , respectively and may be a light-emitting auxiliary layer, a charge auxiliary layer, or a combination thereof. The auxiliary layers  162  and  163  may be, for example, at least one of a hole injection layer, a hole transport layer, an electron blocking layer, an electron injection layer, an electron transport layer, or a hole blocking layer. The auxiliary layers  162  and  163  may independently include an organic material, an inorganic material, or an organic/inorganic material. One or two of the auxiliary layers  162  and  163  may be omitted. 
     The auxiliary layers  162  and  163  may include, for example, poly(9,9-dioctyl-fluoren-2,7-diyl-co-(4,4′-(N-(4-butylphenyI)-diphenylamine)) (TFB), polyarylamine, poly(N-vinylcarbazole, polyaniline, polypyrrole, N,N,N′,N′-tetrakis(4-methoxyphenyl)-benzidine (TPD), (4,4′-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (α-NPD), m-MTDATA (4,4′,4″-tris[phenyl(m-tolyl)amino]triphenylamine), 4,4′,4″-tris(N-carbazolyl)-triphenylamine (TCTA), 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), poly(3,4-ethylenedioxythiophene) (PEDOT) or poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), p-type metal oxide (e.g., NiO, WO 3 , MoO 3 , etc.), a carbon-based material such as graphene oxide, or a combination thereof, but is not limited thereto. 
     The display panel  200  may further include a pixel definition layer  181 . The pixel definition layer  181  may be on (e.g., directly or indirectly) on the second gate insulating layer  140   q.  The pixel definition layer  181  may be formed on a whole surface of the display panel  200 , and may have an opening  182  (e.g., may include one or more inner surfaces  181 S that define one or more openings  182 ) corresponding to each subpixel (PX) and defining an emission region, also referred to herein as an area R 1  of the region where the second source electrode  173 D, the light-emitting layer  161 , and the second drain electrode  175 D are overlapped in the vertical direction (e.g., the direction perpendicular to the surface  110 S of the substrate  110  and/or the direction perpendicular to the surface  161   a  of the light-emitting layer  161 ). The opening  182  may be formed at a position overlapping at least a portion of the switching transistor  100 ST. In some example embodiments, the pixel definition layer  181  is omitted from the display panel  200 . The second active layer  154 D, the light-emitting layer  161 , and the auxiliary layers  162  and  163  may be disposed in the opening  182 , and shapes and sizes of the second active layer  154 D, the light-emitting layer  161 , and the auxiliary layers  162  and  163  may be determined according to the opening  182 . Accordingly, the shapes of the second active layer  154 D, the light-emitting layer  161 , and the auxiliary layers  162  and  163  may be the same, and the sizes of the second active layer  154 D, the light-emitting layer  161 , and the auxiliary layers  162  and  163  may be the same. It will be understood that elements having the same shape may include elements having substantially the same shape, which includes having the same shape within manufacturing tolerances and/or material tolerances. It will be understood that elements having the same size may include elements having substantially the same size, which includes having the same size within manufacturing tolerances and/or material tolerances. 
     The second source electrode  173 D, the light-emitting layer  161 , and the second drain electrode  175 D may provide a light-emitting diode, wherein one of the second source electrode  173 D or the second drain electrode  175 D is an anode and the other of the second source electrode  173 D and the second drain electrode  175 D is a cathode. For example, the second source electrode  173 D may be an anode and the second drain electrode  175 D may be a cathode. 
     A region R 1  where the second source electrode  173 D, the light-emitting layer  161 , and the second drain electrode  175 D are overlapped in the vertical direction (e.g., the direction perpendicular to the surface  110 S of the substrate  110  and/or the direction perpendicular to the surface  161   a  of the light-emitting layer  161 ) may be an emission region R 1 , and the emission region R 1  may be overlapped with at least a portion of the switching transistor  100 ST in the vertical direction. For example, the second source electrode  173 D, the second active layer  154 D, the light-emitting layer  161 , the light-emitting auxiliary layers  162  and  163 , and the second drain electrode  175 D may be overlapped in a direction perpendicular to the switching transistor  100 ST, for example, the first drain electrode  175 S of the switching transistor  100 ST. The switching transistor  100 ST, the second source electrode  173 D, the second active layer  154 D, the light-emitting layer  161 , and the second drain electrode  175 D may be stacked in a direction perpendicular to the surface  110 S of the substrate  110 . 
     Accordingly, the channel length direction  100 LET-CLD of the light-emitting transistor  100 LET from the second source electrode  173 D to the second drain electrode  175 D may be perpendicular to the surface  110 S of the substrate  110 . Such a vertical channel may be parallel to the gate voltage application direction  100 LET-VAD of the light-emitting transistor  100 LET, from the first drain electrode  175 S of the switching transistor  100 ST to the second active layer  154 D of the light-emitting transistor  100 LET. Accordingly, the channel length direction  100 LET-CLD of the light-emitting transistor  100 LET may be parallel to the gate voltage application direction of the light-emitting transistor  100 LET. Herein, since the channel length of the light-emitting transistor  100 LET may correspond to the thickness of the second active layer  154 D, a short channel length may be implemented to effectively increase current density of the light-emitting transistor  100 LET. 
     For example, the current directions  100 LET-CD of the light-emitting diodes of the second source electrode  173 D, the light-emitting layer  161 , and the second drain electrode  175 D may be parallel to the gate voltage application direction  100 ST-VAD applied from the switching transistor  100 ST. The gate voltage application direction  100 ST-VAD applied from the switching transistor  100 ST is parallel to the channel length direction  100 ST-CLD of the switching transistor  100 ST. As a result, the current directions  100 LET-CD of the light-emitting diodes of the second source electrode  173 D, the light-emitting layer  161 , and the second drain electrode  175 D (e.g., the current direction  100 LET-CD of the second source electrode  173 D, the light-emitting layer  161 , and the second drain electrode  175 D) may be parallel to the channel length direction  100 ST-CLD of the switching transistor  100 ST. 
     As described above, since the light-emitting transistor  100 LET is a gate-controlled light-emitting diode  100  including the switching transistor  100 ST as a gate, the light-emitting diode  100  may be operated when the switching transistor  100 ST is operated and a driving voltage is applied through the driving voltage line  172 . 
     Specifically, when a gate voltage is applied to the first gate electrode  124 S of the switching transistor  100 ST and a data voltage is applied to the data line  171 , a current flows from the first source electrode  173 S to the first drain electrode  175 S and a driving voltage is applied to the driving voltage line  172 , a current flows between the second source electrode  173 D and the second drain electrode  175 D using the first drain electrode  175 S as a gate to emit light from the light-emitting layer. 
     The display panel  200  may provide bottom emission to emit light toward the substrate  110 , top emission to emit light toward the opposite side of the substrate  110 , or dual emission to emit light both toward the substrate  110  and toward the opposite side of the substrate  110 . 
     For example, when the first gate electrode  124 S, the first source electrode  173 S, and the first drain electrode  175 S of the switching transistor  100 ST are transparent electrodes and the second drain electrode  175 D of the light-emitting transistor  100 LET is an opaque electrode, the display panel  200  may implement bottom emission. 
     For example, when at least one of the first gate electrode  124 S, the first source electrode  173 S, or the first drain electrode  175 S of the switching transistor  100 ST is an opaque electrode and the second drain electrode  175 D of the light-emitting transistor  100 LET is a transparent electrode, the display panel  200  may implement top emission. 
     For example, when the first gate electrode  124 S, the first source electrode  173 S, and the first drain electrode  175 S of the switching transistor  100 ST and the second drain electrode  175 D of the light-emitting transistor  100 LET are transparent electrodes, respectively, the display panel  200  may implement dual emission. 
     As such, the display panel  200  according to some example embodiments may have a structure in which the switching transistor  100 ST and the light-emitting transistor  100 LET are stacked in a vertical direction. For example, the first gate electrode  124 S, the first source electrode  173 S, the first active layer  154 S, the first drain electrode  175 S, the second source electrode  173 D, the second active layer  154 D, and the light-emitting layer  161 , and the second drain electrode  175 D may be overlapped with each other in a direction perpendicular to the surface  110 S of the substrate  110  within region R 1 , where region R 1  is defined as the emission region. As further shown, region R 1  may be a region in which the first gate electrode  124 S, the first source electrode  173 S, the first active layer  154 S, the first drain electrode  175 S, the second source electrode  173 D, the second active layer  154 D, and the light-emitting layer  161 , and the second drain electrode  175 D may be overlapped with each other in the direction perpendicular to the surface  110 S of the substrate  110 . It will be understood that the direction that is perpendicular to surface  110 S is also the direction that is perpendicular to the surface  161   a  of the light-emitting layer. 
     Accordingly, an area occupied by the transistors in the subpixel (PX) may be reduced, thereby effectively increasing a display area, that is, an aperture ratio and an effective aperture ratio. Here, the aperture ratio is a ratio of an area that may transmit light with respect to an area of the display panel  200 , and the effective aperture ratio is ratio of the area that may transmit light with respect to an area excluding the areas of the signal lines  121 ,  171 , and  172  of the display panel  200 . The area of the display panel  200  may be a sum of the areas of the plurality of subpixels (PX), and the area that may transmit light may be a sum of the areas of the light-emitting layers of each subpixel (PX). For example, the aperture ratio of the display panel  200  may be greater than or equal to about 70%, greater than or equal to about 72%, or greater than or equal to about 75%, and the effective aperture ratio of the display panel  200  may be greater than or equal to about 90%, greater than or equal to about 93%, greater than or equal to about 95%, or greater than or equal to about 97%. 
     With regard to a given subpixel (PX), for example as shown in  FIGS. 2-3 , the area of the subpixel (PX) that may transmit light may be the area R 1  of the emission region. In addition, the area of the subpixel (PX) excluding the areas of the signal lines  121 ,  171 , and  172  of the subpixel (PX) may be area P 1 , and the area of the subpixel (PX) may be area A 1 . The area of the light-emitting layer  161  may be L 1 , which may be the same as the area of the emission region R 1 . 
     The aperture ratio of the subpixel (PX) may be the ratio of area R 1  to area A 1 , and the effective aperture ratio of the subpixel (PX) may be the ratio of area R 1  to area P 1 . The aperture ratio of the subpixel (PX) (e.g., R 1 /A 1 ) may be greater than or equal to about 70%, greater than or equal to about 72%, or greater than or equal to about 75%, and the effective aperture ratio of the subpixel (PX) (e.g., R 1  /P 1 ) may be greater than or equal to about 90%, greater than or equal to about 93%, greater than or equal to about 95%, or greater than or equal to about 97%. 
     The aperture ratio of the subpixel (PX) may be the ratio of area Ll to area A 1 , and the effective aperture ratio of the subpixel (PX) may be the ratio of area Ll to area P 1 . The aperture ratio of the subpixel (PX) (e.g., L 1 /A 1 ) may be greater than or equal to about 70%, greater than or equal to about 72%, or greater than or equal to about 75%, and the effective aperture ratio of the subpixel (PX) (e.g., L 1 /P 1 ) may be greater than or equal to about 90%, greater than or equal to about 93%, greater than or equal to about 95%, or greater than or equal to about 97%. 
     By securing a high aperture ratio as described above, a reduction in luminance of the display panel  200  may be decreased and a high resolution may be realized, thereby improving display quality. 
     In addition, by reducing an area occupied by the transistor in the subpixel (PX), it is possible to realize bottom emission or dual emission, which is difficult to realize due to space limitation, thereby increasing a choice range of emission types. 
     In addition, by reducing an area occupied by the transistor in the subpixel (PX), constituent elements capable of performing additional functions while maintaining the same emission region may be additionally arranged in the display panel, as a form of an in-cell. The constituent elements that may be further disposed in the form of the in-cell may be, for example, a sensor such as a near infrared sensor, a visible light sensor, a fingerprint sensor, or a combination thereof, a driver or a circuit unit that performs additional functions, but is not limited thereto. Accordingly, a display panel having a complex or combination function may be realized without degrading display quality. 
     Hereinafter, an example of the manufacturing method of the display panel  200  described above is described with reference to  FIGS. 4 to 25  and  FIGS. 1 to 3 . 
       FIGS. 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, and 24  are layout views illustrating an example of a method of manufacturing the display panels of  FIGS. 1 to 3 .  FIGS. 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, and 25  are cross-sectional views illustrating an example of a method of manufacturing the display panels of  FIGS. 1 to 3 . 
     Referring to  FIGS. 4 and 5 , a conductive layer (not shown) is formed on the substrate  110  and is subjected to photolithography to form the gate line  121  and the first gate electrode  124 S. The first gate electrode  124 S may be a pattern protruding from the gate line  121 , and may occupy most of the area of the subpixel (PX). 
     Referring to  FIGS. 6 and 7 , the first gate insulating layer  140   p  is formed a whole surface  110 S of the substrate  110 . The first gate insulating layer  140   p  may be, for example, formed by depositing or coating an inorganic insulating material such as silicon oxide, silicon nitride, and silicon oxynitride; an organic insulating material such as polyimide; or organic/inorganic insulating materials such as polyorganosiloxane and polyorganosilazane. 
     Referring to  FIGS. 8 and 9 , a conductive layer (not shown) is formed on the first gate insulating layer  140   p  and is subjected to photolithography to form the data line  171  and the driving voltage line  172 . The data line  171  and the driving voltage line  172  may extend in a direction perpendicular to the gate line  121 . The data line  171  and the driving voltage line  172  may have protruding portions  171   a  and  172   a,  respectively. It will be understood that extending in a direction perpendicular to an element may include extending substantially in a direction perpendicular to an element, which includes extending in the direction perpendicular to the element within manufacturing tolerances and/or material tolerances. 
     Referring to  FIGS. 10 and 11 , the first source electrode  173 S is formed on the first gate insulating layer  140   p  and the data line  171 . The first source electrode  173 S may be provided by forming a conductive layer (not shown) followed by photolithography, or may be formed by coating nanostructure dispersion. The first source electrode  173 S may have, for example, a porous structure, a grid structure, a mesh structure, or a continuous linear structure. The first source electrode  173 S may be formed to be overlapped with the first gate electrode  124 S and may occupy most of the area of the subpixel (PX). A portion of the first source electrode  173 S is in contact with the protruding portion  171   a  of the data line  171 . 
     Referring to  FIGS. 12 and 13 , the first active layer  154 S is formed on the first source electrode  173 S. The first active layer  154 S may be, for example, formed by depositing or coating an inorganic semiconductor such as amorphous silicon and/or crystalline silicon; an organic semiconductor such as a low molecular weight compound and/or a polymeric compound; or an oxide semiconductor. The first active layer  154 S may be formed to be overlapped with the first source electrode  173 S, and may be formed to have the same shape as the first source electrode  173 S. 
     Referring to  FIGS. 14 and 15 , a conductive layer (not shown) is formed on the first active layer  154 S and is subjected to photolithography to form the first drain electrode  175 S. The first drain electrode  175 S may be overlapped with the first source electrode  173 S and the first active layer  154 S, respectively, and may occupy most of the area of the subpixel (PX). 
     Referring to  FIGS. 16 and 17 , the second gate insulating layer  140   q  is formed on the first drain electrode  175 S. The second gate insulating layer  140   q  may be, for example, formed by depositing or coating an organic, inorganic, or organic/inorganic insulating material, and may include, for example, an inorganic insulating material such as silicon oxide, silicon nitride, and silicon oxynitride; an organic insulating material such as polyimide; or organic/inorganic insulating materials such as polyorganosiloxane and polyorganosilazane. Subsequently, the second gate insulating layer  140   q  is subjected to photolithography to form a contact hole  148  that exposes the protruding portion  172   a  of the driving voltage line  172 . 
     Referring to  FIGS. 18 and 19 , a second source electrode  173 D is formed on the second gate insulating layer  140   q.  The second source electrode  173 D may be provided by forming a conductive layer (not shown) followed by photolithography, or may be formed by coating nanostructure dispersion. The second source electrode  173 D may have, for example, a porous structure, a grid structure, a mesh structure, or a continuous linear structure. The second source electrode  173 D may be formed to be overlapped with the first drain electrode  175 S and may occupy most of the area of the subpixel (PX). The second source electrode  173 D may contact the driving voltage line  172  through the contact hole  148  of the second gate insulating layer  140   q.    
     Referring to  FIGS. 20 and 21 , the insulating layer (not shown) is coated and patterned on the second gate insulating layer  140   q  and the second source electrode  173 D to form a pixel definition layer  181  having an opening  182 . The opening  182  may be formed at a region corresponding to the subpixel (PX) or at a position corresponding to the emission region. The opening  182  may be formed in a region in which the first gate electrode  124 S, the first source electrode  173 S, the first active layer  154 S, and the first drain electrode  175 S are stacked. 
     Referring to  FIGS. 22 and 23 , a second active layer  154 D is formed in the opening  182  of the pixel definition layer  181 . The second active layer  154 D may be, for example, formed by depositing or coating an inorganic semiconductor such as amorphous silicon and/or crystalline silicon; an organic semiconductor such as a low molecular weight compound and/or a polymeric compound; or an oxide semiconductor. 
     Referring to  FIGS. 24 and 25 , the light-emitting layer  161  and the auxiliary layers  162  and  163  are formed in the opening  182  of the pixel definition layer. The light-emitting layer  161  may be formed by depositing or coating a light-emitting material such as, for example, an organic light-emitting material, a quantum dot, a perovskite, or a combination thereof. The auxiliary layer  162  and  163  may be formed by depositing or coating a charge transport material. At least one of the auxiliary layers  162  or  163  may be omitted. 
     Referring to  FIGS. 2  and  FIG. 3 , a conductive layer (not shown) is formed on the pixel definition layer  181 , light-emitting layer  161 , and auxiliary layers  162  and  163  and is subjected to photolithography to form the second drain electrode  175 D. The second drain electrode  175 D may be formed on a whole surface of the display panel  200 . 
     Hereinafter, another example of the display panel  200  according to some example embodiments is described. 
       FIG. 26  is a cross-sectional view illustrating another example of one subpixel of a display panel according to some example embodiments. 
     The display panel  200  according to some example embodiments may include a substrate  110 ; a gate line  121 ; a data line  171 ; a driving voltage line  172 ; a switching transistor  100 ST including a first gate electrode  124 S, a first source electrode  173 S, a first active layer  154 S, and a first drain electrode  175 S; a first gate insulating layer  140   p ; a second gate insulating layer  140   q ; a pixel definition layer  181 ; a light-emitting transistor  100 LET including a second source electrode  173 D, a second active layer  154 D, a light-emitting layer  161 , auxiliary layers  162  and  163 , and a second drain electrode  175 D, wherein the switching transistor  100 ST and the light-emitting transistor  100 LET are overlapped with each other in a direction perpendicular to the surface  110 S of the substrate  110 . The detailed description is as described above. 
     However, the display panel  200  according to some example embodiments includes a switching transistor  100 ST having a co-planar structure, unlike the aforementioned example embodiments. That is, the first source electrode  173 S and the first drain electrode  175 S are arranged in parallel to the surface  110 S of the substrate  110 , and the first active layer  154 S is disposed between the first source electrode  173 S and the first drain electrode  175 S. Accordingly, the channel length direction of the switching transistor  100 ST from the first source electrode  173 S to the first drain electrode  175 S may be parallel to the surface  110 S of the substrate  110 , and may be perpendicular to the gate voltage application direction from the first gate electrode  124 S to the first active layer  154 S. 
     The display panel  200  may further include a capacitor electrode  177  electrically connected to the first drain electrode  175 S, and the capacitor electrode  177  may be used as a gate of the light-emitting transistor  100 LET. The second gate insulating layer  140   q  includes a second lower gate insulating layer  140   q - 1  disposed between the switching transistor  100 ST and the capacitor electrode  177 , and a second upper gate insulating layer  140   q - 2  disposed between the capacitor electrode  177  and the light-emitting transistor  100 LET. 
     Hereinafter, another example of the display panel  200  according to some example embodiments is described. 
       FIG. 27  is a layout view illustrating another example of one subpixel of a display panel according to some example embodiments, and  FIG. 28  is a cross-sectional view of the subpixel of the display panel of  FIG. 27  taken along cross-sectional view line XXVII-XXVII′. 
     Referring to  FIGS. 27 and 28 , the display panel  200  according to some example embodiments includes a substrate  110 ; a gate line  121 ; a data line  171 ; a driving voltage line  172 ; a switching transistor  100 ST including a first gate electrode  124 S, a first source electrode  173 S, a first active layer  154 S, and a first drain electrode  175 S; a first gate insulating layer  140   p ; a second gate insulating layer  140   q ; a pixel definition layer  181 ; a light-emitting transistor  100 LET including a second source electrode  173 D, a second active layer  154 D, a light-emitting layer  161 , auxiliary layers  162  and  163 , and a second drain electrode  175 D, like the aforementioned example embodiments, wherein the switching transistor  100 ST and the light-emitting transistor  100 LET are overlapped with each other in a direction perpendicular to the surface  110 S of the substrate  110 . The detailed description is as described above. 
     However, in the display panel  200  according to some example embodiments, unlike the aforementioned example embodiments, the driving voltage line  172  and the second source electrode  173 D directly contact each other without interposing the second gate insulating layer  140   q  and thus the contact hole  148  of the second gate insulating layer  140   q  may be omitted. Accordingly, the emission region may be further increased by an area of a connection portion between the driving voltage line  172  and the second source electrode  173 D through the contact hole  148  described in the aforementioned example embodiments, thereby further increasing the aperture ratio. 
     For example, the aperture ratio of the display panel  200  may be greater than or equal to about 75%, greater than or equal to about 80%, or greater than or equal to about 85%, and the effective aperture ratio of the display panel  200  may be greater than or equal to about 93%, greater than or equal to about 95%, greater than or equal to about 97%, or greater than or equal to about 99%. 
       FIG. 29A  is a schematic diagram of an electronic device  2900  according to some example embodiments.  FIG. 29B  is a perspective view of the electronic device  2900  of  FIG. 29A  according to some example embodiments. 
     An electronic device  2900  may include, but is not limited to a computing device, a tablet device, a mobile phone, a digital camera, an automobile part for incorporation into an automobile, any combination thereof, or the like. As shown in  FIG. 29A , an electronic device  2900  may include a processor  2920 , a memory  2930 , a power supply  2950 , and a display device  2940  that are electrically coupled together via a bus  2910 . The display device  2940  may include a display panel of any of the example embodiments as described herein (e.g., display panel  200 ). In some example embodiments, the display device  2940  includes an organic light-emitting diode (OLED) display, a quantum dot light-emitting diode, or a perovskite light-emitting diode. For example the display panel  200  of the display device  2940  may include an OLED display panel, a quantum dot light-emitting diode display panel, or a perovskite light-emitting diode display panel. The memory  2930 , which may be a non-transitory computer readable medium, may store a program of instructions. The processor  2920  may execute the stored program of instructions to perform one or more functions. For example, the processor  2920  may be configured to process electric signals generated by the display device  2940 . The processor  2920  may be configured to generate an output (e.g., an image to be displayed by the display panel  200  of the display device  2940 ) based on processing the electric signals. 
     While this disclosure has been described in connection with what is presently considered to be practical example embodiments, it is to be understood that the inventive concepts are not limited to the disclosed example embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.