Patent Publication Number: US-2015084009-A1

Title: Organic light-emitting display apparatus and method of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2013-0114133, filed on Sep. 25, 2013 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND 
     1. Field 
     Aspects of embodiments of the present invention are directed toward organic light-emitting display apparatuses and methods of manufacturing the same. 
     2. Description of the Related Art 
     An organic light-emitting display apparatus is a self-luminous display apparatus which includes a plurality of organic light-emitting devices each including a hole injection electrode, an electron injection electrode, and an organic emission layer provided therebetween. An exciton is generated when a hole, injected from the hole injection electrode, is recombined with an electron, injected from the electron injection electrode, in the organic emission layer. Light is then emitted when the exciton falls from an excited state to a ground state. 
     Because the organic light-emitting display apparatus is a self-luminous display apparatus, a separate light source is unnecessary. Therefore, the organic light-emitting display apparatus may be driven at a lower voltage and be manufactured to have a lighter weight and a slimmer profile. In addition, the organic light-emitting display apparatus has high-grade characteristics, such as wide viewing angles, high contrast, and fast response times. Hence, the organic light-emitting display apparatus has been widely applied to various fields, including personal portable devices such as MP3 players, mobile phones, televisions (TVs), or the like. 
     SUMMARY 
     Aspects of embodiments of the present invention are directed toward organic light-emitting display apparatuses and methods of manufacturing the same. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description or may be learned by practice of the presented embodiments. 
     According to one or more embodiments of the present invention, an organic light-emitting display apparatus includes: a pixel electrode on a substrate; an environmental element on the pixel electrode; a protection insulating layer between the pixel electrode and the environmental element and at a location corresponding to the environmental element; an opposing electrode facing the pixel electrode; and an intermediate layer between the pixel electrode and the opposing electrode and including an organic emission layer. 
     A width of the protection insulating layer may be substantially the same as that of the environmental element. 
     The protection insulating layer may be between the pixel electrode and the intermediate layer. 
     The protection insulating layer may include polyimide (PI), silicon oxide, and/or silicon nitride. 
     The protection insulating layer may have a thickness in a range from about 700 Å to about 1000 Å. 
     The opposing electrode and the intermediate layer may each include separated regions due to the environmental element. 
     The organic light-emitting display apparatus may further include: a thin film transistor electrically coupled to the pixel electrode and including an active layer, a gate electrode, a source electrode, a drain electrode, a first insulating layer between the active layer and the gate electrode, and a second insulating layer between the gate electrode and the source and drain electrodes; a pad electrode including a first pad layer on a same layer as the source and drain electrodes, and a second pad layer on the first pad layer; a third insulating layer covering the source and drain electrodes and both edges of the pad electrode and having an opening, the pixel electrode being in the opening; and a pixel defining layer having an opening at a location corresponding to the opening in the third insulating layer, the pixel defining layer covering both edges of the pixel electrode. 
     The organic light-emitting display apparatus may further include: a capacitor including a first electrode on a same layer as the active layer; a second electrode on a same layer as the gate electrode; and a third electrode on a same layer as the source and drain electrodes. 
     The pixel electrode may include a transparent conductive oxide layer and a semi-transmissive metal layer including silver (Ag) or a silver alloy, and the opposing electrode may include a reflective metal layer. 
     The second insulating layer may have an opening at a region corresponding to the opening included in the third insulating layer, wherein the opening in the second insulating layer, the opening in the third insulating layer, and the opening in the pixel defining layer overlap with each other, and wherein the opening in the third insulating layer is larger than the opening in the pixel defining layer and is smaller than the opening in the second insulating layer. 
     An end portion of the pixel electrode may be on a top surface of the third insulating layer. 
     The third insulating layer may have a contact hole to electrically couple the pixel electrode with the source electrode or the drain electrode, wherein a first contact layer is electrically coupled to the source electrode or the drain electrode, and a second contact layer is on the first contact layer and includes a same material as that of the second pad layer, the first and second contact layers being disposed at a lower portion of the contact hole, wherein a portion of the pixel electrode is at the contact hole, and wherein the pixel electrode and the second contact layer are directly connected to each other. 
     According to one or more embodiments of the present invention, a method of manufacturing an organic light-emitting display apparatus includes: forming a pixel electrode on a substrate; forming an insulating material on the pixel electrode; forming a protection insulating layer by removing the insulating material except for a region at which an environmental element is located; forming an intermediate layer on the pixel electrode and the environmental element; and forming an opposing electrode on the intermediate layer. 
     The method may further include: after the forming of the pixel electrode, forming a pixel defining layer having an opening exposing a portion of the pixel electrode, wherein the forming of the insulating material includes forming the insulating material on the pixel defining layer and on the portion of the pixel electrode exposed by the pixel defining layer. 
     The insulating material may be formed of polyimide (PI), silicon oxide, and/or silicon nitride. 
     The insulating material may have a thickness in a range of about 700 Å to about 1000 Å. 
     The insulating material may be formed by printing. 
     The intermediate layer and the opposing electrode may be formed by vapor deposition. 
     The protection insulating layer may be formed by removing the insulating material by plasma treatment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects of the present invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic cross-sectional view of an organic light-emitting display apparatus according to an embodiment of the present invention; 
         FIGS. 2 through 7  are schematic cross-sectional views sequentially explaining a method of manufacturing the organic light-emitting display apparatus shown in  FIG. 1 , according to an embodiment of the present invention; 
         FIG. 8  is a schematic cross-sectional view of an organic light-emitting apparatus according to another embodiment of the present invention; 
         FIG. 9  is a schematic cross-sectional view of an organic light-emitting apparatus according to another embodiment of the present invention; and 
         FIG. 10  is a schematic cross-sectional view of an organic light-emitting apparatus according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present description. 
     Example embodiments of the present invention will be described below in more detail with reference to the accompanying drawings. Throughout the disclosure, like reference numerals refer to like parts, and a redundant description thereof may be omitted. 
     It will be understood that although the terms “first”, “second”, etc. may be used herein to describe various components, these components should not be limited by these terms. These components are only used to distinguish one component from another. 
     As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     It will be further understood that the terms “comprises” and/or “comprising” used herein specify the presence of stated features or components, but do not preclude the presence or addition of one or more other features or components. 
     It will be understood that when a layer, region, or component is referred to as being “formed on” another layer, region, or component, it may be directly or indirectly formed on the other layer, region, or component. That is, for example, intervening layers, regions, or components may also be present. 
     Sizes of elements in the drawings may be exaggerated for convenience of explanation. In other words, because sizes and thicknesses of components in the drawings are arbitrarily illustrated for convenience of explanation, the following embodiments are not limited thereto. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. Further, the use of “may” when describing embodiments of the present invention relate to “one or more embodiments of the present invention.” 
       FIG. 1  is a schematic cross-sectional view of an organic light-emitting display apparatus  100  according to an embodiment of the present invention. 
     Referring to  FIG. 1 , the organic light-emitting display apparatus  100  of the present embodiment includes a pixel electrode  131  disposed on a substrate  110 , an environmental element  160  disposed on the pixel electrode  131 , a protection insulating layer  150  disposed between the pixel electrode  131  and the environmental element  160  and disposed at a region of the pixel electrode  131  corresponding to the environmental element  160 , an opposing electrode  133  disposed to face (e.g., directly face) the pixel electrode  131 , and an intermediate layer  132  disposed between the pixel electrode  131  and the opposing electrode  133  and including an organic emission layer. 
     An insulating layer  120  may be disposed between the substrate  110  and the pixel electrode  131 . 
     The pixel electrode  131  may be configured as a transparent or semitransparent electrode that transmits light emitted from the organic emission layer included in the intermediate layer  132  and may include a transparent conductive oxide, such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium oxide (e.g., In 2 O 3 ), indium gallium oxide (IGO), and/or aluminum zinc oxide (AZO). 
     The pixel electrode  131  may further include a semi-transmissive metal layer, in addition to the transparent conductive oxide. The semitransparent metal layer may be silver (Ag), magnesium (Mg), aluminum (Al), platinum (Pt), palladium (Pd), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium (Li), calcium (Ca), and/or ytterbium (Yb), and may be formed of a thin film that has a thickness in a range of about 100 Å to about 300 Å. 
     The pixel electrode  131  may have a structure in which the transparent electrode, the semi-transmissive metal layer, and the transparent electrode are stacked (e.g., sequentially stacked). 
     The environmental element  160  may be disposed on the pixel electrode  131  and may be an impurity particle provided (e.g., introduced) when the organic light-emitting display apparatus  100  is manufactured. For example, the environmental element  160  may be a microscopic particle introduced from an external environment (for example, dust, mote, etc.), a microscopic particle introduced from manufacturing equipment related to the organic light-emitting display apparatus  100 , a microscopic particle introduced from other layers (for example, the substrate  110 , the insulating layer  120 , etc.) included in the organic light-emitting display apparatus  100 , or the like. 
     The environmental element  160  may have various components (that is, the environmental element  160  have various compositions), such as various organic materials, inorganic materials, combinations of organic and inorganic materials, or the like. 
     Although the environmental element  160  shown in  FIG. 1  is a spherical particle for convenience of illustration, the shape of the environmental element  160  is not limited thereto. 
     The intermediate layer  132  includes the organic emission layer and may further include at least one of a hole injection layer (HIL), a hole transport layer (HTL), an electron transport layer (ETL), and an electron injection layer (EIL). However, the embodiment of the present invention is not limited thereto, and the intermediate layer  132  may include the organic emission layer and may further include various function (e.g., functional) layers. 
     The organic emission layer included in the intermediate layer  132  may include an organic material that emits a red color, a green color, or a blue color. However, the embodiment of the present invention is not limited thereto, and the organic emission layer may emit white light. In this case, the intermediate layer  132  may have a stacked structure of light-emitting material emitting red light, light-emitting material emitting green light, and light-emitting material emitting blue light, and may have a combined structure of the light-emitting material emitting red light, the light-emitting material emitting green light, and the light-emitting material emitting blue light. 
     The red color, the green color, and the blue color are provided as examples, and the present invention is not limited thereto. In other words, other, various suitable color combinations other than the combination of the red, green, and blue colors may be used as long as the combinations can emit white light. 
     The opposing electrode  133  may be configured as a reflective electrode and may include aluminum (Al), magnesium (Mg), lithium (Li), calcium (Ca), lithium fluoride/calcium (LiF/Ca), and/or lithium fluoride/aluminum (LiF/Al). 
     Therefore, the organic light-emitting display apparatus  100  according to the present embodiment may be a bottom emission display apparatus in which light emitted from the intermediate layer  132  is reflected by the opposing electrode  133 , transmits through the pixel electrode  131 , and is emitted in a direction of the substrate  110  (see the arrow in  FIG. 1 ). 
     When the pixel electrode  131  includes the semi-transmissive metal layer, the semi-transmissive metal layer and the opposing electrode  133  may form a microcavity structure, thereby increasing light efficiency and color purity of the organic light-emitting display apparatus  100 . 
     The organic light-emitting display apparatus  100  of the present embodiment includes the protection insulating layer  150  disposed between the pixel electrode  131  and the environmental element  160 . 
     That is, the protection insulating layer  150  may be disposed only at a region of the pixel electrode  131  at which the environmental element  160  is disposed. A width wa of the environmental element  160  and a width wb of the protection insulating layer  150  may be substantially same. 
     In this regard, the width wa of the environmental element  160  is a width of a largest cross-sectional region of the environmental element  160 . For example, when the environmental element  160  is spherical, a diameter of a sphere may be substantially similar to or the same as the width wa of the environmental element  160 . 
     The environmental element  160  may be a particle having an average particle diameter equal to or less than about 5 μm, for example, between about 1 μm and about 5 μm, but is not limited thereto. 
     When the environmental element  160  is provided on the pixel electrode  131 , the protection insulating layer  150  of the present embodiment may prevent the pixel electrode  131  and the opposing electrode  133  from being shorted (e.g., from contacting one another). 
     When there is no protection insulating layer  150  and when the environmental element  160  on the pixel electrode  131  is thicker than the intermediate layer  132 , the environmental element  160  is not sufficiently covered by the intermediate layer  132 , and a region in which the intermediate layer  132  and the opposing electrode  133  are separated (e.g., disconnected or cut) may be generated due to a step difference created by the environmental element  160 . 
     The opposing electrode  133  including aluminum (Al) may diffuse in the separated region (e.g., the cut region) toward the intermediate layer  132  and the pixel electrode  131 . Thus, the pixel electrode  131  and the opposing electrode  133  may short or contact one another, which causes a phenomenon in which a corresponding sub pixel does not emit light, i.e., a dark spot. 
     However, the organic light-emitting display apparatus  100  of the present embodiment includes the protection insulating layer  150  that may block a diffusion path of the opposing electrode  133  and prevent the pixel electrode  131  and the opposing electrode  133  from being shorted. Thus, the phenomenon of the dark spot due to the environmental element  160  may be prevented. 
     The protection insulating layer  150  may include an organic material, such as polyimide (PI), and/or an inorganic material, such as silicon oxide (e.g., SiO 2 ) or silicon nitride (e.g., Si 3 N 4 ). However, the present invention is not limited thereto, and the protection insulating layer  150  may include any suitable materials as long as they are insulating materials resistant to moisture. 
     The protection insulating layer  150  may have a thickness in a range of about 700 Å to about 1000 Å. When the protection insulating layer  150  is formed having a thickness less than 700 Å, the diffusion path of the opposing electrode  133  may not be sufficiently or completely blocked, and, when the protection insulating layer  150  is formed having a thickness greater than 1000 Å, the step difference may be greatly increased and removal of the protection insulation layer  150  by plasma treatment may not be easy. 
     A separated region (e.g., a cut region) may be included in the intermediate layer  132 , and the opposing electrode  133  of the organic light-emitting display apparatus  100  of the present embodiment due to step differences created by the protection insulting layer  150  and the environmental element  160 . That is, a separated region  132   a  (e.g., a separated portion) of the intermediate layer  132  and a separated region  133   a  (e.g., a separated portion) of the opposing electrode  133  may be disposed on the protection insulting layer  150  and the environmental element  160 . 
     Therefore, no voltage is applied to the region  133   a  of the opposing electrode  133  disposed on environmental element  160 , and thus, no light may emit from the region  132   a  of the intermediate layer  132  corresponding to the region  133   a  of the opposing electrode  133 . However, a region from which no light emits is a relatively very small region, and light emits from a region in which the environmental element  160  is not disposed, and thus a phenomenon in which entire corresponding sub pixels do not emit light is prevented. 
       FIGS. 2 through 7  are schematic cross-sectional views sequentially explaining a method of manufacturing the organic light-emitting display apparatus  100  shown in  FIG. 1  according to an embodiment of the present invention. 
     Referring to  FIG. 2 , the insulating layer  120  and the pixel electrode  131  are formed on the substrate  110 . The pixel electrode  131  may be formed by forming a pixel electrode material utilizing a deposition process or a sputtering process and patterning the pixel electrode material by utilizing a photolithography process. 
     The pixel electrode  131  may be configured as a transparent electrode or a semi-transparent electrode, may include a transparent conductive oxide, and may further include a semi-transmissive metal layer used to form a microcavity structure with the opposing electrode  133  shown in  FIG. 1 . 
     Referring to  FIG. 3 , a pixel defining layer  140  that includes an opening C5 exposing a part of the pixel electrode  131  and covers both ends of the pixel electrode  131  is formed on the pixel electrode  131 . 
     The pixel defining layer  140  functions to define a pixel region from which light is emitted and may be formed as an organic insulating layer. 
     Referring to  FIG. 4 , an insulating material  150 ′ used to form the protection insulating layer  150  of  FIG. 5  is coated on the pixel defining layer  140  and the pixel electrode  131  that is exposed by the opening C5 formed in the pixel defining layer  140 . The insulating material  150 ′ may be a material resistant to moisture, such as an organic material such as polyimide (PI) or an inorganic material such as silicon oxide or silicon nitride. 
     The insulating material  150 ′ may be formed by utilizing a printing process, but the present invention is not limited thereto. The insulating material  150 ′ may be formed by utilizing other, suitable methods. 
     The insulating material  150 ′ may have a thickness in a range of about 700 Å to about 1000 Å. 
     After the insulating material  150 ′ is formed, the substrate  110  on which the pixel electrode  131  and the insulating material  150 ′ are formed goes through processes including separation, chamfering, washing, curing, etc. 
     During any of the above processes, the environmental element  160  may be introduced or attached to the insulating material  150 ′. The environmental element  160  may not be removed by the washing process. 
     Referring to  FIG. 5 , the protection insulating layer  150  is formed by removing the insulating material  150 ′ except for a region at which the environmental element  160  is disposed. Thus, the width wa of the environmental element  160  and the width wb of the protection insulating layer  150  may be substantially the same, within a processing error or tolerance range. 
     The insulating material  150 ′ may be removed by a plasma treatment process. Plasma treatment is generally performed before the intermediate layer  132  shown in  FIG. 6  is formed, and thus no additional process is necessary for removing the protection insulating layer  150 ′ of the present embodiment, thereby simplifying a manufacturing process. 
     Referring to  FIG. 6 , the intermediate layer  132  is formed on the pixel electrode  131  and the environmental element  160 . 
     The intermediate layer  132  may be formed by utilizing a vapor deposition process. When a step difference between the region at which the environmental element  160  is disposed and a region at which the environmental element  160  is not disposed is great, due to, for example, a large size of the environmental element  160 , the intermediate layer  132  may include a separated region (e.g., a cut region). 
     That is, the separated region  132   a  of the intermediate layer  132  may be disposed on the environmental element  160 . 
     Referring to  FIG. 7 , the opposing electrode  133  is formed on the intermediate layer  132 . 
     The opposing electrode  133  may be formed by utilizing the vapor deposition process, and may include a separated region (e.g., a cut region) similar to the intermediate layer  132 . In this regard, the separated region  133   a  of the opposing electrode  133  may be formed to cover the separated region  132   a  of the intermediate layer  132 . 
     The organic light-emitting display apparatus  100  of the present embodiment includes the protection insulating layer  150  blocking a path (e.g., a short circuit path) from the pixel electrode  131  through the separated regions of the intermediate layer  132  and the opposing electrode  133  due to diffusion of a material included in the opposing electrode  133 , thereby preventing a phenomenon in which a dark spot is generated (that is, the protection insulating layer  150  prevents the opposing electrode  133  from contacting or shorting the pixel electrode  131 ). 
       FIG. 8  is a schematic cross-sectional view of an organic light-emitting apparatus  200  according to another embodiment of the present invention. 
     Referring to  FIG. 8 , the organic light-emitting apparatus  200  of the present embodiment includes a pixel electrode  231  disposed on a substrate  210 , environmental elements  261  and  262  disposed on the pixel electrode  231 , protection insulating layers  251  and  252  disposed between the pixel electrode  231  and the environmental elements  261  and  262  and respectively disposed at regions of the pixel electrode  231  corresponding to the environmental elements  261  and  262 , an opposing electrode  233  disposed to face the pixel electrode  231 , and an intermediate layer  232  disposed between the pixel electrode  231  and the opposing electrode  233  and including an organic emission layer. 
     An insulating layer  220  may be disposed between the substrate  210  and the pixel electrode  231 . 
     The environmental elements  261  and  262  may be disposed on or introduced to the pixel electrode  231 . The environmental elements  261  and  262  may have different sizes and include materials different from each other. 
     The protection insulating layers  251  and  252  may be disposed between the pixel electrode  231  and the environmental elements  261  and  262 , respectively. 
     The protection insulating layers  251  and  252  may have substantially the same widths as those of the environmental elements  261  and  262  that are respectively disposed on the protection insulating layers  251  and  252 . 
     The intermediate layer  232  and the opposing electrode  233  may include a separated region (e.g., a cut region). A separated region  232   a  (e.g., a separated portion) of the intermediate layer  232  and a separated region  233   a  (e.g., a separated portion) of the opposing electrode  233  may be disposed on the environmental element  262 . 
     When a size of the environmental element  261  is relatively small, the intermediate layer  232  and the opposing electrode  233  may not be separated or cut due to the environmental element  261 . In this case, light may be emitted from the intermediate layer  232  corresponding to a region at which the environmental element  261  is disposed. 
     The other elements are substantially the same as or substantially similar to those of the organic light-emitting apparatus  100  of  FIG. 1 , and thus descriptions thereof are omitted. 
       FIG. 9  is a schematic cross-sectional view of an organic light-emitting apparatus  300  according to another embodiment of the present invention. 
     Referring to  FIG. 9 , the organic light-emitting apparatus  300  of the present embodiment includes a pixel electrode  331  disposed on a substrate  310 , an environmental element  360  disposed on the pixel electrode  331 , a protection insulating layer  350  disposed between the pixel electrode  331  and the environmental element  360  and disposed at a region of the pixel electrode  331  corresponding to the environmental element  360 , an opposing electrode  333  disposed to face the pixel electrode  331 , and an intermediate layer  332  disposed between the pixel electrode  331  and the opposing electrode  333  and including an organic emission layer. 
     An insulating layer  320  may be disposed between the substrate  310  and the pixel electrode  331 . 
     The pixel electrode  331  may be configured as a reflective electrode that reflects light emitted from the organic emission layer included in the intermediate layer  332  and may include a reflective layer including Al, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr or compounds thereof. The pixel electrode  331  may also include a transparent or semi-transparent electrode layer formed on the reflective layer. 
     The transparent or semi-transparent electrode layer may include indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium oxide (e.g., In 2 O 3 ), indium gallium oxide (IGO), and/or aluminum zinc oxide (AZO). 
     The environmental element  360  may be disposed on or introduced to the pixel electrode  331 . The protection insulating layer  350  may be disposed between the environmental element  360  and the pixel electrode  331 . 
     The intermediate layer  332  includes the organic emission layer and may further include at least one of a hole injection layer (HIL), a hole transport layer (HTL), an electron transport layer (ETL), and an electron injection layer (EIL). The present embodiment of the present invention is not limited thereto, and the intermediate layer  332  may include the organic emission layer and may further include various function (e.g., functional) layers. 
     The opposing electrode  333  may be configured as a semi-transmissive electrode, may include Ag, Al, Mg, LI, Ca, Cu, LiF/Ca, LiF/Al, magnesium/silver (Mg/Ag), and/or calcium/silver (Ca/Ag), and may be formed as a thin film having a thickness in a range of several nm through several tens nm. 
     Therefore, the organic light-emitting apparatus  300  of the present embodiment may be a top emission display apparatus in which light emitted from the intermediate layer  332  is reflected by the pixel electrode  331  and is emitted in a direction of the opposing electrode  333  (see the arrow in  FIG. 9 ). 
     The other elements are substantially the same as or substantially similar to those of the organic light-emitting apparatus  100  shown in  FIG. 1 , and thus descriptions thereof are omitted. 
       FIG. 10  is a schematic cross-sectional view of an organic light-emitting apparatus  400  according to another embodiment of the present invention. 
     Referring to  FIG. 10 , the organic light-emitting apparatus  400  of the present embodiment includes a pixel region PXL including an intermediate layer  432  disposed on a substrate  410 , a transistor region TR including at least one thin film transistor, a capacitor region CAP including at least one capacitor, and a pad region PAD. 
     The substrate  410  may be a glass substrate or a plastic substrate. A buffer layer  421  may be disposed on the substrate  410 . 
     An active layer  212  of the thin film transistor is disposed at the transistor region TR and provided on the buffer layer  421 . The active layer  212  may be formed to include various materials. For example, the active layer  212  may include an inorganic semiconductor material, such as amorphous silicon or crystalline silicon. In this case, the active layer  212  may include a channel region  212   c,a  source region  212   a , and a drain region  212   b . The source region  212   a  and the drain region  212   b  are disposed at both edges of the channel region  212   c  and are doped with ion impurities. As another example, the active layer  212  may include an oxide semiconductor. As another example, the active layer  212  may include an organic semiconductor material. 
     A gate electrode  215  is disposed on a first insulating layer  423  at a location corresponding to the channel region  212   c  of the active layer  212 . The first insulating layer  423  is a gate insulating film disposed between the gate electrode  215  and the active layer  212 . The gate electrode  215  may have a single layer structure or a multilayer structure including aluminum (Al), platinum (Pt), palladium (Pd), silver (Ag), magnesium (Mg), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium (Li), calcium (Ca), molybdenum (Mo), titanium (Ti), tungsten (W), and/or copper(Cu). 
     A source electrode  217   a  and a drain electrode  217   b  that are respectively connected to the source region  212   a  and the drain region  212   b  of the active layer  212  are disposed on a second insulating layer  426 . The second insulating layer  426  is an interlayer insulating film disposed between the gate electrode  215  and the source and drain electrodes  217   a  and  217   b . Each of the source electrode  217   a  and the drain electrode  217   b  may have a structure of two or more heterogeneous metal layers having electron mobilities different from each other. For example, each of the source electrode  217   a  and the drain electrode  217   b  may have a structure of two or more layers including a metal, such as Al, Pt, Pd, Ag, Mg, Au, Ni, Nd, Ir, Cr, Li, Ca, Mo, Ti, W, Cu, and/or alloys of these metal materials. 
     A third insulating layer  429  is provided on the second insulating layer  426  to cover the source electrode  217   a  and the drain electrode  217   b.    
     The first insulating layer  423  and the second insulating layer  426  may be configured as single-layer or multilayer inorganic insulating layers. The third insulating layer  429  may be configured as an organic insulating layer. 
     A pixel defining layer  440  is disposed on the third insulating layer  429 . The pixel defining layer  440  may be configured as an organic insulating layer. 
     The buffer layer  421  and the first insulating layer  423  are disposed on the substrate  410  in the pixel region PXL. A pixel electrode  431  is disposed on the first insulating layer  423  at the pixel region PXL. 
     The pixel electrode  431  is disposed in an opening C2 formed in the third insulating layer  429 . The pixel defining layer  440  including an opening C5, formed in a location corresponding to the opening C2 included in the third insulating layer  429 , is disposed at both edges of the pixel electrode  431 . 
     The second insulating layer  426  includes an opening C1 formed at a location corresponding to the opening C2 included in the third insulating layer  429 . The opening C1 included in the second insulating layer  426 , the opening C2 included in the third insulating layer  429 , and the opening C5 included in the pixel defining layer  440  are formed to overlap with each other. The opening C2 included in the third insulating layer  429  may be larger than the opening C5 included in the pixel defining layer  440  and may be smaller than the opening C1 included in the second insulating layer  426 . 
     An end portion of the pixel electrode  431  is disposed on a top surface of the third insulating layer  429  and is covered by the pixel defining layer  440 . A part of the pixel electrode  431  is exposed by the pixel defining layer  440 . 
     The third insulating layer  429  may include a contact hole C3 that electrically couples (e.g., electrically connects) the pixel electrode  431  to the source electrode  217   a  or the drain electrode  217   b . A case where the pixel electrode  431  is electrically coupled to (e.g., electrically connected to) the drain electrode  217   b  is illustrated in the embodiment shown in  FIG. 10 . 
     That is, a first contact layer  417  extending from the drain electrode  217   b  and a second contact layer  418  provided on the first contact layer  417  are disposed at a lower portion of the contact hole C3. The pixel electrode  431  disposed in the contact hole C3 is directly connected to (e.g., contacts) the second contact layer  418  and is electrically coupled to (e.g., electrically connected to) the drain electrode  217   b.    
     The pixel electrode  431  may include a semi-transmissive metal layer  431   b . The pixel electrode  431  may further include transparent conductive oxide layers  431   a  and  431   c  that are respectively formed at lower and upper portions of the semi-transmissive metal layer  431   b  and protect the semi-transmissive metal layer  431   b.    
     The semi-transmissive metal layer  431   b  may be formed of silver (Ag) or a silver alloy. The semi-transmissive metal layer  431   b  forms a microcavity structure with an opposing electrode  433  (e.g., a reflective electrode) that will be further described later, thereby increasing light efficiency and color purity of the organic light-emitting display apparatus  400 . 
     An environmental element  460  may be disposed on the pixel electrode  431  exposed by the opening C5 included in the pixel defining layer  440 . The environmental element  460  may have various components (i.e., may include various materials), such as various organic materials, inorganic materials, combinations of organic and inorganic materials, or the like 
     The organic light-emitting display apparatus  400  of the present embodiment includes a protection insulating layer  450  disposed between the pixel electrode  431  and the environmental element  460 . 
     That is, the protection insulating layer  450  may be disposed only at a region of the pixel electrode  431  on which the environmental element  460  is disposed. A width of the environmental element  460  and a width of the protection insulating layer  450  may be substantially the same. 
     When the environmental element  460  is provided on the pixel electrode  431 , the protection insulating layer  450  of the present embodiment may prevent the pixel electrode  431  and the opposing electrode  433  from being shorted (that is, may prevent the pixel electrode  431  and the opposing electrode  433  from contacting each other). 
     When the protection insulating layer  450  is not present or formed and when the environmental element  460  that is thicker than the intermediate layer  432  is provided, the environmental element  460  is not sufficiently covered by the intermediate layer  432 , and a region in which the intermediate layer  432  and the opposing electrode  433  are separated (e.g., cut) may be generated. 
     The opposing electrode  433 , including aluminum (Al), may diffuse into the separated region (e.g., the cut region) toward the intermediate layer  432  and the pixel electrode  431 . Thus, the pixel electrode  431  and the opposing electrode  433  may be shorted (that is, the pixel electrode  431  and the opposing electrode  433  may contact each other), which causes a phenomenon in which a corresponding sub pixel does not emit light, i.e., a dark spot. 
     However, the organic light-emitting display apparatus  400  of the present embodiment includes the protection insulating layer  450  that may block a diffusion path of the opposing electrode  433  and prevents the pixel electrode  431  and the opposing electrode  433  from being shorted with each other. Thus, the phenomenon of the dark spot due to the environmental element  460  may be prevented. 
     The intermediate layer  432  may be disposed on the pixel electrode  431  and the environmental element  460 . The intermediate layer  432  includes an organic emission layer and may further include at least one of a HIL, a HTL, an ETL, and an EIL. The embodiment of the present invention is not limited thereto, and the intermediate layer  432  may include the organic emission layer and further various function (e.g., functional) layers. 
     Although the intermediate layer  432  is disposed only at a bottom of the opening C5 included in the pixel defining layer  440  shown in  FIG. 10 , this is for convenience of illustration and the present invention is not limited thereto. That is, the organic emission layer included in the intermediate layer  432  may be extended and formed at a top surface of the pixel defining layer  440  along an etch surface of the opening C5 included in the pixel defining layer  440  as well as at the bottom of the opening C5. Function layers included in the intermediate layer  432  may be extended to other pixels. 
     The opposing electrode  433  may be disposed on the intermediate layer  432 . 
     The opposing electrode  433  may be configured as a reflective electrode including a reflective material, and may include Al, Mg, Li, Ca, LiF/Ca, and/or LiF/Al. 
     Therefore, the organic light-emitting display apparatus  400  of the present embodiment may be a bottom emission display apparatus in which light emitted from the intermediate layer  432  is reflected by the opposing electrode  433 , transmits through the pixel electrode  431 , and is emitted in a direction of the substrate  410 . 
     The intermediate layer  432  and the opposing electrode  433  may each include a separated region (e.g., a cut region) due to step differences created by the protection insulting layer  450  and the environmental element  460 . That is, a separated region  432   a  (e.g., a separated portion) of the intermediate layer  432  and a separated region  433   a  (e.g., a separated portion) of the opposing electrode  433  may be disposed on the protection insulting layer  450  and the environmental element  460 . 
     Therefore, no voltage is applied to the region  433   a  of the opposing electrode  433  disposed on the environmental element  460 , and thus no light may emit from the region  432   a  of the intermediate layer  432  corresponding to the region  433   a  of the opposing electrode  433 . However, a region from which no light emits is a relatively very small region, and light emits from a region in which the environmental element  460  is not disposed, and thus a phenomenon in which entire corresponding sub pixels do not emit light is prevented. 
     The buffer layer  421  is disposed on the substrate  410  in the capacitor region CAP. A capacitor including a first electrode  312  disposed on the same layer as the active layer  212 , a second electrode  314  disposed on the same layer as the gate electrode  215 , and a third electrode  317  disposed on the same layer as the source electrode  217   a  and the drain electrode  217   b  is provided on the buffer layer  421  in the capacitor region CAP. 
     The first electrode  312  of the capacitor may be formed as a semiconductor doped with ion impurities, similar to (or like) the source area  212   a  and the drain area  212   b  of the active layer  212 . 
     The second electrode  314  of the capacitor is disposed on the first insulating layer  423  in the same layer as the gate electrode  215 , whereas materials of the second electrode  314  and the gate electrode  215  are different from each other. The material of the second electrode  314  may include the transparent conductive oxide. Ion impurities are doped on the first electrode  312  through the second electrode  314 , thereby forming the capacitor having a metal-insulator-metal (MIM) structure. 
     The third electrode  317  of the capacitor may be formed of the same material as those of the source electrode  217   a  and the drain electrode  217   b . A plurality of capacitors that are connected in parallel to each other are formed by using the first electrode  312 , the second electrode  314 , and the third electrode  317 , thereby increasing a capacitance of the organic light-emitting display apparatus  400  without increasing an area of the capacitor. Thus, the area of the capacitor may be reduced as the capacitance increases, thereby increasing an aperture ratio. 
     A first pad layer  517  and a second pad layer  518  are disposed on the second insulating layer  426  in the pad region PAD. 
     The first pad layer  517  may include a plurality of metal layers having electron mobilities different from each other like the source electrode  217   a  and drain electrode  217   b . For example, the first pad layer  517  may have a multilayer structure including one or more metal materials, such as aluminum (AI), platinum (Pt), palladium (Pd), silver (Ag), magnesium (Mg), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium (Li), calcium (Ca), molybdenum (Mo), titanium (Ti), tungsten (W), and/or copper(Cu). 
     The second pad layer  518  may be formed of a transparent conductive oxide and may prevent the first pad layer  517  from being exposed to moisture and oxygen, thereby preventing a deterioration of reliability of a pad. The second pad layer  518  may be formed of the same material and on the same layer as that of the second contact layer  418  disposed at the lower portion of the contact hole C3. 
     The first pad layer  517  is not exposed to an etchant during a process of etching the pixel electrode  431  because the second pad layer  518  that is a protection layer is formed on an upper portion of the first pad layer  517 . 
     Moreover, end portions of the first pad layer  517  that are sensitive to an external environment including, for example, moisture or oxygen, are covered by the third insulating layer  429 , and thus, the end portions of the first pad layer  517  are not also exposed to the etchant during the process of etching the pixel electrode  431 . 
     Meanwhile, the organic light-emitting display apparatus  400  according to the present embodiment may further include a sealing member that seals (e.g., that is configured to seal) a display region including the pixel region PXL, the transistor region TR, and the capacitor region CAP. The sealing member may be formed as a substrate including, for example, a glass member, a plastic member, a metal film, or a thin film encapsulation formed by alternately disposing an organic insulating film and an inorganic insulating film. 
     As described above, aspects of the one or more of the above embodiments of the present invention provide the organic light-emitting display apparatus and method of manufacturing the same that may reduce or prevent dark spot generation. 
     It should be understood that the example embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. 
     While one or more embodiments of the present invention have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims and their equivalents.