Abstract:
An organic light-emitting display is disclosed. In one embodiment, the display includes i) a substrate, ii) a thin film transistor formed on the substrate, and comprising i) a gate electrode, ii) an active layer electrically insulated from the gate electrode, and iii) source and drain electrodes that are electrically connected to the active layer and iii) a first electrode electrically connected to the thin film transistor. The display further includes an intermediate layer formed on the first electrode and comprising an organic emission layer and a second electrode formed on the intermediate layer, wherein the source electrode or the drain electrode has an optical blocking portion extending in the direction of substrate thickness.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2010-0053025, filed on Jun. 4, 2010, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND 
     1. Field 
     The described technology generally relates to an organic light-emitting display. 
     2. Description of the Related Technology 
     Today, cathode ray tube (CRT) displays have been largely replaced by flat displays having a thin profile. From among various types of flat display technologies, an organic light-emitting diode (OLED) display is self emissive, and has desirable characteristics such as a large viewing angle, good contrast characteristics, fast response speeds, enhanced brightness and low power consumption. Thus, such a display has drawn widespread attention as the next-generation commercial display. 
     An organic light-emitting display includes a cathode electrode and an anode electrode with an organic emission layer therebetween. If a voltage is applied to the cathode electrode and the anode electrode, visible light is generated from the organic emission layer. 
     An active matrix (AM) organic light-emitting display includes driving and switching thin film transistors (TFTs) to provide electrical signals to each OLED. TFTs generally degrade when exposed to light. Generally, the performance of an organic light-emitting display depends on the optical reliability of its TFTs. 
     The performance of the active semiconductor layer included in the thin film transistor degrades with exposure to visible light generated from the organic emission layer. Accordingly, the electrical characteristics of the thin film transistor are changed, thereby diminishing the image quality of the OLED display. 
     SUMMARY 
     One inventive aspect is an organic light-emitting display in which image quality can be easily improved. 
     Another aspect is an organic light-emitting display including a substrate; a thin film transistor that is disposed on the substrate and includes a gate electrode, an active layer insulated from the gate electrode, and a source electrode and drain electrode that are electrically connected to the active layer; a first electrode that is electrically connected to the thin film transistor; an intermediate layer formed on the first electrode and including an organic emission layer; and a second electrode formed on the intermediate layer, wherein the source electrode or the drain electrode includes an optical blocking unit extending in a thickness direction of the substrate. 
     The source electrode or the drain electrode may be connected to the first electrode, and the source electrode or drain electrode that is connected to the first electrode may include the optical blocking unit. 
     The active layer may include an oxide semiconductor material. 
     The gate electrode may be formed on the substrate, the active layer may be formed over the gate electrode, and the optical blocking unit may include a region that overlaps the gate electrode in a direction perpendicular to the thickness direction of the substrate. 
     The optical blocking unit may contact the substrate. 
     The organic light-emitting display may further include a buffer layer between the substrate and the thin film transistor, and the optical blocking unit may contact the buffer layer. 
     A passivation layer that includes a via-may be hole disposed between the thin film transistor and the first electrode, a via-hole. The source electrode or the drain electrode may be connected to the first electrode via the via-hole. The optical blocking unit may include a region that overlaps the via-hole in the thickness direction of the substrate. 
     The gate electrode may be formed on the substrate. The active layer may be formed on the gate electrode. The organic light-emitting display may further include a conductive unit formed on the substrate to be disposed apart from the gate electrode. The optical blocking unit and the conductive unit may be connected to each other. 
     The conductive unit may include the same material as the gate electrode. 
     The organic light-emitting display may further include a passivation layer disposed between the thin film transistor and the first electrode, the passivation layer including a via-hole. The source electrode or the drain electrode may be connected to the first electrode via the via-hole. The optical blocking unit may include a region that overlaps the via-hole in the thickness direction of the substrate. 
     The gate electrode and the first electrode may be formed on the substrate to be disposed apart from each other. The active layer may be formed on the gate electrode. The optical blocking unit may include a region that overlaps the gate electrode in a direction perpendicular to the thickness direction of the substrate. 
     The optical blocking unit may contact a side surface of the first electrode. 
     The optical blocking unit may contact a side surface of the first electrode facing the gate electrode. 
     The optical blocking unit may cover a region of a side surface of the first electrode, which contacts the substrate. 
     The organic light-emitting display may further include a buffer layer disposed between the substrate and the first electrode. The optical blocking unit may cover a region of a side surface of the first electrode that contacts the buffer layer. 
     Another aspect is an organic light-emitting display comprising: a substrate; a thin film transistor formed on the substrate, and comprising i) a gate electrode, ii) an active layer electrically insulated from the gate electrode, and iii) source and drain electrodes that are electrically connected to the active layer; a first electrode electrically connected to the thin film transistor; an intermediate layer formed on the first electrode and comprising an organic emission layer; and a second electrode formed on the intermediate layer, wherein the source electrode or the drain electrode has an optical blocking portion extending in the direction of substrate thickness. 
     In the above display, the source electrode or the drain electrode is electrically connected to the first electrode, and wherein the electrode that is connected to the first electrode comprises the optical blocking portion. In the above display, the active layer is formed at least partially of an oxide semiconductor material. In the above display, the gate electrode is formed on the substrate, wherein the active layer is formed over the gate electrode, and wherein the optical blocking portion includes a region that overlaps with at least part of the gate electrode in a direction substantially perpendicular to the substrate thickness. 
     In the above display, the optical blocking portion contacts the substrate. The above display further comprises a buffer layer formed between the substrate and the thin film transistor, wherein the optical blocking portion contacts the buffer layer. The above display further comprises a passivation layer disposed between the thin film transistor and the first electrode, the passivation layer including a via-hole, wherein the source electrode or the drain electrode is connected to the first electrode by way of the via-hole, and wherein the optical blocking portion includes a region that overlaps with at least part of the via-hole in the thickness direction of the substrate. 
     In the above display, the gate electrode is formed on the substrate, wherein the active layer is formed on the gate electrode, wherein the organic light-emitting display further comprising a conductive unit formed on the substrate to be disposed apart from the gate electrode, and wherein the optical blocking portion and the conductive unit are connected to each other. In the above display, the conductive unit and the gate electrode are formed of the same material. 
     The above display further comprises a passivation layer disposed between the thin film transistor and the first electrode, the passivation layer including a via-hole, wherein the source electrode or the drain electrode is electrically connected to the first electrode via the via-hole, and wherein the optical blocking portion includes a region that overlaps with at least part of the via-hole in the thickness direction of the substrate. 
     In the above display, the gate electrode and the first electrode are formed on the substrate to be disposed apart from each other, wherein the active layer is formed on the gate electrode, and wherein the optical blocking portion includes a region that overlaps with at least part of the gate electrode in a direction substantially perpendicular to the thickness direction of the substrate. In the above display, the optical blocking portion contacts a side surface of the first electrode. In the above display, the optical blocking portion contacts a side surface of the first electrode facing the gate electrode. 
     In the above display, the optical blocking portion at least partially covers a side surface of the first electrode, which contacts the substrate. The above display further comprises a buffer layer disposed between the substrate and the first electrode, wherein the optical blocking portion at least partially covers a side surface of the first electrode that contacts the buffer layer. 
     Another aspect is an organic light-emitting display comprising: a thin film transistor (TFT) formed on a substrate, wherein the TFT comprises i) a gate electrode, ii) an active layer electrically insulated from the gate electrode, and iii) source and drain electrodes electrically connected to the active layer; a first electrode electrically connected to the TFT; an organic light emission layer formed on the first electrode and configured to emit light; and a second electrode formed on the organic light emission layer, wherein a portion of at least one of the source electrode and the drain electrode extends in the direction of substrate thickness and is configured to substantially block the emitted light from entering the active layer of the TFT. 
     In the above display, only one of the source and drain electrodes includes the portion, and wherein the electrode having the portion is formed to be closer to the organic light emitting layer than the other electrode. The above display further comprises a gate insulating layer formed between the gate electrode and active layer, wherein the portion at least partially penetrates the gate insulating layer. In the above display, the portion substantially completely penetrates the gate insulating layer. In the above display, the portion contacts the substrate or a conductive unit formed between the portion and substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of an organic light-emitting display according to an embodiment. 
         FIG. 2  is a schematic cross-sectional view of an organic light-emitting display according to another embodiment. 
         FIG. 3  is a schematic cross-sectional view of an organic light-emitting display according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, certain embodiments will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a schematic cross-sectional view of an organic light-emitting display  100  according to an embodiment. Referring to  FIG. 1 , the display  100  includes a substrate  101 , a thin film transistor (TFT), a first electrode  114 , an intermediate layer  116 , a second electrode  117 , and an optical blocking unit (or optical blocking portion)  111 . The TFT includes a gate electrode  103 , an active layer  107 , a source electrode  109 , and a drain electrode  110 . The source electrode  109  or the drain electrode  110  includes the optical blocking unit  111 . 
     The substrate  101  may be formed of a glass material, the main ingredient of which is SiO 2  but is not limited thereto and may be formed of any transparent plastic material. The transparent plastic material may be an insulating organic material selected from the group consisting of polyethersulphone (PES), polyacrylate (PAR), polyetherimide (PEI), polyethyelenen napthalate (PEN), polyethyeleneterepthalate (PET), polyphenylene sulfide (PPS), polyallylate, polyimide, polycarbonate (PC), cellulose triacetate (TAC), and cellulose acetate propionate (CAP). 
     Although not shown, a buffer layer may be formed on the substrate  101  to provide a planar surface on the substrate  101  and to prevent moisture or foreign substances from permeating into the substrate  101 . This applies to the embodiments of  FIGS. 1 and 2 . 
     The gate electrode  103  is formed on the substrate  101 . The gate electrode  103  may be formed of at least one material selected from the group consisting of Au, Ag, Cu, Ni, Pt, Pd, Al, Mo, an Al:Nd alloy, and a Mo:W alloy but is not limited thereto and may include various conductive materials. 
     A first capacitor electrode  104  is formed on the substrate  101 . The first capacitor electrode  104  may be formed of the same material as the gate electrode  103 . In one embodiment, the first capacitor electrode  104  is simultaneously formed with the gate electrode  103  by performing a patterning process only once. 
     A gate insulating layer  106  is formed on the gate electrode  103  and the first capacitor electrode  104 . The gate insulating layer  106  insulates the gate electrode  103  and the active layer  107  from each other. 
     The active layer  107  is formed on the gate insulating layer  106 . The active layer  107  may include various materials. The active layer  107  may include an oxide semiconductor material but is not limited thereto and may include crystalline silicon or amorphous silicon. 
     An etch stopper  108  is formed on the active layer  107 . The source electrode  109  and the drain electrode  110  are formed on the etch stopper  108 . The source electrode  109  and the drain electrode  110  contact an exposed region of the active layer  107 , which is not covered by the etch stopper  108 . 
     That is, a region that acts as a channel of surfaces of the active layer  107  is protected by the etch stopper  108 . The etch stopper  108  prevents an upper surface of the active layer  107  from being damaged during an etch process for patterning the source electrode  109  and the drain electrode  110 . The etch stopper  108  may be formed of various insulating materials. 
     Each of the source electrode  109  and the drain electrode  110  may be formed, but is not limited to, of at least one material selected from the group consisting of Au, Pd, Pt, Ni, Rh, Ru, Ir, Os, Al, Mo, an Al:Nd alloy, and a MoW alloy. 
     In one embodiment, the source electrode  109  or the drain electrode  110  includes the optical blocking unit  111 . In another embodiment, each of the source electrode  109  and the drain electrode  110  includes the optical blocking unit  111 . If only one of the electrodes  109  and  110  includes the optical unit  111 , the electrode having the optical unit  111  may be formed to be closer to the light emitting region than the other electrode to efficiently block light from entering the TFT or at least the active layer  107 . This applies to the embodiments of  FIGS. 2 and 3 . In the current embodiment, the drain electrode  110  includes the optical blocking unit  111 . The optical blocking unit  111  extends from a region of the drain electrode  110 . In one embodiment, the unit  111  extends in a thickness direction of the substrate  101 , i.e., a Y-axis direction in  FIG. 1 . 
     In one embodiment, the optical blocking unit  111  is formed of the same material as the drain electrode  110  and thus prevents light from penetrating into the active layer  107 . In particular, the optical blocking unit  111  prevents light generated from the intermediate layer  116  from being incident on a side or bottom surface of the active layer  107 . In one embodiment, the optical blocking unit  111  is formed to partially overlap the gate electrode  103  in a direction substantially perpendicular to the thickness direction of the substrate  101 , i.e., an X-axis direction in  FIG. 1 . For example, the optical blocking unit  111  may be formed on the same layer on which the gate electrode  103  is formed. That is, the optical blocking unit  111  is formed to contact the substrate  101 . If the buffer layer is formed, the optical blocking unit  111  is formed to contact the buffer layer. 
     A second capacitor electrode  112  is formed on the etch stopper  108  to overlap the first capacitor electrode  104 . The first capacitor electrode  104  and the second capacitor electrode  112  together form one capacitor C. The second capacitor electrode  112  may be formed of the same material as the source electrode  109  and the drain electrode  110 . In one embodiment, the second capacitor electrode  112  is substantially simultaneously formed with the source electrode  109  and the drain electrode  110  by performing a patterning process only once. 
     A passivation layer  113  is formed on the source electrode  109 , the drain electrode  110 , and the second capacitor electrode  112 . The passivation layer  113  may be formed of various insulating materials including organic or inorganic materials. Also, the passivation layer  113  may have a stacked structure of organic and inorganic materials. The passivation layer  113  includes a via-hole  113   a  for exposing a region of the drain electrode  110 . 
     The first electrode  114  is formed on the passivation layer  113 . The first electrode  114  is electrically connected to the drain electrode  110  via the via-hole  113   a . The first electrode  114  may be a transmissive electrode or a reflective electrode. 
     If the first electrode  114  is a transmissive electrode, then the first electrode  114  may include ITO, IZO, ZnO, or In 2 O 3 . Otherwise, if the first electrode  114  is a reflective electrode, then the first electrode  114  may be fabricated by forming a reflective layer by using at least one material selected from the group consisting of Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, and Cr and forming an ITO, IZO, ZnO, or In 2 O 3  layer on the resultant structure. 
     In the current embodiment, the drain electrode  110  is electrically connected to the first electrode  114  but this arrangement is not considered limiting and the source electrode  109  may be connected to the first electrode  114 . If the source electrode  109  is electrically connected to the first electrode  114 , the source electrode  109  includes the optical blocking unit  111 . 
     A pixel defining layer  115  is formed on the first electrode  114 . The pixel defining layer  115  may include various insulating materials and may be formed to expose a predetermined region of the first electrode  114 . The intermediate layer  116  is formed on the exposed region of the first electrode  114 . The second electrode  117  is formed on the intermediate layer  116 . 
     The intermediate layer  116  includes an organic emission layer (not shown). When a voltage is applied to the first electrode  114  and the second electrode  117 , visible light is emitted from the organic emission layer of the intermediate layer  116 . 
     If the organic emission layer of the intermediate layer  116  is a low-molecular weight organic layer, then a hole transport layer (HTL) and a hole injection layer (HIL) may be included between the organic emission layer and the first electrode  114  and an electron transport layer (ETL) and an electron injection layer (EIL) may be included between the organic emission layer and the second electrode  117 . 
     If the organic emission layer of the intermediate layer  116  is a high molecular weight organic layer, then the HTL may be included between the organic emission layer and the first electrode  114 . 
     The second electrode  117  is formed to substantially cover all pixels. The second electrode  117  may be a transmissive or reflective electrode. 
     If the second electrode  117  is a transmissive electrode, then the second electrode  117  may be fabricated by stacking a layer formed of at least one selected from the group consisting of Li, Ca, LiF/Ca, LiF/Al, Al, Ag, and Mg, and a transmissive conductive layer, such as ITO, IZO, ZnO, or In2O3. Alternatively, if the second electrode  117  is a reflective electrode, then the second electrode  117  is formed of at least one material selected from the group consisting of Li, Ca, LiF/Ca, LiF/Al, Al, Ag, and Mg. 
     In the current embodiment, the first electrode  114  and the second electrode  117  are an anode electrode and a cathode electrode, respectively. In another embodiment, the first electrode  114  and the second electrode  117  may be a cathode electrode and an anode electrode, respectively. Also, the above-described materials of the first electrode  114  and the second electrode  117  are just examples and various materials may be used to form them. 
     A sealing unit (not shown) may be formed on the second electrode  117 . In one embodiment, the sealing unit is formed of a transparent material to protect the intermediate layer  116  and the other layers from external moisture or oxygen. The sealing unit may include glass, plastic, or a plurality of stacked layers including organic and inorganic materials. 
     In the organic light-emitting display  100 , the drain electrode  110  includes the optical blocking unit  111 . The optical blocking unit  111  extends in the thickness direction of the substrate  101  and thus prevents light from being incident on a side surface of the active layer  107 . 
     The characteristics of the active layer  107  are likely to be changed by light, thereby degrading the optical reliability of the TFT. In particular, when the active layer  107  includes an oxide semiconductor material, the active layer  107  is very sensitive to light. 
     However, in the current embodiment, the active layer  107  is prevented from being exposed to light so that the characteristics of the active layer  107  may not change, thereby preventing the optical reliability of the TFT from degrading. In particular, light generated from the intermediate layer  116  is prevented from being incident on the side surface of the active layer  107 , thereby protecting the active layer  107  from light. 
     The image quality of the organic light-emitting display  100  is generally influenced by the characteristics of the TFT. In the current embodiment, the active layer  107  included in the TFT is prevented from degrading due to light, and thus, the optical reliability of the TFT is enhanced and the image quality of the organic light-emitting display  100  is improved accordingly. 
     In one embodiment, the optical blocking unit  111  is formed to reach the same layer on which the gate electrode  103  is formed. That is, the optical blocking unit  111  is formed to contact the substrate  101 , thereby maximizing the blocking of light incident on the active layer  107 . 
     Also, the optical blocking unit  111  partially overlaps the via-hole  113   a  so that the thickness of a region of the drain electrode  110  that contacts the first electrode  114  may be increased, thus reducing contact resistance in an interface region between the first electrode  114  and the drain electrode  110 . Furthermore, light incident from the intermediate layer  116  onto the active layer  107  may be blocked effectively. 
       FIG. 2  is a schematic cross-sectional view of an organic light-emitting display  200  according to another embodiment. For convenience of explanation, the organic light-emitting display  200  will now be described focusing on the differences with respect to the  FIG. 1  embodiment. 
     Referring to  FIG. 2 , the organic light-emitting display  200  includes a substrate  201 , a TFT, a first electrode  214 , an intermediate layer  216 , a second electrode  217 , a conductive unit  205 , and an optical blocking unit  211 . The TFT includes a gate electrode  203 , an active layer  207 , a source electrode  209 , and a drain electrode  210 . The source electrode  209  or the drain electrode  210  includes the optical blocking unit  211 . The gate electrode  203  is formed on the substrate  201 . A first capacitor electrode  204  is formed on the substrate  201 . The first capacitor electrode  204  may be formed of the same material as the gate electrode  203 . 
     The conductive unit  205  is also formed on the substrate  201  to be disposed apart from the gate electrode  203 . The conductive unit  205  is formed of the same material as the gate electrode  203 . The gate electrode  203  and the conductive unit  205  may be formed substantially simultaneously by performing a patterning process once. 
     A gate insulating layer  206  is formed on the gate electrode  203 , the first capacitor electrode  204 , and the conductive unit  205 . The active layer  207  is formed on the gate insulating layer  206 . An etch stopper  208  is formed on the active layer  207 , and the source electrode  209  and the drain electrode  210  are formed on the etch stopper  208 . The source electrode  209  and the drain electrode  210  contact an exposed region of the active layer  207 , which is not covered by the etch stopper  208 . 
     The source electrode  209  or the drain electrode  210  includes the optical blocking unit  211 . In the current embodiment, the drain electrode  210  includes the optical blocking unit  211 . The optical blocking unit  211  extends from a region of the drain electrode  210 , and more particularly, extends in a thickness direction of the substrate  201 , i.e., a Y-axis direction in  FIG. 2 . The optical blocking unit  211  is connected to the conductive unit  205 . 
     In one embodiment, the optical blocking unit  211  is formed of the same material as the drain electrode  210  and blocks light from being incident on the active layer  207 . The optical blocking unit  211  is formed to be connected to the conductive unit  205 , on the same layer on which the gate electrode  203  is formed, and thus, the optical blocking unit  211  and the conductive unit  205  effectively prevent light from being incident on a side or bottom surface of the active layer  207 . 
     A second capacitor electrode  212  is formed on the etch stopper  208  to overlap the first capacitor electrode  204 . The first capacitor electrode  204  and the second capacitor electrode  212  together form one capacitor C. 
     A passivation layer  213  is formed on the source electrode  209 , the drain electrode  210 , and the second capacitor electrode  212 . The passivation layer  213  includes a via-hole  213   a  to expose a region of the drain electrode  210 . 
     The first electrode  214  is formed on the passivation layer  213 . The first electrode  214  is electrically connected to the drain electrode  210  via the via-hole  213   a . In the current embodiment, the drain electrode  210  is electrically connected to the first electrode  214 . However, the source electrode  209  may be connected to the first electrode  214 . When the source electrode  209  is connected to the first electrode  214 , the source electrode  209  includes the optical blocking unit  211 . 
     A pixel defining layer  215  is formed on the first electrode  214 . The pixel defining layer  215  may include various insulating materials and exposes a predetermined region of the first electrode  214 . The intermediate layer  216  is formed on the exposed region of the first electrode  214 . The second electrode  217  is formed on the intermediate layer  216 . 
     A sealing unit (not shown) may be formed on the second electrode  217 . The sealing unit protects the intermediate layer  216  and the other layers from external moisture or oxygen. T he sealing unit may include glass, plastic, or a plurality of stacked layers including organic and inorganic materials. 
     In the organic light-emitting display  200 , the drain electrode  210  includes the optical blocking unit  211 . The optical blocking unit  211  extends in the thickness direction of the substrate  201 , and is also connected to the conductive unit  205 . Thus, it is possible to prevent the properties of the active layer  207  from degrading due to light by blocking light from being incident on a side or bottom surface of the active layer  207 , thereby improving the image quality of the organic light-emitting display  200 . 
     For example, the optical blocking unit  211  does not need to extend to the substrate  201  owing to the conductive unit  205 , thereby simplifying a process of forming the optical blocking unit  211 . 
     Also, the optical blocking unit  211  partially overlaps the via-hole  213   a , and thus, the thickness of the drain electrode  210  that contacts the first electrode  214  is increased, thus reducing contact resistance in an interface region between the first electrode  214  and the drain electrode  210 . Furthermore, it is possible to effectively block light from being incident from the intermediate layer  216  onto the active layer  207 . 
       FIG. 3  is a schematic cross-sectional view of an organic light-emitting display  300  according to another embodiment. For convenience of explanation, the organic light-emitting display  300  will now be described focusing on the differences with respect tot the embodiments shown in  FIGS. 1 and 2 . 
     Referring to  FIG. 3 , the organic light-emitting display  300  includes a substrate  301 , a TFT, a first electrode  314 , an intermediate layer  316 , a second electrode  317 , and an optical blocking unit  311 . The TFT includes a gate electrode  303 , an active layer  307 , a source electrode  309 , and a drain electrode  310 . The source electrode  309  or the drain electrode  310  includes the optical blocking unit  311 . 
     Specifically, the gate electrode  303 , a first capacitor electrode  304 , and the first electrode  314  are formed on the substrate  301 . The gate electrode  303  includes a first conductive layer  303   a  and a second conductive layer  303   b . Each of the first conductive layer  303   a  and the second conductive layer  303   b  may be formed of various materials. For example, the first conductive layer  303   a  may be formed of a transmissive conductive material, such as ITO, IZO, or In 2 O 3 , and the second conductive layer  303   b  may be formed of at least one material selected from the group consisting of Mo, W, Al, Cu, and Ag. 
     The first capacitor electrode  304  includes a first layer  304   a  and a second layer  304   b . The first capacitor electrode  304  may be formed of the same material as the gate electrode  303 . That is, the first layer  304   a  may be formed of the same material as the first conductive layer  303   a  and the second layer  304   b  may be formed of the same material as the second conductive layer  303   b.    
     The first electrode  314  is formed on the substrate  301  to be disposed apart from the gate electrode  303  and may be formed of the same material as the first conductive layer  303   a  of the gate electrode  303 . 
     The gate electrode  303 , the first capacitor electrode  304 , and the first electrode  314  may be patterned substantially simultaneously. In this regard, photolithography may be performed using a half-tone mask. 
     A gate insulating layer  306  is formed on the gate electrode  303 , the first capacitor electrode  304 , and the first electrode  314 . The active layer  307  is formed on the gate insulating layer  306 . An etch stopper  308  is formed on the active layer  307 , and the source electrode  309  and the drain electrode  310  are formed on the etch stopper  308 . The source electrode  309  and the drain electrode  310  contact exposed regions of the active layer  307  that are not covered by the etch stopper  308 , respectively. 
     The drain electrode  310  is electrically connected to the first electrode  314 . The gate insulating layer  306  and the etch stopper  308  are etched from the first electrode  314  so as to expose a region of the first electrode  314 , and the drain electrode  310  is connected to the exposed region of the first electrode  314 . 
     The source electrode  309  or the drain electrode  310  includes the optical blocking unit  311 . In the current embodiment, the drain electrode  310  includes the optical blocking unit  311 . The optical blocking unit  311  extends from a region of the drain electrode  310 , and more particularly, extend in a thickness direction of the substrate  301 , i.e., a Y-axis direction in  FIG. 3 . 
     Also, the optical blocking unit  311  partially overlaps the gate electrode  303  in a direction substantially perpendicular to the thickness direction of the substrate  301 , i.e., an X-axis direction. For example, the optical blocking unit  311  contacts a side surface of the first electrode  314 . The optical blocking unit  311  may contact a side surface of the first electrode  314  facing the gate electrode  303 . Also, the optical blocking unit  311  is formed to cover an interface region between a side surface of the first electrode  314  and the substrate  301 . 
     Although not shown, if the buffer layer is formed between the substrate  301  and the first electrode  314 , the optical blocking unit  311  is formed to cover an interface region between a side surface of the first electrode  314  and the buffer layer. 
     In one embodiment, the optical blocking unit  311  is formed of the same material as the drain electrode  310  and blocks light from being incident on the active layer  307 . According to one embodiment, since the optical blocking unit  311  contacts the side surface of the first electrode  314 , light generated from the intermediate layer  316  may be effectively prevented from being incident on a side or bottom surface of the active layer  307  via the side surface of the first electrode  314 . 
     A second capacitor electrode  312  is formed on the etch stopper  308  to overlap the first capacitor electrode  304 . The first capacitor electrode  304  and the second capacitor electrode  312  together form one capacitor C. 
     A pixel defining layer  315  is formed on the source electrode  309 , the drain electrode  310 , and the second capacitor electrode  312 . Predetermined regions of the pixel defining layer  315 , the gate insulating layer  306 , and the etch stopper  308  are etched to expose a region of the first electrode  314 . The intermediate layer  316  is formed on the exposed region of the first electrode  314 . The second electrode  317  is formed on the intermediate layer  316 . 
     In the current embodiment, since the pixel defining layer  315  also acts as a passivation layer, the thickness of the organic light-emitting display  300  decreases and the efficiency of a process of fabricating the display  300  increases. 
     A sealing unit (not shown) may be formed on the second electrode  317 . The sealing unit protects the intermediate layer  316  and the other layers from external moisture or oxygen. The sealing unit may be formed of a transparent material. The sealing unit may include glass, plastic, or a plurality of stacked layers including organic and inorganic materials. 
     In the organic light-emitting display  300 , the drain electrode  310  includes the optical blocking unit  311 . The optical blocking unit  311  extends in the thickness direction of the substrate  301 . Also, the optical blocking unit  311  contacts the side surface of the first electrode  314  facing the gate electrode  303 , thereby blocking light from being incident on a side or bottom surface of the active layer  307 . Also, light passing through a side surface of the first electrode  314  is prevented from being incident on the active layer  307 . Accordingly, the performance of the active layer  307  is not degraded by light, and thus, the image quality of the display  300  is enhanced. 
     Thus, it is possible to improve image quality. 
     While certain embodiments have been particularly shown and described, 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 following claims.