Organic Light Emitting Diode Display

Abstract

The present disclosure relates to an organic light emitting diode display. According to an exemplary embodiment, the organic light emitting diode display includes: a substrate; a first buffer layer, the first buffer layer is on the substrate; a first semiconductor layer, the first semiconductor layer is on the first buffer layer; a first gate insulating layer, the first gate insulating layer is on the first semiconductor layer; a first gate electrode and a barrier layer, the first gate electrode and the barrier layer are on the first gate insulating layer; a second buffer layer, the second buffer layer is on the first gate electrode; a second semiconductor layer, the second semiconductor layer is on the second buffer layer; a second gate insulating layer, the second gate insulating layer is on the second semiconductor layer; and a second gate electrode, the second gate electrode is on the second gate insulating layer.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] The entire contents of Korean Patent Application No. 10-2018-0118769 filed on October 5, 2018 in the Korean Intellectual Property Office and entitled: “Organic Light Emitting Diode Display” are incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to organic light emitting diode displays. Background Art

[0004] The organic light emitting element of the organic light emitting diode display includes two electrodes and an organic light emitting layer positioned between the two electrodes. Electrons injected from the cathode as an electrode and holes injected from the anode as the other electrode combine with each other in the organic light emitting layer to form excitons. When the excitons release energy, light is emitted.

[0005] As organic light emitting diode (OLED) display technology develops, organic light emitting diode (OLED) displays are becoming high resolution, and thus, demand for highly integrated organic light emitting diode displays is growing. Summary of the invention

[0006] The present disclosure provides an organic light emitting diode display having increased design freedom, high resolution, and improved display quality.

[0007] According to an exemplary embodiment, an organic light emitting diode display includes: a substrate; a first buffer layer, the first buffer layer is on the substrate; a first semiconductor layer, the first semiconductor layer is on the first buffer layer; a first gate insulating layer, the first gate insulating layer is on the first semiconductor layer; a first gate electrode and a barrier layer, the first gate electrode and the barrier layer are on the first gate insulating layer; a second buffer layer, the second buffer layer is on the first gate electrode; a second semiconductor layer, the second semiconductor layer is on the second buffer layer; a second gate insulating layer, the second gate insulating layer is on the second semiconductor layer; and a second gate electrode, the second gate electrode is on the second gate insulating layer.

[0008] The barrier layer may overlap the second semiconductor layer.

[0009] The blocking layer may be at the same layer as the first gate electrode.

[0010] The organic light emitting diode display according to the present exemplary embodiment may further include a driving voltage line transmitting a driving voltage, and the blocking layer may be connected to the driving voltage line to receive the driving voltage.

[0011] The first semiconductor layer may include: a first channel region, the first channel region overlapping the first gate electrode; and a first source region and a first drain region, the first source region and the first drain region are at respective sides of the first channel region, and the second semiconductor layer may include: a second channel region, the second channel region overlapping the second gate electrode; and a second source region and a second drain region, the second source region and the second drain region are at respective sides of the second channel region.

[0012] The barrier layer may overlap the second channel region.

[0013] The organic light emitting diode display may further include a third gate insulating layer on the second gate electrode and a second storage electrode on the third gate insulating layer and overlapping the first storage electrode of the second gate electrode.

[0014] The organic light emitting diode display may further include: a first source electrode and a first drain electrode, the first source electrode and the first drain electrode being connected to the first source region and the first drain region, respectively; and a second source electrode and a second drain electrode, the second source electrode and the second drain electrode being connected to the second source region and the second drain region, respectively, and the second storage electrode may be connected to the second drain electrode.

[0015] The organic light emitting diode display may further include: a pixel electrode on the second storage electrode; an organic emission layer on the pixel electrode; and a common electrode on the organic emission layer, and the second drain electrode may be connected to the pixel electrode.

[0016] The organic light emitting diode display may further include an encapsulation layer on the common electrode.

[0017] The organic light emitting diode display may further include: a first source electrode and a first drain electrode, the first source electrode and the first drain electrode being connected to the first source region and the first drain region, respectively; and a second source electrode and a second drain electrode, the second source electrode and the second drain electrode being connected to the second source region and the second drain region, respectively, and the second storage electrode may be connected to the driving voltage line.

[0018] One of the first semiconductor layer and the second semiconductor layer may be an oxide semiconductor and the other may include polysilicon.

[0019] An organic light emitting diode display according to an exemplary embodiment includes: a substrate; a first transistor, the first transistor being on the substrate; a second transistor, the second transistor being on the first transistor; and a blocking layer, the blocking layer being below the second transistor, wherein the first transistor includes: a first semiconductor layer, the first semiconductor layer being on the substrate; and a first gate electrode, the first gate electrode being on the first semiconductor layer, wherein the blocking layer is on a layer covering the first semiconductor layer.

[0020] The organic light emitting diode display may further include a buffer layer between the first transistor and the second transistor, and the second transistor may include: a second semiconductor layer on the buffer layer; and a second gate electrode on the second semiconductor layer.

[0021] The second semiconductor layer may include a channel region overlapping the second gate electrode, and a source region and a drain region at respective sides of the channel region, and the barrier layer may overlap the channel region.

[0022] The organic light emitting diode display according to the present exemplary embodiment may further include a driving voltage line transmitting a driving voltage, and the blocking layer is connected to the driving voltage line to receive the driving voltage.

[0023] The blocking layer may be in the same layer as the first gate electrode.

[0024] The first transistor may include a third gate electrode on and overlapping the first gate electrode, and the blocking layer may be on the same layer as the third gate electrode.

[0025] The barrier layer may also overlap the source region and the drain region of the second semiconductor layer.

[0026] One of the first semiconductor layer and the second semiconductor layer may be an oxide semiconductor and the other may include polysilicon. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Features will become apparent to those skilled in the art by describing in detail exemplary embodiments with reference to the accompanying drawings, in which:

[0028] Figure 1 An organic light emitting diode display according to an exemplary embodiment is shown;

[0029] Figure 2 An equivalent circuit diagram showing one pixel of an organic light emitting diode display according to an exemplary embodiment;

[0030] Figure 3 A cross-sectional view showing an organic light emitting diode display according to an exemplary embodiment;

[0031] Figure 4 A graph showing a transient afterimage duration of an organic light emitting diode display according to a comparative example and an exemplary embodiment;

[0032] Figure 5 An equivalent circuit diagram showing one pixel of an organic light emitting diode display according to another exemplary embodiment;

[0033] Figure 6 showing a cross-sectional view of an organic light emitting diode display according to another exemplary embodiment; and

[0034] Figure 7 A cross-sectional view illustrating an organic light emitting diode display according to another exemplary embodiment is shown. DETAILED DESCRIPTION

[0035] Example embodiments will now be described more fully below with reference to the accompanying drawings; however, the example embodiments may be implemented in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey exemplary implementations to those skilled in the art.

[0036] In order to clearly explain the embodiments, elements that are not directly related to the embodiments are omitted, and the same reference numerals are attached to the same or similar constituent elements throughout the specification.

[0037] In addition, for better understanding and ease of description, the size and thickness of each construction shown in the drawings are arbitrarily shown. In the drawings, the thickness of layers, films, panels, regions, etc. are exaggerated for clarity. In the drawings, the thickness of some layers and regions are exaggerated for better understanding and ease of description.

[0038] It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, the element may be directly on the other element, or there may be intervening elements. Conversely, when an element is referred to as being "directly on" another element, there are no intervening elements. In addition, in the specification, the words "on..." or "above..." indicate positioning on or below an object part, and do not necessarily mean positioning on the upper side of an object part based on the direction of gravity.

[0039] In addition, unless explicitly described to the contrary, the word “comprise” will be understood to imply the inclusion of stated elements but not the exclusion of any other elements.

[0040] Furthermore, in this specification, the phrase "on a plane" means observing an object portion from the top, and the phrase "on a cross section" means observing a cross section formed by vertically cutting the object portion from the side.

[0041] Figure 1 is a block diagram of an organic light emitting diode display according to an exemplary embodiment. Figure 1 According to an exemplary embodiment, the organic light emitting diode display may include a gate driver GD, a data driver DD, and a pixel unit 40. The pixel unit 40 includes a plurality of pixels PX. The pixel PX represents the minimum unit for display, and the organic light emitting diode display displays an image through the plurality of pixels PX.

[0042] The gate driver GD generates a scan signal corresponding to a driving power and a control signal supplied from the outside, and supplies the scan signal to the gate line 152. The pixels PX are selected by the scan signal to sequentially receive the data voltage.

[0043] The gate driver GD may be a thin film transistor on a substrate together with a pixel circuit included in the pixel unit 40 , or may be mounted on the substrate in a chip shape and may be variously positioned around the pixel unit 40 .

[0044] The data driver DD generates a data voltage corresponding to data and a control signal supplied from the outside and supplies the data voltage to the data line 171, and may be variously positioned around the pixel unit 40. Whenever a scan signal is supplied, the data voltage supplied to the data line 171 is supplied to the pixel PX selected by the scan signal. According to an embodiment, the organic light emitting diode display may further include a light emission control driver that supplies a light emission control signal.

[0045] The pixel unit 40 includes a plurality of pixels PX at intersections of the gate line 152 and the data line 171. The pixel unit 40 receives a driving voltage ELVDD as high potential pixel power and a common voltage ELVSS as low potential pixel power from the outside, and the driving voltage ELVDD and the common voltage ELVSS are transmitted to each pixel PX.

[0046] The pixel PX emits light having brightness corresponding to the driving current flowing from the driving voltage ELVDD to the common voltage ELVSS corresponding to the data voltage, thereby displaying an image.

[0047] In the following, reference will be made to Figure 2 and Figure 3 An organic light emitting diode display according to an exemplary embodiment is described. Figure 2 is an equivalent circuit diagram of one pixel of an organic light emitting diode display according to an exemplary embodiment. Figure 3A cross-sectional view illustrating an organic light emitting diode display according to an exemplary embodiment.

[0048] Reference Figure 2 The organic light emitting diode display according to the exemplary embodiment includes a plurality of signal lines 152, 171 and 172, a plurality of transistors T 1 and T 2 , storage capacitor C st and organic light-emitting diodes OLED. In addition, Figure 3 As can be seen in FIG. 1 , the organic light emitting diode display according to the present exemplary embodiment includes a barrier layer 160, the barrier layer 160 being disposed on a plane, for example, in a vertical direction DV orthogonal to the plane, and being in contact with the driving transistor T 2 overlapping.

[0049] The signal lines 152, 171, and 172 include a gate line 152 transmitting a scan signal Sn, a data line 171 transmitting a data voltage Dm, and a driving voltage line 172 transmitting a driving voltage ELVDD. 1 and T 2 Including switching transistor T 1 and the driving transistor T 2 .

[0050] Switching transistor T 1 The gate electrode connected to the gate line 152, the first electrode connected to the data line 171 and the first electrode connected to the driving transistor T 2 The second electrode of the gate electrode of the switching transistor T 1 The second electrode is also connected to the storage capacitor C st The first storage electrode of the switch transistor T 1 is connected to the gate line 152 to be turned on in response to the scan signal Sn, and when the switching transistor T 1 When turned on, the data voltage Dm supplied through the data line 171 is supplied to the first storage capacitor C st a first storage electrode.

[0051] Drive transistor T 2 The first electrode of the driving transistor T may be connected to the driving voltage line 172 and connected to the barrier layer 160. 2 The gate electrode can be connected to the storage capacitor C st , so that the first storage electrode receives the first electrode driving voltage ELVDD. The driving transistor T 2 The second electrode of the organic light emitting diode OLED can be connected to the first electrode and connected to the storage capacitor C st The second storage electrode of the driving transistor T 2 According to the storage capacitor C stThe data voltage in the OLED outputs a driving current to the organic light emitting diode OLED.

[0052] Storage capacitor C st The storage capacitor C includes a first storage electrode and a second storage electrode. st The first storage electrode is connected to the switching transistor T 1 The second electrode is connected to the driving transistor T 2 The gate electrode of the storage capacitor C st The second storage electrode is connected to the driving transistor T 2 The second electrode of the storage capacitor C is connected to the first electrode of the organic light emitting diode OLED. st can be stored through the switching transistor T 1 The supplied data voltage Dm is stored in the storage capacitor C st The data voltage Dm is controlled by the driving transistor T 2 The magnitude of the drive current is determined by the degree of conduction. Figure 2 A structure including two transistors and one capacitor is shown, but may additionally include one or more transistors or capacitors.

[0053] The organic light emitting diode OLED includes a driving transistor T connected to 2 The first electrode of the organic light emitting diode OLED may be an anode electrode, and the second electrode of the organic light emitting diode OLED may be a cathode electrode. The organic light emitting diode OLED is connected to the driving transistor T 2 The output drive current emits light and displays gray levels according to the brightness level.

[0054] The barrier layer 160 is electrically connected to a driving voltage line 172 that transmits a driving voltage ELVDD. The barrier layer 160 may be formed of a metal having a conductive property or a semiconductor material having a conductive property equivalent to the conductive property. The driving voltage ELVDD is constantly applied to the barrier layer 160 to prevent the potential from being changed while injecting specific charges into the barrier layer 160. The barrier layer 160 has a similar structure to the driving transistor T in the circuit diagram. 2 However, since a predetermined voltage is applied to the barrier layer 160, the driving transistor T 2 Not conducting, but driving transistor T 2 Having predetermined characteristics.

[0055] Reference Figure 3 The organic light emitting diode display according to the present exemplary embodiment includes a substrate 110, a switching transistor T 1 , driving transistor T 2 and organic light-emitting diodes OLED.

[0056] The substrate 110 may include a flexible material such as plastic that can be bent, folded, and folded. For example, the substrate 110 may be made of a polymer such as polyimide, polyamide, polycarbonate, or polyethylene terephthalate. The substrate 110 may be a rigid substrate made of a material such as glass.

[0057] The first buffer layer 121 is on the substrate 110. The first buffer layer 121 may include silicon nitride (SiN x ), silicon oxide (SiO x ) etc. Since the first buffer layer 121 is between the substrate 110 and the first semiconductor layer 136a, impurities are prevented from diffusing from the substrate 110 into the first semiconductor layer 136a, and the substrate 110 is planarized, thereby relieving stress on the first semiconductor layer 136a formed on the first buffer layer 121.

[0058] The first semiconductor layer 136a is on the first buffer layer 121. The first semiconductor layer 136a may be made of polycrystalline silicon. For example, the first semiconductor layer 136a may be made of polycrystalline silicon formed by crystallizing amorphous silicon by a crystallization method such as excimer laser annealing (ELA). The first semiconductor layer 136a may include a first channel region 134a, a first source region 133a, and a first drain region 135a. The first source region 133a and the first drain region 135a are on respective sides of the first channel region 134a. The first channel region 134a is an intrinsic semiconductor in which impurities are not doped, and the first source region 133a and the first drain region 135a are impurity semiconductors in which conductive impurities are doped. The conductive impurities may be P-type impurities.

[0059] The first gate insulating layer 122 is on the first semiconductor layer 136a. The first gate insulating layer 122 may include silicon nitride (SiN x ), silicon oxide (SiO x ) or a single layer of at least one of them or a multilayer thereof.

[0060] The first gate electrode 155a and the barrier layer 160 are on the first gate insulating layer 122 (e.g., directly on the first gate insulating layer 122). The barrier layer 160 is in the same layer as the first gate electrode 155a, e.g., directly on the first gate insulating layer 122, but because the first semiconductor layer 136a is between the first gate electrode 155a and the substrate 110, the barrier layer 160 can be closer to the substrate 110 along the vertical direction DV.

[0061] The first gate electrode 155a may be a multilayer including a metal layer including at least one of copper (Cu), a copper alloy, aluminum (Al), an aluminum alloy, molybdenum (Mo), and a molybdenum alloy. The first gate electrode 155a and the first semiconductor layer 136a may constitute a switching transistor T 1 .

[0062] For example, the barrier layer 160 is formed in the same layer with the first gate electrode 155a without an additional mask process, thereby simplifying the process. The barrier layer 160 is electrically connected to the driving voltage line 172 through the opening to receive the driving voltage ELVDD. The barrier layer 160 can be formed of a metal having a conductive property or a semiconductor material having a conductive property equivalent to the conductive property.

[0063] The second buffer layer 141 is on the first gate electrode 155a, the barrier layer 160, and the first gate insulating layer 122. The second buffer layer 141 may include silicon nitride (SiN x ), silicon oxide (SiO x ) etc. The second buffer layer 141 has openings that expose the first source region 133a and the first drain region 135a and the barrier layer 160, respectively.

[0064] The second semiconductor layer 136b is on the second buffer layer 141. The second semiconductor layer 136b includes a second channel region 134b, a second source region 133b, and a second drain region 135b. The second source region 133b and the second drain region 135b are on respective sides of the second channel region 134b.

[0065] The second semiconductor layer 136b may be made of an oxide semiconductor. Although the first semiconductor layer 136a is made of polysilicon and the second semiconductor layer 136b is an oxide semiconductor, the switching transistor T 1 The first semiconductor layer 136a may be formed of an oxide semiconductor having better off-current characteristics than polysilicon, and the driving transistor T 2 The second semiconductor layer 136b may be formed of polysilicon. Alternatively, both the first semiconductor layer 136a and the second semiconductor layer 136b may be made of the same material, for example, polysilicon or an oxide semiconductor.

[0066] The second gate insulating layer 123 is on the second semiconductor layer 136b. The second gate insulating layer 123 may include silicon nitride (SiN x ), silicon oxide (SiO x ) or more than one layer thereof.

[0067] The first source electrode 161a and the first drain electrode 162a are on the second gate insulating layer 123. The first source electrode 161a and the first drain electrode 162a are connected to the first source region 133a and the first drain region 135a of the first semiconductor layer 136a through openings formed in the first gate insulating layer 122, the second buffer layer 141, and the second gate insulating layer 123, respectively.

[0068] The second gate electrode 155b overlapping the second channel region 134b is also on the second gate insulating layer 123. The second gate electrode 155b may be a multilayer including a metal layer including at least one of copper (Cu), copper alloy, aluminum (Al), aluminum alloy, molybdenum (Mo), and molybdenum alloy. The second gate electrode 155b and the second semiconductor layer 136b may constitute a driving transistor T. 2 .

[0069] In the organic light emitting diode display according to the present exemplary embodiment, the switching transistor T 1 and the driving transistor T 2 On different layers. In other words, the switching transistor T 1 The first semiconductor layer 136a and the driving transistor T 2 The second semiconductor layer 136b is on a different layer. Therefore, the switching transistor T can be reduced. 1 and the driving transistor T 2 The spacing along the horizontal direction DH between the transistors may be reduced, or the transistors may partially overlap along the vertical direction DV, thereby improving the degree of design freedom, increasing the aperture ratio of the pixel and / or improving the resolution of the display device.

[0070] The barrier layer 160 may be perpendicular to the driving transistor T in the vertical direction DV. 2 The barrier layer 160 may also overlap with the second source region 133b and the second drain region 135b at respective sides of the second channel region 134b, for example, may overlap with the entire second semiconductor layer 136b. In addition, the barrier layer 160 may not overlap with the switching transistor T 1 Since the barrier layer 160 overlaps the first channel region 134a of the driving transistor T 2 Below, it is possible to make the switching transistor T 1 and the driving transistor T 2The kickback voltage caused by the parasitic capacitance of the organic light emitting diode display is minimized, and as described in detail below, the display quality of the organic light emitting diode display can be improved by preventing afterimages. In addition, the barrier layer 160 under the second semiconductor layer 136b is not floating, but receives the driving voltage ELVDD. For example, the barrier layer 160 may extend in the horizontal direction DH beyond the second semiconductor layer 136b to receive the driving voltage ELVDD, thereby preventing the degradation of the display quality due to unnecessary parasitic capacitance.

[0071] The third gate insulating layer 124 is on the second gate insulating layer 123 , the first source electrode 161 a , the first drain electrode 162 a and the second gate electrode 155 b . The second drain electrode 162 b and the second storage electrode 165 extending from the second drain electrode 162 b in the horizontal direction DH are on the third gate insulating layer 124 .

[0072] The second drain electrode 162 b is connected to the driving transistor T through an opening formed in the second gate insulating layer 123 and the third gate insulating layer 124. 2 The second storage electrode 165 extends from the second drain electrode 162b in the horizontal direction DH to overlap the second gate electrode 155b. The second gate electrode 155b and the second storage electrode 165 overlap each other in the vertical direction DV via the third gate insulating layer 124 to form a storage capacitor C st In this case, the second gate electrode 155b may be a storage capacitor C st The third gate insulating layer 124 is made of a dielectric material, and the storage capacitor C st The charge charged in the storage electrode 155 and the voltage between the first storage electrode 155 b and the second storage electrode 165 are determined.

[0073] The interlayer insulating layer 142 is on the third gate insulating layer 124 and the second storage electrode 165. The interlayer insulating layer 142 may be made of silicon nitride (SiN x ), silicon oxide (SiO x ) or more than one layer thereof.

[0074] The second source electrode 161b and the connecting member 174 are on the interlayer insulating layer 142. The second source electrode 161b is connected to the second source region 133b of the second semiconductor layer 136b through the openings in the interlayer insulating layer 142, the second gate insulating layer 123, and the third gate insulating layer 124. The connecting member 174 is connected to the driving transistor T through the opening in the interlayer insulating layer 142. 2 The second drain electrode 162b and the storage capacitor C st The second storage electrode 165 is formed on the substrate.

[0075] The second source electrode 161b extends and is connected to the driving voltage line 172 to receive the driving voltage ELVDD. The second source electrode 161b is also connected to the barrier layer 160 through the openings in the second buffer layer 141, the second gate insulating layer 123, the third gate insulating layer 124, and the interlayer insulating layer 142. Therefore, the barrier layer 160 is not floating and receives the driving voltage ELVDD.

[0076] The data line 171 is also on the interlayer insulating layer 142. The data line 171 is connected to the switching transistor T through the opening in the third gate insulating layer 124 and the interlayer insulating layer 142. 1 The first source electrode 161a is used to transmit the data voltage to the switching transistor T 1 .

[0077] The passivation layer 180 is on the interlayer insulating layer 142, the data line 171, the second source electrode 161b, and the connecting member 174. The passivation layer 180 covers the interlayer insulating layer 142, the second source electrode 161b, the data line 171, and the connecting member 174 to provide a flat upper surface so that the pixel electrode 191 can be formed without a step on the passivation layer 180. The passivation layer 180 may be formed of an organic material (e.g., polyacrylate resin or polyimide resin, etc.) or a stacked film of an organic material and an inorganic material.

[0078] The pixel electrode 191 is on the passivation layer 180. The pixel electrode 191 is connected to the connection member 174 through the opening formed in the passivation layer 180. Therefore, the pixel electrode 191 is connected to the driving transistor T through the connection member 174. 2 The second drain electrode 162b of the driving transistor T 2 Connected to the pixel electrode 191 to supply a driving current to the organic light emitting diode OLED.

[0079] The partition wall 361 covers the passivation layer 180 and the pixel electrode 191 and has a pixel opening 365 exposing the pixel electrode 191. The partition wall 361 may include an organic material (eg, polyacrylate resin or polyimide resin, etc.) or an inorganic material (eg, a silicon dioxide-based inorganic material).

[0080] The organic emission layer 370 is on the pixel electrode 191 exposed by the pixel opening 365. The organic emission layer 370 may be formed of a low molecular weight organic material or a high molecular weight organic material such as PEDOT (poly (3,4-ethylenedioxythiophene)). In addition, the organic emission layer 370 may be a multilayer further including 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 organic emission layer 370 may include a red organic emission layer that emits red light, a green organic emission layer that emits green light, and a blue organic emission layer that emits blue light.

[0081] The common electrode 270 is on the organic emission layer 370. The common electrode 270 may cover a plurality of pixels. The pixel electrode 191, the organic emission layer 370, and the common electrode 270 may form an organic light emitting diode OLED.

[0082] Here, the pixel electrode 191 may be an anode of a hole injection electrode, and the common electrode 270 may be a cathode of an electron injection electrode. Alternatively, according to a driving method of an organic light emitting diode display, the pixel electrode 191 may be a cathode, and the common electrode 270 may be an anode. Holes and electrons are injected into the organic emission layer 370 from the pixel electrode 191 and the common electrode 270, respectively, and light is emitted when excitons, which are a combination of the injected holes and electrons, transition from an excited state to a ground state.

[0083] The encapsulation layer 390 is on the common electrode 270. The encapsulation layer 390 encapsulates the organic light emitting diode OLED to prevent the penetration of external moisture and oxygen, because the organic light emitting diode OLED is very vulnerable to moisture and oxygen. The encapsulation layer 390 may include a plurality of layers and may be formed of a composite film including both an inorganic film and an organic film. The encapsulation layer 390 may be formed of three layers in which an inorganic film, an organic film, and an inorganic film are sequentially formed.

[0084] Figure 4 is a graph showing the duration of instantaneous afterimages of organic light emitting diode displays according to comparative examples and exemplary embodiments. Figure 4 , A represents an organic light emitting diode display without a barrier layer according to a comparative example, and B represents an organic light emitting diode display including a barrier layer overlapping a channel region of a driving transistor according to an exemplary embodiment.

[0085] In an organic light emitting diode display, if black and white are displayed for 10 seconds and then low grayscale is driven at the same time, a brightness difference occurs in an area displaying black and an area displaying white even if the same color is driven. In detail, an area displaying black is brighter than a grayscale to be driven immediately after grayscale driving of low grayscale, and an area displaying white is darker than a grayscale to be driven. An instantaneous afterimage means an afterimage recognized by a brightness difference.

[0086] Figure 4 The duration of the momentary afterimage is found by measuring the time it takes for the brightness difference between an area displaying black and an area displaying white to reach 0.4% immediately after grayscale driving from a low grayscale. Here, the brightness difference is calculated by (BW) / (B+W), where B is the brightness of an area displaying black, and W is the brightness of an area displaying white. The momentary afterimage is directly related to the display quality of the display device, so that if the duration of the momentary afterimage is reduced, a clearer image can be achieved. The momentary afterimage can be improved by minimizing the vertical crosstalk between transistors in an organic light emitting diode display.

[0087] Reference Figure 4 , in case A, the instantaneous afterimage lasts for 7.66151 seconds. However, in case B, the instantaneous afterimage lasts for only 4.42379 seconds. Therefore, compared with the organic light emitting diode display without a blocking layer (comparative example), the organic light emitting diode display including a blocking layer according to the embodiment improves the instantaneous afterimage by about 3.2 seconds.

[0088] Next, we will refer to Figure 5 and Figure 6 An organic light emitting diode display according to an exemplary embodiment is described. Figure 5 is an equivalent circuit diagram of one pixel of an organic light emitting diode display according to another exemplary embodiment.

[0089] Reference Figure 5 The organic light emitting diode display according to the exemplary embodiment includes signal lines 152, 171 and 172, two transistors T 1 and T 2 , storage capacitor C st In addition, the organic light emitting diode display according to the present exemplary embodiment includes a barrier layer 160, which is in a plane, for example, in a vertical direction DV with the driving transistor T 2 In addition to connecting to the driving voltage line 172 and the driving transistor T 2 The first electrode of the storage capacitor C st Except for the second storage electrode, this embodiment is similar to Figure 2 The embodiments are described below and redundant descriptions are not repeated.

[0090] Storage capacitor C st The storage capacitor C includes a first storage electrode and a second storage electrode. st The first storage electrode is connected to the switching transistor T 1 The second electrode and the driving transistor T 2 The gate of the storage capacitor C stThe second storage electrode of is connected to the driving voltage line 172. The storage capacitor C st The second storage electrode is also connected to the driving transistor T 2 The first electrode and the barrier layer 160 are provided.

[0091] Storage capacitor C st can be stored through the switching transistor T 1 The supplied data voltage Dm is stored in the storage capacitor C st The data voltage Dm in the drive transistor T is adjusted by 2 The degree of conduction determines the size of the drive current.

[0092] The blocking layer 160 is electrically connected to a driving voltage line 172 that transmits a driving voltage ELVDD. The driving voltage ELVDD is constantly applied to the blocking layer 160 to prevent the potential from being changed while a specific charge is injected into the blocking layer 160. The blocking layer 160 has a similar structure to the driving transistor T in the circuit diagram. 2 However, since a predetermined voltage is applied to the barrier layer 160, the driving transistor T 2 Not conducting, but driving transistor T 2 Having predetermined characteristics.

[0093] Figure 6 is a cross-sectional view of an organic light emitting diode display according to another exemplary embodiment. Figure 6 The construction is similar to Figure 3 The structure of Figure 3 A detailed description of the overlap.

[0094] Reference Figure 6 The organic light emitting diode display according to the present exemplary embodiment includes a substrate 110, a switching transistor T 1 , driving transistor T 2 and organic light-emitting diodes OLED.

[0095] The second source electrode 161b extends and is connected to the driving voltage line 172 to receive the driving voltage ELVDD. The second source electrode 161b is also connected to the barrier layer 160 through the openings in the second buffer layer 141, the second gate insulating layer 123, the third gate insulating layer 124, and the interlayer insulating layer 142. Therefore, the barrier layer 160 is not floating and receives the driving voltage ELVDD.

[0096] In addition, Figure 3 Different from the first source electrode 161b, the second source electrode 161b is also connected to the storage capacitor C through an opening formed in the interlayer insulating layer 142. st The second storage electrode 165 is not connected to the second drain electrode 162b. Therefore, the storage capacitor Cst The second storage electrode 165 receives the driving voltage ELVDD. Figure 3 The same as in.

[0097] Figure 7 is a cross-sectional view of an organic light emitting diode display according to another exemplary embodiment. Figure 7 The organic light emitting diode display according to the present exemplary embodiment includes a first transistor T 1 , the second transistor T 2 and a barrier layer 260 .

[0098] The organic light emitting diode display according to the present exemplary embodiment includes a substrate 210 and a first buffer layer 221 on the substrate 210 .

[0099] The first semiconductor layer 236a is on the first buffer layer 221. The first semiconductor layer 236a may be made of polysilicon and includes a first channel region 234a, a first source region 233a, and a first drain region 235a. The first source region 233a and the first drain region 235a are at respective sides of the first channel region 234a.

[0100] The first gate insulating layer 222 is on the first semiconductor layer 236a, and the first gate electrode 255a is on the first gate insulating layer 222. The first gate electrode 255a overlaps the first channel region 234a of the first semiconductor layer 236a. The first gate electrode 255a and the first semiconductor layer 236a may form a first transistor T 1 .

[0101] The second gate insulating layer 223 is on the first gate electrode 255a. The second gate electrode 265 and the barrier layer 260 are on the second gate insulating layer 223. The second gate electrode 265 overlaps the first gate electrode 255a and the first channel region 234a of the first semiconductor layer 236a along the vertical direction DV. Along the vertical direction DV, the first gate electrode 255a and the second gate electrode 265 overlap and are separated by the second gate insulating layer 223, thereby forming a storage capacitor.

[0102] The barrier layer 260 is in the same layer as the second gate electrode 265, for example, directly on the second gate insulating layer 223, but since the first semiconductor layer 236a is between the second gate electrode 265 and the substrate 210, the barrier layer 260 can be closer to the substrate 210 in the vertical direction DV. The barrier layer 260 is electrically connected to the driving voltage line 272 through the opening to receive the driving voltage ELVDD. The barrier layer 260 can be formed of a metal having a conductive property or a semiconductor material having a conductive property equivalent to the conductive property.

[0103] The second buffer layer 241 is on the second gate electrode 265, the barrier layer 260 and the second gate insulating layer 223. The second semiconductor layer 236b is on the second buffer layer 241. The second semiconductor layer 236b includes a second channel region 234b, a second source region 233b and a second drain region 235b. The second source region 233b and the second drain region 235b are at respective sides of the second channel region 234b. The second semiconductor layer 236b may be made of an oxide semiconductor.

[0104] The third gate insulating layer 224 is on the second semiconductor layer 236b. The third gate electrode 255b overlapping the second channel region 234b is on the third gate insulating layer 224. The third gate electrode 255b and the second semiconductor layer 236b may form a second transistor T. 2 .

[0105] The barrier layer 260 and the second transistor T 2 The barrier layer 260 may also overlap with the second source region 233b and the second drain region 235b at respective sides of the second channel region 234b, for example, may overlap with the entire second semiconductor layer 236b. In addition, the barrier layer 260 may not overlap with the first transistor T 1 overlaps with the first channel region 234a.

[0106] The first transistor T is described 1 The first semiconductor layer 236a is made of polysilicon and the second transistor T 2 The second semiconductor layer 236b is made of an oxide semiconductor, but the first semiconductor layer 236a may be made of an oxide semiconductor and the second semiconductor layer 236b may be made of polysilicon. Alternatively, both the first semiconductor layer 236a and the second semiconductor layer 236b may be made of the same material, for example, polysilicon or an oxide semiconductor.

[0107] The interlayer insulating layer 242 is on the third gate electrode 255 b and the third gate insulating layer 224 . The first source electrode 261 a , the first drain electrode 262 a , the second source electrode 261 b , the second drain electrode 262 b , and the driving voltage line 272 are on the interlayer insulating layer 242 .

[0108] The first source electrode 261a and the first drain electrode 262a are respectively connected to the first source region 233a and the first drain region 235a of the first semiconductor layer 236a through openings in the second buffer layer 241, the first to third gate insulating layers 222 to 224, and the interlayer insulating layer 242.

[0109] Furthermore, the second source electrode 261 b and the second drain electrode 262 b are connected to the second source region 233 b and the second drain region 235 b of the second semiconductor layer 236 b through the openings in the interlayer insulating layer 242 and the third gate insulating layer 224 , respectively.

[0110] Finally, the driving voltage line 272 is connected to the blocking layer 260 through the openings in the second buffer layer 241 , the interlayer insulating layer 242 , and the third gate insulating layer 224 .

[0111] By way of summary and review, embodiments herein may provide an organic light emitting diode display having increased design freedom, high resolution, and improved display quality.

[0112] Example embodiments have been disclosed herein, and although specific terms are employed, the specific terms are used and interpreted only in a general and descriptive sense, and not for purposes of limitation. In some cases, it will be apparent to one of ordinary skill in the art from the time of filing this application that, unless otherwise expressly indicated, features, characteristics, and / or elements described in conjunction with a specific embodiment may be used alone or in combination with features, characteristics, and / or elements described in conjunction with other embodiments. Therefore, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the spirit and scope of the invention set forth in this disclosure.

Claims

1. An organic light emitting diode display, wherein: The organic light emitting diode display comprises: substrate; a first buffer layer, the first buffer layer being on the substrate; a first semiconductor layer, wherein the first semiconductor layer is on the first buffer layer; a first gate insulating layer, the first gate insulating layer being on the first semiconductor layer; a first gate electrode and a barrier layer, wherein the first gate electrode and the barrier layer are on the first gate insulating layer; a second buffer layer, the second buffer layer being on the first gate electrode; a second semiconductor layer, wherein the second semiconductor layer is on the second buffer layer; a second gate insulating layer, wherein the second gate insulating layer is on the second semiconductor layer; a second gate electrode, the second gate electrode being on the second gate insulating layer; and An electrode directly contacts top surfaces of the first semiconductor layer and the second gate insulating layer.

2. The organic light emitting diode display according to claim 1, wherein: The barrier layer overlaps the second semiconductor layer, and The blocking layer is on the same layer as the first gate electrode.

3. The organic light emitting diode display according to claim 2, wherein: The organic light emitting diode display further comprises: a driving voltage line, the driving voltage line transmitting a driving voltage, wherein the blocking layer is connected to the driving voltage line to receive the driving voltage, Wherein, the first semiconductor layer comprises: a first channel region, the first channel region overlapping the first gate electrode; and a first source region and a first drain region, wherein the first source region and the first drain region are located in the At respective sides of the first channel region, Wherein, the second semiconductor layer comprises: a second channel region, the second channel region overlapping the second gate electrode; and a second source region and a second drain region, wherein the second source region and the second drain region are located in the at respective sides of the second channel region, and Wherein, the barrier layer overlaps with the second channel region.

4. The organic light emitting diode display according to claim 3, wherein: The electrode directly contacting the top surfaces of the first semiconductor layer and the second gate insulating layer includes a first source electrode and a first drain electrode, the first source electrode and the first drain electrode are connected to the first source region and the first drain region, respectively, and the organic light emitting diode display further includes: a third gate insulating layer, the third gate insulating layer being on the second gate electrode; a second storage electrode on the third gate insulating layer and overlapping the first storage electrode of the second gate electrode; and a second source electrode and a second drain electrode, the second source electrode and the second drain electrode being connected to the second source region and the second drain region, respectively, wherein the second storage electrode is connected to the second drain electrode.

5. The organic light emitting diode display according to claim 3, wherein: The electrode directly contacting the top surfaces of the first semiconductor layer and the second gate insulating layer includes a first source electrode and a first drain electrode, the first source electrode and the first drain electrode are connected to the first source region and the first drain region, respectively, and the organic light emitting diode display further includes: a third gate insulating layer, the third gate insulating layer being on the second gate electrode; a second storage electrode on the third gate insulating layer and overlapping the first storage electrode of the second gate electrode; and a second source electrode and a second drain electrode, the second source electrode and the second drain electrode being connected to the second source region and the second drain region, respectively, wherein the second storage electrode is connected to the driving voltage line.

6. The organic light emitting diode display according to claim 5, wherein: One of the first semiconductor layer and the second semiconductor layer is an oxide semiconductor and the other includes polycrystalline silicon.

7. An organic light emitting diode display, wherein: The organic light emitting diode display comprises: substrate; a first transistor, the first transistor being on the substrate; a second transistor, the second transistor being on the first transistor; and a blocking layer, the blocking layer being below the second transistor, Wherein, the first transistor comprises: a first semiconductor layer, the first semiconductor layer being on the substrate; and a first gate electrode, the first gate electrode being on the first semiconductor layer, wherein the barrier layer is on a layer covering the first semiconductor layer, Wherein, the second transistor comprises: a second semiconductor layer on the barrier layer; and a second gate electrode, the second gate electrode being on the second semiconductor layer, Wherein, the organic light emitting diode display further comprises: a first gate insulating layer, the first gate insulating layer being between the first semiconductor layer and the first gate electrode; a second gate insulating layer between the second semiconductor layer and the second gate electrode; and An electrode directly contacts top surfaces of the first semiconductor layer and the second gate insulating layer.

8. The organic light emitting diode display according to claim 7, wherein: The organic light emitting diode display further comprises: a buffer layer, the buffer layer being between the first transistor and the second transistor, Wherein, the second semiconductor layer comprises: a channel region overlapping the second gate electrode; and a source region and a drain region, the source region and the drain region being at respective sides of the channel region, Wherein, the barrier layer overlaps with the channel region.

9. The organic light emitting diode display according to claim 8, wherein: The organic light emitting diode display further comprises: a driving voltage line, the driving voltage line transmitting a driving voltage, wherein the barrier layer is connected to the driving voltage line to receive the driving voltage, and Wherein, the blocking layer and the first gate electrode are on the same layer.

10. The organic light emitting diode display according to claim 8, wherein: The organic light emitting diode display further comprises: a driving voltage line, the driving voltage line transmitting a driving voltage, in: The barrier layer is connected to the driving voltage line to receive the driving voltage, the first transistor includes a third gate electrode on and overlapping the first gate electrode, The blocking layer is on the same layer as the third gate electrode.

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