Capacitor structure for organic light-emitting display apparatus and manufacturing method thereof

An organic light-emitting display apparatus includes: a display unit including an organic light-emitting element, a driving transistor electrically connected to the organic light-emitting element, and a capacitor; and a pad unit connected to the display unit, the capacitor including: a first conductive layer disposed on a substrate; a second conductive layer interposed between the substrate facing a first surface of the first conductive layer; and a third conductive layer disposed facing a second surface of the first conductive layer opposing the first surface of the first conductive layer, the third conductive layer being electrically connected to the second conductive layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from and the benefit of Korean Patent Application No. 10-2018-0094621, filed on Aug. 13, 2018, which is hereby incorporated by reference for all purposes as if fully set forth herein.

BACKGROUND

Field

Exemplary embodiments/implementations of the invention relate generally to an organic light-emitting display apparatus and a method of manufacturing the same, and more specifically, to an organic light-emitting display apparatus having an improved structure and a method of manufacturing the organic light-emitting display apparatus.

Discussion of the Background

An organic light-emitting display apparatus typically includes, in each pixel, a thin film transistor, a capacitor, and an organic light-emitting element connected to the thin film transistor and the capacitor, and a desired image is realized as the organic light-emitting element emits light by receiving an appropriate driving signal from the thin film transistor.

Here, a sufficient charge capacity of the capacitor may be required to stably realize images by using the organic light-emitting display apparatus. That is, the capacitor having sufficient charge capacity may maintain a stable voltage of the thin film transistor without fluctuations during light emission of the organic light-emitting element to produce natural images.

Accordingly, a capacitor having a relatively large charge capacity generally requires increased size in planar area. However, recent increases in resolution of organic light-emitting display apparatuses has gradually decreased a planar space allocated to each pixel, and therefore, the planar area for the capacitor is also limited.

SUMMARY

Devices constructed and methods according to exemplary implementations of the invention are capable of providing an organic light-emitting display apparatus with a capacitor having increased charge capacity without increasing a planar area taken up by the capacitor, and a method of manufacturing the organic light-emitting display apparatus.

According to one or more embodiments of the invention, an organic light-emitting display apparatus includes: a display unit including an organic light-emitting element, a driving transistor electrically connected to the organic light-emitting element, and a capacitor; and a pad unit connected to the display unit, the capacitor including: a first conductive layer disposed on a substrate; a second conductive layer interposed between the substrate facing a first surface of the first conductive layer; and a third conductive layer disposed facing a second surface of the first conductive layer opposing the first surface of the first conductive layer, the third conductive layer being electrically connected to the second conductive layer.

The driving transistor may include an active layer disposed on the substrate, a gate electrode disposed on the active layer, and a source electrode and a drain electrode disposed on the gate electrode, the source electrode and the drain electrode being connected to the active layer.

The second conductive layer may interposed between below the active layer of the driving transistor and the substrate.

The first conductive layer may be disposed on a same layer as the gate electrode.

The third conductive layer may be disposed on a same layer as the source electrode and the drain electrode.

The second conductive layer may include a light-shielding layer to block light from entering or exiting the substrate.

The second conductive layer may completely cover a planar area of the first conductive layer.

The organic light-emitting display apparatus may further include a fourth conductive layer disposed facing the third conductive layer on the opposite side of the first conductive layer.

The pad unit may include a metal layer disposed on a same layer as the source electrode and the drain electrode and an indium-tin-oxide (ITO) layer on the metal layer, the fourth conductive layer may be disposed on a same layer, and the fourth conductive layer may include the same material as the ITO layer.

The fourth conductive layer may be electrically connected to the first conductive layer.

According to one or more embodiments of the invention, a method of manufacturing an organic light-emitting display apparatus, includes: forming a display unit including an organic light-emitting element, a driving transistor, and a capacitor on a substrate; and forming a pad unit connected to the display unit, wherein the forming of the capacitor includes: forming a first conductive layer on the substrate; forming a second conductive layer interposed between the substrate facing a first surface of the first conductive layer, the second conductive layer facing a first surface of the first conductive layer; and forming a third conductive layer facing a second surface of the first conductive layer opposing the first surface, the third conductive layer being electrically connected to the second conductive layer.

The forming of the driving transistor may include: forming an active layer on the substrate; forming a gate electrode on the active layer; and forming a source electrode and a drain electrode on the gate electrode, the source electrode and the drain electrode being connected to the active layer.

The second conductive layer may interposed between the active layer of the driving transistor and the substrate.

The first conductive layer may be formed on a same layer as the gate electrode.

The third conductive layer may be formed on a same layer as the source electrode and the drain electrode.

The second conductive layer may include a light-shielding layer to block light from entering or exiting the substrate.

The second conductive layer may completely cover a planar area of the first conductive layer.

The method may further include forming a fourth conductive layer facing the third conductive layer on the opposite side of the first conductive layer.

The forming of the pad unit may include forming a metal layer on a same layer as the source electrode and the drain electrode; and forming an indium-tin-oxide (ITO) layer on the metal layer, wherein the fourth conductive layer is disposed on a same layer as the ITO layer and formed of the same material as the ITO layer.

The fourth conductive layer may be electrically connected to the first conductive layer.

DETAILED DESCRIPTION

FIG. 1is a plan view of an organic light-emitting display apparatus10according to an exemplary embodiment. As illustrated inFIG. 1, an organic light-emitting display apparatus10according to the current exemplary embodiment includes, a substrate101, and a display unit100and a pad unit102disposed on the substrate101. The display unit100is configured to realize an image, and the pad unit102is connected to the display unit100to which a flexible circuit board is connected.

A plurality of pixels PX are arranged on the display unit100, and each pixel PX approximately has a planar structure as illustrated in an enlarged view inFIG. 2.

FIG. 2is an enlarged plan view of a pixel PX illustrated inFIG. 1. Referring toFIG. 2, a first base metal layer131and a second base metal layer132are disposed on the substrate101. The first base metal layer131is arranged in an area of a capacitor130, and the second base metal layer132is arranged in an area of a driving transistor110, and both the first and second base metal layers131and132perform a light-shielding function to block light from entering or exiting through the substrate101. The first base metal layer131and the second base metal layer132also provide electrical characteristics in connection with a first conductive layer133and a third conductive layer134which will be described later. Hereinafter, the first base metal layer131and the second base metal layer132are collectively referred to as second conductive layers13.

A driving transistor110and a switching transistor120are formed on the second conductive layers13, respectively. An organic light-emitting element140is formed on the driving transistor110and the capacitor130, and the organic light-emitting element140is configured to generate light emission. Particularly, the region enclosed by the dotted line represents an area of the light-emitting element140.

A cross-sectional structure of the pixel PX will now be described with reference toFIG. 3.FIG. 3is a cross-sectional view of the pixel PX ofFIG. 2taken along a sectional line III-III.

As illustrated inFIG. 3, the driving transistor110, the switching transistor120, and the capacitor130are provided on the substrate101, and the organic light-emitting element140connected to the driving transistor110is provided thereon.

First, the driving transistor110and the switching transistor120will be described, in which active layers111and121are formed on a buffer layer101a, and gate electrodes112and122face the first and second active layers111and121with a gate insulating layer101binterposed therebetween, and source electrodes113and123and drain electrodes114and124formed on the gate electrodes112and122with an interlayer insulating layer101cinterposed therebetween are connected to two ends of the active layers111and121doped with an N-type or P-type impurity. Hereinafter, the source electrodes113and123and the drain electrodes114and124will be referred together as source/drain electrodes113,114,123, and124. The active layers111and121may be formed of an oxide semiconductor and may include, for example, an oxide of a material selected from Group 12, 13, or 14 metal elements such as zinc (Zn), indium (In), gallium (Ga), tin (Sn), cadmium (Cd), germanium (Ge), and a combination thereof. For example, the active layers111and121formed of an oxide semiconductor may include G-I-Z-O[(In2O3)a(Ga2O3)b(ZnO)c] (a, b, and c are respectively real numbers satisfying the condition of a≥0, b≥0, and c>0).

The driving transistor110and the switching transistor120have a nearly identical stack structure, except that the driving transistor110, which is relatively close to the organic light-emitting element140, further includes the second base metal layer132from among the second conductive layers13in a lower portion of the driving transistor110. The second base metal layer132has a light-shielding function to block light from entering or exiting from the substrate101as described above to thereby prevent or reduce intermixing of external light with the light generated by the organic light-emitting element140. The second base metal layer132is also connected to the source electrode113to thereby stabilize saturation characteristics of the source/drain electrodes113and114at the same time.

The organic light-emitting element140includes the pixel electrode141connected to the source electrode113and the drain electrode114of the driving transistor110with an indium tin oxide (ITO) layer115interposed therebetween, an opposite electrode143facing the pixel electrode141, and an emissive layer142between the pixel electrode141and the opposite electrode143. Accordingly, when appropriate voltage conditions are created between the opposite electrode143and the pixel electrode141as a voltage is applied to the pixel electrode141from the driving transistor110, light emission takes place in the emissive layer142. The emissive layer142may include all of a hole injection transport layer, an organic emissive layer, an electron injection transport layer or the like or selectively some of these layers.

Although not illustrated in the drawings, a protective layer may be further formed on the opposite electrode143.

Reference numerals101d,101e, and101fdenote insulating layers, which are respectively a passivation layer, a via layer, and a pixel defining layer.

The pad unit102in an outer portion of the display unit100includes a metal layer102aformed on a same layer and of the same material as the source/drain electrodes113,114,123, and124and an ITO layer102bon the metal layer102a, and a flexible circuit board is connected to the ITO layer102bthat is exposed to the outside.

Next, a structure of the capacitor130according to the current exemplary embodiment will be described.

The capacitor130includes a first conductive layer133, second conductive layers13, and a third conductive layer134that face each other with insulating layers interposed therebetween.

The first conductive layer133is formed on a same layer as the gate electrodes112and122. Also, the first conductive layer133is formed of the same material as the gate electrodes112and122.

The second conductive layers13face the first conductive layer133with the buffer layer101aand the gate insulating layer101binterposed therebetween. The first base metal layer131among the second conductive layers13corresponds to the area of the capacitor130.

The third conductive layer134faces the first conductive layer133with the interlayer insulating layer101cinterposed therebetween and is formed on a same layer as the source/drain electrodes113,114,123, and124. Also, third conductive layer134is formed of the same material as the source and drain electrodes113,114,123, and124.

According to this structure, a first capacitor C1is formed between the first conductive layer133and the first base metal layer131of the second conductive layers13, and a second capacitor C2is formed between the first conductive layer133and the third conductive layer134. That is, two capacitors, the first and second capacitors C1and C2, are formed in a same area on a plane.

FIG. 4is a circuit diagram of an organic light-emitting element140, a transistor110, and a capacitor130illustrated inFIG. 3. The structure of the capacitors described above is expressed as a circuit diagram as illustrated inFIG. 4in which the two capacitors, the first and second capacitors C1and C2, connected in parallel to each other provide a stable voltage to the driving transistor110. That is, a capacity of the capacitor130may be increased by providing a double layer structure of the two capacitors, that is, the first and second capacitors C1and C2without increasing space occupancy thereof on a plane. Thus, according to this configuration, an organic light-emitting display apparatus in which a charge capacity is increased without increasing an area on a plane taken up by capacitors may be provided.

The organic light-emitting display apparatus having the above-described configuration may be manufactured as follows.

First, a first base metal layer131and a second base metal layer132, which will be formed as second conductive layers13, are formed on a substrate101.

Then a buffer layer101ais formed thereon, and then active layers111and121of a driving transistor110and a switching transistor120are formed on the buffer layer101a. When viewed from the substrate101, the active layer111of the driving transistor110is completely covered by the second base metal layer132provided in a lower portion of the driving transistor110.

Next, a gate insulating layer101bis formed on the active layers111and121and the buffer layer101a, and gate electrodes112and122are formed on the gate insulating layer101b, and a first conductive layer133is formed in an area of the capacitor130by using the same material as that of the gate electrodes112and122. When viewed from the substrate101, the first conductive layer133is completely covered by the first base metal layer131.

Next, an interlayer insulating layer101cis formed, and source/drain electrodes113,114,123, and124of the driving transistor110and the switching transistor120, a third conductive layer134of the capacitor130, and a metal layer102aof the pad unit102are formed on the interlayer insulating layer101cby using the same material as each other. Here, a contact hole penetrates through the interlayer insulating layer101cand the buffer layer101ato connect the source/drain electrodes113,114,123, and124and the active layers111and121to each other, the source electrode113and the second base metal layer132to each other, and the second conductive layers13and the third conductive layer134to each other.

Then a passivation layer101d, ITO layers115and102b, and a via layer101eare formed, and then a pixel electrode141, a pixel defining layer101f, an emissive layer142, and an opposite electrode143of the organic light-emitting element140are sequentially formed.

Accordingly, as illustrated inFIG. 3, the capacitor130having a high capacity may be realized within a relatively small planar area, and an organic light-emitting display apparatus including the capacitor130may have high light-shielding effects and a high resolution.

Next,FIG. 5is a cross-sectional view of an organic light-emitting display apparatus according to another exemplary embodiment.

The driving transistor110, the switching transistor120, the organic light-emitting element140, and the pad unit102are identical to those described above with reference toFIG. 3, and therefore, the redundant descriptions are omitted.

Here, the capacitor130includes three capacitors C1, C2, and C3. That is, a fourth conductive layer135formed of the same material as the ITO layer102bof the pad unit102is formed on the same layer as the ITO layer102bfacing the third conductive layer134.

Accordingly, a first capacitor C1is formed between the first conductive layer133and the first base metal layer131of the second conductive layers13, a second capacitor C2is formed between the first conductive layer133and the third conductive layer134, and a third capacitor C3is formed between the third conductive layer134and the fourth conductive layer135. That is, three capacitors C1, C2, and C3are formed in a same space on a plane.

FIG. 6is a circuit diagram of an organic light-emitting element140, a transistor110, and a capacitor130illustrated inFIG. 5. The structure of the capacitors described above is expressed as a circuit diagram as illustrated inFIG. 6in which the three capacitors, the first through third capacitors C1, C2, and C3connected in parallel to each other, provide a stable voltage to the driving transistor110. That is, a capacity of the capacitor130may be increased by providing a multi-layer structure of the three capacitors, that is, the first through third capacitors C1, C2, and C3without increasing space occupancy thereof on a plane. Thus, according to this configuration, an organic light-emitting display apparatus having a sufficient charge capacity obtained without increasing an area on a plane taken up by capacitors may be provided.

The manufacturing process of the above organic light-emitting display apparatus is also identical to the exemplary embodiment ofFIG. 3, except that the fourth conductive layer135is additionally formed and connected to the first conductive layer133when forming the ITO layers102band115respectively on the metal layer102aof the pad unit102and under the pixel electrode141.

As described above, according to the organic light-emitting display apparatus of the current exemplary embodiment, a charge capacity of a capacitor may be sufficiently increased without increasing the planar area taken up by the capacitor, and thus, an organic light-emitting display apparatus may have high light-shielding effects and a high resolution.