CN1578550A - Actively Driven Organic Electroluminescence Display Structure - Google Patents

Abstract

An active matrix organic electroluminescent display structure with stable luminance. The active-drive organic electroluminescent display comprises a Thin Film Transistor (TFT) structure and an organic light-emitting diode (OLED) structure, and the invention reduces the leakage current of the TFT by improving the protective layer structure of the TFT, so that the brightness of the organic light-emitting diode (OLED) is maintained stable.

Description

Actively Driven Organic Electroluminescence Display Structure

technical field

The present invention relates to an organic electroluminescence display structure, in particular to an improved TFT protective layer structure to reduce the leakage current of the thin film transistor and maintain a display structure that actively drives the luminance of an organic light emitting diode (OLED).

Background of the invention

Organic Electroluminescence Display (Organic Electroluminesence Display), also known as Organic Light Emitting Diode (OLED) display, because of its high brightness, fast screen response, thin and short, full color, no viewing angle difference, no It needs the advantages of liquid crystal display backlight and saves light source and power consumption, so it can take the lead in replacing the twisted nematic (Twist Nematic; TN) and super twisted nematic (Super Twist Nematic; STN) liquid crystal display market, and further replace Small-sized thin film transistor liquid crystal display (TFT-LCD) has become a display material commonly used in a new generation of portable information products, mobile phones, personal digital processors and portable computers.

Organic light-emitting diode displays can be divided into passive (Passive Matrix, PMOLED) and active (Active Matrix, AMOLED) according to the driving method. The so-called active driving OLED (AMOLED) is to use thin film transistor (Thin Film Transistor, TFT) with capacitor to store signal to control the brightness grayscale performance of OLED. When the scan line is scanned, the pixels can still maintain the original brightness; as for the passive drive, only the pixels selected by the scan line will be lit. Therefore, in the active driving mode, the OLED does not need to be driven to a very high brightness, so it can achieve a long service life and meet the requirements of high resolution.

1 is a schematic cross-sectional view of the structure of an AMOLED. A thin film transistor (TFT) 1 of an AMOLED includes a gate metal 11, a dielectric insulating layer 12, a source/drain metal 13, an amorphous silicon layer 14, doped amorphous Crystalline silicon 15 and protective layer 16 . The AMOLED organic light emitting diode 2 includes an indium tin oxide (ITO) electrode 21 , an organic light emitting layer 22 and a cathode electrode 23 , and the ITO transparent electrode 21 is connected to the source/drain metal 13 . Since the AMOLED is a current-driven device, a constant current must be provided to maintain consistent brightness of the OLED. As shown in Figure 1, the current (as indicated by the arrow) flows through the source/drain metal 13 of the TFT 1, flows through the ITO layer 21, and then flows into the organic light-emitting layer 22 and the cathode electrode 23, at this time the OLED emits light. However, the inventors found that in the current technology, when a constant current is applied, the brightness of the OLED still declines (decay).

Therefore, it is urgent to find out the reason why the luminance of the existing AMOLED is unstable and to improve its structure, so as to produce an AMOLED that maintains the luminance of the OLED.

Contents of the invention

The inventors of the present invention have discovered the reason why the luminance of AMOLED is unstable. When the thin film transistor (TFT) 1 of AMOLED is in operation, a voltage will be applied to its gate metal 11, so there will be a strong electric field E between the gate metal 11 and the cathode electrode 23, as shown in FIG. 2 , and the protective layer 16 of the TFT 1 is made of a dielectric material such as SiNx. This dielectric material is under a fixed voltage, and the change diagram of the current and time flowing through the dielectric material is shown in FIG. 3 . When the ability of the protective layer 16 to block current is poor, the protective layer 16 will collapse after a certain period of time, and a large amount of leakage current will flow through the protective layer 16, as shown by arrow B in FIG. 4 . Therefore, under a certain current supply, the current flowing through the ITO layer and injected into the organic light-emitting layer 22 is greatly reduced, resulting in a decrease in the brightness of the OLED.

Therefore, to reduce the occurrence of this leakage current, so that the provided constant current can effectively pass through the OLED instead of being lost through other paths, so as to maintain the luminous brightness of the OLED and increase the service life (lifetime) of the AMOLED component, the present invention improves The protective layer structure of TFT is used to achieve the above-mentioned purpose.

The main purpose of the present invention is to provide a structure capable of maintaining the luminance of an actively driven organic light emitting diode (AMOLED). By improving the structure of the protective layer of the TFT, the leakage current of the TFT is reduced, and the luminance of the organic light emitting diode (OLED) is kept stable.

The present invention provides an active driving organic electroluminescent display structure, including:

A thin film transistor structure comprising a gate metal, a dielectric insulating layer, a source/drain metal and a protective layer, the gate metal is arranged on a substrate, the dielectric insulating layer covers the gate metal and on the substrate, the source/drain metal is disposed on the dielectric insulating layer and above the gate metal, and the protective layer covers the source/drain metal; and

An organic light-emitting diode structure, which includes an anode electrode, an organic light-emitting layer and a cathode electrode, the anode electrode is connected to the source/drain metal, the organic light-emitting layer is formed on the anode electrode, and the cathode electrode is formed on the organic light-emitting layer;

The protective layer of the thin film transistor structure is a multi-layer structure.

Each layer of the multilayer structure of the protection layer is composed of different dielectric materials.

The present invention provides an active driving organic electroluminescent display structure, including:

A thin film transistor structure comprising a gate metal, a dielectric insulating layer, a source/drain metal and a protective layer, the gate metal is arranged on a substrate, the dielectric insulating layer covers the gate metal and on the substrate, the source/drain metal is disposed on the dielectric insulating layer and above the gate metal, and the protective layer covers the source/drain metal; and

An organic light-emitting diode structure, which includes an anode electrode, an organic light-emitting layer and a cathode electrode, the anode electrode is connected to the source/drain metal, the organic light-emitting layer is formed on the anode electrode, and the cathode electrode is formed on the organic light-emitting layer;

The protective layer of the thin film transistor structure is subjected to thermal oxidation treatment.

The protective layer is SiNx dielectric material, the surface of which is thermally oxidized to form SiON.

The present invention provides an active driving organic electroluminescent display structure, including:

A thin film transistor structure comprising a gate metal, a dielectric insulating layer, a source/drain metal and a protective layer, the gate metal is arranged on a substrate, the dielectric insulating layer covers the gate metal and on the substrate, the source/drain metal is disposed on the dielectric insulating layer and above the gate metal, and the protective layer covers the source/drain metal; and

An organic light-emitting diode structure, which includes an anode electrode, an organic light-emitting layer and a cathode electrode, the anode electrode is connected to the source/drain metal, the organic light-emitting layer is formed on the anode electrode, and the cathode electrode is formed on the organic light-emitting layer;

The protective layer is made of high dielectric strength material.

Description of drawings

1 is a schematic cross-sectional view of a structure of an existing actively driven organic electroluminescence display (AMOLED);

Fig. 2 shows a strong electric field between the gate metal and the cathode electrode of the AMOLED of Fig. 1;

Fig. 3 is a dielectric material under a fixed voltage, the change diagram of the current and time flowing through the dielectric material;

Figure 4 shows that the AMOLED in Figure 1 has a large amount of leakage current lost through the protective layer, as indicated by arrow B;

Fig. 5 is the first embodiment of the protective layer structure of the TFT of the present invention;

Fig. 6 is the second embodiment of the protective layer structure of the TFT of the present invention; and

FIG. 7 is a third embodiment of the protective layer structure of the TFT of the present invention.

Explanation of drawing number:

Thin Film Transistor (TFT) -----1 Organic Light Emitting Diode -----2

Gate metal ------------11 Dielectric insulation layer ---------12

Source/Drain Metal -----------13 Amorphous Silicon Layer -----------14

Indium tin oxide electrode (ITO) ---21 Doped amorphous silicon ---------15

Protective layer ---------------16 Organic light-emitting layer ---------22

Cathode electrode-------------23 Electric field---------------E

Arrow -----------------B Protective Layer-------------26, 36, 46

Two-layer structure ------------261, 262 Protective layer surface ---------36'

Detailed ways

Fig. 5 shows a first embodiment of the structure of the protective layer of the TFT of the present invention. A multi-layer protective layer 26 is fabricated to increase the anti-leakage current capability of the protective layer 26 . For example, SiNx with a thickness of 3000 angstroms can be plated in multiple layers (more than two layers), or SiNx can be plated with other dielectric materials alternately. In FIG. 5 , the protection layer 26 is composed of two layers 261 , 262 . By increasing the thickness of the dielectric layer of the protection layer and increasing the interface of the dielectric film due to multi-layer plating, the anti-leakage current capability of the protection layer 26 can be double enhanced.

In addition, the present invention provides another preferred embodiment, performing thermal oxidation treatment on the surface of the protection layer to increase the anti-leakage current capability of the protection layer. Fig. 6 shows the second embodiment of the protective layer structure of the TFT of the present invention, for example, after the SiNx protective layer 36 is plated, the SiNx is subjected to thermal oxidation treatment, so that the surface 36' of the protective layer 36 forms SiON, so The anti-leakage current capability of the protection layer 36 can also be increased.

Furthermore, the present invention provides another preferred embodiment. FIG. 7 shows a third embodiment of the protective layer structure of the TFT of the present invention, using a material with high dielectric strength, such as SiO ₂ , as the material for the protective layer, To increase the anti-leakage current capability of the protection layer 46 .

The above described the present invention in detail using the preferred embodiments, rather than limiting the scope of the present invention, and those who are familiar with this type of technology can understand that appropriate and slight changes and adjustments on the basis of the present invention will still not affect the scope of the present invention. Without the gist of the present invention, the protection scope of the present invention shall be determined by the claims.

Claims (6)

1. active driving organic electro-luminescent display structure comprises:

One thin-film transistor structure, it comprises a gate metal, a dielectric insulation layer, one source/drain metal and a protective layer, this gate metal is arranged on the substrate, this dielectric insulation layer covers on this gate metal and this substrate, this source/drain metal is arranged on this dielectric insulation layer, and be positioned at the top of this gate metal, this protective layer covers on this source/drain metal; And

One organic LED structure, it comprises an anode electrode, an organic luminous layer and a cathode electrode, this anode electrode is connected with this source/drain metal, and this organic luminous layer is formed on this anode electrode, and this cathode electrode is formed on this organic luminous layer;

It is characterized in that: the protective layer of described thin-film transistor structure is a sandwich construction.

2. active driving organic electro-luminescent display structure according to claim 1, each is made of each layer of the sandwich construction of described protective layer different dielectric materials.

3. active driving organic electro-luminescent display structure comprises:

One thin-film transistor structure, it comprises a gate metal, a dielectric insulation layer, one source/drain metal and a protective layer, this gate metal is arranged on the substrate, this dielectric insulation layer covers on this gate metal and this substrate, this source/drain metal is arranged on this dielectric insulation layer, and be positioned at the top of this gate metal, this protective layer covers on this source/drain metal; And

One organic LED structure, it comprises an anode electrode, an organic luminous layer and a cathode electrode, this anode electrode is connected with this source/drain metal, and this organic luminous layer is formed on this anode electrode, and this cathode electrode is formed on this organic luminous layer;

It is characterized in that: the protective layer of described thin-film transistor structure is through thermal oxidation.

4. active driving organic electro-luminescent display structure according to claim 3, described protective layer is the SiNx dielectric material, its surface forms SiON through after the thermal oxidation.

5. active driving organic electro-luminescent display structure comprises:

One thin-film transistor structure, it comprises a gate metal, a dielectric insulation layer, one source/drain metal and a protective layer, this gate metal is arranged on the substrate, this dielectric insulation layer covers on this gate metal and this substrate, this source/drain metal is arranged on this dielectric insulation layer, and be positioned at the top of this gate metal, this protective layer covers on this source/drain metal; And

One organic LED structure, it comprises an anode electrode, an organic luminous layer and a cathode electrode, this anode electrode is connected with this source/drain metal, and this organic luminous layer is formed on this anode electrode, and this cathode electrode is formed on this organic luminous layer;

It is characterized in that: described protective layer is made of high dielectric strength material.

6. according to the described active driving organic electro-luminescent display structure of claim 5, described protective layer is SiO ₂Dielectric material constitutes.

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