KR100793314B1 - Multi-layer anode and top emission organic light emitting diode including the multi-layer anode - Google Patents

Abstract

A multi-layer anode and a top emission organic light emitting diode including the multi-layer anode are provided to manufacture a conductive metal thin film as an anode electrode of the top emission organic light emitting diode. A top emission organic light emitting diode(10) includes a substrate(11), an anode(12), a hole injection layer(13a), a hole transporting layer(13b), a light emitting layer(14), an electron transporting layer(15a), an electron injection layer(15b), a cathode, a buffer layer(16), and a passivation layer(17). The anode is formed on the substrate. The hole transporting layer and the hole injection layer are formed on the anode. The cathode is formed on the electron injection layer. The buffer layer is formed on the cathode. The anode has a multi-layer structure. The anode includes a lower conduction layer(12a), a reflective conduction layer(12b), and an upper conductive layer(12c). The lower conductive layer is in direct contact with the substrate. The reflective layer is formed on the lower conduction layer. The upper conduction layer is formed on the reflective conduction layer.

Description

Multi-layer anode and top emission organic light emitting diode including the multi-layer anode}

1 is a schematic side cross-sectional view of an organic light emitting device including an anode electrode having a multilayer structure according to the present invention.

2 is a graph illustrating I-V-L characteristics of an organic light emitting diode according to the present invention.

3 is a graph of efficiency characteristics of the organic light emitting device according to the present invention.

4 is an emission spectrum of the organic light emitting device according to the present invention.

5 is a light emission image of the organic light emitting device according to the present invention.

<Description of Symbols for Main Parts of Drawings>

10: upward-emitting organic light emitting element 11: substrate

12: anode 12a: lower conductive layer

12b: reflective conductive layer 12c: upper conductive layer

13a: hole injection layer 13b: hole transport layer

14: light emitting layer 15a: electron transport layer

15b: electron injection layer 16: buffer layer

17: passivation layer

The present invention relates to an anode electrode having a multilayer structure and an upward light emitting organic light emitting device including the anode electrode, and more specifically, an upper conductive layer and a lower conductive layer formed of a conductive metal thin film on the upper and lower portions of the reflective conductive layer. It relates to an anode electrode having a multi-layer structure comprising a and an up-emitting organic light emitting device comprising the anode.

In general, an organic light emitting device is a light emitting device using an organic material that emits light when a current flows, and generally includes a pair of electrodes formed of an anode and a cathode, and a hole injection layer between the electrodes. , A hole transport layer, an electron injection layer, an electron transport layer and a light emitting layer. The organic light emitting device having such a structure generates light while combining holes and electrons injected from the anode and the cathode into the light emitting layer. The organic light emitting device may be classified into an upward light emitting organic light emitting device that emits light from the light emitting layer to an upper portion of the substrate, and a downward light emitting organic light emitting device emitting to the bottom of the substrate.

Among the various organic light emitting devices as described above, the up-emitting organic light emitting device currently being developed has various advantages such as direct light emission, high efficiency, and wide viewing angle. When the transparent conductive film is used for the anode of the organic light emitting element, since the light is not easily transmitted and used as an electrode layer of the upward light emitting organic light emitting element, a reflective conductive metal is mainly used. Accordingly, in order to suppress the decrease in luminous efficiency caused by decreasing the work function of the anode electrode formed of ITO or IZO or ITZO, and to further improve the brightness (luminance) of light generated in the light emitting layer, the reflectance is relatively high. It is proposed to form an anode electrode using metal silver (Ag), silver alloy or the like (Korean Laid-Open Patent Publication No. 10-2006-0037857).

However, silver or silver alloys are generally inferior in water resistance, so that when contacted with water (or water vapor) during the manufacturing process, the electrically ionized metal melts or is transferred. In addition, since silver or silver alloys generally have poor adhesion to other metals or substrates, there is a disadvantage in that productivity is lowered even though they have relatively high reflectance than other metals.

Accordingly, the present invention is an invention derived to solve the above-mentioned conventional problems, an object of the present invention is to form a top and bottom conductive layer by using a conductive metal thin film on the top and bottom of the reflective metal layer, thereby improving the contact force The present invention provides a multi-layered anode electrode capable of increasing productivity and increasing reflectance and an upward-emitting organic light emitting device including the anode electrode.

In addition, an object of the present invention is to improve the work function of the anode electrode, reflectance problems due to oxidation of the reflective conductive layer, problems in the lithography process and the like, and a multi-layered anode electrode and up-emitting organic light-emitting including the anode electrode It is to provide a device.

An anode electrode of a multilayer structure of the present invention configured to achieve the above object is a lower conductive layer formed of a conductive metal thin film on a substrate; A reflective conductive layer formed of a reflective metal thin film on the lower conductive layer; And an upper conductive layer formed of the conductive metal thin film on the reflective conductive layer.

Preferably, the reflective conductive layer uses one of silver, aluminum, silver or an alloy containing at least one element of chromium, copper, manganese, zinc, and neodymium in aluminum. The reflective conductive layer is 2000-5000 mm thick. The upper conductive layer and the lower conductive layer are formed of at least one of Pt, Ti, and Cr. The lower conductive layer has a thickness of 100 to 500 kV. The upper conductive layer is formed of the same material as the lower conductive layer. The upper conductive layer is 10 to 90 kPa thick. The substrate is formed of one of a plastic substrate, a metal thin film, silicon oxide, and a glass substrate.

According to another aspect of the invention, the present invention is an anode having a multi-layer structure including a lower conductive layer, a reflective conductive layer and an upper conductive layer of any one of claims 1 to 8; A hole injection and transport layer formed on the anode; An emission layer formed on the hole injection and transport layer; An electron transport and injection layer formed on the light emitting layer; And a cathode formed on the electron transport and injection layer.

Preferably, the lower conductive layer and the upper conductive layer are formed of the same material. The lower conductive layer and the upper conductive layer are formed of one of Pt, Ti, and Cr. The reflective conductive layer is formed by using one of silver, aluminum, silver, or an alloy containing at least one element of chromium, copper, manganese, zinc, and neodymium in aluminum.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic side cross-sectional view of an organic light emitting device including an anode electrode having a multilayer structure according to the present invention. In the present embodiment, an up-emitting organic light emitting diode is described as an example.

Referring to FIG. 1, the upward emission organic light emitting diode 10 may include a substrate 11, an anode 12 formed on the substrate 11, a hole injection layer and a hole transport layer 13a formed on the anode 12. 13b), light emitting layer 14, electron transport layer and electron injection layer 15a, 15b, cathode 15 formed on electron injection layer 15b, buffer layer 16 and passivation layer formed on cathode 15 (17).

Referring to the above-described components constituting the organic light emitting device 10 in more detail, first, the substrate 10 may use a variety of materials, preferably glass, plastic, foil having transparency Metal thin films such as silicon oxide and the like, and the like.

The anode 12 having a multilayer structure formed on the substrate 10 has a lower conductive layer 12a, which is a conductive metal thin film in direct contact with the substrate 10, and a reflective metal formed on the lower conductive layer 12a. A reflective conductive layer 12b made of a material and an upper conductive layer 12c made of a conductive metal thin film formed on the reflective conductive layer 12b are included.

The lower conductive layer 12a constituting the anode 12 is a component for improving adhesion between the substrate 11 and the reflective conductive layer 12b, and is a physical vapor deposition method (PVD). ), For example, by using one of a sputtering method and a vacuum thermal deposition method. In this case, the lower conductive layer 12a is deposited using one of chromium (Cr), platinum (Pt), and titanium (Ti), and they are not transparent. The thickness of the lower conductive layer 12a is preferably deposited relatively thinner than the thickness of the reflective conductive layer 12b. In the present embodiment, the lower conductive layer 12a is deposited to a thickness of 100 to 500 mW.

The reflective conductive layer 12b is formed of chromium (Ag), aluminum (Al), or silver (Ag) or aluminum (Al) to prevent loss of light emitted from the light emitting layer 14 and improve reflectance. An alloy formed by adding at least one element of Cr, copper (Cu), manganese (Mn), zinc (Zn), and neodymium (Nd) may be used. The reflective conductive layer 12b is also deposited by a physical vapor deposition method. In general, as the thickness of the reflective conductive layer 12b increases, the loss of light emitted from the light emitting layer 14 can be prevented, thereby improving the reflectance. Therefore, in the present embodiment, the thickness of the reflective conductive layer 12b is 2000 to 5000 kPa.

The upper conductive layer 12c is formed on the reflective conductive layer 12b and has a function of protecting the reflective conductive layer 12b, and the reflective conductive layer 12b is formed by contact with oxygen and moisture in the air. Oxidation and corrosion (or corrosion) can be prevented. In addition, the upper conductive layer 12c preferably uses a metal containing a high work function. Since the upper conductive layer 12c is in direct contact with the organic material layer serving as the hole injection layer and the hole transport layers 13a and 13b, the surface roughness is low. do. The upper conductive layer 12c serving as described above may be deposited by one of physical vapor deposition methods using one of chromium (Cr), platinum (Pt), and titanium (Ti), and the upper conductive layer 12c As the thickness increases, the protective effect of the conductive reflective layer 12b is improved. However, since the reflection efficiency of light reflected from the reflective conductive layer 12b can be reduced, it is preferable to form the thickness as thin as several tens of micrometers. In the present embodiment, preferably formed to a thickness of 10 ~ 90Å.

On the other hand, in the case of depositing the conductive layers 12a, 12b, 12c constituting the anode electrode using a physical vapor deposition process, for example, a sputtering process, deposition conditions (deposition pressure, RF power, etc.) in a vacuum state The reflective conductive layer 12c and the conductive layers 12a and 12c are deposited while continuously or stepwise changing. Changing the deposition conditions is to allow the surface of the substrate 11 to be used as an anode to be formed smoothly, that is, to prevent the formation of a hill on the substrate (anode surface). In the present embodiment, the deposition conditions are RF power, deposition pressure, etc., RF power is selectively applied at 100w to 300w, and the deposition pressure is selected in the range of 1 to 5 mTorr. Further, the process proceeds in a continuous process in a vacuum chamber so that no oxide film is formed between the lower conductive layer, the reflective conductive layer, and the upper conductive layer. That is, after depositing the lower conductive layer 12a, the reflective conductive layer 12b is deposited without taking out of the vacuum chamber, the reflective conductive layer is deposited, and then the upper conductive layer 12c is continuously deposited in the vacuum chamber. do. In addition, when depositing the upper, lower and reflective conductive layers, argon, oxygen gas or a mixed gas containing one of them is used as the reaction gas.

In addition, in the present embodiment, since the lower conductive layer 12a and the upper conductive layer 12c are formed of the same metal, when the lithography process is performed, the number of etching processes is reduced, thereby improving productivity. For example, when the lower conductive layer 12a / reflective conductive layer 12b / upper conductive layer 12c is formed of Cr / Al / Cr, the lower and upper conductive layers 12a and 12c may be etched at once. have. In addition, when the lower conductive layer 12a / reflective conductive layer 12b / upper conductive layer 12c is configured as described above, the adhesive force may be applied without a separate adhesive to improve the adhesion between the substrate 11 and the anode 12. Can be improved.

Then, on the anode 12, the hole injection layer and the hole transport layers 13a and 13b, the light emitting layer 14, and the organic material layer including the electron transport layer and the electron injection layers 14a and 14b are sequentially stacked, and the hole injection layer and the hole are sequentially stacked. The transport layers 13a and 13b, the light emitting layer 14, and the electron injection layer and the electron transport layers 15a and 15b are formed of NPB, Alq3, and the like, respectively. In addition, the cathode 15 is deposited on the electron transport layer 15b, and the cathode 15 uses aluminum having excellent conductivity, and the oxidative property is relatively oxidative on the aluminum having high oxidation resistance and then affecting conductivity. Low silver can be deposited. When the cathode 15 is manufactured in the above configuration, the safety of the electrode is increased.

Next, a buffer layer 16 having a low oxygen permeability and a moisture vapor transmission rate is formed on the cathode 15, and a passivation layer 17 is formed on the buffer layer 16 layer. The buffer layer 16 may be formed of a metal or semiconductor thin film, and the passivation layer 17 may be used as an encapsulation film, and may be formed of a multilayer inorganic thin film layer. In this case, the passivation layer 17 may be manufactured by depositing an IZO (or ITO) thin film in several layers with a predetermined thickness.

The top emitting organic light emitting device having the above-described configuration has the following characteristics.

2 is a graph illustrating I-V-L characteristics of an organic light emitting diode according to the present invention. 2, the horizontal axis represents voltage, the left vertical axis represents current density, and the right vertical axis represents luminance. According to the graph (a) between the voltage and the current density, the threshold voltage is near 0V, and the current density gradually increases from 0V. According to the graph (b) between the voltage and the luminance, the applied voltage gradually increases after 8V and shows the brightest state near 13V, and thereafter, the luminance drops rapidly.

3 is a graph of efficiency characteristics of the organic light emitting device according to the present invention. The horizontal axis represents voltage, and the vertical axis represents efficiency (%). The efficiency of the light emitting diode also increases gradually after 0V and decreases in efficiency near 13V.

4 is an emission spectrum of the organic light emitting device according to the present invention. Referring to FIG. 4, the horizontal axis represents wavelength (nm), and the vertical axis represents emission intensity (normalized EL intensity: a.u.). When the wavelength is around 500 ~ 600nm, it shows a green light emission characteristic graph with good luminous efficiency, in this embodiment it can be seen that the highest emission intensity in the vicinity of 520 ~ 530 nm.

5 is a green light emission image of the organic light emitting device according to the present invention. Referring to FIG. 5, it can be seen that the light emitting image of the OLED having the anode manufactured according to the above shows uniform light emission characteristics. In addition, not only uniform light emission characteristics can be observed, but also white spots due to hills generated at the anode are not observed. Therefore, when using the anode electrode according to the present invention, it is possible to increase the luminous efficiency. On the other hand, in the present embodiment, the green light emission image is disclosed to disclose the efficiency of the anode electrode according to the present invention, but red and blue may also provide the same effect.

As mentioned above, the present invention has been described in detail with reference to preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and should be understood by those skilled in the art within the scope of the technical idea of the present invention. Various modifications are possible.

As described above, according to the present invention, first, by forming the anode electrode of the multilayer structure consisting of a conductive metal thin film on the lower and upper portions of the reflective conductive layer, it is possible to improve the adhesion between the substrate and the anode electrode. For example, when the lower conductive layer / reflective conductive layer / the upper conductive layer is formed of Cr / Al / Cr, a separate adhesive is not required to improve adhesion between the substrate and the anode, and thus productivity may be increased. In addition, the reflectance can be adjusted.

Second, by manufacturing a conductive metal thin film as an anode constituting the up-emitting organic light emitting device using a general process, it is possible to improve the productivity and to ensure a low oxygen permeability and moisture permeability between the thin film.

Third, by forming the upper and lower conductive layers of the same metal thin film, not only is possible in the general process but also the number of processes is reduced, thereby ensuring productivity and processability.

Fourth, since the metal thin film is formed by dividing it into several layers, it is not transmitted to the whole when stress is generated, but is prevented from the intermediate thin film, whereby mechanical stress can be reduced.

Claims (12)

A lower conductive layer formed of a conductive metal thin film on the substrate; A reflective conductive layer formed of a reflective metal thin film on the lower conductive layer; And An upper conductive layer formed of the conductive metal thin film on the reflective conductive layer Anode of a multilayer structure comprising a. The method of claim 1, The reflective conductive layer is a multi-layered anode using one of silver, aluminum, silver or an alloy containing at least one element of chromium, copper, manganese, zinc and neodymium in aluminum. The method of claim 2, The reflective conductive layer is an anode having a multilayer structure of 2000 ~ 5000 2000 thickness. The method of claim 1, And the upper conductive layer and the lower conductive layer are formed of at least one of Pt, Pi, and Cr. The method of claim 4, wherein The lower conductive layer is an anode having a multilayer structure of 100 ~ 500Å thickness. The method of claim 4, wherein And the upper conductive layer is formed of the same material as the lower conductive layer. The method of claim 4, wherein The upper conductive layer is an anode having a multilayer structure of 10 ~ 90 ~ thickness. The method of claim 1, The substrate is a multi-layered anode using one of a plastic substrate, a metal thin film, silicon oxide, a glass substrate. An anode having a multilayer structure including a lower conductive layer, a reflective conductive layer, and an upper conductive layer formed of the metal thin film according to any one of claims 1 to 8; A hole injection and transport layer formed on the anode; An emission layer formed on the hole injection and transport layer; An electron transport and injection layer formed on the light emitting layer; And A cathode formed on the electron transport and injection layer Up-emitting organic light emitting device comprising a. The method of claim 9, And the lower conductive layer and the upper conductive layer are formed of the same material. The method of claim 10, And the lower conductive layer and the upper conductive layer are formed of one of Pt, Ti, and Cr. The method of claim 9, The reflective conductive layer is formed by using one of silver, aluminum, silver or aluminum alloy containing at least one element of chromium, copper, manganese, zinc and neodymium.

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