JP2004253315A - Organic light emitting device having long lifetime - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic light emitting device which has a long lifetime and is improved in luminous efficiency. <P>SOLUTION: In this organic light emitting device, an organic luminous layer AxByCz is placed between an anode and a cathode, and A, B and C are mediums for transporting holes and electrons, and electron injecting media, and x, y and z express contents of A, B and C media. The organic luminous layer is composed of a combination of organic media which are mixed and continuous, and does not generate a hetero junction phenomenon, and the sum of x, y and z is 100%, and x has a maximum value at a portion close to the anode, and y and z develop maximum values at the cathode portion. The C medium is an electron injecting medium and is made of a low work function metal, a metal compound, a metal alloy or an organic substance. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an organic light emitting device, and more particularly, to a light emitting device having improved efficiency and lifetime of an organic light emitting diode structure.
[0002]
[Prior art]
In recent developments of organic light emitting devices, much attention has been paid to many characteristics such as high brightness, high viewing angle, low voltage driving, full color and portability. In general, an organic light emitting device has a structure in which a multilayer structure is sandwiched between two electrodes in a sandwich shape. Among them, the organic multilayer structure includes a hole transport layer, a light emitting layer, and an electron transport layer. Also, the electron transporting layer or hole transporting layer can be a light emitting layer, so that light is emitted from the electron transporting layer or hole transporting layer.
[0003]
Usually, the most effective organic light emitting devices further comprise a conductive layer, which is transparent to light. Further, ITO is usually used as a material for this conductive layer. Generally, the ITO is deposited on a transparent substrate made of glass or plastic.
[0004]
Furthermore, although the above-mentioned multilayer structure is used in the construction of an organic light emitting device, the interface between the electron transporting layer and the hole transporting layer itself has low compatibility, which may result in the formation of a poor connecting interface. In some cases, a peeling phenomenon may occur under the influence of a high temperature environment.
[0005]
In addition, the lifetime of a multi-layer light emitting device can be affected by sudden changes in the interface between different media under high voltage. In the prior art, an effective improvement method for such an organic light emitting device is provided, and the light emitting structure includes a hole transport layer, an electron transport layer, and a graded layer, wherein the graded layer is provided. Is located between the hole transporting layer and the electron transporting layer, and the progressive layer is converted from the hole transporting layer organic material to the electron transporting layer organic material in a stepwise or continuous manner. (For example, see Patent Document 1). However, such a structure can be a major factor affecting the lifetime of the organic light emitting device. That is, the interface between the hole transporting layer and the electron transporting layer is normally placed under a bias state and becomes unstable, resulting in a peeling phenomenon.
[0006]
In view of this problem, a structure has been provided that eliminates the influence of the interface between different media (see Patent Document 2). It employs a continuous organic medium AxBy, where A medium transports holes, B medium transports electrons, and x and y indicate the content of A and B media, respectively. The value of the x content gradually increases from almost 0% near the anode to 100% near the cathode, and the value of the y content gradually decreases from almost 100% near the anode to 0% near the cathode. A continuity-free structure can effectively improve the lifetime of the light emitting device.
[0007]
[Patent Document 1]
US Pat. No. 5,925,980 [Patent Document 2]
US Patent No. 6130001
[Problems to be solved by the invention]
The present invention provides one structure, in which a single media layer structure is composed of an organic medium that mixes different materials and exhibits continuity, preventing the occurrence of heterojunction incompatibility problems, In addition, the light emitting effect and the life of the organic light emitting device are effectively improved, and the structure is improved in stability.
[0009]
[Means for Solving the Problems]
The invention according to claim 1 is an organic light emitting device,
An anode and a cathode,
A hole injection layer located between the anode and the cathode,
A progressive layer positioned between the cathode and the hole injection layer and defining a light emitting region;
An organic light-emitting device characterized by comprising:
According to a second aspect of the present invention, in the organic light emitting device according to the first aspect, the progressive layer is a mixed continuous medium, represented by the equation AxByCz, the A medium is a hole transport material, and the B medium is an electron transport material. The C medium is an electron injecting substance, wherein x, y, and z indicate the content of the medium, respectively, to provide an organic light emitting device.
According to a third aspect of the present invention, there is provided the organic light emitting device according to the second aspect, wherein the sum of the contents x, y, and z is 100%.
According to a fourth aspect of the present invention, in the organic light emitting device according to the second aspect, the content x indicates the content of the hole transporting substance, and the numerical value exhibits a maximum value near the anode. It is an organic light emitting device.
According to a fifth aspect of the present invention, in the organic light emitting device according to the second aspect, the contents y and z indicate the contents of the electron transporting substance and the electron injecting substance, respectively, and the sum of x and y is close to the cathode. The organic light emitting device is characterized by exhibiting a maximum value.
According to a sixth aspect of the present invention, there is provided the organic light emitting device according to the second aspect, wherein the progressive layer is doped with at least one kind of fluorescent or phosphorescent pigment.
According to a seventh aspect of the present invention, in the organic light emitting device according to the second aspect, the hole transporting substance is a porphyrin compound or an organic tertiary aromatic amine.
An eighth aspect of the present invention is the organic light emitting device according to the second aspect, wherein the electron transporting material is an organometallic composite.
According to a ninth aspect of the present invention, in the organic light emitting device according to the second aspect, the electron injecting substance is an organic medium having a high electron affinity.
According to a tenth aspect of the present invention, in the organic light emitting device according to the ninth aspect, the electron injecting substance is nitro, carbonyl, cyano, metal, quinoline, or oxaline. The present invention provides an organic light-emitting device, which is a metal composite such as a diazole (oxadiazole), a quinoxanline (quinoxanline), and a silole derivative (silole derivatives) composite.
An eleventh aspect of the present invention is the organic light emitting device according to the second aspect, wherein the electron injecting substance is a non-organic medium having a low work function.
According to a twelfth aspect of the present invention, in the organic light emitting device according to the eleventh aspect, the electron injecting substance is a low work function metal such as an alkali metal, a lithium aluminum alloy, a strontium aluminum alloy, a cesium aluminum alloy, and lithium fluoride. , An organic light emitting device characterized by being made of a metal mixture such as lithium chloride or lithium oxide.
According to a thirteenth aspect, in the organic light emitting device according to the first aspect, the material of the cathode is selected from lithium, magnesium, calcium, and strontium.
According to a fourteenth aspect, in the organic light emitting device according to the first aspect, the material of the cathode is selected from aluminum, indium, copper, gold, and silver.
According to a fifteenth aspect of the present invention, in the organic light emitting device according to the first aspect, an evaporation technique is used for depositing the hole transport material, the electron transport material, and the electron injection material. .
According to a sixteenth aspect of the present invention, in the organic light emitting device according to the fourteenth aspect, an electron transporting organic substance, a hole transporting organic substance, and an electron injecting organic substance are used as a deposition source at the time of vapor deposition, and are sequentially placed in a vapor deposition chamber. It is an organic light emitting device.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The organic light emitting device of the present invention has a single emission continuous medium layer placed between the anode and the cathode, and the single medium layer is a mixture of three types of substances and has continuity and a heterojunction. It is an organic medium exhibiting an unstructured state, which comprises a hole transporting material, an electron transporting material and an electron injecting material. The composition of the medium is represented by AxByCz, where A is a substance capable of injecting and transporting holes, B is a substance capable of transporting electrons, C is a substance capable of injecting electrons, and x, y, z Indicates the contents of the A, B, and C media, respectively.
[0011]
In addition, the contents x, y, and z of the three types of media A, B, and C have the following characteristics. That is, the sum of x, y, and z is 100%, and x is the maximum at a portion approaching the anode (which may include a hole injection layer), and the sum of y and z is the maximum at the cathode. Value (the organic medium may be doped with at least one fluorescent or phosphorescent pigment), the C medium is an electron injecting material, and the electron injecting material may have high electron affinity properties. It is required and therefore contains non-organic substances (eg low work function metals, metal compounds, metal alloys or organic substances).
[0012]
【Example】
FIG. 1 is a sectional view of an organic light emitting device 10 according to the present invention. As can be seen from this figure, the organic light emitting device 10 is formed on the upper surface of a substrate 12, and the substrate 12 is transparent. In addition, the substrate 12 may be formed of glass or a transparent plastic such as polyolefin, polyethylene, or polyarylates.
[0013]
Next, an anode 14 is provided on the upper surface of the substrate 12, and the anode 14 can exhibit a light-transmitting or semi-light-transmitting state in addition to being conductive. The material of the anode 14 is a conductive metal oxide (eg, indium oxide, indium tin oxide, indium zinc oxide, zinc tin oxide) or a conductive transparent polymer (eg, polyaniline). In addition, the anode 14 may also be composed of a thin translucent metal layer (less than 500.ANG.) Of gold, copper, silver and its compounds.
[0014]
Further, a hole injection layer 15 is provided on the upper surface of the anode 14, and the hole injection layer 15 performs a function similar to that of the buffer layer, and adjusts the thermal power and opportunity characteristics of the anode 14 and the organic medium thereon. In addition, the hole injection layer 15 can transport holes in the present invention. On the other hand, the hole injection layer 15 is not necessarily required in the present invention. That is, the hole injection layer 15 is not necessarily provided in the light emitting device of the present invention.
[0015]
In addition, an organic progressive layer 16 is provided on the upper surface of the hole injection layer 15, and the organic progressive layer 16 is sandwiched between the anode 14 and the cathode 18. This organic progressive layer 16 comprises a mixed continuous organic medium without Heter junction. And this continuous organic medium is represented by the equation AxByCz, where A contains a hole transport material, B contains an electron transport material, C contains an electron transport material, and x, y, z have the following properties: Have. That is, the sum of x, y, and z is 100%, and the maximum value of x appears in a portion approaching the anode (which may include a hole injection layer), and its content gradually decreases in the direction of the cathode. Thus, the content x exhibits a minimum value at the cathode portion. Therefore, the content x is at the position where the minimum value appears, the sum of y and z (y + z) appears at the maximum value, and that position is the part approaching the cathode. The C medium is an electron injecting substance, and is an organic medium having characteristics of high electron affinity. On the other hand, the C medium may be a non-organic substance such as a low work function metal, a metal compound, or a metal alloy. Further, the C medium has a function of injecting electrons and transporting electrons, and this layer has a function of easily injecting electrons from the cathode into this layer, so that this layer improves the injection efficiency of the organic light emitting device. . Thus, it should be particularly noted that the organic AxByCz medium described above can be doped with at least one phosphorescent or fluorescent pigment.
[0016]
Comparing the conditions of the electrodes, the content x of the A medium gradually decreases from 100% near the anode 14 to 0% near the cathode 18. As a result, the sum of y and z gradually decreases from almost 100% near the anode 18 near the anode to 0% near the anode 14. In another embodiment, z is also a function of y plus z (ie, y + z), where the z content is between 0% and 100%. The x, y, z content changes are in an organic structure and have a stepwise distribution, and even if the content changes exhibit sudden changes, the actual content changes are deposited in a continuous manner, The transitions still exhibit continuous transitions, a phenomenon which is due to the effect of interdiffusion during the deposition process. In addition, changes in x, y, z content can also be indicative of changes in linearity, and in effect, as will be appreciated by those skilled in the art, steps, lines or other types. Are all within the scope of the present invention. In addition, the deposition rates of the A, B and C media can be easily obtained by careful control of the switch device during the deposition process.
[0017]
The formation of the structure of the present invention is by a mixed vapor deposition technique and is formed by the switched discharge of different organic vapors, so that the A, B, C medium can be any hole transport, electron transport and electron injection material. The hole transporting material may be a porphyric mixture or tertiary aromatic amines, and the electron transporting material may be selected from an organometallic compound. The organic electron injecting material is a medium having a high electron affinity, and usually, in organic synthesis, nitro, carbonyl, cyano, metal, quinoline, oxadiazole, and oxadiazole. , Quinoxanline, and silole derivatives, thereby achieving high electron affinity properties.
[0018]
The electron-injecting material is a non-organic material, a low work function metal such as an alkali metal, a lithium aluminum alloy, a strontium aluminum alloy, a cesium aluminum alloy, and a metal mixture such as lithium fluoride, lithium chloride or lithium oxide. You.
[0019]
The material of the cathode is usually lithium, magnesium, calcium and strontium, and a metal having a high work function can be selected and formed by a vapor deposition technique.
[0020]
In the present embodiment, a transparent substrate and an anode are included, and the entire structure can be reversed to emit light rays upward. At this time, the substrate is formed of an opaque material.
[0021]
Further, in this embodiment, the hole transporting, electron transporting and electron injecting materials are usually deposited by a well-known vapor deposition or sputtering method. According to a typical example, the substrate 12 is placed in a vapor deposition chamber and the hole transporting A source of material, a source of electron transport material, and a source of electron injecting material are each placed in the deposition chamber, and the emission of these organic sources is controlled by gradually and continuously turning on or off.
[0022]
Due to the gradual content change of each one of the media, this grading layer is made of at least three kinds of substances mixed and distributed in the anode and the cathode. Also, the progressive layer containing the three media exhibits a single layer structure and has the mixed properties of the materials described above. This allows the carrier to flow smoothly in this single layer structure.
[0023]
Finally, in this embodiment, the organic progressive layer 16 has its emission content controlled by carefully controlling the valves of each source, and the hole transport from the anode to the cathode in controlling the content trend. The substance A is emitted with a tendency to decrease in content, and the electron transporting substance and the electron injecting substance are emitted with a tendency to increase in content.
[0024]
In the present invention, the new organic dielectric layer is deposited by a vapor deposition method, but the purpose of depositing the medium can also be achieved by a sputtering method.
[0025]
The above is only the description of the embodiment of the present invention, and does not limit the scope of the present invention, and any modification or alteration of details that can be made based on the present invention belongs to the scope of the present invention. .
[0026]
【The invention's effect】
The present invention provides a new organic light emitting device having an improved lifetime. The present invention also provides an organic light emitting device with improved luminous efficiency. The present invention further provides an organic light emitting device with improved stability.
[Brief description of the drawings]
FIG. 1 is a sectional view of an organic light emitting device of the present invention.
[Explanation of symbols]
Reference Signs List 10 light emitting device 12 substrate 14 anode 15 hole injection layer 16 organic progressive layer 18 cathode

Claims (16)

In an organic light emitting device,
An anode and a cathode,
A hole injection layer located between the anode and the cathode,
A progressive layer positioned between the cathode and the hole injection layer and defining a light emitting region;
An organic light-emitting device, comprising: 2. The organic light emitting device according to claim 1, wherein the progressive layer is a mixed continuous medium, represented by the equation AxByCz, wherein the A medium is a hole transport material, the B medium is an electron transport material, and the C medium is electron injection. An organic light-emitting device, wherein x, y, and z each represent a content of a medium. The organic light emitting device according to claim 2, wherein the sum of the contents x, y, and z is 100%. 3. The organic light emitting device according to claim 2, wherein the content x indicates the content of the hole transporting substance, and the numerical value has a maximum value near the anode. 3. The organic light emitting device according to claim 2, wherein the contents y and z indicate the contents of the electron transporting material and the electron injecting material, respectively, and the sum of x and y exhibits a maximum value near the cathode. An organic light emitting device. 3. The organic light emitting device according to claim 2, wherein the progressive layer is doped with at least one kind of fluorescent or phosphorescent pigment. 3. The organic light emitting device according to claim 2, wherein the hole transporting substance is a porphyrin compound or an organic tertiary aromatic amine. 3. The organic light emitting device according to claim 2, wherein the electron transporting material is an organometallic composite. 3. The organic light emitting device according to claim 2, wherein the electron injecting substance is an organic medium having a high electron affinity. 10. The organic light emitting device according to claim 9, wherein the electron injecting substance is nitro, carbonyl, cyano, metal, quinoline, oxadiazole, quinoxaneline. An organic light emitting device, comprising: a metal composite such as a quinoxanline and a silole derivative. 3. The organic light emitting device according to claim 2, wherein the electron injecting substance is a low work function non-organic medium. 12. The organic light emitting device according to claim 11, wherein the electron injecting substance is a low work function metal such as an alkali metal, a lithium aluminum alloy, a strontium aluminum alloy, a cesium aluminum alloy, and lithium fluoride, lithium chloride or lithium oxide. An organic light-emitting device comprising a metal mixture as described above. The organic light emitting device according to claim 1, wherein the material of the cathode is selected from lithium, magnesium, calcium, and strontium. 2. The organic light emitting device according to claim 1, wherein the material of the cathode is selected from aluminum, indium, copper, gold and silver. The organic light emitting device according to claim 1, wherein a deposition technique is used for depositing the hole transport material, the electron transport material, and the electron injection material. 15. The organic light emitting device according to claim 14, wherein an electron transporting organic substance, a hole transporting organic substance, and an electron injecting organic substance are used as deposition sources during deposition and are sequentially placed in a vapor deposition chamber.

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