JP2009152015A - Organic electroluminescence element, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive organic EL element with an excellent element lifetime, and its manufacturing method capable of reducing power consumption of the organic EL element having a tandem structure, and significantly improving productivity. <P>SOLUTION: The manufacturing method of the organic EL element includes a positive electrode forming step for forming a positive electrode 20 on a substrate 10, a first light emitting layer forming step for forming a light emitting layer 302-1 on a surface of the positive electrode 20, an interface layer forming step for forming a precursor containing a conductive organic polymer with molecular weight 1000 or more on a surface of the light emitting layer 302-1 by a wet film forming method, and forming an n-type light emitting unit interface layer 401 and a p-type light emitting unit interface layer 402 by crosslinking reaction of the formed precursor, a second light emitting layer forming sep for forming a light emitting layer 302-2 on a surface of the p-type light emitting unit interface layer 402, and a second electrode forming step for forming a negative electrode 50 on the light emitting layer 302-2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an organic electroluminescent element, and more particularly to an organic electroluminescent element used as a display device and a method for manufacturing the same.

  An element obtained by sandwiching an organic thin film between two opposing electrodes and applying light to obtain light emission (electroluminescence) is called an organic electroluminescence element (hereinafter referred to as an organic EL element). An organic EL element was found in the 1960s (Non-patent Document 1), and an element structure having a practical process and characteristics was developed in the 1980s (Non-Patent Document 2). Subsequently, in the early 1990s, organic EL elements using polymers were reported (Non-patent Document 3).

  In an organic EL element using a low molecular material, an organic thin film is formed by a vacuum deposition method. Since a vacuum process is used, an organic EL element based on a low molecular material is produced under conditions where impurities and dust are not mixed, and thus has a feature that it has a long lifetime and few pixel defects.

  On the other hand, an organic EL element using a polymer material is obtained by applying a solution or dispersion obtained by dissolving a polymer in a solvent by a wet method. Therefore, the polymer-based organic EL element has a feature that it is manufactured by a simple process under atmospheric pressure and has little material loss.

  Each of the organic EL elements has advantages such as being self-luminous and bright and having a small viewing angle dependency, and has recently been developed as a light emission source for a display and a light source for illumination.

  On the other hand, in any organic EL element, the biggest problem is the element life. In many cases, the lifetime of the element is evaluated by the time during which the initial luminance is halved. As a premise for explaining measures taken to improve the device lifetime, the basic operation principle of the organic EL device will be briefly described below.

  When a voltage is applied between the anode and cathode sandwiching the organic layer, holes are injected from the anode and electrons are injected from the cathode into the organic layer. The injected holes and electrons move in the organic layer by a hopping mechanism and recombine in the organic layer. At this time, excited species of the organic matter are generated, and energy emission when the organic species returns to the ground state is extracted as light energy to the outside of the device.

  The mechanism by which the luminance of the organic EL element decreases depending on the driving time is described as follows, for example. The above-described hole or electron hopping is a reaction in which an organic radical cation or radical anion is generated in an organic layer, and a charge transfer (one-electron redox reaction) occurs between these organic substances in a neutral state. Refers to a phenomenon in which is repeated. The radical cation or radical anion generated as an intermediate state has higher energy than the neutral state, and causes chemical alteration, that is, deterioration with a certain probability. In addition, the excited species of the organic matter described above has a high energy corresponding to the energy of the emitted light compared to its ground state, and, as with the radical species, has a certain degree of chemical alteration, that is, degradation. Wake up.

  Here, a measure for extending the life of the organic EL element will be described. In order to suppress the deterioration of the organic EL element, there are typically the following three approaches.

  First, a material that is resistant to deterioration of the mechanism is used. This corresponds to improving the stability of radical cation species or radical anion species and excited species, that is, reducing the probability of deterioration.

  Secondly, a device structure in which the mechanism does not easily deteriorate is used. For example, the device structure is a three-layer structure of a hole transport layer, a light-emitting layer, and an electron transport layer, a material in which the radical cation species is stable in the hole transport layer, a material in which the excited species is stable in the light-emitting layer, and a radical in the electron transport layer By using a material with stable anion species, the probability of each degradation process is reduced.

  Third, the amount of current flowing through the device is reduced. This is because assuming that device deterioration occurs at a certain probability, the number of radical species and excited species generated per unit time decreases, and consequently deterioration hardly occurs.

  Usually, when the current value flowing through the device decreases, the luminance decreases. In order for an organic EL element to be applied to a display or a lighting application, luminance corresponding to the application is required, and the current value cannot be simply reduced in order to extend the life. In order to reduce the current value while maintaining a constant luminance, it is necessary to improve the light emission efficiency of the element. For this purpose, a light emitting material with excellent light emission characteristics is used, or by improving the device structure Generally, the recombination balance between holes and electrons is improved, or the light extraction efficiency from the inside of the device to the outside of the device is improved.

  As a method for improving the current efficiency of the organic EL element, a plurality of light emitting units are connected in series (tandem) via an interface layer between the light emitting units (hereinafter this layer is referred to as a light emitting unit interface layer). Patent Documents 1 to 3 propose a structure in which light emission is superimposed. Although the name of the structure of the organic EL element varies depending on the inventor or the author, this structure is referred to as a tandem structure here. Further, the light emitting unit is the same as the definition in Patent Document 2, and is defined as a layer structure having a light emitting layer, excluding the cathode and the anode, among elements constituting the organic EL element not having a tandem connection structure. Hereinafter, the operating principle of the tandem structure and its features will be described.

  FIG. 11 is a structural sectional view of an organic EL element having a conventional tandem structure. The organic EL element 800 in the figure includes a transparent substrate 801, a transparent anode 802, n light emitting units 803-1 to 803-n, and n-1 light emitting unit interface layers 804-1 to 804-n-. 1 and a reflective cathode 805.

  FIG. 12 is a structural sectional view of a light emitting unit of an organic EL element having a conventional tandem structure. The light emitting unit 803 in the figure includes a hole transport layer 803A, a light emitting layer 803B, and an electron transport layer 803C.

  As a premise for explaining the organic EL element having the tandem structure, an operation principle of a non-tandem structure having a single light emitting unit will be described in detail.

  FIG. 13 is a diagram in which an organic EL element having a non-tandem structure with a single light emitting unit is connected to a DC voltage source. The organic EL element 810 in the figure includes a light emitting unit 803, an anode 802, and a cathode 805. In addition, a DC voltage source 901 is connected to the organic EL element 810. Here, regarding the light emitting unit 803, the light emitting layer 803B which is a component thereof is assumed to be a single layer.

  FIG. 14 is a schematic diagram of energy levels when an organic EL element having a non-tandem structure is not connected to a power source. In the figure, the work functions of the anode 802 and the cathode 805, the energy level (HOMO) of the highest occupied molecular orbital of the light emitting layer 803B, and the energy level (LUMO) of the lowest unoccupied molecular orbital of the light emitting layer 803B are schematically shown. Has been shown.

FIG. 15 is a schematic diagram of energy levels when an organic EL element having a non-tandem structure is short-circuited. This figure is an energy diagram when the anode 802 and the cathode 805 are short-circuited, that is, when an external circuit is driven with V = 0. The anode 802 and the cathode 805 containing a large amount of free electrons have the same Fermi energy level by an electrical short circuit. A built-in potential V ₀ corresponding to the work function difference between the anode 802 and the cathode 805 is applied to the light emitting layer 803B.

FIG. 16 is a schematic diagram of energy levels when an external electric field is applied to an organic EL element having a non-tandem structure. The figure shows the energy level when the anode 802 is positive and the cathode 805 is negative, and a voltage higher than the emission start voltage is applied. According to the external voltage V ₀ , holes from the anode 802 and electrons from the cathode 805 are injected and transported into the light emitting layer 803B, whereby a current I ₀ flows in the external circuit. Then, holes and electrons recombine in the light emitting layer 803B to generate an excited state in the light emitting layer 803B, and the emitted light L ₀ is extracted to the outside.

  FIG. 17 is a diagram in which two non-tandem organic EL elements connected in series are connected to a DC voltage source. In the figure, the cathode 805-1 of the organic EL element 810-1 and the anode 802-2 of the organic EL element 810-2 are short-circuited and a DC voltage source 901 is connected. Again, regarding the light emitting unit 803, the light emitting layer 803B which is a component thereof is assumed to be a single layer.

  FIG. 18 is a schematic diagram of energy levels when two non-tandem organic EL elements connected in series are not connected to a power source. In the same figure, similarly to FIG. 14, the work function of each layer or the energy level of HOMO and LUMO is schematically shown.

FIG. 19 is a schematic diagram of energy levels when two non-tandem organic EL elements connected in series are short-circuited. FIG. 16 is an energy diagram when the anode 802 and the cathode 805 are short-circuited, that is, when an external circuit is driven with V = 0, similarly to FIG. 15. The anode 802 and the cathode 805 which are in contact with each other through the conductive wires have the same energy level as in FIG. Similarly to FIG. 15, the built-in potential V ₀ corresponding to the work function difference between the anode 802 and the cathode 805 is applied to the light emitting layer 803B-1 and the light emitting layer 803B-2.

FIG. 20 is a schematic diagram of energy levels when an external electric field is applied to two non-tandem organic EL elements connected in series. In the figure, the energy level is shown when the anode 802-1 is positive and the cathode 805-2 is negative, and a voltage higher than the emission start voltage is applied. Since the organic EL element 810-1 and the organic EL element 810-2 are connected in series, the voltage required to pass the current value I ₀ is 2V ₀ , but the total light emission is 2L ₀ .

  FIG. 21 is a diagram in which an organic EL element having a tandem structure including a light emitting unit interface layer is connected to a DC voltage source. In the figure, two light emitting units (light emitting layers) 803B-1 and 803B-2 are connected in series via a light emitting unit interface layer 804 composed of two layers, an n-type interface layer 804A and a p-type interface layer 804B. The tandem organic EL element 820 is connected to the DC voltage source 901. In this conventional example, light emitting units (light emitting layers) 803B-1 and 803B-2 indicate a light emitting layer 803B.

  FIG. 22 is a schematic diagram of energy levels when an organic EL element having a tandem structure including a light emitting unit interface layer is not connected to a power source. In the same figure, similarly to FIG. 14, the work function of each layer or the energy level of HOMO and LUMO is schematically shown. Here, for easy comparison with the case of the two non-tandem organic EL elements shown in FIG. 17, the electron conduction level of the n-type interface layer 804A and the hole conduction level of the p-type interface layer 804B are: , And the energy levels of the anode 802 and the cathode 805, respectively.

FIG. 23 is a schematic diagram of energy levels when an organic EL element having a tandem structure including a light emitting unit interface layer is short-circuited. FIG. 16 is an energy diagram when the anode 802 and the cathode 805 are short-circuited, that is, when an external circuit is driven with V = 0, similarly to FIG. 15. The anode 802 and the cathode 805 have the same energy level as in FIG. In addition, the n-type interface layer 804A and the p-type interface layer 804B try to have the same energy level, but generally they are not perfectly aligned, and this energy difference ΔV becomes an excessive voltage and is added to the drive voltage of the device. Will be. This is presumably because the light emitting unit interface layer 804 is required to be transparent, and it is difficult to use a metal material having a large amount of light reflection or absorption, and therefore there is an injection barrier due to material limitations.

FIG. 24 is a schematic diagram of energy levels when an external electric field is applied to an organic EL element having a tandem structure including a light emitting unit interface layer. The figure shows the energy level when the anode 802 is positive and the cathode 805 is negative, and a voltage higher than the emission start voltage is applied. Since the light-emitting units (light-emitting layers) 803B-1 and 803B-2 are connected in series, the voltage required to flow the current value I ₀ is 2V ₀ + ΔV, but the total light emission is 2L _0. .

An organic EL element having a tandem structure in which the number of stacked layers is n can be considered in the same manner as in the case where the number of stacked layers is two. Therefore, when an organic EL element having a tandem structure in which n light emitting units of the same kind are stacked, a current value necessary to obtain a constant luminance L ₀ is about I ₀ / n. That is, since the amount of current required to obtain a constant luminance is small, the third policy for improving the element lifetime described above is executed, and the lifetime is greatly improved.

  When the value of the current flowing through each light emitting unit is reduced to one half or one third, the improvement of the lifetime is not simply doubled or tripled, but more than that. As an example, Non-Patent Document 4 reports that the half-life of an organic EL element is improved in inverse proportion to the luminance of 1.7. This suggests that the half-life of the organic EL element is extended by about 3.2 times at half the luminance and the half-life of the organic EL element is increased by about 6.5 times at one-third of the luminance.

In addition, the current value of an organic EL element having a tandem structure in which n light emitting units are stacked is 1 / n compared to an organic EL element composed of one light emitting unit. The voltage is generally n times or more. Therefore, the organic EL element having a tandem structure is comparable in power consumption to the organic EL element having a non-tandem structure. The advantage of the tandem structure is that the required current value can be reduced, so that the burden on the external circuit is small, and the lifetime is improved because the current value is small.
M. Pope et al., Journal of Chemical Physics, 1963, 38, p.2042-2043. CW Tang and SA Vanslyke, Applied Physcs Letters, 1987, 51, p. 913-915 JH Burroughes et al., Nature, 1990, No. 347, p. 539-541 C. Fery et al., Applied Physics Letters, 2005, 87, 213502. Hideki Shirakawa, Polymer, 1988, No. 37, p. 518 TEA Chemical Co., Ltd. website, Internet <URL: http://www.ta-chemi.jp/PEDOT.html> Japanese Patent Laid-Open No. 11-329748 JP 2003-272860 A Japanese Patent Application Laid-Open No. 2005-166737

As described above, the organic EL element having the tandem structure has a great merit of extending the life, but the control of the excess voltage ΔV described in FIG. As described above, ΔV is a voltage drop in the light emitting unit interface layer, which is a voltage added to the voltage V ₀ necessary for securing the current value I ₀ , and hinders reduction in power consumption. Further, the light emitting unit interface layer has a role of injecting electrons into the light emitting unit on the anode side and holes into the light emitting unit on the cathode side. For this purpose, the light emitting unit interface layer needs to have an appropriate energy level. However, the injection efficiency of electrons and holes is lowered, and as a result, the improvement of the light emission efficiency is hindered.

  From the above viewpoint, in order to obtain a tandem type organic EL device characterized by low power consumption and high light emission efficiency, the light emitting unit interface layer is extremely important, and improvement of materials used and layer configuration is required. The light emitting unit interface layer is sometimes called a “charge generation layer” or a “hole current-electron current conversion layer” due to its role (Patent Document 2 and Patent Document 3).

Typical conditions required for the light emitting unit interface layer are high transparency with respect to light emission from the light emitting unit, no damage to the underlying organic layer during film formation, low excess voltage ΔV, and The hole and the electron can be efficiently injected into the adjacent light emitting unit.

  The followings have been reported as a structure and manufacturing method of a tandem organic EL element for satisfying the requirements for the light emitting unit interface layer.

  In Patent Document 1, magnesium + silver alloy thin film / indium-tin oxide or indium-zinc oxide is used. In this case, the magnesium / silver electrode is formed as an ultra-thin film to form a semi-transmissive electrode, but the absorption is not negligible, so that the light emission is absorbed and the current efficiency is smaller than the number of layers that should be theoretically obtained. Moreover, there is a concern about sputtering damage of indium-tin oxide or indium-zinc oxide.

  Patent Document 2 discloses a configuration of an n-doped electron transport layer / p-doped hole transport layer or a metal oxide. Specific examples include lithium-doped bathocuproine / vanadium oxide + NPD.

  Patent Document 3 discloses a structure in which a metal layer capable of reducing the n dopant is inserted in order to avoid an undesirable reaction between the n dopant and the p dopant in Patent Document 2.

  In Non-Patent Document 6, lithium-doped Alq layer / iron (III) chloride-doped NPD is used.

  Since these are doped with a metal or a metal salt, it is considered that deterioration of the element due to diffusion of the metal or ions thereof becomes a problem. Furthermore, since each layer needs to be formed by a vacuum process called co-evaporation, there is a problem in productivity in that the material loss is large and the increase in area is limited. In particular, when producing a tandem organic EL element in which a large number of light emitting units are stacked, the number of light emitting unit interface layers is required for (number of light emitting units −1) layers, which increases the productivity of the stacking process. Important to the whole production.

  On the other hand, as described above, the conductive high molecular organic material employs wet film formation by printing because of its high viscosity compared to the above inorganic material and low molecular organic material, and therefore requires a large vacuum device. First, large area film formation is realized using a simple apparatus.

In general, it is known that a conductive polymer exhibits electrical conductivity even in an undoped state because a developed π electron can move relatively freely. For example, a cis-type polyacetylene thin film has a conductivity of the order of 10 ⁻⁹ S / cm, and a trans-type polyacetylene thin film has a conductivity of the order of 10 ⁻⁸ S / cm (Non-patent Document 5).

Further, doping with iodine, arsenic pentafluoride, or the like for the purpose of giving a free charge shows a very high conductivity of 10 ² to 10 ⁵ S / cm. Another example is a polythiophene derivative. A thin film doped with poly (3,4-ethylenedioxy) thiophene with polystyrene sulfonic acid exhibits a conductivity of 400 to 500 S / cm. In general, the higher the conductivity is, the more the excessive voltage ΔV is reduced. Therefore, the conductive polymer is an advantageous material from the viewpoint of reducing ΔV.

  Furthermore, a thin film obtained by doping poly (3,4-ethylenedioxy) thiophene with polystyrene sulfonic acid exhibits a high value of 90% transmittance at a film thickness of 12 μm or less (Non-patent Document 6). In addition, since it has a high molecular weight, it is easy to form a thin film and has excellent stability.

  From the above characteristics, the conductive polymer has sufficient holes and electrons to be injected into the light emitting unit, and has high transparency with respect to the light emitted from the light emitting unit, so that the light emission in the tandem organic EL element is achieved. It has compatibility as a unit interface layer.

  Therefore, the conductive polymer organic EL element having a tandem structure manufactured by a wet film formation method has a longer life than a light emitting unit interface layer using a low molecular compound, a metal thin film, an inorganic conductive film, or an inorganic semiconductor film. The possibility of having advantages such as large area and high productivity is considered high.

However, in the tandem conductive polymer organic EL element by the wet film formation method, it is difficult to control the laminated interface, and thus the excessive voltage ΔV is not reduced as theoretically. Therefore, there is a problem that power consumption is reduced due to the use of the conductive organic polymer in the light emitting interface unit, and high productivity unique to wet film formation is not exhibited.

  In view of the above problems, the present invention reduces the power consumption of a conductive polymer organic EL element having a tandem structure and greatly improves the productivity, thereby providing an organic EL element that is excellent in element lifetime and inexpensive and a method for manufacturing the same The purpose is to provide.

  In order to achieve the above object, a method for manufacturing an organic electroluminescent element according to the present invention is a method for manufacturing an organic electroluminescent element, comprising: a first electrode forming step of forming a first electrode on a substrate; A first light emitting unit forming step of forming a first light emitting unit having at least one first organic light emitting layer on the surface of one electrode; and a conductive organic polymer having a molecular weight of 1000 or more on the surface of the first light emitting unit. A first interfacial layer film forming step for forming a precursor containing a precursor by a wet film forming method, and at least the surface is intermolecularly or intramolecularly crosslinked by cross-linking the precursor formed by the wet film forming method. A first interface layer bridging step for forming the light emitting unit interface layer, and a second organic light emitting layer comprising at least one second organic light emitting layer on the surface of the light emitting unit interface layer. A second light emitting unit formation step of forming a light unit, on the second light-emitting unit, characterized in that it comprises a second electrode forming step of forming a second electrode.

As a result, the conductive organic polymer that contributes to the reduction of the excess voltage ΔV is used as the light emitting unit interface layer, and at least the surface of the light emitting unit interface layer has a cross-linked structure by a cross-linking reaction. It is insolubilized and does not dissolve or diffuse into other layers. Therefore, the energy level of the light emitting unit interface layer is stabilized, efficient carrier injection into the light emitting layer is realized, and productivity is improved as the yield is improved.

  In the first light emitting unit forming step, a first light emitting layer forming step of forming a precursor containing a conductive organic polymer having a molecular weight of 1000 or more by a wet film forming method, and a film forming by the wet film forming method. It is preferable to include a first light-emitting layer cross-linking step of forming the first organic light-emitting layer having at least a surface cross-molecularly or intramolecularly cross-linked by cross-linking the formed precursor.

  This insolubilizes not only at the interface with the upper layer of the light emitting unit interface layer but also at the interface with the lower layer, thereby accelerating the carrier injection efficiency and productivity in the light emitting layer.

  In the first interface layer bridging step, the light emitting unit interface layer is of one conductivity type, and further after the first interface layer bridging step and before the second light emitting unit forming step, A second interface layer forming step of forming a precursor containing a conductive organic polymer having a molecular weight of 1000 or more on the surface of the conductive light emitting unit interface layer by a wet film forming method, and forming a film by the wet film forming method It is preferable to include a second interfacial layer cross-linking step of forming a reverse conductivity type light emitting unit interfacial layer in which at least the surface is intermolecularly or intramolecularly cross-linked by performing a cross-linking reaction of the precursor.

Thus, electrons from the n-type conductive organic polymer layer are applied in the anode direction to which a positive voltage is applied, and holes are transmitted from the p-type conductive organic polymer layer in the cathode direction to which a negative voltage is applied. Are injected into each adjacent light emitting unit. Further, since the interfaces of the layers of the light emitting unit interface layer all have a crosslinked structure due to a crosslinking reaction, the respective layers are insolubilized, and elution and diffusion to other layers do not occur. Therefore, power consumption can be reduced along with the reduction of the excess voltage ΔV, and light emission efficiency can be improved by highly efficient carrier injection into the light emitting unit.

  Moreover, it is preferable that the layer formed with the organic substance formed between the first electrode and the second electrode is formed by the wet film forming method.

  Thereby, the layer formed with the organic substance pinched | interposed between both electrodes is consistently formed by the wet film forming method. Therefore, material loss can be reduced and the area can be increased, and productivity can be improved.

  Moreover, it is preferable to carry out a crosslinking reaction at least on the surface of the layer formed of the organic material each time the layer formed of the organic material is formed.

  This insolubilizes the interface of the layer formed of each organic material that is consistently formed by the wet film forming method, so that elution or diffusion to the adjacent interface does not occur. Therefore, the film quality of each layer is made uniform, and the productivity is improved as the yield is improved.

  The film formation by the wet film formation method is a solution in which a precursor containing the conductive organic polymer is dispersed or dissolved in an atmosphere of an inert gas having a water content concentration and an oxygen content concentration of 1000 ppm or less. The solution is preferably sprayed, applied, or printed, and the solution preferably has a water content and oxygen content of 1000 ppm or less.

  Thereby, it is avoided that the dopant of the n-type conductive organic polymer layer or p-type conductive organic polymer layer which is the light emitting unit interface layer is deteriorated by water or oxygen present in the solvent and the environment. Therefore, it becomes possible to obtain an organic EL element excellent in production efficiency and element life.

  In the cross-linking reaction, it is preferable that the surface of the precursor is cross-linked between molecules or intra-molecularly by keeping the temperature of the substrate at 100 ° C. or higher.

  Thereby, the cross-linking reaction by thermal energy is promoted over the entire layer. Therefore, elution to an adjacent layer is avoided not only on the layer surface but also on the back surface. Moreover, it becomes possible to perform a crosslinking reaction with an inexpensive heating apparatus.

  In the crosslinking reaction, the surface of the precursor is intermolecularly or intramolecularly irradiated by irradiating ultraviolet light having a wavelength of 200 to 450 nm with an irradiation power of 10 to 1000 W and an irradiation time of 1 to 600 seconds. It may be cross-linked.

  Thereby, the crosslinking reaction by light energy accelerates. It is also possible to cause only the outermost surface to undergo a crosslinking reaction by adjusting the wavelength, irradiation power, or irradiation time. Therefore, the structural change or alteration of the organic light-emitting body itself due to the promotion of the crosslinking reaction hardly occurs. Further, by irradiating light from the upper part of the film to be subjected to the cross-linking reaction, excessive heat addition to the already formed other layer is avoided, so that the film quality of the other layer does not change. Therefore, the productivity can be stabilized with the yield improvement.

  The precursor containing the conductive organic polymer may include a conductive polymer into which a substituent that crosslinks between molecules or within a molecule by heat or light energy is introduced.

  Thereby, the organic substance which produces | generates a carrier and the organic substance which light-emits itself can carry out a crosslinking reaction. Therefore, since it is not necessary to mix organic substances for the purpose of only the crosslinking reaction, it is possible to realize simple and inexpensive production using a material with little mixture.

  In order to achieve the above object, an organic electroluminescence element according to the present invention is formed on a substrate, a first electrode formed on the substrate, and a surface of the first electrode, and emits light by injecting carriers. A first light-emitting unit comprising at least one first organic light-emitting layer, and a light-emitting unit interface formed of a conductive organic polymer having a molecular weight of 1000 or more on the surface of the first light-emitting unit and supplying carriers to the organic light-emitting layer A second light-emitting unit including at least one second organic light-emitting layer that is formed on the surface of the light-emitting unit interface layer and emits light by carrier injection; and a second light-emitting unit formed on the second light-emitting unit. The light-emitting unit interface layer includes at least a cross-linking reaction of the conductive organic polymer precursor formed by a wet film formation method. Surface respectively is characterized in that it comprises a intermolecular or intramolecular crosslinked p-type conductive organic polymer layer and the n-type conductive organic polymer layer.

As a result, the light emitting unit interface layer composed of the conductive organic polymer that contributes to the reduction of excess voltage ΔV has a cross-linked structure due to the cross-linking reaction, so that the light emitting unit interface layer is insolubilized and eluted or diffused into other layers. Does not occur. Therefore, low power consumption accompanying reduction of excess voltage ΔV is realized, and light emission efficiency is improved by highly efficient carrier injection into the light emitting unit, and productivity is improved along with yield improvement.

  According to the organic EL element and the manufacturing method thereof of the present invention, the power consumption of the conductive polymer organic EL element having a tandem structure is reduced and the productivity is greatly improved. A molecular organic EL device and a method for producing the same can be provided.

  The organic electroluminescence element in the present embodiment (hereinafter referred to as an organic EL element) has a tandem structure, and the surface or the whole of the wet-formed conductive polymer precursor is intermolecularly or intramolecularly crosslinked. The p-type conductive organic polymer layer and the n-type conductive organic polymer layer are provided between the plurality of light emitting unit layers.

As a result, the p-type conductive organic polymer layer and the n-type conductive organic polymer layer having high conductivity are insolubilized, and elution and diffusion to other layers do not occur. High luminous efficiency and low power consumption are realized by reducing the voltage ΔV, and productivity is improved by wet film formation.

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

  FIG. 1 is a structural cross-sectional view of a tandem organic EL element in an embodiment of the present invention.

  The tandem organic EL element 1 in FIG. 1 includes a substrate 10, an anode 20, n light emitting units 30-1, 30-2,..., 30 -n, and (n−1) light emitting units. Interface layers 40-1, 40-2,..., And 40- (n-1), and a cathode 50 are provided.

  The substrate 10 needs to have a high transmittance with respect to the light emission of the organic EL when the light emission is taken out from the substrate side. As the material, for example, a glass substrate or a quartz substrate is used. Further, by using a plastic substrate such as polyethylene terephthalate or polyethersulfone, it is possible to impart bendability to the entire organic EL. On the other hand, when light emission is extracted from the side opposite to the substrate, the substrate need not be transparent, and an opaque plastic substrate or a metal substrate may be used. Furthermore, a metal wiring or a transistor circuit for driving the organic EL may be formed on the substrate.

  The anode 20 is formed on the surface of the substrate 10, and n light emitting units 30-1, 30-2, ... 30-n and (n-1) light emitting unit interface layers 40-1, 40-2. ... A positive external voltage is applied to 40- (n-1). Thereby, holes are injected from the anode 20 into the n light emitting units 30-1, 30-2,... 30-n. Then, in the n light emitting units 30-1, 30-2,... 30-n, holes and electrons described later are recombined so that the n light emitting units 30-1, 30-2,. -An excited state is generated within 30-n, and light emission is extracted outside. Further, when the anode 20 is an electrode on the side from which light emitted inside the element is extracted, it is necessary for the anode 20 to be transparent to the light. Examples of the transparent electrode material include an indium-tin oxide electrode and an indium-zinc oxide electrode. On the other hand, when the electrode is not the light extraction side, a metal or an alloy may be used. The electrode may be formed of one layer or may be formed of multiple layers.

  The light emitting unit 30-1 is formed on the surface of the anode 20, includes at least one light emitting layer, and has a function of emitting light by generating an excited state by injecting and recombining holes and electrons.

  FIG. 2 is an example of a structural sectional view of the light emitting unit. The light emitting unit 30 in the figure includes a hole transport layer 301, a light emitting layer 302, and an electron transport layer 303 from the substrate side. Examples of the material of the light-emitting layer 302 include polyfluorene derivatives, polythiophene derivatives, and polyphenylene vinylene derivatives. The polyphenylene vinylene derivative has the following formula:

で表される化合物ＭＥＨ−ＰＰＶ（Ｐｏｌｙ（２−ｍｅｔｈｏｘｙ，５−（２’−ｅｔｈｙｌ−ｈｅｘｙｌｏｘｙ）−ｐ−ｐｈｅｎｙｌｅｎｅｖｉｎｙｌｅｎｅ）が挙げられる。発光ユニット界面層４０−１は、発光ユニット３０−１の表面に形成され、発光ユニット３０−１及び発光ユニット３０−２にキャリアを供給する機能を有する。

The compound MEH-PPV (Poly (2-methyoxy, 5- (2′-ethyl-hexyloxy) -p-phenylenevinylene)) is represented by the surface of the light emitting unit 30-1. And has a function of supplying a carrier to the light emitting unit 30-1 and the light emitting unit 30-2.

FIG. 3 is an example of a structural cross-sectional view of the light emitting unit interface layer. The light emitting unit interface layer 40 in the figure includes an n-type light emitting unit interface layer 401 and a p-type light emitting unit interface layer 402 on the surface thereof. By making the anode side an n-type (n-doped) conductive polymer layer and the cathode side a p-type (p-doped) conductive polymer layer, holes and electrons can be easily injected into the light-emitting unit layer. At the same time, the excessive voltage ΔV is reduced, and an efficient organic EL element having a tandem structure is obtained. The two layers may be in contact with each other, but a thin metal layer or the like may be sandwiched between them.

The n-type light emitting unit interface layer 401 and the p-type light emitting unit interface layer 402 are conductive polymer layers having a conductivity of 1.0 × 10 ⁻⁸ S / cm or more and a molecular weight of 1000 or more. In general, the limit conductivity indicating semiconductor characteristics is 10 ⁻⁸ S / cm, and if the conductivity is less than this, it becomes insulating, and it becomes difficult to obtain an organic EL element having a tandem structure with a small excess voltage ΔV. In order for a conductive polymer to have high conductivity, a sufficient spread of π conjugation is important, and this requires a molecular weight of 1000 or more. In addition, in order to be easy to form a thin film by a wet film formation method and excellent in stability, the high viscosity of the polymer is required, and this requires a molecular weight of at least 1000 or more. . In addition, these polymer material layers are generally not a vacuum process, but can be applied by a wet film formation method at normal pressure, which can improve the productivity of the interface layer of the light emitting unit. Good compatibility with organic EL device fabrication methods.

  The n-type light emitting unit interface layer 401 preferably has an energy level for generating anions, that is, an energy level of the lowest unoccupied molecular orbital (LUMO) of 2.5 eV to 4.5 eV with respect to the vacuum level. By satisfying this energy level, an anion charge is likely to be generated and the conductivity is increased. In addition, an effect that electrons are easily injected into the electron transport layer 303 of the adjacent light emitting unit 30 is obtained. Examples of materials that satisfy this energy level include polythiophene derivatives, polyphenylene vinylene derivatives, polyacetylene derivatives, and polymers containing nitrogen-containing aromatic heterocycles. As an example, a polymer containing an aromatic heterocycle containing nitrogen has the following formula:

で示されるようなポリフルオレンとベンゾチアジアゾールを共重合した高分子が挙げられる。また、ベンゾチアジアゾール以外の窒素を含有する芳香族複素環としては、例えば、ピリジン、ビピリジン、オキサジアゾール、トリアゾール、ベンゾアゾール、フェナントロリンなどが挙げられる。

And a polymer obtained by copolymerizing polyfluorene and benzothiadiazole as shown in FIG. Examples of the aromatic heterocycle containing nitrogen other than benzothiadiazole include pyridine, bipyridine, oxadiazole, triazole, benzoazole, phenanthroline, and the like.

  Note that an alkali metal, an alkaline earth metal, an aliphatic quaternary amine salt, an organic complex of an alkali metal, or an organic complex of an alkaline earth metal is preferably mixed with the polymer material. Thereby, anions are generated as electric charges in the n-type light emitting unit interface layer 401. Examples of the ligand of these organic complexes include acetate, acetoacetate, quinoline and the like. Since the anion is movable, the conductivity is dramatically improved, the injection of electrons into the light emitting unit 30 is facilitated, and the excessive voltage ΔV is reduced.

  The p-type light emitting unit interface layer 402 preferably has an energy level for generating a cation, that is, an energy level of the highest occupied molecular orbital (HOMO) of 4.8 eV to 5.8 eV with respect to the vacuum level. . By satisfying this energy level, an effect of easily injecting holes into the hole transporting layer of the adjacent light emitting unit can be obtained in addition to the increase in electric conductivity that is likely to generate cationic charges. Examples of materials that satisfy this energy level include polythiophene derivatives, polyaniline derivatives, polyacetylene derivatives, polypyrrole derivatives, and polymers containing aromatic tertiary amines. As an example, a polymer containing an aromatic tertiary amine may have the following formula:

で示されるようなポリフルオレンとトリフェニルアミンを共重合した高分子が挙げられる。

And a polymer obtained by copolymerizing polyfluorene and triphenylamine as shown in FIG.

  Note that the polymer material is preferably mixed with a metal oxide, a metal salt, a halogen, an aromatic tertiary amine salt, a sulfonate, or a carboxylate. Thereby, cations are generated as charges in the p-type light emitting unit interface layer 402. Since the cation is movable, the conductivity is remarkably improved, holes are easily injected into the light emitting unit 30, and the excess voltage ΔV is reduced.

  Here, the n-type light emitting unit interface layer 401 and the p-type light emitting unit interface layer 402 have a crosslinked structure on at least the surface. A crosslinked structure is a structure in which polymer chains are chemically linked to each other directly or through several bonds at any position other than the end, or two distant locations in the ring of a cyclic organic substance. A connected structure.

  The n-type light-emitting unit interface layer 401 and the p-type light-emitting unit interface layer 402 having a crosslinked structure on the surface have enhanced molecular bonds in each layer, so that elution to other laminated films formed on the surface It has a function of preventing diffusion or impurity intrusion from the laminated film. Therefore, the energy levels of the n-type light emitting unit interface layer 401 and the p-type light emitting unit interface layer 402 do not vary depending on the interface state. Therefore, the effect of reducing the excess voltage ΔV due to the adoption of the above-described conductive polymer in the light emitting unit interface layer 40 is not affected by the interface state.

  The light emitting unit 30-k (k is a natural number of 2 to n) is formed on the surface of the light emitting unit interface layer 40- (k-1), includes at least one light emitting layer, and holes and electrons are injected. By being recombined, an excited state is generated and has a function of emitting light. The layer configuration and material of the light emitting unit 30-k are the same as those of the light emitting unit 30-1.

  The light emitting unit interface layer 40-k (k is a natural number of 2 to n) is formed on the surface of the light emitting unit 30-k and has a function of supplying carriers to the light emitting unit 30-k and the light emitting unit 30- (k + 1). . The layer configuration and material of the light emitting unit interface layer 40-k are the same as those of the light emitting unit 40-1.

  The cathode 50 is formed on the surface of the light emitting unit 30-n, and n light emitting units 30-1, 30-2,... 30-n and (n-1) light emitting unit interface layers 40-1, A negative external voltage is applied to 40-2, ... 40- (n-1). Thereby, electrons are injected from the cathode 50 into the n light emitting units 30-1, 30-2,... 30-n. Then, electrons and holes described above are recombined in the n light emitting units 30-1, 30-2,... 30-n, so that the n light emitting units 30-1, 30-2,. -An excited state is generated within 30-n, and emitted light is extracted outside. In addition, in the case of an electrode on the side from which light emitted inside the device is extracted, it is necessary to be transparent to the light. The electrode material is the same as that of the anode 20.

  With the above structure, holes and electrons having a sufficient energy level in the light emitting unit interface layer 40 are injected into the light emitting unit 30, so that the organic EL element has high light emission efficiency and low power consumption by wet film formation. Is realized.

  In addition, about a concrete crosslinked structure and its method, it demonstrates with the manufacturing method of the organic EL element mentioned later.

  FIG. 4 is a structural sectional view of a tandem organic EL element showing a modification according to the embodiment of the present invention. The tandem organic EL element 2 in the figure includes a substrate 10, an anode 20, n light emitting units 31-1, 31-2, ..., and 31-n, and (n-1) light emitting units. Interface layers 41-1, 41-2,..., 31- (n-1) and a cathode 50 are provided. Compared with the organic EL element according to the embodiment described in FIG. 1, the tandem organic EL element 2 in FIG. 1 has the same configuration of each layer constituting the organic EL element. The positional relationship is different. Description of the same points as those of the organic EL element shown in FIG. 1 is omitted, and only different points will be described below.

  When the cathode 50 is formed on the surface of the substrate 10 and is an electrode on the side from which the light emitted inside the element is extracted, it needs to be transparent to the light.

  The light emitting unit 31-1 is formed on the surface of the cathode 50, includes at least one light emitting layer, and emits light when holes and electrons are injected. FIG. 5 is an example of a cross-sectional view of the structure of the light emitting unit. The light emitting unit 31 in the figure includes an electron transport layer 313, a light emitting layer 312 and a hole transport layer 311 from the substrate side.

  The light emitting unit interface layer 41-1 is formed on the surface of the light emitting unit 31-1. FIG. 6 is an example of a structural cross-sectional view of the light emitting unit interface layer. The light emitting unit interface layer 41 in the figure includes a p-type light emitting unit interface layer 402 and an n-type light emitting unit interface layer 401 on the surface thereof.

  The light emitting unit 31-k (k is a natural number of 2 to n) is formed on the surface of the light emitting unit interface layer 41- (k-1), includes at least one light emitting layer, and holes and electrons are injected. Emits light. The layer configuration and material of the light emitting unit 31-k are the same as those of the light emitting unit 31-1.

  The light emitting unit interface layer 41-k (k is a natural number of 2 to n) is formed on the surface of the light emitting unit 31-k. The layer configuration and material of the light emitting unit interface layer 41-k are the same as those of the light emitting unit 41-1.

  When the anode 20 is formed on the surface of the light emitting unit 31-n and is an electrode on the side from which the light emitted inside the element is extracted, the anode 20 needs to be transparent to the light. The electrode material is the same as that of the cathode 50.

  Also in the organic EL element showing the modification according to the above embodiment, there are the same effects as those of the organic EL element of the embodiment, and holes and electrons having sufficient energy levels in the light emitting unit interface layer are generated. Since it is injected into the light emitting unit, an organic EL element having high luminous efficiency and low power consumption by wet film formation is realized.

  In addition, each light emitting unit of the organic EL element described in the embodiment and the modification thereof may be configured with the same structure and material, or may be configured with different structures or materials. For example, like the two-stage tandem organic EL element 3 shown in FIG. 7, a light emitting unit that emits light blue is used for the first light emitting unit 30-1 from the substrate side. By using a light emitting unit that emits orange light for the light emitting unit 30-2 of the eye, white light emission in which both light emissions are superimposed is obtained. White light emission is important for lighting and backlighting applications. In these applications, color rendering is important, and in order to improve this, it is effective to superimpose three light emitting units of red, blue, and green as a three-stage tandem organic EL element.

Next, the manufacturing method of the tandem organic EL element of this invention is demonstrated with reference to drawings.
FIG. 8 is an example of a structural cross-sectional view of the organic EL element according to the embodiment of the present invention. The tandem organic EL element 4 in FIG. 1 includes a substrate 10, an anode 20, a cathode 50, a hole transport layer 301, two light emitting layers 302-1 and 302-2, and an n-type light emitting unit interface layer 401. And a p-type light emitting unit interface layer 402. The functions and materials used in each layer are the same as in the embodiment.

  The layer configuration is, in order from the substrate 10, the anode 20, the hole transport layer 301, the light emitting layer 302-1, the n-type light emitting unit interface layer 401, the p-type light emitting unit interface layer 402, the light emitting layer 302-2, and the cathode 50. .

  Here, the n-type light emitting unit interface layer 401 and the p-type light emitting unit interface layer 402 may be a single layer or a plurality of layers. As described above, the light emitting unit interface layer is manufactured by a wet film forming method using a solution in which a conductive organic polymer material is dispersed or dissolved. As a result, advantages such as an increase in area and a reduction in material loss can be utilized, and the disadvantages of a tandem structure type organic EL element generally inferior in productivity can be overcome.

  The wet film-forming method uses a solvent such as water or an organic solvent to form a film by various printing methods such as spray, dip, nozzle jet, spin coating, bar coating, letterpress printing, intaglio printing, and screen printing. And a manufacturing method for obtaining a predetermined thin film by removing the solvent.

  A more preferable manufacturing method of the tandem organic EL element using the conductive organic polymer of the present invention is a method of forming all organic layers by a wet film forming method. With this manufacturing method, it is not necessary to use a vacuum process for forming the organic layer, so that the manufacturing time and the manufacturing cost are drastically improved.

  In this example, an example of a manufacturing method in the case where the hole transport layer 301 to the light emitting layer 302-2 are formed by a wet film forming method out of the layer configuration of the tandem organic EL element shown in FIG. This will be described below.

  FIG. 9 is a process diagram for explaining a method of manufacturing a tandem organic EL element using a conductive polymer according to an embodiment of the present invention.

  First, a conductive layer made of indium-tin oxide is formed on the soda glass substrate 11 by sputtering to a thickness of 100 nm. The indium-tin oxide is patterned into an electrode shape using a photolithography process to form the anode 20. Then, surface treatment is performed by exposing the anode 20 made of indium-tin oxide to UV-ozone for 2 minutes (step (a)).

  Next, the following formula is applied to the surface of the surface-treated anode 20:

で示される化合物ＰＥＤＯＴ（Ｐｏｌｙ（３、４−ｅｔｈｙｌｅｎｅｄｉｏｎｘｙｔｈｉｏｐｈｅｎｅ））とＰＳＳ（Ｐｏｌｙ（ｓｔｙｒｅｎｅｓｕｌｆｏｎａｔｅ））との混合物からなる正孔輸送層３０１をスピンコート法により５０ｎｍ製膜し、ホットプレート上で２００℃、５分間ベークする（工程（ｂ））。

A hole transport layer 301 composed of a mixture of the compound PEDOT (Poly (3,4-ethylenedoxythiophene)) and PSS (Poly (styrenesulfonate)) represented by the following formula: Bake for 5 minutes (step (b)).

  Then the following formula

で示される化合物ＭＥＨ−ＰＰＶと、２０重量％比のジペンタエリスリトールヘキサアクリレートのトルエン溶液とを調整し、スピンコート法により５０ｎｍの発光層前駆体３０２Ａを製膜する（工程（ｃ））。

And a toluene solution of dipentaerythritol hexaacrylate in a ratio of 20% by weight is prepared, and a 50 nm light emitting layer precursor 302A is formed by spin coating (step (c)).

  Then, by heating on a hot plate at 200 ° C. for 30 minutes, a light emitting layer 302-1 having at least a surface cross-linking reaction is formed (step (d)).

  Step (d) is a cross-linking reaction step in which the light emitting layer precursor 302A is converted into a desired conductive polymer by thermal energy. This method is particularly beneficial when the desired conductive polymer is insoluble in the solvent while the precursor is soluble in the solvent. The cross-linking reaction in this step is the following formula

で示されるジペンタエリスリトールヘキサアクリレートであり、発光機能を有するＥＬポリマーであるＭＥＨ−ＰＰＶは架橋反応をしていない。ジペンタエリスリトールヘキサアクリレートは、二重結合部（式中の→部）にエーテル結合（酸素原子による有機基同士の結合）を作りながら、架橋反応を進行させ、複雑な網目状構造をつくる。この網目状構造とＥＬポリマーが絡みあうことによって、溶液への溶解性が低い発光層３０２−１が形成される。

MEH-PPV, which is an EL polymer having a light emitting function, is not subjected to a crosslinking reaction. Dipentaerythritol hexaacrylate forms a complex network structure by advancing a crosslinking reaction while forming an ether bond (bonding between organic groups by oxygen atoms) at a double bond part (→ part in the formula). When the network structure and the EL polymer are entangled with each other, the light emitting layer 302-1 having low solubility in a solution is formed.

  Then the following formula

で示されるｎ型高分子と、２０重量％のジペンタエリスリトールヘキサアクリレートと１０重量％のバリウムアセトアセテートからなる混合物のトルエン溶液とを調整し、スピンコート法により２０ｎｍのｎ型発光ユニット界面層前駆体４０１Ａを製膜する（工程（ｅ））。ここで、バリウムアセトアセテートはｎ型ドーパントとして機能する。

And a toluene solution of a mixture of 20% by weight of dipentaerythritol hexaacrylate and 10% by weight of barium acetoacetate, and a 20 nm n-type light emitting unit interface layer precursor by spin coating. The body 401A is formed into a film (step (e)). Here, barium acetoacetate functions as an n-type dopant.

  Then, by heating on a hot plate at 200 ° C. for 30 minutes, an n-type light emitting unit interface layer 401 whose surface is crosslinked is formed (step (f)). In this step, as in the step described in step (d), the network structure formed by the crosslinking reaction with dipentaerythritol hexaacrylate and the n-type polymer are entangled with each other, so that the solubility in the solution is increased. A low n-type light emitting unit interface layer 401 is formed.

  Then the following formula

で示されるｐ型高分子と、２０重量％のジペンタエリスリトールヘキサアクリレートと１０重量％のヨウ素からなる混合物のトルエン溶液とを調整し、スピンコート法により２０ｎｍのｐ型発光ユニット界面層前駆体４０２Ａを製膜する（工程（ｇ））。ここで、ヨウ素はｐ型ドーパントとして機能する。

And a toluene solution of a mixture of 20% by weight of dipentaerythritol hexaacrylate and 10% by weight of iodine, and a 20 nm p-type light emitting unit interface layer precursor 402A by spin coating. Is formed (step (g)). Here, iodine functions as a p-type dopant.

  Then, by heating on a hot plate at 200 ° C. for 30 minutes, the p-type light emitting unit interface layer 402 whose surface has undergone a crosslinking reaction is formed (step (h)). In this step, as in the step described in step (d), the network structure formed by the crosslinking reaction with dipentaerythritol hexaacrylate and the p-type polymer are entangled with each other, so that the solubility in the solution is increased. A low p-type light emitting unit interface layer 402 is formed.

  Then the following formula

で示される化合物ＭＥＨ−ＰＰＶからなる発光層３０２−２をスピンコート法により５０ｎｍ製膜し、ホットプレート上で１５０℃、１０分間ベークする（工程（ｉ））。

A light emitting layer 302-2 made of the compound MEH-PPV represented by the following formula is formed by spin coating to a thickness of 50 nm and baked on a hot plate at 150 ° C. for 10 minutes (step (i)).

  Finally, barium 5 nm and aluminum 200 nm are vapor-deposited on the surface of the light emitting layer 302-2 to form a cathode 50 having a predetermined pattern shape (step (j)).

  The atmosphere from step (a) to step (j) is controlled such that the water and oxygen concentration is 1000 ppm or less, and all the solutions for spin coating are also controlled so that the water and oxygen concentration is 1000 ppm or less. . Thereby, since the dopant in the step (e) and the step (g) is avoided from being deteriorated by water or oxygen present in the solvent and the environment, an organic EL device having excellent production efficiency and device life can be obtained. it can.

  Furthermore, it is preferable that the atmosphere in the above process is controlled so that the water and oxygen concentrations are 1 ppm or less, and all the solutions for spin coating are also controlled so that the water and oxygen concentrations are 1 ppm or less. This greatly improves production efficiency and device life.

  In steps (e) and (g), the n-type light-emitting unit interface layer 401 and the p-type light-emitting unit interface layer 402 are exposed to halogen or metal vapor after forming a solution containing no dopant. Alternatively, the production method of forming a conductive polymer may be used.

  Moreover, although the setting temperature of the crosslinking reaction in the step (d), the step (f), and the step (h) is 200 ° C., the crosslinking reaction is advanced by adjusting the heating time if it is 100 ° C. or more. Can do.

  In addition, the crosslinking reaction in the step (d), the step (f), and the step (h) proceeds not only by supplying heat energy as in the above-described process but also by supplying light energy. The supply conditions of light energy are preferably ultraviolet light having a wavelength of 200 to 450 nm, irradiation power of 10 to 1000 W, and irradiation time of 1 to 600 seconds. Thereby, depending on the adjustment of conditions, it is possible to cause only the outermost surface to undergo a crosslinking reaction, and structural change or alteration of the organic light-emitting body itself due to the promotion of the crosslinking reaction is unlikely to occur. Further, alteration due to excessive energy supply to other layers already formed is avoided. Therefore, the productivity can be stabilized with the yield improvement.

  The cross-linking reaction in the step (d), the step (f), and the step (h) is performed by the cross-linking reaction of dipentaerythritol hexaacrylate that is a mixture of the light emitting layer 302, the n-type without the EL polymer cross-linking. The light emitting unit interface layer 401 and the p-type light emitting unit interface layer 402 have a crosslinked structure. In contrast, the EL polymer itself represented by the formulas [Chemical Formula 1] to [Chemical Formula 4] having a light emitting function and a carrier generating and transporting function is not a crosslinking reaction by a mixture such as dipentaerythritol hexaacrylate. A structure having a group and a crosslinking reaction and a production method may be taken.

  In the method for manufacturing the organic EL element shown in Embodiment 2, the tandem structure is formed by the two-stage light-emitting unit including the light-emitting layer 302. However, the number of light-emitting units is three or more. However, the manufacturing process of each layer is the same. Here, the layers that require the crosslinking reaction process are the light emitting layer 302, the n-type light emitting unit interface layer 401, and the p-type light emitting unit interface layer 402 in each stage. As the number of stages increases, the current value required for a predetermined amount of light emission decreases, so that the lifetime of the element is promoted.

  Not only the light emitting layer 302, the n-type light emitting unit interface layer 401, and the p-type light emitting unit interface layer 402 are subjected to a cross-linking reaction, but also a cross-linking reaction process is performed on all the layers formed of wet-formed organic substances. Also good. In this case, not only the effects of high light emission efficiency and low power consumption due to improved energy levels and carrier controllability in the light emitting unit interface layer 40, but also an improvement in manufacturing yield are expected.

With the above manufacturing method, all layers having organic polymers are wet-formed, so that the area of the device can be increased and the production cost can be reduced. In addition, since a cross-linking reaction step is added after each step of forming the light emitting unit interface layer and the light emitting layer, elution and diffusion at each interface are prevented, and the light emitting unit interface layer having a conductive organic polymer The reduction of the excess voltage ΔV, which is an advantage of the above, is achieved. As a result, holes and electrons having sufficient energy levels in the light emitting unit interface layer are efficiently injected into the light emitting unit, so that an organic EL element having high light emission efficiency and low power consumption by wet film formation is realized. The

  The electrode on the substrate for the organic EL element used in the present invention may be a cathode or an anode. This electrode may be uniformly formed on the entire surface or most of the substrate. In this case, since large area light emission can be obtained, it can be used for applications such as illumination. Or this electrode may be patterned so that a specific figure and a character can be displayed. In this case, a characteristic pattern of light emission can be obtained, which can be used for advertising display. Alternatively, this electrode may be formed on a simple matrix. In this case, it can be used for applications such as a passive drive display. Alternatively, the electrode may be formed on the substrate on which the transistor array is arranged so that electrical connection can be obtained in a form corresponding to the transistor array. In this case, as represented by the TV described in FIG. 10, it can be used for applications such as an active drive display.

  Further, in the organic EL device of the present invention, either the anode or the cathode needs to be transparent in order to extract emitted light to the outside, but either of the organic EL of the present invention may be transparent, Both may be transparent. In the case where both are transparent and the substrate is a transparent substrate such as a glass substrate, light emission can be emitted from both the substrate surface and the opposite side of the substrate, and the effect of seeing the opposite side of the substrate through the organic EL element can be obtained.

  As mentioned above, although the organic EL element of this invention and its manufacturing method were demonstrated based on embodiment, this invention is not limited to these embodiment. Unless it deviates from the meaning of the present invention, various modifications conceived by those skilled in the art have been made in the present embodiment, and forms constructed by arbitrarily combining components in different embodiments are also within the scope of the present invention. included.

  The present invention is particularly useful for a display device or an optical device using an organic EL element as a light source, or a backlight of a liquid crystal display, and is particularly suitable as an organic EL element that requires long life, low power consumption, and low price. is there.

It is a structure sectional view of the organic EL element which has a tandem type in an embodiment of the invention. It is an example of the structure sectional view of a light emitting unit. It is an example of structure sectional drawing of a light emitting unit interface layer. It is a structure sectional view of the organic EL element which shows the 1st modification concerning an embodiment of the invention. It is an example of the structure sectional view of a light emitting unit. It is an example of structure sectional drawing of a light emitting unit interface layer. It is a structural sectional view of a two-stage tandem organic EL device. It is an example of the structure sectional view of the organic EL element concerning an embodiment of the invention. It is process drawing explaining the manufacturing method of the tandem-type organic EL element using the conductive polymer in embodiment of this invention. It is an external view of TV using the organic EL element of this invention. It is structure sectional drawing of the organic EL element which has the conventional tandem structure. It is structure sectional drawing of the light emission unit of the organic EL element which has the conventional tandem structure. It is the figure where the organic EL element which has a non-tandem structure with a single light emission unit was connected to the direct-current voltage source. It is a schematic diagram of the energy level when the organic EL element having a non-tandem structure is not connected to a power source. It is a schematic diagram of an energy level when the organic EL element which has a non-tandem structure is short-circuited. It is a schematic diagram of an energy level when an external electric field is applied to an organic EL element having a non-tandem structure. FIG. 2 is a diagram in which two non-tandem organic EL elements connected in series are connected to a DC voltage source. It is a schematic diagram of the energy level when two organic EL elements having a non-tandem structure connected in series are not connected to a power source. It is a schematic diagram of the energy level when two organic EL elements having a non-tandem structure connected in series are short-circuited. It is a schematic diagram of the energy level when an external electric field is applied to two organic EL elements having a non-tandem structure connected in series. It is the figure where the organic EL element of the tandem structure provided with the light emission unit interface layer was connected to the DC voltage source. It is a schematic diagram of an energy level when the organic EL element of a tandem structure provided with a light emitting unit interface layer is not connected to a power source. It is a schematic diagram of an energy level when the organic EL element of a tandem structure provided with a light emitting unit interface layer is short-circuited. It is a schematic diagram of an energy level when an external electric field is applied to an organic EL element having a tandem structure including a light emitting unit interface layer.

Explanation of symbols

1, 2, 3, 4, 820 Tandem organic EL element 10, 801 Substrate 11 Soda glass substrate 20, 802, 802-1, 802-2 Anode 30, 30-1, 30-2, 30-k, 30- n, 31, 31-1, 31-2, 31-k, 31-n, 803, 803-1, 803-2, 803-n Light emitting unit 40, 40-1, 40-2, 40-k, 40 -(N-1), 41, 41-1, 41-2, 41-k, 41- (n-1), 804, 804-1, 804-2, 804- (n-1) Light emitting unit interface layer 50, 805, 805-1, 805-2 Cathode 301, 311, 803A Hole transport layer 302, 302-1, 302-2, 302A, 312, 803B, 803B-1, 803B-2 Light emitting layer 303, 313, 803C electron transport layer 401 n-type Optical unit interface layer 401A n-type light emitting unit interface layer precursor 402 p-type light emitting unit interface layer 402A p-type light emitting unit interface layer precursor 810, 810-1, 810-2 Organic EL element 804A n-type interface layer 804B p-type interface Layer 901 DC voltage source

Claims (10)

A method for producing an organic electroluminescence device, comprising:
A first electrode forming step of forming a first electrode on the substrate;
A first light emitting unit forming step of forming a first light emitting unit having at least one first organic light emitting layer on a surface of the first electrode;
A first interface layer forming step of forming a precursor containing a conductive organic polymer having a molecular weight of 1000 or more on the surface of the first light emitting unit by a wet film forming method;
A first interface layer crosslinking step for forming a light emitting unit interface layer having at least a surface intermolecular or intramolecularly crosslinked by crosslinking reaction of the precursor formed by the wet film formation method;
A second light emitting unit forming step of forming a second light emitting unit comprising at least one second organic light emitting layer on the surface of the light emitting unit interface layer;
And a second electrode forming step of forming a second electrode on the second light emitting unit. A method of manufacturing an organic electroluminescence element, comprising: In the first light emitting unit formation step,
A first light-emitting layer forming step of forming a precursor containing a conductive organic polymer having a molecular weight of 1000 or more by a wet film forming method;
A first light-emitting layer cross-linking step that forms a first organic light-emitting layer having at least a surface intermolecularly or intramolecularly cross-linked by cross-linking the precursor formed by the wet film forming method. The manufacturing method of the organic electroluminescent element of Claim 1. In the first interface layer crosslinking step,
The light emitting unit interface layer is of one conductivity type,
Furthermore, after the first interface layer crosslinking step and before the second light emitting unit formation step,
A second interface layer forming step of forming a precursor containing a conductive organic polymer having a molecular weight of 1000 or more on the surface of the light-emitting unit interface layer of the one conductivity type by a wet film forming method;
A second interfacial layer cross-linking step of forming a reverse conductivity type light emitting unit interfacial layer having at least a surface intermolecularly or intramolecularly cross-linked by a cross-linking reaction of the precursor formed by the wet film-forming method. The manufacturing method of the organic electroluminescent element of Claim 1 or 2 characterized by these. The layer formed with the organic substance formed between the first electrode and the second electrode is formed by the wet film forming method. The manufacturing method of the organic electroluminescent element of description. 5. The method of manufacturing an organic electroluminescence element according to claim 4, wherein a cross-linking reaction is performed on at least the surface of the layer formed of the organic material each time the layer formed of the organic material is formed. Film formation by the wet film formation method is
It is carried out by spraying, applying or printing a solution in which the precursor containing the conductive organic polymer is dispersed or dissolved in an atmosphere of an inert gas whose water content and oxygen content are both 1000 ppm or less. ,
The method for producing an organic electroluminescent element according to any one of claims 1 to 5, wherein the solution has a water content and an oxygen content of 1000 ppm or less. In the crosslinking reaction,
The organic electroluminescence device according to any one of claims 1 to 6, wherein the surface of the precursor is intermolecularly or intramolecularly crosslinked by maintaining the temperature of the substrate at 100 ° C or higher. Production method. In the crosslinking reaction,
The surface of the precursor is intermolecularly or intramolecularly crosslinked by irradiating ultraviolet light having a wavelength of 200 to 450 nm with an irradiation power of 10 to 1000 W and an irradiation time of 1 to 600 seconds. The manufacturing method of the organic electroluminescent element of any one of Claims 1-6. The precursor containing the conductive organic polymer,
The method for producing an organic electroluminescent element according to claim 1, comprising a conductive polymer into which a substituent that crosslinks between molecules or intramolecularly by heat or light energy is introduced. A substrate,
A first electrode formed on the substrate;
A first light emitting unit including at least one first organic light emitting layer formed on the surface of the first electrode and emitting light by injecting carriers;
A light-emitting unit interface layer formed of a conductive organic polymer having a molecular weight of 1000 or more on the surface of the first light-emitting unit and supplying carriers to the organic light-emitting layer;
A second light emitting unit comprising at least one second organic light emitting layer formed on the surface of the light emitting unit interface layer and emitting light by carrier injection;
A second electrode formed on the second light emitting unit,
The light emitting unit interface layer is
The conductive organic polymer precursor formed by the wet film forming method undergoes a cross-linking reaction, so that at least each surface is intermolecular or intramolecularly cross-linked, a p-type conductive organic polymer layer and an n-type An organic electroluminescence element comprising: a conductive organic polymer layer of:

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