JP2014032851A - Organic optical device and organic electronic device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an organic optical device capable of effectively controlling light propagation at a low cost without damaging other organic layers by controlling the refractive index of an organic film and using a combination of organic film layers having refractive indexes largely different from each other; and an organic electronic device using the organic optical device.SOLUTION: An organic optical device includes at least one pair of laminated two layers of organic films having refractive indexes different from each other while the difference of refractive indexes of the two layers of organic films is 0.5 or more. The organic optical device is applied for an organic electronic device.

Description

  The present invention relates to an organic optical device made of an organic material, and an organic electronic device such as an organic electroluminescence device (hereinafter, abbreviated as organic EL) or an organic thin film solar cell formed using the organic optical device.

In recent years, in the field of electronic devices, research and development of organic electronic devices such as organic ELs, organic lasers, and organic thin-film solar cells using organic semiconductor materials have been actively conducted with the aim of reducing power consumption, weight reduction, and flexibility. Yes.
In such an organic electronic device, the refractive index of the organic semiconductor thin film is conventionally considered to be about 1.7 to 1.8, and the refractive index is adjusted by the organic film itself, There was no idea of controlling light propagation. For this reason, the control of light propagation has been performed exclusively by applying an inorganic material layer such as a metal, an insulating derivative, or a conductive metal oxide to the outside of the stacked organic film.

  However, in recent years, it has been found that the refractive index of an organic film varies greatly depending on the material, and a large birefringence may occur due to the molecular orientation of the organic material in the film, resulting in a large refractive index for normal incident light (non- Patent Document 1).

On the other hand, the concept of controlling the refractive index of a polymer material has been conventionally employed in plastic optical fibers (see Non-Patent Document 2). However, it has not been considered to form a thin film with a controlled refractive index using an organic semiconductor material.
In addition, although an example using an insulating polymer material has been reported in a multilayer mirror, there is no example composed mainly of an organic semiconductor material, and it can be said that the refractive index difference between layers is sufficiently large. It was not a thing.

  Thus, conventionally, there has been no optical device whose refractive index is controlled by an organic semiconductor material.

D.Yokoyama, J.Mater.Chem., 2011, 21, p.19187-19202 Yasuhiro Koike, “Optical Properties of Polymers”, Kyoritsu Shuppan, 1994

  Conventionally, when controlling the light propagation by depositing an inorganic material layer, the process cost is high, and it is difficult to achieve both proper conductivity and refractive index. It had problems such as easy damage. Further, since the refractive index inside the device cannot be directly adjusted, there is a problem that it is difficult to perform effective light propagation control.

  Accordingly, the present inventors have repeatedly studied refractive index control by an organic film that is easy to form at low temperature and is excellent in terms of process cost, film surface smoothness, and the like. The present inventors have found a technique that can suitably control light propagation in an electronic device.

  That is, the present invention controls the refractive index of an organic film and uses an organic film layer having a large refractive index difference in combination to effectively propagate light at low cost without damaging other organic layers. An object of the present invention is to provide an organic optical device that can be controlled and an organic electronic device using the same.

The organic optical device according to the present invention includes at least one set in which two layers of organic films having different refractive indexes are stacked, and a difference in refractive index between the two layers of organic films is 0.5 or more. To do.
By laminating such a high refractive index layer and a low refractive index layer, effective light propagation control by an organic film becomes possible, and it can be applied to various optical property control in an organic optical device.

In the organic optical device, it is preferable that the optical film thickness of at least one of the two organic films is ¼ of the wavelength of incident light with respect to the organic thin film.
By using such a film thickness, it becomes possible to make the most of the effect of optical interference and control light propagation more effectively.

  The organic optical device as described above can be suitably applied to a multilayer mirror such as a distributed Bragg reflector (hereinafter abbreviated as DBR).

  Further, by configuring the organic film with an organic semiconductor material, it is possible to configure an organic optical device having conductivity or an organic optical device having a function as a semiconductor that responds to light or emits light.

ADVANTAGE OF THE INVENTION According to this invention, the organic electronic device using the above organic optical devices can be provided.
By applying the organic optical device, it is possible to configure an organic electronic device whose light propagation is effectively controlled at low cost without damaging other organic layers.

According to the organic optical device of the present invention, the refractive index difference of a plurality of layers of organic films for light propagation control can be increased to 0.5 or more, which is generally known in the field of plastic optical fibers. It can be made larger than the difference in refractive index of a high polymer material. Further, the organic film can be formed by vacuum deposition, and a film having an arbitrary thickness excellent in smoothness can be formed.
Therefore, according to the present invention, it is possible to configure an organic optical device in which light propagation is effectively controlled at low cost without damaging other organic layers.
The organic film can be configured to have conductivity, and further to have a function as a semiconductor that responds to light or emits light. Therefore, the organic optical device according to the present invention can be widely applied to various organic electronic devices using organic semiconductors.

Is a graph showing the refractive index evaluation results at each wavelength for co-deposited film and BDAVBi between PBD and C ₂₄ F _50. (A), (b) is a graph which shows the simulation result of the reflectance with respect to each wavelength light of predetermined | prescribed DBR, (b) is expanded about the reflectance of 0.88 or more of (a). It is a graph which shows the calculated value and measured value of the reflectance with respect to each wavelength light of DBR which concerns on an Example. It is a graph which shows the evaluation result of the reflection angle dependence of the reflectance with respect to each wavelength light of DBR which concerns on an Example. It is the schematic sectional drawing which showed the layer structure of organic EL which concerns on a 1st embodiment. It is the schematic sectional drawing which showed the layer structure of organic EL which concerns on a 2nd embodiment. It is the schematic sectional drawing which showed the layer structure of organic EL which concerns on a 3rd embodiment. It is the schematic sectional drawing which showed the layer structure of organic EL which concerns on a 4th embodiment. It is the schematic sectional drawing which showed the layer structure of organic EL which concerns on a 5th embodiment. It is the schematic sectional drawing which showed the layer structure of organic EL which concerns on a 6th embodiment. It is the schematic sectional drawing which showed the layer structure of the organic thin film solar cell which concerns on a 7th embodiment. It is the schematic sectional drawing which showed the layer structure of the organic thin-film solar cell concerning an 8th embodiment. It is the schematic sectional drawing which showed the layer structure of the organic thin-film solar cell which concerns on a 9th embodiment.

Hereinafter, the present invention will be described in more detail.
The organic optical device according to the present invention includes at least one set in which two layers of organic films having different refractive indexes are stacked, and the difference in refractive index between the two layers of organic films is 0.5 or more. It is a feature.
Of the materials constituting each layer of a general organic semiconductor device, the material having the largest refractive index as a light propagating material is ITO (refractive index for visible light: about 2.0), while the refractive index. Is the glass used as a substrate (refractive index with respect to visible light: about 1.5). Therefore, since the difference in refractive index between ITO and the glass substrate is about 0.5 in the visible region, the difference in refractive index between adjacent organic films in the laminated structure of organic films is set to 0.5 or more. It is possible to adjust the difference in refractive index with any of the layers, and to effectively control light propagation.
Further, when forming a multilayer mirror, it is important to reflect at least one wavelength region of at least one of the three visible light primary colors (BGR) from the viewpoint of application. For this purpose, the refractive index difference between adjacent organic films in the multilayer film needs to be at least 0.5.

  In the organic optical device, from the viewpoint of making the best use of the effect of optical interference and more effectively controlling light propagation, the optical film thickness of at least one of the two organic films constituting the laminated structure Is preferably ¼ of the wavelength λ of incident light on the organic thin film.

The organic optical device can be applied not only to the multilayer mirror as described above, but also to organic electronic devices such as organic EL and organic thin film solar cells by configuring the organic film with an organic semiconductor material. be able to.
The organic electronic device referred to in the present invention is an electronic device having a pair of electrodes on a substrate and at least one organic layer between the electrodes, and is a generic term for organic EL, organic thin-film solar cells, and the like. Used as
In the organic electronic device as described above, since an organic film can be formed by vapor deposition, the film forming process is simple, the film thickness can be easily controlled, and further, no damage is caused to the lower organic layer. And, it has an advantage that a desired organic film can be laminated.

  Specifically, the refractive index of the organic material constituting the organic film can be adjusted as follows. In addition, the compound shown below is a representative example and this invention is not limited only to these compounds.

  Among hole transport materials generally used in organic electronic devices, examples of high refractive index materials include the following compounds (BDAVBi, TTPPA, BT-DDP). Refractive indexes for normal incident light of 532 nm, which is the wavelength of BDAVBi, TTPPA, and BT-DDP green lasers, are 1.99, 2.01, and 2.03, respectively. BDAVBi also functions as a p-type semiconductor.

  Moreover, as a high refractive index electron transporting material and typical examples, the following compounds (Bpy-OXD, BTB, B4PyMPM) can be given. The refractive indices of Bpy-OXD, BTB, and B4PyMPM for vertically incident light with a wavelength of 532 nm are 1.86, 1.87, and 1.84, respectively.

By mixing such an organic material having a relatively high refractive index with a compound containing a large amount of sulfur atoms having a large atomic refraction, for example, the compound (BTBBTT) shown below, the conductivity of the organic material is increased. Without losing the refractive index, the refractive index of the organic film containing the high refractive index organic material can be further increased. Specifically, the film can be easily formed by co-evaporation.
BTBBTT alone forms a polycrystalline thin film with large surface irregularities, but it can be made a highly smooth film by forming a co-deposited film with a different material. BTBBBTT also functions as a p-type semiconductor by co-evaporation with BDAVBi or the like which is a hole transporting material.

  On the other hand, a representative example of the low refractive index hole transporting material is a compound (TAPC) shown below. The refractive index of TAPC for vertically incident light with a wavelength of 532 nm is 1.68.

  Moreover, as a typical example of an electron transport material having a low refractive index, the following compounds (PBD, OXD7) can be given. The refractive indices of PBD and OXD7 for vertically incident light with a wavelength of 532 nm are 1.67 and 1.64, respectively.

By mixing such an organic material having a relatively low refractive index with a compound containing a large amount of fluorine atoms having small atomic refraction, for example, the compound (C ₂₄ F ₅₀ ) shown below, Without losing conductivity, the refractive index of the organic film containing the low refractive index organic material can be further reduced. Specifically, the film can be easily formed by co-evaporation.
C ₂₄ F ₅₀ alone forms a polycrystalline thin film with large surface irregularities, but can be made a highly smooth film by forming a co-deposited film with a different material. C ₂₄ F ₅₀ also functions as an n-type semiconductor by co-evaporation with PBD or the like which is an electron transporting material.

FIG. 1 is a graph of the refractive index at each wavelength obtained by multi-incidence angle spectroscopic ellipsometry analysis for a co-deposited film of PBD and C ₂₄ F ₅₀ which is a compound having a function of reducing the refractive index. Indicates. This graph also shows the refractive index of the BDAVBi film with respect to the normal incident light.
The refractive index of PBD for vertically incident light with a wavelength of 532 nm is 1.67, but the refractive index decreases as the mixing ratio of C ₂₄ F ₅₀ by co-evaporation increases, and the weight ratio of PBD: C ₂₄ F ₅₀ is 20:80. In this case, the refractive index was 1.41, and the refractive index difference from the BDAVBi film was 0.58.
As described above, the refractive index difference between adjacent organic films can be adjusted to 0.5 or more by mixing predetermined additives.

Of the multilayer mirrors, the DBR is a light mirror that forms a reflecting mirror by laminating layers with different refractive indexes whose thickness is 1/4 of the incident light wavelength on a substrate such as glass. The Bragg reflection due to the effect strengthens the reflected waves in each layer and a high reflectance can be obtained, but a good DBR can also be produced by two organic film layers having different refractive indexes as described above. it can.
For example, on a quartz glass substrate or ITO glass substrate, the above-mentioned BDAVBi vapor-deposited film (high refractive index layer (H layer); refractive index n _H = 1.99, film) with respect to vertical incident light having a wavelength (λ) of 532 nm Thickness d _H = λ / (4n _H ) = 66.7 nm) and PBD: C ₂₄ F ₅₀ (20:80) co-deposited film (low refractive index layer (L layer); refractive index n _L = 1.41, d By stacking a set of _L = λ / (4n _L ) = 94.1 nm), the difference in refractive index Δn between the two is as large as 0.58. Therefore, a stacked structure of (HL) ^q H (q: the number of sets) A DBR made of an organic semiconductor including

FIG. 2 shows a simulation calculation result of the reflectance for each wavelength light of the DBR. FIG. 2B is an enlarged view of the reflectance of 0.88 or more in FIG.
As can be seen from the simulation calculation results shown in FIG. 2, the reflectance increases as the number q of stacked layers increases. When q = 8, the reflectance is 99.4%, and a mirror having a very high reflectance is obtained. Can do.

As shown in the examples below, it was confirmed that a DBR having a high reflectivity and a high bandwidth substantially equal to the calculated value and having a small reflection angle dependency was obtained.
Therefore, by using such a DBR, it is possible to construct a device structure of an organic laser such as an organic DBR laser.

  Next, various embodiments of the laminated structure of the organic electronic device to which the organic optical device as described above is applied will be shown. Note that the organic electronic device according to the present invention is not limited to the following embodiments.

(First embodiment)
FIG. 5 shows an example of a configuration in which the organic optical device according to the present invention is applied to a top emission type organic EL.
The organic EL shown in FIG. 5 is a known top emission type organic EL structure 2 in which a metal electrode 23, an organic layer 22 including a light emitting layer, a transparent (or translucent) electrode 21 and the like are sequentially laminated on a substrate 3. The multilayer mirror 1 in which the high refractive index organic film 11 and the low refractive index organic film 12 are alternately and repeatedly stacked a plurality of times is disposed on the transparent electrode 21. That is, the multilayer mirror 1 which is an organic optical device according to the present invention is provided outside the organic EL structure 2. For this reason, the multilayer mirror 1 is not required to have conductivity.
The organic EL having such a configuration can improve the light extraction efficiency of emitted light in the organic EL structure 2 by the microcavity effect, and can improve the emission angle distribution.

(Second Embodiment)
FIG. 6 shows another example of a configuration in which the organic optical device according to the present invention is applied to a top emission type organic EL.
The organic EL shown in FIG. 6 has a known top emission type organic EL structure 2 in which a metal electrode 23, an organic layer 22 including a light emitting layer, a transparent (or translucent) electrode 21 and the like are sequentially laminated on a substrate 3. The multilayer mirror 1 in which the high refractive index organic film 11 and the low refractive index organic film 12 are alternately and repeatedly laminated a plurality of times is disposed under the transparent electrode 21. That is, the multilayer mirror 1 which is the organic optical device according to the present invention is provided inside the organic EL structure 2. The multilayer mirror 1 provided inside the organic EL structure 2 needs to be conductive.
In addition to the same effects as in the first embodiment, the organic EL having such a configuration suppresses light absorption by the transparent electrode 21 by the multilayer mirror 1 provided inside the organic EL structure 2. You can also get the effect.

(Third embodiment)
FIG. 7 shows an example of a configuration in which the organic optical device according to the present invention is applied to a bottom emission type organic EL.
The organic EL shown in FIG. 8 has a known bottom emission type organic EL structure in which a transparent (or translucent) electrode 21, an organic layer 22 including a light emitting layer, a metal electrode 23, and the like are sequentially laminated on a transparent substrate 31. 2, the multilayer mirror 1 in which the high refractive index organic film 11 and the low refractive index organic film 12 are alternately and repeatedly stacked a plurality of times is disposed on the transparent electrode 21. That is, the multilayer mirror 1 which is the organic optical device according to the present invention is provided inside the organic EL structure 2. The multilayer mirror 1 provided inside the organic EL structure 2 needs to be conductive.
The organic EL having such a configuration can obtain the same effects as those of the second embodiment.

(Fourth embodiment)
FIG. 8 shows another example of a configuration in which the organic optical device according to the present invention is applied to a top emission type organic EL.
The organic EL shown in FIG. 8 is a known top emission type organic EL structure 2 in which a metal electrode 23, an organic layer 22 including a light emitting layer, a transparent (or translucent) electrode 21 and the like are sequentially laminated on a substrate 3. , The multilayer mirror 1 in which the high-refractive index organic film 11 and the low-refractive index organic film 12 are alternately and repeatedly stacked a plurality of times is disposed under the transparent electrode 21, and the same applies to the metal electrode 23. The multilayer mirror 1 is disposed. That is, two multilayer mirrors 1 that are organic optical devices according to the present invention are provided in the organic EL structure 2. The multilayer mirror 1 provided inside the organic EL structure 2 needs to be conductive.
The organic EL having such a configuration is based on electrodes by providing the multilayer mirror 1 above and below the organic layer 22 including the light emitting layer inside the organic EL structure 2 than in the second embodiment. Light absorption is suppressed. Such a configuration is expected to be applied to an organic semiconductor laser.

(Fifth embodiment)
FIG. 9 shows another example of a configuration in which the organic optical device according to the present invention is applied to a bottom emission type organic EL.
The organic EL shown in FIG. 9 has a known bottom emission type organic EL structure in which a transparent (or translucent) electrode 21, an organic layer 22 including a light emitting layer, a metal electrode 23, and the like are sequentially laminated on a transparent substrate 31. 2, the multilayer mirror 1 in which the high-refractive index organic film 11 and the low-refractive index organic film 12 are alternately and repeatedly stacked a plurality of times is disposed on the transparent electrode 21, and also under the metal electrode 23. The multilayer mirror 1 is arranged. That is, two multilayer mirrors 1 that are organic optical devices according to the present invention are provided in the organic EL structure 2. The multilayer mirror 1 provided inside the organic EL structure 2 needs to be conductive.
The organic EL having such a configuration is effective as in the fourth embodiment, and is expected to be applied to an organic semiconductor laser.

(Sixth embodiment)
FIG. 10 shows another example of a configuration in which the organic optical device according to the present invention is applied to a top emission type organic EL.
The organic EL shown in FIG. 10 has a known top emission type organic EL structure 2 in which a metal electrode 23, an organic layer 22 including a light emitting layer, a transparent (or translucent) electrode 21 and the like are sequentially laminated on a substrate 3. The organic layer 22 includes an electron transport layer 221 made of a low refractive index organic film, a light emitting layer 222 made of a high refractive index organic film, and a hole transport layer 223 made of a low refractive index organic film. That is, the organic layer 22 itself including the light emitting layer constitutes a multilayer film of a high refractive index organic film and a low refractive index organic film. For this reason, these high refractive index organic films and low refractive index organic films are required to have electrical conductivity.
According to the organic EL having such a configuration, the core / cladding structure can be formed in the organic layer 22 without separately providing a multilayer mirror, and the light-emitting layer 222 made of a high-refractive-index organic film serving as the core can be formed. Such a configuration is expected to be applied to an organic semiconductor laser because light can be effectively confined.

(Seventh embodiment)
In FIG. 11, an example of the structure which applied the organic optical device which concerns on this invention to an organic thin-film solar cell is shown.
The organic thin film solar cell shown in FIG. 11 has a known structure in which a transparent (or translucent) electrode 41, an organic layer 42 including an active layer, a transparent (or translucent) electrode 41, and the like are sequentially laminated on a transparent substrate 3. In the organic thin film solar cell structure 4, the multilayer mirror 1 in which the high refractive index organic film 11 and the low refractive index organic film 12 are alternately and repeatedly laminated a plurality of times is disposed on the upper transparent electrode 41. . That is, the multilayer mirror 1 which is an organic optical device according to the present invention is provided outside the organic thin film solar cell structure 4. For this reason, the multilayer mirror 1 is not required to have conductivity.
According to the organic thin-film solar cell having such a configuration, plasmon absorption by the electrode can be suppressed, and wavelength-selective light reflection can be performed, thereby improving the light absorption rate.

(Eighth embodiment)
FIG. 12 shows another example of a configuration in which the organic optical device according to the present invention is applied to an inverted cell type organic thin film solar cell.
The organic thin film solar cell shown in FIG. 12 is a known reverse cell type organic thin film in which a metal electrode 43, an organic layer 42 including an active layer, a transparent (or translucent) electrode 41, and the like are sequentially laminated on a substrate 3. In the solar cell structure 4, an antireflection layer 5 in which a high refractive index organic film 51 and a low refractive index organic film 52 are laminated is disposed on an upper transparent electrode 41. That is, the antireflection layer 5 which is the organic optical device according to the present invention is provided outside the organic thin film solar cell structure 4. For this reason, the antireflection layer 5 does not need to be conductive.
According to the organic thin-film solar cell having such a configuration, in addition to the same effects as those of the seventh embodiment, reflection on the upper surface of the organic thin-film solar cell is prevented, and photoelectric in the organic thin-film solar cell is prevented. There is also an effect that the field distribution can be optimized.

(Ninth Embodiment)
FIG. 13 shows another example of a configuration in which the organic optical device according to the present invention is applied to an inverted cell type organic thin film solar cell.
The organic thin film solar cell shown in FIG. 13 is a known reverse cell type organic thin film in which a metal electrode 43, an organic layer 42 including an active layer, a transparent (or translucent) electrode 41, and the like are sequentially laminated on a substrate 3. In the solar cell structure 4, an antireflection layer 5 in which a high refractive index organic film 51 and a low refractive index organic film 52 are laminated is disposed under an upper transparent electrode 41. That is, an antireflection layer 5 that is an organic optical device according to the present invention is provided inside the organic thin film solar cell structure 4. The antireflection layer 5 provided inside the organic thin film solar cell structure 4 needs to be conductive.
According to the organic thin-film solar cell having such a configuration, in addition to the same effect as that of the eighth embodiment, the anti-reflection layer 5 provided in the organic thin-film solar cell layer configuration 4 provides a photoelectric field. The effect that the controllability of distribution can be improved is also obtained.

  In addition, the formation method of each layer of the organic electronic device is an inkjet method, a casting method, a dip coating method, a bar coating method, a blade coating method, a roll coating method, a gravure coating method, even in a drive process such as a vapor deposition method and a sputtering method. Wet processes such as flexographic printing and spray coating may be used.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited by the following Example.

(Production of DBR)
On an ITO glass substrate having a thickness of 140 nm, a BDAVBi vapor deposition film (refractive index n _H = 1.99, film thickness d _H = 66.7 nm) as a high refractive index layer (H layer), and a low refractive index layer (L A layered structure of (HL) ⁸ H including a layer of 8 repetitions of PBD: C ₂₄ F ₅₀ (20:80) co-deposited film (refractive index n _L = 1.41, d _L = 94.1 nm). A prepared DBR was produced.
The reflectance of this DBR was measured.

FIG. 3 shows a comparison between the calculated value of the reflectance and the actual measurement value of each wavelength light of the DBR produced in the above.
As can be seen from the graph shown in FIG. 3, the reflectivity was 98%, the wavelength width was about 100 nm, and it was confirmed that a high reflectivity and high bandwidth DBR almost equal to the calculated value was obtained.

FIG. 4 shows the evaluation result of the reflection angle dependency of the reflectance for each wavelength light of the DBR.
As can be seen from the graph shown in FIG. 4, the above DBR was found to have a small reflection angle dependency.

From the above results, it was recognized that a multilayer mirror such as DBR can be formed using an organic semiconductor material.
Therefore, an organic laser such as an organic DBR laser can be constructed by using such a multilayer mirror made of an organic semiconductor material.

DESCRIPTION OF SYMBOLS 1 Multilayer film mirror 2 Organic EL structure 3 Substrate 4 Organic thin film solar cell structure 5 Antireflection layer 11,51 High refractive index organic film 12,52 Low refractive index organic film 21,41 Transparent electrode 22,42 Organic layer 23,43 Metal Electrode 31 Transparent substrate

Claims (5)

  An organic optical device comprising at least one set in which two layers of organic films having different refractive indexes are laminated, wherein a difference in refractive index between the two layers of organic films is 0.5 or more.   2. The organic optical device according to claim 1, wherein an optical film thickness of at least one of the two organic films is ¼ of a wavelength of incident light with respect to the organic thin film.   The organic optical device according to claim 1, wherein the organic optical device is a multilayer mirror.   The organic optical device according to claim 1, wherein the organic film is made of an organic semiconductor material.   An organic electronic device using the organic optical device according to any one of claims 1 to 4.

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