JP2002313554A - Light emitting element and method of manufacturing light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting element improved in element efficiency. SOLUTION: This light emitting element is provided with a base material 100; a transparent electrode 120 formed on the base material 100; a luminescent material layer 140 provided on the transparent electrode 120 and having at least one corrugated surface; and an electrode 160 formed on the luminescent material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention particularly relates to a light emitting device having a structure containing a substrate, a transparent electrode, a light emitting material layer and a second electrode.

[0002]

2. Description of the Related Art In a light emitting device having the above structure, holes are injected into a light emitting material from one electrode (usually a transparent electrode), and electrons are injected from the other electrode. Electron-hole recombination in a luminescent or active material produces light. The generated light is emitted from the device through the transparent electrode.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a light emitting device of the aforementioned type with improved device efficiency.

[0004]

According to a first aspect of the present invention, there is provided a substrate, a transparent electrode formed on the substrate, and a light emitting device provided on the transparent electrode and having at least one corrugated surface. A light emitting device comprising a material layer and a further electrode formed on the light emitting material is provided. A preferred configuration comprises a substrate having a corrugated surface, a transparent electrode formed on the corrugated surface, a luminescent material layer provided on the transparent electrode, and a further electrode formed on the luminescent material. .

In another preferred configuration, a base material, a transparent electrode formed on the base material, a conductive polymer layer formed on the transparent electrode and having a corrugated surface opposite to a surface facing the transparent electrode, A light emitting device is provided comprising a luminescent material in contact with a corrugated surface, and a further electrode formed on the luminescent material.

According to a second aspect of the present invention, a step of providing a substrate, a step of forming a transparent electrode on the substrate, a step of providing a luminescent material layer on the transparent electrode, A method for manufacturing a light-emitting device, comprising: adjusting the light-emitting element to have at least one corrugated surface; and forming another electrode above the light-emitting material layer.

In a preferred method, conditioning the light emitting surface to have at least one corrugated surface includes providing a corrugated surface on the substrate.

[0008] Another preferred method includes forming a conductive polymer layer on the transparent electrode, wherein the step of adjusting the light emitting surface to have at least one corrugated surface comprises: Providing a corrugated surface on the layer.

In the present invention, very preferably, the luminescent material is an organic material.

[0010] In conventional devices, it has been found that the luminescent material layer functions as a waveguide and that a substantial portion of the generated light can be trapped in a waveguide mode in the active material. The higher the refractive index of the luminescent material,
The proportion of generated light trapped in the waveguide mode in the light emitting material increases. Therefore, this idea is important when using organic materials as the light emitting layer, especially when using conjugated polymers as active materials. This is because organic materials, particularly conjugated polymers, have a high refractive index near the wavelength of light emitted from the organic material.

Some types of electronic pumping laser devices (elec
It is understood that proposals have been made to use a corrugated surface in a tronically pumped laser device. However, such a device basically has a different structure and operation mode as compared with the light emitting device to which the present invention is applied.
Furthermore, previous proposals were of predominantly theoretical nature and assumed very difficult, if not impossible, devices to actually assemble.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: FIG.

The present invention provides a light emitting device in which the active layer has a corrugated surface. The effect of this wavy active layer is to improve the efficiency of the light emitting device according to the present invention. The pitch of the corrugated shape, the smaller its width, as described below,
Affects the function of the device. However, there are four areas of particular interest for embodiments of the present invention. These are: manufacturing method, light loss in the active layer, corrugated pitch and corrugated periodic structure. Each of these four areas of particular interest is discussed below, followed by specific examples.

Manufacturing Method A particular advantage of the present invention is that many different manufacturing methods are suitable for use in manufacturing a light emitting device according to the present invention.

FIG. 1 illustrates a method of forming a substrate for use in a light emitting device according to the present invention. In this configuration,
The substrate 10 contains two components, a transparent base 12 and a photopolymer resin 14. As shown in FIG. 1 a, a photopolymerizable resin 14 is applied to the upper surface of the base material 12. FIG.
As shown in FIG. 2B, the photopolymerizable resin 14 covers an area at least as large as the area of the corrugated portion of the stamping mold 16. The stamping die is pressed against the photopolymerizable resin 14, which has the effect of flattening the photopolymerizable resin 14 into a layer of uniform thickness (excess resin flows out of the edge). This operation is preferably performed in a vacuum so as to prevent the formation of bubbles in the resin layer. As shown in FIG. 1c,
The resin 14 is cured by irradiating UV radiation through the transparent substrate 12. After the resin has cured, the stamping mold is removed, leaving the treated substrate 10 having a corrugated upper surface 18. Using this corrugated surface, a corrugated active layer is formed. This method is particularly suitable for large products.

A conductive polymer layer is formed by spin coating from a solution. The surface of the conductive polymer layer also has a wavy shape. This is not exactly the same as the corrugations on the photopolymerized layer, but rather slightly shallow and rounded. Further, instead of the conductive polymer layer, a hole transport layer can be applied. Spin coating is suitable for a polymer-type hole transport layer, while vapor deposition is suitable for a low-molecular-weight hole transport layer. For the light emitting layer, spin coating or evaporation is used depending on the type (whether polymer type or low molecular type). Subsequently, a cathode is formed by vapor deposition of a metal.

Instead of using a substrate formed by the method of FIG. 1, a transparent electrode is formed thereon, using a transparent substrate configuration with a conductive polymer film formed on the electrode, Here, the conductive polymer has a corrugated surface. A method for forming such another component is shown in FIG.

In FIG. 2, component 20 is formed by providing a transparent substrate having an indium tin oxide (ITO) electrode 24 thereon. As shown in FIG. 2 a, a solution 26 of a conjugated polymer embedded in a transparent polymer matrix is applied to the upper surface of the ITO electrode 24. FIG.
The solution 26 covers an area at least as large as the area of the corrugated part of the stamping mold 28 as shown in FIG.
Pressing the stamping die firmly on the solution 26 has the effect of flattening the solution into a layer of uniform thickness. The resulting material is then dried by heating to solidify the solid content of solution 26. After solidification of the solid content, the stamping mold is removed to complete the substrate 20 having a corrugated upper surface 30.

In the method of FIG. 1, a stamping type of metal (for example, nickel) can be used. However, the use of a metal stamping type is difficult in the method of FIG. It may be considered unsuitable. Therefore, in the method of FIG. 2, a stamping mold made of a polymer through which a solvent can penetrate may be used. Further, FIG.
May involve the use of vacuum drying.

Another method of forming part 20 is shown in FIG. The method of FIG. 3 involves forming two components and laminating them into one part. First, the conductive polymer material 32 is applied on the stamping mold 34 by spin coating. As shown in FIG. 3 a, the spin-coated material 32 may have a corrugated upper surface that follows the corrugation of the stamping mold 34. Transparent substrate 38,
A component composed of the ITO electrode 40 and the conductive polymer 42 is separately formed as shown in FIG. 3B. The spin-coated stamping mold 34 is inverted and placed on the other component so that the polymers 32 and 42 abut each other. As shown in FIG. 3c, the two components are laminated together under pressure (or heat). Polymer 32
And 42 combine to form a single layer 44. The polymer has plastic properties especially at temperatures above the glass transition temperature. The polymers 32 and 42 do not differ in their surface morphology, and due to their plastic nature, the polymers combine to form a single layer 44. Thereafter, the stamping mold 34 is removed, as shown in FIG. 3d, to form a transparent base 38, an ITO electrode 40 formed thereon, and a conductive polymer layer formed on the ITO and having a corrugated upper surface 46. Leave a single component with 44.

A still further method of forming the desired components is shown in FIG. This method is based on the polymer solution method shown in FIG.
Is used. Specifically, as shown in FIG. 4A, the conductive polymer material 48 is applied to the stamping mold 50 by spin coating. Separately,
A transparent substrate 52 having an ITO electrode 54 thereon is placed on the transparent substrate 52 as shown in FIG.
It is prepared by applying a conductive polymer solution 56 to the ITO surface as shown in FIG. Next, as shown in FIG. 4 c, the spin-coated mold 50 is inverted and pressed against the polymer solution 56. Next, heat is applied to evaporate the solvent and form a single layer 58 from the polymers 48 and 56. This method can form a single layer with a corrugated surface, even if the polymer used is not sufficiently plastic for the lamination process. As before, the mold removal is done on a transparent base,
It leaves an ITO electrode formed thereon and a single component having a conductive polymer formed on the ITO and exhibiting a corrugated upper surface.

FIG. 5 shows a light emitting device using the substrate manufactured by the method shown in FIG. In FIG. 5, the transparent base material is denoted by reference numeral 100, the transparent ITO electrode is denoted by reference numeral 120, the light emitting polymer is denoted by reference numeral 140, and the metal electrode is denoted by reference numeral 160.
Indicated by FIG. 6 shows a light emitting device using the substrate manufactured by the method shown in FIG. Not only the light emitting device manufactured by the method shown in FIG. 3 but also the one manufactured by the method of FIG. 4 are the same as those shown in FIG. The common reference numbers used in FIGS. 6 and 5 indicate the same basic components,
In FIG. 6, neither the substrate nor ITO is corrugated. In FIG. 6, the corrugated surface is provided to the active layer 140 by reference numeral 1.
30 is a conductive polymer layer indicated by 30.

In use, a display element is driven by applying a voltage. Typically, the voltage ranges from 2V to 10V. A positive voltage can be applied to the anode and the cathode can be grounded.

The functional effect of the corrugated surface will be described with respect to the embodiment formed by the method of FIG. 1 and the embodiment formed by any of the methods according to FIGS.
In particular, the fundamental function of the wave-shaped surface is the guided wave propagation mode (wavegu
ide propagation mode)
e) emitting much of the generated light conventionally trapped in the waveguide mode from the device in the emission mode (ie, through a transparent substrate perpendicular to the active layer). Within limits, the depth or width of the corrugations controls the strength of the junction between the modes (the deeper the depth, the higher the junction). Typically, the corrugation depth is 5
It may be about 0 nm, that is, the same as the depth of the active layer. But,
The period of the wave shape is more important.

The (periodic) waveguide mode is composed of an active material and a transparent I
It is recognized that the waveguide mode may be provided over both of the TO electrodes and the waveguide mode may be provided exclusively within the ITO layer. However, if the index of refraction of ITO is sufficiently smaller than the index of refraction of the active layer, the waveguide modes that are actually exclusively in the ITO layer can be ignored.

An actual device structure having many layers can support many waveguide modes. However, only two waveguide modes need to be considered for the following reasons. One is a waveguide mode supported in the light emitting layer, and the other is a mode supported entirely from the substrate to the light emitting layer. Typical refractive indices of the layers and substrates are: 1.8-1.9 for the light-emitting layer; 1.5-1.6 for the conductive polymer layer (or hole transport layer); ITO layer Is 1.8
-2.0; 1.55 for the substrate (or photopolymerized layer). Emissive layers generally have a high refractive index due to the absorption edge near the emission spectrum. The conductive polymer layer or the hole transport layer has a lower refractive index than the light emitting layer. The conductive polymer is a narrow bandgap polymer and has a rather low refractive index in the visible region. The hole transport layer should be transparent to the emission spectrum, resulting in a lower refractive index.
The refractive index of the conductive polymer layer (or the hole transport layer) is substantially equal to the refractive index of the substrate. The conductive polymer layer (or the hole transport layer) functions as a coating layer that confine the light emitted from the light emitting layer in the light emitting layer. Since the refractive index of air is the lowest in the system, not all light that has passed through the conductive polymer layer (or hole transport layer) enters the radiation mode. Some light is reflected at the interface between the substrate and air and is confined within the structure from the light emitting layer to the conductive layer to the substrate.

FIG. 7 shows various parameters of the corrugated active layer to be controlled so as to achieve the improved efficiency of the light emitting device according to the present invention. In this regard, the following equations can be derived for various parameters.

The height (or depth) of the active layer is represented by h.
As shown in FIG. 7, light propagating in a waveguide mode in the active layer is reflected from the upper and lower surfaces of the active layer at an angle θ _m (where m is used to indicate the number of modes). There is a phase change where there is reflection from this surface, which depends on the respective refractive index between the active material and the material on each side thereof. Respectively a phase change of the upper and lower surfaces by the symbol phi _a and phi _b. Desired (in vacuum)
Λ _o to indicate the output wavelength, k to indicate the propagation constant in vacuum, β to indicate the propagation constant in the active material, Λ to indicate the pitch of the wave type, and n to indicate the integer. with these parameters are related by the following _{equation: 2nhkcosθ m -2φ a -2φ b =} 2mπ β = nksinθ m k = 2π / λ o Given the adjacent portions along the corrugated surface of the active layer It is clear that a phase difference exists in the emission of radiation from each adjacent part. The radiation mode output is therefore enhanced by ensuring that the output from the sections separated by the length of the corrugated pitch is in one phase. Therefore, the phase difference along the active layer, Δφ, should be configured to be equal to the product of the corrugated pitch, Λ, and the propagation constant, β in the active layer. For example, in FIG.
The emission of the radiation at the two points should be in phase with each other, ie, to ensure that Δφ = βΛ. Thus, for a strong radiation mode emission: Δφ = βΛ = 2πv (v = 1, 2, 3,...) And therefore: Λ = vλ _o / nsin θ _m .

That is, the pitch required to achieve intense emission in the emission mode at wavelength λ _o is a relatively simple function of the angle θ _m , which is the depth and refractive index of the active layer and the junction. Is determined by the number of waveguide propagation modes.

(Periodic structure) The corrugated surface corresponds to 3 in FIG.
It will be appreciated from FIGS. 1-4 that, as shown first in one embodiment, it has the shape of a simple diffraction grating.
This may be one case, but is not limited to this, and another periodic pattern may be used. Another shape that can be considered as a one-dimensional periodic structure is shown in FIG. 8A as two other examples. Furthermore, for example, what is considered as a two- or three-dimensional periodic structure having the format shown in FIG. 8B can be used. These are essentially photon bandgap structures. These stop propagation in certain directions at certain wavelengths. Of the two embodiments shown in FIG. 8B, the offset pattern (the second embodiment) is considered to be the most effective because it indicates that all the inter-dot distances are equal to Λ. Yet another example is to use the so-called chirped grating of the example shown in FIG. Usually, the use of a grating results in a narrow spectrum. However, where high efficiency is required without the limitations of narrow gratings, chirped gratings can be used. This results in a broad spectrum. Efficiency is improved and the emission from the device depends more on the intrinsic emission properties of the material.

(Light Loss) In order to obtain strong light emission from the waveguide mode joined to the radiation mode, it is necessary to minimize the light loss in the waveguide mode. Light in the waveguide travels a very long distance compared to light emitted directly in radiation mode. Even a small amount of absorption will weaken the field intensity confined in the active layer and reduce the emission from the waveguide mode joined to the radiation mode.

Coming from a flat waveguide without a corrugated surface
Consider light and light through a corrugated waveguide; some of the light
Is refracted out of the plane and the rest is reflected into the waveguide.
You. The electric field strength is exponential. The intensity in the plane area is
It is the sum of incident light and reflected light. The decay curve in the wavy region is
I = e^-ΓxWhere γ is derived
It represents the junction coefficient between the waveguide mode and the radiation mode. In the waveguide
Absorption, ie, I = e ^-ΑxCan be described in this
Where α is the absorption coefficient. Strong light emission from waveguide mode
Preferably has a factor of at least 10
And the joining coefficient γ should be smaller than the absorption coefficient.
You.

The basic absorption of the active material, for example, the light-emitting small molecule and the light-emitting conjugated polymer, is sufficiently small in the transmission spectrum region (for example, 1000 cm ^-1 or less) as compared with the junction coefficient. Absorption in the waveguide mode arises not only from absorption in the active layer, but also from absorption in adjacent layers. Absorption from the adjacent layer occurs because the medium of the adjacent layer can absorb the transient light energy present in the adjacent layer. Since the cathode is made of metal, which has a large absorption, if the cathode is formed on an active layer, the absorption in the waveguide is defined by the metal. Since the degree of absorption is 1000 cm ^{- 1} , a structure having a cathode on the active layer can be used in the present invention, but is probably not ideal. An electron transport coating layer is preferably located between the active layer and the cathode. The electron transport coating should be made from a material that has a high electron mobility and a good match of its LUMO level to the work function of the cathode. For high mobilities, small molecule systems may be more suitable for this purpose than conjugated polymers.

A preferred structure for achieving low absorption in the waveguide is shown in FIG. The structure includes a substrate 200 having a photopolymerized layer 210 thereon. The surface of the photopolymerization layer 210 opposite to the surface in contact with the base material 200 is corrugated, and the transparent electrode 220 is provided thereon. Next, a conductive polymer layer or a hole transport layer 230 is provided on the electrode 220,
Next, the light emitting layer 240 is disposed. An electron transport layer 250 is provided on the light emitting layer, and the top of the structure is an electrode 260.
All subsequent layers, including electrodes 260, follow the waveform of layer 210. In this structure, the thickness of the electron transport layer should be greater than the transient light penetration depth at the interface between the light emitting layer and the electron transport layer.

Scattering in the active layer also increases light loss. Scattered light, however, is emitted from the device, so scattering does not reduce efficiency. However, if the scattering is large, it is difficult to obtain the narrow spectral output expected of the device (due to the period of the wave pattern). Small molecule systems generally have a rough surface and many scattering points. Amorphous conjugated polymers are more suitable for the active layer because of their low scattering properties.

Light loss in the waveguide mode arises not only from absorption by the active layer, but also from absorption by adjacent layers. Absorption by an adjacent layer occurs because the reflection at the interface of the active layer is not reflection from the ideal surface, but is actually reflection across the interface depth. In addition, domain ordering occurs in the active layer, which is similar to a polycrystalline structure. That is, scattering occurs, which also causes light loss in the waveguide mode.

The absorption coefficient α of the active material is important for reducing light loss in the waveguide mode. Typically, low molecular weight has an absorption coefficient in the range of ^{500cm -1 ~1000cm} -1.

The assembling method using a low-molecular-weight system causes defects in the layer and causes high scattering. In comparison, polymer materials can be applied using ink-jet technology, and thus can apply a low defect, low scattering active layer.

The intensity of light loss in a material depends on the absorption coefficient α and the distance x in the material as follows. I = e− ^αx Therefore, if the absorption coefficient is large, the depth of the material (eg, 1
(Within 0 μm), a sharp change in absorption occurs. A layer thickness of 10 μm does not result in a large junction, so 10 μm can be considered the lower limit. The absorption coefficient at 100 cm ^-1 is 1
This would correspond to an absorption depth of 00 μm, which is good enough to form the desired junction. Therefore, the use of materials such as conjugated polymers is more desirable than the use of low molecular weight systems as the active layer. Also, of course, there are many different polymer materials, some exhibiting a polycrystalline type phase,
Some exhibit an amorphous phase. It is preferred to use an amorphous conjugated polymer for the active layer of the device according to the invention. Polyfluorene derivatives are particularly suitable materials having strong luminescence in the device according to the invention.

The embodiment of the present invention is preferably
A light-emitting material having an absorption coefficient of at most cm ⁻¹ , more preferably at most 500 cm ⁻¹ is used.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment)
Prepared according to the method described in Such examples used a glass substrate and an epoxy photopolymerized resin. A corrugated surface was formed using an electrodeposited nickel stamper patterned by photolithography. 300, 330, 36
Using a stamper having a one-dimensional periodic structure having a pitch size of 0 and 450 nm, a corrugated depth of 50 nm
Set to The glass substrate was treated with a silyl coupler to ensure sufficient adhesion to the resin layer. The ITO layer
It was applied on the resin layer by sputtering at 200 ° C. using Ar and O ₂ sputtering gas. IT
The thickness of the O layer was 120 nm. An active layer formed of F8BT, poly (9,9-dioctylfluorene-co-2,1,3-benzothiadiazole) was applied on the ITO layer by spin coating. F8BT is an amorphous material with low light loss. The active layer had a thickness of 140 nm and an absorption coefficient of less than 100 cm ^-1 . Ca1
A metal electrode formed of 00 nm / Al 300 nm was provided on the active layer by vapor deposition coating.

The light emitting device of the first embodiment has high directivity and high efficiency and a narrow line width output. Typically, the line width is 20
nm and best results are 330 nm and 360 n
m and a corrugated pitch of m. These pitches satisfy the requirement to obtain strong emission at the desired wavelength, which is within the fluorescence spectrum of F8BT.

FIG. 9 shows the spectral output achieved in this embodiment.

(Second Embodiment) A second embodiment was formed essentially according to the method of FIG. Such an embodiment has a flat I
A glass substrate provided with a TO layer was used. The conductive polymer layer was formed using an aqueous solution of a mixture of PEDOT (poly-3,4-ethylenedioxythiophene) and PSS (poly-styrene-sulfonic acid) in a ratio of 1: 5 to 1: 100. PSS was used essentially as a flexible matrix for PEDOT material. PPS is a conventional polymer, which is relatively easy to perform stamping and casting processes. PEDOT is a conjugated polymer, which is not as easily processed as a non-conjugated polymer. It has higher conductivity, but has less plastic bulk properties. The use of thin PEDOT is acceptable as the use of thin layers reduces the importance of conductivity. PEDOT has low absorption (the absorption coefficient is about 0.04 in the visible region), where it can be reduced by dilution with PSS, which is transparent in the visible region. This PEDOT does not form the core of the waveguide,
Light distribution ends confined in the core may be present in this PEDOT layer. Waveguide loss can be reduced by applying this diluted PEDOT with low absorption.

The surface of the conductive polymer layer was corrugated using a polymer stamper mold (formed using a nickel stamper). That is, a polymer solution was applied on the ITO layer, and a polymer stamper mold was applied to the solution.
It was left to dry at 24 ° C. for 24 hours. The mold was then removed and the active layer was applied by spin coating. Active layer is F8B
T, poly (9,9-dioctylfluorene-co-2,
1,3-benzothiadiazole) to a thickness of 140 nm. The absorption coefficient was 100 cm ^-1 or less. C
A metal electrode formed of a100 nm / Al300 nm was provided on the active layer by vapor deposition coating.

The light emitting device of the second embodiment exhibited output characteristics very similar to those of the light emitting device of the first embodiment.

A first improved embodiment of the second embodiment was formed essentially using the method of FIG. That is, the conductive polymer solution was spin-coated on the nickel stamper and the ITO layer. The two components thus formed were pressed together at 200 ° C. for 5 minutes in a vacuum and then the nickel stamper was separated. The same result as in the previous example was obtained.

A second improved embodiment of the second embodiment was formed using essentially the method of FIG. That is, the conductive polymer solution was spin-coated on the plastic mold and the ITO layer. The two components were combined together and dried in vacuum at 80 ° C. for 24 hours. The plastic mold was then removed. Again, the same results as in the previous example were obtained.

Third Embodiment The third embodiment was formed essentially according to the method and materials used in the first embodiment, except that the stamper was embossed in an array of dots. That is, the periodic structure was of the type shown in FIG. The third set of examples showed high directivity output, and the emission peak was 2.5 times that of the first example.
The one-dimensional periodic structure of the first embodiment produces a "line" output directivity, whereas the two-dimensional periodic structure of the third embodiment produces a "pillar" output directivity.

Fourth Embodiment The fourth embodiment was formed essentially according to the method and materials used in the first set of embodiments, but in which the stamper was embossed on a "chirped" grid. did. That is, the periodic structure was of the type shown in FIG. The fourth example showed high efficiency and broad spectral output.

Fifth Embodiment The fifth embodiment essentially follows the method and materials used in the first set of embodiments, except that the stampers use different periods or different designs of the same grating. Provided on the substrate. Thus, each region having a respective one of the gratings enhances each wavelength,
Thus, the embodiments provided multiple color outputs. The high directivity of the output reduces the usefulness of elements for display elements such as those conventionally used in liquid crystal display panels. However, the high directivity of the output provides elements that are particularly suitable for a variety of other applications, such as projection displays.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a method of forming a substrate for use in a light emitting device according to an embodiment of the present invention along the steps.

FIG. 2 is a cross-sectional view showing another method of forming a substrate for use in a light emitting device according to an embodiment of the present invention along the steps.

FIG. 3 is a cross-sectional view showing a further method of forming a substrate for use in a light emitting device according to an embodiment of the present invention along the steps.

FIG. 4 is a cross-sectional view showing another method of forming a base material for use in the light emitting device according to the embodiment of the present invention along the steps.

FIG. 5 is a cross-sectional view showing a light-emitting element using a substrate manufactured by the method shown in FIG.

FIG. 6 is a cross-sectional view showing a light emitting element using a substrate manufactured by the method shown in FIG. 2, 3 or 4.

FIG. 7 is a diagram showing various parameters related to pitch selection for an active layer.

FIG. 8 is a diagram showing various periodic structures that can be employed in practicing the present invention.

FIG. 9 shows a spectral output of an example of an embodiment according to the present invention.

FIG. 10 is a cross-sectional view showing a preferred structure for achieving low absorption in a waveguide.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Base material 12 Transparent base material 14 Resin 16 Stamping type 18 Wavy upper surface 100 Transparent base material 120 Transparent electrode 140 Light emitting material layer (light emitting polymer) 160 Metal electrode

 ──────────────────────────────────────────────────続 き Continued on the front page (71) Applicant 501023524 Cambridge University Technical Services Limited (Old Schools Trinity Lane Cambridge CB2 1TS England UK Inventor Takeo Kawase Cambridge UK CB2 1TS Trinity Lane The Old Schools F-term in Cambridge University Technical Services Limited (Reference) 3K007 AB03 AB04 AB18 BA00 CB01 CB04 DA01 DB03 EB00 FA01

Claims (20)

[Claims] 1. A substrate, a transparent electrode formed on the substrate,
A light emitting device comprising: a light emitting material layer provided on the transparent electrode and having at least one corrugated surface; and a further electrode formed on the light emitting material layer. 2. The light emitting material is an organic material.
The light-emitting element according to any one of the preceding claims. 3. The light emitting device according to claim 1, wherein the substrate has a corrugated surface. 4. A conductive polymer layer is formed on the transparent electrode, the conductive polymer layer has a corrugated surface on the side opposite to the surface facing the transparent electrode, and the luminescent material is formed of the conductive polymer layer. The light emitting device according to claim 1, wherein the light emitting device is in contact with a corrugated surface of the light emitting device. 5. The light emitting device according to claim 1, wherein the light emitting material has an absorption coefficient of 1000 cm ⁻¹ or less. 6. The light emitting device according to claim 1, wherein the light emitting material is made of a conjugated polymer. 7. The light emitting device according to claim 1, wherein the light emitting material is made of a polyfluorene derivative. Wherein said corrugated surface has the formula: Λ = vλ _o / nsi
having a pitch に よ る by nθ _m (the angle θ _m is above and below the layer of luminescent material for light propagating in a waveguide mode m in the luminescent material from the upper and lower surfaces of the layer of luminescent material) The angle of reflection from the lower surface, λ _o
Is the output wavelength, and n and v are integers.)
8. The light-emitting element according to any one of claims 7 to 7. 9. The pitch of the corrugated surface is 300 to 450.
The light emitting device according to claim 1, wherein the wavelength is in the range of nm. 10. The light emitting device according to claim 1, wherein the corrugated surface has a one-dimensional periodic structure. 11. The light emitting device according to claim 1, wherein the corrugated surface has a two-dimensional periodic structure. 12. The light emitting device according to claim 1, wherein said corrugated surface has a three-dimensional periodic structure. 13. The method according to claim 13, wherein the corrugated surface has a chirped grating structure (structural structure).
10 to 9 having a texture of chirping grating.
The light emitting device according to any one of the above. 14. The light emitting device according to claim 1, wherein said light emitting material layer has a plurality of regions, and each region has a corrugated surface having a different pitch. 15. A step of providing a substrate, a step of forming a transparent electrode on the substrate, a step of providing a light emitting material layer on the transparent electrode, and a light emitting surface having at least one corrugated surface. The method for manufacturing a light-emitting element, comprising the steps of: adjusting the temperature of the light-emitting material layer; and forming another electrode above the light-emitting material layer. 16. The method according to claim 15, wherein adjusting the light emitting surface to have at least one corrugated surface includes providing a corrugated surface on the base material. 17. A step of providing a photocurable resin on the substrate, a step of forming a corrugated surface on the substrate by molding the resin using a mold, and exposing the resin to radiation to convert the resin. 17. The method according to claim 16, further comprising a step of curing. 18. The method according to claim 18, further comprising the step of forming a conductive polymer layer on the transparent electrode, wherein the step of adjusting the light emitting surface to have at least one corrugated surface comprises forming a corrugated surface on the conductive polymer layer. The method for manufacturing a light-emitting device according to claim 15, comprising a step of providing a surface. 19. The method according to claim 18, further comprising the steps of forming a corrugated surface on the conductive polymer layer by molding the layer using a polymer mold, and curing the layer by applying heat. A method for manufacturing a light emitting device. 20. The step of providing a corrugated surface on the conductive polymer layer comprises: spin-coating the conductive polymer material on a transparent electrode; and spin-coating the conductive polymer material on the corrugated surface of the mold. Disposing the spin-coated mold on a conductive polymer layer provided on a transparent electrode so as to sandwich the two conductive polymer layers together, and then removing the mold. A method for manufacturing a light emitting device according to claim 18.