JP2011096367A - Glass substrate, solar cell, organic el element, and manufacturing method of glass substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glass substrate capable of improving utilization efficiency of light in an optical element such as a solar cell or a light-emitting element, and a manufacturing method of the glass substrate. <P>SOLUTION: The glass substrate includes a structure with periodical repeating projections and grooves in a length direction on at least one surface, and with a haze rate of wavelengths from 300 nm to 800 nm to be 30% or more. At least on a surface of a glass base material, a structure periodically repeating projections and grooves is formed, then the glass base material is heated to extend into a length direction of the projections and grooves. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a glass substrate, a solar cell, an organic EL element, and a method for producing a glass substrate.

  In solar cell substrates, light emitters, and display substrates, a rough surface treatment is performed to form a periodic uneven structure (texture structure) having a size equivalent to the wavelength of light on the surface of a glass substrate. Yes. In the solar cell substrate, incident light is scattered by the concavo-convex structure, and the light use efficiency is increased. Moreover, in a light-emitting body and a display, the light emitted from light emitting elements, such as an organic EL element, is scattered by a concavo-convex structure, and the efficiency of discharge | released outside increases.

  As a method for roughening the substrate, there are a sand blast method, a rough polishing method, a dicing method, a chemical etching method, and the like (for example, see Patent Documents 1 and 2).

JP-T-2004-506330 Japanese Patent No. 4049329

  By the way, by making the pitch of the concavo-convex structure about the wavelength of light, the light utilization efficiency becomes higher. However, in the above rough surface processing method, the surface roughness increases when the local surface is viewed. As a result, the solar cell substrate has a problem that the conversion efficiency decreases due to insufficient coverage of the semiconductor thin film. Further, when laser light is used in electrode patterning, the laser light may be scattered and the electrode may be disconnected or short-circuited.

  The subject of this invention provides the manufacturing method of the glass substrate which can improve the utilization efficiency of light in optical elements, such as a solar cell and a light emitting element, a solar cell using this, an organic EL element, and a glass substrate. That is.

  In order to solve the above problems, the invention according to claim 1 is a glass substrate having a periodic repeating structure of protrusions and grooves in the longitudinal direction of at least one surface, and has a haze ratio of a wavelength of 300 nm to 800 nm. Is 30% or more.

  The invention described in claim 2 is a glass substrate having a periodic repeating structure of ridges and grooves in the longitudinal direction of at least one surface, wherein the pitch between the ridges and grooves is 200 nm to 10 μm, The step between the top of the protrusion and the bottom of the groove is 2 μm or less.

Invention of Claim 3 is the glass substrate of Claim 1 or 2, Comprising: In observation area | region 1 micrometer ² or less, arithmetic mean roughness (the top part of the said protrusion and the bottom part of the said groove | channel) ( Ra) is characterized by being 2 nm or less.

  Invention of Claim 4 is a glass substrate as described in any one of Claims 1-3, Comprising: The said glass substrate is 0.3 mm or less, It is characterized by the above-mentioned.

  The invention according to claim 5 is a solar cell using the glass substrate according to any one of claims 1 to 4.

  The invention according to claim 6 is an organic EL element characterized by using the glass substrate according to any one of claims 1 to 4 as a substrate or a sealing material.

  Invention of Claim 7 is a manufacturing method which manufactures the glass substrate as described in any one of Claims 1-4, Comprising: At least one surface of a glass base material is periodic with a protrusion and a groove | channel. A repeating structure is formed, and then the glass base material is heated and stretched in the length direction of the protrusions and the grooves.

  According to the present invention, incident light can be scattered by the uneven shape of the glass substrate, and the light utilization efficiency is increased. In addition, since light emitted from the light emitting element is scattered by the uneven structure, efficiency of being emitted to the outside is increased.

It is a scanning electron microscope (SEM) photograph of a glass base material. It is an enlarged photograph of FIG. It is a scanning electron microscope (SEM) photograph of the glass substrate after extending | stretching. FIG. 4 is a partially enlarged view of FIG. 3. It is an observation image by the atomic force microscope (AFM) which shows the range of 30 micrometers x 30 micrometers of the glass substrate after extending | stretching. It is an observation image by an atomic force microscope (AFM) which shows the range of 500 nm x 500 nm of the glass substrate after extending | stretching. It is an observation image by an atomic force microscope (AFM) which shows the range of 100 nm x 100 nm of the glass substrate after extending | stretching. It is the three-dimensional image which comprised the range of 30 micrometers x 30 micrometers of the glass substrate after extending | stretching with the atomic force microscope (AFM). It is a figure which shows the solar cell 10 using the glass substrate 11 which concerns on this invention. It is a graph which shows a total light transmittance. It is a graph which shows a scattered light transmittance. It is a graph which shows a haze rate. It is sectional drawing which shows the organic EL element 20A of the bottom emission structure using the glass substrate 21 which concerns on this invention. It is an enlarged view of the XIV part of FIG. It is sectional drawing which shows the organic EL element 20B of the top emission structure using the glass substrate 21 which concerns on this invention. It is an enlarged view of the XVI part of FIG.

Embodiments of the present invention are described in detail below.
Quartz glass, borosilicate glass, etc. can be used for the glass base material before extending | stretching which concerns on this invention.
In order to form a periodic repetitive structure (irregular shape) of protrusions and grooves on the glass base material, for example, masking is performed on the protrusions on the glass surface, and then sandblasting is performed on the glass surface. Thus, there is a method of forming a groove in a portion that has not been masked. Alternatively, a method by mechanical processing such as rough polishing or dicing, a method by chemical processing such as wet etching or dry etching, or the like may be used.

  The glass substrate which concerns on this invention is manufactured by extending | stretching in the length direction of the formed protrusion and groove | channel with respect to the glass base material in which said uneven | corrugated shape was formed. The stretching temperature is appropriately changed depending on the material of the glass base material, and is set within a temperature range of 500 ° C. higher than the softening point to the softening point. It is preferable to set the temperature within the range of 200 ° C. higher than the softening point to the softening point, and more preferable to set the temperature within the range of 100 ° C. higher than the softening point.

For example, when the glass base material is quartz glass, since the softening point is about 1580 ° C., the stretching is preferably performed at about 1680 ° C. Alternatively, when the glass base material is borosilicate glass, since the softening point is about 815 ° C., it is preferable to perform stretching at about 915 ° C.
By performing stretching at a temperature closer to the softening point, the uneven shape of the glass base material can be left in a similar shape on the glass substrate to be manufactured.

In the glass substrate manufactured in this way, since an uneven shape is formed on the glass base material and then stretched, a glass substrate having a reduced shape of the glass base material is formed. For this reason, the surface roughness of a glass substrate becomes smaller than a glass base material. Moreover, since it can manufacture continuously using the redraw method, a glass substrate can be manufactured cheaply.
The glass substrate preferably has a thickness of 0.3 mm or less. If the thickness is 0.3 mm or less, it is flexible and can be greatly deformed (flexibility).

  In the concavo-convex shape of the manufactured glass substrate, the pitch between the ridge and the groove is preferably 200 nm to 10 μm, and the step between the top of the ridge and the bottom of the groove is preferably 2 μm or less. When the pitch is 200 nm to 10 μm and the step is 2 μm or less, in the solar cell substrate, incident light can be scattered by the uneven shape of the glass substrate, and the light utilization efficiency is increased. Moreover, in a light-emitting body and a display, the light emitted from light emitting elements, such as an organic EL element, is scattered by a concavo-convex structure, and the efficiency of discharge | released outside increases.

The manufactured glass substrate preferably has an Ra (arithmetic mean roughness: JIS B0601-1994) of 2 nm or less in an observation region of 1 μm ² or less. When Ra is 2 nm or less, when used as a solar cell substrate, the coverage of the semiconductor thin film is improved, and the conversion efficiency is improved. Moreover, also when using a laser beam in electrode patterning, scattering of a laser beam can be suppressed. Further, when used as a substrate for an organic EL element, it is possible to prevent current leakage, short circuit, and dark spots.
Hereinafter, the present invention will be further described by examples.

A glass base material (75 mm in width, 525 mm in length, 1.5 mm in thickness) made of Tempax Float (registered trademark of Shot AG), with an uneven surface with a width of 30 μm and a depth of 2.5 μm on one surface by sandblasting A shape was formed. Thereafter, stretching was performed at a furnace temperature of 915 ° C. and a linear velocity of 1 m / min. The drawing rate during stretching was 1/5, the width of the glass substrate after stretching was 15 mm, and the thickness was 0.3 mm. In addition, by changing the withdrawal rate, the substrate thickness and the pitch of the concavo-convex shape formed on the substrate surface can be arbitrarily changed. However, if the substrate thickness is 0.3 mm or less, a flexible glass substrate can be obtained. it can. The concave / convex pitch is preferably 400 nm to 800 nm, which corresponds to the wavelength of visible light, but the light use efficiency can be increased even at 200 nm to 10 μm.
Next, the uneven pitch formed on the substrate surface was measured by SEM. Moreover, the depth of the uneven | corrugated shape formed in the glass substrate after extending | stretching, and the surface roughness were measured by AFM.

FIG. 1 is an SEM photograph of a glass base material, and FIG. 2 is an enlarged photograph of FIG. As shown in FIGS. 1 and 2, it can be seen that an uneven shape is formed on the glass base material.
FIG. 3 is a scanning electron microscope (SEM) photograph of the glass substrate after stretching, and FIG. 4 is a partially enlarged view of FIG. As shown in FIG. 3 and FIG. 4, it can be seen that the uneven shape formed on the glass base material is held in a reduced state even in the stretched glass substrate. In the present example, a concavo-convex shape was formed in which the pitch of the periodic structure between the ridges and the grooves was 6.4 μm, and the step between the top of the ridges and the bottom of the grooves was 0.5 μm.

5 to 7 are observation images of the stretched glass substrate by an atomic force microscope (AFM), and FIG. 8 is a three-dimensional image formed by the atomic force microscope (AFM) of the stretched glass substrate. 5 and 8 show a range of 30 μm × 30 μm, FIG. 6 shows a range of 500 nm × 500 nm, and FIG. 7 shows a range of 100 nm × 100 nm.
The surface roughness in each region was as follows.

In the range of 30 μm × 30 μm shown in FIGS. 5 and 8 (area 900 μm ² ), Ra (arithmetic mean roughness) is 208.675 [nm] and Ry (maximum height: JIS B0601-1994) is 1.161. [Μm], Rz (ten-point average roughness: JIS B0601-1994) is 769.289 [nm], Rms (root mean square roughness: JIS B0601-1994) is 236.936 [nm], Rp (maximum peak height: JIS B0601-1994) was 660.074 [nm], and Rv (maximum valley depth: JIS B0601-1994) was 500.943 [nm].

In the range of 20 μm × 20 μm (area 400 μm ² ) shown in FIG. 5A, Ra is 209.867 [nm], Ry is 1.179 [μm], Rz is 543.942 [nm], and Rms is 239. It was 387 [nm], Rp was 652.482 [nm], and Rv was 528.468 [nm].

In the range of 10 μm × 10 μm (area 100 μm ² ) shown in FIG. 5B, Ra is 203.624 [nm], Ry is 786.288 [nm], Rz is 237.094 [nm], and Rms is 237. It was 846 [nm], Rp was 303.444 [nm], and Rv was 482.844 [nm].

In the range of 500 nm × 500 nm shown in FIG. 6 (area 250,000 nm ² ), Ra is 0.778 [nm], Ry is 7.659 [nm], Rz is 7.386 [nm], and Rms is 0.994 [ nm], Rp was 3.783 [nm], and Rv was 3.876 [nm].

In the range of 100 nm × 100 nm shown in FIG. 7 (area 10000 nm ² ), Ra is 0.351 [nm], Ry is 3.984 [nm], Rz is 3.670 [nm], and Rms is 0.455 [ nm], Rp was 1.901 [nm], and Rv was 2.083 [nm].

As described above, according to the present invention, it is possible to obtain a glass substrate in which the step between the top of the protrusion and the bottom of the groove is 2 μm or less, and Ra is 2 [nm] or less in the range of 1 μm × 1 μm. it can.
Next, the total light transmittance and scattered light transmission of the glass substrate of Example 1, a commercially available flat glass substrate (Comparative Example 3), and a substrate (Comparative Example 4) in which a transparent electrode having a texture structure is provided on the flat glass substrate. Rate, haze ratio (= scattered light transmittance / total light transmittance × 100). The results are shown in FIGS.
In the glass substrate of Example 1, the scattered light transmittance is higher in all wavelengths than in Comparative Examples 3 and 4, and the haze ratio is increased in the visible light wavelength region. For this reason, improvement of the light utilization efficiency is expected.

[Evaluation of coverage characteristics]
A thin film silicon layer was formed by plasma CVD on the surface of the glass substrate of Example 1, a substrate having a texture structure produced by sandblasting (Comparative Example 1), and a textured substrate produced by rough polishing (Comparative Example 2). Coverage characteristics were evaluated. The substrate temperature during film formation was 200 ° C., and the film thickness was 50 nm. As a result, in Comparative Examples 1 and 2, since the surface roughness in the micro region was large, the thin film silicon layer could not completely cover the substrate surface, and a portion where the glass substrate was partially exposed was seen.

On the other hand, in the case of Example 1, although the surface roughness is large in the macro region, the surface roughness is small in the micro region, so that it can be confirmed that the thin film silicon layer can completely cover the glass substrate surface. It was. That is, when a thin film solar cell is manufactured using a substrate having a large surface roughness in the micro region as in Comparative Examples 1 and 2, a short path is generated in the element, and the photoelectric conversion efficiency is greatly reduced. However, in the case of Example 1, since the surface roughness in the micro region is small, even when a very thin semiconductor film is produced, the substrate surface can be completely covered. As a result, the thin film solar cell element produced on the substrate can be covered. Since there is no short path inside, there is no decrease in photoelectric conversion efficiency.
As described above, in the method for manufacturing a glass substrate according to the present invention, a low surface roughness in a micro region that cannot be achieved by a conventional manufacturing method can be easily manufactured at low cost.

[Solar cell]
FIG. 9 is a diagram showing a solar cell 10 using the glass substrate 11 according to the present invention. Hereinafter, a method for manufacturing the solar cell 10 will be described.
First, the transparent electrode 12 is formed on at least one surface of the glass substrate 11 produced by the manufacturing method described above, on which at least the uneven shape is formed. As the transparent electrode 12, general ITO (Indium Tin Oxide), ZnO (Zinc Oxide), SnO ₂ (Tin Oxide), and those obtained by adding a dopant to them are used. In this example, 200 nm of ZnO containing Ga as a dopant was manufactured.

  Next, the semiconductor layer 13 is deposited on the produced transparent electrode 12. As a deposition method, a generally used method such as plasma CVD or thermal CVD can be applied. Depending on the application, the semiconductor layer 13 may be a material having a photoelectric conversion function, such as a polycrystalline silicon thin film, a microcrystalline silicon thin film, an amorphous silicon thin film, a CIS compound semiconductor thin film, a dye-sensitized semiconductor layer, or an organic semiconductor thin film. Can be used. In this example, a p-i-n amorphous silicon thin film having a total thickness of 500 nm was formed by plasma CVD.

  Next, a thin film such as Ag or Al is formed by sputtering or the like to produce the counter electrode 14 of the transparent electrode 12. In this example, an Ag film having a thickness of 200 nm was formed. In addition, after each layer is formed, each layer deposited by using a laser scribing method is selectively removed, and an integrated structure is provided in one substrate by forming a groove for isolation from an adjacent structure. It is also possible to increase the voltage. The solar cell 10 is produced through the above steps.

  Using three types of substrates, the glass substrate of Example 1 according to the present invention, a commercially available flat glass substrate (Comparative Example 3), and a substrate (Comparative Example 4) in which a transparent electrode having a texture structure is provided on a flat glass substrate. The solar cell of 5 mm square was prepared by the above procedure, and the short-circuit current value of the produced solar cell was measured. The cell using the substrate of Comparative Example 3 was 11.2 mA / cm 2 and the substrate of Comparative Example 4 The cell using 12.8 mA / cm 2 for the cell using 1 and 13.7 mA / cm 2 for the cell using the substrate of Example 1. In the solar cell using the substrate of Example 1, a large short-circuit current value was obtained as compared with the cells using the substrates of Comparative Examples 3 and 4, and the glass substrate according to the present invention is a conventional glass substrate. It can be seen that the light use efficiency is improved compared to

[Organic EL device]
FIG. 13 is a cross-sectional view showing an organic EL element 20A having a bottom emission structure using the glass substrate 21 according to the present invention, and FIG. 14 is an enlarged view of the XIV portion of FIG. Hereinafter, a method for producing the organic EL element 20A will be described. First, the transparent electrode 22 is formed on the flat surface opposite to the side on which the concavo-convex shape of the glass substrate 21 produced by the manufacturing method described above is formed. As the transparent electrode 22, general ITO (Indium Tin Oxide), ZnO (Zinc Oxide), SnO ₂ (Tin Oxide), and those obtained by adding a dopant to them are used. In this example, an anode made of an ITO transparent film having a thickness of 150 nm was formed from an ITO ceramic target (In ₂ O ₃ : SnO ₂ = 90 wt%: 10 wt%) using a DC sputtering method. Thereafter, ultrasonic cleaning was sequentially performed using a neutral detergent, deionized water, acetone, and isopropyl alcohol, and then the substrate was cleaned by an ultraviolet ozone method.

Next, N, N′-Di (1-naphthyl) -N, N′-diphenylbenzidine (α-NPD) placed on a transparent boat 22 in a molybdenum boat in a resistance heating vacuum deposition apparatus, and another After forming the hole transport layer 23 made of an α-NPD film having a thickness of 60 nm with Trix Aluminum (Alq3) arranged in a molybdenum processing boat, the vacuum chamber is in a reduced pressure state of 1 × 10 ⁻⁴ Pa, A light emitting layer 24 made of an Alq3 film having a thickness of 65 nm was formed thereon. Next, the cathode 25 made of Al with a thickness of 100 nm was formed by vacuum deposition with the inside of the vacuum chamber at a reduced pressure of 2 × 10 ⁻⁴ Pa, and an organic EL element 20A that emits green light (main wavelength 513 nm) was created. .

Using the glass substrate of Example 1 according to the present invention and a commercially available flat glass substrate (Comparative Example 3), a 5 mm square organic EL device was produced by the above procedure. When the front luminance when a voltage of 6 V was applied to these organic EL devices was measured, the device using the substrate of Comparative Example 3 was 1300 cd / m ² , and the device using the substrate of Example 1 was 1400 cd / m ^2. Met. The organic EL device using the substrate of Example 1 has higher luminance than the device using the substrate of Comparative Example 3, and the glass substrate according to the present invention extracts light compared to the conventional glass substrate. It can be seen that the efficiency is improved.

  In addition, although the organic EL element 20A of the bottom emission structure was produced in the present Example, you may apply to the organic EL element of a top emission structure. FIG. 15 is a cross-sectional view showing an organic EL element 20B having a top emission structure, and FIG. 16 is an enlarged view of the XVI portion of FIG. As shown in FIG. 15, the organic EL element 20 </ b> B having a top emission structure has a cathode 25, a light emitting layer 24, a hole transport layer 23, and a transparent electrode 22 formed in this order on one surface of a flat glass substrate 26. . An adhesive layer 27 is provided on the outer periphery of the surface of the glass substrate 26 on which the laminate of the cathode 25, the light emitting layer 24, the hole transport layer 23, and the transparent electrode 22 is formed, and the sealing material 28 is provided on the adhesive layer 27. By providing, the laminated body is sealed. By using the glass substrate according to the present invention for the sealing material 28, the light extraction efficiency can be improved in the same manner as the organic EL element 20A having the bottom emission structure.

  Thus, the solar cell produced using the glass substrate according to the present invention can have higher photoelectric conversion efficiency than the conventional thin film solar cell. Moreover, the organic EL element produced using the glass substrate which concerns on this invention can be set as the light extraction efficiency higher than the conventional organic EL element.

DESCRIPTION OF SYMBOLS 10 Solar cell 11 Glass substrate 11a Projection 11b Strip 12 Transparent electrode 13 Semiconductor layer 14 Counter electrode 20 Organic EL element 21, 26 Glass substrate 22 Transparent electrode 23 Hole transport layer 24 Light emitting layer 25 Cathode 27 Adhesive layer 28 Sealing material

Claims (7)

A glass substrate having a periodic repeating structure of protrusions and grooves in the longitudinal direction of at least one surface,
A glass substrate having a haze ratio of 30% or more at a wavelength of 300 nm to 800 nm.   A glass substrate having a periodic repeating structure of ridges and grooves in a longitudinal direction of at least one surface, wherein a pitch between the ridges and grooves is 200 nm to 10 μm, and the tops of the ridges and the grooves A glass substrate having a step difference of 2 μm or less from the bottom of the glass substrate. 3. The glass substrate according to claim 1, wherein an arithmetic average roughness (Ra) between the top of the protrusion and the bottom of the groove is 2 nm or less in an observation region of 1 μm ² or less. .   The glass substrate according to any one of claims 1 to 3, wherein the glass substrate has a thickness of 0.3 mm or less.   The solar cell using the glass substrate as described in any one of Claims 1-4.   An organic EL device comprising the glass substrate according to any one of claims 1 to 4 as a substrate or a sealing material.   It is a manufacturing method which manufactures the glass substrate as described in any one of Claims 1-4, Comprising: At least one surface of a glass base material forms the cyclic | annular repeating structure of a protrusion and a groove | channel, and then The glass base material is heated and stretched in the length direction of the protrusions and the grooves.