JP2002293644A - Substrate for solar cell and manufacturing method thereof, solar cell using the substrate for solar cell and solar cell clock using solar cell as clock face - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate for solar cell, which is free from defects such as chipping or crack, strain or warp and suitable for a solar cell. SOLUTION: The substrate for solar cell is a ceramic substrate obtained by sintering a molding containing powdery raw material of ceramic powder, which is prepared by mixing large sized powder and a smaller sized powder in an optional ratio with each other, and a binder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell substrate having an uneven shape, a method of manufacturing the same, a solar cell formed by using the solar cell substrate, and a solar cell clock equipped with the solar cell. .

[0002]

2. Description of the Related Art A solar cell is formed on a ceramic substrate,
Solar cell clocks in which the solar cell substrate also serves as a dial are in widespread use. By making the dial of the solar cell watch translucent, disposing the ceramic substrate on the light incident side, and controlling the light transmittance of the ceramic substrate, it is difficult to visually recognize the color and pattern of the solar cell. be able to. However, in order to make it difficult to recognize the color and pattern of the solar cell, it is necessary to lower the light transmittance of the ceramic substrate, so how efficiently the amount of light reduced by the ceramic substrate can be used for power generation of the solar cell. Whether to contribute is considered as a technical issue.

[0003] A solar cell formed on a ceramic substrate is composed of a laminated film of a lower electrode layer, a power generation layer (for example, an amorphous silicon layer) and an upper electrode layer, and transmits light to the power generation layer of the solar cell. In order to increase the amount of absorption, the above-mentioned laminated film is formed on a substrate having a surface having an uneven shape to improve the photoelectric conversion efficiency. The translucent ceramic substrate is formed by adding 0.01% to the ceramic raw material.
A molded body in which fine powder having a constant average particle size of about 1 μm is densely arranged is sintered to form a ceramic substrate in which pores are minimized. Secondary processing such as blasting can be performed on the ceramic substrate to form a ceramic substrate having an uneven surface.

[0004] A specific configuration and a manufacturing method thereof will be described with reference to FIG. A substrate structure that can improve the power generation efficiency most in the conventional solar cell substrate is provided on the surface of the first uneven step portion 1 as shown in FIG. Transparent ceramic substrate 5 having 2
8 If the solar cell is formed on the substrate using the substrate, light is scattered at the interface with the laminated film due to the shape of the first and second large and small uneven portions provided on the surface of the substrate. The optical path length in the layer can be increased, and the short-circuit current and photoelectric conversion efficiency of the solar cell can be improved.

[0005] The manufacturing method is described below. In the translucent ceramic substrate 58 having a smooth surface shown in FIG. 3A, a ceramic fine powder having an average particle diameter of 1 μm is used in order to reduce the content of pores. For example, when the ceramic fine powder is alumina after sintering, sintering at about 1800 degrees can obtain a light transmittance of about 30%.

As a method for forming the first and second large and small uneven steps, sandblasting is performed twice. Specifically, as shown in FIG. 3A, the first sandblasting process is performed on the surface of the smooth translucent ceramic substrate 58 using the first abrasive grains 60 having a particle size of 50 μm or more. By forming a first uneven step portion 1 in which the average step d1 shown in (b) becomes 3 μm or more and performing a second sandblasting process using the second abrasive grains 62 having a particle size of 20 μm or less, FIG. The first uneven step portion 1 shown in FIG.
A translucent ceramic substrate 60 having a solar cell forming surface 64 having a second uneven portion 2 having an average step d2 of 0.5 μm or less can be obtained on the surface of the substrate.

[0007]

However, in the prior art method, the surface of the translucent ceramic substrate is
Damage caused by the first abrasive grains 60 having a particle size of 50 μm or more causes many chips and cracks to be generated irregularly, and the surface can be processed into a relatively smooth surface by the second sandblasting, but the defects are completely removed. A transparent solar cell substrate cannot be formed.

Further, since the blasting process generally causes distortion and warpage of the blasted object, there is a problem that the degree of distortion and warpage is further increased by performing the sandblasting process on the substrate twice. In particular, when it is mounted on a solar battery timepiece that also serves as a dial, it may be broken by a shock while being carried, and thus lacks reliability.

An object of the present invention has been made in view of the above technical problems, and includes a defect such as a chip or a crack;
Solar cell substrate having first and second uneven steps suitable for a solar cell that does not warp, a method of manufacturing the same, a solar cell configured using the solar cell substrate, and the solar cell It is to provide a solar cell clock equipped with.

[0010]

Means for Solving the Problems The solar cell substrate of the present invention is a solar cell substrate comprising: a ceramic powder raw material powder in which a large powder and a smaller powder are mixed at an arbitrary ratio; Characterized in that it is a ceramic substrate obtained by sintering a molded body containing:

In the solar cell substrate of the present invention, the large powder has a particle diameter of 3 to 6 μm, and the small powder has a particle diameter of 0.3 to 6 μm.
5 to 1 μm particles, the raw material powder of the ceramic powder is composed of 80 to 95% by weight of the whole, and the binder is composed of 20 to 5% by weight of the whole organic binder. Features.

[0012] The substrate for a solar cell according to the present invention is characterized in that the surface of the ceramic substrate has a first uneven portion having an average step of 3 μm or more.

The solar cell substrate of the present invention is characterized in that a second uneven step smaller than the first uneven step is formed on the surface of the first uneven step.

The solar cell substrate according to the present invention is characterized in that the second uneven step portion is constituted by an average step smaller than the thickness of the power generation layer of the solar cell formed on the ceramic substrate. .

The solar cell substrate according to the present invention is characterized in that the second uneven portion is formed by abrasive grain processing.

The solar cell substrate of the present invention is characterized in that the abrasive processing is a sand blast method or a liquid honing method.

The solar cell substrate according to the present invention is characterized in that the ceramic substrate has a sintering temperature of 1700 to 1900 ° C. and the ceramic substrate has a transmittance of 20 to 50%.

The method for manufacturing a solar cell substrate according to the present invention comprises the steps of: forming a substrate-like molded body containing a ceramic powder raw material powder and a binder in which a large powder and a smaller powder are mixed at an arbitrary ratio. The method includes a step of forming and a step of firing the molded body to form a sintered body.

The method for manufacturing a solar cell substrate according to the present invention is characterized in that the sintered body is subjected to abrasive grain processing to form a second uneven step portion.

In the method for manufacturing a solar cell substrate according to the present invention, the abrasive processing is a sandblast method or a liquid honing method.

A solar cell according to the present invention is characterized by using the solar cell substrate.

The solar battery timepiece according to the present invention is characterized in that the solar battery substrate is a dial.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The translucent solar cell substrate of the present invention forms a plate-like molded body with a large powder having a size of 3 to 6 μm and a small powder having a size of 0.5 to 1 μm. It is a ceramic substrate formed by sintering. Since the ceramic substrate is a substrate in which small powders are densely filled in gaps between large powders, the light transmittance can be easily controlled by the firing temperature of the molded body.

The manufacturing method will be described. Particle size 3-6 μm
Of 80 to 95% by weight of a ceramic powder raw material powder obtained by mixing particles having a particle size of 0.5 to 1 μm at an arbitrary ratio;
With an organic binder of 0 to 5% by weight, the average step height is 3 μm.
A molded body having the first uneven portion 1 having a height of m or more was formed. The molded body was controlled and fired at 1700 to 1900 ° C. to produce a sintered body having a desired transmittance of 20 to 50%. Thereafter, the surface of the first uneven step portion 1 is subjected to blast processing only once to form a structure in which the second uneven step portion 2 having an average step less than or equal to the thickness of the power generation layer of the solar cell is formed. Defects, distortion, and warpage of the substrate caused by the conventional twice blasting process can be minimized.

The structure of the solar cell formed on the surface of the translucent solar cell substrate and the effect thereof will be described with reference to FIG. FIG. 1B is a cross-sectional view of an amorphous silicon solar cell formed by using the substrate for a light-transmitting solar cell according to the manufacturing method of the present invention. In the solar cell 42 formed according to the present invention, the second uneven step portion 2 having an average step of not more than the thickness of the power generation layer of the solar cell was formed on the surface of the first uneven step 1 having an average step of 3 μm or more. A transparent conductive film 28 as a lower electrode layer and an amorphous silicon film 3 as a power generation layer are formed on the solar cell forming surface 26 of the translucent solar cell substrate 24.
8. A metal film 40 of Al, Ag or the like is sequentially laminated as an upper electrode layer. The amorphous silicon film 38 is composed of an amorphous silicon carbon p-layer (hereinafter abbreviated as a p-layer) 3
0, an amorphous silicon carbon buffer layer (hereinafter abbreviated as b layer) 32, an amorphous silicon i layer (hereinafter abbreviated as i layer) 34, and an amorphous silicon n layer (hereinafter abbreviated as n layer) 36. It is.

The second uneven step portion 2 has an effect of scattering light at the interface of the laminated film. For example, light can be scattered at the interface having a large difference in refractive index (n). That is, the light guided at the interface between the transparent conductive film (n = 1.9) and the amorphous silicon film (n = 3.5) is scattered more. The refracted light is guided obliquely through the i-layer 34, so that the optical path length can be made longer than when the light is guided vertically, and as a result, the i-layer As a result, the short-circuit current can be increased.

The light scattering effect can be further increased by setting the second uneven step portion 2 to be large so as to increase the unevenness at the interface of the laminated film. If the thickness is larger than the thickness of the film 38 (generally, about 0.5 μm), the metal film 40 of the upper electrode layer and the transparent conductive film 28 of the lower electrode layer are likely to be short-circuited. Therefore, the second uneven step portion 2
Needs to be less than the thickness of the power generation layer of the solar cell.

The first uneven step portion 1 not only scatters light but also has the effect of causing the reflected light of the light once transmitted through the amorphous silicon film 38 and reflected by the upper electrode 40 to enter the amorphous silicon film 38 again. Average step 3μm
It is a well-known fact that the effect is remarkable as described above.

As is clear from the above description, the average step of the second uneven step 2 is set to be equal to or less than the thickness of the power generation layer of the solar cell, and the average step of the first uneven step 1 is set to 3 μm or more. Thus, an optimum light scattering effect can be obtained without short-circuiting the upper and lower electrode layers.

(Embodiment 1) Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 (a)-
2C is a process cross-sectional view illustrating the method for manufacturing the translucent solar cell substrate of the present invention, and FIG. 2A is a schematic cross-sectional view of a solar cell using the substrate manufactured according to the embodiment of the present invention. FIG. 2B is a schematic cross-sectional view of a solar cell timepiece equipped with a solar cell using a substrate prepared according to an embodiment of the present invention.

First, a method for obtaining a ceramic sintered body having irregularities with an average step of 3 μm or less on the surface will be described with reference to the case where alumina (Al ₂ O ₃ ) is used as a ceramic raw material.

First, a substrate-like molded body 44 as shown in FIG. 1A was prepared. The molded body 44 is formed by mixing alumina particles 46 having a particle diameter of 3 to 6 μm, alumina powder obtained by mixing alumina particles 48 having a particle diameter of 0.5 to 1 μm at a ratio of 70% by weight and 30% by weight, and an organic binder 50 as an organic material. After kneading with the solvent, a molded body 44 was formed on the substrate using a doctor blade method. The molded body 44 is preferably formed with the alumina powder in the range of 80 to 95% by weight and the binder 50 in the range of 20 to 5% by weight. The same applies when other ceramic raw materials are used.

Since the particle size of the alumina powder greatly affects the surface shape of the sintered body, it is important to select the particle size of the powder to obtain an appropriate mixing ratio. Is done.

The alumina particles 48 having a particle size of 0.5 to 1 μm exist so as to fill gaps between the alumina particles 46 having a particle size of 3 to 6 μm, thereby reducing defects and voids in the sintered body.
In order to increase the strength by increasing the density, FIG.
It is desirable to make the compact 44 as close as possible to the closest packing as shown in FIG.

The binder 50 is used to enhance the moldability, plasticity and adhesiveness during molding, and to firmly bind the respective ceramic powders until the ceramic powders are sintered. For example, the binder 50 is made of polymethacrylate. And dibutyl phthalate.

Next, the molded body 44 was placed in an electric furnace for 2 hours.
After decomposing and evaporating the binder 50 at around 00 to 600 ° C., the binder 50 is fired at 1700 to 1900 ° C. to reduce the average step D1 of the first uneven step portion 1 having a transmittance of 20 to 50% by 3 to 3.
A sintered body 52 having a thickness of not less than μm was obtained. The transmittance can be easily controlled by the firing temperature.

Further, since the sintered body surface 54 of the sintered body 52 is formed by sintering alumina particles, a substrate subjected to sandblasting using abrasive grains having a particle diameter of 50 μm or more according to a conventional method is used. A substrate having a smooth surface with less cracks and defects than the surface of the substrate can be formed.

Next, as shown in FIG. 1B, the surface 54 of the sintered body was subjected to abrasive processing by a wet liquid honing process. Since the wet liquid honing process sprays water containing abrasive grains on the workpiece, the workability is good when small abrasive grains 56 are used, and the workpiece can be ground while being washed with water. Subsequent cleaning of the substrate is also facilitated. The conditions of the wet liquid honing treatment are as follows:
Using alumina abrasive grains 56 of μm or less, projection distance 20 m
m, the projection angle was 90 °, the processing speed was 10 mm / sec, the air pressure was about 0.8 to 1.2 kg / cm ^2, and the size of the injection port was set according to the size of the substrate to be processed. The same effect can be obtained by using silicon carbide (SiC) for the alumina abrasive grains 56.

A similar shape can be obtained by performing the above-described abrasive grain processing by sandblasting using alumina abrasive grains 56 having a particle size of 20 μm or less.

Further, by subjecting the sintered body surface 54 to the above-described abrasive processing, a translucent solar cell substrate 24 as shown in FIG. 1C is obtained. Has a second uneven portion 2 formed on an uneven surface having an average height of 3 μm or more, and the average height D2 is 0.5 μm.
m or less.

As described above, the translucent solar cell substrate 24
Can be formed by performing blasting using small abrasives only once on a sintered body 52 having a smooth surface, so that damage to the substrate caused by the abrasives can be suppressed as much as possible, and distortion and warpage can be prevented. As a result, a ceramic substrate with few chips and cracks on the solar cell forming surface 26 was formed.

Although the case where alumina was used for the ceramic raw material powder was described, magnesia (Mg
O), zirconia (ZrO ₂ ) or the like can be used to form the light-transmitting solar cell substrate of the present invention.

Example 2 A lower electrode layer was formed on the solar cell formation surface 26 of the translucent solar cell substrate 24 manufactured in Example 1 by using, for example, a sputtering apparatus as shown in FIG. Tin oxide (hereinafter referred to as ITO), tin oxide (hereinafter SnO ₂ ), zinc oxide (ZnO)
80 nm thick transparent conductive film 28, plasma CVD
Amorphous silicon film 38 as a power generation layer by using the apparatus
Was formed to a thickness of about 500 nm, and a metal film 40 of Al or Ag was sequentially formed as an upper electrode layer with a thickness of 1 μm using a sputtering device or the like, whereby a solar cell 42 was obtained. Light incident from the transparent conductive film 28 side is added with the scattering effect of the large uneven step portion to the scattering effect of the small uneven step portion 2, and the optical path length in the amorphous silicon film 38 increases, thereby increasing the short-circuit current. It is known that the photoelectric conversion efficiency of the solar cell can be improved.

Hereinafter, a specific method of manufacturing the power generation layer will be described. The amorphous silicon film 38 has an amorphous silicon carbon p-layer (hereinafter abbreviated as p-layer) 30 having a thickness of 1
2 nm, b layer (amorphous silicon carbon composition change layer, hereinafter ab layer) 32 has a thickness of 15 nm, and amorphous silicon i layer (hereinafter abbreviated as i layer) 34 has a thickness of 400 n.
m, n-layer of amorphous silicon (hereinafter abbreviated as n-layer) 36
Are laminated in the order of the thickness of 40 nm. The conditions for forming each layer are described below. The p-layer 30 has a substrate temperature of 225 ° C. and a power of 0.02.
W / cm ² , pressure 120 Pa, gas flow rate is SiH ₄ / CH
45/105 / 45s in the order of ₄ / B ₂ H ₆ (2% H ₂ dilution)
ccm. The b layer 32 has a substrate temperature of 225 ° C., a power of 0.02 W / cm ² , a pressure of 120 Pa and a gas flow rate of Si.
300/300 / 300scc in the order of H ₄ / CH ₄ / H ₂
m. The i-layer 34 has a substrate temperature of 225 ° C. and a power of 0.
05W / cm ² , pressure 80Pa, gas flow rate is 6 for SiH ₄
00 sccm. The n layer 36 has a substrate temperature of 225 ° C., a power of 0.05 W / cm ² , a pressure of 120 Pa, and a gas flow rate of 400/40 s in the order of SiH ₄ / PH ₃ (2% H ₂ dilution).
Performed at ccm.

The characteristics of the solar cell 42 formed as described above include a short-circuit current of 47.1 μA / cm ² , an open voltage of 0.64 V, a fill factor of 0.73, and a photoelectric conversion efficiency of 15.
1% could be obtained. This characteristic is not inferior to the characteristics of a solar cell formed on a ceramic substrate for a solar cell manufactured using a conventional technique, and the substrate for a translucent solar cell according to the manufacturing method of the present invention has irregularities. After making a ceramic sintered body, 1
By performing the blasting process twice, chipping and cracking caused by the abrasive processing can be suppressed, and the problems of substrate distortion and warpage can be solved. Substrate cracking does not occur in subsequent handling.

Further, by the one blast process,
A surface shape suitable for a translucent solar cell substrate can be realized on a ceramic substrate.

Example 3 Further, as shown in FIG. 2 (b), the light-transmitting side of the solar cell clock 14 is formed by using the translucent solar cell substrate 24 of the solar cell manufactured in Example 2 as a dial. To place. Since the dial has translucency, light required for power generation passes through the solar cell. As mentioned above, the dial is chipped and cracks are suppressed, and the problems of substrate distortion and warpage have been solved, so that not only the impact resistance as a watch dial is improved, but also the reliability is improved. Confirmed that there was no problem.

[0048]

As described above, the substrate for a translucent solar cell formed by the present invention has a ceramic substrate formed of a large powder of 3 to 6 μm and a small powder of 0.5 to 1 μm. Since the substrate is a substrate in which small powders are densely filled in the gaps between the bodies, a substrate for a translucent solar cell whose light transmittance can be easily controlled by the firing temperature of the molded body can be provided.

Further, since the second irregularity step 2 can be formed by performing the abrasive processing only once on the surface of the first irregularity step 1 formed at the stage of the ceramic sintered body, a large and small step difference can be obtained. Transparent solar cell substrate without warping, distortion, and cracking, without causing defects such as chipping or cracking in the substrate, and the method for producing the same and the light transmission thereof, while maintaining the effect on the solar cell due to the unevenness of A solar cell constituted by using a conductive solar cell substrate could be provided. Furthermore, high reliability with excellent impact resistance was obtained even when the solar cell watch was mounted on a solar cell timepiece also serving as a dial.

Further, the light-transmitting solar cell substrate formed by the present invention enables more efficient power generation of the solar cell due to the unevenness formed on the substrate even when the transmittance of incident light is reduced. Therefore, it was possible to obtain a solar cell clock in which the color of the solar cell and the visibility of the pattern were reduced.

The solar cell of the present invention can be applied not only to a solar cell clock, but also to any electronic device equipped with a solar cell.

[Brief description of the drawings]

FIG. 1 is a process cross-sectional view illustrating a method for manufacturing a light-transmitting solar cell substrate according to an embodiment of the present invention.

FIG. 2 is a structural sectional view showing a solar cell and a solar cell watch in an embodiment of the present invention.

FIG. 3 is a process cross-sectional view illustrating a method for manufacturing a conventional translucent solar cell substrate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st uneven | corrugated step part 2 2nd uneven | corrugated step part 14 solar cell clock 24 translucent solar cell substrate 26 solar cell formation surface 28 transparent conductive film 30 p layer 32 b layer 34 i layer 36 n layer 38 amorphous silicon Film 40 metal film 42 solar cell 44 molded body 46 alumina particles having a particle size of 3 to 6 μm 56 alumina particles having a particle size of 0.5 to 1 μm 50 binder 52 sintered body 54 sintered body surface 56 abrasive grains

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 31/04 P

Claims (13)

[Claims] 1. A ceramic substrate obtained by sintering a ceramic powder raw material powder in which a large powder and a smaller powder are mixed at an arbitrary ratio, and a molded body containing a binder. A substrate for a solar cell, comprising: 2. The method according to claim 1, wherein the large powder has a particle size of 3 to 6 μm, the small powder has a particle size of 0.5 to 1 μm, and the raw material powder of the ceramic powder comprises 80 to 95% by weight of the whole. 2. The solar cell substrate according to claim 1, wherein the binder is composed of 20 to 5% by weight of an organic binder. 3. 3. The solar cell substrate according to claim 1, wherein the surface of the ceramic substrate has a first uneven portion having an average height of 3 μm or more. . 4. The solar cell substrate according to claim 3, wherein a second uneven step smaller than the first uneven step is formed on the surface of the first uneven step. 5. The method according to claim 4, wherein the second uneven step portion has an average step smaller than a thickness of a power generation layer of the solar cell formed on the ceramic substrate. Substrate for solar cells. 6. The solar cell substrate according to claim 5, wherein the second uneven step portion is formed by abrasive processing. 7. The method according to claim 6, wherein the abrasive processing is a sand blast method or a liquid honing method.
Item 10. The solar cell substrate according to item 9. 8. The sintering temperature of the ceramic substrate is 17
00-1900 ° C., and the ceramic substrate is 20-5
The solar cell substrate according to any one of claims 1 to 7, wherein the substrate has a transmittance of 0%. 9. Large powder and smaller powder,
It is characterized by comprising a step of forming a substrate-like molded body containing a ceramic powder raw material powder and a binder mixed at an arbitrary ratio, and a step of firing the molded body to form a sintered body. A method for manufacturing a solar cell substrate. 10. The method for manufacturing a solar cell substrate according to claim 9, wherein said sintered body is subjected to abrasive processing to form a second uneven step portion. 11. The method for manufacturing a solar cell substrate according to claim 10, wherein the abrasive processing is a sand blast method or a liquid honing method. 12. A solar cell using the solar cell substrate according to claim 1. 13. A solar cell watch according to claim 12, wherein said solar cell substrate is a dial.