JPH1174548A - Solar battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a light utility efficiency, by forming a diffuse reflecting surface formed in a selective protrusion and recess shape on a surface formed with a transparent conductive film, thereby enhancing a ratio of an optical confinement in a layer due to a random reflection on a junction surface. SOLUTION: To form a diffuse reflecting surface 5, a surface of a solar battery board 1 at a transparent conductive film side is honed with liquid. This is a processing for spraying water containing abrasive from a nozzle to a work piece, thereby forming the surface of the board being flat to an elementary surface having a desired protrusion and recess shape. At this time, the abrasive having predetermined type, particle size and the like is selected. And, the other working conditions are selectively controlled to perform sufficient optical confinement effect. And, according to a liquid honing method, the board 1 is polished while cleaning it, and hence a worked surface is clean and a cleaning step can be simplified. Thereafter, a transparent conductive film 2 and an a-Si film 3 are formed on the diffuse reflecting surface 5 formed to be the elementary surface, and a metal electrode film 4 is formed by vacuum vapor deposition or sputtering.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell in which an electrode and an amorphous silicon film are laminated on a solar cell substrate, and a method of manufacturing the same. It is about watches.

[0002]

2. Description of the Related Art Solar cells formed by laminating electrodes and an amorphous silicon film on a transparent solar cell substrate are used in various electronic devices today. The basic structure is as shown in FIG. 2, where 21 is a transparent solar cell substrate, 22 is a transparent conductive film formed on the solar cell substrate 21, and 23 is a P-I-N formed on the transparent conductive film 22. A junction type amorphous silicon film (abbreviated as an a-Si film), 24 is a metal electrode film formed on the a-Si film 23. When light is incident from the solar cell substrate 21 side, free electrons and holes are generated in the a-Si film 23, and the transparent conductive film 22 is generated by the electric field created by the PIN junction.
And the metal electrode film 24 to generate a voltage. The electromotive force of such a solar cell is 0.4 ~
For example, when used as a power source for an electronic wristwatch, the voltage is not enough to operate the circuit, so that a plurality of solar cells (for example, for four) are mounted on a substrate. A configuration is adopted in which these elements are arranged and these elements are connected in series to obtain an added electromotive force.

In order for the solar cell to efficiently generate power, it is necessary that incident light from the solar cell substrate 21 reaches the a-Si film without loss and performs a photoelectric action. But,
The bonding surface between the solar cell substrate 21 and the transparent conductive film 22 or the bonding surface between the transparent conductive film 22 and the a-Si film 23 is a boundary surface between layers having different optical characteristics. There is a portion that is reflected by the surface and does not reach the a-Si film 23 and does not contribute to power generation. If the bonding surface is flat, total reflection is likely to occur depending on the incident angle of light. Therefore, it is effective to make the joint surface a surface with many irregularities, that is, a rough surface, in order to enhance the light use efficiency. By making the bonding surface rough, the amount of light that passes through the bonding surface without being reflected increases, and light that once passes through the bonding surface is likely to be reflected to the next bonding surface and emitted to the outside However, the rate of reflection at the joining surface again and remaining inside increases. It has a so-called light confinement effect.

[0004] To improve the performance of the solar cell, that is, to improve the light confinement effect by roughening the bonding surface, is described in, for example, "Amorphous Silicon Solar Cell on Textured" in a paper submitted at the "9th International Conference on Photovoltaic Power Generation (1996)". T
empered Glass Substrate (Taniguchi et al.), SnO _{2 has been} conventionally used as the transparent conductive film 22.
One method is to form a film on the solar cell substrate 21 by crystallization by a CVD method, roughen the SnO ₂ film by selecting film forming conditions, and use this.

[0005]

However, as described in the above-mentioned paper, the formation of the SnO ₂ film requires 500 ° C.
Since it is necessary to perform the CVD method at such a high temperature, glass having a high softening point must be used, and the cost has increased. Therefore, the above-mentioned paper shows a method of obtaining a necessary rough surface at room temperature by forming a rough surface by sandblasting a film forming surface of the solar cell substrate 21 instead of forming a rough surface with the transparent conductive film 2. According to this, it is sufficient to form an ITO film by a sputtering method instead of forming a SnO ₂ film as a transparent conductive film on a solar cell substrate by a CVD method as in the related art.

[0006] However, in order to obtain the desired surface roughness, it is necessary to ensure that both large and small abrasives reach the work surface. However, in sandblasting, the abrasive is sprayed from a nozzle. Due to the air resistance, it is difficult to reach the processing surface, it is difficult to control the surface roughness, and the variation in the roughness increases. Further, since many abrasive fine particles and shaved polishing dust adhere to the surface of the solar cell substrate by spraying, a careful cleaning step must be provided after the treatment, which has contributed to an increase in manufacturing cost. The present invention addresses these problems.

[0007]

According to the present invention, the surface of a solar cell substrate is roughened, that is, a diffusion having a selective unevenness is formed on at least the surface of the solar cell substrate on which a transparent conductive film is formed. The present invention is characterized in that a reflection surface is formed, and a liquid honing method is used to form a diffuse reflection surface. This is a method in which water containing an abrasive is sprayed onto the processing surface, so that the abrasive with a small particle size can reliably reach the processing surface by riding on the water flow, and the surface roughness can be controlled more easily than in the sandblasting method. Become. In addition, since the abrasive and the water are sprayed, the polishing and the cleaning are performed at the same time. Therefore, the surface after processing has a high degree of cleanliness, and the post-process can be performed by simply cleaning. This facilitates processing, provides a bonding surface with a large light confinement effect, and improves the performance of the solar cell.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the solar cell of the present invention,
In forming the diffuse reflection surface 5 shown in FIG. 1, the surface of the solar cell substrate 1 on the transparent conductive film side is formed by liquid honing. This is a process in which water containing an abrasive is sprayed from a nozzle onto a workpiece, thereby making the flat solar cell substrate surface rough with desired irregularities. At this time, the abrasive is selected of a predetermined type, particle size and the like, and by selectively controlling other processing conditions,
It is possible to achieve a sufficient light confinement effect.

Further, as described above, since liquid honing is equivalent to grinding while washing with water, the processing surface has little adhesion of abrasive grains and dirt, and it is only necessary to simply wash after processing.

Further, since the diffuse reflection surface 5 formed on the solar cell substrate surface by this method has a desired light confinement effect, the power generation characteristics of the solar cell can be improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. First, in forming the diffuse reflection surface 5 shown in FIG. 1, the surface of the solar cell substrate 1 on the side of the transparent conductive film 2 is formed by a liquid honing method. A borosilicate glass substrate was used. Alumina A # 2 is used as an abrasive.
000 (maximum particle diameter 19 μm), and the processing conditions were:
The air pressure ^{1.2~1.8Kgf / cm 2, 0.8~1.0Kgf / cm} 2 the pump pressure, projection angle 90 degrees, the processing count was 1-5 times.

FIG. 3 shows an example of the result. The vertical axis shows the average roughness (Ra), and the horizontal axis shows the relationship between the discharge pressure, ie, the pump pressure and the air pressure. As is clear from this figure, by controlling the number of treatments and the discharge pressure,
The diffuse reflection surface 5 having an effective light confinement effect as compared with the related art was able to be formed. Although alumina was used as the polishing agent, it goes without saying that the polishing agent is not limited to this as long as it has a desired light confinement effect.

Next, indium tin oxide (IT) which is the transparent conductive film 2 is formed on the diffuse reflection surface 5 formed on the roughened solar cell substrate by sputtering.
O) Form a film. Further, an a-Si film 3 is formed thereon by a CVD method, and a metal electrode film 4 is formed by vacuum deposition or sputtering. Thereafter, a solar cell is completed by applying a protective film or the like as necessary.

As described above, when the solar cell according to the present invention was evaluated, the conversion efficiency of the power generation characteristics was measured to be 12 to 13% (on ITO) and 18 to 20% in absolute value.
(On SnO 2), the characteristics were improved. From this, according to the solar cell of the present invention, a remarkable effect is obtained in the power generation characteristics as compared with the conventional solar cell.

[0015]

According to the solar cell obtained by the present invention, since the bonding surface of the laminated portion, that is, the diffuse reflection surface has an uneven shape, light is irregularly reflected on the bonded surface and confined in the laminated portion. Efficiency is increased, and light utilization efficiency is increased. In addition, according to the liquid honing method, since the grinding is performed while cleaning, the processed surface is clean and the cleaning process can be simplified.

In the method of sand blasting a solar cell substrate, fine abrasive particles do not reach a processing surface due to air resistance, causing a variation in surface roughness. According to the above-mentioned paper, the solar cell substrate was sand blasted. The performance of solar cells is
Although not necessarily equivalent to that of the structure in which the SnO ₂ film is roughened, the solar cell of the present invention using the liquid honing method can reliably apply the fine abrasive particles to the processing surface together with the water flow, The surface roughness of the diffuse reflection surface in the solar cell substrate can be finely controlled, and an effect that a performance approaching that of a solar cell using a SnO ₂ film can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a solar cell according to the present invention.

FIG. 2 is a cross-sectional view of a conventional solar cell.

FIG. 3 is a diagram showing a relationship between an average roughness and a discharge pressure.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 solar cell substrate 2 transparent conductive film 3 a-Si film 4 metal electrode film 5 diffuse reflection surface

Claims (2)

[Claims] 1. A solar cell comprising a transparent conductive film, an amorphous silicon film and a metal electrode film laminated on a solar cell substrate, wherein at least a surface of the solar cell substrate on which the transparent conductive film is formed is formed. Is a solar cell having a diffuse reflection surface having a selective uneven shape. 2. A method for manufacturing a solar cell, comprising laminating a transparent conductive film, an amorphous silicon film, and a metal electrode film on a solar cell substrate, wherein at least the transparent conductive film of the solar cell substrate is formed. A method for manufacturing a solar cell, characterized in that a diffuse reflection surface having a concave-convex shape is selectively formed on a surface of the substrate by a liquid honing method.