JPH08287969A - Photocell - Google Patents

Abstract

PURPOSE: To get a photocell equipped with an electrode on the side of incoming light where photoelectric conversion efficiency is raised and besides the electric resistance is lowered by preventing the interruption of light by metal. CONSTITUTION: For a photocell, the cross section has an acute edge on the side of incoming light. Besides, the photocell is equipped with an electrode on the side of incoming light, which has a metallic electrode 2 where the irradiated face of the incoming light is a mirror face, photoelectric convertor bodies 3 and 4, and a counter electrode 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic cell having an incident light side electrode which enhances light-electricity conversion efficiency.

[0002]

2. Description of the Related Art In a conventional photovoltaic cell, a transparent electrode such as an ITO film or a SnO ₂ film is directly used as an electrode on the incident light side.

In addition, a striped metal such as lead was used as a current collecting electrode in contact with a transparent electrode such as an ITO film or a SnO ₂ film.

[0004]

However, in the conventional photovoltaic cell, an ITO film or Sn is used as an electrode on the incident light side.
When only a transparent electrode such as an O ₂ film is used, there is a problem that the electric resistance of the electrode itself is large.

When a striped metal is used as a current collecting electrode in contact with the transparent electrode, the metal causes
There has been a problem that the irradiation of light to the main body of the photoelectric conversion element is hindered.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a photovoltaic cell provided with an incident light side electrode which prevents light from being blocked by a metal to improve light-to-electricity conversion efficiency and which has reduced electric resistance.

[0007]

In order to achieve the above object, the photovoltaic cell of the present invention comprises a metal electrode whose cross-sectional shape has an acute-angled edge on the incident light side and whose incident light irradiation surface is a mirror surface. An incident light side electrode having, a light-electricity conversion element body,
And a counter electrode.

The shape of the metal electrode is a plurality of linear shapes.

Further, the plurality of linear metal electrodes have a striped shape or a grid shape.

Further, the metal electrode is in electrical contact with the transparent electrode.

Further, the metal electrode is characterized in that the light irradiation surface is embedded in the transparent substrate.

[0012]

The light radiated to the electrode portion is provided by having a metal electrode whose cross-sectional shape has an acute angle edge on the incident light side and whose light irradiation surface is a mirror surface as an electrode on the incident light side of the photocell. After being reflected on the surface of the electrode, it reaches the inside of the photovoltaic cell.

A description will be given below with reference to FIG. 3, which is an optical path diagram showing the reflection direction of incident light. A shape whose cross-sectional shape has an acute-angled edge on the incident light side can be approximated by an acute-angled isosceles triangle shown in FIG.

When the base length of the acute-angled isosceles triangle is 2x, the height is y, and the diagonal size of the base is 2θ, the light a incident perpendicularly on the base of the triangle is relative to the perpendicular of the base. 2θ
Reflected in the direction of. When 2θ is less than 90 °, the reflected light travels to the bottom side (that is, the photocell side), and if it does not hit the electrode of the adjacent acute-angled isosceles triangle, it can go into the photocell and be used for power generation. When 2θ is 90 ° or more, the reflected light hits the adjacent electrode and is further reflected, and goes out of the photocell. Therefore, the diagonal 2θ of the base is limited to an acute angle. Also, the light incident on the apex of the acute-angled isosceles triangle is y · tan2 in the direction parallel to the base until it reaches the base.
θ advance. Therefore, when arranging acute-angled isosceles triangles,
If the period is set to x + y · tan 2θ (= Y) or more, all vertically incident light can be introduced into the photocell.

For example, for simplicity, when x = 1,
Y = 1 + y · tan2θ = 1 + y {2tanθ / (1-
tan ² θ)} = 1 + 2 / (1-1 / y ² ), and y
Is larger, Y is smaller, and approaches 3. This is
It is shown that when the height of the electrodes is increased to infinity, all the vertically incident light is reflected and reaches the inside of the battery even if the electrode interval is made as close as 1/2 of the base of the triangle.

Next, consider the optical path of the light b incident at an angle of δ with respect to the vertical direction of the base of the acute-angled isosceles triangle. From FIG. 3, the light incident on the apex of the acute-angled isosceles triangle reaches y · tan in the direction horizontal to the base until it reaches the base.
Proceed by (2θ + δ). Therefore, if the period of the acute-angled isosceles triangle is x + y · tan (2θ + δ) or more, all incident light distributed within δ ° from the direction perpendicular to the base can be introduced into the photocell. However,
In a region where δ is sufficiently larger than θ, it is impossible to expect light to enter the inside of the photocell due to reflection, and only light that reaches directly can be used. Then, in this case, the larger y is, the more the triangle becomes an umbrella, and it becomes difficult for direct light to reach the inside of the photovoltaic cell.

From the above, it can be seen that the size of y, that is, the height of the metal electrodes, and the triangle, that is, the distance between the metal electrodes, may be determined according to the angle change of the incident light at the place where the photovoltaic cell is used.

Then, by making the shape of the metal electrode into a plurality of linear shapes, more preferably stripes or grids,
An incident light side electrode having a low electric resistance which prevents light from being blocked can be obtained.

By forming this metal electrode on the transparent electrode, the electric resistance of the incident light side electrode can be further reduced.

Furthermore, by embedding the light irradiation surface of the metal electrode in the transparent substrate, the mirror surface of the metal electrode can be protected and the transparent substrate can be used as a case member of a photovoltaic cell.

[0021]

The photocell of the present invention will be described below with reference to the drawings by taking a dye-excited photocell as an example.

First, a striped metal electrode used as a collector electrode of a transparent electrode of a photovoltaic cell was prepared. FIG. 1 is a sectional view of the striped metal electrode. In the figure, 1 is a transparent silica glass substrate, and 2 is a striped metal electrode formed on the silica glass substrate 1.

That is, length 30 mm, width 40 mm, thickness 5 m
m transparent silica glass substrate 1 was prepared. Then, one side of this silica glass substrate is processed to have a bottom length of 0.
A plurality of grooves having an isosceles triangular cross section shown in Table 1 with 5 mm, apex angle (2θ), and height and spacing were prepared. next,
After silver was vapor-deposited in these grooves, lead was poured into the groove to prepare a striped metal electrode embedded in a transparent silica glass substrate, the surface in contact with the silica glass substrate, that is, the light irradiation surface was a mirror surface.

Here, the sheet resistance and the light transmittance of the obtained striped metal electrode were measured. That is, the area resistance was obtained by measuring the resistance value of the surface of the silica glass substrate on which the striped metal electrodes were formed in the direction in which the metal electrode was extended, and determining the area resistance of the silica glass surface.

The light transmittance was measured by measuring the amount of light transmitted when light in the Z direction shown in FIG. 1, which was perpendicular to the silica glass surface on which the striped metal electrodes were formed, was applied. Then, on the basis of the amount of light transmission in the case of the unprocessed transparent silica glass alone, the entire surface light transmittance in the case of irradiating light onto the entire surface of the silica glass on which the striped metal electrodes were formed was determined. Based on this value, the light transmittance of the metal portion in the case where light was irradiated only to the S portion shown in FIG. 1, that is, the striped metal electrode portion was calculated. Table 1 shows the above results.

[0026]

[Table 1]

As is clear from Table 1, the entire surface light transmittance is 97 to 99% by making the cross section of the groove an acute triangle.
In addition, the metal partial light transmittance can be increased to 94 to 98%. Further, the sheet resistance is, for example, 0.1 to 0.00 while the resistance value of the SnO ₂ system film is about 15 Ω / □.
It can be reduced to 6Ω / □.

That is, it is shown that the striped metal electrode obtained in this example has a high light transmittance and a low sheet resistance and is optimal as an electrode of a photovoltaic cell.

Next, using the striped metal electrodes shown in Sample Nos. 1 to 4, dye-excited photovoltaic cells having a sectional structure shown in FIG. 2 were produced. In the figure, 1 is a silica glass substrate,
2 is a striped metal electrode formed on the silica glass substrate 1,
Reference numeral 3 is an electrolytic solution, 4 is a semiconductor ceramic to which a dye is adsorbed, 5 is a transparent electrode made of an ITO film, and 6 is a counter electrode made of platinum.

The dye-excited photovoltaic cells obtained as described above were all excellent in light-to-electricity conversion efficiency.

Although the striped metal electrode has been described in the above embodiments, the present invention is not limited to this. That is, the electrode shape is not particularly limited, and similar effects can be obtained for various shapes such as a lattice shape and a geometric pattern.

Further, in the above-mentioned embodiment, the case of the dye-excited type photocell has been described, but other various photocells such as p-type / n-type silicon semiconductor junction type can obtain the same effect.

Further, in the above embodiment, the case where the striped metal electrode is formed on the transparent electrode such as the ITO film as the incident light side electrode has been described, but for example, the p-type / n-type silicon semiconductor junction is used. In the case of a photovoltaic cell of the type, a striped metal electrode can be directly formed as an incident light side electrode on the semiconductor film without forming the transparent electrode.

[0034]

As is apparent from the above description, the incident-light-side metal electrode described above prevents light from being blocked by metal and has an incident-light-side electrode whose electrical resistance is reduced. A highly efficient photovoltaic cell can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a striped metal electrode used in the photovoltaic cell of the present invention.

FIG. 2 is a cross-sectional view showing an example of the photovoltaic cell of the present invention.

FIG. 3 is an optical path diagram showing a reflection direction of incident light.

[Explanation of symbols]

 1 Silica Glass Substrate 2 Striped Metal Electrode 3 Electrolyte 4 Semiconductor Ceramics 5 Transparent Electrode 6 Counter Electrode

Claims (5)

[Claims] 1. An incident light side electrode having a metal electrode whose cross-sectional shape has an acute angle edge on the incident light side and whose incident light irradiation surface is a mirror surface, a photoelectric conversion element body, and a counter electrode. And a photovoltaic cell. 2. The photovoltaic cell according to claim 1, wherein the shape of the metal electrode is a plurality of linear shapes. 3. The photovoltaic cell according to claim 2, wherein the plurality of linear metal electrodes have a stripe shape or a grid shape. 4. The photovoltaic cell according to claim 1 or 2, wherein the metal electrode is in electrical contact with the transparent electrode. 5. The photovoltaic cell according to claim 1, wherein the light irradiation surface of the metal electrode is embedded in a transparent substrate.