JPH06260670A - Light confinement structure for solar cells - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a light confinement structure for a solar cell capable of confining incident light in a substrate significantly efficiently. The above object is to provide an optical confinement structure for a solar cell, which is characterized by comprising a combination of at least two types of inverted pyramid layers provided on the surface of a substrate, and in particular,
Light incident on one slope of a large inverted pyramid, reflected by the back surface of the substrate, and then reaching the front surface of the substrate again is adjacent to each other.
This is achieved by providing a light confinement structure for a solar cell, characterized in that two surfaces of an inverted pyramid having a large pair are in contact with each other and are incident on a slope inclined at a right angle to the incident light incidence slope. be able to.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light confining structure for a solar cell, and more particularly to a light confining structure for a solar cell capable of confining incident light in a substrate significantly efficiently.

[0002]

2. Description of the Related Art In order to improve the photoelectric conversion efficiency of a solar cell, it is necessary to efficiently confine the light incident on the solar cell in the solar cell. For this purpose, it is necessary to first suppress the surface reflection and allow more light to enter the substrate, but in order to achieve this, a method of forming an inverted pyramid structure on the solar cell surface has been considered. There is. As such a structure, up to now, as shown in FIG. 2, an antireflection structure having a structure in which inverted pyramids of the same size made of a downwardly convex quadrangular pyramid are arranged is used. Examples of the disclosure of such a structure include Applied Physics Letters Vol. 55, No. 13, pp. 1363 to 1365 (1989) (Appl. Phys.
ett., Vol.55, No.13, 1989, pp.1363-1365).

[0003]

However, in the structure of the prior art described above, when the light incident on one slope of the inverted pyramid is reflected on the back surface of the substrate and reaches the front surface again, most of the light is emitted to the outside. Therefore, the light could not be efficiently confined in the substrate. The object of the present invention is to solve the problems that the above-described conventional art had,
An object of the present invention is to provide a light confinement structure for a solar cell capable of confining incident light in a substrate significantly efficiently.

[0004]

The above object is to provide an optical confinement structure for a solar cell, which is characterized by comprising a combination of at least two kinds of reverse pyramid layers provided on the surface of a substrate. The main part of the light that is incident on one slope of the pyramid, is reflected by the back surface of the substrate, and reaches the front surface of the substrate again, is the two surfaces of two adjacent pairs of large inverted pyramids that are in contact with each other, and are perpendicular to the incident light incident slope. This can be achieved by providing an optical confinement structure for a solar cell, which is configured to be incident on an inclined surface that is inclined in the direction.

[0005]

As shown in FIG. 2, the conventional optical confinement structure has a surface structure in which inverted pyramids of the same size, which are downwardly convex quadrangular pyramids, are arranged. When the light 3 enters the slope 1, it is reflected by the back surface of the substrate 8 and enters the slope 2. In this case, the angle at which the reflected light 7 is incident on the slope 2 is the same as the angle at which the incident light is incident on the slope 1 into the substrate, so this light is emitted to the outside of the substrate.

On the other hand, in the case of the light confinement structure of the present invention shown in FIG. 1, the light incident on the slope 1 travels along the line AA 'and is emitted to the slope 2. Since the slope 2 is inclined in the Y direction unlike the slope 1, the light 7 reflected on the back surface of the substrate enters the slope 2 at a large incident angle. When the light is incident on the boundary surface shallowly in this way, the reflectance of the light increases, so that most of the reflected light 7 is reflected by the slope 2 and travels inside the substrate again. Further, when light is incident from a substance having a large refractive index toward a substance having a small refractive index such as air, or when the incident angle is large, that is, when the light is incident shallowly, the light is totally reflected, so that the inclined surface 2 All incident light is confined within the substrate. As a result, most of the light 3 incident on the substrate 8 can be efficiently confined in the substrate 8.

These effects can also be obtained by combining a large inverse pyramid with a slightly smaller inverse pyramid as shown in FIG. 3 or a combination of a large inverse pyramid with an inverse pyramid half its size as shown in FIG. Obtainable.

[0008]

EXAMPLES The optical confinement structure for a solar cell of the present invention will be specifically described below with reference to examples. The configuration of one embodiment of the present invention will be described with reference to FIG. As described above, the light incident on the slope 1 is reflected by the back surface of the substrate, and the reflected light 7 enters the slope 2, so that the light is confined in the substrate 8. In order to do this efficiently, the substrate thickness 4, the inverse pyramid width 5 and the inverse pyramid opening angle 10 must have a specific relationship. In the case of this embodiment, the ratio of the width 5 of the large inverted pyramid to the width of the small inverted pyramid is set to 1: 6. For this reason, when the light that has entered the slope 1 at three cycles along the line AA 're-enters the slope 2, the light can be efficiently confined. For this,
The refractive index of the substrate 8 is 3.6, the substrate thickness 4 is w, and the opening angle of the inverted pyramid is

[0009]

[Equation 1]

When the width 5 of the large inverted pyramid is d,

[0011]

[Equation 2]

It is necessary to satisfy the relationship of In this embodiment, the substrate thickness 4 is 180 μm, and the width 5 of the inverted pyramid larger than the above equation is 101 μm. Further, when the repetition period is increased, the relationship between the substrate thickness 4 and the inverse pyramid width 5 can be obtained by increasing the value of n in the above equation.

[0013]

As described above, by using the optical confinement structure for a solar cell as the structure of the present invention, the problems of the prior art can be solved and incident light can be introduced into the substrate. It has been possible to provide a light confinement structure for a solar cell that can be confined significantly efficiently.

[Brief description of drawings]

FIG. 1 is a conceptual diagram illustrating the structure of an example of a solar cell light confinement structure of the present invention.

FIG. 2 is a conceptual diagram illustrating the structure of a conventional light confinement structure.

FIG. 3 is a conceptual diagram illustrating the structure of another example of the optical confinement structure of the present invention.

FIG. 4 is a conceptual diagram illustrating a structure of still another example of the optical confinement structure of the present invention.

FIG. 5 is a diagram for explaining the structure of an embodiment of the optical confinement structure of the present invention.

[Explanation of symbols]

1 ... Slope, 2 ... Slope, 3 ... Incident light, 4 ... Substrate thickness, 5 ...
Inverse pyramid width, 6 ... Inverse pyramid width, 7 ... Reflected light, 8 ... Substrate, 9 ... Incident angle, 10 ... Opening angle.

Claims (2)

[Claims] 1. A light confinement structure for a solar cell, comprising a combination of at least two kinds of large and small inverted pyramid layers provided on the surface of a substrate. 2. A main part of light which is incident on one slope of a large inverted pyramid, is reflected by the back surface of the substrate, and reaches the front surface of the substrate again, is the two surfaces of two adjacent pairs of large inverted pyramids which are in contact with each other. The light confinement structure for a solar cell according to claim 1, wherein the incident light is incident on a slope inclined at a right angle to the incident slope.