JP2000196113A - Solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the photoelectric conversion efficiency of a solar battery by providing a light scattering function on the rear surface side of a photovoltaic device so that light absorption by a transparent electrode on the light- receiving surface side of the photovoltaic device is reduced. SOLUTION: A solar battery is provided with a light-receiving surface-side substrate body 7, constituted by forming a photovoltaic device 13 composed of an amorphous semiconductor on a light-transmissive substrate 9 and a rear surface-side substrate body 8, which is formed separately from the substrate body 7 and provided on the rear surface side of the device 13, in a state where the body 8 faces opposite to the body 7. Therefore, a solar battery having a light scattering function on the rear surface side of the photovoltaic device 13 can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD OF THE INVENTION

The present invention relates to a solar cell having a photovoltaic device made of an amorphous semiconductor.

[0002]

2. Description of the Related Art Conventionally, in this type of solar cell, a transparent electrode (T
CO) has a texture structure having fine irregularities.

A conventional solar cell having a transparent electrode having this texture structure is constructed as shown in FIG. 5, and a light-receiving surface is provided on the light-receiving surface side (lower side in FIG. 5) of the light-transmitting substrate 1. The transparent electrode 2 on the side, the semiconductor layer of the amorphous semiconductor, and the transparent electrode 4 on the back side are sequentially laminated to form the amorphous semiconductor photovoltaic device 5.

The semiconductor layer 3 is specifically a semiconductor layer (a-Si layer) having an amorphous silicon pin structure.
And formed by a plasma CVD method.

On the other hand, the transparent electrodes 2 and 4 are Sn
The transparent electrode 2 is made of a transparent conductive film such as O ₂ , ZnO, or ITO. The transparent electrode 2 has a textured structure at the interface with the semiconductor layer 3 so as to exhibit a light confinement effect by a light scattering function.

On the back side of the transparent electrode 4, in order to increase light reflection on the back electrode of the photovoltaic device 5, for example, a reflective metal film 6 having a high reflectivity such as an Ag thin film is formed by a sputtering method.
Are integrally formed.

[0007]

In the case of the conventional solar cell shown in FIG. 5, the reflection on the back electrode side of the photovoltaic device 5 is increased to improve the photoelectric conversion efficiency. The reflective metal film 6 is formed integrally by a sputtering method or the like. At this time, the transparent electrode 4 is damaged by oxygen deficiency or the like.
Since the transmittance is reduced and the photoelectric conversion efficiency is rather reduced, the conditions for forming the reflective metal film 6 are limited.

Therefore, in this type of solar cell, conventionally, the transparent electrode 2 has a texture structure and the light receiving surface side of the photovoltaic device 5 has a light scattering function. Is 7000-8000 [deg.] Due to the texture structure, which is extremely thick compared to the thickness of the transparent electrode 4 of 500-1000 [deg.]. As a result, most of the long wavelength light of 800 nm or more is mainly transparent. There is a problem that the light is absorbed by the electrode 2 and the light cannot be used effectively, and the photoelectric conversion efficiency cannot be improved.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a solar cell having a light scattering function on the back side of a photovoltaic device without a decrease in transmittance in the prior art. Thus, the photoelectric conversion efficiency of this type of solar cell can be improved by reducing the absorption of light by the transparent electrode on the light receiving surface side.

It is another object of the present invention to provide a similar effect in the case of a series-connected integrated structure having a plurality of photovoltaic devices.

[0011]

In order to solve the above-mentioned problems, a solar cell according to the present invention comprises a light-transmitting substrate having an amorphous semiconductor photovoltaic device formed on a light-transmitting substrate. A substrate on the back side having a light scattering function, which is formed separately from the substrate and is provided on the back side of the photovoltaic device so as to face the substrate on the light receiving surface side.

Accordingly, a solar cell having a light scattering function on the back side of the photovoltaic device can be provided.

In this case, the transparent electrode on the light receiving surface side of the photovoltaic device does not need to have a texture structure as in the prior art.
The absorption of light by the transparent electrode can be reduced, and the reflective metal film is not formed integrally with the transparent electrode on the back side by sputtering or the like, but on the front side of the optical power device,
Since the structure is such that the substrate body on the back side of the separate body is provided to face, the transparent electrode on the front side of the photovoltaic device is not damaged by sputtering or the like.

The photovoltaic device is formed by laminating a transparent electrode on the light receiving surface side, a semiconductor layer, and a transparent electrode on the rear surface side on the rear surface of a light transmitting substrate, and the substrate on the rear surface side is formed on the light receiving surface side. It is practical and preferable that a reflective metal film having a texture structure is formed on the surface facing the substrate body.

Further, when the transparent electrode on the light receiving surface side and the transparent electrode on the back surface side are made into a flat thin film, in particular, the transparent electrode film on the light receiving surface side can be made extremely thin as compared with the conventional texture structure. Light absorption by the film is reduced,
The photoelectric conversion efficiency is significantly improved.

Next, a plurality of amorphous semiconductor photovoltaic devices may be formed on the translucent substrate of the substrate body on the light receiving surface side, and may be formed in an integrated type structure connected in series. The present invention can be similarly applied to a solar cell having an integrated structure in which a plurality of photovoltaic devices are connected in series.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.
This will be described with reference to FIG. (One Embodiment) First, one embodiment of the present invention will be described with reference to FIGS. This type of solar cell is shown in FIG.
As shown in FIG. 2, a substrate body 7 on the light receiving surface side (the lower side in the figure) and a substrate body 8 on the back side (the upper side in the figure) are provided, and both the substrate bodies 7 and 8 are shown in FIGS. ) Are formed separately.

FIG. 2A is a perspective view of the substrate 8 as viewed from the back side, and FIG. 2B is a perspective view of the substrate 7 as viewed from the back side.

The substrate 7 is provided on the back surface of a light-transmitting light-receiving surface substrate 9 as a supporting substrate made of a glass substrate, with the transparent electrode 10 on the light-receiving surface side, the semiconductor layer 11, and the transparent electrode 1 on the back side.
2 are stacked to form a photovoltaic device 13.

Incidentally, the transparent electrodes 10 and 12 are made of GZO (G
A thin film (transparent conductive film) of ZnO such as ZnO doped with a) can be used. Since the transparent electrode 10 does not need to be formed in a textured structure unlike the conventional transparent electrode 2 of FIG. 5, it is made of, for example, a flat thin film (transparent conductive film) of 5000 ° or less. It is made of a 500-1000 ° flat thin film (transparent conductive film) similar to the transparent electrode 4.

On the back surface of the transparent electrode 12, Ag grid electrodes 14 are formed at appropriate lattice intervals to reduce current loss.

The semiconductor layer 11 is a pin-structured a-Si layer formed by a plasma CVD method, similarly to the conventional semiconductor layer 3 of FIG.

On the other hand, the substrate body 8 is formed by laminating a transparent electrode 16 and a reflective metal film 17 of Ag on a surface of a translucent rear substrate 15 as a support substrate made of a glass substrate by a sputtering apparatus.

At this time, the surface of the transparent electrode 16 is processed into fine irregularities by controlling the forming conditions or by mechanical polishing or etching, and the thin film of the reflective metal film 17 formed on the surface is transparent. A texture structure is formed according to the surface shape of the electrode 16.

Therefore, a reflective metal film 17 having a texture structure is formed on the surface of the substrate 8 facing the substrate 7, and this reflective metal film 17 has a light reflecting function and a light scattering function.

Then, the separately formed substrate bodies 7, 8
Are provided to face each other such that the substrate body 8 is located on the back surface side of the photovoltaic device 13, thereby completing the solar cell module.

At this time, the substrate 8 is provided so that the reflective metal film 17 contacts (joins) the grid electrode 14 on the back surface of the transparent electrode 12 in order to use the reflective metal film 17 also as a collecting electrode.

More specifically, for example, the substrates 7 and 8 are supported on a module frame, or the surface periphery of the transparent electrode 12 and the surface periphery of the reflective metal film 17 are soldered. Then, the substrates 7 and 8 are joined so that the reflective metal film 17 is in contact with the grid electrode 14.

The gap between the substrates 7 and 8, that is, the gap between the transparent electrode 12 and the reflective metal film 17 is usually provided with an EV.
A (Ethylene Vinyl Acetate), PVB (Poly Vinyl B)
Although a translucent resin such as utylol) is filled, the space may be left without filling with a resin in order to reduce light loss during that time.

In the case of the solar cell of the present embodiment formed as described above, the reflective metal film 1 on the back side of the photovoltaic device 13
7, the light scattering function is formed, so that the transparent electrode 10 on the light receiving surface side of the photovoltaic device 13 is not formed in a texture structure, but is formed in a flat thin film, and the transparent electrode film 10 absorbs light. And, in particular, the photoelectric conversion efficiency for long wavelength light is improved.

The reflection metal film 17 is formed on the photovoltaic device 13.
5 is mechanically (physically) bonded to the transparent electrode film 12 and is not formed integrally with the transparent electrode film 4 by a sputtering device unlike the reflective metal film 6 of the conventional battery shown in FIG. There is no limitation on the formation conditions, and even if the reflective metal film 17 is formed in a textured structure, there is no loss of oxygen in the transparent electrode film 12 and the transmittance does not decrease. Therefore, the photoelectric conversion efficiency of the solar cell is remarkably improved as compared with the related art.

In the above-described embodiment, the substrates 7 and 8 are joined via the grid electrode 14 in order to extract electricity from the reflective metal film 17 by using the reflective metal film 17 as a collecting electrode. When the collector electrode is not required, the grid electrode 14 may be omitted, and electricity may be extracted from the transparent electrode 12. In this case, the reflective metal film 17 is provided so as to have a gap between the reflective metal film 17 and the transparent electrode 12. It may be.

Next, another embodiment of the present invention will be described with reference to FIGS. In these drawings, those with a dash (') attached to the reference numerals indicate the same or corresponding parts as those of the same reference numerals in FIGS. 1 and 2, and FIG. 3 is an explanatory view of the configuration of the solar cell. 4 (a) and 4 (b) show the substrate body 8 'on the back side thereof.
It is the perspective view which looked at the board | substrate 7 'of the light-receiving surface side from the back surface side, respectively.

In this embodiment, the substrate 7 '
The transparent electrode 10 'on the light receiving surface side, the semiconductor layer 11', and the transparent electrode 12 'on the rear surface side
Are formed to form a series-connected integrated structure.

Specifically, in the case of forming by a laser patterning method, first, a planar transparent electrode film of ZnO such as ZGO having plasma resistance is formed on a substrate 9 ′ by a sputtering device, and this is patterned by laser patterning. The film is processed to form each transparent electrode 10 '.

Next, plasma CVD was performed on those surfaces.
An a-Si layer having a pin structure is deposited by a method, and separated into respective semiconductor layers 11 'by laser light.

Further, Zn is deposited on the surface of each semiconductor layer 11 '.
Forming a flat transparent electrode film of O, processing this film and each separated a-Si layer by laser patterning to form each semiconductor layer 11 'and each transparent electrode 12' on the back side thereof, Each integrated photovoltaic device 13 'is formed.

The photovoltaic devices 13 'may be formed by using a metal mask method or a photolithography method instead of the laser patterning method.

Also, in the case of this integrated structure, each photovoltaic device 13 'has a small light receiving area and a small individual loss.
Moreover, since it is necessary to prevent short-circuiting of each transparent electrode 12, an electrode corresponding to the grid electrode 14 of the above-described one form is not provided.

On the other hand, as for the substrate body 8 ', as in the case of the substrate body 8 of one embodiment, a reflective metal film 17' having a texture structure is provided on the front surface side of the translucent rear substrate 13 'via the transparent electrode 16'.
To form

Then, the substrate body 8 is opposed to the surface side of each photovoltaic voltage 13 'of the substrate body 7' with a gap provided therebetween, thereby forming a solar cell having an integrated structure shown in FIG.

The gap between the substrates 7 'and 8' is usually filled with a translucent resin such as EVA or PVB, but may be left as a space.

In this case, the reflective metal film 1 is also used.
Since the light scattering function is formed by 7 ', the transparent electrode 10' on the light receiving surface side of each photovoltaic voltage 13 'is not formed in a texture structure, and the same effect as in the first embodiment can be obtained.

By the way, the present invention is similarly applied to the case where the photovoltaic devices of the second stage, the third stage,... Of course.

The solar cell of the first embodiment and the solar cell of the other embodiment were used as the solar cells of Examples 1 and 2, respectively, and the module output of the conventional cell of FIG. , 13 ′, the module output of the conventional battery was 11W, but the module output of the solar cells of Examples 1 and 2 was 11.2W, 11.5W
It was confirmed that each of them increased from the conventional battery.

Then, the transparent electrodes 10, 10 ', 12, 1
Film thickness of 2 ′ reflective metal film 17, 17 ′, etc., photovoltaic device 1
The semiconductors 3 and 13 'are not limited to those in the above-mentioned embodiments, and the present invention can be applied to various solar cells made of an amorphous semiconductor.

[0047]

The present invention has the following effects. First, the substrate 7 on the light receiving surface side in which the amorphous semiconductor photovoltaic devices 13 and 13 'are formed on the translucent substrates 9 and 9',
7 'and a back surface having a light scattering function, which is formed separately from the substrate bodies 7 and 7' and provided on the back side of the photovoltaic devices 13 and 13 'so as to face the substrate bodies 7 and 7'. Side substrate body 8,
8 ′, it is possible to provide a solar cell having a light scattering function on the back side of the photovoltaic devices 13 and 13 ′.

In this case, it is not necessary to provide the transparent electrodes 10, 10 'on the light receiving surface side of the photovoltaic devices 13, 13' with a light scattering function. Since the separate substrates 8 and 8 'on the back side are provided to face each other, the transparent electrodes 12 and 12' on the front side of the photovoltaic devices 13 and 13 'may be damaged by sputtering or the like. In addition, it is possible to prevent a decrease in transmittance due to the addition of a light scattering function, and to improve photoelectric conversion efficiency.

The photovoltaic devices 13 and 13 ′ are provided on the back surfaces of the transparent substrates 9 and 9 ′ with the transparent electrodes 10 and 1 on the light receiving surface side.
0 ′, semiconductor layers 11, 11 ′, transparent electrode 12 on the back side,
It is preferable that the reflective metal films 17 and 17 ′ having a texture structure are formed on the surfaces of the substrate members 8 and 8 ′ on the back surface facing the substrate members 7 and 7 ′ on the light receiving surface side. It is practical and preferable.

At this time, the transparent electrodes 10, 10 'on the light receiving surface side
If the transparent electrodes 12 and 12 'on the back side are made into a flat thin film, the transparent electrodes 10 and 10' on the light receiving side are particularly thinner than those of the conventional texture structure. Light absorption is reduced, and the photoelectric conversion efficiency can be significantly improved.

Next, a plurality of amorphous semiconductor photovoltaic devices 13 'are formed on the light-transmitting substrate 9' of the substrate body 7 'on the light-receiving surface side, and formed in a series-connected integrated structure. In this case, the present invention can be similarly applied to a solar cell having an integrated structure in which a plurality of photovoltaic devices are connected in series.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a solar cell according to one embodiment of the present invention.

2A is a perspective view of a substrate body on the back surface side in FIG. 1, and FIG. 2B is a perspective view of the substrate body on the light receiving surface side in FIG.

FIG. 3 is a configuration diagram of a solar cell according to another embodiment of the present invention.

4A is a perspective view of the substrate body on the back surface side in FIG. 3, and FIG. 4B is a perspective view of the substrate body on the light receiving surface side in FIG.

FIG. 5 is a configuration diagram of a conventional battery.

[Explanation of symbols]

 7, 7 'Substrate body on light receiving surface side 8, 8' Substrate body on back surface 9, 9 'Transparent substrate on light receiving surface side 10, 10' Transparent electrode on light receiving surface side 11, 11 'Semiconductor layer 12, 12 'Transparent electrode on back side 13, 13' Photovoltaic device 15, 15 'Transparent substrate on back side 17, 17' Reflective metal film

Claims (4)

[Claims] 1. A light-receiving-side substrate body in which an amorphous semiconductor photovoltaic device is formed on a light-transmitting substrate; and the photovoltaic device formed separately from the light-receiving surface side substrate body. And a backside substrate having a light-scattering function, provided on the backside of the device and facing the substrate on the light-receiving side. 2. A photovoltaic device is formed by laminating a transparent electrode on the light receiving surface side, a semiconductor layer, and a transparent electrode on the rear surface side on the back surface of a translucent substrate. The solar cell according to claim 1, wherein a reflective metal film having a texture structure is formed on a surface facing the substrate body. 3. The solar cell according to claim 2, wherein the transparent electrode on the light receiving surface side and the transparent electrode on the back side are flat thin films. 4. A plurality of amorphous semiconductor photovoltaic devices are formed on a light-transmitting substrate of the substrate on the light-receiving surface side, and are formed in an integrated type structure connected in series. The solar cell according to claim 1, 2 or 3.