JP3222945B2 - Method for manufacturing photovoltaic device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a process for producing a photovoltaic equipment for converting energy according to the incident light into electrical energy.

[0002]

2. Description of the Related Art In a photovoltaic device, there is a problem how to absorb most of incident light. FIG. 5 is an element structure diagram of a conventional photovoltaic device. In the figure, (61) is a substrate made of glass or ceramic or the like serving as a support of the photovoltaic device, (62) is a back electrode made of a metal film formed on the substrate (61), and (63) is a back surface. A photoelectric conversion layer having an amorphous silicon film formed on the electrode (62) as a base material, and a pin junction parallel to the film surface is formed on the photoelectric conversion layer. (64) is a translucent electrode formed on the photoelectric conversion layer (63) and functioning as a light incident electrode. In this photovoltaic device, light (65) incident from the film forming surface side is photoelectrically converted and extracted as a photocarrier composed of electrons and holes.

[0003] In this conventional photovoltaic device, the incident light is effectively used by forming a concavo-convex shape as shown on the surface of the substrate (61). That is, the translucent electrode (64)
The light (65) incident through is traveling in the photoelectric conversion layer (63),
Although this light is sequentially absorbed, usually this light (65) is not sufficiently absorbed by this photoelectric conversion layer (63) only once, and a part of the light (65) passes through the photoelectric conversion layer (64) and the back electrode (62). To reach.

In such a case, if the above-mentioned uneven shape is formed on the surface of the substrate (61), the uneven shape reflects the uneven state to the surface of the back electrode (62) attached to the surface of the substrate. As a result, the irregularities formed on the surface of the back electrode (62) effectively scatter and reflect the light (65), and the light travels again into the photoelectric conversion layer (63). In particular,
Most of the light scattered and reflected travels obliquely in the film of the photoelectric conversion layer (63), so that the distance traveled in the film of the photoelectric conversion layer (63) is longer than that of the film of the photoelectric conversion layer (63). It is substantially longer than the thickness, allowing more light absorption.

[0005] Therefore, by utilizing such a concavo-convex shape, the photoelectric conversion efficiency of the photovoltaic device can be improved, and in particular, the short-circuit current can be increased due to an increase in the absorption of long-wavelength light. Such a photovoltaic device is described in detail in, for example, JP-A-62-76569.

[0006]

However, manufacturing a substrate (61) having such a concavo-convex shape generally involves some difficulties.

In other words, in order to effectively reflect light in this uneven shape, it is necessary to make the degree of the uneven shape minute, while the formed convex portion of the uneven shape is too sharp. Not be. That is, if the projection becomes too sharp, the back electrode (6
2) and the photoelectric conversion layer (63) are extremely thin films, which makes it difficult to form them with a uniform thickness, and furthermore, the formed film has large residual stress in the film. This is because the characteristics as a photovoltaic device cannot be sufficiently obtained in the first place.

[0008] Conventionally, as a method of manufacturing such a concavo-convex shape,
It is often performed by mechanical processing on the substrate surface or chemical etching with a chemical or the like, but still has some problems.

In particular, a photovoltaic device must be manufactured as a device having a large area in order to absorb more light, that is, to obtain a larger output.
According to the above-mentioned conventional method, it was not possible to form a uniform and fine uneven shape over a large area.

[0010]

A feature of the method of manufacturing a photovoltaic device according to the present invention is that an amorphous silicon film containing hydrogen is formed on a substrate, and the amorphous silicon film is irradiated with an energy beam. An object is to sequentially form a back electrode, a photoelectric conversion layer, and a translucent electrode on the surface of the amorphous silicon film.

[0011]

[0012]

[0013]

[0014]

According to the production process of the working of the present invention a photovoltaic device, by irradiating an energy beam to the amorphous silicon film containing hydrogen, hydrogen is ejected from the membrane contained in the amorphous silicon film The thickness of the amorphous silicon film is locally increased or decreased due to the pressure at the time of the ejection. Thus, the surface of the substrate on which the amorphous silicon film is formed can be provided with a fine uneven shape suitable for light reflection.

[0015]

[0016]

[0017]

DETAILED DESCRIPTION FIG. 1, the important reference photovoltaic device of the present invention
It is a device structure figure of a reference example . In the figure, (1) is a substrate made of ceramics or the like, (2) is an insulating film containing insulating ceramic particles (2b) in an insulating material (2a), and (3) is formed on the insulating film (2). A back electrode made of silver or the like, (4) is a photoelectric conversion layer of the photovoltaic device. In this example, an amorphous silicon film is used. The structure thereof is n-type amorphous silicon (4n), It has a three-layer structure of crystalline silicon (4i) and p-type amorphous silicon (4p). (5) is a light-transmitting electrode made of indium tin oxide, tin oxide, or the like on the light incident side.

Materials other than the insulating film (2) containing the ceramic particles (2b) are conventionally known materials, and Table 1 shows the photoelectric conversion layer (4).
The typical formation conditions of are shown.

[0019]

[Table 1]

The insulating film (2) which is a feature of this embodiment is formed as follows. Particle size of about 5 as ceramic particles (2b)
After a silica (SiO ₂ ) solution containing alumina particles of μm is applied to the surface of the substrate (1), it is cured at a temperature of about 500 ° C. The thickness of the cured insulating film (2) is 0.5 μm to 500 μm.
μm is a practical range. Also, ceramic grains (2b)
The typical range of the particle size is 0.1 μm to 10 μm.

As a result, the silica becomes
In addition to filling the interstices so as to enclose (2b), the surface of the cured insulating film (2) can be made uneven by the ceramic grains (2b).

[0022] The thickness of the insulating film in the present embodiment has been designed to be approximately 20μm after cure, the film thickness according to the experiments of the present inventors used in the range of 0.5μm~500μm Make sure it is possible. Further, in the case of the present reference example, the degree of irregularities generated on the surface of the insulating film was about 2 μm.

Table 2 is a table showing the characteristic values of the photovoltaic device of the reference example, and the table also shows the values of the conventional photovoltaic device for comparison. This conventional photovoltaic device has a completely similar structure except that an insulating film made of silica alone is used instead of the insulating film containing ceramic particles, which is a feature of this reference example .

[0024]

[Table 2]

As is clear from the table, the photovoltaic device of this reference example has a short-circuit current of 20% as compared with the conventional photovoltaic device.
It is increasing. This is presumably because in the photovoltaic device of the present reference example , as a result of the effective reflection of light by the ceramic grains, light absorption was effectively performed and the short-circuit current could be increased.

The insulating film in the present embodiment is not only formed by a coating fabric method described above, it may be an insulating film formed by a so-called plasma spraying. In the plasma spraying method, a powdery material spouted into the air is decomposed by the energy of plasma, and this is used as a material for forming a film. This plasma spraying method is described in detail in, for example, JP-A-4-45521.

In this plasma spraying method, an insulating film can be formed in the same manner as in the reference example by using raw materials and gases as shown in Table 3.

[0028]

[Table 3]

As the ceramic particles, TiN, TiC or the like can be used in addition to the above-mentioned alumina (Al ₂ O ₃ ).

Next, a description will be given of actual施例of the present invention. In this embodiment, the method of forming the unevenness on the substrate surface is performed by irradiating the hydrogen-containing amorphous silicon film with an energy beam such as a laser beam. Cause the eruption phenomenon,
The surface of the amorphous silicon film is made uneven.

FIG. 2 shows the relationship between the content of hydrogen, which is the base of the ejection phenomenon, in the film and the degree of unevenness due to the irradiation of the film with the energy beam. The horizontal axis shows the energy density of the ArF excimer laser used as the energy beam, and the vertical axis shows the degree of the unevenness. In the figure, the hydrogen content in the film is (a) 18%, (b) 13) and (c) 8%. The control of the hydrogen content was performed by adjusting the film formation temperature described later.

As can be seen from the figure, as the hydrogen content and the energy density in the film both increase, the degree of the irregularities rapidly increases. In particular, when the hydrogen content is 18%, the energy density is 200 mJ / cm ^2.
Above, it has increased sharply.

FIG. 3 is a characteristic diagram showing the relationship between the formation temperature and the hydrogen content in the film. The figure shows that the temperature gradually decreases as the formation temperature increases from 200 ° C. to 500 ° C. Therefore, it is understood that the control of the hydrogen content in the film by the formation temperature is extremely easy and has good reproducibility.

Next, the characteristics of the photovoltaic device provided with the uneven shape due to the hydrogen ejection phenomenon will be described. FIG.
Is a comparison of the characteristics of the photovoltaic device of the second embodiment with the characteristics of a conventional photovoltaic device. FIG. 4 shows the respective photosensitivity characteristics. The specific element structure of the photovoltaic device (a) of the present embodiment is different from the insulating film (2) of the photovoltaic device of the reference example described above in that the unevenness is formed by the ejection of hydrogen due to the irradiation of the energy beam. This is exactly the same except that an amorphous silicon film is used.

The amorphous silicon film used in the embodiment has a formation temperature of about 250 ° C. and a thickness of about 3000
膜 film. Further, as the conventional photovoltaic device (b), the same device as the conventional photovoltaic device in Table 2 was evaluated.

According to the figure, the photovoltaic device of the present invention (a)
In the above, the light sensitivity in the long wavelength region of 600 nm to 800 nm is greatly improved, and the incident light, especially the long wavelength light, can be sufficiently utilized, so that the uneven shape by the hydrogen ejection can be formed well. I understand.

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

Although an amorphous semiconductor is mainly used as the semiconductor material in the above-described embodiment, the effect of the present invention is not limited to such a semiconductor material. For example, a combination of a polycrystalline semiconductor and a single-crystal semiconductor may be used. Such a photoelectric conversion layer can be formed in exactly the same manner as long as an amorphous silicon material containing hydrogen is used. Further, the photoelectric conversion layer is not limited to one formed by the plasma CVD method or the like used in the embodiment, and may be one formed by, for example, a solid phase growth method.

[0046]

According to the photovoltaic device manufacturing method of the present invention ,
Energy beam on amorphous silicon film containing hydrogen.
Irradiation of the amorphous silicon film
Hydrogen is ejected from the membrane, and due to the pressure at the time of the ejection,
Leverage amorphous silicon film thickness can be locally large or small
It will be. Thereby, this amorphous silicon film is formed.
Fine uneven surface suitable for light reflection
Can be applied.

[0047]

[0048]

[Brief description of the drawings]

1 is a device structure cross-sectional view of a reference example of important reference photovoltaic device of the present invention.

FIG. 2 is a characteristic diagram showing the energy density of energy beam irradiation on amorphous silicon containing hydrogen and the degree of unevenness.

FIG. 3 is a characteristic diagram showing a relationship between amorphous silicon formation conditions and hydrogen content in a film.

FIG. 4 is a light sensitivity characteristic diagram of the photovoltaic device of the present invention and a conventional photovoltaic device.

FIG. 5 is a sectional view of an element structure of a conventional photovoltaic device.

[Explanation of symbols]

(1) ... substrate (2) ... insulating film (2b) ... insulating ceramic particles (3) ... back electrode (4) ... photoelectric conversion layer (5) ... translucent electrode

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-196364 (JP, A) JP-A-2-180081 (JP, A) JP-A-3-159179 (JP, A) JP-A-4-199 299575 (JP, A) JP-A-3-212977 (JP, A) JP-A-57-71188 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 31/04-31 / 078

Claims (1)

(57) [Claims] Amorphous silicon containing hydrogen on a substrate
Forming a film, and irradiating the amorphous silicon film with an energy beam.
Irradiating , forming a back electrode on the amorphous silicon film, and forming a photoelectric conversion layer made of a semiconductor on the back electrode.
A method for manufacturing a photovoltaic device, comprising: a step of forming a translucent electrode on the photoelectric conversion layer .