JPH0795601B2 - Photovoltaic device manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a photovoltaic device in which a light-receiving surface electrode having an uneven surface is arranged on the light incident side.

(B) Conventional technology A photovoltaic device using a semiconductor film having a semiconductor junction as a photoactive layer is already known, and its basic configuration is a light-receiving surface electrode, a semiconductor film, and a back electrode on an insulating surface of a transparent substrate. Are laminated in this order. The photovoltaic device disclosed in U.S. Pat.No. 4,281,208 has a plurality of unit photoelectric conversion elements, which are a laminate of a light-receiving surface electrode, a semiconductor film, and a back electrode, formed on a common substrate, and the photoelectric conversion elements are electrically connected. By providing a serial connection in series, a structure for obtaining a practically high output voltage is provided.

On the other hand, in order to improve the photoelectric conversion efficiency of such a photovoltaic device, Japanese Examined Patent Publication No. 62-7716 and the 44th Academic Meeting of the Applied Physics Society (September 25-28, 1983) Proceedings 25P-L -2 third
As disclosed on page 51, etc., an attempt is made to texture the surface of the light-transmitting light-receiving surface electrode on the light-incident side by providing unevenness to lengthen the optical path length of the incident light and confine the incident light in the semiconductor film. There is.

FIG. 8 is an enlarged view of a series connection portion when a light receiving surface electrode having a concavo-convex surface is applied as the light receiving surface electrode of the series connection type photovoltaic device disclosed in the above-mentioned US patent. That is, in FIG. 8, (1) is an insulative and translucent substrate such as glass or transparent ceramics, and (2a) and (2b) are SnO ₂ , ITO, etc., which are separately arranged on the surface of the substrate (1). Is a light-receiving surface electrode made of a transparent conductive oxide (TCO) and has an uneven surface (2tex) on its exposed surface side. (3a) and (3b) are amorphous semiconductors including amorphous silicon, amorphous silicon carbide, amorphous silicon germanium and their microcrystals deposited on the light-receiving surface electrodes (2a) and (2b). And (4a) and (4b) are the semiconductor films (3a) and (3b).
b) A back electrode including ohmic metal superposed and deposited on the light-receiving surface electrodes (2a) (2b), semiconductor films (3a) (3).
The unit photoelectric conversion elements (5a) and (5b) are formed from the respective laminated bodies of b) and the back electrodes (4a) and (4b), and the photoelectric conversion elements (5a) and (5b) are the photoelectric conversion elements (5a) on the left side. Photoelectric conversion element (5b) with the extension (4a ') of the back electrode (4a) of the
Are electrically connected in series by extending to the exposed portion (2b ') of the light receiving surface electrode (2b).

However, in the photovoltaic device having such a structure, although the light receiving surface electrodes (2a) (2b) have the uneven surface (2tex), the photoelectric conversion efficiency can be increased, but the photoelectric conversion elements (5a ) (5b) divided portions of the semiconductor films (3a) and (3b), that is, electrically coupled portions between the extended portion (4a ') of the back electrode (4a) and the exposed portion (2b') of the light-receiving surface electrode (2b). At
As disclosed in JP-A-57-12568, when a laser scribing method that divides each film by irradiating a laser beam, which is excellent in large area fine processing and does not require a wet process, is solved as follows. There are problems to do. That is, as shown in FIG. 9, the light-receiving surface electrodes (2a) (2b) are already formed on the insulating surface of the substrate (1) by patterning, and the light-receiving surface electrodes (2a) (2b) are included in the surface of the substrate (1). After the semiconductor film (3) is continuously deposited on the substrate, a laser beam is irradiated to divide the semiconductor film (3) into photoelectric conversion elements (5a) and (5b). Although the semiconductor film portion received is basically burned and removed, the uneven surface (2tex) of the light-receiving surface electrode (2b) that is the underlying layer
As a result, the laser beam is not scattered and is not focused, so that a part of the semiconductor film (3 ′) to be removed may remain at the bottom of the uneven surface (2tex). The residual semiconductor film (3) ″ on the uneven surface (2tex) finally forms the series connection of the photoelectric conversion elements (5a) (5b) and the extension (4a ′) of the back electrode (4a) and the light-receiving surface electrode. Since it is located at the interface of the exposed portion (2b ') of (2b), the resistance value in the series connection portion increases.

(C) Problems to be Solved by the Invention In the present invention, when the evaluation surface of the light-receiving surface electrode is textured in order to improve the photoelectric conversion efficiency as described above, a part of the semiconductor film remains on the uneven surface in the series connection part. However, it is intended to solve the problem that the resistance value in the series connection portion increases.

(D) Means for Solving the Problems In the present invention, a light-receiving surface electrode having at least an uneven surface is arranged on an insulating surface of a transparent substrate, and a semiconductor film and a back electrode are laminated on the uneven surface of the light-receiving surface electrode. To form a plurality of unit photoelectric conversion elements, and to connect the photoelectric conversion elements in series to one another, the light receiving surface electrode of the adjacent photoelectric conversion element is electrically connected to the electrical extension of the other back electrode. In a method of manufacturing a power device, in order to solve the above problems, prior to dividing the semiconductor film deposited over a plurality of photoelectric conversion element regions by irradiation of an energy beam for each photoelectric conversion element, A flattening process is performed in advance on the series connection portion of the uneven surface of the one light-receiving surface electrode to which the electrical extension portion of the other back electrode is electrically connected in series.

(E) Action As described above, the series connection of the uneven surface of the one light-receiving surface electrode, to which the electrical extension of the other back electrode is electrically connected in series, is preliminarily flattened. Yotsutte
Even if the semiconductor film is irradiated with an energy beam for each photoelectric conversion element, the scattering of the energy beam is suppressed and the beam can be focused.

(F) Example FIG. 1 to FIG. 7 show the manufacturing method of the present invention step by step.

In the process shown in Fig. 1, the thickness is 1 mm to 3 mm and the area is 10 cm x 10 cm to 40
Average film thickness on the entire surface of the transparent substrate (1) with a size of cm x 40 cm
2000Å ~ 6000Å, uneven peak toe peak about 0.3 μm ~
A light-receiving surface electrode (2) made of TCO provided with an uneven surface (2tex) of 0.5 μm is deposited. The uneven surface (2tex) of the light-receiving surface electrode (2) has a large particle size as disclosed in Japanese Patent Publication No. 62-7716, and therefore, the uneven surface (2t) is directly used.
Ex.) forming a light receiving surface electrode (2) having
As described in Japanese Patent No. 288473, it may be processed into an uneven surface (2tex) by utilizing the anisotropy of the etching rate after film formation.

In the process shown in FIG. 2, the adjacent gaps (2 ') of the light-receiving surface electrodes (2) are removed by irradiation with the laser beam (LB), and the individual light-receiving surface electrodes (2a) (2b) ... Are separately formed. To be done. The wavelength of the laser device used is such that it is hardly absorbed by the substrate (1), and when the substrate (1) is made of glass, a pulse output type with a wavelength of 0.35 μm to 2.5 μm is preferable. Such a preferred embodiment has a wavelength of about 1.06.
[mu] m, about 20 J / cm ^3, Q switchable Nd pulse repetition frequency 3 KHz: a YAG laser is used, the width of the adjacent intervals portion (2 ') is set to about 50 .mu.m to 100 .mu.m.

In the step of FIG. 3, the uneven surface of the light-receiving surface electrode (2b) at the semiconductor film division planned site is biased toward one end of the adjacent spacing part (2 ′) including a serial connection part for serial connection ( 2tex)
On the other hand, a flattening process is performed to form a flat surface (2flat). One example of such flattening processing is to reduce and use the output of the laser device used in the separation step (step of FIG. 2) for the light-receiving surface electrode (2). For example, the processing limit power density of the light-receiving surface electrode (2) of the TCO is about 9 J / cm ³ , and the unevenness surface (2tex) of the planned back electrode division part has a laser beam (power beam density slightly lower than the processing limit power density By irradiating LBlo), it is melted and re-solidified to flatten the uneven surface (2tex). Therefore, if the flattening process of the uneven surface (2tex) is performed by irradiating the laser beam (LBlo), the laser output is changed to separate the light-receiving surface electrode (2) shown in FIG. Processing can be carried out simultaneously or successively.

As another example of the flattening process, the flat surface (2flat) may be partially formed by mechanically cutting and polishing the uneven surface (2tex).

In the step shown in FIG. 4, the thickness of the light receiving surface electrodes (2a) and (2b) including the uneven surface (2tex) and the flat surface (2flat) is effectively contributed to photoelectric conversion over the entire surface of the substrate (1). 4000Å ~ 1 μm
Plasma using a silicon compound gas as a main raw material gas for which a semiconductor film (3) such as amorphous silicon (a-Si) is known to some extent
It is formed by a CVD method or an optical CVD method. Such a semiconductor film (3)
Contains a pin junction parallel to the film surface, and more specifically, first, p-type amorphous silicon carbide is deposited, and then i-type and n-type amorphous silicon are sequentially laminated. Be applied.

In the step of FIG. 5, in order to separate and form the continuously formed semiconductor film (3) into individual semiconductor films (3a) and (3b), the flat surface (2flat) of the light-receiving surface electrode (2b) which is a base layer is formed. The semiconductor film adjacent gap portion (3 ') covering the above is removed by irradiation with a laser beam from the main surface side of the substrate (1) as indicated by the arrow. The laser device used has a wavelength of 0.35 μm to 0.78 μm.
It is a 0.53 μm pulse output type laser with irradiation conditions of pulse width 90 nsec, pulse repetition frequency 3 KHz and energy density 0.
At 5 J / cm ³ , the width of the adjacent space (3 ') to be removed is about 300.
The flat surface (2flat) is exposed to the extent that the light-receiving surface electrode (2b) is planned to be connected in series, and is set to about μm to 500 μm.

In the process shown in FIG. 6, a flat surface (2flat) including a portion to be connected in series with the light-receiving surface electrode (2b) and an individual semiconductor film (3
A back electrode (4) is continuously deposited on a) (3b). Such a back electrode (4) has a film thickness of, for example, 1000Å to 1μ.
A single layer structure of highly reflective metal such as aluminum or silver having a thickness of about m, a two-layer structure in which a highly moisture resistant metal such as titanium or titanium silver alloy is superposed on the highly reflective metal, the highly reflective metal and the semiconductor film ( 3a) From the two-layer structure in which TCO such as ITO and SnO ₂ is arranged at the interface with (3b), and the three-layer structure in which a high humidity resistant metal is laminated on the two-layer structure of TCO / highly reflective metal Become.

In the final step of FIG. 7, the adjacent space (4 ′) of the back electrode (4) deposited on the flat surface (2flat) of the light-receiving surface electrode (2b) is irradiated with the laser beam (LB). The individual back electrodes (4a) (4b) are formed by removing. The laser device used is a pulse output type laser having a wavelength of 1.06 μm, and the width of the adjacent interval portion (4 ′) is, for example, about 20 μm.
It is set to -100 μm. As a result, the light-receiving surface electrode (2a)
(2b), semiconductor films (3a) (3b) and back electrodes (4a) (4
A unit photoelectric conversion element (5a) (5b) is formed from each laminated body of b), and the photoelectric conversion element (5a) (5b) is an extension of the back electrode (4a) of the photoelectric conversion element (5a) on the left side. (4a ') extends directly to the exposed portion (2b') of the light-receiving surface electrode (2b) of the photoelectric conversion element (5b) adjacent on the right side, so that it is electrically connected in series.

What should be noted in the above series of steps is the step of FIG. 5 in which the semiconductor film (3) deposited over a plurality of photoelectric conversion element regions is divided into photoelectric conversion elements (5a) and (5b). Prior to this, the extension (4a ') of the back electrode (4a) of the photoelectric conversion element (5a) on the left side is electrically connected in series. Planarized in the step of FIG. 3 in advance in the divided portions of the semiconductor films (3a) and (3b) including the series connection part of the uneven surface (2tex) of the light receiving surface electrode (2b) of the photoelectric conversion element (5b) on the right side. This is because the flat surface (2flat) was formed by processing. Therefore, when the semiconductor film (3) is individually divided into (3a) and (3b) by the irradiation of the laser beam (LB) in the step of FIG. 5, the exposure of the light-receiving surface electrode (2b) at the divided portion is exposed. A part of the semiconductor film (3) does not remain on the portion (2b ').

Further, the flat surface (2flat) of the light-receiving surface electrode (2b) divides the back electrode (4) applied over a plurality of photoelectric conversion element regions into photoelectric conversion elements (5a) (5b). 7th
It is formed in advance even before the process shown in the drawing. Therefore, the back electrodes (4) are individually (4a) and (4b) by the process of FIG.
The back electrode (4a) that is divided and exposed as
The side surfaces (4as) (4bs) of (4b) face the flat surface (2flat) of the light-receiving surface electrode (2b), and sandwich the semiconductor film (3b) together with the light-receiving surface electrode (2b) so that the photoelectric conversion element (5b ), A sufficient insulation distance is formed with the back electrode (4b).

Thus, the photoelectric conversion characteristics of the photovoltaic device manufactured by the manufacturing method of the present invention (hereinafter, referred to as the device of the present invention) were measured by irradiating sunlight at AM-1 under the equator with light of 100 mW / cm ³ . . The device of the present invention provided for measurement has a light receiving area of 10 cm.
The photoelectric conversion elements (5a) to 14 stages of × 10 cm are connected in series. For comparison, the flattening step of FIG. 3 among the manufacturing steps of FIGS. Except for the above, the photoelectric conversion characteristics of the comparative device manufactured in the same process except the above were measured, and the results are summarized in Table 1.

As described above, in the device of the present invention, the resistance value mainly in the series connection portion can be reduced, so that the short-circuit current increases and the output increases by about 10%.

Further, 100 each of the device of the present invention and the comparative device were created, and an output of 700 mW or more under irradiation conditions of AM-1, 100 mW / cm ³ was regarded as a good product, and a product of less than that was a defective product. The good yield was 98, the bad yield was 2 and the production yield was 98%, whereas the comparison device was 90 good and the bad was 10 and the production yield was 90%. Not only that, the short-circuit accident was avoided, and as a result, the production yield was improved.

(G) Effect of the Invention As is apparent from the above description, the manufacturing method of the present invention is such that the other back electrode of the adjacent photoelectric conversion element is electrically connected in series with the electrical extension portion in a concavo-convex pattern on one light-receiving surface electrode. Even if the semiconductor film is irradiated with an energy beam for each photoelectric conversion element by performing a flattening process on the surface serial connection portion in advance, the scattering of the energy beam is suppressed and the beam can be focused. Does not remain in the divided portion, and it is possible to prevent the resistance value from increasing in the series connection portion. Therefore, the photoelectric conversion characteristic can be improved by providing the light receiving surface electrode with the uneven surface even in the series-connected photovoltaic device.

[Brief description of drawings]

1 to 7 are enlarged cross-sectional views of a main part showing the manufacturing method of the present invention for each step, and FIG. 8 is an enlarged cross-sectional view of a main part showing a conventional apparatus.
FIG. 9 is an enlarged sectional view of an essential part showing one step of a conventional manufacturing method. (1) ... substrate, (2) (2a) (2b) ... light-receiving surface electrode,
(2flat): flat surface, (2tex): uneven surface, (3)
(3a) (3b) …… Semiconductor film, (4) (4a) (4b) …… Back electrode.

Claims (1)

[Claims] 1. A plurality of unit photoelectric conversion elements are formed by arranging a light-receiving surface electrode having at least an uneven surface on an insulating surface of a translucent substrate, and laminating a semiconductor film and a back electrode on the uneven surface of the light-receiving surface electrode. And a method for manufacturing a photovoltaic device in which one light-receiving surface electrode of an adjacent photoelectric conversion element is electrically coupled to an electrical extension of the other back electrode so as to connect the photoelectric conversion elements in series, Prior to dividing the semiconductor film deposited over the photoelectric conversion element region of each photoelectric conversion element by irradiation with an energy beam, the electrical extension of the other back electrode is electrically connected in series. A method for manufacturing a photovoltaic device, characterized in that the series connection portion of the uneven surface of the one light-receiving surface electrode is preliminarily flattened.