JPH0851229A - Integrated solar battery and its manufacture - Google Patents

Abstract

PURPOSE:To prevent inferiority of processed shapes or electrics shortage by the laser scribe of an electrode at the rear of a metallic film which also functions as a reflecting plate, in processing for integration of a film solar battery. CONSTITUTION:A firsts transparent conductive film is stacked on a translucent insulating substrate 1, and then it is patterned, and thereon a photoelectric transfer layer 3 of amorphous silicon is stacked, and it is patterned by laser scribing, and thereon a second transparent conductive film 4 is stacked, and it is patterned by laser scribe, and a cell is connected in series thereby being integrated, and then thereon a translucent insulating film 6 is made, and further thereon a rear reflecting film 7 is stacked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in the structure and manufacturing method of integrated thin film solar cells.

[0002]

2. Description of the Related Art Generally, an integrated type thin film solar cell has tin oxide (SnO) formed on a transparent insulating substrate such as glass as a light receiving surface.
₂ ) or an electrode made of a transparent conductive film such as indium tin oxide (ITO) is formed, and a metal thin film back surface electrode which also functions as a semiconductor photoelectric conversion layer and a reflector such as crystal or amorphous is laminated on the electrode. It is formed.

Since the amorphous semiconductor photoelectric conversion layer is formed by vapor phase growth such as plasma CVD method or light CVD method by glow discharge decomposition of raw material gas, it has an advantage that a large area thin film can be formed.

Further, an integrated type is formed by a series connection structure in which a metal thin film back surface electrode of one photoelectric conversion element electrically contacts an end portion of an electrode formed of a transparent conductive film on the light receiving surface side of an adjacent photoelectric conversion element. Examples of means for dividing each photoelectric conversion element include a photoetching method and a laser scribing method.

The photo-etching method involves many steps such as resist film coating and is complicated, and the production cost increases as the area of the thin-film solar cell substrate increases. In addition, the film surface is damaged during the chemical treatment step of immersing in the resist film removing liquid, which causes a reduction in conversion efficiency of the solar cell.

On the other hand, in the laser scribing method, the photoetching process for the metal thin film rear surface electrode serving as the reflection film is eliminated, so that the production process is simplified and the production cost can be kept low. Furthermore, since the groove width of the element division formed by laser scribing can be narrowed, for example, it can be processed to 100 μm or less, the area of the electrode bonding portion of the photoelectric conversion element can be small, and the area not involved in photoelectric conversion is small, and thus the integrated The effective power generation area of the thin film solar cell can be increased.

[0007]

When the thin film solar cell is to be integrated by the above-mentioned laser scribing method, the most problematic problem is the patterning of the metal thin film rear surface electrode which becomes the reflector.

FIGS. 4A, 4B and 4C are sectional views of an example of an integrated type thin film solar cell for explaining the patterning of the metal thin film back electrode. On the surface of the translucent insulating substrate 1, a first transparent conductive film 2, a photoelectric conversion layer 3, a second transparent conductive film 4, which is one of the electrodes, and a metal thin film back electrode 8 which is a reflector are laminated. . In the photoelectric conversion layer 3, the scribe groove 11 penetrating the photoelectric conversion layer 3 is filled with the material of the transparent conductive film 4, so that the plus side and the minus side of the photoelectric conversion layer are connected. This is separated by the scribe groove 12 for each photoelectric conversion element, and each element is integrated because it is connected in series.

At this time, for example, when the Q-switch YAG laser beam is used to scribe from the metal thin film rear surface electrode 8 side, if the power of the laser beam is weak, FIG.
As shown in (a), the surface of the metal thin film rear surface electrode 8 reflects the laser beam, resulting in cutting failure, the second transparent conductive film 4 is not divided, and adjacent power generating elements are short-circuited. .

Further, when the power of the laser beam is strong, the metal thin film back electrode 8 is cut as shown in FIG. 4B, but the photoelectric conversion layer 3 of an amorphous semiconductor laminated thereunder is cut off.
Also, the first and second transparent conductive films 2 and 4 are also cut, and the series connection between the photoelectric conversion elements is insulated and cut off, which makes integration impossible.

Further, since the scribe by the laser beam is originally a local thermal processing, the metal thin film rear surface electrode 8
Even if the amorphous semiconductor photoelectric conversion layer 3 and the first and second transparent conductive films 2 and 4 stacked below are not cut,
Thermal damage is caused, and the scattered substances of the metal film come into contact with the lowermost transparent conductive film or remain in the scribe groove, resulting in an electrical short circuit. As described above, in the laser scribing from the surface of the metal thin film rear surface electrode 8 serving as a reflective film, the laser power and the scribing processing speed must be controlled extremely delicately, and a laminated film having different thermal conductivity, melting point, and sublimation property is required. It is extremely difficult to selectively process.

In order to solve this, as shown in FIG. 4 (c), for example, a YAG laser second harmonic (wavelength: 0 ..
(53 μm) from the surface of the translucent insulating substrate 1 to allow the laser beam to pass through without damaging the translucent insulating substrate 1 and the transparent conductive film laminated on the translucent insulating substrate 1 to be absorbed by the photoelectric conversion layer 3,
A method has been proposed in which sublimation and evaporation are performed, and at the same time, the metal thin film rear surface electrode 8 laminated thereon is also blown away to perform scribing processing. If necessary, scattered matter of the metal film is likely to come into contact with the first transparent conductive film 2 of the lowermost layer, or the metal thin film rear surface electrode 8 is peeled off to cause an electrical short circuit.

In order to improve the conversion efficiency of the solar cell, each laminated film has a textured structure,
Furthermore, due to variations in the film thickness of the metal thin film back electrode layer that serves as a reflection plate, there is a concern that processing reproducibility and reliability under one scribe condition are low, resulting in a reduction in yield in the production process.

In any case, in the conventional structure, since the metal thin film serving as the reflective film on the back surface also serves as the collector electrode, it is necessary to pattern this metal thin film electrode on the back surface for serial integration. However, when patterning by the laser scribing method is applied to this, it is difficult to raise the yield by causing a defective machining shape or an electrical short circuit.

[0015]

In the solar cell of the present invention, a first transparent conductive film is formed on a translucent insulating substrate, patterned into strips, and then an amorphous semiconductor photoelectric conversion layer is formed thereon. Laser light is applied to form a scribe groove for patterning, a second transparent conductive film is laminated on the scribe groove, and the laser light is transmitted from the opposite side of the laminated surface of the translucent insulating substrate for irradiation. After forming a scribe groove and processing the photoelectric conversion layer into a state in which a plurality of photoelectric conversion elements are connected in series,
A translucent insulating film is formed on the surface, and a reflective film layer is further formed thereon.

Further, after processing a plurality of photoelectric conversion layers electrically connected in series, the second photoelectric conversion layer on the surface of each photoelectric conversion element is processed.
After laminating the metal electrode on the transparent conductive film, the transparent insulating film is formed, and the reflective film is formed thereon.

[0017]

According to the present invention, since the back surface reflection film is formed by serially integrating only the first and second transparent conductive films and the translucent insulating film, the metal thin film back surface electrode serving as the reflection film is formed. Since it is not necessary to perform laser scribing on the metal thin film, there is no defect in the processed shape that has been conventionally caused in the patterning process of the metal thin film, and the peeling of the metal thin film rear surface electrode and the electrical short circuit caused thereby are eliminated.

Further, after processing the photoelectric conversion layer into a state in which a plurality of photoelectric conversion elements are electrically connected in series, a metal electrode is laminated on the second transparent conductive film electrode of each photoelectric conversion element, and then, In the structure in which the translucent insulating film is formed on the transparent insulating film and the reflective film is formed on the transparent insulating film, the direction of serial integration (scribing direction) is larger than that in the case of serial integration of only the first and second transparent conductive films. The series resistance in the direction (orthogonal direction to) can be suppressed low, and depending on the shape of the metal electrode, a light scattering effect can be obtained, which contributes to improvement of photoelectric conversion efficiency.

[0019]

1 is a perspective view of a part of an integrated solar cell according to the present invention. For example, on the surface of a transparent insulating substrate 1 such as glass, a first transparent conductive film 2, a photoelectric conversion layer 3 made of an amorphous semiconductor, a second transparent conductive film 4, a transparent insulating film 6, a metal. The back reflection film 7 and the like are laminated.

Here, the photoelectric conversion layer 3 is filled in the scribe groove 10 formed in the first transparent conductive film 2 and reaches the transparent insulating substrate 10, and the second transparent conductive film 4 is formed. The scribed grooves 11 formed in the photoelectric conversion layer 3 are filled with the adjacent photoelectric conversion elements, and the adjacent photoelectric conversion elements are connected in series. The transparent insulating film 6 includes the second transparent conductive film 4 and the photoelectric conversion layer 3.
The photoelectric conversion elements are completely separated by filling the scribe groove 12 formed in the above.

On the surface of the second transparent conductive film 4, for example, a comb-shaped metal electrode 5 is provided. This can be omitted.

Such a device is manufactured as follows. The first embodiment is a case where the metal electrode 5 is not provided on the surface of the second transparent conductive film 4.

First, as shown in FIG. 2A, a glass substrate having a thickness of 1 mm, for example, is used as the translucent insulating substrate 1, and the first transparent conductive film 2 serving as one electrode is formed on one surface thereof.
As an example, a SnO ₂ film having a thickness of 1 μm and atmospheric pressure C
It is formed by VD. Next, the first transparent conductive film 2 is irradiated with laser light to be patterned. More specifically, the SnO ₂ film on the glass substrate is scribed with a fundamental laser beam of an Nd-YAG laser (wavelength: 1.06 μm) to form scribe grooves 10, 10 ... And divided into strips. Complete insulation with a scribe width of 30 μm and a depth of 1 μm. Each strip becomes an electrode on the light-receiving surface side of each photoelectric conversion element. The width of each strip is, for example, 1 cm. The laser light applied at this time may be either an Nd: YAG laser or an excimer laser, but the YAG laser is industrially superior because it is easy to maintain and the running cost is low.

Next, as shown in FIG. 2B, the first transparent
On the surface of the bright conductive film 2, a p layer of an amorphous semiconductor photoelectric conversion layer is formed.
Is laminated to a thickness of 12 nm. In the plasma CVD equipment
The substrate is placed and the substrate temperature is raised to 200 ° C. Reaction gas
Is a monosilane gas flow rate of 30 _sccm, Flow rate of methane gas 8
0_sccmThe carrier gas is hydrogen gas with a flow rate of 150._sccm, De
The flow rate of diborane gas diluted with 1% hydrogen is 1
0_sccmFlush with. Subsequently, an i layer is laminated to a thickness of 400 nm.
To do. At this time, the substrate temperature was kept at 200 ° C.
The flow rate of monosilane gas is 60_sccm, The carrier gas is water
Flow rate of elementary gas is 20_sccmFlush with. Then, n layer is 100 nm
To the thickness of. The substrate is kept at 200 ° C and the reaction gas
Is a monosilane gas flow rate of 60_sccm, The carrier gas is hydrogen
Gas flow rate 3_sccm, Doping gas is diluted with 0.3% hydrogen
Flow rate of 18 phosphine gas_sccmFlush with. Scribe groove
10 is filled with an amorphous semiconductor. In this way, non
After stacking a crystalline semiconductor photoelectric conversion layer, it transmits laser light
Irradiate from the surface of the insulating substrate to form the scribe groove 11, and
Give the training.

More specifically, the photoelectric conversion layer 3 made of an amorphous semiconductor is separated from the previous scribe groove 10 by a groove center line distance of 1.
An insulating substrate 1 which is transparent to laser light of Nd-YAG laser second harmonic (wavelength: 0.53 μm) at positions separated by 00 μm
Irradiate from the surface, scribe and scribe grooves 11, 11 ...
To form. The photoelectric conversion layer is completely divided with the width of the scribe groove being 40 μm. The total thickness of the photoelectric conversion layer 3 is 0.5.
It becomes 12 μm. When the scribe groove 11 is formed, some grooves are formed on the first transparent conductive film 2 as well.
This helps make good contact between the upper and side surfaces of both transparent conductive films when the second transparent conductive film is formed later.

Next, as shown in FIG. 2C, 60 n of ITO is formed as a second transparent conductive film 4 on the photoelectric conversion layer 3.
The thickness of m is laminated by the DC magnetron sputtering method. The scribe groove 11 is filled with ITO. Thereafter, patterning is performed by irradiating a laser beam from the surface of the translucent insulating substrate 1, and a plurality of photoelectric conversion elements are processed into a state in which they are electrically connected in series, whereby integration is performed. More specifically, the ITO is separated from the scribed groove 11 by a groove center line distance of 150 μm from the surface of the translucent insulating substrate 1 with Nd-YAG laser second harmonic (wavelength: 0.53 μm) laser light. By irradiation, the ITO layer is blown off together with the photoelectric conversion layer and scribed to form the scribe grooves 12, 12. The ITO layer and the photoelectric conversion layer are completely divided with the scribe groove width of 40 μm. At this time, the upper portion of the first conductive film 2 is slightly damaged, but it is desirable that the damage is as small as possible. The shorter the distance between the scribe grooves 11 and 12, the better, but it is necessary to consider the processing accuracy and the yield.

Thereafter, as shown in FIG. 2D, as the translucent insulating film 6, for example, organic precursor silazane, which is a thermosetting inorganic high molecular polymer of a ceramic precursor, is applied to the laminated surface by spin coating, The transparent insulating film 6 made of amorphous SiO ₂ is baked to about 1 by baking at 200 ° C. in the atmosphere.
It is formed with a thickness of μm. The groove 12 is filled with the material of the translucent insulating film.

On top of this, as shown in FIG.
Silver is formed to a thickness of 500 nm by the magnetron sputtering method to form the back surface reflection film 7, and an integrated solar cell is formed.

The second embodiment is a case where a metal electrode is provided on the surface of the second transparent conductive film, and each step thereof is shown in FIG.
It is shown in (a) to (f). Since the steps of FIGS. 3A to 3C are exactly the same as the steps of FIGS. 2A to 2C, description thereof will be omitted.

As shown in FIG. 3D, a comb-shaped silver electrode 5 branching and extending in a direction orthogonal to the scribe direction is formed on the second transparent conductive film 4 by screen printing. The screen printing width was 50 μm, the pitch between the comb-shaped electrodes was 0.5 cm, and the scribed groove 1 of the second transparent conductive film 4 was used.
Screen printing is performed on the second layer so that the comb-shaped silver electrodes are not laminated. This makes it possible to reduce the series resistance of the integrated thin-film solar cells in series connection due to the surface resistance of the transparent conductive film, and to reduce the comb structure of the slit electrodes of the comb-shaped silver electrode, as compared with the case where the transparent conductive film alone is connected in series. The effect of scattering incident light can further improve the photoelectric conversion efficiency.

The shape of the metal electrode is not limited to the comb shape, but may be a slit shape in a direction orthogonal to the scribe groove, a lattice shape, a honeycomb structure shape, or the like. Further, as a method for laminating these metal electrodes, there is a vapor deposition method by mask patterning in addition to the screen printing method.

3 (e) and 3 (f) are the same as FIGS. 2 (d) and 2 (e) except that the comb-shaped silver electrode 5 is present, and the description thereof is omitted.

[0033]

According to the present invention, it is not necessary to pattern the metal thin film rear surface electrode also serving as a reflection film with a laser beam when integrating a thin film solar cell, and an electrical short circuit or a photoelectric conversion element caused by the conventional method is not required. Insulation defects in the series connection between the two are eliminated, and the reproducibility of processing and the improvement of reliability can contribute to the improvement of the yield of the production process.

Further, by providing the metal electrode on the second transparent conductive film in a portion excluding the scribe groove so as to be branched in the direction orthogonal to the scribe direction, the series resistance can be suppressed low and the metal electrode can be suppressed. Depending on the shape, the effect of scattering light is further contributed to the improvement of photoelectric conversion efficiency.

[Brief description of drawings]

FIG. 1 is a perspective view of an essential part of an integrated solar cell according to the present invention.

2A to 2E are cross-sectional views of respective steps of the first embodiment according to the present invention.

3A to 3F are cross-sectional views of respective steps of the second embodiment according to the present invention.

4 (a) to 4 (c) are explanatory views of patterning of a metal thin film rear surface electrode also serving as a reflector of an integrated solar cell according to a conventional method.

[Description of Reference Signs] 1 translucent insulating substrate 2 first transparent conductive film 3 photoelectric conversion layer 4 second transparent conductive film 5 comb-shaped silver electrode 6 translucent insulating film 7 back surface reflective film

Front page continued (72) Inventor Hitoshi Sannomiya 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka

Claims (3)

[Claims] 1. A plurality of amorphous semiconductor photoelectric conversion elements which are formed on a light-transmissive insulating substrate which is a light-receiving surface and are connected in series, and a plurality of amorphous semiconductor photoelectric conversion elements, which are opposite to the light-receiving surface of the photoelectric conversion element. An integrated solar cell, wherein a reflective film is provided via an optical insulating film. 2. A step of forming a first transparent conductive film on a translucent insulating substrate, and a step of patterning the first transparent conductive film in a strip shape to form an amorphous semiconductor photoelectric conversion layer thereon. A step of scribing the amorphous semiconductor photoelectric conversion layer and the first transparent conductive film by a laser scribing method, and a second transparent film on the surface of the amorphous semiconductor photoelectric conversion layer and the scribe groove formed by the scribing. A step of forming a conductive film, and scribing the second transparent conductive film and the amorphous semiconductor photoelectric conversion layer by a laser scribing method to process the photoelectric conversion layer into a form in which a plurality of photoelectric conversion elements are connected in series. A step of forming a translucent insulating film on the surface of the second transparent conductive film and the scribe groove formed by the scribe, and a step of forming a reflective film on the surface of the translucent insulating film. A method for manufacturing an integrated solar cell, which comprises: 3. A metal electrode having a large number of branches extending in a direction orthogonal to the scribe groove is formed on the surface of the second transparent conductive film on the surface of each photoelectric conversion element connected in series. The method for manufacturing the integrated solar cell according to claim 2.