JPH0799775B2 - Solar cell - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a solar cell, and more particularly, to reducing the area occupied by a current collector for collecting current in the solar cell and increasing the effective efficiency of the solar cell. It was done.

[Prior Art and its Problems] Solar cells, which directly convert light energy into electric energy by utilizing the photovoltaic effect of semiconductors, are devices that have been attracting attention for their effective use in Japan, which is a country with few resources. Is.

In order to effectively convert light energy, solar cells (1) To effectively guide light energy into the semiconductor section (photoelectric conversion section).

(2) Generation of optical carriers.

(3) Polarization of photogenerated carriers by the internal electric field.

(4) Effective collection of polarized carriers.

It has four basic functions.

Usually, a solar cell has a structure in which a photoelectric conversion layer is sandwiched between two electrodes, but the electrode arranged on the light incident direction side of the two electrodes is formed of a translucent conductive film. This translucent conductive film must be formed thin in order to maintain translucency, but if it is formed thin, the resistance of the electrode itself increases as the area of the solar cell increases. There was a problem that the current collection efficiency was reduced.

Therefore, as described in JP-A-56-130977, a structure has been proposed in which a comb-shaped current collector (grid electrode) made of a good conductive material is formed on a transparent conductive film. ing.

That is, as shown in FIGS. 7 (a) to 7 (e) together with the manufacturing process, for example, a comb-shaped grid having a strip portion B for collecting electric power as a collector electrode on a translucent glass substrate 101. An electrode 102 is formed, and an indium tin oxide (ITO) electrode as a transparent conductive film 103, an amorphous silicon (a-si) layer as a photoelectric conversion layer 104, and a metal electrode 105 are formed on the electrode 102 as usual. And a chrome electrode as described above are laminated to form a solar cell. Then, this solar cell output is taken out between the collector electrode 102 and the metal electrode 105.

In such a structure, the resistance of the power extraction part becomes small, but the part where the collector electrode exists does not work as a solar cell (due to the attenuation of the amount of incident light), so the light receiving area becomes smaller accordingly, and in particular The existence of the strip portion B for taking out is a big problem from the viewpoint of effective use of light. This problem can be improved to some extent by optimizing the shape of the collector electrode, but it was difficult to solve it fundamentally.

[Means for Solving Problems] The present invention has been made to solve the above problems, and aims to increase the light receiving area and reduce the resistance of the electrode extraction portion, thereby increasing electromotive force and reducing power loss. The purpose is to reduce. Therefore, in the present invention, in a solar cell in which a photoelectric conversion layer is sandwiched by a translucent first electrode and a second electrode, for collecting current via an insulating layer on the back surface of the solar cell, that is, on the side opposite to the light incident direction. Is formed, and this electrode is electrically connected to the first electrode.

A first feature of the present invention is that a translucent first electrode integrally formed on substantially the entire surface of a translucent substrate and a photoelectric conversion layer sequentially laminated in a stripe pattern at a predetermined interval. And a second electrode, formed to cover the second electrode and side walls of the second electrode and the photoelectric conversion layer, and to expose a part of the first electrode. An insulating film, and a third electrode for current collection integrally formed so as to cover the first electrode exposed on the insulating film over the entire upper surface of the insulating film. This is because light is made incident from the electrode side of No. 1.

A second feature of the present invention is that the surface of the metal substrate is covered with stripes so that the edges are aligned, and the insulating film and the first electrode are sequentially laminated, and the first electrode is covered up to the side wall. A photoelectric conversion layer formed to expose a part of the metal substrate, and a translucent second electrode formed on the entire upper surface of the photoelectric conversion layer and covering the surface of the metal substrate exposed from the photoelectric conversion layer. And that light is incident from the second electrode side.

[Operation] That is, in the solar cell of the present invention, the current generated from each part is guided from the translucent first electrode to the current collecting electrode formed on the back surface beyond the photoelectric conversion layer, Electric current is taken out on the back surface side of the solar cell.

Therefore, the strip portion B for extracting electric power, which has been conventionally required, becomes unnecessary, and the effective light receiving area increases.

Further, the present invention intends to increase the light receiving area and reduce the resistance of the electrode lead-out portion, and form a collector electrode on the entire back surface side to increase electromotive force and reduce power loss. With this feature, the electrode lead-out area is not required, and the light receiving area can be maximized (increase in electromotive force). Further, in the first, the metal electrode is integrally formed so as to cover the entire surface of the substrate, and in the second, the transparent second electrode is brought into contact with the metal substrate. The distance between the third electrode for collecting electricity and the transparent first electrode or the distance between the metal substrate and the transparent second electrode is set to be extremely short by using the surface. The resistance of the take-out portion is greatly reduced, and the take-out loss is extremely small (reduction of power loss).

Embodiments of the Invention Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Example 1) This solar cell has a top view in FIG. 1 (a) and FIG. 1 (b).
To (d), respectively, are cross-sectional views taken along the line AA of FIG.
As shown in the cross-sectional views B-C and C-C, an indium tin oxide (ITO) electrode 2 (translucent conductive film) as a surface electrode formed on the entire surface of the translucent glass substrate 1, An amorphous silicon layer 3 as a photoelectric conversion layer and a first electrode as a back electrode, which are sequentially laminated on the indium tin oxide electrode 2 in a plurality of strips at predetermined intervals.
Aluminum electrode 4, a strip-shaped laminated body of the photoelectric conversion layer and the aluminum electrode for each strip, and a silicon nitride film 5 as an insulating layer, and the substrate surface excluding the electrode lead-out portion T ₁ on the upper layer. It is composed of a second aluminum electrode 6 as a current collecting electrode formed over the entire surface, and is arranged so that light enters from the glass substrate 1 side as indicated by an arrow L ₁ .

Next, a method for manufacturing this solar cell will be described.

First, as shown in FIG. 2A, the translucent glass substrate 1
On the other hand, indium oxide 95 mol% + tin oxide (SnO ₂ ) 5 mol
%, A sputtering target is used to form an indium tin oxide electrode 2 having a film thickness of about 500 Å. This indium tin oxide electrode had a sheet resistance of 5 Ω / port.

Then, as shown in FIG. 2 (b), the amorphous silicon P layer 3P, the amorphous silicon I layer 3I, and the amorphous silicon N are formed by a glow discharge decomposition method of monosilane (SiH ₄ ) gas through a metal mask (not shown). Layer 3N 3
An amorphous silicon layer 3 composed of layers is formed. At this time, the thickness of each of the amorphous silicon P layer, the amorphous silicon I layer, and the amorphous silicon N layer is 10 respectively.
0Å, 5000Å and 500Å, diborane (B ₂ H ₆ ) was added as a dopant for forming the P layer, and phosphine (PH ₃ ) was added as a dopant for forming the N layer.

Subsequently, the metal mask is left as it is, and the first aluminum electrode 4 as the back surface electrode is formed on the amorphous silicon layer 3 by the electron beam evaporation method as shown in FIG. 2 (c).
Form only on top.

After that, the metal mask was converted to a narrow one, and the glow discharge decomposition method using a mixed gas of monosilane (SiH ₄ ) and ammonia (NH ₃ ) was performed, as shown in FIG. 2 (d).
A silicon nitride film (Si ₃ N ₄ ) 5 is formed so as to cover the amorphous silicon layer 3 and the first aluminum electrode 4.
To form. At this time, it is necessary to install a metal mask so that the silicon nitride film is not formed also on the power extraction portion on the back electrode side.

Finally, as shown in FIG. 2 (e), a second aluminum electrode 6 having a film thickness of 1 μm is formed on the entire surface of the substrate excluding the power take-out portion of the back electrode by the electron beam evaporation method, and the sun of the present invention is formed. The battery is completed.

The voltage-current output characteristics of this solar cell under AMI of 100 mW / cm ² light illuminance were as shown in FIG. The area of this battery is 10 × 10 cm ² . Here, the vertical axis represents the output current (A) and the horizontal axis represents the output voltage (V). As is clear from this figure, open-circuit voltage 812 mV, short-circuit current 1.47 A, maximum output
With 0.77W, a large output can be obtained for the outer shape of the solar cell.

That is, a current collecting electrode for the light-transmitting front surface electrode of this solar cell is formed on almost the entire surface on the back surface electrode side through an insulating layer, and the current obtained at the front surface electrode is guided to this current collecting electrode. Therefore, unlike the conventional solar cell shown in FIG. 7 (e), it is not necessary to provide a power extraction portion from the surface electrode, and the effective area of the solar cell can be increased, thereby increasing the effective efficiency. Can be increased.

When a comb-shaped grid electrode is provided as a collector electrode like the conventional solar cell shown in FIG. 7 (e), the grid must be formed as high as possible (thick) to reduce the resistance of the grid. However, in the solar cell of the present invention, the current collecting electrode on the front surface is formed on the entire back surface,
Since the desired resistance value can be obtained with a relatively thin film thickness, the collector electrode can be easily formed.

In the examples, the sputtering method was used to form the indium tin oxide as the surface electrode, but other methods such as an electron beam evaporation method may be used.

Although a silicon nitride film was used as an insulating layer for insulating the collector electrode and the back electrode, a silicon oxide film formed by an electron beam evaporation method using silicon oxide SiO as a target, and a screen printing method. An epoxy resin film or the like can also be applied.

(Example 2) This solar cell is shown in Figs. 4 (a), (b), (c) (fourth example).
(B) and (c) are stainless steel substrates as shown in FIGS. 4 (a) and 4 (b), respectively.
A plurality of insulating layers 12 made of a polyimide resin formed in a strip shape on 11 and an aluminum layer as a back electrode 13 and amorphous silicon as a photoelectric conversion layer 14 sequentially laminated on the insulating layer 12. A transparent indium tin oxide layer is formed as a surface electrode 15 formed on the layer and the upper layer thereof so as to cover the entire substrate surface, and the amorphous silicon layer also covers the side surface of the back surface electrode 13.
Prevents short circuit between front surface electrode 15 and back surface electrode 13
15 is in contact with the stainless steel substrate 11 at one part and is electrically connected and is configured to be used as a collecting electrode. The surface of the stainless steel substrate 11, that is, the side where the photoelectric conversion portion is formed is indicated by an arrow L ₂ As shown in (1), it is arranged and used so that light is incident.

Next, a method for manufacturing this solar cell will be described.

First, as shown in FIG. 5 (a), the width W = 1.5 cm and the interval B = on the stainless steel substrate 11 by the screen printing method.
Polyimide resin film consisting of 0.5-1 mm strip-shaped patterns
Forming twelve. At this time, as shown in FIG. 4A, a polyimide resin film is also formed on a part of the side surface of the substrate 1.

Next, as shown in FIG. 5B, an aluminum layer as the back electrode 13 is selectively formed on the upper layer of the polyimide resin film 12 by a partial vapor deposition method using a metal mask (not shown). Also at this time, as shown in FIG. 4 (a), the aluminum layer is also extended to a part of the side surface of the substrate 1.

Thereafter, a photoelectric conversion layer 14 composed of three layers of an amorphous silicon N layer 14N, an amorphous silicon I layer, and an amorphous silicon P layer 14P is formed by a glow discharge decomposition method of monosilane (SiH ₄ ) gas using a metal mask having a smaller width.
Are selectively formed (FIG. 5 (c)). At this time, since the metal mask whose width is smaller than that of the metal mask when the back electrode is formed is used, the photoelectric conversion layer is formed in a shape that covers each side surface of the strip-shaped back electrode 13.

Finally, as shown in FIG. 5 (d), an indium tin oxide layer 15 as a surface electrode 15 is formed on the entire surface of the substrate by vacuum vapor deposition to complete the solar cell of the present invention.

In this solar cell, the translucent indium tin oxide electrode as the surface electrode is ohmic-connected to the stainless steel substrate 11, and the current obtained at the surface electrode is guided to the stainless steel substrate 11 as the current collecting electrode. Therefore, the power loss in the current collector can be significantly reduced. Further, since it is not necessary to form a large power take-out portion as in the case where a comb-shaped grid electrode is used as a current collecting electrode as in the conventional case, the effective battery area is increased and the effective efficiency of the solar cell is improved.

Also, because the power output part is provided on the side of the battery,
Series connection between batteries is easy. For example, as shown in FIG. 6, two solar cells S1 and S2 are arranged on a support D, and the side surfaces of the stainless steel substrate 11 are connected with a conductive adhesive P to connect the solar cells S1 and S2 in series. You can
In this way, a large number of solar cells can be connected in series without area loss.

In the example, in order to prevent a short circuit between the aluminum electrode 13 formed in a strip pattern as the back electrode and the indium tin oxide electrode as the front electrode 15, each strip is provided by extending the photoelectric conversion layer. Although each pattern is formed so as to cover the side surface of the back electrode, an insulating layer may be formed separately from the photoelectric conversion layer so as to cover the side surface of the back electrode.

In addition, when forming the strip-shaped conductive film as the back electrode, it is needless to say that in addition to partial vapor deposition using a metal mask, pattern formation may be performed by photolithographic etching after forming the entire surface. .

Further, in both (Example 1) and (Example 2), the back electrode and the photoelectric conversion layer were divided into strips, and the front electrode and the current collecting electrode were electrically connected in the portion between them. However, the invention is not necessarily limited to this, and it is possible to appropriately change it by forming a connecting portion in a lattice shape.

[Effects of the Invention] As described above, according to the present invention, a current collecting electrode is formed on the back surface of the solar cell, that is, on the side opposite to the incident direction of light, and the current is guided from the transparent electrode on the front surface. As a result, compared to the case where a conventional comb-shaped grid electrode is used as the current collecting electrode, the effective battery area is significantly improved, and the power collecting electrode can be made large in area, which reduces power loss. To be done.

Further, when forming a comb-shaped grid electrode, it must be formed thick (about 10 μm) in order to reduce the resistance, and it is difficult to form a predetermined film thickness by a plating method after vapor deposition. However, according to the method of the present invention, the formation of the collecting electrode becomes extremely easy.

Further, the power take-out portion can be provided on the side surface or the back surface, which facilitates electrical connection.

[Brief description of drawings]

1 (a) to 1 (d) are views showing a solar cell according to a first embodiment of the present invention, and FIGS. 1 (b) to 1 (d) are A- of FIG. 1 (a), respectively. (A cross section, BB cross section, and CC cross section), and FIGS. 2A to 2E are FIGS. 1A to 1.
FIG. 3 is a manufacturing process diagram of the solar cell shown in (d), FIG. 3 is a current-voltage characteristic curve of the same solar cell, and FIGS.
Is a diagram showing a solar cell of a second embodiment of the present invention,
(B) and (c) of FIG. 4 (a) are cross-sectional views taken along the line aa and the cross-section of the bb), and FIGS. 5 (a)-(d).
Is a manufacturing process diagram of the solar cell shown in FIGS. 4 (a) to (c), FIG. 6 is a diagram showing a connection example of the solar cell of the present invention, and FIGS. 7 (a) to (e) are It is a figure which shows the structure of the solar cell of a prior art example with the manufacturing process. 101 ... Glass substrate, 102 ... Comb type grid electrode, 103 ... Translucent conductive film, 104 ... Photoelectric conversion layer, 105 ... Metal electrode, 1 ...
Glass substrate, 2 ... Indium tin oxide electrode, 3 ... Amorphous silicon layer, 4 ... First aluminum electrode, 5 ... Silicon nitride film, 6 ... Second aluminum electrode, 11 ... Stainless substrate, 12 ... Insulating layer, 13 ... Back electrode, 14 ... Photoelectric conversion layer, 15 ... Front electrode, D ... Support base.

Claims (2)

[Claims] 1. A transparent first electrode integrally formed on substantially the entire surface of a transparent substrate, a photoelectric conversion layer and a second photoelectric conversion layer sequentially stacked in a stripe pattern at a predetermined interval. An electrode, and an insulating film formed to cover the second electrode and to cover the sidewalls of the second electrode and the photoelectric conversion layer and to expose a part of the first electrode. Further comprising a third electrode for current collection formed over the entire upper surface of the insulating film and covering the first electrode exposed from the insulating film, wherein light from the first electrode side is emitted. A solar cell characterized by being incident. 2. An insulating film and a first film, which are sequentially laminated on the surface of a metal substrate so that the edges are aligned with each other.
Electrode, a photoelectric conversion layer formed so as to cover the first electrode to the side wall and expose a part of the metal substrate, and the photoelectric conversion layer formed on the entire upper surface of the photoelectric conversion layer. Second light-transmitting material that covers the surface of the metal substrate exposed from the
A solar cell comprising an electrode, wherein light is incident from the second electrode side.