JPH0458711B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a solar cell having high reliability and quality with excellent practicality.

[Conventional technology]

In order to configure a photoelectric conversion device as a cheaper and highly reliable system, the following are required: (1) the first and second electrodes, (2) the semiconductor layer that generates photovoltaic force, and (3) the mechanical aspects of the device. (4) A terminal for electrical connection with the outside, (5) Various mechanical adhesion properties of the terminal to the substrate, (6) One of the two electrodes is optically transparent. (7) The first and second electrodes and the semiconductor layer must be guaranteed against mechanical strain; (8) The semiconductor layer must have high photoelectric conversion efficiency. .

In addition, as photoelectric conversion devices, (9) the manufacturing cost of semiconductor layers is low, (10) conversion devices using semiconductor layers are easy to manufacture and have a simple structure, and (11) compared to semiconductor layers. It is important that the equipment attached to the lever is not expensive, (12) that the conversion device is easy to handle, and (13) that it has high long-term reliability.

However, in conventional photoelectric conversion devices, the semiconductor that generates photovoltaic force itself is expensive, and
The system, including its auxiliary equipment, had not been properly thought of.

Conventionally, for example, when trying to fabricate a solar cell using CZ (Czyochoralski) slices, the amount of power generated was
Assuming that 10KW/year and the required silicon raw material are 8000 tons/year, it will cost 4160 yen per 1W.

Furthermore, the cost is 74%, or 3,070 yen, for the cell section that generates the photovoltaic force, and an additional 1,090 yen (26%) for other equipment that needs to be converted into electricity.

And this price is 1/ from 4160 yen/W.
There were many difficulties in reducing the price to 40 yen/W for 100.

For example, in order to save raw materials, silicon wafers are made thinner by 1 to 2 μm, but the wafer used for the cell part always requires a substrate because it also has the precision of a substrate with mechanical strength.

Furthermore, when a thin film semiconductor is used, there is a problem in that terminals for connecting external leads from the substrate cannot be directly bonded to the semiconductor layer.

For this reason, the cost of the semiconductor layer is simply reduced to 3070
Even if it were possible to reduce the price to 30 yen/W, which is 1/100th of the yen/W, it would have cost more than ever to make it into a module.

[Problems with conventional technology]

When thin film semiconductors are used to construct a solar power generation system at low cost, the problems described above have arisen.

Another problem is that the photoelectric conversion layer has a diode structure, so when no photovoltaic force is generated or when the photovoltaic force becomes weak, current is generated by the back electromotive force from the external load. There was a problem with backflow.

In particular, in the case of power generation systems that use sunlight, where the amount of power generated is unstable, a large loss of generated power occurs due to reverse current.

In addition, if a configuration in which multiple photovoltaic power generators are connected is constructed and some of the photovoltaic power generators are damaged and shot due to some reason, a large amount of backflow current may occur in this part. Power loss had occurred.

Furthermore, when a metal thin film formed by sputtering or vapor deposition is used as an electrode or wiring, the thin film becomes extremely thin in vertical portions, resulting in problems such as disconnection, electrical instability, and poor withstand voltage.

[Purpose of the invention]

An object of the present invention is to provide a photovoltaic power generation device that has high productivity, is low cost, and has no loss of generated power due to backflow current.

Furthermore, it is an object of the present invention to provide a highly reliable photovoltaic power generation device that is free from problems such as electrical instability and poor breakdown voltage in electrode wiring portions.

[Structure of the invention]

The present invention is a photovoltaic power generation device comprising a photoelectric conversion device having a non-single crystal semiconductor layer provided on an insulating substrate, and a backflow prevention diode connected to the photoelectric conversion device, the backflow prevention device comprising: The diode is provided on the insulating substrate using the same material and having the same configuration as the non-single crystal semiconductor layer that forms the photoelectric conversion device, and the non-single crystal semiconductor layer that forms the photoelectric conversion device and the backflow prevention diode. The photovoltaic power generation device is characterized in that the periphery of the side is formed into a tapered trapezoid.

The present invention provides a semiconductor device that generates a photovoltaic force on an insulating substrate, and furthermore, connects to one output of the semiconductor device to make it easier for current to flow into the photoelectric conversion device and to make it difficult for current to flow into the photoelectric conversion device. It is characterized by the provision of a backflow prevention diode whose direction is reversed.

In addition, the semiconductor layer constituting this backflow prevention diode is configured to have the same semiconductor layer as the semiconductor layer that generates photovoltaic force, and the semiconductor layer that configures the backflow prevention diode and the semiconductor layer that generates photovoltaic force are also the same. In order to solve the problem of disconnection and leakage around the sides, as well as the problem of electrical instability, the sides of these semiconductor layers are characterized by having a trapezoidal taper shape or a bevel shape.

Example 1 Examples using the present invention will be described below.

This example has a configuration in which light is incident from the upper surface of the substrate, and a transparent electrode provided on an insulating substrate and a thin film of a non-single crystal semiconductor doped with hydrogen or a halogen element are formed in approximately the same shape. The goal is to improve the quality, ease of manufacture, and high efficiency.

In this example, a first electrode is placed on a soft or hard insulating substrate, a non-single crystal semiconductor doped with hydrogen or a halogen element that generates a photovoltaic force is placed on the first electrode, and a second electrode is placed on top of the first electrode. The present invention discloses a photoelectric conversion device including a semiconductor device having the above-mentioned semiconductor device and a backflow prevention diode provided on the same substrate as the semiconductor using the same semiconductor material, and a method for manufacturing the same.

In this example, in order to form the side periphery of the semiconductor layer that constitutes the backflow prevention diode and the semiconductor layer that generates photovoltaic force into a trapezoidal taper shape or bevel shape, one electrode is etched in the plasma etching process of the semiconductor layer. The etching was performed while vibrating up and down, left and right, and back and forth.

In addition, at least two bus lines for positive and negative were provided on the board in order to ensure mechanical distortion and to attach an external lead-out end. The bus line is used to form a plurality of semiconductor layers into a matrix, thereby unifying the entire system.

Furthermore, in this embodiment, etching, photo-etching, or selective printing was used for low-cost manufacturing, and the process was completed in 3 to 4 mask steps.

In particular, the manufacturing process is simplified by making the semiconductor layer and the transparent electrode of one of the first or second electrodes approximately the same shape, and the manufacturing process is simplified by making the semiconductor layer and the transparent electrode of one of the first or second electrodes have approximately the same shape. The reliability of the device is improved by providing a lead that extends from the provided electrode to the substrate.

The present invention will be explained below with reference to the drawings.

FIG. 1 shows the manufacturing process of the conversion device of the present invention using a longitudinal sectional view.

In this example, glass (thickness: 1.4 mm) was used as the substrate 1. Furthermore, chromium was deposited on the top surface as the first electrode 2 by electron beam evaporation.
The film was formed to a thickness of .ANG., and etched into a predetermined shape using a chrome etch solution in the first etching step.

As the substrate material, methacrylic resin, epoxy resin, especially glass-epoxy composite material (commonly known as GALA-EPO), fluororesin, polycarbonate, glass, alumina and other ceramics, set mono, etc. can be used as a hard substrate.

Furthermore, polyimide, polyester, silicone resin, etc. can be used as the flexible and soft substrate.

Although chromium was used in this embodiment as a material with excellent adhesion to the substrate for the first conductive electrode 2, it may also be a two-layer film in which chromium is formed and aluminum is further formed on the top surface.

After forming the first conductive electrode,
Non-single crystal semiconductors 3 having a PIN junction were laminated by a glow discharge method.

Specifically, N-type non-single crystal semiconductor (PH ₃ /
SiH ₄ = 0.01, thickness 200 Å, Eg 1.7 eV), type non-single crystal semiconductor (SiH 100%, thickness 0.5 μm, Eg 1.8 eV),
Silicon doped with P-type carbon (CH ₄ :SiH ₄ =
1:1B ₂ H ₆ /SiH ₄ =0.003, thickness 100Å,
Eg2.1eV). These were formed using a glow discharge method (frequency: 13.56 MHz, output: 10 W, pressure: 0.1 torr, film growth rate: 2.1 Å/sec, substrate temperature: 210° C.).

As a semiconductor layer, PN junction, PIN junction,
A configuration that can generate a photovoltaic force by light irradiation, such as a PINPIN junction, a PNPN...PN junction, or a PI ₁ I ₂ N junction, can be used.

In this embodiment, in order to efficiently convert continuous light such as sunlight or white light into electricity,
The energy gap Eg of a non-single crystal semiconductor such as polycrystalline or amorphous semiconductor in which photoelectric conversion is performed has a W-N structure.

In other words, increase Eg on the light irradiation side, that is, W−Eg
(WIDE Eg) to 2 to 3 eV, and reduce the Eg on the other side, that is, 0.7 to N-Eg (NALLOW Eg).
It was set to 1.5eV. The semiconductor material has silicon as its main component, and contains C, N, O, Ge, Sn, Pb,
In, Sb, and Te were added as necessary. Further, as a method for forming the semiconductor layer, it is also possible to use a low pressure CVD method. For these, patent applications and Japanese patent applications No. 53-086867/
086868, patent application 1972-032070/032071, patent application 1972-
071738.

After forming the semiconductor layer 3, a conductive film containing tin oxide as a main component was formed to a thickness of 700 Å by electron beam evaporation as a transparent conductive film 4 serving as a second electrode (on the light incident side).

In this way, a state as shown in FIG. 1B was obtained.
FIG. 1B shows a state in which the upper surface of the semiconductor layer 3 is coated with a second electrode material 4 made of a transparent conductive electrode.

Thereafter, as shown in FIG. 1C, unnecessary portions of the semiconductor layer 12 and transparent conductive electrode 11 were removed by a second etching process using the same mask. By this etching, the semiconductor layers 12 and 1 are formed in approximately the same shape as the patterns 11 and 11' of the transparent electrodes.
2' was etched. That is, the semiconductor layer was etched using the transparent electrode as a mask.

Furthermore, this semiconductor layer has a trapezoidal shape, and the periphery of the trapezoid is tapered.

For etching, a fluorine-based plasma etchant was used. That is, in a plasma etching apparatus having parallel plate type electrodes, a metal mask is used as a transparent electrode, and parts 11, 11', 12, 1 where the semiconductor layer is left are used as the metal mask.
2', and selectively caused plasma discharge only in the area to be removed. At that time, plasma discharge was caused between a common negative electrode under the substrate and a positive opposing electrode provided on the substrate at a distance from the transparent electrode. In this way, there was no need to use a photoresist or the like, and the patterning process could be carried out without mechanically damaging the transparent electrode or semiconductor layer.

During this selective plasma etching, the positive counter electrode is periodically moved up and down, left and right, front and rear by 1 mm to 1 mm.
It was vibrated and moved at 1 to 10 c/s with a width of cm. As a result, the edge portion of the discharge became blurred, and as a result, the side periphery of the semiconductor layer was able to be tapered into a trapezoidal shape.

Moreover, the angle of this taper could be made into a bevel shape to about 45° with respect to the substrate when the vibration period was made the same as the etching speed, and to about 30° when it was doubled.

The conditions for this plasma etching are, for a transparent electrode, the gas used is _CF4 , the frequency is 13.56MHz,
Etching was carried out at room temperature. In the case of semiconductors, etching was carried out under the following conditions: the gas used was CF ₄ +O ₂ (5%), the frequency was 13.56 MHz, and the etching temperature was room temperature.

Furthermore, auxiliary electrodes 30 and 22 shown in FIG. 1D were fabricated by aluminum vacuum evaporation using a stainless steel mask.

The characteristics of the photovoltaic power generator produced as described above are as follows.

Open circuit voltage 0.7V (2 stages in series) Short circuit current 23μA Fill factor 0.5 Irradiation light White fluorescent lamp 300 lx Cell area 10mm x 15mm Area of backflow prevention diode 5mm x 15mm In the above explanation, the transparent electrode is SnO ₂ , indium or antimony. , doped with tellurium. However, the second electrode, the transparent electrode 4
may be a shotgun electrode or an extremely thin insulating film of 20 to 50 Å for forming a shotgun diode.

In this shotgun electrode, instead of a transparent electrode, a metal with a large work function, such as platinum, was formed thin enough to allow light to pass through, with a thickness of 25 to 100 Å.

In addition, in MIS type photoelectric conversion devices, 20 to 50
An insulating film thin enough to allow a tunnel current of 1.5 Å to flow was provided corresponding to 11 and 11', and a lattice-shaped or other metal electrode was provided thereon as a counter auxiliary electrode 22, as shown in FIG. 1D, for example.

In this embodiment, at least two bus lines 5 and 9 are provided on only one surface of the insulating substrate. But one bus line or two
It goes without saying that a portion of the two bus lines may be formed by using a through hole in the insulating substrate and using the opposite or back surface thereof. However, it has the disadvantage of being expensive.

Furthermore, in this example, when selectively forming the conductive electrodes 2 on the insulating substrate 1, a photoetching process using a second photomask was used. However, selective plasma etching or printing methods may be used to simplify and reduce costs.

By forming the side periphery of the semiconductor layer into a tapered trapezoidal shape, which is the structure of the present invention, it is possible to form a lead from the first electrode to the bus line of the substrate along the gentle side periphery of the semiconductor layer. can be done,
We were able to obtain an extremely reliable configuration with little possibility of disconnection of the lead wiring.

Furthermore, since we were able to provide electrically stable leads for the reverse current prevention diode, we were able to increase its reverse breakdown voltage and substantially expand the depletion layer at the PIN junction interface.

In FIG. 1D, a first bus line 5, photoelectric conversion devices 6 and 7 connected in series, a backflow prevention diode 8, and a second bus line 9 are shown. In this way, two photoelectric conversion devices were connected in series to double the output voltage.

FIG. 1D is completed by selectively forming a conductor that will become a part of the second electrode on the upper side of C.
In the drawing, the light 10 is incident on the substrate 1 from above. A first bus line 16 provided closely to the substrate and a first electrode 13 of the photoelectric conversion device 6 are connected by a lead 17. In addition, the counter electrode (referring to the electrode on the side that is irradiated with light), which is the second electrode, is formed by overlapping the transparent electrode 11 with another auxiliary electrode 30 such as a grid line pattern, a crosshatch pattern, a fishbone pattern, etc. Efforts are being made to reduce series resistance. The auxiliary electrode 30 for connection is provided at 20% or less, preferably about 5% of the total effective area irradiated with light. This auxiliary electrode 30 extends onto the substrate along the tapered surface around the side of the semiconductor layer 12 and is connected in series to the first electrode of another conversion device 7 . The counter electrode of this photoelectric conversion device 7 also consists of a transparent electrode 11' and an auxiliary electrode 22.

Furthermore, this transparent electrode 11' and the auxiliary electrode overlap to constitute one electrode of the backflow prevention diode 8. The semiconductor layer 12 of this diode is made of the same material and has the same structure as the semiconductor layer of the converter 7. This is clear from the manufacturing process shown in FIG. 1B. This is because the same semiconductor layer 3
This is because it was obtained by selectively etching.

As described above, when the configuration of the present invention is such that the backflow prevention diode 8 is provided on the same plane at the same time as the photoelectric conversion devices 6 and 7, and no new process is required for manufacturing this diode. It is a characteristic of Also, the other electrode 1 of this diode
3 is a base metal 15 constituting the second bus line 9
and the electrode 18.

Although this drawing shows an example in which two converters are connected in series, the features of the present invention can be further utilized by creating a plurality of converters on the same board and arranging them in series or in parallel.

In addition, in the case of this embodiment, two electrodes with different heights sandwiching a semiconductor layer can be connected in the same plane configuration without introducing any new process, which is extremely simple and industrially possible. We were able to create a low-cost device.

Example 2 FIG. 2 shows another embodiment of the invention.

In this embodiment, light passes through the substrate side and is irradiated onto the semiconductor layer from below.

In FIG. 2A, an electrode 3 which is a part of the first electrode and also constitutes a part of the counter electrode is disposed on the substrate 1.
7, 37', and 37'' were selectively formed using the first mask.

Furthermore, a transparent electrode 4 and a semiconductor layer 3 are formed on the upper surface in the same manner as in the embodiment shown in FIG.
Figure B was obtained. In Figure 2C, there is a second
The electrodes 34, 34', 34'' were formed using the second mask.

Thereafter, the semiconductor layer 3 was selectively etched using this second electrode as a mask, and the transparent electrode 4 was further etched. Therefore, in this example as well, a self-aligned structure in which the semiconductor layer and the transparent electrode had approximately the same shape could be achieved.

Then, as in FIG. 1, the periphery of the semiconductor layer 3 was tapered to remove disconnections in the wiring.

FIG. 2D is a completed diagram of the apparatus of the present invention. The first bus line 5 and the second bus line 9 are provided on the transparent insulating substrate 1, and the photoelectric conversion devices 6 and 7 generate photovoltaic force in response to light irradiation through the substrate. A backflow prevention diode is provided at 8.

Around the 12, 12' sides of the semiconductor are insulators 35,
35', and lead 3 is placed on this insulator.
6 electrically connects the photoelectric conversion devices.

The counter electrodes are transparent electrodes 11, 11' and auxiliary electrodes 3 such as a grid line pattern or a cross line pattern.
7, 37', 37''...

Further, in this example, the substrate material used was a light-transmitting material, typically glass or transparent organic resin.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a photoelectric conversion device using the present invention having a configuration in which light is irradiated from above the substrate, and a manufacturing process thereof. FIG. 2 shows a longitudinal cross-sectional view of a photoelectric conversion device using the present invention having a configuration in which light is irradiated from below the substrate, and a manufacturing process thereof.

Claims (1)

[Scope of Claims] 1. A photovoltaic power generation device comprising a photoelectric conversion device having a non-single crystal semiconductor layer provided on an insulating substrate, and a backflow prevention diode connected to the photoelectric conversion device, The backflow prevention diode is provided on the insulating substrate with the same material and the same configuration as the non-single crystal semiconductor layer that constitutes the photoelectric conversion device, and the non-single crystal semiconductor layer that constitutes the photoelectric conversion device and the non-single crystal semiconductor layer that constitutes the A photovoltaic power generation device characterized in that a side periphery of a crystalline semiconductor layer is formed into a tapered trapezoid.