JPH0221668A - Amorphous silicon base photoelectromotive force element and manufacture thereof - Google Patents

Abstract

PURPOSE:To rapidly increase the directly hitting terminal values while eliminating any complicated manufacture devices and processes for facilitating the manufacture by a method wherein insulating films in specified volume resistivity and thickness are formed of oxide film, etc. CONSTITUTION:Insulating films 16 with volume resistivity of 10<2>-10<7>OMEGA.cm and thickness of 10-200Angstrom are formed on an amorphous silicon base semiconductor layer 14. The insulating films 16 are formed of oxide films comprising a metal more easily oxidized than silicon, etc., e.g., aluminum or aluminum alloy containing 80% or more aluminum to be deposited on the amorphous silicon base semiconductor layer 14 by evaporation, etc., in thickness of 10-200Angstrom and then the metal is heated in the temperature of 100-300 deg.C to be thermal-oxidized in the atmospheric air or in the atmosphere sealed with oxygen if necessary. Finally, rear side electrodes 18 are deposited opposingly to transparent electrodes 12 on the formed insulating films 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an amorphous silicon-based photovoltaic device and a method for manufacturing the same.

[Conventional technology and issues to be solved]

Amorphous silicon photovoltaic elements are placed on an insulating substrate.
A transparent electrode, an amorphous silicon-based semiconductor layer, and a back electrode are sequentially stacked. An amorphous silicon-based photovoltaic device is manufactured by using one amorphous silicon-based photovoltaic device or a plurality of amorphous silicon-based photovoltaic devices connected in series to obtain a high electromotive force.

Amorphous silicon photovoltaic devices are assembled as power supplies into electronic desk calculators, watches, etc., but the automatic assembly process may involve high voltage being applied to the amorphous silicon photovoltaic devices. be. Even in such a case, it is necessary to ensure that the amorphous silicon-based photovoltaic device (device) can operate normally. Therefore, we determined the voltage that an amorphous silicon-based photovoltaic device can withstand even if a certain voltage is applied to it, that is, the so-called terminal direct impact (electrostatic withstand voltage) value, for each manufacturer and nine types, and guaranteed this terminal direct impact value. Quality is maintained through these measures.

For a relatively small amorphous silicon-based photovoltaic device, the terminal direct impact value is measured by electricity that is charged to a predetermined voltage three times in the forward direction and in the reverse direction through a 200PF capacitor between the terminal electrodes. It is determined by investigating whether or not the amorphous silicon-based photovoltaic device can function normally after applying the voltage. To give an example of the terminal direct impact value, for example, the terminal direct impact value of an amorphous silicon photovoltaic device in which a back electrode is formed of a metal material having an ohmic contact on an amorphous silicon semiconductor layer is 100 to 150 V/. c+s". However, this terminal direct hit value was not large enough, and 3
It was desired to obtain a terminal direct impact value of 00 to 450 V/c+*''.

Conventionally, methods for improving the terminal direct impact value include eliminating defects such as pinholes that occur in the amorphous silicon semiconductor layer, and removing defects between the positive and negative electrodes that make up the amorphous silicon photovoltaic element. A method of imparting resistance or an amorphous silicon semiconductor layer
In the case of an in-type structure, a method of increasing the thickness of the iN film has been proposed. However, these methods require new steps in manufacturing and assembling amorphous silicon-based photovoltaic devices, and are therefore lacking in practicality and feasibility.

Moreover, when the present inventors conducted an experiment on a method of increasing the thickness of the i-layer, no significant improvement in the terminal direct impact value was observed.

Therefore, the inventors of the present invention conducted extensive research with the aim of dramatically improving the terminal direct impact value, and as a result, they arrived at the present invention.

[Means for Solving the Problems] The gist of the amorphous silicon-based photovoltaic device according to the present invention is that a transparent electrode, an amorphous silicon-based semiconductor layer, and a back electrode are sequentially stacked on an insulating substrate. In an amorphous silicon-based photovoltaic device consisting of
An insulating film having a volume resistivity of 10'' to 10 7 Ω·cm and a thickness of 10 to 200 Ω·cm is provided between the amorphous silicon semiconductor layer and the back electrode.

In particular, the insulating film is made of a metal oxide film that is more easily oxidized than silicon, and the insulating film is made of ohmink contact with amorphous silicon semiconductors such as chromium, alloys of aluminum and silver, silver titanium, nickel, and molybdenum. This is due to the use of an oxide film made of a metal material, a conductive resin, or a transparent insulating layer.

Furthermore, the gist of the method for manufacturing an amorphous silicon-based photovoltaic device according to the present invention is that a transparent electrode, an amorphous silicon-based semiconductor layer, and a back electrode are sequentially stacked on an insulating substrate to produce an amorphous silicon-based photovoltaic device. In a method for manufacturing an electromotive force element, a metal that is more easily oxidized than silicon is deposited to a thickness of 10 to 200 mm on an amorphous silicon-based semiconductor layer deposited on a transparent electrode, and then the deposited metal is deposited to a thickness of 10 to 200 mm. The metal is thermally oxidized at a temperature of 100 to 300° C. to form an oxide film, and then a back electrode is formed on the oxidized film.

[For production]

In the amorphous silicon photovoltaic device of the present invention, an insulating film is formed between the amorphous silicon semiconductor layer and the back electrode. However, the insulating film has a volume resistivity of 102 to 107 Ω·cam and a thickness of 10 to 200 Ω, and the carriers generated in the amorphous silicon semiconductor layer are insulated by the tunnel effect. Through the film, it is possible to function as an amorphous silicon-based photovoltaic element with almost no reduction in output. On the other hand, the presence of the insulating film protects the amorphous silicon-based semiconductor layer and improves the value of direct damage to the terminal, although the theoretical explanation is not sufficient for direct damage to the terminal due to high voltage.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings. Note that the drawings are shown enlarged as appropriate for the purpose of explanation.

In FIGS. 1(a) and 1(b), reference numeral 10 indicates an insulating substrate, and the insulating substrate 10 may be a transparent substrate such as glass or a polymer film, or an opaque substrate such as a metal foil with an insulating film on the surface, or a ceramic substrate. It is composed of a substrate, and may be flexible in addition to being rigid. Here, for the sake of explanation, a transparent substrate will be used as an example of the insulating substrate 10.

A plurality of transparent electrodes 12 are formed on the transparent substrate 10 by sputtering or the like. The transparent electrode 12 has an I.T.
O, 5nOt, ITO/Snow, or the like is used, and is formed into a predetermined pattern by photoetching, laser scribing, masking, or the like.

On the plurality of transparent electrodes 12 formed in a predetermined pattern, an amorphous silicon-based semiconductor [14] is deposited by an ion blasting method, a vacuum evaporation method, a plasma CVD method, a sputtering method, or the like. The amorphous silicon semiconductor layer 14 is made of, for example, amorphous silicon a-5i, hydrogenated amorphous silicon a-5i:
H, hydrogenated amorphous silicon carbide a-5iC
:If, amorphous silicon nitride, etc.
Amorphous or microcrystalline amorphous silicon-based semiconductors made of alloys of silicon Si and other elements such as carbon C, germanium Ge, and tin Sn are known as pin type, pn type,
It is deposited in a Mis-type heterozygous type, homozygous type, cykontoky barrier type, or a combination of these types.

On top of the amorphous silicon semiconductor layer 14 is a layer having a volume resistivity of 10'' to 10'Ω·C- and a thickness of 10
Insulation level II for ~200 people! 16 is formed. The insulating film 16 is made by depositing a metal that is more easily oxidized than silicon, such as aluminum or an aluminum alloy containing 80% or more of aluminum, on the amorphous silicon semiconductor layer 14 to a thickness of 10 to 200 nm using a vapor deposition method or the like. rear,
It is formed by an oxide film obtained by thermally oxidizing the metal by heating it to a temperature of 100 to 300° C. in the air or, if necessary, in an atmosphere containing oxygen.

The reason why a metal that is more easily oxidized than silicon is selected as the metal constituting the insulation degree @16 is because the amorphous silicon semiconductor layer 14 on which the metal is deposited is also heated, so that the metal is oxidized faster than the amorphous silicon is oxidized. This is to oxidize the deposited metal. Moreover, the reason why 100 to 300° C. is selected as the heating temperature is to prevent amorphous silicon from being denatured by heat.

The volume resistivity of the thus obtained oxidation degree 11116) is required to be 102 to 10'Ω·cl. Volume resistivity of insulation degree M (oxide film) 16 is 107Ω・cll
When it exceeds amorphous silicon semiconductor N14
The electrons generated in step 1 do not flow between the transparent electrode 12 and the back electrode described later, and the amorphous silicon-based photovoltaic device is no longer able to function. On the other hand, when the volume resistivity of the insulating film (oxide film) 16 is less than 102Ω/0 ring, the externally applied current flows freely without resistance, so it cannot contribute in any way to improving the terminal direct impact value. .

A back electrode 18 is deposited on top of which the insulation level #16 is formed so as to face the transparent electrode 12. The back electrode 18 is made of aluminum, aluminum containing silver,
There are those that are formed by applying a coating film such as chromium by vapor deposition or sputtering and then molded by laser scribing or photo-etching, or those that are formed by screen printing a metal paste made by kneading metal powder such as nickel into resin. It is formed from a film obtained by

In this way, the transparent electrode 12. Amorphous silicon-based semiconductor layer 14. Insulating film (oxide film) 16 and back electrode 18
are laminated to form an amorphous silicon-based photovoltaic element 20.
is configured. Further, an amorphous silicon-based photovoltaic device 22 is configured by connecting one amorphous silicon-based photovoltaic device 20 or a plurality of amorphous silicon-based photovoltaic devices 20 in series to obtain the necessary electromotive force. In this example, four amorphous silicon-based photovoltaic devices 20 are connected in series by connection electrodes 24 to form an amorphous silicon-based photovoltaic device 22.
is configured.

A MOS (Metal
When light is irradiated onto the amorphous silicon photovoltaic element 20 having the 0xide semiconductor structure, carriers generated in the amorphous silicon semiconductor layer 14 pass through the oxide film 16 by a tunnel effect, and are connected to the transparent electrode 12 and the back electrode. A current flows between the photovoltaic device 18 and the device functions as a photovoltaic device.

In addition, the obtained amorphous silicon-based photovoltaic device 2
An experiment was conducted to determine the terminal direct hit value by applying various voltages three times each in the forward direction and the reverse direction between the two terminals 26 through a 200 PF capacitor. As a result, the terminal direct impact value was improved by about twice to more than that of a conventional amorphous silicon-based photovoltaic device (device) in which no oxide film was formed. In addition, as the voltage, which is the direct impact value on the terminals, is increased, the function as an amorphous silicon photovoltaic element does not deteriorate suddenly, but gradually (a trend is shown). The deterioration in the function of the power device was noticeable with respect to the open circuit voltage, and there was almost no change in the short circuit current.

Although the theoretical elucidation of such a phenomenon is not sufficient, it is believed that by providing a barrier between the amorphous silicon semiconductor J114 and the back electrode 18 (at the interface) by the oxide film 16, the diffusion of charges (ions) is delayed. This is thought to be due to

Next, after observing the state of the oxide film 16 deposited on the amorphous silicon semiconductor layer 14, the back electrode 18 was deposited on the resulting amorphous silicon photovoltaic device 22. The terminal direct hit value was investigated. As a result, it was found that if the oxide film 16 was not formed over the entire surface of the amorphous silicon semiconductor layer 14 and there was an exposed portion of the amorphous silicon semiconductor layer 14, the terminal direct impact value would hardly improve. This is understood to be because carriers flow freely in the exposed portion of the amorphous silicon semiconductor layer 14, so that the oxide film 16 does not function as a ¥iJ wall.

Although the embodiments of the present invention have been described in detail above, the present invention can be implemented in other embodiments as well.

For example, on the upper side, aluminum or an aluminum alloy is used as a metal that is more easily oxidized than silicon, and its oxide film is used as an insulating film, but other materials that make up the insulating film include alloys of chromium aluminum and silver, silver, titanium, Enkel. A metal material that forms an ohmic contact with an amorphous silicon-based semiconductor such as molybdenum is also suitable. Among these metal materials, titanium, nickel, molybdenum, etc. are metals that are more difficult to oxidize than silicon, but they form stable compounds at the interface with silicon, making them suitable for amorphous silicon-based photovoltaic materials with stable quality. A power element is obtained. In this example as well, after the metal material constituting the ohmink contact is deposited to a thickness of 10 to 200 layers on the upper surface of the amorphous silicon semiconductor layer, it is thermally oxidized at a temperature of 100 to 300 degrees Celsius, and then further deposited on the back surface. Electrodes will be deposited.

According to this example, an alloy layer is formed by ohmink junction at the interface between the amorphous silicon semiconductor layer and the metal film layer with ohmic contact, and on the other hand, a metal film is formed at the interface between the metal film layer and the back electrode. An oxide film is formed in which the layer is thermally oxidized. Therefore, not only the terminal direct impact value is improved, but also the performance as an amorphous silicon photovoltaic element is improved.

Further, the amorphous silicon-based photovoltaic element according to the present invention has a volume resistivity of 10'' to 107 Ω·cII due to a metal oxide film that is more easily oxidized than silicon between the amorphous silicon-based semiconductor layer and the back electrode. The purpose is to form an insulating film with a thickness of 10 to 200 mm, but such an oxide film, that is, a volume resistivity of 10 to 10 that can function equivalently to an insulating film.
7Ω・Cl11 conductive resin or transparent insulator 10-2
According to this example, it is possible to form an insulating film to a film thickness of 0.00 mm by coating, LB film (Langmuir-Progent film), etc., and there is an advantage that thermal oxidation is not necessary.

Further, the method for integrating an amorphous silicon photovoltaic device according to the present invention is not limited to the type shown in FIG. 1, but may be, for example, the type shown in FIG. 2. In this example, after the amorphous silicon semiconductor layer 32 is laminated and deposited so as to cover the plurality of transparent electrodes 30 formed on the transparent substrate 28, an oxide film of a metal that is more easily oxidized than silicon is further deposited. After that, the amorphous silicon semiconductor layer 32 and the insulating film 34 are scribed into a predetermined shape using a laser or the like, and then a plurality of back electrodes 36 are applied.

In the above embodiments, a transparent substrate was used as the insulating substrate, but the present invention can also be suitably applied to an opaque substrate. In this example, after forming a back electrode on an opaque substrate, an insulating film such as a metal oxide film is formed on the back electrode, and then,
An amorphous silicon semiconductor layer and a transparent electrode are laminated and deposited on the insulating film. The oxide film in this example does not necessarily need to be made of a metal that is more easily oxidized than silicon (and the temperature for thermal oxidation is also 10
It is not limited to 0-300'C.

In addition, the oxide film may be formed not only by heat but also by chemical treatment, and the present invention is based on the knowledge of those skilled in the art without departing from the spirit of the invention. It can be implemented in the form a with various modifications, improvements, and modifications.

After depositing 800 layers of SnO2 as transparent electrodes on the upper glass substrate, 9 layers of amorphous silicon-based semiconductor layers were formed.
The i-layer and the n-layer were deposited in this order. Next, 150% aluminum ^1 was deposited on the n-layer of the amorphous silicon semiconductor layer.
After evaporation to a thickness of 50°C, the deposited aluminum film was thermally oxidized in the air at 150°C for 15 minutes to obtain an oxide film of aluminum oxide l, 81□O:I. . Aluminum was deposited as a back electrode on the aluminum oxide A1.03 film and covered by 1000 people. The model of the amorphous silicon-based photovoltaic device obtained was 5C5513AS (manufactured by Kanekabuchi Kagaku Kogyo fil).

A 200 pF capacitor was charged to a predetermined voltage in the forward and reverse directions, and the voltage was applied to the terminal of the obtained amorphous silicon photovoltaic device for three times.
The terminal direct hit value test was repeated several times.

For the sample to which a voltage of a predetermined terminal surface ml value was applied, F
1 for the open circuit voltage (V) and operating current in L1501ux
．． 5V) (μΔ). As a result, at least 5
It has been proven that it can withstand a terminal direct impact value of 00■. The relationship with open circuit voltage is shown in Table 1, and the relationship with operating current is shown in Table 2 as average values for 15 samples.

Disaster application-1 In the same manner as in Example 1, a transparent electrode, an amorphous silicon semiconductor layer, and an aluminum oxide film were laminated and deposited on a glass substrate, and then chromium Cr was deposited as a back electrode.
was deposited and 1,000 people arrived.

The obtained amorphous silicon-based photovoltaic device was subjected to the same test as in Example 1, and then the open circuit voltage and operating current were examined. As a result, it was proven that it could withstand a terminal direct impact value of at least 500μ. The relationship between open circuit voltage and operating current is shown in Tables 1 and 2, respectively.

Comparison 5 - After depositing a transparent electrode and an amorphous silicon semiconductor layer on a glass substrate in the same manner as in Example 1, a layer containing 1% silver was deposited on the amorphous silicon semiconductor layer as a back electrode. A total of 1,000 people were coated with aluminum alloy (AI/8g to χ).

The obtained amorphous silicon-based photovoltaic device was subjected to the same test as in Example 1, and then the open circuit voltage and operating current were examined. As a result, it was proven that it could withstand a terminal direct impact value of 150 μm, but both the open circuit voltage and operating current were significantly reduced, making it unsuitable for use as an amorphous silicon-based photovoltaic device. The relationship between open circuit voltage and operating current is shown in Tables 1 and 2, respectively.

Comparison 1-I After depositing a transparent electrode and an amorphous silicon semiconductor layer on a glass substrate in the same manner as in Example 1, a layer containing 7% silver was deposited on the amorphous silicon semiconductor layer as a back electrode. An aluminum alloy (^l/^g7χ) was vapor-deposited and 1000 people arrived.

The obtained amorphous silicon-based photovoltaic device was subjected to the same test as in Example 1, and then the open circuit voltage and operating current were examined. As a result, it was proven that it could withstand a terminal direct impact value of 250 cm. The relationship between open circuit voltage and operating current is shown in Tables 1 and 2, respectively.

(Blank below) [Effects of the Invention] According to the amorphous silicon-based photovoltaic device according to the present invention, the volume resistivity between the amorphous silicon-based semiconductor layer and the back electrode is 10'' to 10 7 Ω·cm, Moreover, since the insulating film with a thickness of 10 to 200 mm is formed of an oxide film, etc., the terminal direct impact value can be dramatically improved without sacrificing the function as an amorphous silicon photovoltaic element. In addition, due to the dramatic improvement in the terminal direct impact value, it is possible to prevent the occurrence of defects in amorphous silicon photovoltaic devices later when they are assembled into various devices. The reliability of power equipment will be improved.

Furthermore, the present invention has the advantage that the device and the method for manufacturing the same do not require complicated manufacturing equipment or processes and can be easily manufactured.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are diagrams for explaining an amorphous silicon-based photovoltaic device constructed from an amorphous silicon-based photovoltaic element according to the present invention;
is a plan view, and FIG. 3(b) is a front sectional view. FIG. 2 is a front sectional view showing an amorphous silicon photovoltaic device which is another embodiment of the amorphous silicon photovoltaic device according to the present invention. 10.28; Insulating substrate 12.30; Transparent electrode 14.32. Amorphous silicon semiconductor layer 16.3
4. Insulating film 18.36. Back electrode 20; Amorphous silicon photovoltaic device 22; Amorphous silicon photovoltaic device Patent applicant Kanekabuchi Chemical Co., Ltd.

Claims (8)

[Claims] (1) In an amorphous silicon-based photovoltaic element in which a transparent electrode, an amorphous silicon-based semiconductor layer, and a back electrode are sequentially stacked on an insulating substrate, between the amorphous silicon-based semiconductor layer and the back electrode, The volume resistivity is 10^2 to 10^7 cm,
An amorphous silicon-based photovoltaic device characterized by having an insulating film having a thickness of 10 to 200 Å. (2) An amorphous silicon-based photovoltaic device, wherein the insulating film according to claim 1 is an oxide film of a metal that is more easily oxidized than silicon. (3) An amorphous silicon-based photovoltaic device, wherein the metal that is more easily oxidized than silicon according to claim 2 is aluminum or an aluminum alloy containing 80% or more of aluminum. (4) The insulating film according to claim 1 is an oxide film made of a metal material that forms an ohmic contact with an amorphous silicon semiconductor such as chromium, an alloy of aluminum and silver, silver, titanium, nickel, or molybdenum. An amorphous silicon-based photovoltaic device characterized by: (5) An amorphous silicon-based photovoltaic device, wherein the insulating film according to claim 1 is a conductive resin. (6) An amorphous silicon-based photovoltaic device, wherein the insulating film according to claim 1 is a transparent insulating layer. (7) Claim 1, 2, 4, 5 or 6
An amorphous silicon-based photovoltaic device, characterized in that the insulating film according to item 1 is formed on the entire surface of an amorphous silicon-based semiconductor layer. (8) In a method for manufacturing an amorphous silicon-based photovoltaic device by sequentially stacking a transparent electrode, an amorphous silicon-based semiconductor layer, and a back electrode on an insulating substrate, the amorphous silicon-based semiconductor layer deposited on the transparent electrode 10-20% of metal, which is more easily oxidized than silicon, is placed on the semiconductor layer.
After being deposited to a thickness of 0 Å, the deposited metal is
1. A method for manufacturing an amorphous silicon photovoltaic device, comprising forming an oxide film by thermal oxidation at a temperature of 300° C., and then forming a back electrode on the oxide film.