JPS60101979A - Photovoltaic element - Google Patents

Abstract

PURPOSE:To improve photoelectric conversion efficiency by connecting amorphous Si thin-films in a multilayer shape while mixing crystallite Si to the amorphous Si thin-film most separate from the beam incident side. CONSTITUTION:A transparent electrode 200 is formed on a glass substrate 100. P type, I-type and N type each semiconductor layer 300A, 400A and 500A consisting of amorphous Si are shaped on the electrode 200 in succession, thus forming a first Si thin-films A. P type, I-type and N type each semiconductor layer 300B, 400B and 500B composed of amorphous Si are formed on the layer 500A. Crystallite Si is mixed to each of these layers 300B, 400B and 500B, thus forming second Si thin-films B. Accordingly, the absorption wavelength range of solar rays can be increased, and photoelectric conversion efficiency can be improved largely.

Description

[Detailed Description of the Invention] The present invention relates to a photovoltaic device that performs photoelectric conversion using a silicon thin film grown on a substrate, and particularly aims to significantly improve the photoelectric conversion efficiency by increasing the efficiency of using incident light. That is.

In general, photovoltaic elements, which refer to solar cells made of silicon, are mainly crystalline (single crystal, multi-crystalline, and amorphous elements). Visible light and wavelengths longer than the visible light contribute to power generation, while amorphous photovoltaic elements mainly absorb energy in the shorter wavelength region, i.e. in the visible light, compared to the absorption wavelength of the crystalline type. It is known that glass contributes the most to power generation. Figure 1 is a conceptual cross-sectional view showing the structure of a conventional cell-like amorphous photovoltaic device using glass as a substrate. The substrate, 2 is a transparent conductive film, 3 is an amorphous P-type semiconductor layer, 4 and 5 are amorphous ■-type and N-type semiconductor layers. semiconductor layer 314
+5 are stacked. Further, on the upper surface of the N-type semiconductor layer 5, an opaque metal electrode 6 such as a vapor-deposited film of aluminum is deposited to form a photovoltaic element. Since the semiconductor layer of such a photovoltaic element is amorphous, it has a total thickness of 2000 to 6000 A in consideration of light absorption and electron diffusion distance, and the photoelectric conversion of this photovoltaic element The efficiency remains at 2 to 6%, and even in the case of a hetero type in which silicon carbide (SiC) is mixed in the l' type conductor layer, the current limit is about 7 to 8%. In addition, the wavelength range of light in which this pre-originated zh force element contributes to power generation is
Most of the light is in the visible light range, which matches the wavelength of the light emitted by fluorescent lamps, making it suitable as a power source for desk-top computers and the like that use indoor lighting. Therefore, as a photovoltaic element that performs photoelectric conversion using sunlight having a wide wavelength range, it is not possible to perform effective photoelectric conversion using light within a partial wavelength range of sunlight.

Therefore, in order to solve the above-mentioned problems, a forward cell tandem type photovoltaic device in which silicon thin films for photoelectric conversion are double-connected as shown in FIG. 2 has been proposed. FIG. 2 is a conceptual cross-sectional view showing the structure of a III cell tandem type photovoltaic device using glass as a substrate, where 10 is a glass substrate, 2° is a transparent conductive film, and 30, 40.50 are amorphous. a first P, I, N type semiconductor layer made of silicon, 31.41
．． 51 is higher energy/L/−f than the first semiconductor layer.
- a second P made of amorphous germanium or the like with a narrow cap; 1. The N-type semiconductor layer 60 is a metal electrode, and these constitute a forward cell tandem photovoltaic device. This tandem type photovoltaic element is made to be able to absorb light in the short wavelength visible light range by P, I, and N type semiconductor layers 30, 40, and 50, and another P, I type semiconductor layer 30, 40, and 50.

The N-type semiconductor layers 31, 41, 51 can absorb light with a longer wavelength than is absorbed by the first semiconductor layer, and the incident light in the visible light range is converted into P, I, N)-
(+J semiconductor layer 30, 40.50 and 31.41+51
It absorbs light over a wide wavelength range, greatly increasing photoelectric conversion efficiency. However, this type of tandem photovoltaic device uses materials other than silicon, such as germanium, tin, etc., as the main component to produce the thin film.
! It is necessary to use a special gas in combination with a thin film generating device or 41.1. In addition, these special gases are dangerous in terms of health and safety, are not easy to handle, and are extremely expensive, which poses some practical problems.

In view of the above-mentioned problems, the present invention combines amorphous silicon thin films for photoelectric conversion in multiple ways and mixes microcrystalline silicon in the amorphous silicon thin film furthest from the light incident side, thereby reducing incident light. The present invention proposes a photovoltaic element that can significantly improve photoelectric conversion efficiency by absorbing light over a wide wavelength range.

The present invention will be described in detail below with reference to embodiments shown in the drawings.

FIG. 3 is a conceptual cross-sectional view showing the structure of a photovoltaic device according to the present invention. In FIG. 3, 100 is a substrate made of glass, 200 is a transparent conductive film formed on the top surface of the substrate 100, 300A is a P-type semiconductor layer made of amorphous silicon formed on the top surface of the transparent conductive film 200, 400A is a J-type conductor made of amorphous silicon formed on the top surface of the P-type soil conductor layer 300A. 1.500A is made of amorphous silicon formed on the top surface of the I-type semiconductor layer 400A It is an N-type semiconductor layer, and a P-type layer in which these are stacked,
I-type and N-type semiconductor layers 300A, 400. A, a first silicon thin film A to be photoelectrically converted is formed at 500A. 300B is a 1″21 layer made of amorphous silicon formed on the surface of the N-type semiconductor layer of the first semiconductor layer A.
'421'4 semiconductor 0B is a type 1 semiconductor layer made of amorphous silicon formed on the upper surface of the P-type semiconductor layer 300B;
500B is made of amorphous silicon formed on two surfaces of the l-type semiconductor layer 400Is. This is a KJ semiconductor layer. Each of these laminated P-type, I-type, and N-type semiconductor layers 300B, 4001S, and 500B has a grain size of about 20 to 30oX and contains microcrystalline silicon in a volume ratio of 5 to 98%. A second silicon thin film B to be photoelectrically converted is formed. Reference numeral 600 denotes an opaque metal electrode in which aluminum is deposited on the upper surface of the second silicon thin film BON type conductor layer 50 (lB), and these constitute the photovoltaic element according to the present invention.

The first and second silicon thin films described above are produced by a known plasma CVD method.

First, a substrate 100 made of a glass plate is placed in a vapor deposition apparatus (not shown), and an ITO film, which is an oxide of indium and tin, is vapor-deposited on the substrate loo using an electron beam to form a transparent conductive film 2.
00 is formed.

Subsequently, the substrate 100 is taken out of the vapor deposition apparatus and placed in a vacuum container (not shown) in which a thin film is generated by glow discharge, and a high voltage is applied to a predetermined gas supplied into the vacuum container to cause glow discharge. L type and N type are formed on the conductive film 200.

N-type semiconductor layers 300A, 40OA, and 500A are sequentially generated to form a first silicon thin film A. To generate the P-type semiconductor layer 300A and the N-type semiconductor l-, diborane (B2I-16) is added to monosilane (S+LI4), respectively.
Alternatively, monosilane (Sil-I4) can be used to form an N-type semiconductor layer by adding phosphine (1)■I3).
) is used. The first silicon thin film A produced in this manner is capable of absorbing visible light in the short wavelength range of sunlight well over a wide range.

On the other hand, the second silicon thin film B containing microcrystalline silicon is formed on the substrate 10 while being formed on the first silicon thin film.
0 is placed in a vacuum container and the first silicon thin film B is formed, P,
Each semiconductor layer of .degree.N is generated. For example 13.56MH
When high-frequency air pressure of z was applied to the discharge electrode, the first silicon thin film A was generated with a power of 20 W, whereas monosilane gas was diluted with hydrogen gas and the power was gradually increased to 100 W. By producing each of the semiconductor layers described above, a state in which microcrystalline silicon with a grain size of 60 to 70 A is mixed in each semiconductor layer is obtained, and a P-type silicon film is formed on the first silicon thin film A.

■ type and N type semiconductor layers 300B, 400B
.

500B is sequentially produced to produce the second silicon thin film B. In addition, P type, ■ type, and N type semiconductor layers 300B
, 400B, and 500B, each semiconductor layer 300A of the first silicon thin film A.

Monosilane (
A large amount of hydrogen gas (H2) is added to dilute the H2+114). Further, the proportion of microcrystalline silicon can be mixed at a predetermined level by appropriately selecting the thin film formation time. The second silicon thin film B mixed with microcrystalline silicon produced in this way can absorb long-wavelength light near the infrared region of sunlight well over a wide range. Furthermore, due to the presence of microcrystalline silicon, the light reflected by the metal electrode can easily pass through this thin film, so that the reflected light is absorbed again by the silicon thin film containing microcrystalline silicon and can contribute to power generation. Furthermore, the presence of microcrystalline silicon reduces the internal resistance of this silicon thin film, thereby reducing power loss inside the thin film.

In this way, due to the light absorption wavelength range of the first silicon thin film and the light absorption wavelength range of the second silicon thin film B,
The conventional narrow light absorption wavelength range can be significantly increased, and synergistic effects such as reduction in internal resistance and reabsorption of reflected light can be obtained, and the photovoltaic device according to the present invention has a higher photoelectric conversion efficiency than the conventional one. This can be increased from 6% of an amorphous silicon photovoltaic element to about 9%.

According to this example, monosilane was diluted with hydrogen gas to generate microcrystalline silicon, so microcrystalline silicon contains hydrogen, but microcrystalline silicon contains other halogen elements such as fluorine. can also be used. In addition, microcrystalline silicon was mixed throughout the silicon film that was farthest from the light incident side, but at least one part of the thin film was mixed.
They may be mixed in one conductor layer.

Historically, the substrate is limited to a glass plate; however, a metal plate such as stainless steel can be used, and the same effect as when using a glass plate can be obtained.

Historically, the connection of silicon 1ilj films is not limited to only double connections.

Although the structure of the thin film in this embodiment is of a similar type, it is of course possible to use a reverse type.

As described in detail above, the photovoltaic device of the present invention comprises a silicon 1 semiconductor layer made of amorphous silicon for photoelectric conversion.
By multiplexing the J17 films and mixing microcrystalline silicon in at least one semiconductor layer of the silicon thin film furthest from the light incident side, it is possible to increase the absorption wavelength range of sunlight. In addition, the incident sunlight is reflected by the metal electrode provided on the side opposite to the light incident side, and the sunlight that re-enters the silicon film mixed with microcrystalline silicon is absorbed again, completely absorbing the incident sunlight. Photoelectric conversion can be performed. Furthermore, by mixing microcrystalline silicon, the electrical resistance of the silicon thin film can be lowered.

Therefore, it is possible to significantly increase the photoelectric conversion efficiency of incident sunlight, and the silicon thin film mixed with microcrystalline silicon can reduce internal power loss, and this function also increases the photoelectric conversion efficiency. can be increased. Furthermore, there are safety and health issues during manufacturing.
Since the plasma CVD method is used without using special gases, photovoltaic elements can be produced safely and at low cost, which would otherwise require major modification of production equipment, making it a great contribution to industry.

[Brief explanation of the drawing]

1 and 2 are conceptual 1 (11) views showing the structure of a conventional photovoltaic device, and FIG. 3 is a conceptual sectional view showing a 4114 structure of a photovoltaic device according to the present invention. 1.10,100...Substrate 2,20,200・
...Transparent conductive film 3,30,31.30OA. 300B...P-type semiconductor layer 4.40.41°40O
A, 40013... [type semiconductor layer 5.50°51.
500Δ, 500B...N-type semiconductor layer 6.・60
, 600...Metal electrode A...First silicon thin film 11...Second silicon thin film Agent Patent attorney Hiroshi Chugai 1st floor] Tadashi Neyama in front of 2nd figure 8;! , : (spontaneous) 1. Indication of slight heat 1982 Patent Application No. 209639D 2. Name of the invention Photovoltaic element 3. Persons making amendments 1!1 Which relationship Patent applicant 1-1, 1111112-chome, Yodoyo-ku, Osaka City゛1shi] (02
G) Osaka Transformer Co., Ltd. 1 4, Agent 1.1 Address: 0.11112-111i, Yodoyo-ku, Osaka 532, 5, Subject of amendment Detailed explanation of the invention of Sekiro) , ? +li il- contents detailed audience as follows Δ]' IT-5. (1) Page 10, No. 1! :+ 1-C funnel of f-j. ''s ゛) In [J's 1st Sirini 1st Expo II! III
△ and the second series': ] N thin 11! 413 is attached to the cotton culm surface through the metal 01) oxide 10 (t) J-. ” is added. that's all

Claims (1)

[Claims] 1. Silicon thin films made of amorphous silicon semiconductor layers for photoelectric conversion are multiple-connected, and microcrystalline silicon is mixed in at least one semiconductor layer of the silicon polishing film furthest from the light incident side. Photovoltaic element.