JPH0613639A - Photovoltaic device - Google Patents

Abstract

PURPOSE:To suppress carrier recombination created in a boundary between insulating amorphous material which passivates crystalline silicon and the crystalline silicon. CONSTITUTION:Amorphous silicon layers (4) and (7) are provided in the boundaries between crystalline silicon layers (1) and (2) and insulating amorphous material layers (3) and (6).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a photovoltaic device for converting light energy into electric energy.

[0002]

2. Description of the Related Art Conventionally, so-called passivation has been carried out in a photovoltaic device, in order to stabilize element characteristics, that a semiconductor material constituting the photovoltaic device is covered with an insulating film. Usually, the insulating film used for this passivation is called a passivation film.

FIG. 3 is a diagram showing the element structure of a conventional photovoltaic device. In the figure, (31) is p-type polycrystalline silicon, (32) is p
N-type polycrystalline silicon exhibiting a photoelectric conversion function by being joined to the n-type polycrystalline silicon (31), and (33) made of a metal material formed on the n-type polycrystalline silicon (32). Collector electrode, (34) a back electrode deposited on the p-type polycrystalline silicon (31), and (35) covering the collector electrode (33) on the surface of the n-type polycrystalline silicon (32). An insulating amorphous material made of silicon nitride, amorphous silicon carbide, silicon oxide, or the like coated as described above is a passivation film.

By forming such a passivation film, it is possible to prevent the surface of the n-type polycrystalline silicon (32), which is the main constituent material of the photovoltaic device, from being exposed to the atmosphere. This can suppress surface recombination of carriers caused by exposure of the surface to the atmosphere.

[0005] As a document relating to a photovoltaic device provided with such an insulating amorphous material, for example, "Conference r
ecord of the 21st IEEE PVSC (1990) p.678-680 ”.

[0006]

However, even if the insulating amorphous material (35) is used as the passivation film in the first place as in the conventional photovoltaic device, the insulating amorphous material itself is covered. Since it has a crystal structure different from that of polycrystalline or single crystal silicon (hereinafter referred to as crystalline silicon), that is, a so-called random crystal structure, its insulating amorphous structure is based on the difference in the crystal structure. Carrier recombination will occur at the interface between the quality material (35) and silicon (32).

In particular, in the case where the carriers lost by recombination are carriers generated by light, the loss due to recombination reduces the amount of external extraction as photocurrent, resulting in a decrease in photoelectric conversion efficiency. Will be invited.

[0008]

The photovoltaic device of the present invention is characterized in that the amorphous silicon is formed at the interface between crystalline silicon having a semiconductor junction exhibiting a photoelectric conversion function and an insulating amorphous material. And has a semiconductor junction having a photoelectric conversion function, which is composed of crystalline silicon of one conductivity type, intrinsic amorphous silicon, and amorphous silicon of another conductivity type. In a power device, a laminated body made of amorphous silicon and an insulating amorphous material is inserted at a part of the interface between the one conductivity type crystalline silicon and the intrinsic amorphous silicon. Especially.

[0009]

According to the photovoltaic device of the present invention, the recombination of carriers at the interface can be reduced by inserting the amorphous silicon at the interface between the insulating amorphous material and the crystalline silicon. .

This is because the conventional insulating amorphous material and crystalline silicon have large gaps in their respective lattice constants, and if they are brought into direct contact with each other, many carrier recombination occurs at the interface. The center will be generated,
Even if a large amount of photogenerated carriers are generated in this crystalline silicon, the recombination centers thereof cause the disappearance of many photogenerated carriers.

On the other hand, in the photovoltaic device of the present invention, amorphous silicon having a lattice constant relatively close to both of the insulating amorphous material and crystalline silicon is used as the contact interface between them. It is possible to dramatically suppress the carrier recombination by inserting the carrier into the carrier.

In the photovoltaic device of the present invention, the amorphous silicon and the insulating amorphous material are laminated on a part of the interface between the one conductivity type crystalline silicon and the intrinsic amorphous silicon. By inserting the body, the insulating amorphous material functions as a passivation film for the one-conductivity-type crystalline silicon, and the amorphous silicon is separated from the intrinsic amorphous silicon and insulating amorphous. It plays the role of reducing carrier recombination between quality materials.

In particular, by inserting the laminated body at the interface, it is possible to reduce the forward current, which is a characteristic of the diode, that is potentially possessed even by the photovoltaic device.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a device structure diagram of a first embodiment of a photovoltaic device of the present invention. In the figure, (1) is p-type polycrystalline silicon, (2) is n-type polycrystalline silicon that exhibits a photoelectric conversion function by a semiconductor junction with this p-type polycrystalline silicon (1),
(3) is an insulating amorphous material that functions as a passivation film made of amorphous silicon carbide (film thickness of about 700Å), and (4) is intrinsic amorphous silicon (film thickness of about 50Å) which is a feature of the present invention. ) Is inserted at the interface between the insulating amorphous material (3) and the n-type polycrystalline silicon (2). Reference numeral (5) is a collector electrode made of a metal material containing silver as a main component, which is provided in the openings of the amorphous silicon (4) and the insulating amorphous material (3). In this embodiment, the light from the collecting electrode (5) side is used, but the back surface side also uses the amorphous silicon which is a feature of the present invention.

That is, (6) is an insulating amorphous material that passivates the back surface of this photovoltaic device, and an amorphous silicon carbide (film) of the same material as the insulating amorphous material (3) on the light incident side. The thickness is about 700Å). (7) is a feature of the present invention for improving the interface between the insulating amorphous material (6) and the p-type polycrystalline silicon (1). , (8) are collector electrodes to be the back electrodes.

In particular, in the photovoltaic device of the embodiment, the amorphous silicon (4) (7) for improving the interface was used at two places, but it was used only at one place on the light incident side. Is also effective. However, as an effect of reducing carrier recombination, it is preferable to dispose them at both of these two locations. Table 1 shows the respective conditions for forming the amorphous silicon (4) (7) and the insulating amorphous material (3) (6) which are the features of the present invention.

[0017]

[Table 1]

In the above photovoltaic device, since the light from the collector electrode (5) side is used, the p-type polycrystalline silicon (1) having a photoelectric conversion function is irradiated with light. It is necessary to make it sufficiently incident. However, since the amorphous silicon material used in the photovoltaic device of the present invention usually has light absorption characteristics, this amorphous silicon (4)
In the case of arranging on the light incident side, it is necessary to make the film thickness sufficiently small to suppress the light absorption as much as possible. Therefore, in the photovoltaic device of the above embodiment, this amorphous silicon is used.
The thickness of (4) is reduced to about 50Å.

[0019]

[Table 2]

Table 2 is a comparison of the characteristics of the photovoltaic device of the present invention and the conventional photovoltaic device. (A) in the table is a photovoltaic device without any passivation,
(b) is a conventional photovoltaic device described above, which is a photovoltaic device in which silicon nitride is directly formed as a passivation film on the surface of polycrystalline silicon, and (c) is the photovoltaic device of the above embodiment, Each one is shown.

Since the photovoltaic device (b) is provided with a passivation film, the photoelectric conversion efficiency is improved from 9.0% to 12.0% as compared with the device (a).
In case of (c), it is improved to 12.6% more than that of the device (b). In particular, in the photovoltaic device (c) of the present invention, since the open circuit voltage is increased from 0.58 V to 0.59 V, carrier recombination, which is the effect of the present invention, can be reduced. I understand.

FIG. 2 is an element structure diagram of the second embodiment of the photovoltaic device of the present invention. The basic difference of the photovoltaic device of this embodiment from the photovoltaic device of the first embodiment is that a BSF (Back Surface F
That is, one of the semiconductors is made of polycrystalline silicon of one conductivity type and the other is made of amorphous silicon of the other conductivity type as a pn junction having a photoelectric conversion function.

Reference numeral (21) in the figure denotes n-type polycrystalline silicon (thickness 100 μm to 20 μm) which has a photoelectric conversion function of the present photovoltaic device.
0 μm), (22) is p-type amorphous silicon (thickness of about 500 Å) that forms a pn junction that performs photoelectric conversion with the n-type polycrystalline silicon (21), and (23) has the above BSF structure. , N-type amorphous silicon (film thickness of about 50Å) formed on the n-type polycrystalline silicon (21), (24) is made of indium tin oxide or tin oxide, which will be the electrode on the light incident side. Front electrode made of transparent conductive film (film thickness about 700Å), (25) is front electrode (24)
(26) is a collector electrode made of a metal paste or the like that complements the collection of photo-generated carriers in (26) is an amorphous silicon (thickness of about 50Å) that constitutes a part of the laminate, which is a feature of the present invention Is an insulating amorphous material (film thickness of about 700 Å) made of amorphous silicon carbide that functions as passivation, and constitutes the above-mentioned laminated body together with the amorphous silicon (27). (28) is a back electrode made of a metal material such as aluminum, and (29) is intrinsic amorphous silicon (film thickness: about 50Å).

In particular, in the photovoltaic device of this embodiment, the intrinsic amorphous silicon (29) has a good interface between the amorphous silicon (22) (23) and the polycrystalline silicon (21). It is provided to do so. Therefore, the n-type polycrystalline silicon in this example is
The (21) and the p-type amorphous silicon (22) form a pn junction having a photoelectric conversion function, that is, a semiconductor junction through the amorphous silicon (29).

Further, in the photovoltaic device of this example, holes are mainly p-type amorphous silicon (22) among the photo-generated carriers that are mainly absorbed by the polycrystalline silicon (21) and are generated by this.
One electron is taken out from the collecting electrode (25) through the n-type amorphous silicon (23) and the front electrode (24).

The feature of the photovoltaic device of this embodiment is that the n-type polycrystalline silicon (21) and the p-type amorphous silicon (21) that form a pn junction through the amorphous silicon (29). (twenty two)
Between the insulating amorphous material (27) and the amorphous silicon (26) which function as passivation. Even with such a structure, it is possible to insert the amorphous silicon (26), which is a feature of the present invention, between the insulating amorphous material (27) having a different crystal structure and the polycrystalline silicon (21). Therefore, it is possible to suppress the recombination of carriers.

In the photovoltaic device of this embodiment, the photo-generated carrier is generated only through the opening (30) of the laminated body composed of the insulating amorphous material (27) and the amorphous silicon (26). Therefore, the characteristics of the photovoltaic device fluctuate depending on the extent of the occupied area where the laminated body and the polycrystalline silicon (21) with which the laminated body comes into contact are in contact with each other.

That is, in the photovoltaic device of the present embodiment, although the effect of reducing carrier recombination can be obtained by inserting the amorphous silicon (26) constituting this laminated body, the occupied area is halfway. The larger the area, the smaller the path for taking out photogenerated carriers to the outside. Therefore, it is necessary to consider the occupied area.

[0029]

[Table 3]

Table 3 shows the characteristics of the photovoltaic device of this example and the photovoltaic device of the conventional example. Here, the conventional example device (a) does not have a passivation film on its surface, and is not affected by the above-mentioned occupied area of the laminate. On the other hand, in the photovoltaic device (b) of the present embodiment, the occupied area of the photovoltaic device (b) is the conventional device due to the influence of the laminate.
It occupies up to 9/10 of the joint area in (a).

As is apparent from the table, in the photovoltaic device (b) of the present embodiment, the photoelectric conversion efficiency is increased despite the large occupied area, and the open circuit voltage is remarkably improved. ing. This is because by increasing the occupied area, the forward current component of the diode characteristic, which was a substantial loss of the current component in the conventional photovoltaic device, can be reduced.

That is, when a photovoltaic device having a diode structure with a pn junction is irradiated with light, holes are attracted to the p-type semiconductor and electrons are attracted to the n-type semiconductor, respectively. A state similar to that in which a positive voltage and a negative voltage are applied to the type semiconductor and the n-type semiconductor is developed. Then, this is the same as when a forward bias as a so-called diode is applied to this pn junction, and a forward current flows from the p-type semiconductor in the photovoltaic device to the n-type semiconductor. Usually, this forward current can be easily observed by applying a forward bias to the diode without irradiating it with light.

Therefore, in the photovoltaic device having the diode structure which is irradiated with light, the photocurrent flowing from the n-type semiconductor to the p-type semiconductor and the order of flowing from the p-type semiconductor to the n-type semiconductor are internally provided. A current obtained by adding the directional current will flow as a whole.

Therefore, in the photovoltaic device of the above-mentioned embodiment, the forward current is reduced by increasing the occupied area, and the photocurrent value obtained as a whole can be increased. is there.

In the example of the photovoltaic device of the present invention, only polycrystalline silicon was used as the crystalline silicon.
The same effect can be expected by using single crystal silicon.

[0036]

In the photovoltaic device of the present invention, since amorphous silicon is inserted at the interface between the insulating amorphous material and crystalline silicon, recombination of photogenerated carriers at the interface is reduced. It becomes possible.

Further, in the photovoltaic device of the present invention, a laminate of amorphous silicon and an insulating amorphous material is interposed at a part of the interface between the one conductivity type crystalline silicon and the intrinsic amorphous silicon. Since it is inserted, the carrier recombination can be reduced, and the forward current in the photovoltaic device can be reduced by inserting this laminated body, which in turn improves the photovoltaic characteristics. It is possible to blame.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an element structure of a first embodiment of a photovoltaic device of the present invention.

FIG. 2 is a sectional view of the element structure of the second embodiment of the photovoltaic device of the present invention.

FIG. 3 is a cross-sectional view of an element structure of a conventional photovoltaic device.

[Explanation of symbols]

(1) ... p-type polycrystalline silicon (2) ... n-type polycrystalline silicon (3) (6) ... insulating amorphous material (4) (7) ... amorphous silicon

Claims (2)

[Claims] 1. A photovoltaic device, wherein amorphous silicon is inserted at an interface between crystalline silicon having a semiconductor junction exhibiting a photoelectric conversion function and an insulating amorphous material. 2. A photovoltaic device comprising a semiconductor junction having a photoelectric conversion function, which is composed of one conductivity type crystalline silicon, intrinsic amorphous silicon, and another conductivity type amorphous silicon. A photovoltaic device, characterized in that a laminated body made of amorphous silicon and an insulating amorphous material is inserted in a part of an interface between one conductivity type crystalline silicon and the intrinsic amorphous silicon. Power equipment.