JP3281760B2 - Method for manufacturing photovoltaic device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a photovoltaic device comprising a stack of semiconductor layers.

[0002]

2. Description of the Related Art In a photovoltaic device, the light confinement effect is utilized by making the light incident side surface uneven so as to increase the optical path length and increase the absorption amount so that the irradiation light can be used efficiently. Has been done. FIG. 6 is a structural diagram of such a conventional photovoltaic device. In FIG.
Reference numeral 51 denotes an n-type polycrystalline silicon film having an uneven surface, and an i-type amorphous silicon layer is formed on the polycrystalline silicon film 51.
52 and a p-type amorphous silicon layer 53 are stacked in this order. On the amorphous silicon layer 53, a surface electrode on the light incident side
On the flat surface of the polycrystalline silicon film 51, a back electrode 56 is formed.

Indeed, although the current taken out increases by adopting the concavo-convex shape on the light incident side, a thin semiconductor layer is hardly formed in the concave or convex portion of the polycrystalline silicon film 51. It is difficult to uniformly stack a thin semiconductor layer on the surface of a semiconductor that has been made uneven, such as the polycrystalline silicon film 51. Therefore, it is inevitable that the semiconductor thin film to be formed is partially deficient (portion A in FIG. 6) or thin, and as a result, there is a problem that the photovoltaic characteristics are rather deteriorated.

As a means for solving such a problem, an insulating layer is formed in advance on an uneven transparent electrode on glass, and a plurality of amorphous thin film semiconductor layers (for example, p-type semiconductor layers) having different conductivity types are formed thereon.
An amorphous photovoltaic device in which an in-amorphous silicon laminate is formed has been devised (Japanese Patent Publication No. 5-74951). In this photovoltaic device, by forming an insulating layer on the transparent electrode, the uneven state of the uneven surface of the transparent electrode is alleviated, and the amorphous semiconductor layer is easily laminated uniformly on the transparent electrode. In addition, the protrusion is prevented from penetrating through the amorphous thin film semiconductor layer laminated on the insulating layer, and the improvement of the photovoltaic characteristics due to the uneven shape can be ensured.

[0005]

However, in the photovoltaic device disclosed in Japanese Patent Publication No. 5-74951, an insulating layer and an amorphous thin-film semiconductor layer are formed in this order. However, since the amorphous thin-film semiconductor layer is exposed to heat and plasma during formation, the constituent elements of the insulating layer diffuse into the amorphous thin-film semiconductor layer, and the film characteristics are deteriorated and the photovoltaic characteristics are reduced. The problem remains.

The present invention has been made in view of such circumstances, and by forming an insulating layer after forming a thin film semiconductor layer, deterioration of photovoltaic characteristics caused by partial defect of the thin film semiconductor layer is prevented. It is an object of the present invention to provide a method of manufacturing a photovoltaic device, which can prevent the deterioration of the photovoltaic characteristics caused by the diffusion of the constituent elements of the insulating layer.

[0007]

According to a first aspect of the present invention, there is provided a method for manufacturing a photovoltaic device, comprising the steps of: forming an i-type and a p-type semiconductor thin film on an n-type semiconductor having an uneven surface; Are stacked in this order, a method for manufacturing a photovoltaic device that generates an electromotive force by irradiating the semiconductor and the semiconductor thin film with light,
Forming an insulating layer on the p-type semiconductor thin film in a range of 5 to 50 °;
And forming a surface electrode on the insulating layer.
And a step of

According to a second aspect of the present invention, there is provided a photovoltaic device manufacturing method, comprising the steps of: forming an i-type semiconductor on an n-type semiconductor having an uneven surface
And a p-type semiconductor thin film laminated in this order, a method of manufacturing a photovoltaic device that generates an electromotive force by irradiating the semiconductor and the semiconductor thin film with light, wherein the upper part of the p-type semiconductor thin film is insulated. A step of forming an insulating layer in a range of 5 to 50 ° and a step of forming a surface electrode on the insulating layer .

[0009]

In the first invention, i-type and p-type semiconductor thin films, an insulating layer , and a surface electrode are formed in this order on an n-type semiconductor having irregularities on the surface . Further, in the second invention, i-type and p-type semiconductor thin films are formed in this order on an n-type semiconductor having irregularities on the surface, and the upper portion of the semiconductor thin film is changed to an insulating layer by oxidation or nitridation. And then
A surface electrode is formed on the insulating layer. This solves the conventional problem that the constituent elements of the insulating layer are diffused into the inside of the semiconductor thin film when the semiconductor thin film is formed, and prevents a decrease in photovoltaic characteristics. Further, even if the semiconductor thin film is deficient, the MIS solar cell having the semiconductor layer / insulating layer / electrode structure is formed at the deficient portion because the insulating layer is formed on the roughened light incident side surface. It is formed to compensate for a decrease in photovoltaic characteristics due to a defect in the semiconductor thin film.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be specifically described with reference to the drawings showing the embodiments.

In a heterojunction photovoltaic device in which amorphous silicon is formed on polycrystalline silicon, poly-Si (n-type)
HIT (Heteroju) with / a-Si (i-type) / a-Si (p-type) structure
An embodiment of the present invention will be described for a photovoltaic device of the nction with intrinsic thin-layer type.

FIG. 1 is a structural diagram of such a HIT type photovoltaic device manufactured by the manufacturing method of the present invention. FIG.
In the figure, reference numeral 1 denotes an n-type polycrystalline silicon film (thickness: 300 μm) having an uneven surface, and an i-type amorphous silicon layer 2 (thickness: 10 to 200 °) on the polycrystalline silicon film 1. ) And a p-type amorphous silicon layer 3 (film thickness: 50 to 200 °) are stacked in this order. On the amorphous silicon layer 3, S
An insulating layer 7 (film thickness: 5 to 50 °) made of an iO ₂ film is formed. On the insulating layer 7, a surface electrode 4 (thickness: 500-1500 °) made of an ITO film and a collector electrode 5 (width 5 μm or less × thickness 5 μm) made of a Ti / Ag film are formed. On the flat surface of the film 1, a back electrode 6 (2 μm or less in thickness) made of an Al film is formed. Note that there is a portion (B portion) where the amorphous silicon layers 2 and 3 to be laminated are not formed and are missing.

Next, a method of manufacturing the photovoltaic device having such a configuration will be described.

FIG. 2 is a sectional view showing the steps of a first example of the manufacturing method. First, after cleaning the n-type polycrystalline silicon film 1, irregularities having a pitch and a height of about 10 μm are formed on one surface of the polycrystalline silicon film 1 by plane orientation etching using an aqueous sodium hydroxide solution. (Figure 2
(A)). Next, an i-type amorphous silicon layer 2 and a p-type amorphous silicon layer 3 are continuously formed on the uneven surface of the polycrystalline silicon film 1 by plasma CVD (FIG. 2).
(B)). At this time, the amorphous silicon layers 2 and 3 are not formed partially, and a defective portion (C portion) is generated. The formation conditions by plasma CVD at this time are as follows. i-type amorphous silicon layer 2 Source gas: SiH ₄ , deposition temperature: 120 ° C., pressure: 0.2T
orr, power: 30 mW / cm ² p-type amorphous silicon layer 3 Source gas: B ₂ H ₆ : SiH ₄ : H ₂ = 0.1: 5: 100
, Film forming temperature: 120 ° C., pressure: 0.2 Torr, power: 3
0 mW / cm ²

Next, an insulating layer 7 made of a SiO ₂ film is formed on the amorphous silicon layer 3 by plasma CVD (FIG. 2C). Next, a surface electrode 4 made of an ITO film is formed on the insulating layer 7 by a sputtering method (FIG. 2).
(D)). Finally, a collector electrode 5 made of a Ti / Ag film is formed on the surface electrode 4 and a back electrode 6 made of an Al film is formed on the other flat surface of the polycrystalline silicon film 1 by vapor deposition (FIG. 2 ( e)).

FIG. 3 is a sectional view showing the steps of a second example of the manufacturing method. First, after the n-type polycrystalline silicon film 1 is washed, irregularities having a pitch and a height of about 10 μm are formed on one surface thereof in the same manner as in the first example (FIG. 3).
(A)). Next, an i-type amorphous silicon layer 2 and a p-type amorphous silicon layer 3 are continuously formed on the uneven surface of the polycrystalline silicon film 1 by plasma CVD (FIG. 3).
(B)). The formation conditions by plasma CVD at this time are the same as those in the first example. At this time, a portion (D portion) where the film thickness of the amorphous silicon layers 2 and 3 is insufficient and the film thickness is thinner than other regions partially occurs.

Next, the intermediate is immersed in nitric acid, and a part of the formed amorphous silicon layer 3 on the surface side is oxidized to be insulated to form an insulating layer 7 made of a SiO ₂ film. (FIG. 3 (c)). In addition, the amorphous silicon layer 2,
In a portion where film formation of 3 is insufficient, both amorphous silicon layers 2 and 3 are oxidized to become an insulating layer 7 (SiO ₂ film). The thickness of the insulating layer 7 formed here depends on the concentration of nitric acid and the temperature.
_, Determined by _the immersion time. As an example, in this embodiment, HNO ₃ : 50 g / H ₂ O: 1 liter, immersion at 50 ° C. for 1 minute, thereby forming a SiO ₂ film having a thickness of 20 °. The oxidation reaction of silicon with nitric acid is as follows. Si + 4HNO ₃ → SiO ₂ + 4NO ₂ + 2H ₂ O

Next, as in the first example, a surface electrode 4 made of an ITO film is formed on the insulating layer 7 by a sputtering method (FIG. 3D). A collecting electrode 5 made of an Ag film and a back electrode 6 made of an Al film are formed on the other flat surface of the polycrystalline silicon film 1 by vapor deposition (FIG. 3E).

In the above embodiment, single-crystal silicon may be used instead of polycrystalline silicon. Further, germanium may be used instead of silicon. Further, germanium, silicon germanium or silicon carbon may be used instead of amorphous silicon. Further, microcrystals may be used instead of amorphous. The texturing may be performed by mechanical processing using a cutting jig in addition to the above-described etching.

As the insulating layer 7, in addition to the above-mentioned oxide such as SiO ₂ , a nitride such as SiN or SiC
Is also effective. Further, as a method of forming the insulating layer 7, in addition to the above-described example, a processing method of oxidizing and nitriding amorphous silicon by plasma may be considered.

The surface electrode 4 has, in addition to the above-mentioned ITO, Z
nO, SnO _{2 and the} like can also be used, and as a forming method, there is a CVD method other than the sputtering method. In addition, as a method for forming the collecting electrode 5, a sputtering method is also possible in addition to the above-described evaporation.

Next, the photovoltaic device of the present invention having the configuration shown in FIG. 1 (hereinafter, referred to as the present invention) and the conventional photovoltaic device having the configuration shown in FIG. 6 described above (hereinafter, referred to as the conventional example). Table 1 below shows the photovoltaic characteristics of the above. The conventional example is different only in that the insulating layer 7 (SiO ₂ film) does not exist.
The configuration of the other parts is exactly the same as that of the present invention.

[0023]

[Table 1]

The effect of the present invention and the effect of the insulating layer 7 (Si
FIG. 4 shows the relationship between the thickness of the insulating layer 7 (SiO ₂ film) and the photovoltaic characteristics in the example of the present invention in order to verify the optimum thickness of the O ₂ film.

As can be seen from the results shown in Table 1 and FIG. 4, by inserting the insulating layer 7, the open-circuit voltage V
_OC and short circuit current I _SC are improved. If there is a portion where the amorphous silicon formed on the polycrystalline silicon is not partially formed due to the unevenness of the base, the conventional example causes a decrease in photovoltaic characteristics due to the effect of the defective portion. Was. In the structure of the example of the present invention, the MIS type photovoltaic device in which the insulating layer 7 is sandwiched between the deficient portions (portion B in FIG. 1) can compensate for the deterioration of the photovoltaic characteristics. In the MIS type photovoltaic device, the thickness of the insulating layer greatly affects the photovoltaic characteristics. FIG. 4 shows that the thickness of the insulating layer is 20
In the case of Å, the conversion efficiency η is the highest, and in the case of the range of 5 to 50 °, the photovoltaic characteristics are improved as compared with the conventional example having no insulating layer. This is because the open-circuit voltage V _OC of the MIS photovoltaic device increases with the thickness of the insulating layer, but as the thickness increases, the short-circuit current I _SC tends to decrease.

Next, an example of application of the present invention to an amorphous silicon photovoltaic device will be described. FIG. 5 is a structural diagram of such a photovoltaic device. In FIG. 5, reference numeral 11 denotes a substrate having an uneven surface. On a substrate 11, an n-type amorphous silicon layer 12 (thickness: 500 °), an i-type amorphous silicon layer 13 (thickness: 6000 °), a p-type amorphous silicon layer 14
(Film thickness: 100 mm) are laminated in this order. On the amorphous silicon layer 14, an insulating layer 15 made of a SiO ₂ film, a surface electrode 16 made of an ITO film as a light incident electrode, and a collecting electrode 17 made of a Ti / Ag film are formed. They are formed in order.

Next, a method of manufacturing the photovoltaic device having the structure shown in FIG. 5 will be briefly described. An n-type amorphous silicon layer 12, an i-type amorphous silicon layer 13, and a p-type amorphous silicon layer 14 are successively formed on a substrate 11 by a plasma CVD method. The formation conditions by plasma CVD at this time are as follows. n-type amorphous silicon layer 12 Source gas: PH ₃ : SiH ₄ = 1: 10, deposition temperature: 120
° C, pressure: 0.2 Torr, power: 30 mW / cm ² i-type amorphous silicon layer 13 Source gas: SiH ₄ , deposition temperature: 200 ° C, pressure: 0.2T
orr, power: 30 mW / cm ² p-type amorphous silicon layer 14 Same as amorphous silicon layer 3 described above.

After that, similarly to the above-described embodiment, the insulating layer 15 is formed by immersing in the nitric acid and oxidizing the amorphous silicon layer 14. Then, the surface electrode 16 is formed by a sputtering method, and the collector electrode 17 is formed by vapor deposition.

After forming a SiO ₂ film as an insulating layer,
Exposing the SiO ₂ film to the process temperature of the semiconductor layer activates the diffusion of the element of the SiO ₂ film, and the mixing of this element causes the deterioration of the characteristics of the semiconductor layer. However, even in the present embodiment, such a problem does not occur because the SiO ₂ film serving as the insulating layer is formed after forming the semiconductor layer.

Here, for comparison, in the amorphous silicon photovoltaic device as shown in FIG. 5, the case of annealing at 200 ° C. for 1 hour after the formation of the insulating layer of SiO ₂ film, the case of
In the case where it was left at room temperature after formation of the O ₂ film of the insulating layer, both to form the surface electrode of the ITO film, to produce two kinds of the photovoltaic device was measured each photovoltaic characteristics . The measurement results are shown in Table 2 below. When the annealing process is performed, the photovoltaic characteristics are deteriorated.

[0031]

[Table 2]

In this embodiment, germanium, silicon germanium, or silicon carbon may be used instead of amorphous silicon. Further, microcrystals may be used instead of amorphous.

When an amorphous semiconductor is formed by plasma CVD after the formation of the insulating layer, the diffusion of the constituent elements of the insulating layer is further activated since surface energy due to plasma is applied in addition to heat. It is expected that. Therefore, in the method of forming the insulating layer after forming the semiconductor layer as in the present invention, the characteristics of the manufactured photovoltaic device can be improved.

[0034]

As described above, in the present invention, an insulating layer is formed after a semiconductor thin film is formed, or a part of the semiconductor thin film is formed into an insulating layer by oxidation, nitridation, or the like to form an insulating layer. Then, since a surface electrode was formed on the insulating layer, a film-forming type junction photovoltaic device such as a HIT structure formed by forming a thin film semiconductor layer on the surface of a crystalline substrate, and unevenness In a photovoltaic device such as a photovoltaic device in which an amorphous semiconductor is further formed on the surface of the amorphous semiconductor layer on which is formed a junction, the constituent elements of the insulating layer are diffused into the semiconductor thin film to form a photovoltaic device. It is possible to solve the conventional problem of lowering power characteristics, and to manufacture a photovoltaic device with improved photovoltaic characteristics.

[Brief description of the drawings]

FIG. 1 is a structural diagram of a photovoltaic device manufactured according to the present invention.

FIG. 2 is a cross-sectional view illustrating steps of a manufacturing method according to the present invention.

FIG. 3 is a cross-sectional view illustrating steps of a manufacturing method according to the present invention.

FIG. 4 is a graph showing the relationship between the thickness of an insulating layer and photovoltaic characteristics.

FIG. 5 is a structural diagram of a photovoltaic device manufactured according to the present invention.

FIG. 6 is a structural diagram of a photovoltaic device manufactured by a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polycrystalline silicon film (n type) 2 Amorphous silicon layer (i type) 3 Amorphous silicon layer (p type) 4 Surface electrode 5 Collector electrode 6 Back electrode 7 Insulating layer 11 Substrate 12 Amorphous silicon layer ( 13) Amorphous silicon layer (i-type) 14 Amorphous silicon layer (p-type) 15 Insulating layer 16 Surface electrode 17 Collector electrode

Continuation of the front page (56) References JP-A-2-288369 (JP, A) JP-A-3-256368 (JP, A) JP-A-6-61512 (JP, A) JP-A-3-209780 (JP) , A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 31/04-31/078

Claims (2)

(57) [Claims] An i-type and a p-type semiconductor thin film are laminated in this order on an n-type semiconductor having irregularities on its surface, and a photovoltaic device that generates an electromotive force by irradiating the semiconductor and the semiconductor thin film with light. The method of manufacturing a power device, wherein the p
Forming an insulating layer in a range of 5 to 50 ° on a semiconductor thin film of a mold, and forming a surface electrode on the insulating layer
And a method for manufacturing a photovoltaic device. 2. A photovoltaic device comprising: an i-type and a p-type semiconductor thin film laminated in this order on an n-type semiconductor having irregularities on its surface, and generating an electromotive force by irradiating the semiconductor and the semiconductor thin film with light. The method of manufacturing a power device, wherein the p
Forming an insulating layer in the range of 5 to 50 ° by insulating the upper portion of the semiconductor thin film of the mold, and forming a surface electrode on the insulating layer
And a method of manufacturing a photovoltaic device.