JPH03214676A - Pin-type amorphous silicon solar cell and manufacture thereof - Google Patents

Abstract

PURPOSE:To enable attainment of a solar cell being inexpensive and excellent in a photoconductive characteristic and a conversion efficiency by a method wherein at least one layer of a protective film having resistance to a hydrogen gas is provided between a P layer and an amorphous silicon germanium film. CONSTITUTION:At least one layer of a protective film 4 having resistance to a hydrogen gas is provided between a P layer 3 and an amorphous silicon germanium film 5. Although the composition of the protective film 4 is not limited in particular so long as it does not impair films formed on a substrate before the formation of the protective film, an alpha-Si: H film being excellent in a photoconductive characteristic is preferably employed. In this case, a pin- type solar cell having an (i) layer formed into a multilayer of the the alpha-Si: H film and an alpha-SiGe: H film is obtained. By this method, the solar cell having no impairment in the ground film and being excellent in a conversion efficiency can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a pin W amorphous silicon solar cell and a method for manufacturing the same.

[Conventional technology]

In order to achieve high efficiency, pin-type amorphous silicon solar cells use hydrogenated amorphous silicon germanium (a-Si:H), which has a smaller optical gap than hydrogenated amorphous silicon (a-Si:H), in the T layer.
Efforts have been made to increase the absorption of long wavelength light using SiGg:H).

However, in the α-SiGa:H film, the reactivity of the Si source gas and the G6 source gas during film formation is significantly different.

For this reason, it was difficult to form a film in which Si atoms and G atoms were uniformly distributed and there were few dangling bonds in the film, and the superiority of the a-SiGg:H film could not be demonstrated.

Therefore, Journal of Non-Crystal Solids, Vol. 97.98 (1987), pp. 1667-1374.
llirx! ;olidz + 97 & 98 ( 1
987) LS67 to 1374), α-
It has been proposed to improve the light guiding properties of SiGe:H films.

Furthermore, recently, a method of improving photoconductive properties by eliminating the difference in decomposition reactivity between Si source gas and Ga source gas by using microwave plasma CVD in a high vacuum region has also been attracting attention.

[Problem to be solved by the invention]

However, when the triode method is used, the film formation rate is as slow as one color or less, and it is not practical as a T-layer of a pin-type solar cell, which requires a film thickness of several 10 oo i.

In addition, when hydrogen dilution method or microwave plasma CVD method is used, pin-type solar cells with excellent photoconductive properties can be produced.
Under the film forming conditions for forming the layer, source gases (SzH4,
(GgH4, etc.), which tends to damage the film formed on the substrate, resulting in a decrease in conversion efficiency.

Thus, a solar cell that takes advantage of the characteristics of amorphous silicon germanium has not yet been developed.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a t. −
Hydrogenated amorphous silicon germanium (α-Si
An object of the present invention is to provide a solar cell using Ge:H) that is inexpensive, has excellent photoconductive properties, and has excellent conversion efficiency.

[Means to solve the problem]

The object of the present invention is to provide a pin-type amorphous silicon solar cell using amorphous silicon germanium as an il, which is characterized by having at least one protective film resistant to hydrogen gas between the pN amorphous silicon germanium films. This is achieved by amorphous silicon solar cells.

It is also an object of the present invention to provide an amorphous silicon solar cell comprising at least a p layer, an i layer, a layer and a substrate,
(4) This is achieved by a pin type amorphous silicon solar cell comprising an amorphous silicon germanium film and a protective film resistant to hydrogen gas, wherein the protective film is located closer to the substrate than the amorphous silicon germanium film.

Furthermore, an object of the present invention is to provide a method for manufacturing a pin-type amorphous silicon solar cell using amorphous silicon germanium, in which the plasma power density is 0.0 when forming an i-layer.
After forming an amorphous silicon film on the p-layer by plasma decomposing a gas with a hydrogen content of 10 or less at 5 W/1 or less, an amorphous silicon germanium film was formed on the amorphous silicon film. This can also be achieved by a method for manufacturing a pin-type amorphous silicon solar cell.

The composition of the protective film is the film formed on the substrate before the formation of the protective film (for example, electrode film or P layer.Hereinafter, it refers to the film formed on the substrate before forming the protective film.
It is called the base film. ), an a-Si:H film having excellent photoconductive properties is preferably used, although there are no particular limitations.

In this case, it becomes a pin type thick layer having a multilayered head layer made of an α-Si:H film and an α-SiGa:H film. In the present invention, one layer is not limited to any number of layers.

The film thickness of the film-holding film varies depending on the film-forming conditions of other films constituting the solar cell, but is generally preferably 100 mm or more. If the film is thinner than 10 oo i, it will be less effective in preventing damage to the underlying film5.

The method for forming the lumbar protection film is preferably a photo-CVD method or a glow discharge plasma CVD method, which has a low film-forming rate.

a-. 5i:H film at a plasma bower density of 0. 0 5
It is preferable to form by plasma decomposition of a gas having f/1 or less and a hydrogen content of 10% or less.

If a gas with a hydrogen content of 10% or more is used, the underlying film will be damaged and the conversion efficiency will decrease. Also, bra x”-r
C'7 - Density 0. Even plasma decomposition of 0 5 F/1 or more damages the underlying film.

[Effect]

In the solar cell using the amorphous silicon germanium of the present invention, before forming the α-SiGa:H film, a film is made from hydrogen gas to capture the base film.

The above-mentioned film-retaining film has α-. SiGt:
Prevents physical and chemical damage to the doped base film caused by hydrogen gas generated during the production of hydrogen.

Furthermore, the protective film has a plasma power density of 0.0.
The α-1 film was formed by plasma decomposition of scum with a hydrogen content of 10% or less at a power of 5W/cm3 or less. By using the Si:H film, it is possible to form a film with excellent photoconductive properties in which the underlying film is not damaged by hydrogen gas.

〔Example〕

Examples of the present invention will be described, but the present invention is not limited thereto.

FIG. 1 is a sectional view showing the structure of a solar cell using the a-SiGg:E film of the present invention.

The solar cell includes a glass substrate 1 on which a Sn 0 2 film 2 is formed.
Above, B atom-doped α-1 as a p-layer. Si:H membrane and purulent membrane are 8Il! , α-Si:H film 4 of the i-layer of item 1, a-SiGa as the t-layer of the 21st item:
Ha5 and P atom-doped microcrystals. 5i film 6 and back surface M'
It is constructed by sequentially stacking vlL poles 7.

The glass substrate 1 is made of blue plate glass. 5 n
An O2 film 2 is formed to a thickness of about 5000 i. p-type α-S:
For the H film, add H, dilution B, H6 and S L E4 to the usual 1!
It is formed by a 1.56 MHz parallel plate type τf plasma CVD method.

The first layer ia-a-si:H film 4, which is a protective film, is S*
H4 gas as usual 15. 1,500 layers are formed at a low power density (preferably 15y++F/1 or less) by a 56 MHz parallel plate type rf plasma CVD method.

The 2Nth t-α-SiGa:H film 5 is formed using a magnetic field microwave plasma CVD apparatus as shown in FIG. The above-mentioned magnetic field microwave plasma CVI) apparatus includes a vacuum chamber 12 that is evacuated through an exhaust port 19, a discharge tube 13 disposed above the vacuum chamber 12, a magnetron 10 that supplies microwaves, and a The above discharge tube 1
3 and a waveguide 11 for guiding the wave. A solenoid coil 14 that generates a magnetic field is provided around the discharge tube 13. The vacuum chamber 12 is provided with a sample stand 18 on which the substrate &17 is placed, and a discharge gas inlet 15 whose tip opens toward the discharge tube 13 and a film-forming gas inlet 16 which opens toward the sample stand 18. is provided. The above le-type microcrystalline Si
The film 6 can be formed by a parallel plate RF plasma CVD method. Further, the back surface M electrode 7 is formed by a normal vacuum evaporation method.

In order to compare the performance of the solar cells of the present invention and solar cells other than the present invention, the following solar cells were manufactured.

(Manufacture of solar cell of the present invention) A solar cell was used in which approximately 5,000 layers of S2O2 film 2 were formed on a glass substrate 1 made of soda lime glass. 13 on this board
．． Using a 56MHz parallel plate RF plasma CVD method, H was used as the raw material gas, and diluted 1% B, H, (ciborane) was used.
Flowing 20 sccm and SiH4 20 sccm, substrate temperature 160°C, reaction pressure 200 mTorr, rf
α-Si diH film 6 doped with B atoms under the condition of power 3W
was formed.

Next, on top of this, the first layer t, which is a protective film, is layer 4.
A-. Si:H
PP +1+ 10oo. ; ,+21 1500,4
, (3) 20004 Each of these was manufactured. Note that the hydrogen gas concentration is 0.

As the second layer under the same conditions for each sample,
An α-SiGa:H film 5 was formed using a magnetic field microwave plasma CVD apparatus shown in FIG.

From the film forming gas inlet 16. 5iH48sccm and GgH
4 4 scan, 4 6 s from discharge gas inlet 15
ec@, microwave frequency 2. 54 GHz
, microwave output 100F, discharge gas pressure 1.6mTor
An a-SiGg:H film was formed under the following conditions: r, substrate temperature of 180° C., and magnetic field strength at the exhaust side end of the discharge tube 13 of 875 G.

Next, for the three samples mentioned above, the microcrystalline 54 film 6 was diluted with H2 to 100 ppm. Phosphine 50 pccm,
The film was formed using a parallel plate type τf plasma CVI) method with a discharge power of 60 W under the conditions of SiH4 2 zcarn + film formation temperature of 170° C. and reaction pressure of 600 mTorr.

Next, a back M electrode was formed by resistance heating vapor deposition to obtain a solar cell.

α-Si:H film (11 1000,4, +2+
The solar cells of 1sooA, (31 2ooo,;) are referred to as Example-1, Example-2, and Example-3.

SiH4 with a hydrogen gas concentration of 9 zccm,
Substrate temperature 180℃, reaction pressure 200rnTorr,
rf power 13F (plasma power density [Loar/,
A solar cell of Example 4 was produced in the same manner as Example 2 above, except that the α-Si:H film 4 was formed as a purulent retention film under the conditions of 1).

(Manufacture of solar cell of comparative example) Without forming the α-Si:H film 4 of the film-holding film, the p-layer α-S
Comparative example under the same conditions except that the i-α-5iGm:H film 5 was directly formed on the i:H film 3.
1 solar cell was formed.

When forming the α-Si:H film 4, a gas with a hydrogen content of 12% was used at an RF power of 16W (plasma power density of 0.5%).
A solar cell of Comparative Example 2 was formed under the same conditions as Example 2 except that it was formed using 05 F/1).

When forming the α-Si:H film 4, a gas with a hydrogen content of 10% was used at an RF tolerance of 19W (plasma power density of 0.[
l6F/,! ) A solar cell of Comparative Example 3 was formed under the same conditions as Example 2 except for forming the solar cell in Comparative Example 3.

When forming the α-Si:H film 4, a gas with a hydrogen content of 12% was supplied with a γft force of 19W (plasma power density of 0.
A solar cell of Comparative Example 4 was formed under the same conditions as Example 2 except that the solar cell was formed at 0.06 W/l, t).

(Performance comparison between the solar cell of the present invention and the solar cell of the comparative example) The solar cells of the present invention and the solar cell of the comparative example were
I-V% measurements were carried out under mF/one red filter.

The results are shown in FIG.

Figure 2 shows the 7-V characteristics 9 of the solar cell of Comparative Example 1 based on the IV characteristics 8 of the solar cell of Example 2 of the present invention, which has an α-Si:H gland thickness of 1 500 A. It shows. Although there is not much difference in short circuit current and open circuit voltage, the fill factor is 0.571 in the solar cell of the present invention (curve 8) compared to 0457 in the comparative example (curve 9), which is a significant improvement, indicating that the fill factor has improved. has been done.

As described above, in the solar cell of the present invention, since the fill factor is large, the conversion efficiency expressed by fill factor x open circuit voltage x short circuit current density is improved.

Similarly, the thickness of the α-Si:H film of the present invention was 10 oo. ，
;． 2000 A Example-1, Same-3 and Example-
In the solar cell No. 4, good characteristics with a fill factor of 0.55 or more were obtained. On the other hand, Comparative Example-2. The solar cells No. 3 and No. 4 had a fill factor of 0.50 or less, which was a small fill factor.

〔Effect of the invention〕

By providing an aSi:H film as a purulent-retaining film on the base film as in the present invention, a solar cell with good conversion efficiency without damage to the base film can be obtained.

In particular, a-S*Gg, which has absorption characteristics even in the long wavelength light range.
Since the :H film can be formed as an i-layer without damaging the underlying film, the efficiency of solar cells using amorphous silicon germanium can be greatly improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of the structure of an amorphous solar cell using silicon germanium of the present invention. FIG. 2 is a diagram showing 1-V characteristics of amorphous solar ta using silicon germanium according to an example of the present invention and a comparative example. FIG. 6 is a diagram schematically showing the structure of an example of a microwave plasma CVD apparatus used for forming a λ layer α-SiGa:H gland in a solar cell. 1......Glass substrate 2...
・・・・・・S 30 2 Exhibition 3・・・・・・・・・・・・
・pmα-Si:H film 4・・・・・・・・・・・・i-
α-Si:H gland 5・・・・・・・・・i-a-S
Otsu Gm: Hli6......Lou microcrystal Sip7......Back side A1 electrode 8...
......I-V characteristics of the solar cells produced according to the examples of the present invention 9...........I-V characteristics of the solar cells produced according to the comparative examples 10.・・・・・・・・・Magnetron 11・・・・・・Waveguide 12・・・・・・Vacuum chamber 13・・・・・・Discharge tube solenoid coil Discharge gas introduction Daily film gas inlet Substrate sample stage exhaust port

Claims (1)

[Claims] 1. In a pin-type amorphous silicon solar cell using amorphous silicon germanium as the i-layer, between the p-layer and the amorphous silicon germanium film,
An amorphous silicon solar cell characterized by having at least one protective film resistant to hydrogen gas. 2. In an amorphous silicon solar cell comprising at least a p-layer, an i-layer, an n-layer, and a substrate, the i-layer comprises at least an amorphous silicon germanium film and a protective film resistant to hydrogen gas, and the protective film is made of the amorphous silicon. A pin-type amorphous silicon solar cell characterized by being located closer to the substrate than the germanium film. 3. The pin type amorphous silicon solar cell according to claim 1 or 2, wherein the protective film is an amorphous silicon film. 4. Pin using amorphous silicon germanium
In the method for manufacturing type amorphous silicon solar cells, when forming the i-layer, the plasma power density is 0.05W.
/cm^3 or less and an amorphous silicon film is formed on the p layer by plasma decomposition of a gas with a hydrogen content of 10% or less, and then an amorphous silicon germanium film is formed on the amorphous silicon film. A method for manufacturing a pin-type amorphous silicon solar cell.