JPS5864070A - Amorphous silicon solar battery containing fluorine - Google Patents

Abstract

PURPOSE:To enable to largely improve the efficiency of a solar battery by providing an intrinsic amorphous silicon layer hydrogenated at p-i boundary in a pin type solar battery which employs a-Si:F:H. CONSTITUTION:A substrate 1 and a transparent electrode 5 are provided, and an intrinsic a-Si:H layer 6 is obtained by diluting and glow discharge decomposing silane (SiH4) or polysilane (SinH2n+2), preferably less than 1,000Angstrom . After the intrinsic a-Si:F:H layer 3 is accumulated, it is annealed with hydrogen plasma, or said intrinsic a-Si:H may be attached between the layer 3 and the n type amorphous semiconductor layer 7. The P type layer may preferably employ a- SiC:H, a-SiC:F:H, a-SiN:H, a-SiN:F:H, a-SiCN:H, or a-SiCH:F:H, and the n type layer may preferably employ the amorphous semiconductor thereof, which have excellent chemical resistance and HF resistance. The thickness of the layer 7 is normally 100-500Angstrom , and the thickness of the layer 3 is 2,000-10,000Angstrom . The thickness of the p type amorphous semiconductor layer 8 is 70-150Angstrom .

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amorphous silicon solar cell containing fluorine. It's a bird.

Amorphous silicon obtained by the plasma decomposition method of silane (Sta4) can be made by using W, IC, 8p・ar, etc.
It was discovered in 1976 that its conductivity could be greatly changed by doping it with PH, +B, and it, and a solar cell using amorphous silicon was prototyped by D. Arlson and others (1976). Since then, research has been actively conducted to improve the efficiency of amorphous silicon thin-film solar cells. Amorphous silicon, which is obtained by plasma decomposition of silane, has poor heat resistance and 5traeblθr-Tlrona.
sb, B, R, 0vahinaky is 811F,
Fluorine-containing amorphous silicon (a-81:F:H) obtained by glow discharge decomposition has poor heat resistance and 8t
In contrast to the report that the Raebler-Wronski efficiency was small, they subsequently fabricated a M-type 8 a-81:F:H solar cell and reported that an efficiency of 6.6- was obtained.

However, the structure of this MIB type solar cell is Mo/n
fJia-81:F:H/iJia-81:IF
:H/Nb1Os/Pd-muU5. Wb, O
Since the thickness of s was as small as 30 mm, reproducibility was poor and the manufacturing process was complicated, making it unsuitable for industrial production.

On the other hand, although the p-1-n type structure is generally simple and suitable for industrial production, the p-1-n type structure is simple and suitable for industrial production.
The problem with the efficiency of -1-n type solar cells is that they are lower than p-1-n solar cells using a-8i 2H obtained by glow discharge decomposition of EliH.

The present inventors found that p- obtained by glow discharge decomposition of 81) 4
As a result of intensive research to improve the efficiency of 1-n type solar cells, we found that by using a-81:F:H and providing an intrinsic layer of hydrogenated amorphous silicon at the p-1 interface in 7j pin type solar cells. The present invention has been completed based on the discovery that it is possible to greatly improve the efficiency of the process. The details will be explained below.

The amorphous silicon containing fluorine used in the present invention (hereinafter referred to as a-8i:F:H), Fi7 silane tF) or a derivative thereof, and/or a mixture of this and silane (81H4) or a derivative thereof, Must be 4k
Mix with inert gas such as argon or helium diluted with hydrogen and perform high frequency glow decomposition or direct current glow discharge decomposition using capacitive coupling method or conductive coupling method.
You can get good results.

The present invention relates to a p-1-n type solar cell using this a-8i:F:H in one layer (intrinsic layer). Figure 1 shows the structure of this type of conventional product. ■ is a substrate made of stainless steel or molybdenum, etc., ■ is n-type a-81:H or a-81,'F:H, ■ is intrinsic a-8i:IF:H, ■
is a p-type a-81:H or tja-81:F:H1 is a transparent electrode such as TO or 5n01. In a solar cell with this structure, the open circuit voltage Voa is as small as 0.3 volts.
In addition, the short circuit current Jsc is as small as 3mm/1 scratch, so
The efficiency was only about 0.4516, which was slow. The reason for this is thought to be as follows: 0, that is, 8 iF, glow discharge decomposition requires H! or 81H4 is required, but this inevitably generates HIF due to glow discharge decomposition.Since this IIP is a strong etching agent for Sl, it is deposited on the substrate and 9a-81:F:)I Therefore, the a-81 deposited on the substrate:
F: It is estimated that the surface of the first layer has many defects and recombination of carriers at the bonding interface increases, resulting in a decrease in efficiency.0 Figure 2 shows the structure of a long embodiment of the present invention. be. In this case, ■LDN type amorphous semiconductor, ■Horotic a
-81:H1■ A-81:II:F of Hiromonicity, ■ is a p-type amorph, an assemiconductor, ■ is a substrate, and ■ is a transparent electrode. Intrinsic a-81: H layer ■ is silane (B i, H,)
Alternatively, it can be obtained by glow discharge decomposition of polysilane (81 nHgn+t), diluted with hydrogen or inert gas if necessary, and its thickness must be about 30 μm or more. However, if the thickness of this intrinsic a-81:H becomes too large, it may cause a problem in the heat resistance of the cell, so it is preferable that the thickness is 1000 μm or less.

Further, as a method for obtaining this a-81:H layer (1), after an intrinsic a-81:F:1 layer is deposited, this layer may be annealed with hydrogen plasma for 7 times. Also, true a-fii:H:
This intrinsic a-81:H may also be added between the P layer (1) and the n-type amorphous semiconductor layer (2).

The amorphous semiconductor used for the n-type layer and the p-type layer is a-at:il obtained from silane or a derivative thereof.

a-81 obtained from fluorinated silane or its derivative:?
:H.

Hydrogenated or fluorinated amorphous silicon carbide obtained from silane or 7-silane and hydrocarbon (hereinafter a-810:H, respectively).

a-81C:F:H) Hydrogenated or fluorinated amorphous silicon nitride obtained by glow discharge decomposition of silane or heptadide and ammonia, or hydrazine or nitrogen (hereinafter a-81N:H, respectively)
, a-Elili: IF:H) or hydrogenated or fluorinated amorphous silicon carbon nitride obtained from silane, hydrocarbon, ammonia, etc. (hereinafter a-81ON: 11. a-EIiCN:F:
(denoted as H) is used. Especially p-type layer 4CFin-810:II, a-810:IP:H% on the side where light enters
a-81N:E.

a-81N:F:H, a-81ON:H, a-81(3
These amorphous semiconductors have excellent chemical resistance for the On-type layer, which is preferably N:F:H. (C is strong, so O is preferable
The thickness of the n-type amorphous semiconductor layer (2) is usually from aloo to 500 μm, and the thickness of the intrinsic a-131:F:H layer (2) is from 2,000 μm to 10,000 μm. P-type amorphous semiconductor layer ■Good.

Moreover, by replacing the n-type layer (2) and the p-type layer (2) shown in FIG. 2, it can function satisfactorily as a tun solar cell. However, in this case, L1 intrinsic a-81:? : H layer■ and pf which is in contact with K11il
Between the J layer and the intrinsic a-81:H layer, approximately 30i to 1000
It is necessary to put on a good mood.

FIG. 3 shows a separate embodiment of the present invention, where ■ indicates a transparent substrate 0 such as glass, etc., and @ l = t f? No. 1 [
] ■ functions as a transparent electrode. (2) is a p-type amorphous semiconductor, (2) is an intrinsic a-8i:H, (2) is an intrinsic a-Eli:P:H, (2) is an n-type amorphous semiconductor, and @ is an electrode made of aluminum, molybdenum, etc.

When depositing on a transparent substrate such as glass,
Since the transparent t& is etched when depositing a-81Nia:H with only Koto [Co., Ltd.], when SnJ is used as a p-type amorphous semiconductor layer (2), a-Elie:H is used.

a-81N:HX a-810:F:HS a-8
iN:IF:H, a-81σa2m.

a-81ON:IF:H is particularly preferred. Because p
a-81:H4) a- as an amorphous semiconductor layer of type
When using Eli:F:H, then JCa-B
This is because it is easily etched by TIF generated when depositing the 1:F:II layer (2). Company 0 genuine a-81:
H, thickness is 30A~1000mm, ■ is intrinsic a-, Si:
F:H, ■ is an n-type amorphous semiconductor layer, and a-
'81:TIXa-81:F:H.

a-81C:H,% a-810:F:H, a-8iN:
H, a-8in:IF:H.

a-81CN:)I, a-1ON:IF2H, etc. are used.

Plasma decomposition for depositing these amorphous semiconductors is typically performed at substrate temperatures of 200°C to 400°C. In addition, for n-type or up-type control, aluminum is used for p-type,
Elements from Group I of the periodic table, such as bones, and elements from Group M of the periodic table, such as phosphorus and arsenic, for N-type, as their hydrides or fluorides, are mixed in the reaction gas to glow. Discharge decomposition or ion in-branching of these elements
It is done by shiron jin.

As described above, in the present invention, in a p-1-n type amorphous silicon solar cell, one layer has a multilayer structure, and intrinsic a-81:1P:Ili is used as the first layer, and Intrinsic a-81 at the interface of p-1 as one layer of:
It is characterized by having an H layer of approximately 30 µm to 1000 µm, and has achieved a significant improvement in efficiency compared to the conventional solar cell with a single layer of a-81:IF:H. .

Next, this epoch-making efficiency improvement effect will be explained using an example.〇Example A quartz reaction tube with an inner diameter of 11 cm was used for glow discharge decomposition at a high frequency of 13.56 MHz. Each of the required amorphous semiconductors was deposited on a substrate by glow discharge decomposition with the following gas composition and the substrate temperature was fixed at 270 °C.
a-131 2F,'H (SiH4/HS = 6) a
-8iO:H (mouth, /81H,=2)a-81N:H
(MH,/SiH4:0.3)a-8iON:H(
m@2 (Kokuyo[,: 81.=0. 2: 5
: 1) The structure shown in FIG. 2 was used as an example, and the structure shown in FIG. 1 was used as a control example. The board ■ will eventually be 4,
BS (stainless steel). Both transparent electrodes (1) were made of TO by electron beam evaporation. The thicknesses of the p-type layers (2) and (2) are both 4100 μm, the thickness of the intrinsic a-81:F:H0゛ layer (2) is both 4000 μm, and the thickness of the n-type layers (2) and (2) are both 500 μm. Intrinsic a specific to the present invention
-9i: The thickness of the H layer (second layer) was 500 μm.
Note that the p-type amorphous semiconductor is obtained by doping with Ba1l@, and the boron concentration in the deposited film should be approximately 0.1 atom % even if the concentration is different. Further, the n-type amorphous semiconductor is obtained by doping with PH, and the phosphorus concentration in the deposited film is about 0.5 atom % in either case. Regarding the obtained various solar cells, AM-1 solar shemulator (100mW
/cm, determine the T-v% property, and calculate this as shown in Table 1, short circuit voltage 1et; Jaa (mm/♂), open voltage To
It was described in terms of e (volts), fill factor FF (-), and conversion efficiency d.

(Continued on page 12) As is clear from this Table 1, all of the control examples are J
ee is much smaller and Voc is also 0.2 volts
It can be seen that the diffusion potential of the p-1-n junction is not sufficiently formed because it is as small as ηaO of 2% or less because the IPXP is also small. In contrast, in the embodiment of the present invention, voc is 0.67 volt
Above θ, both lJe+c and 7F show large values, and the p-type amorphous semiconductor layer and the intrinsic a-8i:F:H layer (first
layer of intrinsic a-8i:H (second layer)
A-81, which has a large optical forbidden band in the 0 special Kp layer, shows that the DA can be greatly increased by adding only 500 μm.
0:H, a-81N: II, a-8101:il
By using the above, the effect becomes even more pronounced.

Ete O/p type a-810: H/i type a-81: H/i type a-81'yF, "H/n type a81: F: H/ 8
In the type B solar cell, i fil a-8
Table 2 shows the solar cell characteristics at 9 o'clock when the thickness of the 1:H layer (second 1 layer) was changed.

(Continues from 14) As can be seen from this table 2, the intrinsic a-8 of only 5om
i: Just adding the H layer (second layer) will greatly improve the
It has an improving effect. The thickness of this a-81:H layer is 1000
Even if the a-81:F:H layer (the first layer) becomes thicker than the a-81:F:H layer (the first layer), it still shows a large da. layer) Since the original heat resistance tends to not be utilized, the a-81:H layer is 10
It is desirable that the thickness be 0.00 mm or less.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing the structure of a conventional p-1-n type solar cell, and FIGS. 2 and 3 are schematic sectional views showing the structure of an embodiment of the present invention. Toshihiko Uchida, Patent Attorney, Kanebuchi Chemical Industry Co., Ltd.

Claims (1)

[Claims] One layer of an i p-1-n type amorphous silicon solar cell contains heptafluoride silane (81F) or its derivative and hydrogen, or fluoride silane or its derivative and silane or its In a solar cell using intrinsic a-81.:IP:H obtained by 2' discharge decomposition of a derivative,
A layer of intrinsic a-81:H obtained by glow and discharge decomposition from silane or its derivatives, or an a- obtained by hydrogen plasma annealing of 1ia-81:IF:H in the p layer, the 1st layer and the 0th layer. 81: An amorphous silicon solar cell characterized by providing a second layer consisting of a layer of If. 2 The thickness of the layer of intrinsic a-81:H is about 30 μm to 1 μm.
Amorphous silicon solar cell according to claim 1, characterized in that the amorphous semiconductor of the p-layer or n-layer has at least a layer on the side where light enters a-810-: H. a-8i(!:F:H, a-81N:H, h=B"LM
:F:B, a-81ON:Hla-81ON:F:)
The amorphous silicon solar cell according to claim 1 or 2, characterized in that the amorphous silicon solar cell is made of an amorphous semiconductor selected from the following. 4. Claim 1, characterized in that the amorphous semiconductor constituting the p-1-n type solar cell is deposited on a transparent substrate such as glass with 1 μm TO and 50 μm thick.
1. Amorphous silicon according to item 2 or 3
pond.