JPH0258876A - Manufacture of substrate for solar cell and solar cell - Google Patents

Abstract

PURPOSE:To form unevenness excellent in reproducibility and controllability on a substrate surface, and improve photovoltaic conversion efficiency, by a method wherein, after etch-pits are formed on the surface of crystal silicon by chemically treating the crystal silicon, the pattern of the etch-pits is transferred on the surface of low melting point glass under a heated state. CONSTITUTION:After a crystal silicon wafer 15 having crystal orientation of (100) face is subjected to surface polishing with diamond paste, pyramid type etch-pits are formed on the surface by chemical treatment. The depth of etch-pit is desirable to be 0.2-0.5mum. A substrate 11 is obtained by transferring the pattern of etch-pit on the surface of low melting point glass under a heating state at 500-600 deg.C. Thereby, uneveness excellent in reproducibility and controllability is formed on the substrate surface, and a solar cell having high photovoltaic conversion efficiency can be constituted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a substrate for a solar cell having a textured structure, and to a solar cell.

[Prior Art] A solar cell is constructed by forming a semiconductor layer that performs photoelectric conversion on a transparent conductive film provided on a glass substrate, and laminating a conductive film on this semiconductor layer.

Conventionally, substrates for solar cells have been made with uneven surfaces to improve light confinement, as disclosed in Japanese Patent Laid-Open No. 82-98, for example.
It is disclosed in Japanese Patent No. 677. JP-A-62-98f1
The one described in Japanese Patent No. 77 is a glass substrate having an uneven surface by welding flat glass and finely powdered glass.

[Problems to be Solved by the Invention] However, the conventional glass substrate having an uneven surface has the following problems.

■The uneven shape is non-uniform, and the reproducibility and controllability of the uneven shape is poor.

(2) As a result of (2) above, there is a limit to the improvement of optical confinement properties, and thus there is a limit to the improvement of photoelectric conversion efficiency.

An object of the present invention is to form a concavo-convex shape with good reproducibility and controllability on the surface of a substrate, and to construct a solar cell with high photoelectric conversion efficiency.

[Means to solve the problem]

The method for manufacturing a solar cell substrate according to claim 1.

After chemically treating crystalline silicon having a (100) crystal orientation to form etch bits on the surface of the crystalline silicon, the pattern of the etch bits was transferred to the surface of low-melting glass under heating. It is something.

The solar cell according to claim 2 includes: a substrate formed by transferring crystalline silicon etch bits onto a surface of low-melting glass; a transparent conductive film provided on the surface of the substrate on which the etch bits are formed; and the transparent conductive film. The device includes a semiconductor layer provided on the surface of a film to perform photoelectric conversion, and a conductive film provided on the surface of the semiconductor layer.

The substrate of the present invention can be produced by applying the pattern of the etch bits under appropriate conditions, such as by pressing an original plate having etch bits on its surface or by setting it on a roll and rolling glass that can be used as a substrate. obtained by transcribing.

Next, a method for manufacturing the substrate of the present invention will be described in detail.

In the present invention, as the crystalline silicon having the matrix of the etch bits, in the present invention, crystalline silicon having the (+00) crystal orientation is chemically treated with a strong alkali such as KO) to form pyramid-shaped etch bits on the surface. Use formed crystalline silicon.

The depth of the etch bit in this case can be adjusted depending on the processing conditions, but may be 0.1 to 2. The thickness of the Oit layer, especially when used as a solar cell, is preferably 0.2 to 0.5 m thick, and the thickness of the crystalline silicon used here is approximately 0.1 to 2.0 m thick. It is preferable for handling.

A thin film made of a material harder than crystalline silicon is formed on the etch bit obtained as described above by sputtering, CVD, or the like. Such materials include Tie, diamond.

Examples include materials having high hardness and heat resistance, such as TiB2 and ZrB2. Among these, especially TiC and TiB2
A thin film of is preferred. The thickness of the thin film is 1" to 42, preferably 5 to 2Qp+s.

Next, a holding material such as stainless steel and a highly hard material (the surface without the etch bit, that is, the top surface) are bonded using a glass adhesive or the like. Thereafter, lapping and etching are performed to remove the crystalline silicon, and an original plate for transfer is produced.

The etch bit surface of the substrate surface obtained by pressing the transfer master plate and the glass substrate is coated with a known photoelectric conversion layer such as amorphous silicon, polycrystalline silicon, microcrystalline silicon, etc., preferably by plasma CVD method. A solar cell can be obtained by forming an amorphous silicon layer, a polycrystalline silicon layer, etc., and providing a transparent electrode such as ITO thereon. Since the surface of the photoelectric conversion layer has the etched edges of the substrate,
Photoelectric conversion efficiency can be increased by about 10-40% over conventional solar cells.

The solar cell of the present invention is manufactured using a plasma CVD apparatus.

In the solar cell of the present invention, the raw material produced using a raw material having silicon atoms is Si[(S
i) nH2n+z, n is 1 or 2] and/or any of the halogenated silanes represented by the general formula 5iHo-sX-1 (x: halogen atom), or a mixture of two or more of these Among them, silane SiH < and/or halogenated silane in which X is chlorine or fluorine is preferred, especially S! H4, S
i 82 F2 or SiF+ is preferred.

In addition, as is well known, dopants make semiconductors p-type or n-type.
It is a substance used for forming a type, and when forming a p-type, it is an element from group Ⅰ of the periodic table of elements, and when forming an n-type, it is an element from group V. The dopant is mixed in the raw material gas as a dopant gas as a single vapor and/or a gaseous compound. Examples of these dopant gases include B2HE, BF3
.

Examples include PH3 and PF3.

The dopant gas is mixed in a gas ratio of 10% to 1% by volume with respect to the raw material containing silicon atoms.

In the present invention, plasma refers to a plasma state in which a reactive gas is discharged in an electromagnetic field.

In the present invention, the dilution ratio of the raw material silicon compound with hydrogen and/or noble gas is 30 times or more, but this is due to the partial pressure P of the silicon compound in the reaction vessel and the dilution ratio of the diluent gas such as hydrogen. Pressure P(H2) and P(H2)/P>
0 means 30 In the present invention, especially 50
It is desirable to adjust the range of 0≧P()12)/P>30, and by using a reaction gas in this range, the crystallinity in the obtained silicon thin film can be increased, while P(H2 )/P<30, the crystallinity decreases, and P(H2)/P>500, the film formation rate decreases, which is not preferable.

For example, the deposition rate when P(H2)/p=soo is 1/l of the deposition rate when P(H2)/P=30.
It decreases to O.

In the present invention, the pressure in one reaction chamber is set to 1 Torr or more:
, 1 atm or less.

When the pressure inside the reaction chamber is not vortexed by ITarr, the obtained silicon thin film layer tends to become amorphous as the degree of pressure reduction increases, and when it exceeds 1 atm, the pressure must be considerably high to generate plasma. In the present invention, it is particularly preferable to set the temperature to 2 to 50 Torr, which is unsuitable for the purpose of the present invention because it is impossible to obtain a practically stable plasma due to the need for voltage.

In addition, in the plasma CVD method described above, a pin junction of amorphous silicon is formed at a substrate temperature of 100 to 300°C.
It can be formed by adopting conditions of a reaction pressure of 10 mTorr to 10 Torr and a power density of 0.01 to 0.05 w/cm<2>. The film thickness is, for example, 2 layers: 100 to 300 people, 1 layer: 1,000 to 5,000 people
0 A, N layer: Estimated to be 100 to 400 people. Note that one layer usually does not contain a dopant, but it can also be formed so that the degree of dopant changes to a gradient.

After providing a PN or pin junction to the substrate, a transparent conductive film and/or metal comb electrodes can be formed. As a transparent conductive film, tin oxide or ITO (
Indium-tin oxide) was adopted. These transparent conductive films are formed by a spray method or a sputtering method. The film thickness is preferably about 500 to 5,000 A.
If the resistance of the P+ layer and N+ layer on the light incident side is sufficiently low, there is no need to form a transparent conductive film.

[Effect] According to the present invention, there are the following effects.

(2) The uneven shape formed on the substrate surface is uniform because the matrix is a crystalline silicon pyramid-shaped etch bit (irregularities of several hundred OA).

(2) An original plate having a pyramid-shaped etch plate made of crystalline silicon can be used as the matrix for (2) above, and the reproducibility of the uneven shape formed on the substrate surface is good.

■By adjusting the pyramid-shaped etch bit shape of crystalline silicon, the uneven shape formed on the substrate surface can be easily controlled.

(2) As a result of (1) to (2) above, incident sunlight is effectively confined within the solar cell, and a solar cell with high photoelectric conversion efficiency can be constructed even if the film thickness is thinner than usual.

(2) When the semiconductor layer that performs photoelectric conversion is a polycrystalline silicon thin film, the light confinement properties of a polycrystalline silicon thin film solar cell can be achieved. In addition, the presence of the uneven structure provided on the substrate surface improves the adhesion of the polycrystalline silicon thin film and improves the manufacturability of the solar cell.

(2) When the semiconductor layer that performs photoelectric conversion is an amorphous silicon thin film, the light confinement properties of an amorphous silicon thin film solar cell can be achieved.

(2) When the semiconductor layer that performs photoelectric conversion is composed of a composite of a polycrystalline silicon thin film and an amorphous silicon thin film, the effects of the combination of (1) and (2) described above can be obtained. Also, above ■
, ■Higher photoelectric conversion efficiency can be achieved than in .

[Example] Fig. 1 is a schematic diagram showing the manufacturing process of a polycrystalline silicon thin film solar cell according to a first embodiment of the present invention, and Fig. 2 is a schematic diagram showing a manufacturing process of a polycrystalline silicon thin film type solar cell according to a second embodiment of the present invention. FIG. 2 is a schematic diagram showing a type solar cell.

(First Example) The polycrystalline silicon thin film solar cell lO shown in FIG.
A substrate (glass) 11, a conductive film (stainless steel) 12, a polycrystalline silicon thin film 13A (semiconductor layer), and an ITO 1
It consists of a laminated structure of 4 (transparent conductive films).

The specific structure of the solar cell 10 and its manufacturing method are as follows.

■ In the present invention, a crystalline silicon wafer 15 having a (+00) crystal orientation is used as the crystalline silicon having the matrix of the etch bit in the present invention (see FIG. 1(A)).
.

■The surface of this crystalline silicon wafer is polished with a diamond paste of 10 pm or less (see Figure 1 1))
, further this surface was treated with [ethylenediamine (EDA)
+ pyrocatechol + water] at a temperature of 50 to 90°C to form pyramid-shaped etch bits on the surface (see Figure 1 (C)). It can be adjusted depending on the conditions, but from 0.1 to
2.0 gm, especially for use as solar cells, and 0.0 gm.
The thickness of the crystalline silicon used here is preferably about 0.1 to 2.0 mm for handling reasons.

■The pattern of the etched bits of the crystalline silicon is 50
The substrate 11 is obtained by transferring it onto the surface of low-melting glass under heating at 0 to 800°C (see FIG. 1(D)).

When the etch bits transferred to the substrate 11 were observed using a scanning electron microscope, it was confirmed that the etch bits of crystalline silicon were transferred as they were.

(2) Stainless steel (other metals such as Affi may also be used) is deposited on the surface of the substrate 11 on which the etch bits are formed to form a conductive layer 11112 (see FIG. 1(E)).

■A polycrystalline silicon thin film 13A is formed on the surface of the conductive film 12 by plasma CVD under the following conditions (first
(See figure (F)).

N 10 layer: PH30,04SC:CM, SiH*2
SC(Jl, SiF420SCCM, H211
005CC(7) Mixed gas is flowed into a 2 Torr reaction tank, the substrate humidity is set to 250°C, and discharge is performed at a power density of 0.5 CC/C2 to form a polycrystalline silicon layer of about 1000 A on the conductive film 12. was formed.

N-layer: SiH+ 2SCC! l, 5iF
430SC:CM.

A mixed gas of H211005CC was flowed into the reaction tank at 2 Torr, the substrate temperature was set at 250° C., and discharge was performed at a power density of Q, 5 W/cm 2 to form a polycrystalline silicon layer of approximately 5 Torr on the N soil layer.

P soil layer: BF30.04SCCM, Si)! 4
2SCCM, SiF+20S (C:M, 82
A mixed gas of 1OQsccM was flowed into the reaction tank at 2 Tarr, the substrate temperature was set to 200°C, and a power density of 0.5 W/c 2 was discharged to form a polycrystalline silicon layer of about 1000 on the N-layer. .

(2) Further, on the P soil layer of the polycrystalline silicon thin film 13A, approximately 1000 A of (1) TO was laminated by electron beam evaporation to form a transparent conductive film (see FIG. 1(F)).

The solar cell obtained as described above was heated using a solar simulator with an AMI of 100 W/c at a current of -
As a result of voltage measurement, vOC is 0.58V, Jsc
is 17.8mA/am2. F F was 0.68, and photoelectric conversion efficiency η was 7.02%, which was good.

In addition, when we measured the surface reflection characteristics of this solar cell, we found that
It was found that the reflectance was reduced over the entire wavelength range, indicating that optical confinement was achieved.

(Second Example) The amorphous silicon thin film solar cell 20 shown in FIG.
A substrate (glass) 11, a conductive film (stainless steel) 12, an amorphous silicon thin film 13B (semiconductor layer), and an ITO 1
4 (consisting of a laminated structure of 4 transparent layers and 1).

The specific structure of the solar cell 20 and its manufacturing method are as follows.

The structure of the substrate 11 and the conductive fi 12 and the manufacturing process thereof are the same as steps 1 to 2 of the first embodiment described above.

The amorphous silicon thin film 13B is electrically conductive! It was formed on the surface of 1112 under the following conditions.

1 layer; PH3: SiH4: H2=0.01
: 1 : 30 mixed gas 101) + Torr,
Flow into the reaction tank at a flow rate of 20SCCN, O,I3W/c■
Approximately 300 people formed an amorphous silicon layer doped with P on the substrate at 200° C. by discharging at a power density of 2.

1 layer; SiH+ gas at 200mTorr, 30S
Flow into the reaction tank at the flow rate of CCM, and set the substrate temperature to 200℃ and 0.
．． By discharging at a power density of 031/cpeng2, an amorphous silicon layer of about 5000 layers was formed on the n-layer.

9 layers; 82Hs: 5i) I4: H2=
0. O05: 1:100 mixed gas at 100mTo
rr, flowed into the reaction tank at a flow rate of 20SCCM, and the substrate temperature was 2.
By discharging at a temperature of 00°C and a power density of 0.30/C2, the amorphous silicon layer doped with B on the iM was approximately
100 people were formed.

Furthermore, about 700 fjt layers of ITO were formed by sputtering on the amorphous silicon thin film 13B to form a transparent electrode.

As a result of current-voltage measurement of the solar cell obtained as described above using a solar simulator with AMI: 100 W/c layer 2, Voc was 0.87 volts, Js
c is 18.1mA/c+s2. FF is 0.70
The photoelectric conversion efficiency η was as good as 9.8%.

In addition, when we measured the surface reflection characteristics of this solar cell, we found that
It was found that the reflectance was reduced over the entire wavelength range, indicating that optical confinement was achieved.

According to the first to second embodiments described above, there are the following effects.

■The uneven shape formed on the surface of the substrate 11 is a pyramid-shaped etch bit of crystalline silicon (the unevenness of several thousand people).
Since it is used as a matrix, the shape is uniform.

(2) An original plate (crystalline silicon wafer 15) equipped with crystalline silicon pyramid-shaped etch bits can be used as the master mold for (2) above, and the reproducibility of the uneven shape formed on the surface of the substrate 11 is good.

(2) By adjusting the shape of the pyramid-shaped etch bit of crystalline silicon, the uneven shape formed on the surface of the substrate 11 can be easily controlled.

(2) As a result of (1) to (2) above, incident sunlight is effectively confined within the solar cell, and a solar cell with high photoelectric conversion efficiency can be constructed even if the film thickness is thinner than usual.

■The semiconductor layer that performs photoelectric conversion is a polycrystalline silicon thin film 13
In the case of A, polycrystalline silicon thin film solar cell lO
can achieve optical confinement. Furthermore, due to the presence of the uneven structure provided on the surface of the substrate 11, the polycrystalline silicon thin film 13
The adhesion of A is improved, and the manufacturability of solar cells is improved.

■The semiconductor layer that performs discharge conversion is an amorphous silicon thin film 13
In the case of B, the amorphous silicon thin film solar cell 20
can achieve optical confinement.

[Effects of the Invention] As described above, according to the present invention, an uneven shape with good reproducibility and controllability can be formed on the substrate surface, and a solar cell with high photoelectric conversion efficiency can be constructed.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the manufacturing process of a polycrystalline silicon thin film solar cell according to a first embodiment of the present invention, and FIG. 2 is a schematic diagram showing the manufacturing process of a polycrystalline silicon thin film solar cell according to a second embodiment of the present invention. FIG. 0.20.30...Solar cell. l...Substrate. 2... Road side L 3A... Polycrystalline silicon thin l1l (semiconductor layer), 3B
...Amorphous silicon thin film (semiconductor layer), 4...IT
O (transparent conductive film). Agent Patent Attorney Osamu Shiokawa Diagram (A) (C) 0m Genrigen 115 Diagram

Claims (2)

[Claims] (1) After chemically treating crystalline silicon having a (100) crystal orientation to form etch bits on the surface of the crystalline silicon, the pattern of the etch bits is transferred to the surface of low melting point glass under heating. A method for manufacturing a solar cell substrate, characterized in that: (2) a substrate formed by transferring crystalline silicon etch bits onto the surface of low-melting point glass; a transparent conductive film provided on the surface of the substrate on which the etch bits are formed; and a transparent conductive film provided on the surface of the transparent conductive film. a semiconductor layer that performs photoelectric conversion;
A solar cell comprising a conductive film provided on the surface of the semiconductor layer.