JP2001177133A - Method of manufacturing hybrid thin-film photoelectric transduser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a hybrid silicon-based thin-film photoelectric transducer device by which the properties of the device can be improved. SOLUTION: The hybrid thin-film photoelectric transducer device comprises a transparent electrode 2, an amorphous photoelectric transducer unit 11, a crystalline photoelectric transducer unit 12, and rear face electrode 13, which are formed on a transparent insulation substrate 1 in this order. The amorphous photoelectric transducer unit 11 comprises a p-type amorphous layer 111, an i-type amorphous photoelectric transducer layer 112A, an i-type transition layer 112B, and an n-type fine crystal layer 113, which are deposited by a plasma CVD in this order. The gas mixing ratio of a hydrogen dilution gas to a silane- based material gas is five times at most while the amorphous photoelectric transducer layer 112A is deposited and the same ratio is at least five times, while the transition layer 112B is deposited and fifty times or above when the deposition of the transition layer 112B is finished. The transition layer is deposited in a depth between 5 nm and 30 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor thin film photoelectric conversion device, and more particularly to a method of improving the performance of a hybrid silicon-based thin film photoelectric conversion device.

[0002]

2. Description of the Related Art In general, a semiconductor thin-film photoelectric conversion device has a first electrode, at least one semiconductor thin-film photoelectric conversion unit, and a second thin-film photoelectric conversion unit which are sequentially laminated on an insulating substrate at least on the surface.
Includes electrodes. Then, one photoelectric conversion unit includes an i-type layer sandwiched between a p-type layer and an n-type layer. The i-type layer occupying most of the thickness of the photoelectric conversion unit is a substantially intrinsic semiconductor layer, and the photoelectric conversion action mainly occurs in the i-type layer.

Therefore, regardless of whether the p-type and n-type conductive layers included therein are amorphous or crystalline, a photoelectric conversion unit having an amorphous i-type photoelectric conversion layer has an amorphous structure. A unit in which the i-type layer is crystalline is called a crystalline unit. In the specification of the present application, the terms “polycrystalline”, “microcrystalline”, and “crystalline” are partially amorphous as generally used in the technical field of a thin film photoelectric conversion device. It shall mean a state including a state.

On the other hand, the p-type or n-type conductive layer plays a role of generating a diffusion potential in the photoelectric conversion unit, and one of the important characteristics of the photoelectric conversion device depends on the magnitude of the diffusion potential.
The value of the open-circuit voltage also depends. However, these conductive type layers are inactive layers that do not directly contribute to photoelectric conversion, and light absorbed by impurities doped in the conductive type layers is a loss that does not contribute to power generation. In particular, light loss in the conductive layer on the light incident side is an important issue, and as a material having as little light absorption loss as possible for this conductive layer,
For example, an alloy material having a wide energy band gap, such as p-type amorphous silicon carbide, is used.

Here, when the thin film photoelectric conversion device is formed on a transparent insulating substrate such as a glass plate, the substrate can serve as a cover glass for protecting the surface of the photoelectric conversion device. In general, a p-type layer, an i-type photoelectric conversion layer, and an n-type layer are often stacked on a glass substrate via a transparent electrode.

As a method of improving the conversion efficiency of a thin film photoelectric conversion device, there is a method of stacking two or more photoelectric conversion units to form a tandem type. In this method,
A front unit including a photoelectric conversion layer having a large band gap is disposed on the light incident side of the photoelectric conversion device, and a rear band unit having a smaller band gap (for example, Si-G
By arranging the rear unit including the photoelectric conversion layer (of the e-alloy), it is possible to perform photoelectric conversion over a wide wavelength range of the incident light, thereby improving the conversion efficiency of the entire device. Among tandem type thin film photoelectric conversion devices,
A laminate of an amorphous photoelectric conversion unit and a crystalline photoelectric conversion unit is called a hybrid thin-film photoelectric conversion device.

For example, the wavelength of light that can be photoelectrically converted by i-type amorphous silicon is up to about 800 nm on the long wavelength side, while i-type crystalline silicon has a wavelength of about 100 nm which is longer than that.
It is possible to photoelectrically convert light having a wavelength of about 0 nm. Therefore, when a hybrid thin-film photoelectric conversion device is formed on a glass substrate, usually, a transparent electrode, an amorphous unit, a crystalline unit, and a back electrode are laminated on the glass substrate in this order.

[0008]

SUMMARY OF THE INVENTION Such a hybrid thin film photoelectric conversion device is a single type thin film photoelectric conversion device including either a single amorphous photoelectric conversion unit or a single crystalline photoelectric conversion unit. In comparison, it can exhibit significantly higher photoelectric conversion efficiency. However, even in the hybrid type thin film photoelectric conversion device having such high performance, there is still room for further performance improvement.

Accordingly, an object of the present invention is to provide a method for manufacturing a hybrid thin-film photoelectric conversion device having further improved photoelectric conversion characteristics.

[0010]

According to the present invention, there is provided a hybrid thin-film photoelectric conversion device including a transparent electrode, an amorphous photoelectric conversion unit, a crystalline photoelectric conversion unit, and a back electrode sequentially laminated on a transparent insulating substrate. The method of manufacturing the device includes the steps of: forming an amorphous photoelectric conversion unit by plasma CVD;
An amorphous p-type layer, an amorphous i-type photoelectric conversion layer, an i-type transition layer, and a microcrystalline n-type layer are sequentially deposited by a method, and a silane-based source gas is deposited during the deposition of the amorphous photoelectric conversion layer. The mixing ratio of the hydrogen diluting gas is reduced to 5 times or less, and the gas mixture ratio during the deposition of the transition layer is at least greater than 5 times, and at least at the substantial end of the deposition of the transition layer.
The transition layer is characterized by being deposited to a thickness in the range of 5 to 30 nm.

The mixture ratio of the hydrogen diluent gas to the silane source gas may be increased continuously or stepwise during the deposition of the transition layer. Further, the microcrystalline n-type layer has a thickness of 5 to 10 n.
Preferably, it is deposited to a thickness in the range of m.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the schematic sectional view of FIG. 1, as a specific example of the embodiment of the present invention, a method of manufacturing a hybrid type thin film photoelectric conversion device according to some examples will be described. This will be described below together with the comparative example.

(Example 1) A hybrid thin-film solar cell as shown in FIG. 1 was manufactured in Example 1. First, a glass plate was used as the transparent insulating substrate 1. On the glass substrate 1, a transparent conductive oxide (TC
O) as the front transparent electrode 2 made of O)
SnO ₂ film is formed by a thermal CVD method. Note that TC
It goes without saying that ITO (indium tin oxide), ZnO or the like can be used as O.

On the transparent electrode 2, an amorphous photoelectric conversion unit 11, a crystalline photoelectric conversion unit 12, and a back electrode 13 are laminated in this order. Amorphous photoelectric conversion unit 1
1 is a 10 nm-thick film sequentially deposited by a plasma CVD method.
P-type amorphous silicon carbide layer 111 having a thickness of 335
nm i-type amorphous silicon photoelectric conversion layer 112A, thickness 1
5 nm i-type silicon transition layer 112B and thickness 10
nm n-type microcrystalline silicon layer 113 is included. The crystalline photoelectric conversion unit 12 includes a 10-nm-thick p-type microcrystalline silicon layer 121 sequentially deposited by a plasma CVD method,
2.5 μm-thick i-type crystalline silicon photoelectric conversion layer 12
2, and an n-type microcrystalline silicon layer 123 having a thickness of 10 nm
Contains. The back electrode 13 includes a ZnO layer 131 having a thickness of 90 nm and an Ag layer 132 having a thickness of 300 nm, which are sequentially deposited by sputtering and vapor deposition. Note that ZnO
It goes without saying that the layer 131 may be formed of another TCO material, and the Ag layer 132 may be formed of another metal material. Here, the TCO layer 131 functions to maintain the lower surface of the metal layer 132 at a high reflectance and to prevent metal atoms from diffusing into the photoelectric conversion unit 12.

The p-type amorphous silicon carbide layer 111 included in the amorphous photoelectric conversion unit is deposited by plasma CVD as described above, but may be formed by any other known deposition method. .

The non-doped i-type amorphous silicon photoelectric conversion layer 112A was deposited under the following conditions. That is, only silane is used as a source gas introduced into the plasma CVD reaction chamber, and the pressure in the reaction chamber is 67 Pa (0.
5 Torr). The RF power density is 1
At 5 mW / cm ² , the film formation temperature was 200 ° C.

The deposition conditions for the non-doped silicon transition layer 112B are as follows: silane and hydrogen are used as source gases introduced into the plasma CVD reaction chamber, and the photoelectric conversion is performed only when the flow ratio of hydrogen to silane is increased by 60 times. It was different from the case of the layer 112A.

On the other hand, the n-type microcrystalline silicon layer 113 deposited on the transition layer 112B was deposited under the following conditions. That is, silane, phosphine, and hydrogen are used as source gases introduced into the plasma CVD reaction chamber, and the flow rate ratio of these gases is set to 0.01 times for phosphine and 80 times for hydrogen with respect to silane. Was. The pressure in the reaction chamber was 133 Pa (1 Torr), the RF power density was 75 mW / cm ² , and the film formation temperature was 200
° C was set.

The p contained in the crystalline photoelectric conversion unit 12
The type microcrystalline silicon layer 121 was formed under the following conditions. That is, silane, diborane, and hydrogen are used as source gases introduced into the plasma CVD reaction chamber, and the flow rate ratio of these gases is set such that diborane is 0.005 times that of silane and hydrogen is 100 times that of silane. Was.
The pressure in the reaction chamber was 133 Pa and the RF power density was 3 Pa.
0 mW / cm ² and the film formation temperature were set to 200 ° C.

The non-doped i-type crystalline silicon photoelectric conversion layer 122 was deposited under the following conditions. That is, silane and hydrogen were used as source gases introduced into the plasma CVD reaction chamber, and the flow ratio of hydrogen to silane was increased by a factor of 80. The pressure in the reaction chamber is 266P
a (2 Torr), RF power density is 75 mW / c
m ² , and the film formation temperature were set to 200 ° C.

The n-type microcrystalline silicon layer 123 on the crystalline photoelectric conversion layer 122 was deposited under the same conditions as the n-type microcrystalline silicon layer 113.

The hybrid thin-film solar cell of Example 1 manufactured as described above was irradiated with AM1.5 light at 100 mW using a solar simulator as incident light 3.
Regarding the photoelectric conversion characteristics when irradiated at an energy density of 1 / cm ² , the open-circuit voltage is 1.36 V, the short-circuit current density is 12.2 mA / cm ² , the fill factor is 75.6%, and the conversion efficiency is 12. 7%.

Comparative Example 1 Amorphous Silicon Photoelectric Conversion Layer 1
A hybrid thin-film solar cell was produced as Comparative Example 1 under the same conditions as in Example 1 except that 12A was formed to a thickness of 350 nm and the formation of the transition layer 112B was omitted. In the output characteristics when the solar cell of Comparative Example 1 was irradiated with light under the same conditions as in Example 1,
Open-end voltage is 1.28V, short-circuit current density is 10.5mA
/ Cm ² , fill factor 61.3%, and conversion efficiency 8.2%.

(Comparison between Example 1 and Comparative Example 1)
As is clear from the comparison between Comparative Example 1 and Non-doped silicon transition layer 112B,
It can be seen that the provision of an intervening layer between 12A and the n-type microcrystalline silicon layer 113 significantly improves the photoelectric conversion efficiency of the hybrid thin-film solar cell. This can be understood as follows.

In the prior art, when an n-type microcrystalline silicon layer is to be formed directly on an i-type amorphous silicon layer, crystallization does not easily occur in the n-type silicon layer. In order to achieve this, it is necessary to increase the thickness of the n-type layer. Therefore, it is considered that in Comparative Example 1, microcrystallization was insufficient because the thickness of the n-type layer was not sufficient, and as a result, the photoelectric conversion characteristics were inferior.

Conversely, when the thin non-doped silicon transition layer 112B is formed as in the first embodiment, the transition layer 112B is formed near the interface 1S with the n-type layer 113 shown in FIG. A crystal nucleus is generated. Since these crystal nuclei in the transition layer 112B at the interface 1S can serve as seeds for microcrystal growth in the n-type layer 113, it is considered that the n-type layer 113 can be easily microcrystallized even if its thickness is small. .
The n-type layer thus microcrystallized has a lower resistivity than the amorphous n-type layer. In addition, n which is sufficiently microcrystallized
The mold layer 113 can also act to improve the crystallinity of the crystalline photoelectric conversion unit 12 deposited thereon. Further, since the transition layer 112B has a small thickness, the nucleation layer is also thin, and since most of the transition layer 112B is a non-doped amorphous layer, it can be an active layer that can directly contribute to photoelectric conversion. According to the various effects provided by the transition layer 112B as described above, the first embodiment
It is considered that the hybrid thin-film solar cell of the present invention has remarkably improved in all of various photoelectric conversion characteristics as compared with Comparative Example 1.

(Examples 2 and 3 and Comparative Example 2) Example 2
And 3 and Comparative Example 2 were fabricated in the same manner as in Example 1, and the silicon transition layer 1
The difference is only that the film thickness of 12B was variously changed. In these examples and comparative examples, the total thickness of the amorphous photoelectric conversion layer 112A and the transition layer 112B was maintained at 350 nm. The open-circuit voltage (V) which is the output characteristic when the solar cells of Examples 2 and 3 and Comparative Example 2 are irradiated with light in the same manner as in Example 1
oc), short circuit current density (Jsc), and fill factor (F.
F. ) And conversion efficiency, the results as shown in Table 1 were obtained. Note that, in Table 1, Example 1
And the results of Comparative Example 1 are also shown.

[0028]

[Table 1]

As can be seen from Table 1, when the thickness of the transition layer 112B is too large as in Comparative Example 3, microcrystallization occurs in the vicinity of the interface 1S, and the amorphous region and the microcrystalline region Is locally mixed, resulting in a film having an incomplete structure, which deteriorates the transport characteristics of carriers generated by photoelectric conversion and partially reduces the function as a photoelectric conversion active layer. As a result, the photoelectric conversion efficiency of the solar cell is lower than in Examples 1 to 3.
As can be seen from the above examination results in Table 1, the thickness of the transition layer 112B is preferably set in the range of 5 to 30 nm.

(Examples 4 to 7 and Comparative Examples 3 and 4) Hybrid thin-film solar cells according to Examples 4 to 7 and Comparative Examples 3 and 4 were manufactured in the same manner as in Example 1, and amorphous photoelectric conversion was performed. The only difference is that the flow rate ratio of hydrogen to silane during the deposition of layer 112A and transition layer 112B was varied. In Table 2, the photoelectric conversion characteristics of the hybrid thin-film solar cells according to Examples 4 to 7 and Comparative Examples 3 and 4 are shown, and the photoelectric conversion characteristics of the solar cell of Example 1 are also shown. .

[0031]

[Table 2]

As can be seen from Table 2, when the flow rate ratio of hydrogen to silane is 20 times, which is less than 50 times, during the deposition of the transition layer 112B as in Comparative Example 3, sufficient photoelectric conversion characteristics are obtained. I can't. This is considered to be because the transition layer 112B could not generate sufficient crystal nuclei even in the vicinity of the interface 1S due to the low hydrogen dilution rate, and the microcrystallization of the n-type layer 113 became insufficient. Can be On the other hand,
As in Comparative Example 4, during the deposition of the amorphous photoelectric conversion layer 112A, the flow ratio of hydrogen to
If the value is 0, it is considered that the photoelectric conversion layer 112A itself did not become completely amorphous but became a film in which crystal nuclei were mixed. Therefore, it is considered that the photoelectric conversion function is reduced due to the non-uniformity in the photoelectric conversion layer 112A, and the smooth flow of the carrier is inhibited, so that the photoelectric conversion efficiency is significantly reduced.

Example 8 A hybrid thin-film solar cell of Example 8 was manufactured under the same conditions as in Example 1 except for the film formation conditions mentioned below.

That is, the non-doped i-type amorphous silicon photoelectric conversion layer 112A was deposited to a thickness of 320 nm. The non-doped silicon transition layer 112B has a flow rate ratio of hydrogen to silane of 1 up to an intermediate film thickness of 20 nm.
Deposition was performed under 0 times, and thereafter, until a final film thickness of 30 nm, the flow ratio of hydrogen to silane was deposited under 60 times.

The output characteristics when the hybrid thin-film solar cell according to the eighth embodiment is irradiated with light in the same manner as in the first embodiment have an open-circuit voltage of 1.38.
V, short-circuit current density was 12.5 mA / cm ² , fill factor was 75.5%, and conversion efficiency was 13.0%.

Example 9 A hybrid thin-film solar cell according to Example 9 was produced under the same conditions as in Example 1 except for the film formation conditions mentioned below.

That is, the amorphous silicon photoelectric conversion layer 11
2A was deposited to a thickness of 320 nm. Transition layer 112
B is deposited at a flow rate ratio of hydrogen to silane of 10 times under the initial thickness of 15 nm, at a flow rate of hydrogen to silane of 20 times at the intermediate thickness of 25 nm thereafter, and thereafter. Until the final film thickness of 30 nm was deposited, the flow ratio of hydrogen to silane was 60 times lower.

The output characteristics when the hybrid thin-film solar cell according to the ninth embodiment is irradiated with the same light as in the first embodiment have an open-circuit voltage of 1.40 V and a short-circuit current density of 12.5 mA. / Cm ² and fill factor of 76.
4% and the conversion efficiency was 13.4%.

Examples 8 and 9 and Example 1 as described above
As can be seen from the comparison, the photoelectric conversion efficiency is further improved by gradually increasing the mixing ratio of hydrogen to silane during the deposition of the transition layer 112B.
It goes without saying that the mixing ratio of hydrogen to silane may be continuously increased during the deposition of the transition layer 112B.

[0040]

As described above, according to the manufacturing method of the present invention, the photoelectric conversion characteristics of the hybrid type thin film photoelectric conversion device can be further improved.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a method for manufacturing a hybrid thin-film photoelectric conversion device according to an embodiment of the present invention.

[Explanation of symbols]

1 Substrate such as glass, 2 Transparent electrode such as SnO ₂ , 3
Incident light, 11 amorphous photoelectric conversion unit, 12 crystalline photoelectric conversion unit, 13 back electrode, 111p-type amorphous silicon-based layer, 112A non-doped amorphous silicon-based photoelectric conversion layer, 112B non-doped silicon-based transition layer,
113 n-type crystalline silicon-based layer, 1S transition layer 112
Interface between B and n-type layer 113, 121 p-type crystalline silicon-based layer, 122 non-doped crystalline silicon-based photoelectric conversion layer, 123 n-type crystalline silicon-based layer, 131 ZnO
And a metal film such as 132 Ag.

Claims (3)

[Claims] 1. A method of manufacturing a hybrid thin-film photoelectric conversion device including a transparent electrode, an amorphous photoelectric conversion unit, a crystalline photoelectric conversion unit, and a back electrode sequentially laminated on a transparent insulating substrate, the method comprising: An amorphous p-type layer, an amorphous i-type photoelectric conversion layer, an i-type transition layer, and a microcrystalline n-type layer are sequentially deposited by a plasma CVD method to form a crystalline photoelectric conversion unit; During the deposition of the porous photoelectric conversion layer, the gas mixture ratio of the hydrogen diluent gas to the silane-based source gas is set to 5 times or less, and the gas mixture ratio during the deposition of the transition layer is at least larger than 5 times, A method according to claim 1, characterized in that at least at the substantial end of the deposition of the transition layer, it is increased by a factor of 50 or more, and the transition layer is deposited to a thickness in the range of 5 to 30 nm. 2. The method according to claim 1, wherein the gas mixture ratio is increased continuously or stepwise during the deposition of the transition layer. 3. The method according to claim 1, wherein the microcrystalline n-type layer is deposited to a thickness in a range of 5 to 10 nm.