JPH03280475A - Manufacture of photoelectric conversion device - Google Patents

Abstract

PURPOSE:To prevent a photoelectric conversion device from deteriorating in initial conversion efficiency by a method wherein a low temperature layer is formed on a first impurity semiconductor layer, an intrinsic semiconductor layer is formed at a temperature higher than the film forming temperature of the low temperature layer to serve as a high temperature layer, and a second impurity semiconductor layer is formed. CONSTITUTION:A P layer 3 of a-SiC:H is formed as thick as 250Angstrom or so on a transparent electrode 2, for instance, of SnO2 on a glass substrate 1. In succession, a low temperature I layer 4 of a-Si:H is formed as thick as 4000Angstrom on the P layer 3. The glass substrate 1 is kept at a temperature of 20 deg.C identical to that when the P layer 3 is formed. Other conditions are as follows: gas flow rate of SiH4 is 10sccm; reaction pressure is 0.3Torr; and RF power is 50mW/cm2. In succession, a high temperature layer 5 of a-Si:H is formed as thick as 1000Angstrom at a substrate temperature of 320 deg.C. An N layer 6 of micro- crystallized a-Si:H is formed on the layer 5 as thick as 300Angstrom . Lastly, a back electrode 7 of metal is formed on the N layer 6.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a method for manufacturing a charge conversion device such as a solar cell, and in particular, the present invention relates to a method for manufacturing a charge conversion device such as a solar cell.
The present invention relates to a method of manufacturing a photoelectric conversion device made of a non-single crystal semiconductor in which an intrinsic semiconductor layer (i-layer) is provided between layers.

[Prior Art] Photoelectric conversion devices made of non-single crystal semiconductors are said to have poor stability. Particularly in the case of amorphous silicon solar cells, there is a phenomenon called the 5taebler-Wronski effect. That is, the conductivity of the i-layer, which is the active layer, of the device consisting of the p-layer, i-layer, and n-layer gradually decreases due to light irradiation, the carrier transport ability decreases, and the conversion efficiency of the device decreases.

Therefore, attempts have been made to increase the electric field strength of this layer by making the i-layer thinner. The attempt is made to suppress the deterioration of the device by increasing the carrier transport ability in advance.

Also, attempts have been made to connect a plurality of elements each consisting of a p-layer, a single-layer, and an n-layer in tandem to thin the i-layer of the light-receiving surface side element. By adopting such a tandem structure, it is thought that the deterioration of the light-receiving side element is suppressed due to the thinning of the i-layer, and the deterioration of the back side element is suppressed because it is irradiated with only long wavelength light. .

[Issue 8 to be solved by the invention] Even with the adoption of the above-mentioned i-layer thinning technology and tandem structure, the deterioration of solar cells is not sufficiently suppressed, and the rate of deterioration of photoelectric conversion efficiency when used outdoors for one year is More than 15% of respondents had problems.

Now, it is considered that forming the i-layer between the p-layer and the n-layer at a high temperature is effective in suppressing deterioration. However, the present inventors have discovered that simply forming the i-layer at a high temperature during the solar cell manufacturing process significantly reduces the initial conversion efficiency. It is thought that when the i-layer is formed on the p-layer at high temperature, impurities in the 0-layer diffuse into the i-layer and a surface active layer is generated at the p/i interface, which reduces the initial conversion efficiency. It will be done.

The present invention relates to a photoelectric conversion device made of a non-single crystal semiconductor in which an intrinsic semiconductor layer is provided between two impurity semiconductor layers of different conductivity types, and a manufacturing method that suppresses deterioration while preventing a decrease in initial conversion efficiency. The purpose is to provide

[Means for Solving the Problems] A method for manufacturing a photoelectric conversion device according to the present invention includes forming a film on a first impurity semiconductor layer (p layer or n layer) at a temperature equal to or lower than the film formation temperature of this layer. An intrinsic semiconductor is formed into a film to form a low-temperature i-layer, an intrinsic semiconductor is further formed at a temperature higher than the film-forming temperature of the low-temperature i-layer to form a high-temperature i-layer, and then a second impurity semiconductor layer (n-layer or p layer) is formed.

High school 7! ! The film formation temperature of the i-layer is set to be 200° C. or higher and 400° C. or lower.

Regarding the thickness of the i-layer, the thickness of the low-temperature i-layer is 300 Å or more and 4000 Å or less, and the sum of the thicknesses of the low-temperature i-layer and the high-temperature i-layer is 4000 Å or more and 7000 Å or less.

[Function] According to the method according to the present invention, a low-temperature i-layer is formed on the first impurity semiconductor layer. Since the latter film-forming temperature is equal to or lower than the former film-forming temperature, impurities do not diffuse from the first impurity semiconductor layer into the low-temperature first layer when forming the low-temperature i layer. Moreover, it is low! Since the high temperature i layer is formed after improving the heat resistance and plasma resistance of the surface by forming the ii layer, there is no diffusion of impurities into the high temperature 1 layer.

Therefore, a decrease in initial conversion efficiency can be prevented.

Further, the high if layer has stable carrier transport ability even when exposed to light irradiation, and deterioration is suppressed.

[Example] FIG. 1 is a cross-sectional view of a solar cell with an effective area of 1.0 cm 2 (1.0 cm×1° Ocm) manufactured by a method according to an example of the present invention. However, it is appropriate to use a parallel plate capacitively coupled glow discharge device for forming each 1'-conductor layer.

First, a p layer (made of a-3iC:H) (
3) will be deposited by 250 people. The gas flow rate supplied to the glow discharge device is 5 scc m s for SiH4 and 15 m s for CH4.
sc cms B2 Ha (1000ppml(
2 dilution product) is 15 seconds and %H2 is 50 seconds. Other conditions were reaction pressure 1, OTorr, substrate temperature 200° C., and RF power 50 mW/cm 2 .

Next, a low-temperature single layer (
4) will be deposited by 4,000 people. The substrate temperature is 200° C., which is the same as in the case of forming the p-layer (3).

Other film forming conditions were S t H4 gas flow m 10 s
ccm, reaction pressure 0.3Torr, RF power 50
mW/cm2.

Subsequently, a high-temperature i-layer (5) made of a-Si:H and having a thickness of 100 μm is formed at a substrate temperature of 320″C.

Other film forming conditions are the same as for the low temperature i-layer (4).

On top of this high-temperature i-layer (5), microcrystalline a-Si:H
300 people deposited an n-layer (6) consisting of:

The gas flow rate was 5 sccm for SiH4 and 5 sccm for PH3 (100 sccm).
0ppmH2 diluted product) is 101005c s H2 is 2
00 sec cm. Other conditions were reaction pressure 1.
0Torr, substrate temperature 200℃, RF power 500m
W/cm2.

Finally, a back electrode (7) made of metal is formed on the n-layer (8).

FIG. 2 is a graph showing the initial external characteristics (current-voltage characteristics) of the solar cell manufactured by the method described above. For the measurement, solar simulated light of AM-1, 100 mW/Cm2 was used.

Characteristic values are open circuit voltage 0.858volLs, short circuit current 16.06mA/cm %FF (fill factor)
The photoelectric conversion efficiency was 60.22%, and the photoelectric conversion efficiency was 8.302%. The rate of deterioration of charging conversion efficiency when used outdoors for one year is 10
%, which significantly suppresses deterioration compared to conventional methods.

FIG. 3 is a sectional view showing a comparative example of a solar cell. a-5
This example is the same as the above example except that the entire i-layer (5) consisting of t:H and having a thickness of 5000 layers was formed at a high substrate temperature of 320°C. FIG. 4 shows the initial external characteristics of this comparative example. All characteristics are the same as in the above embodiment. Characteristic values are open circuit voltage Q, 8Q 6volts
, short circuit current 15.58mA/cm FF47.82
%, and the photoelectric conversion efficiency was 6.014%.

A comparison of both characteristics shows that initial external characteristics such as FF are improved by forming the low temperature i-layer (4) before forming the high-temperature i-layer (5). In particular, a significant improvement in initial conversion efficiency is observed.

The film formation temperature of the p layer (3) is preferably 50°C or higher and 400°C or lower. The film formation temperature of the low-temperature i-layer (4) needs to be equal to or lower than the p-layer formation/desorption humidity, but it is 100°C.
Above, the temperature is preferably 300°C or less, more preferably 150°C or less.
℃ or higher and 250℃ or lower. The film-forming temperature of the high-temperature i-layer (5) is higher than the film-forming temperature of the low-temperature i-layer (4), and needs to be 200°C or more and 400°C or less.

The film thickness of the p layer (3) and n layer (6) is 80 Å or more, 30 Å
A suitable thickness is 0 Å or less. The film thickness of the low temperature i-layer (4) is 300
The thickness needs to be 500 Å or more and 4000 Å or less, preferably 500 Å or more and 4000 Å or less. High temperature i-layer (5
), the sum of the thickness of the low temperature i-layer (4) is 4000 Å.
As mentioned above, it is necessary to determine the thickness within a range of 7000 Å or less.

In addition, as a non-single crystal semiconductor constituting a photoelectric conversion device, S iSS t Cs S t N %S IG e
Hydrogenated alloy such as 5SiSn (for example, p layer (3) in the example)
Examples include amorphous silicon-based semiconductors commonly used in photovoltaic devices, such as a-9iC:H used for the i-layer (4, 5), a-3i:H) used for the i-layer (4, 5), and fluorinated alloys. It may be an amorphous semiconductor containing microcrystals, such as the one used for the n-layer (6) in the above embodiment, or a polycrystalline semiconductor. It is most preferable to arrange, on the light-receiving surface side, a p-layer (3) in which a-5iC:H is doped with an element of group MB of the periodic table, as in the above embodiment. However, an n-layer may be arranged on the light-receiving surface side, and in this case, it is optimal to use a-SiC:H doped with an element of group Vb of the periodic table.

Between the p layer (3) and the i layer (4, 5) or between the n layer (6) and 1
A layer whose optical forbidden band width and impurity concentration gradually decrease toward the i-layer (4, 5) may be provided between the layers (4, 5). The film thickness of this impurity semiconductor layer is 30 Å or more, 5
00 Å or less is suitable, more preferably 50 Å or more,
It is 200 Å or less.

In order to reduce the contact resistance between the impurity semiconductor layer (p-layer (3) or n-layer) on the light-receiving surface side and the transparent electrode (2), a high-conductivity layer of the same conductivity type as the impurity semiconductor layer on the light-receiving surface side is added. A concentration doping layer may also be provided. The thickness of this heavily doped layer is suitably 5 Å or more and 100 Å or less, more preferably 10 Å or more and 50 Å or less. The impurity concentration is
Appropriately, it is 5 times or more and 50 times or less as large as the impurity semiconductor layer on the light-receiving surface side.

When employing a two-stage tandem structure in which two elements each consisting of a p-layer, an i-layer, and an n-layer are connected in tandem, it is effective to apply the present invention to the elements on the side farther from the light-receiving surface.

[Effects of the Invention] As explained above, the manufacturing method according to the present invention is a method for manufacturing a photoelectric conversion device made of a non-single crystal semiconductor in which an intrinsic semiconductor layer is provided between two impurity semiconductor layers of different conductivity types. A low-temperature intrinsic semiconductor layer is formed by forming an intrinsic semiconductor on the first impurity semiconductor layer at a temperature equal to or lower than the film-forming temperature of this layer, and the film-forming temperature is higher than the film-forming temperature of the low-temperature intrinsic semiconductor layer. Since an intrinsic semiconductor is further formed at high temperature to form a high-temperature intrinsic semiconductor layer, and then a second impurity semiconductor layer is formed, it is possible to prevent the initial conversion efficiency of the photoelectric conversion device from deteriorating while preventing its deterioration. Can be suppressed. Therefore, according to the present invention, a highly efficient and highly reliable photoelectric conversion device can be manufactured.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a solar cell manufactured by the method according to an embodiment of the present invention, Fig. 2 is a graph showing the initial external characteristics of the thick vA1a cell shown in the previous figure, and Fig. 3 is a comparative example of the solar cell. The cross-sectional view, FIG. 4, is a graph showing the initial external characteristics of the solar cell shown in the previous figure. Explanation of symbols 1... Glass substrate, 2... Transparent electrode, 3... P layer, 4... Low temperature i layer, 5... High temperature i layer, 6... N layer, 7...・Back electrode.

Claims (1)

[Claims] 1. A method for manufacturing a photoelectric conversion device made of a non-single crystal semiconductor in which an intrinsic semiconductor layer is provided between two impurity semiconductor layers of different conductivity types, the method comprising: An intrinsic semiconductor is deposited at a temperature equal to or lower than the deposition temperature of this layer to form a low-temperature intrinsic semiconductor layer, and an intrinsic semiconductor is further deposited at a temperature higher than the deposition temperature of this low-temperature intrinsic semiconductor layer to form a high-temperature intrinsic semiconductor layer. A manufacturing method in which a second impurity semiconductor layer is formed after forming a semiconductor layer. 2. The film-forming temperature of the high-temperature intrinsic semiconductor layer is 200°C or higher, 40°C.
The manufacturing method according to claim 1, wherein the temperature is 0°C or lower. 3. The thickness of the low-temperature intrinsic semiconductor layer is 300 Å or more, 4000 Å or more.
3. The manufacturing method according to claim 1, wherein the total thickness of the low-temperature intrinsic semiconductor layer and the high-temperature intrinsic semiconductor layer is 4000 Å or more and 7000 Å or less.