JP4183688B2 - Method for manufacturing photoelectric conversion device and photoelectric conversion device - Google Patents

Description

  The present invention relates to a photoelectric conversion device, and more particularly to a method for manufacturing a photoelectric conversion device.

  A “plasma CVD apparatus” is known as an apparatus used for forming a semiconductor film in a manufacturing process such as a solar cell (photoelectric conversion apparatus). The plasma CVD apparatus includes a discharge electrode and a ground electrode disposed so as to face the discharge electrode in the film forming chamber. A substrate as an object to be processed on which a semiconductor film is deposited is held on a ground electrode. A board | substrate forms the transparent electrode which has the texture structure of surface unevenness, such as a tin oxide (SnO2), for example in the transparent glass plate. When a material gas containing a desired semiconductor layer material is introduced into the deposition chamber and an ultrahigh frequency power is applied to the discharge electrode, the material gas in the region between the discharge electrode and the substrate is in a plasma state. By activating the gas-phase material gas, a desired semiconductor film such as an amorphous silicon film is deposited on the substrate surface.

  It is desired to manufacture a solar cell module with high power generation efficiency at high speed by using such a plasma CVD apparatus. As a technique for improving the power generation efficiency, for example, a tandem structure in which a top cell made of amorphous silicon (a-Si) and a bottom cell made of microcrystalline silicon (microcrystalline Si) are formed in a laminated form is known. . The film formation conditions for the microcrystalline Si are greatly different from the conventional film formation conditions for a-Si. In order to improve the power generation efficiency (conversion efficiency), it is essential to further improve the quality of the microcrystalline Si film to be formed.

  In order to improve the film forming speed in the plasma CVD apparatus, it is conceivable to increase the super-high frequency power supplied to the discharge electrode. However, in this case, there has been a problem that the film quality of the formed thin film is deteriorated due to generation of higher order silane or increase of ion bombardment. That is, generally, the film forming speed and the conversion efficiency are in a trade-off relationship. In order to improve the productivity of the microcrystalline Si film that requires a film thickness of 1 μm or more, the higher the deposition rate, the better. Of course, the higher the conversion efficiency, the better. And it is most preferable to improve the film forming speed while maintaining high conversion efficiency.

  As a related technique, Patent Document 1 discloses a method for manufacturing a silicon-based thin film photoelectric conversion device. According to this technique, the i layer serving as the power generation layer of the photoelectric conversion layer is formed by the plasma CVD method under the following conditions. The substrate temperature is 550 ° C. or lower. The gas introduced into the reaction chamber of the plasma CVD apparatus includes a silane-based gas and a hydrogen gas, and the flow rate ratio of the hydrogen gas to the silane-based gas is 50 times or more. The pressure in the reaction chamber is set to 3 Torr or more. The film forming speed is set to 16 nm / min or more. In addition, the upper limit of the film forming speed was at most 65 nm / min (˜1.1 nm / sec). Also in the techniques disclosed in Patent Documents 2 to 4, the film forming speed is 1 to 3.9 μm / hour (˜1 nm / second), which is not high speed.

  Further, in the plasma CVD apparatus disclosed in Patent Document 5, the distance between the pair of plasma discharge electrodes is set so that the distance between the substrate and the cathode is 1 mm to 1 cm. The purpose of this is to contain the discharge region between the substrate and the cathode under high pressure, as described in Patent Document 5, and to prevent the generation of powder. It was necessary to set the distance between 1 mm and 1 cm. There is no technical meaning to improve the efficiency by reducing the distance between the electrodes, and it is derived from the configuration of this plasma CVD apparatus. This is because this plasma CVD apparatus does not use a ladder electrode as an electrode, and therefore, in order to maintain the discharge by the pair of plasma discharge electrodes, it is necessary to set the distance between the substrate and the cathode within the above range. That is, the above configuration is an essential requirement for establishing the plasma CVD apparatus described in Patent Document 5, and is clearly not based on special knowledge.

JP-A-11-145499 JP-A-11-330520 JP 2001-135838 A JP 2001-237189 A JP 2003-197536 A

  The objective of this invention is providing the manufacturing method of the photoelectric conversion apparatus which can improve the film forming speed | rate of an electric power generation layer (i layer), maintaining the conversion efficiency of the photoelectric conversion apparatus manufactured.

  [Means for Solving the Problems] will be described below using the numbers and symbols used in [Best Mode for Carrying Out the Invention]. These numbers and symbols are added in parentheses in order to clarify the correspondence between the description of [Claims] and [Best Mode for Carrying Out the Invention]. However, these numbers and symbols should not be used for the interpretation of the technical scope of the invention described in [Claims].

  The present invention is based on the results of finding that there is a large correlation between the film quality of the power generation layer formed by the plasma CVD method and the plasma generation method.

  According to the present invention, the photoelectric conversion device (1) is manufactured using the plasma CVD device (10) installed in the chamber (11) so that the discharge electrode (12) and the ground electrode (13) face each other. The The discharge electrode (12) is preferably a ladder electrode or the like. The manufacturing method according to the present invention includes (A) a step of placing a substrate (20) on which a p-layer is formed on the ground electrode (13) so as to face the discharge electrode (12), and (B) a substrate (20 ) And the discharge electrode (12) are set to a distance of less than 8 mm, (C) a step of heating to 180 to 220 ° C. by a heater built in the ground electrode, and (D) a chamber (11). A step of supplying a material gas (21) into the inside, (E) a step of setting the pressure in the chamber (11) to 600 Pa to 2000 Pa, and (F) a material gas supplying ultrahigh frequency power to the discharge electrode (12). (21) By converting into plasma, the method includes the steps of forming a power generation layer (5) on the substrate (20) and (G) forming an n layer on the power generation layer. The inventors of the present application have found that such a production method and production conditions can improve the film forming speed without reducing the conversion efficiency.

In the step (F), the power density of the supplied superhigh frequency power may be 3.0 kW / m ² or more. Further, the frequency of the supplied ultrahigh frequency power may be 60 MHz or more. The speed at which the power generation layer (5) is formed is 2 nm / s or more.

  In a photoelectric conversion device, a microcrystalline silicon film or a microcrystalline silicon germanium film needs to be thicker than an amorphous silicon film. Therefore, it is particularly preferable that a microcrystalline silicon film or a microcrystalline silicon germanium film is formed as the power generation layer in the step (F).

  When manufacturing a tandem solar cell (31), the manufacturing method according to the present invention includes (a) amorphous silicon with respect to the substrate (20), in addition to the step (F) for forming a microcrystalline silicon film. A step of forming a photoelectric conversion layer (consisting of a pin layer) made of a film is provided. This (a) process may be performed before the (F) process, and may be performed after the (F) process. Further, the step (a) may be performed under the same film forming conditions as those for forming the microcrystalline silicon film. When manufacturing a triple solar cell (41), the manufacturing method according to the present invention further includes (b) a step of forming a microcrystalline silicon germanium film on the substrate. This (b) process may be performed before the (F) process, and may be performed after the (F) process. The step (b) is performed under the same film forming conditions as those for forming the microcrystalline silicon film. The manufacturing conditions according to the present invention mean substrate temperature, pressure, gap length, power density, and excitation frequency.

  According to the method for manufacturing a photoelectric conversion device according to the present invention, it is possible to improve the film forming rate of the power generation layer without reducing the conversion efficiency of the manufactured photoelectric conversion device.

  According to the method for manufacturing a photoelectric conversion device according to the present invention, the manufacturing cost is reduced.

  A method for manufacturing a photoelectric conversion device according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view schematically showing an example of a photoelectric conversion device manufactured in the present invention. The photoelectric conversion device 1 includes a glass substrate 2, a transparent electrode 3, a p layer 4, an i layer 5, an n layer 6, and a back electrode 7. The transparent electrode 3 is made of a transparent electrode material such as SnO ₂ (tin oxide): about 500 nm to 1000 nm, and is formed on the glass substrate 2. The p layer 4 is a p-type semiconductor layer, and the n layer 6 is an n-type semiconductor layer. The i layer 5 is, for example, a microcrystalline Si layer, and is formed so as to be sandwiched between the p layer 4 and the n layer 6. That is, the p layer 4, i layer 5, and n layer 6 form a pin junction and function as a photoelectric conversion layer. The film thicknesses of the p layer 4, i layer 5, and n layer 6 are, for example, about 20 to 50 nm, 1.2 to 1.6 μm, and about 20 to 50 nm, respectively. This photoelectric conversion layer is sandwiched between the transparent electrode 3 and the back electrode 7. As the back electrode 7, for example, Ag (silver) or Al (aluminum): about 200 to 500 nm can be used. In the case of Ag, it is desirable to stack Ti: about 10 to 30 nm on the surface to prevent alteration. Furthermore, a second transparent electrode (GZO: about 50 to 150 nm) may be added between the n layer 6 and the back electrode 7 to increase light reflection from the back electrode side.

  In such a photoelectric conversion device (solar cell) 1, sunlight 8 enters from the glass substrate 2 side. When the sunlight 8 is incident, pairs of electrons and holes are generated in the i layer 5. These holes and electrons are attracted to the transparent electrode 3 and the back electrode 7 by the electric field between the p layer 4 and the n layer 6. A current is taken out by connecting the transparent electrode 3 and the back electrode 7 with a predetermined wiring.

  FIG. 2 is a schematic diagram showing a configuration of a plasma CVD apparatus used for manufacturing the photoelectric conversion apparatus 1. The plasma CVD apparatus 10 includes a chamber 11 and a discharge electrode 12 and a ground electrode 13 installed in the chamber 11. The discharge electrode 12 and the ground electrode 13 are disposed so as to face each other. A heater 14 is connected to the ground electrode 13, and a substrate 20 as an object to be processed on which a semiconductor layer is deposited is held on the ground electrode 13. The discharge electrode 12 is connected to an ultrahigh frequency power supply 15, and the ultrahigh frequency power supply 15 supplies ultrahigh frequency power to the discharge electrode 12. A gas supply pipe 16 and a gas exhaust pipe 17 are provided at predetermined locations in the chamber 11.

  During the film forming process, a material gas 21 containing a desired semiconductor layer material is introduced into the chamber 11 from a gas supply source (not shown) through the gas supply pipe 16. Examples of the material gas 21 include a mixed gas of silane (SiH 4) gas and hydrogen (H 2) gas. By supplying ultrahigh frequency power from the ultrahigh frequency power supply 15 to the discharge electrode 12, the material gas 22 in the region between the discharge electrode 12 and the substrate 20 enters a plasma state. A desired semiconductor layer, for example, a microcrystalline silicon film is deposited on the surface of the substrate 20 by the plasma 22 thus generated. A vacuum pump (not shown) exhausts the gas after reaction through the gas exhaust pipe 17 and adjusts the pressure in the chamber 11.

  FIG. 3 shows the structure of the discharge electrode 12 used in the plasma CVD apparatus 10, and shows the structure seen from the direction A in FIG. The discharge electrode 12 is a “ladder electrode”. That is, the ladder electrode 12 includes a pair of first electrode rods 12a substantially parallel to each other and a plurality of second electrode rods 12b substantially parallel to each other. The first electrode rod 12a and the second electrode rod 12b are connected to be orthogonal to each other. That is, the pair of first electrode rods 12a and the plurality of second electrode rods 12b are combined in a ladder shape. The pair of first electrode rods 12a is formed with a plurality of feeding points 12c to which ultrahigh frequency power is supplied from the ultrahigh frequency power supply 15. The ladder electrode having such a structure has excellent characteristics in controlling the super-high frequency voltage and making the electric field distribution uniform. In addition to the circular cross section shown in FIGS. 2 and 3, the electrode rod shown here can be a quadrilateral, a rounded square face, an ellipse or the like, and does not particularly define the cross-sectional shape. 2 shows a general form in which the material gas is supplied from the direction opposite to the electrode substrate, but it is supplied from a gas supply device having many pores for more uniform supply. Alternatively, a material gas may be ejected from the inside of the electrode. Unlike the plasma CVD apparatus for forming the p layer 4, the i layer 5, and the n layer 6, each plasma CVD apparatus is configured such that the substrate can be transported in a vacuum via a transfer chamber. Yes. A plasma CVD apparatus for forming the p layer 4 and the n layer is not shown, but is the same as the plasma CVD apparatus 10 for forming the i layer.

  As shown in FIG. 2, the distance between the electrode rods (second electrode rods 12b) of the discharge electrode 12 is hereinafter referred to as “pitch p”. Further, the distance between the discharge electrode 12 and the substrate 20 is hereinafter referred to as “gap d”. In order to improve the uniformity of the film to be formed, it is preferable that the pitch p is smaller than the gap d.

  According to this Embodiment, the photoelectric converting layer (i layer 5) and the photoelectric converting apparatus 1 are manufactured using such a plasma CVD apparatus 10. FIG. The manufacturing process and manufacturing conditions are as follows.

FIG. 4 shows the overall flow of the manufacturing process of the photoelectric conversion layer according to the present invention. First, on the ground electrode 13 in the plasma CVD apparatus 10, the substrate 20 on which the p layer 4 is formed as an object to be processed is installed (step S1). In addition, a predetermined layer such as the transparent electrode 3 has already been formed on the substrate 20 as the object to be processed. As the p layer 4, a p-type microcrystalline silicon film was formed by a plasma CVD method. As for the film forming conditions, the plasma CVD apparatus was evacuated to 10 ⁻⁴ Pa or less in a plasma CVD apparatus different from the i layer 5 as the power generation layer, and then the substrate was heated to 150 ° C. Then, SiH ₄ and H ₂ as source gases and B ₂ H ₆ as a p-type impurity gas were introduced into the chamber at 3, 300 and 0.02 sccm, respectively, and the pressure was controlled to 67 Pa. The gap length is 25 mm. Then, plasma is generated between the discharge electrode and the substrate 20 by supplying an ultrahigh frequency power of 100 MHz-5 kW / m ² from the ultrahigh frequency power source to the discharge electrode, and p-type microcrystalline silicon is formed as a p layer 4 on the substrate 20. A layer was deposited to 20 nm. The substrate 20 on which the p layer 4 is formed in this manner is placed in the plasma CVD apparatus 10 so as to face the discharge electrode 12.

Next, the gap d between the discharge electrode 12 and the substrate 20 is set to 8 mm or less (step S2). Next, the board | substrate 20 is heated at 180-220 degreeC with the heater incorporated in the ground electrode (step S3). Subsequently, the material gas 21 is supplied into the chamber 11 through the gas supply pipe 16 (step S4). The material gas 21 is, for example, a mixed gas of silane (SiH ₄ ) gas and hydrogen (H ₂ ) gas. Next, the pressure P in the chamber 11 is set to 600 Pa or more (step S5). Next, by supplying ultrahigh frequency power from the ultrahigh frequency power supply 15 to the discharge electrode 12, the material gas 21 in the region between the discharge electrode 12 and the substrate 20 becomes a plasma state. The i layer 5 that is a power generation layer made of a desired semiconductor is formed on the surface of the object to be processed by the plasma 22 thus generated (step S6). The power generation layer (i layer 5) to be formed is an amorphous silicon film, a microcrystalline silicon film, a microcrystalline silicon germanium film, or the like.

Next, an n-type microcrystalline silicon film was formed as an n layer on the i layer by a plasma CVD method (step S7). As the film forming conditions, the chamber 20 was evacuated to 10 ⁻⁴ Pa or less in a plasma CVD apparatus different from the p layer 4 and the i layer 5, and then the substrate 20 was heated to 170 ° C. Then, SiH ₄ and H ₂ as source gases and PH ₃ as an n-type impurity gas were introduced into the chamber at ₃ , 300 and 0.1 sccm, respectively, and the pressure was controlled at 93 Pa. The gap length is 25 mm. Then, plasma is generated between the discharge electrode and the substrate 20 by supplying an ultrahigh frequency power of 60 MHz-1.5 kW / m ² from the ultrahigh frequency power source to the discharge electrode, and an n-type layer 3 is formed on the substrate 20 as an n-type layer 3. A microcrystalline silicon layer is formed to a thickness of 30 nm. In this manner, a photoelectric conversion layer made of pin was formed, and then Ag was formed as a GZO and back electrode 7 by sputtering to produce a photoelectric conversion device.

  The inventors of the present application have discovered that the film forming speed and the conversion efficiency of the manufactured photoelectric conversion device 1 can be improved simultaneously by the method and film forming conditions described above. Hereinafter, the result data of the experiment conducted by the inventors will be shown in detail.

In this experiment, a tandem solar cell (photoelectric conversion device) 31 as shown in FIG. 5 was produced. The tandem solar cell 31 includes a glass substrate 32, a first electrode 33 formed on the glass substrate 32, a first cell 34 formed on the first electrode 33, a GZO formed on the first cell 34, and the like. A transparent intermediate layer 37 made of a transparent electrode, a second cell 35 formed on the transparent intermediate layer 37, and a second electrode 36 formed on the second cell 35. A pin junction is formed in each cell. The first electrode 33 is a transparent electrode made of, for example, SnO ₂ . The first cell 34 is a top cell, for example, and is formed of amorphous silicon (a-Si). The second cell 35 is a bottom cell, for example, and is formed of microcrystalline Si. In this case, sunlight is incident from the glass substrate 32 side (substrate incident type). In addition, after the first cell 34 made of a-Si is formed, the second cell 35 made of microcrystalline Si is formed, and Ag or Al is formed as the GZO and the second electrode 36 so that the photoelectric conversion device 1 is formed. It is formed.

  The first cell 34 may be a bottom cell formed of microcrystalline Si, and the second cell 35 may be a top cell formed of a-Si. That is, the second cell 35 made of a-Si may be formed after the first cell 34 made of microcrystalline Si is formed. In this case, the second electrode 36 is a transparent electrode, and sunlight is incident from the second electrode 36 side (film surface incident type). In the film surface incidence type, a transparent electrode such as ITO or GZO is used as the second electrode, and the film thickness is 40 to 80 nm. Further, a collecting electrode made of Al, Ag or the like not shown is formed.

In producing the tandem solar cell 31 having such a structure, a microcrystalline Si film as the i layer 5 was formed under various different conditions. FIG. 6 shows the film forming conditions. Condition No. 1, the pressure P in the chamber 11, the gap d, the power density of the ultra high frequency power, the power frequency, the substrate temperature, and the H ₂ / SiH ₄ ratio are 400 Pa, 5.5 mm, 2-3 kW / m ² , respectively. It was set to 100 MHz, 180 ° C., and 20-23. Condition No. 2, pressure P, gap d, power density, power frequency, substrate temperature, H ₂ / SiH ₄ ratio are 533 Pa, 4.5 mm, 4 to 5 kW / m ² , 100 MHz, 180 ° C., 20 to 26, respectively. Was set to Condition No. 3, pressure P, gap d, power density, power frequency, substrate temperature, H ₂ / SiH ₄ ratio are 667 Pa, 3.5 mm, 4-5 kW / m ² , 100 MHz, 180 ° C., 18-22, respectively. Was set to Condition No. 4, pressure P, gap d, power density, power frequency substrate temperature, H ₂ / SiH ₄ ratio are 800 Pa, 3.5 mm, 5-6 kW / m ² , 100 MHz, 180 ° C., 19-21, respectively. Was set. The film thickness of the i layer 5 formed here is about 1.5 μm. Further, when this microcrystalline Si film is formed, a mixed gas of SiH ₄ / H ₂ is supplied as the material gas 21. The crystallization rate of microcrystalline Si is accurately controlled by the H ₂ dilution rate (H ₂ / SiH ₄ ratio) of SiH ₄ gas. A plurality of experiments were performed for each of the conditions shown in FIG. 6, and the “film formation rate” of the microcrystalline Si film and the “power generation efficiency (conversion efficiency)” of the manufactured tandem solar cell 31. Was measured.

FIG. 7 is a graph showing the “pressure dependency” of the film forming speed and the conversion efficiency. The horizontal axis indicates the measured film forming speed, and the vertical axis indicates the measured conversion efficiency. In FIG. 1 and the square indicates the condition no. 2 and the triangle indicates the condition No. 3 and diamonds indicate the condition No. 4 is shown. Further, as a comparative example, the result when the pressure P is set to 400 Pa but the power density is increased to 3 kW / m ² or more is indicated by black circles.

(First embodiment)
When the pressure P is set to 400 Pa (condition No. 1), a film forming speed of about 1.5 nm / s and a conversion efficiency of about 12.5% are realized. However, when the power density is increased to further improve the film forming speed (black circle in FIG. 7), a film forming speed of about 2.0 to 2.5 nm / s is realized, but the conversion efficiency is It has fallen. Conventionally, in order not to reduce the conversion efficiency, the upper limit value of the film forming speed was 1 nm / s at most. In order to significantly reduce the manufacturing cost, it is desirable to realize a film forming speed of “2 nm / s” or more. However, as shown in FIG. 7, when the pressure P is 400 Pa, the conversion efficiency decreases if the film forming speed is 2 nm / s or more.

(Second embodiment)
When the pressure P is set to 533 Pa (condition No. 2), a film forming speed of about 2.0 nm / s and a conversion efficiency of about 11.7 to 12.5% are realized. In this case, a film forming speed of 2.0 nm / s is realized. Condition No. The main reason why the film forming speed is increased compared to the case of 1 is an increase in power density. Conversely, it has been discovered that if the pressure P is set to 533 Pa, the conversion efficiency does not decrease so much even if the power density is increased.

(Third embodiment)
When the pressure P is set to 667 Pa (condition No. 3), a film forming speed of about 2.0 to 2.7 nm / s and a conversion efficiency of about 11.7 to 12.5% are realized. In this case, a maximum film forming speed of about 2.7 nm / s is realized. Condition No. The main reason why the film forming speed is increased compared to the case of 1 is an increase in power density. Conversely, it has been discovered that if the pressure P is set at 667 Pa, the conversion efficiency does not decrease even if the power density is increased. That is, it is possible to increase the film forming speed while maintaining high conversion efficiency.

(Fourth embodiment)
When the pressure P is set to 800 Pa (condition No. 4), a film forming speed of about 3.0 to 3.5 nm / s and a conversion efficiency of about 12.0 to 12.5% are realized. In this case, a maximum film forming speed of about 3.5 nm / s is realized. Condition No. The reason why the film forming speed is further increased as compared with the case of 3 is that the power density is further increased. Conversely, if the pressure P is set to 800 Pa, the power density can be further increased while maintaining high conversion efficiency (5 to 6 kW / m ² ). That is, it is possible to increase the film forming speed while maintaining high conversion efficiency. Under such conditions, it is considered that the deterioration of film quality due to the generation of higher order silane and the increase of ion bombardment is suppressed.

As described above, according to the present invention, when the photoelectric conversion layer is formed, the pressure P in the chamber 11 is set to 533 Pa or more. Preferably, the pressure P is set to 600 Pa or more. Thereby, even if the power density of the super-high frequency power is set higher than the conventional one, conversion efficiency does not decrease. For example, it is better to set the superhigh frequency power supplied to the discharge electrode 12 to 3.0 kW / m ² or more. In this case, a film forming speed of 2.0 nm / s or more is realized, and the conversion efficiency is not lowered. Since the film forming speed of about twice or more than the conventional one is realized, the film forming time is reduced to about half. In particular, in order to obtain a high-performance solar cell module, a microcrystalline Si film having a thickness of 1 μm or more is necessary, and it is preferable that the present invention is applied. Thus, according to this invention, it becomes possible to improve the conversion efficiency of the photoelectric conversion apparatus 1 manufactured, and to improve the film-forming speed | rate of an electric power generation layer. Moreover, since production efficiency improves, manufacturing cost is reduced. The upper limit of the pressure P in the chamber 11 is about 2000 Pa from the viewpoint of suppressing abnormal discharge, uniformity of gas flow distribution, and film quality deterioration due to excessive gas phase reaction.

FIG. 8 is a graph showing the gap dependency of the conversion efficiency. The horizontal axis shows the gap d, and the vertical axis shows the value (relative ratio) normalized by the measured conversion efficiency of 12.5%. In this experiment, the pressure P was set to 1333 Pa, the power density was set to 5 kW / m ² , and the power frequency was set to 60 MHz. The film forming speed was about 2 nm / s.

(5th Example)
When the gap d was set to 5 mm, 6 mm, 7 mm, and 10 mm, the relative ratios of the measured conversion efficiencies were 1.0, 1.01, 0.97, and 0.7, respectively. That is, there was a tendency that the conversion efficiency obtained decreased as the gap d increased. In order to realize a conversion efficiency relative ratio of 0.9 or more, as shown in FIG. 8, the gap d is preferably set to 8 mm or less. In each condition shown in FIG. 6, the gap d was set to 8 mm or less.

  FIG. 9 is a graph showing the “power density dependency” of the film forming speed and the conversion efficiency. The horizontal axis indicates the measured film forming speed, and the vertical axis indicates the measured conversion efficiency. In FIG. 9, a mark similar to the mark in FIG. 1-No. The measurement results for 4 are shown.

(Sixth embodiment)
As shown in FIG. 9, the film-forming speed is improved as the super-high frequency power supplied to the discharge electrode 12 at ² to 6 kW / m ² increases. Conventionally, when the supply power is increased, the conversion efficiency is lowered (see FIG. 7). However, according to the present invention, the conversion efficiency is kept substantially constant even when the supply power is increased. In particular, even if the power density is increased in order to realize a film forming speed of 2.0 nm / s or higher, high conversion efficiency is maintained. This is because, as described above, the pressure P in the chamber is set to 600 Pa, and the gap d is set to less than 8 mm. For example, the power density may be set to 3.0 kW / m ² or more. More preferably, the power density is set to 4.0 kW / m ² or more. As a result, a film forming speed of 2 nm / s or more is realized. Thereby, the production efficiency of the solar cell module is improved, and the manufacturing cost is reduced.

(Seventh embodiment)
FIG. 10 is a graph showing the “power frequency dependency” of the film forming speed and the conversion efficiency. The horizontal axis indicates the measured film forming speed, and the vertical axis indicates the value obtained by normalizing the measured conversion efficiency at 12.5%. In FIG. 10, a white circle indicates a case where the power frequency is 100 MHz, and a triangle indicates a case where the power frequency is 60 MHz. In this experiment, the pressure P was set to 1333 Pa, the gap d was set to 5 mm, and the power density was set to 4-6 kW / m ² .

  As shown in FIG. 10, the film forming speed tends to increase as the power frequency increases. The above condition No. 1-No. In 4, the power frequency was set to 100 MHz. Thereby, even if high conversion efficiency and high film forming speed are realized. Here, as shown in FIG. 10, it was confirmed that even when the power frequency was set to 60 MHz, a sufficiently high conversion efficiency and a sufficiently high film forming speed could be realized. Specifically, the same conversion efficiency as when the power frequency is 100 MHz is realized. In addition, a film forming speed of about 1.7 to 2.5 nm / s is realized. That is, a film forming speed of 2.0 nm / s or more can be realized while maintaining high conversion efficiency. This does not mean that the lower limit of the power frequency at which the above effect is obtained is 60 MHz. Similar results can be obtained even when the power frequency is 40 MHz.

  As described above, according to the manufacturing method and the manufacturing conditions according to the present invention, the film forming speed of the power generation layer to be manufactured is improved, and the conversion efficiency of the manufactured photoelectric conversion device is improved. According to the solar cell having the tandem structure shown in FIG. 5, since the short wavelength light is absorbed by the a-Si cell and the long wavelength light is absorbed by the microcrystalline Si cell, excellent power generation efficiency is realized. . Since the a-Si film absorbs light very well, a thickness of about 0.3 μm is sufficient. On the other hand, regarding the microcrystalline Si film, a film thickness of 1 μm or more is required to achieve high performance. Therefore, it is particularly preferable that the manufacturing method and manufacturing conditions according to the present invention are applied to the process for forming the microcrystalline Si film. Thereby, the production efficiency is particularly improved and the manufacturing costs are particularly reduced. Naturally, the manufacturing method and manufacturing conditions according to the present invention may be applied to the a-Si film forming process.

  Moreover, in the manufacturing process of the tandem solar cell 31 according to the present invention, the a-Si film forming process may be performed before or after the microcrystalline Si film forming process. . The order of the film forming process depends on the desired solar cell structure (substrate incident type, film surface incident type). Further, a transparent electrode may be further formed between the first cell 34 and the second cell 35.

(Eighth embodiment)
Furthermore, the manufacturing method and manufacturing conditions according to the present invention may be applied to a microcrystalline silicon germanium film (microcrystalline SiGe film). The manufacturing conditions according to the present invention mean substrate temperature, pressure, gap length, power density, and excitation frequency. For example, FIG. 11 is a cross-sectional view illustrating an example of a triple solar cell (photoelectric conversion device) 41. The triple solar cell 41 includes a glass substrate 42, a first electrode 43 formed on the glass substrate 42, a first cell 44 formed on the first electrode 43, and a second electrode formed on the first cell 44. A cell 45, a third cell 46 formed on the second cell 45, and a second electrode 47 formed on the third cell 46 are provided. A pin junction is formed in each cell. The first electrode 43 is a transparent electrode made of, for example, SnO ₂ . Further, for example, the first cell 44 is formed of a-Si, the second cell 45 is formed of microcrystalline Si, and the third cell 46 is formed of microcrystalline SiGe. Sunlight enters from the glass substrate 42 side (substrate incident type). In this case, after the a-Si film is formed, the microcrystalline Si film is formed, and then the microcrystalline SiGe film is formed.

  Further, the first cell 44 may be formed of microcrystalline SiGe, the second cell 45 may be formed of microcrystalline Si, and the third cell 46 may be formed of a-Si. Sunlight enters from the side of the second electrode 47 formed of a transparent electrode material (film surface incident type). In this case, after the step of forming the microcrystalline SiGe film, the step of forming the microcrystalline Si film is performed, and then the step of forming the a-Si film is performed. A transparent electrode may be further formed between the cells.

  In such a triple solar cell 41, the thickness of the microcrystalline Si film or microcrystalline SiGe film is larger than the thickness of the a-Si film. Therefore, it is particularly preferable that the manufacturing method and manufacturing conditions according to the present invention are applied to the process of forming the microcrystalline Si film and the microcrystalline SiGe film. Thereby, the production efficiency is particularly improved and the manufacturing costs are particularly reduced. Naturally, the manufacturing method and manufacturing conditions according to the present invention may be applied to the a-Si film forming process. The manufacturing conditions according to the present invention mean substrate temperature, pressure, gap length, power density, and excitation frequency.

  As explained above, according to the method for manufacturing a photoelectric conversion device according to the present invention, it is possible to improve the film forming speed of the power generation layer without reducing the conversion efficiency of the manufactured photoelectric conversion device. Become. This improves production efficiency and reduces manufacturing costs.

FIG. 1 is a cross-sectional view schematically showing the structure of a photoelectric conversion device. FIG. 2 is a schematic diagram illustrating a configuration of a plasma CVD apparatus used for manufacturing a photoelectric conversion apparatus. FIG. 3 is a plan view showing the structure of the ladder electrode in the plasma CVD apparatus. FIG. 4 is a flowchart showing a method for producing a photoelectric conversion layer according to the present invention. FIG. 5 is a cross-sectional view schematically showing the structure of the tandem solar cell. FIG. 6 is a table showing manufacturing conditions when the photoelectric conversion device according to the present invention is prototyped. FIG. 7 is a graph showing the pressure dependency of the film forming speed and the conversion efficiency. FIG. 8 is a graph showing the gap dependency of the film forming speed. FIG. 9 is a graph showing the ultrahigh frequency power dependence of the film forming speed and the conversion efficiency. FIG. 10 is a graph showing the power frequency dependence of the film forming speed and the conversion efficiency. FIG. 11 is a cross-sectional view schematically showing the structure of a triple solar cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoelectric conversion apparatus 2 Glass substrate 3 Transparent electrode 4 p layer 5 i layer 6 n layer 7 Back electrode 8 Sunlight 10 Plasma CVD apparatus 11 Chamber 12 Discharge electrode 13 Ground electrode 14 Heater 15 Superhigh frequency power supply 16 Gas supply pipe 17 Gas exhaust Tube 20 Substrate 21 Material gas 22 Plasma 31 Tandem solar cell 32 Glass substrate 33 First electrode 34 First cell 35 Second cell 36 Second electrode 37 Transparent intermediate layer 41 Triple solar cell 42 Glass substrate 43 First electrode 44 First 1 cell 45 2nd cell 46 3rd cell 47 2nd electrode

Claims (5)

A discharge electrode including a pair of first electrode rods that are substantially parallel to each other and a plurality of second electrode rods that are substantially parallel to each other so as to be orthogonal to the first electrode rods, and a ground electrode are opposed to each other in the chamber A method of manufacturing a photoelectric conversion device using a plasma CVD device installed to perform,
Placing a substrate on which a p-layer is formed on the ground electrode so as to face the discharge electrode;
Setting the distance between the substrate and the discharge electrode to less than 8 mm;
Setting the substrate temperature to 180 to 220 ° C. by a heater built in the ground electrode;
Supplying a mixed gas of SiH ₄ / H ₂ as a material gas into the chamber;
Setting the pressure in the chamber to 600 Pa to 2000 Pa;
An ultrahigh frequency power having a frequency of 40 MHz to 100 MHz and a power density of 3.0 kW / m ² or more is supplied to the discharge electrode to generate plasma between the discharge electrode and the substrate to form a power generation layer. Process,
And a step of forming an n layer after the step of forming the power generation layer,
The method of manufacturing a photoelectric conversion device, wherein the power generation layer is a microcrystalline silicon film, and a speed at which the power generation layer is formed is 2 nm / s or more. It is a manufacturing method of the photoelectric conversion device according to claim 1,
A method for manufacturing a photoelectric conversion device, further comprising the step of forming a photoelectric conversion layer made of an amorphous silicon film on the substrate before the step of placing the substrate on which the p layer is formed on the ground electrode. It is a manufacturing method of the photoelectric conversion device according to claim 2 ,
A method for manufacturing a photoelectric conversion device, further comprising the step of forming a photoelectric conversion layer using a microcrystalline silicon germanium film as a power generation layer after the step of forming the n layer. It is a manufacturing method of the photoelectric conversion device according to claim 1,
A method for manufacturing a photoelectric conversion device, further comprising a step of forming a photoelectric conversion layer made of an amorphous silicon film after the step of forming the n layer. It is a manufacturing method of the photoelectric conversion device according to claim 4 ,
A photoelectric conversion device further comprising a step of forming a photoelectric conversion layer using a microcrystalline silicon germanium film as a power generation layer on the substrate before the step of installing the substrate on which the p layer is formed on the ground electrode. Manufacturing method.

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