JP2004289188A - Process for fabricating photoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for fabricating a photoelectric conversion element exhibiting good interface characteristics to both an oxide based transparent conductive film and a photoelectric conversion layer in which a high conductivity is ensured while suppressing the quantity of light absorption by preventing the film quality of a p-layer from deteriorating due to the discomposition effect of hydrogen from a semiconductor layer of impurities while securing good interface characteristics. <P>SOLUTION: In the process for fabricating a photoelectric conversion element, a p-layer constituting the photoelectric conversion element having a pin junction is formed by depositing a first p-layer 7 having a film thickness of 5 nm or less and added with impurities uniformly, and then depositing a second p-layer 8 on the first p-layer 7 by gas decomposition containing no p-type impurity. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a photoelectric conversion element, and more particularly, to a method for manufacturing a photoelectric conversion element having a pin junction.

In a thin-film solar cell having a pin junction, a doped layer on the light incident side has been variously developed historically as one of the important factors for improving the conversion efficiency (η).
In particular, the p layer, which is one of the doped layers on the light incident side, functions as an amorphous silicon-based window layer, but is not a photoelectric conversion layer. Therefore, various studies have been made to satisfy the conflicting performances of providing a high efficiency and good p / i interface characteristics.

For example, a method using a boron-doped a-SiC film as the p layer is described in Japanese Patent Publication No. 3-40515 (Patent Document 1) and Japanese Patent Publication No. 3-63229 (Patent Document 2). In these publications, the p-layer is composed of a B ₂ H ₆ gas together with a mixed gas such as silane or a silane derivative (eg, SiH ₄ ), a hydrocarbon (eg, CH ₄ ), or an inert gas (eg, Ar, He). Is described by glow discharge decomposition to form a film. In addition, a plasma chemical vapor deposition method and the like are generally known.

However, when the B ₂ H ₆ gas is mixed with the source gas at the same time, boron extracts hydrogen terminating the bond such as Si in the amorphous. As a result, a large number of dangling bonds called dangling bonds are formed in the layer. Therefore, when the boron-doped amorphous silicon-based film formed by the above method is used for the p-layer serving as the window layer, the light absorption of the p-layer increases.

Therefore, in order to suppress the increase in the amount of light absorption, carbon is introduced into the film up to several tens of percent. However, the increase in the amount of carbon causes deterioration of the film quality, and therefore, the conductivity is reduced and the entire device is reduced. However, there is a problem that the internal resistance increases.
As described above, if an attempt is made to obtain a desired conductivity that does not cause series resistance in the cell characteristics, the amount of light absorption becomes so large that it cannot be ignored, and there is a problem that a sufficient photocurrent cannot be secured.

  In addition, in plasma enhanced chemical vapor deposition, boron in the plasma also increases the number of dangling bonds on the film surface, so that a large amount of recombination levels are generated at the p / i interface, which has a great adverse effect on the conversion efficiency. Exert. Therefore, for example, when a boron-doped SiC film is used as the p-layer, the bonding with the photoelectric conversion layer is poor, and it becomes a recombination center of generated photocarriers, and a sufficient open voltage (Voc) and a sufficient fill factor (F. F.) cannot be secured.

Therefore, a method is generally used in which an amorphous film or an intrinsic SiC film in which the amount of C in the film is gradually changed is sandwiched as a buffer layer at the p / i interface to reduce the influence on the cell characteristics. .
However, these buffer layers have low conductivity and cause an increase in the internal resistance of the device. F. It is not possible to avoid the suppression of the decrease.

  On the other hand, Japanese Patent Application Laid-Open No. 7-22638 (Patent Document 3) discloses a method of forming a p-type amorphous silicon layer by stacking an amorphous silicon layer after forming an amorphous boron layer. Appl. Phys. 36 (1997) 467 (Non-Patent Document 1) proposes a method of forming an amorphous boron layer and then laminating amorphous carbon to form a p-layer. .

However, it is still difficult to sufficiently reduce the amount of light absorbed by the amorphous boron layer.
In general, an element formation substrate having a concavo-convex structure made of an oxide-based transparent conductive film such as a SnO ₂ or ZnO film on a glass substrate is used. A pin junction is formed on these oxide-based transparent conductive films. In the case of manufacturing, the interface resistance between the amorphous boron layer and the oxide-based transparent conductive film in JP-A-7-22638 or Appl. Phys. 36 (1997) 467 is high, and good device characteristics cannot be obtained. Still difficult.

  As described above, according to the above-described conventional method, the p layer has a small amount of light absorption, high conductivity, and good interface characteristics with both the oxide-based transparent conductive film and the photoelectric conversion layer. A technology that satisfies conflicting characteristics has not been realized.

Japanese Patent Publication No. 3-40515 Japanese Patent Publication No. 3-63229 JP-A-7-22638 Appl. Phys. 36 (1997) 467

  According to the present invention, as a p-layer constituting a photoelectric conversion element having a pin junction, a first p-layer having a thickness of 5 nm or less and doped with impurities is formed, and a p-type layer is formed on the first p-layer. There is provided a method for manufacturing a photoelectric conversion element, wherein the second p-layer is formed by forming a second p-layer by gas decomposition containing no impurities.

According to the method for manufacturing a photoelectric conversion element of the present invention, a p-layer constituting a photoelectric conversion element having a pin junction is formed into a first p-layer having a thickness of 5 nm or less and uniformly doped with impurities. Since the second p-layer is formed on the first p-layer by gas decomposition containing no p-type impurity, the photoelectric conversion element can be easily manufactured without using any special manufacturing apparatus and manufacturing method. It becomes possible.
Further, according to the manufacturing method of the present invention, the p-layer constituting the photoelectric conversion element having the pin junction has the uniform p-type impurity-free first p-layer having a thickness of 5 nm or less and the gas containing no p-type impurity. Since a photoelectric conversion element formed by laminating the second p-layer formed by decomposition can be manufactured, the p-layer has a small light absorption amount and is formed from a semiconductor layer constituting the p-layer due to impurities in the p-layer. A photo-conversion element that secures high conductivity by preventing hydrogen from being extracted and has good interface characteristics with both the oxide-based transparent conductive film and the photoelectric conversion layer disposed below and above the p-layer. Can be realized. Furthermore, a sufficient internal electric field can be formed in the i-layer without significantly changing the semiconductor material of the p-layer which has been conventionally used, a relatively large open-circuit voltage can be realized, and the light absorption amount increases. A relatively large short-circuit current can be obtained by suppression.

  The photoelectric conversion element manufactured by the manufacturing method of the present invention has a pin junction, and is mainly composed of a transparent electrode layer; a uniformly doped first p layer having a thickness of 5 nm or less and a p-type impurity. A p-layer formed by laminating a second p-layer formed by gas decomposition that does not include the p-layer; an i-layer; an n-layer; and a back electrode layer. Preferably, the electrode layer and the pin junction are formed on a substrate.

  In the present invention, the substrate that can be used for the photoelectric conversion element is not particularly limited as long as it is generally used as a substrate, and a substrate made of a metal such as stainless steel, aluminum, copper, or zinc, glass Various types of substrates, such as a substrate, a resin substrate such as polyimide, PET, PEN, PES, and Teflon (registered trademark), a substrate in which a resin is applied to a metal substrate, and a substrate in which a metal layer is formed on a resin substrate. Among them, a transparent substrate is preferable. The substrate may be an insulating film, another conductive film made of metal, semiconductor, or the like, a wiring layer, a buffer layer, or a combination thereof, depending on the usage of the substrate. The thickness of the substrate is not particularly limited, but may be, for example, about 0.1 to 30 mm so as to have appropriate strength and weight. Further, the substrate surface may have irregularities.

In the present invention, examples of the transparent electrode layer used for the photoelectric conversion element include conductive oxides such as ZnO, ITO, and SnO ₂ . These electrode materials can be formed as a single layer or a laminated layer. The thickness of such a back electrode can be appropriately adjusted depending on the material to be used and the like, and for example, about 200 to 2000 nm. In addition, irregularities may be formed on the surface of such a transparent electrode layer. Examples of the unevenness include those having a wavelength of light in a visible light region, a height of about 0.1 to 1.2 μm, and a pitch of 0.1 to 10 μm.

  In the present invention, the p-layer of the photoelectric conversion element has a thickness of 5 nm or less and has a first p-layer uniformly doped with impurities and a second p-layer formed by gas decomposition not containing p-type impurities. With such a configuration, it is possible to suppress deterioration in the quality of the p-layer due to the action of extracting hydrogen as an impurity while securing good interface characteristics with the transparent conductive layer formed thereunder.

  The p layer can be formed of a semiconductor layer, particularly an amorphous semiconductor layer, for example, a-Si: H, a-Ge: H, a-SiGe: H or the like, for both the first p layer and the second p layer. The first p-layer and the second p-layer do not necessarily have to be formed of the same semiconductor layer, but it is particularly preferable that both the first p-layer and the second p-layer are a-Si: H.

In the first p-layer, a thickness of 5 nm or less means a thickness in a range where the optical absorption of the first p-layer can be neglected, and includes a film of one or more atomic layers of a semiconductor. Further, this film preferably has a uniform film thickness over the entire surface, but for example, may be formed in an island shape on the surface of the transparent electrode layer. Further, that the impurity is uniformly added means that a predetermined amount of impurity is added over the entire first p-layer. That is, when the first p-layer is formed of a silicon-based layer, there are 10 ²² / cm ² of Si in one atomic layer of the first p-layer, and 10 ¹⁸ / cm ² or more of impurities in the layer. If present, the carrier density is sufficient. This means that only one carrier is required for every 10,000 Si atoms. Therefore, the film thickness and the thickness are adjusted so that carriers such as boron, for example, acceptors that can maintain such a carrier density are present. The impurity concentration can be adjusted.

Since the first p-layer is configured as described above, a sufficient internal electric field can be formed in an i-layer described later, a relatively large open-circuit voltage can be secured, and an increase in light absorption can be suppressed, so that a relatively large short circuit An electric current can be obtained.
The first p-layer may have its surface plasma-treated as described later. By performing the plasma treatment on the surface in this way, good p / i interface characteristics can be provided.

In the second p layer, an i layer is formed by gas decomposition not containing a p-type impurity when forming this layer with a p layer formed by gas decomposition not containing a p-type impurity. Alternatively, it means a layer that can become p-type by diffusion of impurities from the lower first p-layer and / or mixing of impurities from the film formation atmosphere thereafter. Therefore, the impurity of the second conductivity type in the second p-layer is lower than the impurity concentration of the first p-layer.
The impurity concentration in the second p-layer may be evenly diffused, but is preferably gradually reduced from the first p-layer to the i-layer described later. As described above, when the impurity concentration in the second p-layer is gradually reduced, the light absorption coefficient can be gradually increased toward the i-layer, that is, the effect of the impurity to extract hydrogen from the second p-layer. And the amount of light absorption can be gradually reduced, and the film quality of the second p-layer can be prevented from deteriorating.
Further, the second p-layer may be formed as a single layer, or may be formed as a plurality of layers with different film-forming conditions or the like. In other words, the second p-layer may be composed of a plurality of layers in which the light absorption coefficient increases as the distance from the i-layer increases. With this configuration, it is possible to further enhance the bonding characteristics at the p / i interface. F. And Voc can be prevented from lowering, and the recombination probability of the photocurrent at the p / i interface can be reduced.
The thickness of the second p-layer is not particularly limited, but may be, for example, about 1 to 200 nm. When the second p-layer is formed of a plurality of layers, the thickness of each layer is preferably about 1 to 30 nm.

Further, as described later, the surface of the second p-layer may be plasma-treated, or when the second p-layer is formed of a plurality of layers, the surface of each layer may be plasma-treated. . Note that all surfaces of the plurality of layers may be plasma-treated, or the surfaces of some of the layers may be plasma-treated.
In the present invention, the i-layer and the n-layer in the photoelectric conversion element are not particularly limited as long as they are the i-layer and the n-layer usually used for the pin junction in the photoelectric conversion element. For example, each of the i-layer and the n-layer is formed of the above-mentioned amorphous layer, the i-layer does not contain an impurity serving as a carrier, and the n-layer contains an impurity serving as a donor, for example, phosphorus or arsenic. A layer introduced at about 10 ¹⁸ to 10 ¹⁹ cm ⁻³ is exemplified. These film thicknesses can be appropriately adjusted depending on the energy to be obtained by the photoelectric conversion element, the impurity concentration in the p-layer, the n-layer, and the like, and for example, about 100 to 600 nm and about 30 to 100 nm, respectively. .

The back electrode layer is not particularly limited as long as it is a conductive material usually used as an electrode, and examples thereof include metals such as gold, platinum, silver, copper, and aluminum, and the above-described conductive oxides. . These film thicknesses can be appropriately selected according to the usage mode of the photoelectric conversion element.
In the present invention, the photoelectric conversion element may have only one pin junction on the substrate, or may have a plurality of repetitions. Further, all of the n-layer, i-layer and p-layer constituting the pin junction need not be formed of amorphous silicon, and it is sufficient that at least the n-layer and i-layer are formed of amorphous silicon. Further, a buffer layer, an intermediate layer, a conductive layer, an insulating layer, and the like may be further provided between the transparent electrode layer, the p layer, the i layer, the n layer, and the back electrode layer.

In the method for manufacturing a photoelectric conversion element of the present invention, first, a first p-layer having a thickness of 5 nm or less and uniformly doped with impurities is formed on a substrate having a transparent electrode layer on the surface thereof. .
The first p-layer can be formed by a known method, for example, a CVD method using a source gas such as SiH ₄ , GeH ₄ , CH ₄ , H ₂ , Ar, He, a plasma CVD method, or the like. The p-type impurity (boron or the like) constituting the p-layer may be doped simultaneously with the film formation by mixing, for example, B ₂ H ₆ gas into the source gas, or may be ion-implanted or formed after forming the semiconductor layer. Doping may be performed by a method such as thermal diffusion.

Further, the first p-layer may be subjected to a plasma treatment on its surface as described above. The plasma at this time is, for example, H ₂ , He, Ar, or the like. When the first p-layer is formed of the a-Si layer, the conditions of the plasma processing can be set, for example, as shown in Table 1.

When the first p layer is formed using Ge as a main element, it is appropriate to perform the input power under a low condition, and when formed using C as a main element, it is appropriate to perform the input power under a high condition. is there.
By such a plasma treatment, the light absorption coefficient in the first p-layer can be increased, that is, the increase in the amount of light absorption in the first p-layer can be suppressed, so that a relatively high short-circuit current can be obtained.

Next, a second p-layer is formed on the first p-layer by gas decomposition containing no p-type impurity. The method for forming the second p-layer can be the same as the method for forming the first p-layer except that the source gas does not contain impurities.
By forming a film by such a method, the p-type impurity is not positively contained, but the p-type impurity is diffused from the first p-layer serving as the base, so that the second p-layer can be formed as a result. it can. In the case where the first and second p-layers are formed by a film forming apparatus, for example, a plasma CVD apparatus, the second p-layer is formed in the same chamber as the first p-layer so that the second p-layer exists in the atmosphere. By mixing p-type impurities when forming the 1p layer, the second p layer can be formed as a result.

Further, the surface of the second p-layer and / or the surface of the obtained second p-layer may be subjected to plasma treatment every time a film having a predetermined thickness is formed, thereby reducing the amount of light absorbed by the second p-layer. It is possible and preferable. The predetermined thickness at this time is, for example, about 1 to 30 nm.
In the case where the plasma processing is performed a plurality of times for each predetermined film thickness, the plasma irradiation time and / or the power input during the processing may be gradually reduced to a second time from the first time and a third time from the second time. preferable. By such a plasma treatment, the light absorption coefficient in the second p-layer can be gradually increased as approaching the i-layer, that is, the increase in light absorption in the first p-layer can be suppressed gradually, so that the short-circuit current can be reduced. Voc and F.I. F. Can be suppressed.

  Note that the formation of the second p-layer may be performed in the same chamber as the chamber of the film forming apparatus in which the first p-layer is formed. In this case, the light absorption coefficient can be increased without designing a special doping profile, that is, the increase in the amount of light absorption in the first and second p-layers can be suppressed. , And a significant reduction in manufacturing cost can be realized.

Further, the formation of the second p-layer does not necessarily have to be the same as the chamber of the film forming apparatus in which the first p-layer has been formed, and may be formed in a different chamber. In this case, since excessive diffusion of impurities is not applied to the second p-layer, the internal electric field in the second p-layer can be easily controlled. As a result, it is possible to easily control the internal electric field of the i-layer without causing excessive diffusion of impurities into the i-layer, and to suppress the space charge in the i-layer. An increase (suppression of a decrease in FF) can be realized.
Hereinafter, examples of the method for manufacturing a photoelectric conversion element of the present invention will be described.

[Embodiment 1: Evaluation of light absorption amount of p-layer]
First, a transparent glass substrate is placed on a substrate support in a chamber of a plasma vapor deposition apparatus, and SiH ₄ : B ₂ H ₆ : H ₂ = 1: 0.1: 20 on the transparent glass substrate. The source gas was supplied at a flow rate of 200 sccm. At this time, the film formation temperature was set to 200 ° C., the substrate temperature was set to 200 ° C., the input power was set to 200 W, and the film was formed for 10 minutes to produce a highly doped p-type a-Si layer doped with boron at a high concentration. The thickness of the obtained highly doped p-type a-Si layer was set to a thickness where the amount of light absorption was negligible, in this case, a thickness of about 2 nm.

Subsequently, in the same chamber, an a-Si layer not doped with boron was formed to a thickness of about 10 nm using a source gas of SiH ₄ : H ₂ = 100: 200 sccm. At this time, the a-Si layer becomes p-type due to the diffusion of boron from the highly doped p-type a-Si layer underlying the a-Si layer or the incorporation of boron in the atmosphere gas. By repeating this method, a p-layer having a total thickness of 300 nm was formed by laminating a highly doped p-type a-Si layer of about 2 nm for every about 10 nm of a-Si layer.

For comparison, a single p-layer having a thickness of 300 nm was formed on a transparent glass substrate with a mixed gas of SiH ₄ : B ₂ H ₆ : H ₂ = 100: 5: 200. Was formed.
Using these two types of p layers, the amount of light absorption and the electrical conductivity of each layer were measured. The result is shown in FIG.

As is clear from FIG. 1, the light absorption amount is smaller in a highly doped p layer / p layer repeated p layer than in a normal single p layer. This is presumably because the repeated p-layer of the highly doped p-layer / p-layer does not have the effect of extracting hydrogen from boron when the p-layer is formed.
The conductivity of each layer was about 5 × 10 ⁻⁴ S / cm, which was almost the same value.

  In the above description, the p-layer in the repetitive p-layer of the highly-doped p-layer / p-layer is about 12 nm, and the highly-doped p-layer of 2 nm is laminated every about 10 nm. In this case, it is known that the effect of reducing the amount of light absorption can be obtained at the same conductivity by forming the film at 200 ° C.

[Embodiment 2: photoelectric conversion element and manufacturing method thereof]
As shown in FIG. 2, the photoelectric conversion element of this embodiment has a transparent electrode layer 2, a highly doped p-type a-Si layer 7, a p-type a-Si layer 8, an i-layer 4, an n layer 5 and a back electrode layer 6 are sequentially formed.

The method for manufacturing the photoelectric conversion element will be described below.
First, a transparent electrode layer 2 is formed on a transparent glass substrate 1 by sputtering a ZnO film having a gentle unevenness with a thickness of about 300 nm to a thickness of about 800 nm.
Subsequently, the obtained transparent glass substrate 1 is placed on a substrate support in a p-layer film forming chamber of the film forming apparatus, and SiH ₄ : B ₂ H ₆ : H ₂ = 1 : 0.1: 20 mixed gas was supplied at a flow rate of 200 sccm. At this time, film formation was performed at a film formation temperature of 200 ° C., a substrate temperature of 200 ° C., and an input power of 200 W. As a first p layer, a highly doped p-type a-Si layer 7 doped with boron at a high concentration was formed. It was produced with a thickness of about 2 nm.

Subsequently, an a-Si layer 8 not doped with boron was formed to a thickness of about 10 nm in the same chamber. At this time, the p-type s-Si layer 8 is formed by diffusion of boron from the highly doped p-type a-Si layer 7 underlying the a-Si layer 8 or mixing of boron in the atmosphere gas. Layer (second p layer).
Next, an i-layer 4 having a thickness of about 200 nm is formed on the a-Si layer 8 in an i-layer deposition chamber with SiH ₄ : H ₂ = 200: 500 and an applied power of 100 W. An n-layer 5 having a thickness of about 30 nm was formed on the n-layer deposition chamber with SiH ₄ : H ₂ : PH ₃ = 10: 500: 3 and a power of 100 W.

Thereafter, an Ag film having a thickness of 500 nm was formed at a film forming temperature of 200 ° C. using a sputtering apparatus, and a back electrode was formed.
Thus, a photoelectric conversion element having a pin junction shown in FIG. 2 was manufactured.
The IV characteristics of the obtained photoelectric conversion element were evaluated.
For comparison, as shown in FIG. 4, instead of the highly doped p-type a-Si layer 7 and the p-type a-Si layer 8, SiH ₄ : B ₂ H ₆ : H ₂ = 100: 5: 200 A photoelectric conversion element having the same configuration as the above-described photoelectric conversion element was prepared except that a single p-layer having a thickness of 10 nm was formed using a mixed gas of the above.

A. of these photoelectric conversion elements M. FIG. 3 shows the IV characteristics under 1.5.
As is clear from FIG. 3, in the photoelectric conversion element according to the second embodiment, as described in the first embodiment, the short-circuit current is 15.0 mA / cm ² because the light absorption of the p-layer is small. And a relatively large value was obtained. In addition, Voc = 0.85 V; F. = 0.65, which indicates that the carrier density of the p-layer is also sufficient.

On the other hand, in the photoelectric conversion element in which the p-layer is formed as a single layer, the amount of light absorption in the p-layer is large as described in the first embodiment, and therefore, compared to the photoelectric conversion element in the second embodiment. Therefore, it is understood that the short-circuit current is not enough at 13.2 mA / cm ² .

[Embodiment 3: Evaluation of light absorption amount of p layer]
Using the same substrate as in the first embodiment, a similar method is used to form an approximately 10 nm a-Si layer on an approximately 2 nm highly doped p-type a-Si layer. Plasma treatment was performed using helium gas under the conditions shown in Table 2. These steps were repeated to form a p-layer having a total thickness of 300 nm.

The light absorption of the p layer obtained above was measured. The result is shown in FIG.
As is clear from FIG. 5, the light absorption amount is smaller than that of the highly doped p-layer / p-layer repetition p-layer according to the first embodiment by performing the plasma treatment. .
Further, in the above, the p-layer in the repetitive p-layer of the highly doped p-layer / p-layer is set to about 10 nm, and the highly doped p-layer is laminated every about 10 nm, and the plasma treatment is performed. It has been found that the same effect of reducing the amount of light absorption can be obtained in the following cases.

[Embodiment 4: Photoelectric conversion element and manufacturing method thereof]
As shown in FIG. 6, a photoelectric conversion element according to this embodiment includes a transparent glass substrate 1, a transparent electrode layer 2, a highly doped p-type a-Si layer 7, a p-type a-Si layer 8, and an i-layer. 4, an n-layer 5 and a back electrode layer 6 are sequentially formed, and the surface of the p-type a-Si layer 8 has a surface 9 that has been subjected to plasma processing.

The method for manufacturing the photoelectric conversion element will be described below.
First, similarly to the second embodiment, a highly doped p-type a-Si layer and an a-Si layer 8 are formed on a transparent glass substrate 1 provided with a ZnO film having the same concavo-convex shape as the second embodiment. Form.
Next, the surface of the a-Si layer 8 was subjected to plasma treatment using hydrogen gas under the conditions shown in Table 3.

Subsequently, as in Embodiment 2, the i-layer 4, the n-layer 5, and the back electrode 6 were formed on the a-Si layer 8, and the photoelectric conversion element shown in FIG. 6 was manufactured.
The IV characteristics of the obtained photoelectric conversion element were evaluated.
A. of this photoelectric conversion element M. FIG. 7 shows IV characteristics under 1.5. Note that FIG. 7 also shows, for comparison, the IV characteristics of the photoelectric conversion element obtained in Embodiment 2.

As is clear from FIG. 7, in the photoelectric conversion element according to the fourth embodiment, as described in the third embodiment, the short-circuit current is 16.0 mA / cm because the light absorption amount of the p-layer is smaller. ^A higher value of ² was obtained. Further, Voc = 0.9 V, F.C. F. = 0.68, which indicates that the carrier density of the p-layer is also sufficient.

[Embodiment 5: Photoelectric conversion element and manufacturing method thereof]
In the photoelectric conversion element of this embodiment, a transparent electrode layer, a highly doped p-type a-Si layer, a p-type a-Si layer, an i-layer, an n-layer, and a back electrode layer are sequentially formed on a transparent glass substrate, The highly doped p-type a-Si layer has a surface subjected to plasma treatment on the surface.

The method for manufacturing the photoelectric conversion element will be described below.
First, similarly to the second embodiment, a highly doped p-type a-Si layer is formed on a transparent glass substrate 1 having a ZnO film having a concavo-convex shape on the surface as in the second embodiment, and then a hydrogen gas is formed. And plasma treatment was performed under the conditions shown in Table 3.
Next, on the highly doped p-type a-Si layer, an a-Si layer, an i-layer, an n-layer, and a back electrode were formed in the same manner as in Embodiment 2, to produce a photoelectric conversion element.

When the IV characteristics of the obtained photoelectric conversion element were evaluated, the photoelectric conversion element according to Embodiment 5 exhibited a large short-circuit current of 16.5 mA / cm ² . Further, Voc = 0.9 V, F.C. F. = 0.68, which indicates that the carrier density of the p-layer is also sufficient.

[Embodiment 6: Photoelectric conversion element and manufacturing method thereof]
As shown in FIG. 8, a photoelectric conversion element according to this embodiment has a transparent electrode layer 2, a highly doped p-type a-Si layer 7, a p-type graded plasma processing layer 10, i on a transparent glass substrate 1. The layer 4, the n-layer 5, and the back electrode layer 6 are sequentially formed, and the surface of the highly doped p-type a-Si layer 7 has a plasma-treated surface. It has a surface that has been subjected to plasma processing.

The method for manufacturing the photoelectric conversion element will be described below.
First, similarly to the second embodiment, a highly doped p-type a-Si layer 7 is formed on a transparent glass substrate 1 having a ZnO film having a concavo-convex shape similar to that of the second embodiment on the surface. As in Embodiment 5, the surface of the highly doped p-type a-Si layer 7 was subjected to plasma treatment using hydrogen gas.

Next, an i-layer having a thickness of 3 nm was formed in the same highly doped p-type a-Si layer 7 in the film formation chamber, and the H ₂ plasma treatment shown in Table 2 was performed at 50 W for 1 minute. Was formed, and the H ₂ plasma treatment shown in Table 3 was performed at 20 W for 1 minute. As a result, boron was mixed in from the atmosphere, and these two i-layers were formed as the p-type graded plasma processing layer 10.

Subsequently, an i-layer 4 having a thickness of 200 nm was formed in the i-layer film forming chamber.
Thereafter, an n-layer 5 having a thickness of 30 nm was formed in an n-layer formation chamber, and then a back electrode 6 was formed, thereby producing the photoelectric conversion element shown in FIG.
The IV characteristics of the obtained photoelectric conversion element were evaluated.
A. of this photoelectric conversion element M. FIG. 9 shows the IV characteristics under 1.5. FIG. 9 also shows, for comparison, the IV characteristics of the photoelectric conversion element obtained by plasma-treating the surface of the a-Si layer 8 obtained in Embodiment 3 with hydrogen.

As is clear from FIG. 9, in the photoelectric conversion element according to the sixth embodiment, as described in the fifth embodiment, a short-circuit current as large as 16.5 mA / cm ² is obtained, and Voc = 0. .92 V, F.R. F. = 0.73, indicating that the carrier density of the p-layer was improved.

4 is a graph showing an evaluation of a light absorption amount of a p-layer used in the photoelectric conversion element of the present invention. FIG. 2 is a schematic sectional view of a main part showing an example of the photoelectric conversion element of the present invention. 3 is a graph showing IV characteristics of the photoelectric conversion element in FIG. It is a schematic sectional drawing of the important section of the photoelectric conversion element provided with the conventional p layer structure for comparing the IV characteristic of the photoelectric conversion element of this invention. It is a graph which shows evaluation of the amount of light absorption of the p layer used for another photoelectric conversion element of the present invention. It is a schematic sectional drawing of the important section showing the example of another photoelectric conversion element of the present invention. 7 is a graph showing IV characteristics of the photoelectric conversion element in FIG. It is an outline sectional view of an important section showing an example of still another photoelectric conversion element of the present invention. 9 is a graph showing IV characteristics of the photoelectric conversion element in FIG.

Explanation of reference numerals

Reference Signs List 1 glass substrate 2 transparent electrode layer 3 p-type a-Si
4 i layer 5 n layer 6 back electrode layer 7 highly doped p-type a-Si layer (first p layer)
8 p-type a-Si layer (second p layer)
9 Plasma treatment interface 10 P-type graded plasma treatment layer

Claims (6)

  As a p-layer constituting a photoelectric conversion element having a pin junction, a first p-layer having a thickness of 5 nm or less and uniformly doped with impurities is formed, and gas decomposition free of p-type impurities is formed on the first p-layer. A method for manufacturing a photoelectric conversion element, wherein the second p-layer is formed by forming a second p-layer.   The method according to claim 1, wherein after forming the first p-layer, the surface of the first p-layer is subjected to plasma treatment.   3. The method according to claim 1, wherein during the formation of the second p-layer, a plasma treatment is performed on the surface of the second p-layer obtained every time the second p-layer is formed to a predetermined thickness.   4. The method for manufacturing a photoelectric conversion element according to claim 3, wherein the plasma processing is performed with a reduced plasma irradiation time and / or processing power every time a predetermined film thickness is formed.   The method according to any one of claims 1 to 4, wherein the first p-layer and the second p-layer are formed in the same chamber of a film forming apparatus.   The method for manufacturing a photoelectric conversion element according to any one of claims 1 to 4, wherein the first p layer, the second p layer, and the i layer are formed in different chambers of a film forming apparatus.

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