JP6021084B2 - Photovoltaic device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a photovoltaic device and a manufacturing method thereof.

  A photovoltaic device is known in which a substantially intrinsic amorphous silicon layer is formed between a crystalline silicon substrate and a doped amorphous silicon layer.

  As a means for improving the output characteristics of a photovoltaic device having such a structure, a structure in which the oxygen concentration at the interface between the silicon substrate and the intrinsic amorphous silicon layer is increased is disclosed (see Patent Document 1). . In addition, a structure is disclosed in which a gradient is provided in the oxygen concentration in the intrinsic amorphous silicon layer to increase the oxygen concentration on the doped amorphous silicon layer side (see Patent Document 2).

  On the other hand, in the technology for deactivating the surface of a silicon substrate with an intrinsic amorphous silicon layer, an appropriate amount of oxygen is contained in the entire intrinsic amorphous silicon layer to form a minute amorphous silicon oxide region in the layer. By doing so, it is reported that inactivation is promoted (refer nonpatent literature 1). Furthermore, it has been reported that when an appropriate amount of oxygen is contained in the entire intrinsic amorphous silicon layer, the output characteristics of the photovoltaic device are improved (see Non-Patent Document 2).

Japanese Patent No. 4070483 JP 2008-235400 A

J.Appl.Phys. 107,014504 (2010) Appl.Phys.Lett. 91,133508 (2007)

  By the way, if excessive oxygen is taken into the amorphous silicon layer, it may act as an impurity to form defects or form a high resistance region, and it is desirable to optimize the oxygen concentration contained. It is. However, the optimum oxygen concentration profile in the intrinsic amorphous silicon layer, particularly the oxygen concentration on the interface side between the silicon substrate and the intrinsic amorphous silicon layer has not been sufficiently studied.

One aspect of the present invention includes a crystalline semiconductor substrate having a first surface and a second surface, and a first amorphous semiconductor layer formed on the first surface of the crystalline semiconductor substrate. In the photoelectric conversion device, an interface between the crystalline semiconductor substrate and the first amorphous semiconductor layer is an oxidation interface containing oxygen of 1 × 10 ²¹ / cm ³ or more, and In the crystalline semiconductor layer, the photoelectric conversion device includes a high concentration oxygen region having an oxygen concentration of 1 × 10 ²⁰ / cm ³ or more and 1 × 10 ²¹ / cm ³ or less in a range of 5 nm or less from the oxidation interface.

  Here, it is preferable that the high-concentration oxygen region is in a region of 1 nm or less from the oxidation interface.

  The conductivity type of the semiconductor substrate is n-type, the first amorphous semiconductor layer is an n-type amorphous semiconductor layer, and the n-type amorphous semiconductor layer is on the light incident surface side. It is preferable to be located in

  The conductivity type of the semiconductor substrate is n-type, the first amorphous semiconductor layer is a p-type amorphous semiconductor layer, and the p-type amorphous semiconductor layer is on the light incident surface side. It is preferable to be located in

  In addition, it is preferable that a collecting electrode is formed on the first amorphous semiconductor layer.

  Further, it is preferable that the first amorphous semiconductor layer has an oxygen concentration profile in which the concentration decreases stepwise along the film thickness direction from the vicinity of the oxidation interface.

  Another aspect of the present invention includes a first step of forming a concavo-convex structure on the surface of a semiconductor substrate made of crystalline silicon, a second step of oxidizing the surface of the semiconductor substrate to form an oxidized interface, And a third step of forming an amorphous semiconductor layer on the oxidation interface, wherein the oxidation treatment includes a method of leaving the substrate in an air atmosphere for a predetermined time, an ozone water treatment, This is a method for manufacturing a photoelectric conversion device, which is carried out using any method selected from hydrogen peroxide treatment, ozonizer treatment, and the like.

  Here, the amorphous semiconductor layer is preferably formed by introducing a silicon-containing gas and carbon dioxide gas or oxygen gas.

  Preferably, the method further includes a fourth step of forming an n-type or p-type amorphous semiconductor layer by introducing an n-type or p-type dopant into the silicon-containing gas after the third step. is there.

  According to the present invention, the photoelectric conversion efficiency in the photovoltaic device can be increased.

It is sectional drawing of the photovoltaic apparatus in embodiment which concerns on this invention. It is a figure which shows the oxygen concentration profile of the photovoltaic apparatus in embodiment which concerns on this invention. It is a figure which shows the gradient profile of the logarithm display of the oxygen concentration of the photovoltaic apparatus in embodiment which concerns on this invention.

  As shown in the sectional view of FIG. 1, the photovoltaic device 100 according to the embodiment of the present invention includes a semiconductor substrate 10, an i-type amorphous layer 12i, a p-type amorphous layer 12p, a transparent conductive layer 14, i. A type amorphous layer 16i, an n type amorphous layer 16n, a transparent conductive layer 18, and collector electrodes 20 and 22 are included.

Hereinafter, the structure of the photovoltaic device 100 will be described while showing a method for manufacturing the photovoltaic device 100. Table 1 shows examples of conditions for forming each amorphous layer in the photovoltaic device 100. Note that the various film forming conditions used in the present embodiment are examples, and should be appropriately changed and optimized depending on the apparatus to be used.

  The semiconductor substrate 10 is made of a crystalline semiconductor material. The semiconductor substrate 10 can be an n-type or p-type conductive crystalline semiconductor substrate. As the semiconductor substrate 10, for example, a single crystal silicon substrate, a polycrystalline silicon substrate, a gallium arsenide substrate (GaAs), an indium phosphide substrate (InP), or the like can be applied. The semiconductor substrate 10 absorbs incident light to generate electron and hole carrier pairs by photoelectric conversion. Hereinafter, an example in which an n-type silicon single crystal substrate is used as the semiconductor substrate 10 will be described.

  The semiconductor substrate 10 is placed in a film formation tank after cleaning. The semiconductor substrate 10 can be cleaned using a hydrofluoric acid aqueous solution (HF aqueous solution) or an RCA cleaning solution. It is also preferable to form a texture structure on the front surface or the back surface of the semiconductor substrate 10 using an alkaline etching solution such as a potassium hydroxide aqueous solution (KOH aqueous solution). In this case, a texture structure having a pyramidal (111) plane can be formed by anisotropically etching the semiconductor substrate 10 having a (100) plane with a KOH aqueous solution.

  Further, a predetermined oxidation treatment may be performed before forming the i-type amorphous layer 12i to form an oxidation interface. As the predetermined oxidation treatment, it can be left for a predetermined time in an atmosphere controlled in the air or humidity, or an ozone water treatment, a hydrogen peroxide treatment, an ozonizer treatment, or the like can be used as appropriate.

An i-type amorphous layer 12 i that is an amorphous semiconductor layer is formed on the surface of the semiconductor substrate 10. For example, the i-type amorphous layer 12i is an amorphous intrinsic silicon semiconductor layer containing hydrogen. Here, the intrinsic semiconductor layer is a case where the concentration of the p-type or n-type dopant contained is 5 × 10 ¹⁸ / cm ³ or less, or when the p-type and n-type dopants are included at the same time. It refers to a semiconductor layer having a p-type or n-type dopant concentration difference of 5 × 10 ¹⁸ / cm ³ or less. It is preferable that the i-type amorphous layer 12i be thin enough to suppress light absorption as much as possible, and thick enough to sufficiently passivate the surface of the semiconductor substrate 10. The film thickness of the i-type amorphous layer 12i is 1 nm to 25 nm, preferably 5 nm to 10 nm.

The i-type amorphous layer 12i can be formed by plasma enhanced chemical vapor deposition (PECVD), Cat-CVD (Catalytic Chemical Vapor Deposition), sputtering, or the like. For PECVD, any method such as RF plasma CVD, high frequency VHF plasma CVD, or microwave plasma CVD may be used. In this embodiment, a case where an RF plasma CVD method is used will be described. For example, as shown in Table 1, a silicon-containing gas such as silane (SiH ₄ ) is supplied by diluting with hydrogen, RF high-frequency power is applied to parallel plate electrodes and the like to form plasma, and the heated semiconductor substrate 10 It can form by supplying to the film-forming surface. At this time, in the present embodiment, a gas containing oxygen (O ₂ ) is simultaneously introduced at the initial stage of the formation of the i-type amorphous layer 12i, so that the vicinity of the interface between the semiconductor substrate 10 and the i-type amorphous layer 12i. Introduce oxygen. Examples of the gas containing oxygen (O ₂ ) include carbon dioxide (CO ₂ ) gas and oxygen (O ₂ ). The substrate temperature during film formation is 150 ° C. or more and 250 ° C. or less, and the RF power density is 1 mW / cm ² or more and 10 mW / cm ² or less.

Here, as shown in FIG. 2, an oxygen concentration profile in which the concentration decreases stepwise from the vicinity of the interface between the semiconductor substrate 10 and the i-type amorphous layer 12i in the film thickness direction of the i-type amorphous layer 12i. And For example, when the i-type amorphous layer 12i is formed, a high-concentration oxygen region containing a large amount of oxygen is formed only on the interface side with the semiconductor substrate 10 by changing the flow rate of the oxygen-containing gas stepwise. To do. The oxygen concentration in the high concentration oxygen region is about 1 × 10 ²⁰ / cm ^{3 to} 1 × 10 ²¹ / cm ³ and the oxygen concentration in the region other than the high concentration oxygen region of the i-type amorphous layer 12 i is about 1 × 10 10. It is preferable to be less than ²⁰ / cm ³ . In addition, in the high concentration oxygen region, it is preferable that the oxygen concentration has a step-like profile having at least one step along the film thickness direction. The oxygen concentration profile from the semiconductor substrate 10 and the characteristics of the photovoltaic device will be described later.

  Note that the concentration of each element in the semiconductor film can be measured by secondary ion mass spectrometry (SIMS) or the like. When the semiconductor substrate 10 is provided with a texture structure, the concentration of each element in the film may be measured by a method that does not reduce the resolution in the film thickness direction due to the texture.

The p-type amorphous layer 12p is a layer made of an amorphous semiconductor film containing a p-type conductive dopant. For example, the p-type amorphous layer 12p is formed from amorphous silicon containing hydrogen. The p-type amorphous layer 12p has a higher p-type dopant concentration in the film than the i-type amorphous layer 12i. For example, the p-type amorphous layer 12p preferably has a p-type dopant concentration of 1 × 10 ²⁰ / cm ³ or more. The thickness of the p-type amorphous layer 12p is preferably thin so as to suppress light absorption as much as possible, while carriers generated in the semiconductor substrate 10 are effectively separated at the pn junction, In addition, it is preferable to increase the thickness so that the generated carriers are efficiently collected by the transparent conductive layer 14. For example, the thickness is preferably 1 nm or more and 10 nm or less.

The p-type amorphous layer 12p can also be formed by PECVD, Cat-CVD, sputtering, or the like. For PECVD, an RF plasma CVD method can be applied. For example, as shown in Table 1, a silicon-containing gas such as silane (SiH ₄ ) and a p-type dopant-containing gas such as diborane (B ₂ H ₆ ) are diluted with hydrogen and supplied to an RF radio frequency to parallel plate electrodes or the like. It can be formed by applying power to plasma and supplying it to the heated i-type amorphous layer 12 i of the semiconductor substrate 10. In Table 1, diborane (B ₂ H ₆ ) was diluted with 1% hydrogen. The substrate temperature during film formation is preferably 150 ° C. or more and 250 ° C. or less, and the RF power density is preferably 1 mW / cm ² or more and 10 mW / cm ² or less.

  The i-type amorphous layer 16 i is formed on the back surface of the semiconductor substrate 10. That is, after the i-type amorphous layer 12 i and the p-type amorphous layer 12 p are formed, the front and back of the semiconductor substrate 10 are reversed and formed on the back surface of the semiconductor substrate 10. For example, the i-type amorphous layer 16i is an amorphous intrinsic silicon semiconductor layer containing hydrogen. The film thickness of the i-type amorphous layer 16i is 1 nm or more and 25 nm or less, preferably 5 nm or more and 10 nm or less, similarly to the i-type amorphous layer 12i.

The i-type amorphous layer 16i can be formed by PECVD, Cat-CVD, sputtering, or the like. For PECVD, an RF plasma CVD method can be applied. For example, as shown in Table 1, a silicon-containing gas such as silane (SiH ₄ ) is supplied by diluting with hydrogen, RF high-frequency power is applied to parallel plate electrodes and the like to form plasma, and the heated semiconductor substrate 10 It can form by supplying to the film-forming surface. Substrate temperature during film formation, as well as the i-type amorphous layer 12i, 0.99 ° C. or higher 250 ° C. or less, RF power density is 1 mW / cm ² or more 10 mW / cm ² or less.

Also in the i-type amorphous layer 16i, similarly to the i-type amorphous layer 12i, a gas containing oxygen (O ₂ ) is simultaneously introduced at the initial stage of film formation, so that the semiconductor substrate 10 and the i-type amorphous layer 16i. It is preferable to introduce oxygen in the vicinity of the interface.

The n-type amorphous layer 16n is a layer made of an amorphous semiconductor film containing an n-type conductive dopant. For example, the n-type amorphous layer 16n is formed from amorphous silicon containing hydrogen. The n-type amorphous layer 16n has a higher n-type dopant concentration in the film than the i-type amorphous layer 16i. For example, the n-type amorphous layer 16n preferably has an n-type dopant concentration of 1 × 10 ²⁰ / cm ³ or more. The thickness of the n-type amorphous layer 16n is preferably thin so that light absorption can be suppressed as much as possible, while carriers generated in the semiconductor substrate 10 are more effective due to the BSF (Back Surface Field) structure. It is preferable that the generated carriers be thick enough to be efficiently collected by the transparent conductive layer 18 while being separated. For example, the thickness is preferably 1 nm or more and 10 nm or less.

The n-type amorphous layer 16n can also be formed by PECVD, Cat-CVD, sputtering, or the like. For PECVD, an RF plasma CVD method can be applied. For example, as shown in Table 1, a silicon-containing gas such as silane (SiH ₄ ) and an n-type dopant-containing gas such as phosphine (PH ₃ ) are diluted with hydrogen and supplied, and RF high frequency power is supplied to parallel plate electrodes and the like. It can be formed by applying it into plasma and supplying it to the heated i-type amorphous layer 16 i of the semiconductor substrate 10. In Table 1, phosphine (PH ₃ ) was diluted with 2% hydrogen. The substrate temperature during film formation is preferably 150 ° C. or more and 250 ° C. or less, and the RF power density is preferably 1 mW / cm ² or more and 10 mW / cm ² or less.

  Note that it is arbitrary whether the front surface side of the semiconductor substrate 10 is a light receiving surface (a surface on which light is mainly introduced from the outside) or the back surface side is a light receiving surface. In the above-described embodiment, after forming the front-side i-type amorphous layer 12i and the p-type amorphous layer 12p, the semiconductor substrate 10 is inverted, and the back-side i-type amorphous layer 16i and the n-type Although the amorphous layer 16n is formed, the formation order thereof is also arbitrary.

The transparent conductive layers 14 and 18 are formed on the p-type amorphous layer 12p and the n-type amorphous layer 16n, respectively. The transparent conductive layers 14 and 18 are made of, for example, a metal oxide such as indium oxide (In ₂ O ₃ ), zinc oxide (ZnO), tin oxide (SnO ₂ ), or titanium oxide (TiO ₂ ) having a polycrystalline structure. Consists of at least one of these metal oxides, tin (Sn), zinc (Zn), tungsten (W), antimony (Sb), titanium (Ti), cerium (Ce), gallium (Ga) Or the like. The transparent conductive layers 14 and 18 can be formed by a thin film forming method such as vapor deposition, plasma enhanced chemical vapor deposition (PECVD), or sputtering. Although the film thickness of the transparent conductive layers 14 and 18 can be suitably adjusted with the refractive index of the transparent conductive layers 14 and 18, in this embodiment, they were 70 nm or more and 100 nm or less.

  Collector electrodes 20 and 22 are formed on transparent conductive layers 14 and 18, respectively. The collector electrodes 20 and 22 preferably have a comb-like finger electrode structure. The collector electrodes 20 and 22 can be formed by a screen printing method, a plating method, or the like. The collector electrodes 20 and 22 are formed, for example, by applying a silver paste or the like to a thickness of about several tens of μm.

<Examples and Comparative Examples 1 to 3>
In accordance with the above formation method, i having an oxygen concentration profile in which the concentration decreases stepwise from the vicinity of the interface between the semiconductor substrate 10 and the i-type amorphous layer 12i in the film thickness direction under the conditions shown in Table 1. And an i-type amorphous layer 16i having an oxygen concentration profile in which the concentration decreases stepwise from the vicinity of the interface between the semiconductor substrate 10 and the i-type amorphous layer 16i in the film thickness direction. A photovoltaic device having the above was taken as an example.

  A photovoltaic device formed in the same manner as in the example except that no oxygen-containing gas such as carbon dioxide was introduced was used as Comparative Example 1. Further, carbon dioxide gas is introduced for the entire time when the i-type amorphous layer 12i and the i-type amorphous layer 16i are formed, and oxygen is introduced throughout the i-type amorphous layer 12i and the i-type amorphous layer 16i. The contained photovoltaic device was referred to as Comparative Example 2. Further, carbon dioxide gas is introduced for the entire time when the i-type amorphous layer 12i and the p-type amorphous layer 12p, and the i-type amorphous layer 16i and the n-type amorphous layer 16n are formed, so that the i-type amorphous layer is formed. A photovoltaic device in which oxygen was contained in the entire region of the porous layer 12i and the p-type amorphous layer 12p, and the i-type amorphous layer 16i and the n-type amorphous layer 16n was referred to as Comparative Example 3.

  FIG. 2 shows the concentration profiles of oxygen atoms in the semiconductor substrate 10, i-type amorphous layer 12i, and p-type amorphous layer 12p in the examples and comparative examples 1, 2, and 3. The concentration profiles of oxygen atoms in the semiconductor substrate 10, the i-type amorphous layer 16i, and the n-type amorphous layer 16n were also the same. In FIG. 2, the measurement results for the examples are indicated by solid lines, and the measurement results for Comparative Examples 1, 2, and 3 are indicated by alternate long and short dash lines, broken lines, and dotted lines.

Even when no oxygen-containing gas such as carbon dioxide gas is introduced into the i-type amorphous layer 12i and the p-type amorphous layer 12p as in the photovoltaic device of Comparative Example 1, the semiconductor substrate 10 and the i-type amorphous layer Oxygen atoms of the order of 10 ²¹ / cm ³ were present in the interface region with 12i. This is because the surface of the semiconductor substrate 10 is naturally oxidized in the transport period from the cleaning to the formation process of the i-type amorphous layer 12i and in the film forming apparatus. In addition, when a predetermined oxidation process is performed before the above-described film formation, this process is also caused. Therefore, the oxygen concentration of the i-type amorphous layer 12i and the p-type amorphous layer 12p shows a peak at the interface with the semiconductor substrate 10, and once decreases to the background level in the i-type amorphous layer 12i. A profile of rising again toward the p-type amorphous layer 12p and the surface was shown. The increase in the oxygen concentration in the p-type amorphous layer 12p is considered to be due to the influence of introducing a doping gas and the influence of the surface in the measurement.

Further, when an oxygen-containing gas is introduced throughout the i-type amorphous layer 12i as in the photovoltaic device of Comparative Example 2, oxygen of about 1 × 10 ²⁰ / cm ³ or more is added to the i-type amorphous layer 12i. Existed. Similarly, in the photovoltaic device of Comparative Example 3, oxygen of about 1 × 10 ²⁰ / cm ³ or more was present in the i-type amorphous layer 12i. The oxygen concentration tended to be slightly higher in Comparative Example 3 than in Comparative Example 2.

On the other hand, in the photovoltaic device of the example, the peak of the oxygen concentration was present in the interface region with the semiconductor substrate 10 for the same reason as in Comparative Example 1. However, by forming the i-type amorphous layer 12i while controlling the introduction of the oxygen-containing gas step by step, a region containing a large amount of oxygen (high concentration oxygen region) near the interface with the semiconductor substrate 10 is a semiconductor. It was observed within a range of 5 nm from the interface with the substrate 10. The oxygen concentration in the high concentration oxygen region was about 1 × 10 ²⁰ / cm ³ or more and 1 × 10 ²¹ / cm ³ or less. Further, the oxygen concentration in the region other than the high concentration oxygen region of the i-type amorphous layer 12i was less than about 1 × 10 ²⁰ / cm ³ .

Furthermore, in the high concentration oxygen region, the oxygen concentration has a stepped profile with one or more steps along the film thickness direction. In other words, the oxygen concentration profile in the vicinity of the interface of the semiconductor substrate 10 in the i-type amorphous layer 12i has one or more inflection points, and has regions with different slopes. More specifically, the semiconductor substrate 10 is located at the interface A between the semiconductor substrate 10 and the i-type amorphous layer 12i and has an oxygen concentration on the order of 10 ²¹ / cm ³ , within the i-type amorphous layer 12i. 10 and the point B having an oxygen concentration of about 1 × 10 ²⁰ / cm ³ or more and 1 × 10 ²¹ / cm ³ or less from the interface between the i-type amorphous layer 12 i and about 1 nm in the i-type amorphous layer 12 i A point C having an oxygen concentration of about 1 × 10 ²⁰ / cm ^{3 to} 1 × 10 ²¹ / cm ³ from the interface between the semiconductor substrate 10 and the i-type amorphous layer 12 i to about 1 nm to 5 nm, And a point D having an oxygen concentration of about 1 × 10 ²⁰ / cm ³ or less within the i-type amorphous layer 12 i and about 5 nm away from the interface between the semiconductor substrate 10 and the i-type amorphous layer 12 i is an inflection. Confirmed as a point. Note that such an oxygen concentration profile was remarkably confirmed when the concentration axis was logarithmically displayed.

An oxygen concentration of about 1 × 10 ²⁰ / cm ³ has technical critical significance as follows. That is, since the density of silicon atoms in the i-type amorphous layer 12i is about 5 × 10 ²² / cm ³ , when the oxygen concentration is about 1 × 10 ²⁰ / cm ³ , The concentration ratio becomes 0.002. In the vicinity of this value, when the oxygen concentration is lower than 0.002, oxygen atoms behave as impurities in silicon, and when higher than 0.002, oxygen and silicon are alloyed to form oxygen and silicon. It is considered that it has properties as a compound. Therefore, it is considered that the properties of the i-type amorphous layer 12i change at an oxygen concentration of about 1 × 10 ²⁰ / cm ³ as a boundary. Since oxygen atoms have a very low carrier activity in the semiconductor layer of this embodiment, the amorphous layer 12i containing oxygen at the concentration of this embodiment is substantially intrinsic.

  FIG. 3 shows a logarithmic gradient profile of the oxygen concentration obtained by differentiating the oxygen concentration profile shown in FIG. 2 with respect to the film thickness direction. In FIG. 3, an Example is shown with a continuous line and Comparative Examples 1, 2, and 3 are shown with a dashed-dotted line, a broken line, and a dotted line, respectively.

  In Comparative Examples 1 to 3, the oxygen concentration profile changes gently in most of the i-type amorphous layer 12i, and has a sharp peak at the interface between the semiconductor substrate 10 and the i-type amorphous layer 12i. Therefore, the oxygen concentration gradient has a value near 0 in the i-type amorphous layer 12i and the p-type amorphous layer 12p except for the vicinity of the interface between the semiconductor substrate 10 and the i-type amorphous layer 12i. . Further, as it approaches the semiconductor substrate 10 from the surface side, the gradient suddenly increases from a point several nm away from the interface between the semiconductor substrate 10 and the i-type amorphous layer 12i, and the gradient becomes 0 near the interface. It became a negative value.

  On the other hand, in the photovoltaic device of the example, as it approaches the semiconductor substrate 10 from the surface side, the gradient increases from a shallow position in the i-type amorphous layer 12i to show a peak, and the gradient is not again. After approaching 0, the gradient increased from a point several nm away from the interface between the semiconductor substrate 10 and the i-type amorphous layer 12i. Thus, the oxygen concentration gradient profile has at least two peaks in the i-type amorphous layer 12i.

  Note that the above description holds true for the oxygen atom concentration profiles in the semiconductor substrate 10, the i-type amorphous layer 16i, and the n-type amorphous layer 16n.

Table 2 shows the output characteristics of the photovoltaic devices of Examples and Comparative Examples 1 to 3. The measurement data are the open circuit voltage (Voc), the short circuit current (Isc), the fill factor (FF), and the output voltage (Pmax). Table 2 shows values normalized by setting each value of Comparative Example 1 to 1.

  Compared to Comparative Example 1 in which intentional oxygen atoms are not intentionally introduced into the i-type amorphous layers 12i and 16i, improvement in open circuit voltage can be confirmed in Examples and Comparative Examples 2 and 3. Specifically, the open circuit voltage was improved by about 1%. This is because the oxygen concentration in the vicinity of the interface with the semiconductor substrate 10 in the i-type amorphous layers 12i and 16i is higher in the example than in the comparative example 1 and in the comparative examples 2 and 3, and thus the semiconductor substrate 10 and the i-type amorphous material. This is presumably because defects at the interface with the material layers 12i and 16i are effectively inactivated (terminated), and recombination of carriers having the defect as a recombination center is suppressed.

  Moreover, the short circuit current Isc was larger than that of Comparative Example 1 in Examples and Comparative Examples 2 and 3. Specifically, an improvement of 0.5% to 1% was observed. This is because the oxygen concentration in the vicinity of the interface with the semiconductor substrate 10 in the i-type amorphous layers 12i and 16i is higher in the example than in the comparative example 1 and in the comparative examples 2 and 3, and thus the i-type amorphous layer in this region. This is probably because the optical band gaps of the layers 12i and 16i are widened and the light transmittance is increased. Thereby, it is considered that the amount of light transmitted to the semiconductor substrate 10 as the carrier generation layer is increased, and the short circuit current Isc is increased.

  As for the fill factor FF, no significant difference was observed between Comparative Example 1 and the Examples. However, Comparative Example 2 in which oxygen is intentionally introduced over the entire area of the i-type amorphous layers 12i and 16i, and further oxygen is intentionally applied to the entire areas of the p-type amorphous layer 12p and the n-type amorphous layer 16n. In Comparative Example 3 in which the introduction of was carried out, a decrease in the fill factor FF was observed with respect to Comparative Example 1 and Examples. If excessive oxygen atoms are contained in the i-type amorphous layers 12i and 16i, the p-type amorphous layer 12p, and the n-type amorphous layer 16n, defects may be formed as impurities or electrical It is thought that it acts as a resistance layer. On the other hand, even if oxygen is included in the range from the interface between the semiconductor substrate 10 and the i-type amorphous layers 12i and 16i to 5 nm as in the embodiment, the increase in resistance is not large, and the fill factor FF It can be said that it does not worsen. Further, the fill factor FF has a correlation with the open circuit voltage Voc, and it is considered that the effect of the open circuit voltage Voc is larger than the increase in the high resistance layer.

  As a result of these, the output power Pmax showed the maximum in the example. That is, the power generation efficiency is improved by reducing the defect near the interface with the semiconductor substrate 10 and improving the open-circuit voltage Voc and the short-circuit current Isc by effectively taking light into the semiconductor substrate 10 while suppressing the decrease in the fill factor FF. Is considered to have improved.

<Examples and Comparative Examples 4 and 5>
In the example, the oxygen concentration at the points B and C in FIG. 2 was set to 1 × 10 ²⁰ / cm ³ or more and 1 × 10 ²¹ / cm ³ or less. In contrast, a photovoltaic device in which the oxygen concentrations at points B and C in FIG. 2 are greater than 1 × 10 ²¹ / cm ³ is referred to as Comparative Example 4, and the oxygen concentrations at points B and C are 1 × 10 ^20. A photovoltaic device having a size smaller than / cm ³ was defined as Comparative Example 5.

Table 3 shows the output characteristics of the photovoltaic devices of Examples and Comparative Examples 4 and 5. Similar to Table 2, the measured data are the open circuit voltage (Voc), the short circuit current (Isc), the fill factor (FF), and the output voltage (Pmax). .

  In contrast to the example, in Comparative Example 4, no significant improvement in the open circuit voltage Voc was observed, and in Comparative Example 5, a decrease in the open circuit voltage Voc was observed. This is because the oxygen concentration profile is optimal in the embodiment, but it can be said that the effect of improving the open-circuit voltage Voc does not increase even if more oxygen atoms are contained than the optimal amount. In addition, an element other than oxygen (for example, carbon when carbon dioxide is used) contained in the oxygen-containing gas is simultaneously taken into the i-type amorphous layers 12i and 16i, which causes defect formation, and the open circuit voltage Voc. It may also cause a decrease in

  On the other hand, the curve factor FF was significantly lower in Comparative Example 4 than in the Examples. This acts as a high resistance region when oxygen is excessively contained even in the range from the interface between the semiconductor substrate 10 and the i-type amorphous layers 12i and 16i to 5 nm, and the fill factor FF is lowered. It is thought that.

  Note that in this embodiment mode, oxygen is introduced into both the i-type amorphous layer 12i and the i-type amorphous layer 16i. However, the i-type amorphous layer 12i and the i-type amorphous layer are described. If oxygen is introduced into at least one of 16i, a considerable effect can be obtained.

DESCRIPTION OF SYMBOLS 10 Semiconductor substrate, 12i i-type amorphous layer, 12pp p-type amorphous layer, 14 Transparent conductive layer, 16i i-type amorphous layer, 16nn n-type amorphous layer, 18 Transparent conductive layer Electrode, 100 photovoltaic device.

Claims (10)

A crystalline semiconductor substrate having a first surface and a second surface;
A first amorphous semiconductor layer formed on the first surface of the crystalline semiconductor substrate;
A photoelectric conversion device comprising:
The interface between the crystalline semiconductor substrate and the first amorphous semiconductor layer is an oxide interface containing oxygen of 1 × 10 ²¹ / cm ³ or more,
In the first amorphous semiconductor layer, a high-concentration oxygen region having an oxygen concentration of 1 × 10 ²⁰ / cm ³ or more and 1 × 10 ²¹ / cm ³ or less in a range of 5 nm or less in the film thickness direction from the oxidation interface A photoelectric conversion device comprising: The photoelectric conversion device according to claim 1, wherein the high-concentration oxygen region is in a region of 1 nm or less in the film thickness direction from the oxidation interface.   Of the first amorphous semiconductor layer, the oxygen concentration is 1 × 10 6 on the side farther from the crystalline semiconductor substrate than the high-concentration oxygen region. ¹⁹ / Cm ³ 1 × 10 or more ²⁰ / Cm ³ The photoelectric conversion device according to claim 1, further comprising the following region. The conductivity type of the semiconductor substrate is n-type,
The first amorphous semiconductor layer is an n-type amorphous semiconductor layer;
The photoelectric conversion device according to claim 1 , wherein the n-type amorphous semiconductor layer is located on a light incident surface side. The conductivity type of the semiconductor substrate is n-type,
The first amorphous semiconductor layer is a p-type amorphous semiconductor layer;
The photoelectric conversion device according to claim 1 , wherein the p-type amorphous semiconductor layer is located on a light incident surface side. Wherein the first amorphous semiconductor layer on the collector electrode is formed, the photoelectric conversion device according to any one of claims 1-5. In the first amorphous semiconductor layer, having the oxygen concentration profile in which the concentration in a stepwise manner along the thickness direction from the vicinity of the vicinity of the oxide interface is reduced, according to any one of claims 1 to 6 Photoelectric transformation device. It is a manufacturing method of the photoelectric conversion device according to any one of claims 1 to 7 ,
A first step of forming a concavo-convex structure on the surface of the crystalline semiconductor substrate ;
A second step of oxidizing the surface of the crystalline semiconductor substrate to form an oxidized interface;
A third step of forming the first amorphous semiconductor layer on the oxide surface,
Including
The oxidation treatment is performed using any method selected from a treatment in which the crystalline semiconductor substrate is left in an air atmosphere for a predetermined time, an ozone water treatment, a hydrogen peroxide treatment, an ozonizer treatment, and the like. A method for manufacturing a conversion device. The method for manufacturing a photoelectric conversion device according to claim 8, wherein the first amorphous semiconductor layer is formed by introducing a silicon-containing gas and carbon dioxide gas or oxygen gas.   The method according to claim 9, further comprising a fourth step of forming an n-type or p-type amorphous semiconductor layer by introducing an n-type or p-type dopant into the silicon-containing gas after the third step. Method for manufacturing a photoelectric conversion device.

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